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42734-G4
Ultrafast Hydration Dynamics at Protein Surfaces

Dongping Zhong, Ohio State University

The project, hydration dynamics at protein surfaces, was supported by PRF from July, 2005. With the support in two years, we have established a novel method to measure protein hydration dynamics, a central problem to protein science. Integrating molecular biological mutation methods and femtosecond spectroscopy, we designed and screened more than thirty mutants of apomyoglobin and measured water relaxation dynamics for these mutants with femtosecond resolution and single-residue resolution. We observed a robust biphasic distribution of water relaxation: One is in a few picoseconds and the other one is in tens to hundreds of picoseconds. With molecular dynamics simulations, the dynamics in a few picoseconds results from initial water collective local relaxation, mainly reorientation motion. The second relaxation on the longer time scale is from local rearrangement of water hydrogen-bond network, mediated by local protein fluctuations. This longer motion is important and relevant to biological activity. These findings are significant and are critical to the understanding of hydration role and protein flexibility, an essential determinant in protein function. These studies, joined with other supports, have led to a series of publications and clearly the support by PRF is crucial. With further support from PRF, we can understand the role of hydration dynamics on protein structure, stability, dynamics and function.

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