Molecular dynamics simulations and neutron scattering yield new insight into protein dynamics. (News Briefs).

Understanding the process by which a protein efficiently folds to the physiologically active native state is one of the great challenges in biology. Proteins can also form stable, partially folded states that are thought to resemble intermediate states along the protein folding pathway. Recently, a collaboration between the University of Pennsylvania, the University of California at Irvine, and NIST have used molecular dynamics simulations and quasielastic neutron scattering techniques to elucidate dynamic changes in the protein alpha-lactalbumin for the native state and the partially folded molten globule state.

Molecular dynamics simulations are the ideal complement to neutron scattering because neutrons measure correlation functions that are based on the positions of the atoms as a function of time. For the case of alpha-lactalbumin, the neutron results show that the side-chain protons in the molten globules are significantly more mobile than those in the native protein. Molecular dynamics results, which reproduce the measured quasielastic neutron spectra extremely well, show that the observed dynamic changes arise primarily from the particular region of the protein that forms a beta sheet in the native state and unfolds to a random coil in the molten globule. Thus the spectroscopic results clearly reflect the formation of secondary structures that occur as a protein folds. Moreover, the techniques developed for the comparison of molecular dynamics simulations with neutron spectra are directly applicable to a wide variety of complex materials.

CONTACT: Dan Neumann, [phone]; [e-mail] or Mounir Tarek, [phone]; [e-mail]; or Zimei Bu, [phone]; [e-mail].