Maze-like ratchet sorts biomolecules.Small particles, such as proteins or dust specks suspended in a liquid, perform an erratic dance called Brownian motion Brownian motion Any of various physical phenomena in which some quantity is constantly undergoing small, random fluctuations. It was named for Robert Brown, who was investigating the fertilization process of flowers in 1827 when he noticed a “rapid oscillatory . Liquid molecules induce the motion by bombarding Bombarding is the process of 'pumping' a Cold Cathode Lighting tube (otherwise called Neon Signs). Information A detailed process of bombarding can be found here, Bombarding. the particles randomly, jolting them first one way, then another. Now, a new device that transforms that jitterbugging into a graceful two-step promises to aid the study of certain biological molecules, researchers report. The device is a novel type of Brownian ratchet The Brownian ratchet is a thought experiment about an apparent perpetual motion machine postulated by Richard Feynman in a physics lecture at the California Institute of Technology on May 11, 1962 as an illustration of the laws of thermodynamics. , a tiny machine that harnesses the energy of random jiggles to produce a one-way particle flow. Although a Brownian ratchet powered only by erratic particle motion violates the second law of thermodynamics Noun 1. second law of thermodynamics - a law stating that mechanical work can be derived from a body only when that body interacts with another at a lower temperature; any spontaneous process results in an increase of entropy , researchers have come up with workable ratchets in recent years that use oscillating os·cil·late intr.v. os·cil·lat·ed, os·cil·lat·ing, os·cil·lates 1. To swing back and forth with a steady, uninterrupted rhythm. 2. electric fields. The result is linear particle flow parallel to the applied field (SN: 5/10/97, p. 285). Taking a step into a new dimension, Alexander van Oudenaarden and Steven G. Boxer of Stanford University Stanford University, at Stanford, Calif.; coeducational; chartered 1885, opened 1891 as Leland Stanford Junior Univ. (still the legal name). The original campus was designed by Frederick Law Olmsted. David Starr Jordan was its first president. have now built the first working version of a ratchet that directs particles to fan out across a plane. The device separates them into streams whose trajectories differ depending on how readily the particles diffuse and the strength of their electric charges. The researchers describe the device in the Aug. 13 SCIENCE. The new ratchet will ease the sorting of hard-to-separate cell-membrane proteins, such as receptors, the scientists predict. "Membrane proteins are notoriously difficult to work with but extremely important," especially in drug development, Boxer says. In their invention, the experimenters employed semiconductor-processing methods to erect a maze of microscopic titanium-oxide barriers on a glass base. The shape and placement of the 25-nanometer-high barriers enable Brownian motion to nudge nudge 1 tr.v. nudged, nudg·ing, nudg·es 1. To push against gently, especially in order to gain attention or give a signal. 2. the proteins along in one direction, while a constant electric field gently pushes them along a perpendicular course. Boxer explains that drug designers might use the ratchet to determine whether molecules of a candidate drug have docked with target receptors on a membrane. If the molecules have bonded, the stream bearing the particular receptor would dry up and a new stream containing the drug-receptor complex would appear. |
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