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"The traditional view has been that a protein passes through a series of fixed reactions to reach its folded state," said senior author Feng Gai, a Penn chemist. "Our work suggests quite strongly that folding is a far richer phenomenon. Like skiers, some proteins rocket down an energy gradient to their destination while others take their time, meandering indiscriminately."

Protein folding is fiendishly intricate, yet crucial to the chemistry of life – so much so that a small army of biologists and chemists has devoted itself to better understanding the process. Each of the body’s 20 amino acids, the building blocks of proteins, is habitually attracted or repulsed by water; it’s largely these affinities that drive the as-yet-unpredictable contorting of proteins into three-dimensional shapes within the aqueous environment of a cell.

Gai and his colleagues traced protein folding by zapping samples of 20-amino-acid proteins with a one-nanosecond laser, momentarily heating them enough to unfold the proteins completely. Using infrared spectroscopy, they then observed, nanosecond by nanosecond, how quickly the cohort of proteins refolded into biochemically stable, three-dimensional shapes. It turned out that the time to refold varied tremendously, offering powerful if indirect evidence that the proteins weren’t following a single, prescribed pathway from unfolded to folded after all.

Gai was joined on the PNAS paper by Cheng-Yen Huang, Yongjin Zhu and Jason W. Klemke of Penn’s Department of Chemistry and Zelleka Getahun and William F. DeGrado of the Department of Biochemistry and Biophysics in Penn’s School of Medicine. Their work was supported by Research Corporation, the University of Pennsylvania Research Foundation and the National Science Foundation.

http://www.sciencedaily.com/releases/2002/02/020227071809.htm

[ 27 February 2002: Message edited by: Moderator ]