QUASIELASTIC NEUTRON SCATTERING PROBES PROTEIN DYNAMICS.

The function of a protein depends critically on its ability to adopt a specific structure. Remarkably a protein can fold efficiently to this native state from the unfolded states on physiological time scales. Understanding how this process occurs is one of the great challenges in biology. Proteins can also form collapsed, partially folded states. Such partially folded proteins resemble the intermediate states along the protein folding pathway and play important roles in understanding the mechanisms of protein folding.

To understand the changes in protein dynamics that occur in the final stages of folding, scientists at NIST have used quasielastic neutron scattering to probe the differences in the dynamics between the native state and the almost completely folded, molten globule state of the protein bovine a-lactalbumin. The results, show that the side-chain protons in the molten globules are significantly more mobile than those in the native protein. Moreover, the length scale of the motion, information that is uniquely provided by neutron, spectroscopic techniques, is substantially longer in the molten globule state compared to that in the more compact native state.