Hydration Dynamics

Our interests here focus on the fundamental understanding of a long standing biological question---how water controls protein structure, dynamics and function. Understanding of protein-water interactions has far-reaching implications relating to protein plasticity and recognition, protein folding and aggregation, and enzyme catalysis. We have used the naturally occurring amino acid tryptophan as a local optical probe and characterized its photophysics and photochemistry in various environments. By measuring femtosecond-resolved Stokes shifts, we have developed a powerful method to construct its environmental response function. By placing tryptophan at desirable positions along the protein with site-directed mutation and using a tryptophan scan, we have extensively studied the hydration dynamics around protein surfaces, in protein crevices, at protein-DNA interfaces, and on membrane surfaces. The dynamic motion of these biological-water molecules is being elucidated on actual time scales and at atomic scale.