Chemistry and Chemical Engineering.
Vice-chair: Dionne Fortenberry, Mississippi University for Women
8:00 THE EFFECTS OF MONOMERIC FUNCTIONALITY AND COMPOSITION ON PROPERTIES OF THIOL-ENE FILMS
Tolecia Clark (1*), Charles E. Hoyle (1), Sergei Nazarenko (1), Brian Olsen (1), and Luke Kwisnek (2), (1) University of Southern Mississippi, Hattiesburg, MS 39406 and (2) Pennsylvania State University, The Behrend College, Erie, PA 16563
The purpose of this study is to understand the fundamental influence of the thiol and ene monomers on the polymerization kinetics, polymer crosslink formation, and physical properties of films when monomer functionality increases and thiol:ene composition varies. Multifunctional thiols ([f.sub.thiol] = 2, 3, 4, 6, and 9) and multifunctional allyl ethers ([f.sub.ene] = 2 and 3) are copolymerized by irradiation using a medium-pressure UV light source. Highly functional thiols ([f.sub.thiol] = 6 and 9) are synthesized by an amine-catalyzed thiol Michael addition reaction. Polymerization parameters are measured by photo-differential scanning calorimetry and real-time FTIR to obtain polymerization rates and percent conversions. Glass transition temperatures are measured by dynamic thermal mechanical analysis, and film densities are obtained by using an aqueous NaBr solution density test. Preliminary results show that polymerization rates, glass transition temperatures ([T.sub.g]), and film densities increase when the functionalities of thiol and allyl ether monomers increase, although polymerization kinetics and film properties show greater changes when allyl ether functionality increases. Polymerization rates and film properties are optimal when films are composed of equal molar thiol:ene compositions (based upon functionality). Percent conversions are relatively high for copolymerizations of highly functional thiols with each ene having conversion of approximately 100%. High percent conversions indicate that a loose crosslinked network has been formed. This phenomenon can be attributed to localized events known as looping, which delay the gel effect and reduce effective crosslink density.
8:15 NOVEL GAS PHASE METHODS WITH POTENTIAL USE IN PROTEOMICS
Douglas S. Masterson (1,2*), Almary Chacon (2), Huiyong Yin (2), and Ned A. Porter (2), (1) University of Southern Mississippi, Hattiesburg, MS 39406 and (2) Vanderbilt University, Nashville, TN 37235
This project aims to develop novel gas phase proteomics methodologies that rely on the site specific generation of free radicals in a mass spectrometer. Peptides are treated with a peroxycarbonate reagent that selectively modifies lysine residues as peroxycarbamates. The resulting peroxycarbamates are introduced into a Q3 MS instrument where they undergo a CID process. The CID process produces nitrogen centered radicals at the modified lysine sites which then undergo hydrogen abstraction via a Hoffman-Loffler-Freytag reaction (HLF). The HLF reaction produces a carbon centered radical which is situated for [beta]-elimination resulting in the cleavage of the peptide backbone. This reaction sequence is essentially the gas phase equivalent of a trypsin digestion. Under acidic pH conditions, the N-terminal nitrogen can be selectively modified as a peroxycarbamate. When the N-terminal nitrogen is modified and subjected to CID conditions in a MS the resulting MS spectra allow for the rapid determination of the N-terminal amino acid. Mechanistic studies show that this transformation is a free radical process and that it can be used to determine all 20 natural amino acids at the N-terminus. Future mechanistic and applications studies will also be discussed.
8:30 THE STRUCTURE AND NONLINEAR OPTICAL PROPERTIES OF THE HMT-CDA 1:1 ADDUCT: EXPERIMENTAL AND DFT APPROACH
Ramaiyer Venkatraman (1*), Paresh Chandra Ray (1), Frank R Fronczek (2), and Jagdish P. Singh (3), (1) Jackson State University, Jackson, MS 39217; (2) Louisiana State University, Baton Rouge, LA 70803; and (3) Mississippi State University, Starkville, MS 39762.
Equimolar amounts of hexamethylenetetramine (HMT) and trans-1,2-cyclohexanedicarboxylic acid (CDA) formed a self-assembled unit through a hydrogen bonding network. Room temperature single crystal diffraction studies and FTIR spectroscopy of the system indicated adduct formation between HMT and CDA. Crystalline adduct sample exhibited appreciable macroscopic NLO properties. Ab-initio Density Functional Theoretical (DFT) calculations, using the 6-31G(d,p) basis set, have been performed to investigate the gas phase structure and IR frequencies. The dynamic NLO properties were calculated with the ZINDO/CV method including solvent effects. Theoretical parameters (geometry and vibrational frequencies) predicted by DFT method for the adduct are in good agreement with the experimental data.
8:45 GEOMETRY OF THE A[.sup.2][summation], v = 0 [greater than or equal to] [X.sup.2][pi], v' = 0, ELECTRONICALLY EXCITED STATE OF OH RADICAL
Dorothy Wood (1*), S.P. McGlynn (2), and Paresh Chandra Ray (1), (1) Jackson State University, Jackson, MS 39217 and (2) Louisiana State University, Baton Rouge, LA 70803
We present an experimental and quantum-mechanical analysis of the molecular geometry of the excited state of the OH radical emission, A[.sup.2][summation], v = 0 [greater than or equal to] [X.sup.2][pi], v' = 0, 2800-3300 [Angstrom] spectral region. The transition has been obtained using high-resolution plasma emission spectroscopy techniques. Time-dependent density functional theory (TD-DFT) and vibronic intensity distribution methods have been employed to calculate the geometry in the excited state. The latter method is a power series expression for the Franck-Condon (FC) integral in the harmonic approximation in terms of a parameter that approaches zero as the vibrational frequencies of the two combining electronic states approach equality (2). From this FC expression, we seek to verify the use of its truncated form to test the correspondence of bond lengths to the results obtained by TD-DFT and other techniques. Theoretical results will be compared with the experimental values wherever available (we currently have two spectra from our laboratory.) The results are evaluated in detail about the agreements and disagreements between theoretical and experimental findings. 1. Mills, R.; Ray, P.C.; Mayo, R.M., CW, H1 Laser Based on Stationery Inverted Lyman Population from Incandescently Heated Hydrogen Gas with Certain Group I Catalysis, IEEE Trans. of Plasma Science, (2003), 31, 236-247.2. Wood, D. M.; Hochmann, P.; Klasinc, L.; McGlynn, S.P., Vibronic Intensities in Diatomic Molecules, International Journal Of Quantum Chemistry (2004), 99(4), 522-532.
9:00 THE INVESTIGATION OF FRONTAL POLYMERIZATION IN THIOL-ENE SYSTEMS
Alford Perryman, Jr.*, Birsen Virsali, and John A. Pojman, University of Southern Mississippi, Hattiesburg, MS 39406
Thiol-ene polymerization proceeds through a sequential radical propagation/chain transfer mechanism that leads to polymer and network formation much like a step-growth polymerization. Thiol-enes are advantageous over traditional acrylate systems in that they exhibit low oxygen inhibition during cure and have the ability to form thin and thick cures. The frontal polymerization of the thiol-ene allows conversion of the monomers into polymer via a localized reaction that propagates through a reaction zone. The overall purpose of this research project was to develop a new frontal polymerization system for potential use in in situ repair on the earth, in space, on the moon, and on Mars. In this study, the velocity and front temperature was determined as a function of the initiator concentration and thiol-ene ratio. This information is essential for determining the optimal chemical composition for actual applications and for developing an understanding of how frontal polymerization of thiol-enes differ from other frontal polymerization systems previously studied.
9:15 SHAPE VS. SIZE IN SIZE EXCLUSION CHROMATOGRAPHY
Gregg Anazia* and Susan Pedigo, University of Mississippi, University, MS 38677
Cadherin is a cell adhesion protein that is significant in tissue formation. Crystallographic studies indicate that the extracellular domains of cadherin are prolate ellipsoid in shape. The molecular weight of two cadherin constructs as determined experimentally using size exclusion chromatography (SEC) was approximately twice that of the computed value. This is misleading given the tendency for cadherin to dimerize in vivo. Alternatively, the SEC column was calibrated according to the Stokes radius of the standard proteins. Using this revised standard curve, cadherin constructs appeared to have Stokes radii very similar to that determined computationally for these constructs using the program HYDROPRO. Thus, calibration of SEC columns according to the Stokes radius yields more reliable determination of the size of proteins.
9:30 QUANTIFICATION OF ALL TRANS RETINOIC ACID (ATRA) BY HPLC, SUBJECTED TO LIGHT AND HEAT TREATMENTS
Mudlagiri Goli (1*), Shanise Brown (1), and Doug Paulsen (2), (1) Mississippi Valley State University, Itta Bena, MS 38941 and (2) Morehouse School of Medicine, Atlanta, GA 30310
All-trans Retinoic Acid is a derivative of vitamin A. It is the stable form and is used in the treatment of cancer and skin wrinkles. ATRA and its isomer are highly toxic to pregnant women or nursing mothers. They are known to cause birth defects. 13-cis retinoic acid, an isomer of ATRA used to treat acne, is known to be more toxic than ATRA. It is well known that ATRA and its isomers are light sensitive. Our purpose was to study the behavior of ATRA samples subjected to heat and light. ATRA was exposed to normal visible light and incubation (heat) for various periods of time (0-92 hours). The exposed samples were analyzed with an Agilent series 1100 HPLC using a diode array detector. ATRA samples subjected to light slowly isomerized to 13-cis retinoic acid. The extent of isomerization reached a maximum after 20 hr. ATRA degradation reached a maximum by 92 hours. Formation of other detectable isomers was negligible. The ATRA samples subjected to heat (37.5[degrees]C) were remarkably stable for a long period (20 hours). No other isomers of ATRA were found in the heat-treated samples. The quantification of ATRA and isomer formation and destruction of the sample, if any, was well studied using the HPLC method.
9:45 ACCESSING LEAD IN DRINKING WATER FROM SOURCES IN THE DELTA
Deere Curtisine* and William C. Mahone, Mississippi Valley State University, Itta Bena, MS 38941
It has been noted and well-documented that lead presents one of the most serious environmental health risks to young children, fetuses, and pregnant women. Lead has been identified as a pollutant in several different aspects of the environment. This investigation accesses the lead content in drinking water sources in the delta. The approach was to develop test methods and quality control procedures for determining levels of lead in drinking water. The method used to test the samples of drinking water for lead was based on the Flame A.A. instrumentation techniques. We developed sample preparation procedures that allowed us to maximize our detection limits using pre-concentration techniques. In these findings, there was lead indicated in several drinking waters near and just above the action level (15 ppb). Preliminary data indicated Belzoni, Mississippi had a 10 ppb of lead, Isola, Mississippi had 25 ppb of lead, Louise, Mississippi had 25 ppb of lead, Silver City, Mississippi had 9 ppb of lead, and Midnight, Mississippi had 10 ppb of lead. The correlation coefficient was 0.999 for the instrument response curve. The sample responses was located within the lower limits of the least squares data range. This data suggest that a more thorough study with better instrumentation and more quality control procedures are required to definitively assess the exposure potential.
10:00 SYNTHESIS AND MESOMORPHIC BEHAVIOUR OF A HOMOLOGOUS SERIES OF N(4-N-ALKOXYSALICYLIDENE)-4'-N-ALKOXYANILINES AND THEIR COPPER(II) COMPLEXES
Francis Tuluri (1*), Nandiraju V.S. Rao (2), Manoj Kr. Paul (2), Romeo Singh (2), and V. Padmini (2), (1) Jackson State University, Jackson, MS 39217 and (2) Assam University, Silchar--788 011, Assam, India
A series of metal (Cu) complexes with bidentate Schiff-bases viz. N-(4-n-alkyloxy salicylidene) 4'-n-alkoxyanilines obtained by the 1:1 condensation of 4-n-alkyloxy salicylaldehyde and 4-n-alkoxyanilines viz., 4-n-hexyloxyaniline, 4-n-octyloxyaniline, 4-n-decyloxyaniline 4-n-dodecyloxyaniline, 4-n-tetradecyloxyaniline and 4-n-hexadecyloxyaniline and have been prepared and characterized. The synthesis of the ligands N-(4-n-hexyloxysalicylidene)-4'-n-alkyloxyanilines as well as the complexes and characterization by thermal microscopy for mesomorphism are presented. The ligands are found to exhibit interesting smectic phases (mostly tilted phases) in addition to nematic phases and polymorphism, while the complexes showed orthogonal smectic A, smectic B, and smectic E phases. The mesomorphic range as well as the polymorphism decreases with increase in chain length. However the coordination with Copper (II) leads to thermally stable metallo-mesogens possessing larger mesomorphic range and a reduced number of mesomorphic phases.
