Exploring the Electrostatic Landscape of Proteins with
Tryptophan Fluorescence
Patrik Callis
Department of Chemistry and Biochemistry, Montana State University
The usefulness of Trp fluorescence in studying proteins stems from the sensitivity to the precise local environment of the fluorescence intensity, lifetime, and wavelength. In particular, it is the local electric field strength and direction that determine whether the fluorescence will be red or blue shifted and whether an electron acceptor will or will not quench the fluorescence. This seminar will describe how we combine molecular dynamics simulations with quantum chemical methods to uniquely predict electron transfer rates of processes that determine the fluorescence intensity. This construct reveals the enormous magnitude and short time scale of fluctuations in the local field, and provides the answer to the 40-year old puzzle of why the fluorescence quantum yields and lifetimes of Trp vary by ~100 fold in proteins while that of Trp itself is insensitive to solvent.