TECHNOLOGY |
Single-molecule protein-folding kinetics A technique that makes it possible to observe and measure the folding kinetics of proteins far from equilibrium, where partially folded protein conformations exist only briefly, has been developed by Everett A. Lipman, Benjamin Schuler, and William A. Eaton of the Laboratory of Chemical Physics at the National Institute of Diabetes & Digestive & Kidney Diseases and Olgica Bakajin of Lawrence Livermore National Laboratory [Science, 301, 1233 (2003)]. It is based on Förster resonance energy transfer (FRET), an approach applicable to single molecules in which the probability of energy transfer between two chromophores is used to determine their separation. The new technique represents a nontrivial combining of two others--one developed by Shimon Weiss of the University of California, Los Angeles, and coworkers in which FRET is observed as molecules diffuse freely through a laser beam, and a micromixing technique similar to one devised by Robert H. Austin of Princeton University and coworkers. The free-diffusion technique alone could be used only to examine states substantially populated at equilibrium, but the combined technique can now be used to measure FRET of dye-labeled proteins at arbitrary times subsequent to the triggering of folding. |
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