10:30 A COMPARISON OF SOLVENT EFFECTS ON THE REGIOSELECTIVITY OF SINGLET OXYGEN ENE REACTIONS OF 2-METHYL-3-PHENYLTHIO-2-BUTENE AND 2-METHYL-3-PHENYLSULFONYL-2-BUTENE
Natacha Touchette* and Kristina Stensaas, Millsaps College, Jackson, MS 39210
2-Methyl-3-phenylthio-2-butene (1) and 2-Methyl-3-phenylsulfonyl-2-butene (2) were photooxidized in deuterated benzene, deuterated methanol, and deuterated methanol/water mixtures. Proton nuclear magnetic resonance spectroscopy was used to monitor product distributions. The photooxidation of sulfide 1 resulted in competitive formation of ene product and sulfoxide product, depending on the choice of solvent. Only ene product was formed during the photooxidation of sulfone 2. The observed regiochemistries are a result of several factors including hydrogen bonding of the solvent with the proposed perepoxide intermediates, the cis effect, the geminal effect, and formation of the thermodynamically favored conjugated product.
10:45 SOLUTION PROPERTIES OF SINGLE-WALLED CARBON NANOTUBES
Mark Hamon*, Gina A. Sorci, Miles A. Sugar, James P. McVaugh, and Daniel T. Walker, Millsaps College, Jackson, MS 39210
Single-walled carbon nanotubes (SWNTs) are unique molecules which possess outstanding physical properties. Chemical modification of the SWNTs has succeeded in producing soluble material in various organic solvents, thus allowing for a higher degree of process ability and study. Despite these advances, a complete understanding of the solvation of SWNTs has not been realized. By studying the soluble SWNTs in solution with static light scattering techniques we have achieved a greater understanding of how SWNTs interact with one another as well as their affinity for the solvent.
11:00 PREPARATION OF INITIATOR-CORE MICROCAPSULES AND THEIR USE IN FRONTAL POLYMERIZATION
Brian McFarland*, Sammy Popwell, and John A. Pojman, University of Southern Mississippi, Hattiesburg, MS 39406
Frontal polymerization is a mode of converting monomer into polymer via a localized exothermic reaction zone that propagates. Frontal polymerization systems often consist of a monomer in which a thermal free-radical initiator has been dissolved. These systems are sometimes not practical for real-world applications however, because the systems often suffer from a short pot life, reacting homogeneously before they can be used for their desired application. A possible remedy to this problem is examined by attempting to microencapsulate free-radical initiators and then use those microcapsules in frontal polymerization systems, keeping the monomer and initiator separate until the desired time. Several different methods of microencapsulation are tested, the most successful proving to be an interfacial polymerization of polyurea shells around an initiator droplet, consisting of either a hydroperoxide or a peroxyketal. The capsules are tested for core loading, dry powder stability, temperature stability and monomer storage stability. The capsules have an initial core loading of 75-80%, which remains stable upon dry storage. The capsules release their core at approximately 85 [degrees]C, ensuring that they will release in a frontal system, which can achieve temperatures of over 200 [degrees]C at the front. Frontal systems prove to run successfully when microencapsulated initiator is used in lieu of a dissolved initiator. There proves to be a substantial improvement in the pot life of frontal systems when the initiator is microencapsulated, both in elevated temperature environments and in systems in which a redox accelerator is added. The effect of shell crosslinking is currently being studied.
11:15 BIOSENSOR BASED ON GOLD NANOPARTICLES INDUCED BY NON-CROSSLINKING DNA HYBRIDIZATION: A SPECTROSCOPIC INVESTIGATION WITH THEORETICAL IMPLEMENTATION
Paresh Chandra Ray* and Hongtao Yu, Jackson State University, Jackson 39217
Taking advantage of recent developments in the field of metallic nanoparticle-based biosensor, we have investigated aggregation phenomena of DNA-functionalized gold nanoparticles prepared by linking sulfur functionalized oligomer DNA with gold nanoparticles through S-S linkage. A solution of 500 nM of HS-(CH2)6-5'-TAC GCC ACC AGC-3' was incubated with 1 nM of gold nanoparticle. At various NaCl concentrations, the aggregation behavior of the gold nanoparticle was observed by observing the solution colors and by monitoring the visible spectra. Modified gold nanoparticles aggregated when they were hybridized with target DNA. The solution become colorless when a complimentary DNA strand was added with the target DNA tethered to gold nanoparticles. Solution color remains the same when a complimentary DNA strand with a single base mismatch was added. This method can detect target DNA at a concentration of nanomolar and discriminate a single base pair mismatched DNA strand. To understand the role of metal-DNA interactions, we also studied the absorption ex-situ using Fourier Transform Infrared (FTIR) and Surface-Enhanced Raman Spectroscopic (SERS) techniques. A simple model describing the optical properties of a DNA-gold nanoparticle aggregate is established and the theoretical data are compared with experimental findings.
11:30 ELECTROGENERATED CHEMILUMINESCENCE AND ITS BIO-RELATED APPLICATIONS
Wujian Miao, University of Southern Mississippi, Hattiesburg, MS 39406
Electrogenerated Chemiluminescence (ECL) has been investigated since 1964 as a method of producing light at an electrode. In a sense, ECL represents a marriage between electrochemical and spectroscopic methods. ECL has some advantages over fluorescence methods, because it does not involve a light source and hence the attendant problem of scattered light and luminescent impurities. Moreover, the specificity of the ECL reaction decreases problems with side reactions and is characterized by good spatial and temporal resolution. The general principle of DNA probe assays and immunoassays based on ECL technique using ECL labels can be described as follows. Single stranded (ss) DNA or an antibody is first immobilized on the surface of the substrate (electrode), then the complementary ssDNA tagged with the ECL label (e.g., tris(2,2'-bipyridyl)ruthenium(II) or Ru(bpy)[.sub.3.sup.2+] hybridizes with the confined ssDNA, or the antigen combines with the immobilizedantibody before it further couples with the antibody that is tagged with the ECL label. When a potential is applied to the electrode in contact with a coreactant solution or scanned over a certain potential range, an ECL signal is generated and detected with a photomultiplier or CCD camera. The most widely used ECL label and coreactant are Ru(bpy)[.sub.3.sup.2+] and tri-n-propylamine (TPrA), respectively, since the combination of these two gives the highest ECL efficiency in all coreactant ECL systems. A brief review of the principles of ECL will be followed by a discussion of its applications to a variety of analyses (e.g., immunoassay, DNA probes).
11:45 Divisional Business Meeting
1:30 SYNTHESIS OF AMINOBENZO-CROWN COMPLEXES AND CARBOXYLIC ACID COMPOUNDS TO FORM HYDROGEN-BONDED CLAY MIMICS
Stefanie Cummings* and Alicia M. Beatty, Mississippi University for Women, Columbus, MS 39701 and Mississippi State University, Mississippi State, MS 39762
Hydrogen-bonded clay mimics, layered organic solids, have a wide variety of chemical applications, but predictably crystallizing these frameworks is difficult. The reaction of certain organic acids (for example, 3,5 pyrazoledicarboxylic acid) with amines, such as benzylamines and alkylamines, has led to hydrogen-bonded pillared clay mimics, and by varying the organic acid and amine used, a variety of predictable layered structures can be synthesized. The organic acid forms the layers of clay mimics, and the pillars are made from amines. Varying the amine compound used may allow us to generate clay mimics with a wide variety of practical applications. To that end, we wish to incorporate crown ether substituents between layers. The use of aminobenzo-crown ethers as pillars may allow for host-guest chemistry to occur. The synthesis of aminobenzo-18-crown-6 and aminobenzo-15-crown-5 will allow for the study of these compounds as possible pillars in clay mimics, and allow for the testing of their ability to trap ions and molecules between layers. New multicarboxylic acids for layer makers are also possible, so the synthesis of 1,10-phenanthroline-4,7-dicarboxylic acid and biphenyl-3,3',5,5'-tetracarboxylic acid will allow for the study of these compound as possible components in clay mimics. Through the synthesis of these four compounds more research can be conducted on the synthesis of clay mimics, their reactivity, and applications.
1:45 THE USE OF LASER LINE DEFLECTION (WEINER'S METHOD) TO DETERMINE THE DIFFUSION COEFFICIENTS OF METHYL METHACRYLATE AND POLY (METHYL METHACRYLATE)
Josh Hanna* and Lydia L. Lewis, Millsaps College, Jackson, MS 39210
Isothermal Frontal Polymerization (IFP) is a self-sustaining, directional polymerization that occurs when a solution of monomer and thermal initiator come in contact with a polymer seed and create a viscous region where a higher polymerization rate, the gel effect, occurs. IFP can be used to produce gradient refractive index materials (GRINs) for use in the fiber-optic industry, and mathematical models of IFP have been constructed in hopes of improving GRIN fabrication. One drawback to these models is the lack of information in the literature on the two diffusion processes that occur in IFP: liquid monomer diffusing into the polymer seed and the polymer seed diffusing into the liquid monomer. We use laser line deflection (or Weiner's method) to measure the diffusion coefficients of monomer into polymer of the methyl methacrylate/poly(methyl methacrylate) system over the temperature range of 40 to 60 [degrees]C and present the analysis technique for these coefficients.
2:00 THE SYNTHESIS OF A POLYMERIC INHIBITOR AND ITS USE WITH ISOTHERMAL POLYMER FRONTS
Evan Underwood* and Lydia L. Lewis, Millsaps College, Jackson, MS 39210
Isothermal frontal polymerization (IFP) is a directional polymerization that occurs where a solution of monomer and thermal initiator contacts a polymer seed creating a viscous region. This region exhibits a higher polymerization rate due to the Trommsdorff, or gel, effect. Monomer solution continues to diffuse into the forming polymer matrix, and the reaction proceeds directionally until the homogeneous polymerization of the monomer above the front halts the movement of the polymerizing front. To prolong the homogeneous polymerization of the monomer solution, a polymeric inhibitor (of sufficient size to prevent diffusion into the forming polymer matrix) was synthesized using 4-amino-2,2'-6,6'-tetramethyl-1-piperidinyloxy. The polymeric inhibitor has been characterized through IR spectroscopy, and quantification of substitution was determined by electron pair resonance. Isothermal fronts were run with and without this polymeric inhibitor confirming that the polymeric inhibitor has been successful in prolonging the lifetimes and distances of isothermal fronts.
2:15 ANALYZING ISOTHERMAL FRONTAL POLYMERIZATION IN THIN LAYERS BY LASER LINE DEFLECTION
Chip Fillingane* and John A. Pojman, University of Southern Mississippi, Hattiesburg, MS 39406
The purpose of this study is to investigate the ability to use laser line deflection to observe the progression of isothermal frontal polymerization within a thin layer. Laser line deflection takes advantage of density gradients occurring in fronts, which cause a deviance in the beam emitted from the laser. Typically, laser line deflection has been used to examine samples with a width of 1 cm. Samples in this study are constrained to a width of 1 mm. The monomer polymer systems examined in this study include methylmethacrylate, dodecyl acrylate, and 1,6 hexanediol diacrylate.
