Structural and Dynamical Examination of the Low Temperature Glass Transition in Serum Albumin
Yanina A. Goddard 1, Jean-Pierre Korb 2 and Robert G. Bryant 1*
1 University of Virginia
2 Ecole Polytechnique
* To whom correspondence should be addressed. E-mail: rgb4g{at}virginia.edu.
Submitted on May 26, 2006
Revised on July 21, 2006
Accepted on 16 August 2006
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Abstract |
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The nuclear magnetic transverse decay and the proton second moment of bovine serum albumin samples dry and hydrated with different water isotope compositions show that at temperatures around 170 K, there is a dramatic change in the dynamics of the water associated with the protein interface. By comparison observation of the protein protons when hydrated with deuterium oxide provides no evidence for significant dynamical changes near 170 K. The proton second moment of the hydrated protein shows that the protein structure becomes more open with increasing hydration from the lyophilized condition and that the side chains extend from the protein surface into the solvent in the hydrated but not the dry cases. The proton second moment of serum albumin hydrated with H2O increases dramatically with decreasing temperature near 170K demonstrating that the water forms a rigid solid around the protein that effectively fills the surface irregularities created by the protein fold. Solvation with dimethyl sulfoxide yields small effects compared with water.
Key Words:
dynamical transition, protein hydration, second moment, solid-state NMR, spin relaxation, water dynamics
