COMPUTATIONAL CHEMISTRY MODELS OF HYDROCARBON CHAINS TESTED.Computational chemistry is increasingly being used to model complex molecular systems to aid the development of new pharmaceuticals, chemicals, and materials. The ability of computational chemistry to contribute to these design efforts is dependent on the availability of experimental data to validate the modeling. Hydrocarbon rich systems, such as organic polymers, self-assembled monolayers 1. A film or layer one molecule thick formed at the interface between water and either oil or air by a substance such as a partially esterified fatty acid that contains both hydrophobic and hydrophilic groups in the same molecule. 2. A confluent sheet of cells, one cell deep, growing on a surface in a cell culture. bilayer /bi·lay·er/ (bi´la-er) a membrane consisting of two molecular layers. bi·lay·er (b ![]() l critical to cellular membranes, are, in principal, ideal systems for the application of computational chemistry models since the numbers of electrons are small and the force fields are simple. As part of an effort to provide validation data for the modeling of hydrocarbon rich systems, researchers at NIST have undertaken a systematic study of the microwave rotational spectra of substituted alkanes, such as 1-pentene, 1-hexene, 1-octene, and 1-dodecene. The spectra reveal a plethora of conformational isomers 1. Any of two or more substances that are composed of the same elements in the same proportions but differ in properties because of differences in the arrangement of atoms. 2. Any of two or more nuclei with the same mass number and atomic number that have different radioactive properties and can exist in any of several energy states for a measurable period of time. , differing solely by rotation about the C-C single bonds. Comparisons of the experimental data show significant discrepancies with computational chemistry models. The origin of these differences is being examined but most likely originates with the relatively poor quality of molecular-mechanics force fields. The researchers note that the ability to precisely control the conformational relaxation in the cold molecular beam may provide a tool to investigate the complex conformational reorientation required by a protein to fold.
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