2:30 METATHESIS IN AQUEOUS MEDIA: SYNTHETIC STRATEGIES TO NEW CATALYSTS
Hans J. Schanz, University of Southern Mississippi, Hattiesburg, MS 39406
Conducting organic transformations in water displays many benefits over classical synthesis in organic solvents. Water is non-toxic, environmentally benign and vastly abundant. Apart from the economic and ecological advantages, aqueous media as solvents are also attractive due to their high heat capacities and their low miscibility with organic solvents which forms the basis of methodologies for catalyst recycling. Over the past four decades metathesis has evolved to become a highly valuable and versatile tool in organic and polymer synthesis. In particular during the last ten years, Ru-based Grubbs-type metathesis catalysts have significantly expanded the application spectrum due to their substrate tolerance and inertness towards air and moisture. Several water-soluble catalysts have been synthesized and successfully employed in aqueous ROMP and ROM reactions. These catalysts are coordinated by water-soluble phosphine ligands providing less active and thermally less stable "first generation" Grubbs-type catalysts. In our research, we target the synthesis of water-soluble N-heterocyclic carbene (NHC) ligands for the application in aqueous metathesis reactions. Substitution of one phosphine versus one NHC-ligand provides "second generation" Grubbs-type catalysts which should display significantly improved catalytic performances. We are currently developing various synthetic procedures which could provide NHC ligand derivatives for the application in aqueous metathesis.
4:00 Divisional Poster Session
EXPERIMENTAL AND COMPUTATIONAL STUDIES OF PERFLUOROCYCLOALKANES c-[C.sub.N][F.sub.2n], N=3-5) AND THEIR STABLE NEGATIVE ANIONS
Adel Elsohly (1*), Gregory S. Tschumper (1), Richard A. Crocombe (2), Jih Tzong Wang (2), and Francon Williams (2), (1) University of Mississippi, University, MS 38677 and (2) University of Tennessee, Knoxville, TN 37996
Perfluorocycloalkanes (c-[C.sub.n][F.sub.2n], n = 3-5) are common compounds used in the manufacture of integrated circuits. Thus, the electronic ground states of their anions are of practical importance. In order to definitively determine the electronic states of the anionic species of these cyclic structures, quantum chemical calculations (B3LYP and MP2) were performed in conjunction with experimental ESR spectroscopy. It was determined that the perfluorocyclopropane anion adopts a [D.sub.3h] geometry and a [.sup.2][A.sub.2]" ground electronic state. The perfluorocyclobutane adopts a [D.sub.4h] geometry and a [.sup.2][A.sub.2u] ground electronic state. Finally, the perfluorocyclopentane anion adopts a [C.sub.s] structure and a [.sup.2]A' electronic state. The highest level calculations were found to be within 1% of the a([.sup.19]F) experimentally determined values.
COMPUTING THE INTRINSIC CONFORMATIONAL PREFERENCES OF SUBSTITUTED CYCLOHEXANES AND TETRAHYDROPYRANS: SOME SURPRISES AND NEW INSIGHTS
Abby Weldon* and Gregory S. Tschumper, University of Mississippi, University, MS 38677
Cyclohexane and tetrahydropyran rings containing simple, electronegative substituents such as C[H.sub.3], F, OH, OC[H.sub.3] provide a paradigm for the anomeric effect. A series of ab initio and density functional (DFT) theory computations have been carried out with basis sets ranging in size from from the modest 6-31G(d) split valence basis to the massive cc-pV5Z correlation consistent basis in order to determine the conformational preference (axial versus equatorial) of these substituted 6-membered rings. In most cases, qualitative agreement exists between each of the theoretical methods and experiment. However, substantial discrepancies are observed for cyclohexanes with simple electronegative substituents such as OH and OC[H.sub.3]. For example, MP2 calculations with split valence basis sets as large as 6-311G(2df,2pd) suggest that axial methoxycyclohexane is electronically more stable than the equatorial conformer by nearly 0.6 kcal/mol. On the other hand, RHF and B3LYP computations with the same basis sets indicate that the equatorial orientation is favored by 0.2-0.4 kcal/mol. The relative energies of these cyclohexane conformers computed with high-level ab initio methods such as MP2 and CCSD(T) are surprisingly sensitive to the quality of the atomic orbital basis set. Only by progressing to extremely large basis sets does a consistent trend begin to emerge. In addition, corrections for the zero-point vibrational energy and entropy are substantial and can even reverse the electronic conformational preferences of these species.
NMR OF A HIGH SALT PROTEIN
John Young* and Bulent Binbuga, Mississippi State University, Mississippi State, MS 39762
Dihydrofolate reductase (DHFR) catalyzes the reduction of dihydrofolate to tetrahyrofolate using coenzyme nicotinamide adenine dinucleotide phosphate (NAPD) as a proton donor. Haloferax volcanii DHFR (hvDHFR) is an Achaean group microorganism that flourishes in a salty environment (3.5M) which is necessary for both stability and activity. We have produced and purified the hvDHFR ([.sup.2]H, [.sup.13]C, [.sup.15]N labeled) to probe its structural characteristics by NMR. The result of this study will be used to investigate the protein's flexibility, through NMR dynamics, at varying salt concentrations. As salt concentrations are lowered the protein shows a reduction in activity without lose in structure or binding affinity. We have hypothesized that this reduction in activity may be due to reduced flexibility. Here we present the sequential backbone assignments of hvDHFR accomplished through triple-resonance NMR experiments.
SECOND VIRIAL COEFFICIENT CORRELATED WITH THE HAMPTON CRYSTALLIZATION SCREEN
Jessica Reily* and William Wilson, Mississippi State University, Mississippi State, MS 39762
The Hampton Crystallization Screen Lite (HCSL) is a complete kit of 50 reagents designed to provide a rapid screening method for the crystallization of biological macromolecules such as proteins, peptides, and nucleic acids. The primary screen variables are salts, pH, and crystallizing agents. The second virial coefficient (B) is a dilute solution thermodynamic parameter that has been shown to be an accurate predictor of crystallization conditions for proteins. Favorable crystallization conditions correspond to B values in the range of -1 to -8 mol/mL/[g.sup.2], called the crystallization slot. We have used laser light scattering to measure B for the protein lysozyme in the HCSL and found that 26 of the 50 conditions fell within the slot. Five conditions were chosen to perform crystallization trials: one with very positive B, one with slightly positive B, one with B near zero, one with slightly negative B, and one with very negative B. The hanging drop method was used to determine if crystals would form under these five conditions. Results of the crystallization trials were found to correlate with and be accurately predicted by the measured B values.
THE EFFECT OF NATURAL SUNLIGHT ON CIPROFLOXACIN EYE DROP
Jiben Roy (1*), Diaa M. Shakleya (2), Patrick S. Callery (2), Dilip K. Sarker (3), Anwar H. Miah (3), and Subodh C. Das (3), (1) Mississippi University for Women, Columbus, MS 39701; (2) West Virginia University, Morgantown, WV 26506; and (3) Square Pharmaceuticals Ltd, Pabna, Bangladesh
Ciprofloxacin 0.3% preparation is available on the market for topical ophthalmic use. The marketed eye drop samples, as well as reference ciprofloxacin in water solution was found to degrade to an ethylenediamine analog of ciprofloxacin when exposed to natural sunlight. The degradation product was identified by comparison to a reference standard as well as by LC--MS, MS/MS and MS & MS/MS after deuterium exchange. A model compound, phenylpiperazine also was found to decompose in a similar fashion but after a long duration of sunlight exposure compared to ciprofloxacin. When tested against Bacillus pumillus, the sunlight induced eye drop showed slightly less antimicrobial activity compared to original eye drop. However, ciprofloxacin eye drop containers were stored in cartons, there was no photolytic degradation.
HPLC METHOD FOR QUANTIFICATION OF 13-cis RETINOIC ACID (13-cis RA) SUBJECTED TO LIGHT AND HEAT TREATMENTS
Mudlagiri Goli (1), Ramona Burris (1), and Doug Paulsen (2), (1) Mississippi Valley State University, Itta Bena, MS 38941 and (2) Morehouse School of Medicine, Atlanta, GA 30310
13-cis RA is a derivative of vitamin A. It is one of the forms used to treat cancer and skin wrinkles. 13-cis RA and all-trans retinoic acid (ATRA) isomers are highly toxic to pregnant women or nursing mothers. They are known to cause birth defects. 13-cis RA is an isomer of ATRA and is more toxic than ATRA. Vitamin A derivatives are known to be light sensitive. Our purpose was to study the behavior of this compound when subjected to heat and light. 13-cis RA was exposed to normal visible light and incubation (heat) for various periods of time (0-92 hours). The exposed samples were analyzed by using Agilent series 1100 HPLC equipped with a diode array detector. 13-cis RA samples subjected to light slowly isomerized to ATRA. The extent of isomerization reached a maximum by approximately 20 hr. Degradation reached a maximum around 92 hours. Formation of other isomers was negligible. The 13-cis RA samples subjected to heat (37.5 [degrees]C) were remarkably stable for a long period (20 hours). No other isomers of 13-cis RA were found in the heat-treated samples. The quantification of 13-cis RA and ATRA formation and destruction of the sample, if any, were well studied using the HPLC method.
NOVEL MULTIDENTATE NHC LIGANDS FOR THE USE IN ASYMMETRIC METATHESIS
Erika Shaffer* and Hans J. Schanz, Loyola University New Orleans, New Orleans, LA 70118 and University of Southern Mississippi, Hattiesburg, MS 39406
Over the last three years, several chiral ruthenium-based metathesis catalysts have been synthesized. These bear chiral NHC ligands and have been employed successfully in catalyzing ARCM (Asymmetric Ring Closing Metathesis) and AROM (Asymmetric Ring Opening Metathesis) reactions providing enantioselection beyond 90% ee for various substrates. Particularly interesting are catalyst with back-bonding hydroxy moieties which promote metathesis in air and nondried solvents. In our research, we target the design of an array of novel, chiral NHC ligands with back-bonding hydroxy moieties in generally applicable synthetic sequences of few steps. Ru-based metathesis catalysts of the new ligands are expected to display high enantioselection in ARCM and AROM reactions, as well as being fairly inert towards molecular oxygen and moisture. Due to the straightforward synthesis, we now can explore the possibility of ligand tuning adjusting steric and electronic parameters to obtain maximum catalytic performance. Starting from enantiomerically resolved trans-1,2-cyclohexanediamine, we initially targeted tridentate, C2-symmetric NHC-ligand precursors with two back-bonding hydroxy groups which are available via reductive amination and subsequent ring closing reaction with triethyl-orthoformate. The synthesis of dissymmetric, bidentate ligand precursors was attempted in a sequential derivatization of the diamine. The optimization of the second step of the reaction sequence, a Pd-mediated arylation reaction or reductive amination remains under current investigation. Both precursors can be readily used for catalyst preparation in a one-pot ligand exchange reaction with first generation Grubbs' catalyst derivatives.
SURFACE MODIFICATION BEHAVIOR OF AMPHIPATHIC FUNGAL PROTEINS ISOLATED FROM EDIBLE FUNGAL SOURCES
Cynthia McWright (1*), Clara Short (2), Ashley Grant (3), Sonya D. Benson (3), and Sarah E. Morgan (3), (1) Hancock High School, Hancock, MS 49930; (2) Hattiesburg High School, Hattiesburg, MS 39401; and (3) University of Southern Mississippi, Hattiesburg, MS 39406
Amphipathic fungal proteins called hydrophobins were isolated from three edible fungal sources: ABH1 from Agaricus bisporus, LEH1 from Lentinans edodes, and POH1 from Pleurotus ostreatus. Contact angle analysis was used to evaluate the surface modification behavior of hydrophobins ABH1, LEH1, and POH1 applied to surfaces of varying hydrophobicity. The surface modification behavior of each hydrophobin protein was monitored as a function of protein concentration and deposition method. Protein solutions ranging in concentration from 5 to 50 ig/mL were prepared and applied to substrates using two deposition methods. The deposition methods evaluated included drop deposition and adsorption methods. The drop deposition method applied a fixed volume of hydrophobin solution directly onto substrates. The adsorption method maintained a substrate in a fixed volume of hydrophobin solution for controlled periods of time. The ability of each hydrophobin to modify surfaces was affected by substrate hydrophobicity, protein concentration, and deposition method. Acknowledgements: Major support for these studies from NSF IUCRC and NSF MRSEC is gratefully acknowledged.
