Domain Motions in the Interpretation of Neutron Spin Echo Spectroscopy

by Nikolai Smolin

      Protein function often requires large-scale motion of functionally-important domains. An exciting new development in the experimental detection of functionally-important domain motions in proteins is the application of neutron spin-echo spectroscopy (NSE). Spin echo directly probes coherent (i.e., pair correlated) scattering on the 10-100 ns timescale. Recent work has demonstrated that domain motions in the tetrameric protein Alcohol Dehydrogenase (yADH) can be positively identified and characterized with this technique.

      Inspired by these results, we conducted theoretical calculations of the coherent time correlated neutron scattering from all-atomic molecular dynamics simulations data of the same protein. NSE allows the direct measurement of the intermediate scattering function and this way allows the direct comparison between simulation and experiment. The global translational and rotational diffusional components were decomposed and the internal dynamics of these functional domains characterized. The translational, rotational, and the internal effective diffusion constants were determined from the intermediate scattering function and the results compared with the NSE data.