MOLECULAR RESPONSE OF CHICKEN EGG WHITE LYSOZYME TO BUFFER SALT CONCENTRATIONS AND pH John P Sumida1, Natalie Kirkland2, Marc Pusey3; 1Universities Space Research Association, 4950 Corporate Drive, Suite 100, Huntsville, Alabama 35805, 2University of Alabama, Huntsville, 3NASA/Marshall Space Flight Center Chicken egg white lysozyme, (CEWL), has been widely used as a model for the study of protein crystal growth. Protein crystal growth bears direct relevance to drug design and development in that the ability to produce better quality protein crystals results in more accurate structure determinations. Having more accurately defined drug targets results in more effective drug design. In order to produce high quality protein crystals, an understanding of the mechanisms involved in protein crystal growth is essential. The present study examines role of the solvent in protein nucleation, and specifically, the dependence of the rotational dynamics of CEWL on the salt concentration and pH. Using time resolved fluorescence anisotropy of fluorescently labelled lysozyme, the rotational lifetime is observed to increase to a maximum at specific salt concentrations. Increasing the pH, acts to shift the observed rotational maximum to a higher salt concentration. Also observed in this work is evidence suggestive of energy transfer between the fluorophore and Trp 63. The magnitude of the energy transfer also changes with both salt concentration and pH in a manner similar to the anisotropy changes. These observations suggest small changes in the protein conformation and hydrodynamic volume in response to the solvent environment.