EXPLORING IMPACT OF SURFACTANT INTERACTIONS ON SURVIVAL OF BACTERIAL SPECIES USING FLUORESCENT NUCLEIC ACID STAINING SYSTEM
Ayesha R. Alam*, Alicyn M. Rhoades, Mohamed O. Elasri, and Douglas A. Wicks, University of Southern Mississippi, Hattiesburg, MS 39406
Spoilage of latex emulsions and harmful components of common in-can preservatives used to deter such spoilage are a serious threat. Because of their unique kill method, peptide-based antimicrobials are expected to be less susceptible to antimicrobial resistance, serving as favorable biocides and preserving latex stability. Thorough understanding of microbes and emulsion components are of primary concern toward these developments. Fluorescence is a powerful tool currently employed in concurrent detection, identification and enumeration of microbes in emulsion systems, providing a means for rapid evaluation of spoilage activity. As part of essential groundwork, this study focuses on impact of surfactant interactions on survival of model bacteria Pseudomonas aeruginosa and Escherichia coli using a fluorescent nucleic acid staining system. Stain compatibility with surfactant solutions, and detection of bacterial growth and survival was confirmed. Explored systems include different formulations and concentrations of hydroxyethyl cellulose, ionic and nonionic surfactants, including ethoxylated nonylphenols (nonionic, phosphated and sulfonated forms), ammonium acetate and modified bacterial nutrient medium. Over a series of experiments, specific ratios of live and dead bacteria, prepared by suspension in phosphate buffered saline and ethanol respectively, were used to inoculate the aforementioned combinations of surfactants/emulsion components. Absorbance and fluorescence peaks were measured, and trends observed.
NANOTRIBIOLOGICAL STUDIES OF POLYMER SURFACES VIA ATOMIC FORCE MICROSCOPY
Rahul Misra*, Paul J. Jones, and Sarah E. Morgan, University of Southern Mississippi, Hattiesburg, MS 39406
Smooth surfaces of rigid rod polymers were generated by spin coating and drawdown techniques to study changes in surface topography after coating with the fungal protein Sc3 hydrophobin. The Sc3 hydrophobin was placed on the polymer surface by both dip coating and spin casting. Friction studies were performed on a polystyrene film to determine the frictional coefficient directly from atomic force microscopy. Studies of interactions of biological molecules with polymer surfaces are of interest for potential use in biomedical and personal care applications, i.e., improvement in lubricity, hydrophilicity, and/or biocompatibility. Acknowledgment is made to the donors of the American Chemical Society Petroleum Research Fund for partial support of this research.
HYDROPHILIC CAMPTOTHECIN ANTI-CANCER DRUGS
Randy Wadkins (1*), David Bearss (2), Govindarajan Manikumar (3), Mansukhlal C. Wani (3), Monroe E. Wall (3), and Daniel D. Von Hoff (2), (1) University of Mississippi, University, MS 38677; (2) University of Arizona Cancer Center, Tucson, AZ 85724; and (3) Research Triangle Institute, Research Triangle Park, NC 27709
Camptothecin analogs that form more stable ternary complexes with DNA and topoisomerase I (termed cleavable complexes) show greater activity in their ability to inhibit tumor cell line growth in pre-clinical studies. Based on our earlier work, we hypothesized that analogs bearing hydrogen bonding moieties at the 7-through 10-position of camptothecin would result in more stable cleavable complexes. Consequently, we synthesized analogs with 7-mono-, 7-di-, and 7-trihydroxymethylaminomethyl groups. These analogs showed increasing cleavable complex stability as the number of hydroxyl groups was increased. The 7-trihydroxymethylaminomethyl analog of 10,11-methylenedioxycamptothecin (THMAM-MD) showed remarkable ternary complex stability with a half-life of 116 minutes. This is an order of magnitude more stable than any previously-examined analog. Our in vitro analysis demonstrated that these analogs were all potent topoisomerase I poisons, and could inhibit tumor cell growth in culture. We studied the effects of THMAM-MD in vivo in SCID mice bearing HT-29 colon cancer and MiaPaCa-2 pancreatic cancer tumors. The THMAM-MD analog showed excellent, persisting activity in inhibiting tumor growth with both lines. Taken together, our results suggest that camptothecins with hydrophilic, hydrogen bonding groups at the 7-position hold the promise of excellent clinical activity.
THE INVESTIGATION OF MORPHOLOGY DEVELOPMENT IN H-PDLC FILMS
Askim F. Senyurt*, Garfield Warren, Charles E. Hoyle, and Joe B. Whitehead, Jr., University of Southern Mississippi, Hattiesburg, MS 39406
Due to numerous important functional properties, liquid crystal (LC) polymer blends have been studied for a wide variety of applications, the most popular being displays and shutters. The electro-optical properties of LC polymer composites depend on both the LC phase and the polymer phase. The size and the shape of the LC domains determine the properties and suitability for system applications. Holographic Polymer Dispersed Liquid Crystal (H-PDLC) films with different thiolene functional monomers were made and investigated to understand the relationship between morphology and electro-optic properties. Thiol-ene systems based upon enes that vary in hardness were chosen for photopolymerization to produce polymer matrices for preparation of optical devices. The matrices formed were found to have several inherent advantages including: high monomer conversion, low shrinkage, resistance to oxygen inhibition during polymerization, and phase separation properties of small molecule LCs with homogenous droplet sizes.
CHARACTERIZATION OF 5-SULFOSALICYLIC ACID USING ANALYTICAL INSTRUMENTATION
Denaya Butler* and Murrell Godfrey, University of Mississippi, University, MS 38677
The purpose of this experiment was to use analytical instrumentation and methods to characterize a given drug. The results from these characterizations can later be used as standards in different drug testing methods and/or to provide a basis for future research studies. In characterizing and analyzing different compounds and drugs, there are different forms of analytical methods and instrumentation that could be used. Several different types of analytical processes and instrumentation were used to determine the analytical and organic properties of the given drug in aqueous solution. Ultraviolet visible spectrophotometry was used to determine the wavelength maximum, concentration, and molar absorptivity of the compound. In order to determine the purity of the given compound, gas chromatography was performed. After determining these properties, nuclear magnetic resonance spectrometry was used to reveal the structure of the drug. The compound to be characterized in this research experiment was sulfosalicylic acid. This compound has three other names by which it is known. These names are 2-hydroxy-5-sulfobenzoic acid, 5-sulfosalicylate, and 5-sulfosalicylic acid. Its molecular formula is [C.sub.7][H.sub.6][O.sub.6]S[H.sub.2]O with a formula weight of 254.22 grams. Sulfosalicylic acid is an aromatic sulfur-oxygen compound. It is a white, odorless powder that is very soluble in water and has a melting point of 120 [degrees]C. Sulfosalicylic acid is a protein precipitant that is commonly used in blood and urine analysis. It is most frequently used in a process known as the sulfosalicylic acid method or proteinuria. This method breaks down the components of a substance to determine its protein concentration. This particular test and others like it are used in forensic examinations during criminal investigations. The results from these characterizations could be used later as standards in different drug testing methods or to provide a basis for further research studies. Such future studies could include examining the effects of added substituents to sulfosalicyic acid.
EXCIPIENT SELECTIONS FOR PEPTIDE STABILITY STUDIES
Levenia Baker (1*), Yunsong Li (2), and Elizabeth Topp (2), (1) Alcorn State University, Alcorn State, MS 39096 and (2) University of Kansas, Lawrence, KS 66045
Purpose: The objective of this current study is to select appropriate excipients for the peptide stability studies in amorphous solid. Methods and Results: Eleven excipients were tested in this study by examining the solubility, color, cake shape and ability for reconstitution in the designed experimental condition. Each excipient was made to 5% (w/v) in CAPS buffer. Samples were then lyophilized. The lyophilized samples were then stored in the stability chamber at 50 [degrees]C with relative humidity of 30%, 75%, or 95%. The physical properties were evaluated for a period of two weeks, and polyethylene glycol, polyethylene oxide, sucrose, dextran 500, hypromellose, hydroxyethyl cellulose and hydroxypropyl cellulose are good candidates for serving as the excipient for peptide stability studies. Among those, polyethylene glycol, polyethylene oxide, and sucrose were formulated with peptide VYPNGA. These excipients were made with 5% (w/v) and dissolved in CAPS buffer. The VYPNGA peptide was added to each excipient solution at a concentration of 100mg/ml. After lyophilization, they were placed in the stability chamber at 50 [degrees]C with RH of (sucrose 30%, PEG 75%, and PEO 95%). At time 0 and other predetermined time intervals the samples were analyzed with HPLC. Conclusion: The sucrose will recrystallize in 7 days. PEG, PEO, hypromellose, dextran 500, hydroxyethyl cellulose, and hydroxypropyl cellulose are potential good candidates for peptide stability studies. VYPNGA peptide have complex chemical reactions when formulated with PEO and PEG, and the peptide mass balance was achieved in PEO and sucrose.
RESONANCE ENERGY TRANSFER STUDIES OF SUBUNIT EXCHANGE KINETICS AND EQUILIBRIUM DIMERIZATION IN THE LAMBDA CRO REPRESSOR
Haifeng Jia* and Michael C. Mossing, University of Mississippi, University, MS 38677
The Cro repressor helps to regulate the master switch that controls the development of bacteriophage lambda, a longstanding paradigm for the control of gene expression. Dimers of Cro are required to recognize operator DNA and repress transcription. Dimerization of Cro is weak relative to DNA binding, and slow relative to other processes required for its production and function. At concentrations typical for DNA binding, most free Cro subunits exist as isolated monomers. Folding and assembly of Cro dimers from unfolded states have been shown to be limited by slow proline isomerization (Satumba and Mossing, Biochemistry 2002, 41, 14216-24). Here we demonstrate that exchange of subunits between Cro dimers is also slow under native states. Exchange of subunits between dimers can be monitored by Fluorescence Resonance Energy Transfer (FRET). Several single-cysteine variants were used to study dimerization equilibria and subunit exchange kinetics. Unique cysteine residues were covalently modified either with the donor fluorophore iodoacetamidoaedans (IAEDANS) or the acceptor 5- iodoacetamido-fluorescein (IAF). The labeled subunits with IAEDANS as donor and IAF as acceptor allow measurement of dimer dissociation and subunit association. Subunit exchange experiments initiated by mixing pre-equilibrated donor and acceptor samples resulted in slow kinetics that were independent of protein concentration but highly dependent on temperature. A simple kinetic model for subunit exchange predicts that the observed rates for this mixing protocol will always be identical to the dimer dissociation rate. Titration of a trace amount of highly fluorescent acceptor subunits by excess donor subunits allow straightforward determination of the fraction of acceptor subunits in dimers by FRET, and thus the dimer dissociation equilibrium constant (Kd). Thus, the association rate constant could be calculated, which then was confirmed by the DNA binding experiments.
INVESTIGATING THE IMPACT OF BIOCIDE BEHAVIOR IN THE PRESENCE OF SURFACTANT AND POLYMER MOLECULES
Adam Hathorne*, Alicyn M. Rhoades, and Douglas A. Wicks, University of Southern Mississippi, Hattiesburg, MS 39406
The problem of latex degradation by microbial action is of vital importance, and the development of new and more effective methods of antimicrobial treatment is an important area of current research. The focus of this project is to determine the minimum inhibitory concentration (MIC) values of two biocides provided by ISP Nuosept[R] 95 and Nuosept[R] 495, versus Pseudomonas aeruginosa when in the presence of surfactant molecules and also within a latex environment. The environment of a biocide molecule impacts resulting efficacy, and ultimately these studies lay the groundwork for the development of new environmentally compatible biocides. These surfactant solutions contain both ionic and nonionic end groups. Based on commercial applications, the expected MIC values are 483 mg/L for Nuosept[R] 95 and 966 mg/L for Nuosept[R] 495. Using standard culture plating techniques the MIC of Nuosept[R] 95 in the surfactant solutions has been determined to be between 97 mg/L and 579 mg/L and for Nuosept[R] 495 to be between 576 mg/L and 966 mg/L. It is hypothesized that the decrease from the theoretical values is due to the presence of the negatively charged end groups of the surfactants. Nuosept biocide behavior as determined in surfactant solutions is compared to the behavior of gentamicin in surfactant solutions, as well as the behavior observed for the same biocides in a latex environment. Gentamicin is reported as having a MIC of 0.25 mg/L in water but was measured as 1050 mg/L in the presence of surfactant molecules.
