Protein Structure and Hydration Probed by SANS and Osmotic Stress
Christopher B. Stanley 1*, Susan Krueger 2, V. Adrian Parsegian 3 and Donald C. Rau 3
1 Oak Ridge National Laboratory
2 NIST Center for Neutron Research
3 NICHD, National Institutes of Health
* To whom correspondence should be addressed. E-mail: stanleycb{at}ornl.gov.
Submitted on September 23, 2007
Revised on October 27, 2007
Accepted on 27 November 2007
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Abstract |
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Interactions governing protein folding, stability, recognition, and activity are mediated by hydration. Here, we use small-angle neutron scattering (SANS) coupled with osmotic stress to investigate the hydration of two proteins, lysozyme and guanylate kinase (GK), in the presence of solutes. By taking advantage of the neutron contrast variation that occurs upon addition of these solutes, the number of protein-associated (solute-excluded) water molecules can be estimated from both changes in the zero-angle scattering intensity and in the radius of gyration. Poly(ethylene glycol) exclusion varies with molecular weight. This sensitivity can be exploited to probe structural features such as the large internal GK cavity. For GK, SANS is complemented by isothermal titration calorimetry with osmotic stress to also measure hydration changes accompanying ligand binding. These results provide a framework for studying other biomolecular systems and assemblies using neutron scattering together with osmotic stress.
Key Words:
guanylate kinase, isothermal titration calorimetry, poly(ethylene glycol), preferential hydration, protein conformation, small-angle neutron scattering
