Mapping hydration dynamics around a protein surface

Departments of Physics, Chemistry, and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, 191 West Woodruff Avenue, Ohio State University, Columbus, OH 43210

Edited by Ahmed H. Zewail, California Institute of Technology, Pasadena, CA, and approved October 3, 2007 (received for review August 13, 2007)

Abstract

Protein surface hydration is fundamental to its structure and activity. We report here the direct mapping of global hydration dynamics around a protein in its native and molten globular states, using a tryptophan scan by site-specific mutations. With 16 tryptophan mutants and in 29 different positions and states, we observed two robust, distinct water dynamics in the hydration layer on a few (≈1–8 ps) and tens to hundreds of picoseconds (≈20–200 ps), representing the initial local relaxation and subsequent collective network restructuring, respectively. Both time scales are strongly correlated with protein's structural and chemical properties. These results reveal the intimate relationship between hydration dynamics and protein fluctuations and such biologically relevant water–protein interactions fluctuate on picosecond time scales.

Footnotes

*To whom correspondence should be addressed. E–mail: dongping{at}mps.ohio-state.edu
Author contributions: L.Z., L.W., Y.-T.K., W.Q., Y.Y., O.O., and D.Z. performed research; L.Z. analyzed data; and L.Z. and D.Z. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0707647104/DC1.
Abbreviation:

apoMb,

apomyoglobin.
Freely available online through the PNAS open access option.