INTERCALATION OF SMALL MOLECULES INTO HYDROGEN-BONDED SOLIDS
Bentley Curry* and Alicia M. Beatty, Millsaps College, Jackson, MS 39210 and Mississippi State University, Mississippi State, MS 39762
Utilizing organic compounds such as 3,5-PDCA, 3,5-PzDCA and amines such as octylamine and diaminododecane, we are able to create layered solids. The layers of these crystals are hydrogen-bonded as well as ionic, but only hydrophobic components are found between the layers, making them ideal, we believe, for intercalation to occur. Taking advantage of the relatively weak interactions between layers of these hydrogenbonded crystals, guest molecules can squeeze into the lattice of the crystalline structures. Our study includes intercalation experiments using solvents of varying boiling points (volatility) as well as different sizes in order to fully explore the abilities of these crystalline structures to intercalate. The materials have been studied using DSC, TGA, and powder X-ray diffraction to determine the presence of any guest molecules. We will report on several techniques and methods that we have used for intercalation, and data collected to support our hypothesis.
CALCIUM-DEPENDENT STABILITY OF E-CADHERIN DOMAIN 1 AND 2
Susan Pedigo*, Alka Prasad, and J. Matthew Rutherford, University of Mississippi, University, MS 38677
Epithelial cadherin is important in establishing and maintaining cell to cell interactions in epithelial cells thereby playing an important role during morphogenesis. The epithelial cadherin molecules have three main regions- the N-terminal extracellular region, the transmembrane region that spans the cell membrane once, and the C-terminal cytoplasmic region that communicates with the cytoskeletal actin filaments through catenins. Crystallographic studies done by Shapiro showed that N-terminal domains have two types of interactions which we designate as cis- and trans- interactions, both of which are mediated by domain 1 (Shapiro et al., 1995, Nature 374:327-370 CAD1). We report studies of the calcium dependent stability of extracellular Domains 1 & 2 of epithelial cadherin as a two domain construct (ECAD12). The molar extinction coefficient was determined using the Edelhoch method and found to be independent of the calcium. CD spectra of the ECAD12 indicated a typical beta-sheet conformation in all solution conditions. There was a significant calcium-dependent decrease in the signal 235 nm (tryptophan). Thermal and denaturant-induced unfolding was monitored by CD. DSC experiments were performed in the presence of either 10 [micro]M EGTA or 5 mM [Ca.sup.2+]. General observations were made from these experiments. The apo-state fitted well to a 3-state model. Both transitions were less stable than the unfolding of the isolated Domain 2, indicating that the domains were destabilized in the two domain construct. Calcium stabilized ECAD12 as witnessed by an increase in Tm (40 [degrees]C in Apo to 66 [degrees]C in 10 mM [Ca.sup.2+]) and delHm (a 3 fold increase from Apo to 10 mM [Ca.sup.2+]), and an increase in [D]1/2 for both Urea and GdnHCl. With calcium added, the unfolding transitions were highly cooperative. DSC transitions shifted from ~40 to 65 [degrees]C and narrowed upon adding calcium.
TREE SEARCH NEIGHBORHOODS FOR THE PROTEIN FOLDING PROBLEM IN HP LATTICE MODEL
Haitao Li (1*), Cesar Rego (1), and Fred Glover (2), (1) University of Mississippi, University, MS 38677 and (2) University of Colorado, Boulder, CO 80309
We examine a prominent and widely-studied model of the protein folding problem, and provide two new methods for the neighborhood search in metaheuristic algorithms. Given a sequence of amino acids, the protein folding problem (PFP) consists of predicting the native tertiary structure (i.e., conformation) of the corresponding protein. One of the most widely studied biophysical models of protein folding is the hydrophobic-hydrophilic (HP) model. In this study we consider the popular two-dimensional (2D) version of the HP model where chains of amino acids are configured as self-avoiding paths on a regular square lattice in which vertices are labeled by the amino acids. An optimal conformation maximizes the number of pairs of hydrophobics that are adjacent on the lattice and not consecutive in the sequence. In this research we propose two neighborhood search methods based on a tree search framework for the problem under investigation. A fundamental feature of the proposed search methods is the use of neighbor-hoods capable of exploring the solution space in a dynamic and adaptive fashion. In one algorithm this is accomplished through a tree search neighborhood built upon a filter-and-fan (F & F) approach. In another a specialized ejection chain method (EC) is designed to generate compound moves. Computational results obtained on a standard set of benchmark problems indicate that the F & F algorithm can be advantageously compared to the state-of-the-art algorithms and that the EC algorithm clearly outperforms all of them, affording a new advance for practitioners who seek to handle applications in this area.
USE OF SURFACTANTS IN MODIFYING THE SURFACE CHARACTERISTICS OF NATURAL FIBERS FOR USE IN POLYMERIC COMPOSITES
Kapil Inamdar*, Ellen Lackey, and John O'Haver, University of Mississippi, University, MS 38677
Natural fibers are hydrophilic which creates problems when they are used as reinforcements in polymeric composites. The polymeric matrix material has difficulty in penetrating and coating these natural fibers to form a good solid product due to the presence of hydroxyl (-OH) groups on the fiber surfaces. This study aims at treating hemp/jute fiber surfaces with different surfactant solutions in an attempt to achieve a hydrophilic-hydrophobic surface character transition of the hemp/jute fibers. We hope to understand the basic surface characteristics of the hemp/jute fibers and use the knowledge gained from the initial experiments as the building blocks for further product development and optimization. The fibers will be treated with surfactant solutions at different concentrations (to make the fiber surface hydrophobic), providing data for an adsorption isotherm. The understanding of the various isotherm regimes will be used to choose the different surfactant concentrations that should be used in further studies (for best results). A KSV Sigma 70 tensiometer will be used to do powder wettability studies on the hemp/jute fibers. Theoretically a liquid capable of wetting a solid should yield a contact angle between 0 and 90 degrees with the former indicating complete wetting. The aim being to make the fibers hydrophobic, the contact angles of water and the resin with the fibers should increase and decrease, respectively, indicating effective use of the surfactant.
MICHAEL ADDITION IN THIOL-ENE SYSTEM POLYMERIZATION
Birsen Varisli* and John A. Pojman, University of Southern Mississippi, Hattiesburg, MS 39406
Thiol-ene polymerization by means of Michael addition is possible with amines as catalyst, from primary to tertiary. Other catalysts involving nitrogen atoms are possible to use too. We established that any primary amine can catalyze the bulk polymerization of the system, with the exemption of the aromatic amines. Also most of the secondary amines are able to catalyze the reaction with the same exemption for the aromatic ones. No tertiary amine is able to catalyze the Michael addition in the Thiol-ene system but 4-(aminomethyl) pyridine. Also we have tested carbamate systems. Carbamates behave in different manner depending of the cations on them. We have showed that the ammonium carbamate is the most active one when it reacts together with 18-crown-6 ether. It promotes a fast polymerization and the formation of a foam as a product.
SYNTHESIS OF NON-SYMMETRICALLY SUBSTITUTED PERYLENETETRACARBOXYLIC BISIMIDES WITH PEG SWALLOWTAILS
Ramakrishna Samudrala* and Daniell Lewis Mattern, University of Mississippi, Oxford, MS 38677
Non-symmetrically substituted perylenetetracarboxylic bisimides, which may serve as molecular rectifiers of electricity, were synthesized with pyrenemethyl, pyrenebutyl or phenylethyl groups connected to one imide nitrogen and the 10-(2,5,8,12,15,18-hexaoxanonadecyl) group, serving as polyethylene-glycol (PEG) swallowtail, connected to the other imide nitrogen. The 2,5,8,12,15,18-hexaoxa-10-nonadecanamine (swallow tail) was prepared by protecting serinol's nitrogen with benzyl protecting groups and then attaching 2-methoxyethoxyethyltosylates to the alcoholic oxygens, followed by deprotection of the benzyl groups. These nonsymmetric bisimides were soluble in organic solvents like CH[Cl.sub.3], but insoluble in water.
PHOTOMUTAGENECITY OF POLYCHLORINATED BIPHENYLS, A CLASS OF ENVIRONMENTAL POLLUTANTS
Esabel Neto*, Elgenaid Hamadain, and Hongtao Yu, Jackson State University, Jackson, MS 39217
Chemical agents represent a largest source of environmental mutagens. Human are constantly exposed to a variety of natural and synthetic chemicals. Among these toxic chemicals is a class of compounds called polychlorobiphenyls (PCBs). These compounds are produced from industrial sources and have been a major concern of the public as they are classified as priority pollutants by the US Environmental Protection Agency (US EPA). These compounds contain the biphenyl rings with multiple substitutions of chlorine atoms. Human contact with these compounds occurs via inhalation, ingestion and absorption through the skin. Since these compounds absorb light, exposure to light should contribute to both the environmental fate and the toxicity of PCBs. Fourteen PCBs were selected randomly in this study, from lower to higher chlorine substituted and they are tested with conventional Ames test for photomutagenicity with modifications. Salmonella typhimurium histidine auxtrophic bacteria strain TA 102 were exposed to light irradiation in the presence of PCBs with concentrations of 0, 5, 10, 25 [micro]M, respectively. After incubation, the number of revertant bacteria colonies, which signifies mutation events, was counted. The results shows that 2,6-dichloro- 3,4,5- trichloro, -2,3,5,6-tetrachloro, and 2,2'3,4'-, 2,2',3,4,5-pentachlorobiphenyl, 2,2',4,4',5',6-heptachlorobiphenyl are photomutagenic, producing at least twice the reverted colonies at the light control. On the other hand, 4,4'-dichloro-, 3,3',4,4',5-pentachloro-, 3,3,4,4'5,5'-hexachloro, 2,2',3,4,5,6,6'-heptachloro-, 2,2'3,3',4,5,6,6'-octachlorobiphenyl are not photomutagenic. A structure-photomutagenicity, relactionship is being established.
NITRIC OXIDE SENSOR USING MYOGLOBIN IMMOBILIZED IN SOL-GEL AND NAFION MATRICES
Sarah Mohamed*, Anandhi Ray, Hiroyasu Tachikawa, and Elgenaid Hamadain, Jackson State University, Jackson, MS 39217
Electrochemical reduction of NO was observed at glassy carbon electrode modified with myoglobin film and covered with Nafion and in sol-gel encapsulated myoglobin. Detection was carried out by cyclic voltammetry under aerobic and anaerobic conditions. Determination of NO at a reduction potential (-0.75 V vs. Ag/AgCl), shows no interference from such species as nitrate, nitrite, ascorbic acid, carbon dioxide and dopamine. Immobilization of Mb by physically trapping the molecules in individual pores of the sol-gel matrix permits the molecules to be isolated, stabilized and used as NO sensor. Electrochemical experiments were carried out using a cypress systems model CS-1190 computer-controlled potentiostat system. The electrochemical cell used consists of a (3 mm) GC disk electrode covered with either Mb and Nafion or sol-gel as working electrode, a platinum wire as auxiliary electrode and an Ag/AgCl as a reference electrode. In sol-gel modified electrode, the solution was prepared by hydrolyzing 1 ml of tetramethylorthosilicate (TMOS) with 30 [micro]l of .04 M of hydrochloric acid and 225 [micro]l of distilled water. Equal amount of this sol was mixed with 1 mM myoglobin solution. Upon addition of protein solution, the gelation occurred within few minutes. The peak corresponding to metmyoglobin reduction appears at around -0.25 V in the Nafion and sol-gel matrices. Upon addition of NO saturated solution new peak appears around -0.75 V. Various amounts of NO saturated solution was added and corresponding changes in the amplitude of the reduction peak was observed. Results show that myolgobin in nafion and sol-gel matrices can be used as NO sensors.
