Excited State Electron Distribution and Role of the Terminal Amine in Acidic and Basic Tryptophan Dipeptide Fluorescence.

ABSTRACT: The results of quantum yield (QY) study of tryptophanyl glutamate (Trp-Glu), tryptophanyl lysine (Trp-Lys) and lysinyl tryptophan (Lys-Trp) dipeptides over the pH range, 1.5 - 13, show that the charge state of the N-terminal amine, and not the nominal molecular charge determines the QY. When the terminal amine is protonated, QY is low (10^-2) for all three dipeptides. As the terminal amine cation is found proximal to the indole ring in Trp-Glu and Trp-Lys conformers but not in those for Lys-Trp, its effect may lie only in the partitioning of energy between nonradiative processes, not on QY reduction. QY is also low when both the N-terminal amine and indole amine are deprotonated. These two low QY states can be distinguished by fluorescence lifetime measurement. Molecular dynamics

SUBMITTER: Eisenberg AS 

PROVIDER: S-EPMC4852485 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature