Water dynamics near a prototypical hydrophobic amino acid surface: Experiment and theory

PHYS 455

Cecile Malardier-Jugroot, cmalardier-jugroot@lbl.gov1, Margaret Johnson1, Daniela Russo2, and Teresa Head-Gordon, TLHead-Gordon@lbl.gov1. (1) Department of Bioengineering, University of California, Berkeley, Berkeley, CA 94720, (2) ILL, France, Grenoble, France
Synthesis of tailor-made biomaterials requires a detailed understanding of the effect of solvent on structure, stability, and dynamics of self-assembly. Understanding solvent environmental influences may lead to the ability to exploit not only differences in monomer composition but solvent composition, to create polymers with desired properties. Our approach focuses on a precise study of successive hydration layers around a prototypical hydrophobic amino acid, N-acetyl-leucine-methylamide (NALMA). This invokes the zeroth-order model of a polymer in solution as an effective local monomer concentration, allowing us to characterize the structure and dynamics of hydration layers. We report on quasi-elastic neutron scattering measurements over a large range of timescales, and supporting molecular dynamics simulations, of the water dynamics for a 1M NALMA solution over a temperature range of 248-310K. We show that the very suppressed and non-Arrhenius translational dynamics of the water molecules actually resolve into two slightly non-Arrhenius diffusional timescales- one for long-lived water bound to the hydrophilic region of the peptide surface, and the other faster component (but still suppressed relative to bulk) due to more fluctional water structure around the hydrophobic side chain. We also discuss the analogies of the hydration dynamics of our peptide model system to water under confinement, in protein glasses, and water when supercooled.

Poster Session
7:30 PM-10:00 PM, Wednesday, 13 September 2006 Moscone Center -- Hall D, Poster

Division of Physical Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006