8:00 MISCIBLE FLUIDS IN MICROGRAVITY (MFMG)--AN INVESTIGATION ON THE INTERNATIONAL SPACE STATION
John A. Pojman (1*), Nick Bessonov (2), and Vitaly Volpert (2), (1) University of Southern Mississippi, Hattiesburg, MS 39406 and (2) Universite Lyon I, F-69622 Villeurbanne Cedex, France
A zero-upmass investigation was performed on the International Space Station, called Miscible Fluids in Microgavity (MFMG). The goals of the experiment were to determine if miscible fluids, honey and water, could exhibit transient interfacial phenomena. Specifically, we tested if a stream of honey into water could exhibit the Rayleigh-Tomotika instability and if a blob of water in honey would spontaneously become spherical. No dramatic phenomena were observed. We used a model consisting of the heat and diffusion equations with convective terms and of the Navier-Stokes equations with an additional volume force written in the form of the Korteweg stresses arising from nonlocal interaction in the fluid. It is proportional to the square of the composition gradient with the proportionality coefficient depending on temperature. We performed simulations of drops and streams of miscible fluids and showed that it is possible for transient phenomena to occur that are similar to that observed with immiscible fluids. Specifically, we show that an aspherical drop can spontaneously become spherical and that a stream of a fluid can exhibit a Rayleigh instability. We also simulated a miscible drop migrating in a temperature gradient. By comparing simulations to the MFMG results, we are to set an upper limit on the value of the Korteweg stress parameter, at least for honey and water.
8:15 EXPRESSION OF HUMAN PEPTIDE HORMONES IN INSECT CELLS
Amanda Parker* and Robert C. Bateman, Jr., University of Southern Mississippi, Hattiesburg, MS 39406
Many peptides and peptide hormones are synthesized as larger precursors that require the action of enzymes in the secretory pathway to become fully active. The sequence of these processing enzymes is highly conserved from humans down to insects. In order to study peptide hormone processing a model insect system will be developed. The human gonadotropin-releasing hormone (GnRH) will be expressed in the S2 cell line derived from Drosophila melanogaster. Subsequent production of GnRH will show the ability of the processing enzymes in the insect secretory pathway to properly process human peptides. Establishment of the Drosophila system for the production of peptide hormones will aid in the identification of which enzymes are necessary for hormone maturation in humans. Also, the system could provide a means of secreting large amounts of human hormones for biotechnology and drug development. Similarities between insect and human peptide processing enzyme function will suggest an evolutionary relationship among peptide biosynthetic pathways.
8:30 ARE MOLECULES AT A SOLID/SOLUTION INTERFACE AFFECTED BY GRAVITY?
Newton Fawcett (1*), Richard D. Craven (1), Ping Zhang (2), and Jeffrey A. Evans (1), (1) University of Southern Mississippi, Hattiesburg, MS 39406 and (2) Reichold, Inc., Durham, NC 27703
Molecules in homogeneous solution do not spontaneous settle because their thermal kinetic energy (kT) energy is [10.sup.6]-[10.sup.7] times greater than their potential energy due to gravity. However solvated molecules adsorbed or bonded to a solid surface in contact with a solution are inhomogeneous with respect to the bulk solution. Furthermore, there is a large decrease in entropy associated with immobilization on a surface. Will, therefore, molecules at a solid/solution interface be affected by the Earth's gravitational field? This question is addressed experimentally using a quartz crystal microbalance, a device that is itself immune to gravity. Evidence is presented showing that DNA macromolecules, solvated in aqueous buffer at room temperature, collapse toward an up facing surface and away from a down facing surface. It is also experimentally shown that, to hybridize, DNA must move away from an upfacing surface.
8:45 POLYMER-DISPERSED AQUEOUS MATERIALS
Kayce Leard* and John A. Pojman, University of Southern Mississippi, Hattiesburg, MS 39406
The focus is to prepare hydrophobic polymeric materials in which an aqueous phase is distributed throughout the polymer matrix as droplets. Depending on the composition of the aqueous phase, the resulting material could respond to various external stimuli, such as magnetic fields, electric fields, or volatile compounds. The thin films consist of water droplets dispersed among a continuous polymer phase, and the films are prepared via reverse microemulsion polymerization of a surfactant, water, and acrylate mixture. The surfactant, Aerosol-OT is employed to encapsulate the nanometer-sized aqueous molecules within a surfactant monolayer. Photopolymerization of the microemulsion solution produces an opaque polymer, therefore the initially nanometer-sized droplets aggregate to sizes large enough to scatter visible light. Opaque films contained at 100% relative humidity will retain the opaque quality, while films exposed to lower humidity levels become transparent. The macroscopic humidity response is a quasi-reversible phenomenon that is assumed to result from water droplets shrinking in size or evaporating from the films. To determine the exact cause of the quasi-reversible hydration, we are using Thermal Gravimetric Analysis (TGA) and Attenuated Total Reflection Infrared Spectroscopy (ATR-IR). Comparison and analysis of data from both techniques suggest water does evaporate from the films, and completely dehydrated (i.e., transparent) films cannot be re-hydrated by sealing them in a saturated environment. Additionally, ATR-IR and Small angle Light Scattering (SALS) together indicate that the water droplet distribution is not uniform throughout the films. This hypothesis will be further investigated with phase contrast and Scanning Electron Microscopy (SEM).
9:00 CHEMICAL PROFILING AND ANTIMICROBIAL ANALYSIS OF A TRADITIONAL HERBAL MEDICINE CONTAINING GARLIC AND BLACK CUMIN
Jiben Roy (1*), Diaa M. Shakleya (2), Patrick S. Callery (2), and Jhon G. Thomas (2), (1) Mississippi University for Women, Columbus, MS 39701 and (2) West Virginia University, Morgantown, WV 26506
A combination of crushed garlic and black cumin seeds has been used as a traditional remedy for urinary tract infections. In-vitro antimicrobial testing suggested that the mixture of two spices in the ratio of 1:1 has antimicrobial effects on both Staphylococcus aureus and E. coli species. Analyses of the extract of garlic and black cumin by GC-MS as well as LC-MS & MS/MS confirmed that the main components of garlic were allicin, y-glutamyl-S-allylcysteine and allicin transformed products such as diallyldisulfide and vinyldithiins. Components of black cumin were thymoquinone, p-cymene, p-tert-butylcatechol, and pinene. Isolated samples of allicin by preparative HPLC from garlic extract and reference samples of diallyldisulfide and thymoquinone were tested individually and in combination for their antimicrobial activities against S. aureus and E. coli. All of these compounds showed modest antimicrobial effects individually (except diallyldisulfide against E. coli) and in combination.
9:15 ORGANIC SYNTHESIS AND CHROMATOGRAPHIC SEPARATION OF [4+2] CYCLOADDITION REACTION PRODUCTS FROM METALLIC NITRIDE FULLERENE (MNF) NANOMATERIALS
Steven Stevenson (1*), Helen Yu (1), Ryan Stephen (1), Shanna Lavergne (1), Ivory Dean (1), Jonathan Dupont (2), and Christy Dyess (2), (1) University of Southern Mississippi, Hattiesburg, MS 39406 and (2) Mississippi School for Math and Science, Columbus, MS 39701
The recently discovered metallic nitride fullerene (MNF) nanomaterials have generated interest within the scientific community due in part to their unique structural and electronic properties. A striking feature is the presence of an internal metallic nitride nanocluster which is encapsulated within the carbon cage housing (e.g., C80). Emerging applications include their use in medicine (e.g., MRI contrast agents). However, development of MNF-based pharmaceuticals depends on the ability to functionalize the MNF carbon cage. Unfortunately, a paucity of MNF reactivity data hampers research application development. With little research in the organic synthesis and derivatization of the MNF carbon cage surface, the objective of this research is the investigation of MNF cage reactivity. The selected reaction type is a [4+2]cycloaddition to the cage, functionalized via o-quinodimethane intermediates. Results indicate the presence of mono- and bis-adducts for these MNF nanomaterials. Generation of the reactive o-quinodimethane diene and subsequent cycloaddition is performed under refluxing 1,2,4-Trichlorobenzene. The reaction products are chromatographically separated and isolated. Purified MNF adducts have been characterized by NMR and mass spectrometry. In conclusion, cycloaddition reactions with MNFs are feasible and result in novel, functionalized nanomaterials. Mono-adduct formation is favored versus bis-adducts.
9:30 MOLECULAR DYNAMICS STUDIES OF THE BT TOXIN CYTIA IN SOLUTION
Xiaochuan Li (1*), Jun Xie (2), Dexuan Xie (2), and Peter Butko (1), (1) University of Southern Mississippi, Hattiesburg, MS 39406 and (2) University of Wisconsin, Milwaukee, WI 53201
A protein's structure determines its function. Ideally, knowledge of structure along with the dynamics and energetics of atomic motions, provides a good insight into the behavior of a protein. By using CHARMM, a molecular dynamics software, we performed a computer simulation of the protein Cyt1A from Bacillus thuringiensis var. israelensis, which is a mosquito-specific toxin. Considering the lack of experimental data on the interaction between Cyt1A and the cell membrane, computer simulation appears to be an ideal tool to study this interaction. Dynamics of Cyt1A and mutated Cyt1A (Lys225 to Ala) in water with periodic boundary condition were run in CHARMM. The minimization revealed that the major contribution to the total energy is the electrostatics. The simulation results identified the most flexible regions of the protein, which might be involved in its binding to the membrane. Since electrostatic interactions play an important role in the toxin's function, we employed the Adaptive Poisson-Boltzmann equation Solver (APBS) to map the electrostatic interaction between the protein and the solvent. The APBS uses the finite element or finite difference methods to solve the related nonlinear second order partial differential equations. Our results are in accord with the few available pieces of experimental data and will serve as a basis for the future simulation of the toxin in the presence of the lipid membrane.
9:45 THE CHARACTERIZATION OF DENDRITIC POL YOL/CLAY NANOCOMPOSITES
Jillian Danner (1*), Sergei Nazarenko (2), and Sarah E. Morgan (2), (1) Mississippi University for Women, Columbus, MS 39701 and (2) University of Southern Mississippi, Hattiesburg, MS 39406
In an effort to eventually determine the intercalation spaces of dendritic polyols, two known procedures were tested to determine the optimal method of testing as well as to determine the effect of thermal history and polydispersity of polyol/clay nanocomposites. A third, more optimal, method was created and tested and all methods were compared to determine the effect of the glass transition on the reaction. A nanocomposite of various synthetic and natural clays and second, third, and fourth generation dendritic polyols were synthesized via intercalation and exfoliation. The reactions were then re-prepared so the surface topology of the nanocomposite films could be examined via Atomic Force Microscopy.
10:00 MECHANICAL AND INTERFACIAL BEHAVIOR OF AMPHIPATHIC NATURAL AND SYNTHETIC POLYMERS
Sonya D. Benson*, Gordon C. Cannon, Charles L. McCormick, and Sarah E. Morgan, University of Southern Mississippi, Hattiesburg, MS 39406
The mechanical and interfacial behavior of amphipathic natural and synthetic polymers is reported. The natural amphipathic polymers called hydrophobins have been isolated from the wood-rotting fungus Schizophyllum commune and from three edible fungal sources: Agaricus bisporus, Lentinans edodes, and Pleurotus ostreatus. The amphipathic synthetic polymers evaluated are nonionic surfactants composed of triblock copolymers of polypropylene oxide and polyethylene oxide. Natural and synthetic solutions of varying concentrations were applied to substrates of varying hydrophobicity using the adsorption technique. Changes in substrate morphology were monitored using tapping mode atomic force microscopy. Adhesion characteristics of unmodified and modified substrates were evaluated using advanced atomic force microscopy techniques. The ability of both natural and synthetic polymers to modify the polarity of substrates was evaluated using contact angle analysis. Owens-Wendttheory was used to determine the polar and dispersive components present on both unmodified and modified substrates. Natural hydrophobins are significantly better surface modification agents than the synthetic triblock copolymer studied. Hydrophobins significantly increased the polarity of hydrophobic substrates at much lower concentrations than the synthetic polymers without significant alteration of substrate morphology. Acknowledgements: Major support for these studies from the National Science Foundation Materials Research Science Engineering Center (DMR 0213883) is gratefully acknowledged.
