Influence of Protein Environment on Tryptophan Fluorescence

Abstract

Tryptophan fluorescence is often used as a probe of protein structure. One example of this involved the study how a mutation in catechol O-methyltrasferase produces a less stable protein. Other examples of the use of tryptophan and what factors influence variations in emission energy and quantum yield are discussed. Further investigation of these factors was carried out using two simple peptide systems, followed by mixed molecular dynamics/quantum mechanics simulations to calculate the energetics of quenching by electron transfer. These simulations used a simple quantum model that allowed tight coupling between classical and quantum calculations. It also incorporates potentials from induced dipoles. These simulations resulted in a correlation of quantum yield and charge-transfer energies. Interactions between the charge acceptor and protein stabilized charge in one system, while the other was stabilized by interactions between water and both the charge donor and acceptor.