10:30 CONDUCTIVITY DEPENDENCE OF PEG CONTENT IN AN ANHYDROUS PROTON CONDUCTING SOL-GEL ELECTROLYTE
Braja D. Ghosh* and Jason Ritchie, University of Mississippi, University, MS 38677
Proton conducting polymer electrolytes have important applications in electrochemical devices such as fuel cells and electrochromic displays. We have prepared anhydrous proton conducting electrolytes composed of mixtures of our "MePEG polymer," a sol-gel based MePEGn polymer, and a MePEGnS[O.sub.3]H acid. Our goal is to gain a fundamental understanding of the mechanism of anhydrous proton conductivity in our MePEG polymer. We have shown that H+ transport is dependant on the volume fraction of polyethylene glycol (PEG) present and that the Grotthus mechanism of H+ transport dominates at low acid concentrations. Here the molar equivalent conductivity of the MePEGnSO3H acid is linearly correlated with the inverse of volume fraction of PEG (Vf,PEG). This indicates that volume fraction of PEG is a strong factor controlling the conductivity in these solutions of acid and polymer. In addition, the dependence on the concentration of PEG supports the Grotthus mechanism of conductivity. Moreover, the lack of a dependence of equivalent conductivity on the size of the MePEGnS[O.sub.3]H acid indicates no contribution from the vehicle mechanism of [H.sup.+] conductivity.
10:45 DIFFUSE REFLECTANCE INFRARED FOURIER TRANSFORM SPECTROMETRY (DRIFTS) ON MINERAL ADDITIONS TO JSC MARS 1 SIMULANT SOIL
Nicholas A. Phillips (1*), Charles Smithhart (1), and Richard Ulrich (2), (1) Delta State University, Cleveland, MS 38733 and (2) University of Arkansas, Fayetteville, AR 72701
Many substances such as hydrates, sulfates, carbonates, and oxides have been discovered to be on Mars either on the surface or in the atmosphere. These minerals indicate that Mars may once have had liquid water on its surface. This experiment is designed to take DRIFTS readings on Mars simulant soil with mineral additions, and it is also designed to determine if DRIFTS is a useful method of identifying elements on the surface of Mars. Minerals were added to the soil in different percentages, and then DRIFTS was used to determine where the functional groups of the mineral additions appeared in the infrared spectra. The minerals added in this experiment included calcite, magnesium sulfate, hematite, and olivine. All of these minerals produced observable peaks in the infrared spectra due to the particular functional group of the mineral, and spectra were collected for all of the mineral additions to the simulant soil. These spectra indicate that DRIFTS would be a useful method of identifying elements on the surface of Mars.
11:00 ELECTRONIC EXCITATION OF TiO IN DIFFUSION FLAME
Chandra M. Pathak, Alcorn State University, Alcorn State, MS 39096
Electronic excitation of molecular species such as [C.sub.2], formed in the flame produced by burning butane in air, has been fairly well known. The study of such flames have yielded spectroscopic data of considerable interest and importance involving both the ground state and the upper electronic states of the molecules formed in the flames. The present study was undertaken in the expectation that under appropriate conditions of excitation in a diffusion flame, a diatomic or a tri-atomic species can be formed in an excited state and an electronic transition to a lower state may give rise to a new electronic band system in the molecule formed in the flame. Diffusion flames have in the past given rise to a number of new electronic band systems of several species as a consequence of the highly exothermic elementary reactions occurring in such systems which produce overpopulations of certain excited states, yielding emission that would be unobservable under thermal excitation. Four new electronic band systems were observed in the emission spectrum of a low pressure diffusion flame of Ti[Cl.sub.4] plus oxygen burning in potassium vapor. The new systems, all of which lie in the ultraviolet region, are attributed to TiO. Two of them have also been observed in emission from a Ti[Br.sub.4][O.sub.2]-K flame. One system appears to involve transition to the ground, [X.sup.3][[DELTA].sub.r], state. The lower state of the other three systems seems to be the low-lying singlet state of TiO. The new bands permit two new excited states to be located with some certainty: a triplet state at 32,000 [cm.sup.-1] and a [.sup.1][SIGMA] state at 30,970 [cm.sup.-1].
11:15 THE ACCURATE CALCULATION OF RO-VIBRATIONAL EIGENENERGIES OF HYDROGEN CYANIDE
Joseph Bentley* and Jennifer L. Curry, Delta State University, Cleveland, MS 38733
A methodology for accurately calculating the quantal ro-vibrational energies of light-heavy-heavy (LHH) triatomic molecules is presented. Calculated ro-vibrational energies of the ground electronic state of HCN are given for J < 3. The discrete variable representation (DVR) [J. C. Light and T. Carrington, Jr., Adv. Chem. Phys. 114:263 (2000)] is used as a basis set for radial coordinates. An angular basis set is used which diagonalizes the rotational (J > 0) part of the total kinetic energy. It is shown how this basis is contracted through a series of diagonalizations of smaller Hamiltonian matrices. The final basis set is a direct product of these contracted angular functions and the primitive radial DVRs. Diagonalization of the full Hamiltonian in this final basis set gives the ro-vibrational energies of HCN. These are compared with an earlier calculation.
11:30 IRREVERSIBLE PHOTOOXIDATION USING NSUBSTITUTED HETEROAROMATIC SYSTEMS
Wolfgang Kramer, Millsaps College, Jackson, MS 39210
Photoinduced homolytic N-O bond cleavage in N-alkoxyheterocycles has been shown to be an efficient pathway to oxygen-centered radicals and/or aromatic radical cations. The reaction pathway should depend upon the stability of the oxy-radical product. The use of N-phenoxy compounds should lead to the formation of a stable phenoxy radical, that would increase the overall efficiency of the fragmentation reaction. Synthesis of N-phenoxyheterocycles involves the reaction of the aromatic N-oxide with a diazonium salt. The synthesis and photochemistry of ArN+-OAr compounds, and their use as irreversible photooxidants is discussed.
11:45 POLYHEDRAL OLIGOMERIC SILSESQUIOXANE (POSS) CAGES WITH ATOMIC ALKALI, NOBLE GAS, TRANSION METAL AND HALOGEN IMPURITIES
Delwar Hossain (1*), Charles U. Pittman, Jr. (1), Svein Saebo (1), and Frank Hagelberg (2), (1) Mississippi State University, Mississippi State, MS 39762 and (2) Jackson State University, Jackson, MS 39217
Octahydridosilsesquioxane, (HSi[O.sub.3/2])[.sub.8], or the Polyhedral Oligomeric Silsesquioxane (POSS) [T.sub.8] cage system and its derivatives have attracted considerable interest. The POSS monomer [T.sub.8] cage consists of silicon atoms occupying the vertices of a cube and oxygen atoms bridging each pair of silicon atoms. In the parent octahydridosilsesquioxane, a single hydrogen atom is attached to each silicon atom. In general, POSS derivatives exhibit the composition (RSi[O.sub.3/2])[.sub.2n], where R denotes an organic ligand. POSS derivatives incorporated into organic polymers, dendrimers, and zeolites have attracted substantial attention due to their applications in material science and catalysis. One interesting feature of these cages is the encapsulation of atoms and ions. Several studies, including our own, have focused on this property. Most experimental and theoretical studies reported in the literature have focused on the pure or the metal-substituted parent POSS cage with or without encapsulated species. We will present a comparative study on endohedral complexes [X@(HSi[O.sub.3/2])[.sub.8]], [X@(HSi[O.sub.3/2][.sub.10]], and [X(HSi[O.sub.3/2]][.sub.12] of [T.sub.8], [T.sub.10], and [T.sub.12] cages respectively. Investigations have been carried out on [T.sub.8], [T.sub.10], [T.sub.12] cages which encapsulate the atomic or ionic species: [Li.sup.+], [Na.sup.+], [K.sup.+], [F.sup.-], [Cl.sup.-], [Br.sup.-], He, Ne, Ar, and first row transition metal atoms or ions. B3L YP/6-31G**, B3LYP/6-311G**, B3LYP/6-311++G** levels of theory were employed. Geometric, energetic and electronic properties were investigated. Endohedral noble gas atoms cause the cages to expand. The extent of the expansion depends the size of the encapsulated atom. Endohedral alkaliions and tranision metal atom/ions in contrast, exhibit both attractive and repulsive interactions with the cage atoms.
1:00 AN INVESTIGATION ON MICROENCAPSULATION OF CARBON TETRABROMIDE
Max Bonner*, John A. Pojman, and Brian McFarland, University of Southern Mississippi, Hattiesburg, MS 39406
The goal of the study was to encapsulate carbon tetrabromide via interfacial polymerization or complex coacervation. The study of interfacial polymerization lead to poor experimental data due to the interaction of carbon tetrabromide with a non-miscible monomer. However, the encapsulation method of complex coacervation of gelatin and gun arabic introduced two miscible poylelectrolytes that formed a liquidliquid phase. As the pH was altered and crosslinking occurred a dense coacervate shell encapsulated the core material. The carbon tetrabromide capsules were then analyzed using atomic transfer radical polymerization of tri (ethylene glycol) dimethacrylate in an oxygen-free environment.
1:15 DETERMINATION OF CRITICAL CONDITIONS FOR THE EXISTENCE OF FRONTAL POLYMERIZATION WITH MULTIFUNCTIONAL ACRYLATES
Burcu Binici*, Nesrin Olten Kocaeli, and John A. Pojman, University of Southern Mississippi, Hattiesburg, MS 39406
Frontal polymerization is a mode of polymerization in which a localized reaction zone propagates from the coupling of thermal transport and the Arrhenius-dependence of the reaction rate of an extensive polymerization. Because frontal polymerization is similar to combustion, it is very sensitive to heat loss. We studied the effects of reactor diameter, reactor medium and filler amount and type on the existence of frontal polymerization for multifunctional acrylates with a peroxide initiator.
1:30 ANALYSIS OF BIFIDOBACTERIUM USING CAPILLARY ELECTROPHORESIS
Timothy Ward*, Aprile McGilvray, Courtney Vowell, Jason Eastlack, David Smith, and Robert Nevins, Millsaps College, Jackson, MS 39210
Identifying and quantitating bacteria and other microorganisms is a difficult problem that is becoming increasingly important. The traditional method for characterizing microorganisms by isolation of pure cultures is slow and tedious. At the present time, there are no reliable and easy to perform techniques for separating and identifying intact microorganisms. Recently, a number of groups have explored the possibility of applying the technique of capillary electrophoresis in order to separate intact bacteria. The application of this technique is advantageous, because it allows the bacteria to remain intact while being analyzed quickly and efficiently with broad applicability. In general, microorganisms tend to be amphoteric, containing multiple charges thus ideally suiting them for analysis by electrophoresis. In this study we have constructed calibration curves correlating colony forming units (CFU) to the absorption profiles of bacteria by UV detection using capillary electrophoresis. Good correlations between peak area and bacterial concentrations were obtained. In addition, we will present examples of bacterial separations via capillary electrophoresis and discuss the relevant characteristics that must be carefully controlled before a practical and useful separation can be achieved.
1:45 SYNTHESIS AND CHARACTERIZATION OF POLY (ETHYLENE GLYCOL) BASED DISCRETE HYDROGELS
Stacy Trey* and Douglas A. Wicks, University of Southern Mississippi, Hattiesburg, MS 39406
In this research we investigate how structural variations in discrete hydrogels, both chemical and mechanical, will affect water absorption and retention. We first synthesized poly(ethylene glycol) based hydrogels crosslinked with a polyhexamethylene diisocyanate crosslinker as films with varying PEG number average molecular weights ranging from 400 g/mol to 7,000 g/mol. A dispersion of PEG based acrylate functionalized hydrogel was also polymerized, composed of tolylene diisocyanate (TDI 2,4), PEG of Mn = 6000 g/mol, hydroxyehtylmethyacrylate (2-HEMA), and PEG monomethacrylate of Mn = 2000 g/mol. The absorption properties were evaluated by absorption studies and thermal gravimetric analysis (TGA). The films were characterized by solid state [.sub.13]C Nuclear Magnetic Resonance. The absorption kinetics were found by placing dehydrated hydrogels in a saline buffer solution containing the fluorescent probe 5-(and-6)-((N-(5-aminopentyl)amino)carbonyl) tetramethylrhodamine and tracking the intensity and shift in the absorption peak. The network structure as a function of chain motion was studied by observing the spin-lattice relaxation times of dehydrated and hydrated materials, and also as a function of temperature. It is clear from this research that morphological properties play an important role in determining the characteristics of PEG based hydrogel films.
2:00 CONCENTRATED ACID PRETREATMENT FOR THE CONVERSION OF LIGNOCELLULOSIC MATERIALS TO SUGAR
William Miller* and Roger D. Hester, University of Southern Mississippi, Hattiesburg, MS 39406
The first stage of a two-step concentrated sulfuric acid process that converts softwood sawdust to sugars has been explored. The research focuses on the ability of an in-house custom fabricated co-rotating twin-screw reactor (TSR) to effectively breakdown and solubilize crystalline cellulose into low molecular weight carbohydrates. This is achieved through intense mechanical shearing action of the lignocellulosic solids during exposure to sulfuric acid at elevated temperatures in the TSR. After the TSR system was placed into operation, an initial two level, three factor screening design of experiments (DOE) was performed to determine the importance of screw speed (70 rpm versus 110 rpm), reactor temperature (30 versus 50[degrees]C) and sawdust feed rate (2 versus 3 g/min). This screening DOE showed that screw speed was relatively insignificant in comparison to sawdust feed rate and reactor temperature. Based on the DOE screening results, a four-level, two-factor experimental model building DOE was undertaken. In this design two independent variables, sawdust feed rate and TSR temperature, were varied from 2 to 5 g/min and 40 to 70[degrees]C. Solid sawdust conversion to liquid, screw torque and TSR exit pressure were measured or recorded to yield percent conversion of solids, material energy requirements and processed material viscosity. Thereafter, model quadratic equations were fitted to the experimental data and the resulting statistical significance of these equations was evaluated.
2:15 SYNTHESIS OF A NEW IONIC LIQUID MONOMER
Zulma Jimenez* and John A. Pojman, University of Southern Mississippi, Hattiesburg, MS 39406
Ionic liquids can be defined as salts with a melting temperature below the boiling point of water, most ionic liquids are liquids at room temperature; they have properties like nonvolatility and high polarity. Some of them have been used as solvents in chemical reactions, e.g., in ring-opening polymerization of ehylene carbonate, condensation polymerizations leading to polyamides and polyimides, atom-transfer or conventional radical homopolymerizations of some acrylates and styrene. Triocylmethylammonium acrylate ([C.sub.28][H.sub.57]N[O.sub.2]) was synthesized from Aliquat 336 and acrylic acid. In order to produce this compound an appropriate amount of Aliquat 336 was combined with an aqueous solution of acrylic acid in a separatory funnel and agitated vigorously; the product was above the aqueous phase, it was washed with water to remove residual reagents and centrifuged to break the emulsion formed in the washing. The reaction was followed with a pH-tester, this is due to HCl production; in this way, pH can give an idea of the conversion degree. The ammonium acrylate was used in a simple polymerization reaction using luperox 231 as initiatior. Polymerization was initiated by heating the solution with a soldering iron. The polymer obtained is a viscous liquid. If copolymerized with a multifunctional acrylate, an opaque and brittle material is produced.
2:30 MEASUREMENT OF THE EFFECTIVE INTERFACIAL TENSION IN A MISCIBLE SYSTEM (1-BUTANOL-WATER) BY SPINNING DROP TENSIOMETRY
Jola Marszalek*, Renato Lamberto, and John A. Pojman, University of Southern Mississippi, Hattiesburg, MS 39406
The system of 1-butanol in water was studied by spin drop tensiometry. The experiments on the water/1-butanol system have permitted us to observe an unambiguous example of interfacial tension in a miscible system. Slow solubilization permited the observation of alcohol droplet. By applying the Vonnegut and modified Vonnegut methods we were able to determine the Effective Interfacial Tension (EIT). The EIT was estimated for different temperatures and at different rotation speeds. In the Vonnegut zone of the droplet shape the EIT remained constant. However, the modified Vonnegut method resulted in rather incoherent EIT values. A constant value for the EIT can be explained considering that the drop shrinks because the 1-butanol flows out into the water matrix while no significant amount of water flows in. In this case, droplet composition remains constant.
2:45 DYNAMIC INTERFACIAL TENSION BEHAVIOR OF NONAQUEOUS PHASE LIQUIDS IN AQUEOUS AMPHIPHILIC BLOCK COPOLYMER SOLUTIONS
Nicola Muratore*, Jola Marszalek, Rosie Parker, and John A. Pojman, University of Southern Mississippi, Hattiesburg, MS 39406
Hydrophobic contaminants like as petroleum-based products frequently enter to the subsurface forming a separated organic phase in the groudwater or nonaqueous phase liquid (NAPL) domains. Under normal condition, this phase is retained within soil pores by the capillary forces and represents a long-term source of aquifer contamination. Remediation technologies based on the use of surfactants by reducing the capillary forces between the organic and aqueous phases are the most promising technique for removal of NAPL from the subsurface. This approach (mobilization) is based on the ability of surfactants to mobilize or displace entrapped NAPL by lowering the interfacial tension. Such thermodynamic property is playing a fundamental role on the removal of NAPL by mobilization. Most of the studies have dealt this aspect under equilibrium condition whereas little attention has been directed to the measurement of interfacial tension under nonequilibrium conditions, i.e., in condition of the contaminants removal. Dynamic interfacial tension studies of organic contaminants in amphiphilic block copolymer solutions were done by using spinning drop technique.
3:00 THE MULTICENTERED INTEGRATED QUANTUM MECHANICAL TECHNIQUE FOR AB INITIO STUDIES OF EXTENDED PI STACKING INTERACTIONS
Brian W. Hopkins* and Gregory S. Tschumper, University of Mississippi, University, MS 38677
An improved, more general method for performing multicentered integrated QM/QM calculations is presented. The new approach allows the multicentered approximation to be extended to overlapping model systems, thereby removing a significant limitation of the original approach. The applicability of multicentered (MC) QM/QM computations to pi stacking interactions is demonstrated. The trimers of cyanogen and diacetylene are studied. Each trimer is studied at six geometries, for a total of 12 unique structures. The accuracy of the MC QM/QM approach is excellent. In all cases, MC QM/QM calculations reproduce CCSD(T) binding energies within 0.05 kcal/mol. In addition, the method has been applied to several configurations of the benzene trimer. The results for these small systems suggest that the relatively new MC QM/QM method may be a powerful tool in the study of extended pi systems such as nucleic acids.
3:30 DETERMINATION OF ANION MOBILITY IN A [H.sup.+] CONDUCTING ELECTROLYTE
Kyle F. Lott* and Jason Ritchie*, University of Mississippi, University, MS 38677
Proton conducting polymer electrolytes have important electrochemical applications in devices such as fuel cells and electrochromic displays. We have prepared polymer electrolytes from a mixture of our "MePEG polymer," (MePEGnO(C[H.sub.2])3Si[O.sub.3])[.sub.n], and a PEG-based acid, MePEG-nS[O.sub.3]H. These electrolytes display substantial anhydrous [H.sup.+] conductivities. Our hypothesis is that ionic mobilities in these systems depend on the volume fraction of PEG (Vf, PEG). Our goal is to understand the mechanism of ion transport in these PEG-based materials. In order to separate the contributions of anions and cations to the overall conductivity, we have prepared mixtures of our MePEG polymer and a redox hybrid polyether melt [Co(bipy)[.sub.3+2]](MePEGnS[O.sub.3]). (n=3, 7, 12, 17). In this mixture, we are able to separately measure the anion and cations' contributions to the overall ionic conductivity by electrochemically measuring the diffusion coefficient of the [Co.sub.2+/3+](bipy)[.sub.3], and then measuring the ionic conductivity of the mixture. The Nernst-Einstein equation is then applied to solve for the diffusion coefficient of the MePEGnS[O.sub.3] anion. We will present a dependence of the physical diffusion coefficient of the MePEGnS[O.sub.3] anions on the Vf, PEG of the mixture, and will discuss the transference number of [H.sup.+] cations in these polymer electrolytes.
3:45 A SYSTEMATIC ASSESMENT OF DENSITY FUNCTIONALS FOR THE STUDY OF HYDROGEN BONDING IN PEPTIDES USING INTEGRATED QUANTUM MECHANICAL METHODS
Julie Anderson* and Gregory S. Tschumper, University of Mississippi, University, MS 38677
Twenty-four (24) density functional methods have been systematically studied to assess which functional(s), if any, can outperform HF as the low-level method in integrated QM/QM calculations. In other words, this work addresses the question "How do MP2/DFT integrated techniques compare to MP2/HF when computing hydrogen bond strengths?". A careful comparison of dissociation energies (De) and substituent (S-) values for hydrogen bonding between water and the central polar side-chain of Gly-X-Gly tripeptides reveals some surprising results. While all 24 density functionals reproduce MP2 dissociation energies more reliably than the HF method, no MP2/DFT scheme offers substantial improvement over the MP2/HF approach. Further, even the worst MP2/DFT combinations outperform the best density functional methods.
4:00 FRONTAL POLYMERIZATION OF A THIOLACRYLATE SYSTEM WITH A PEROXIDE INITIATOR COMBINED WITH AMMONIUM CARBAMATE AND A MICROENCAPSULATED CROWN ETHER
Dawn Anderson*, Birsen Varisli, and John A. Pojman, University of Southern Mississippi, Hattiesburg, MS 39406
Thiols can copolymerize with acrylates via free-radical chain growth mechanism and a free-radical-step-growth mechanism. It is also possible to polymerize thiols and acrylates using an amine-catalyzed Michael addition reaction. We studied a system in which an ammonium carbamate becomes activated as a catalyst when a crown ether is released from microcapsules. We tested how this additional mechanism affects the frontal polymerization of 1,6 hexandiol diacrylate and a trithiol.
4:15 PREPARATION AND ANALYSIS OF INITIATORCORE POLYUREA MICROCAPSULES USING PENTAMINES AND DIAMINES AS SHELL COMPONENTS
Sammy Popwell*, Brian McFarland, and John A. Pojman, University of Southern Mississippi Hattiesburg, MS 39406 Frontal polymerization involves the conversion of monomer to polymer via a localized reaction zone, which propagates through an unreacted solution of monomer and initiator. The stability of free-radical initiators in frontal polymerization systems is investigated through microencapsulation of the initiator. A significant increase in the pot life of the frontal system has been observed. The capsules produced in this study contain a cumene hydroperoxide-core surrounded by a polyurea shell, and the capsule shell is formed via interfacial polymerization between an isocyanate and an amine. Amine functionality can be used to control the degree of crosslinking and subsequently the stability of the polymer shell. Our study now focuses on the effect of a varying amine functionality on capsule stability, using amines such as ethylene diamine and tetraethylene pentamine. Preliminary experiments suggest that the isocynate to primary amine ratio affects the stability of the polyurea shell. At the optimum isocyanate to primary amine ratios, for both systems, there is a significant decrease in the pot life of capsules in monomer solution compared to capsules prepared with tetramine. However, there was still an increase in pot life of these systems compared to systems containing unencapsulated initiator.
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|Publication:||Journal of the Mississippi Academy of Sciences|
|Date:||Jan 1, 2005|
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