The tryptophan fluorescence spectrum in proteins depends sensitively on the local environment covering the range 308-355 nm. We have previously shown that the wavelength can be predicted from QM-MM simulations. One must sum over all charged atoms of the protein and solvent to find the electric potential different from the 5- to the 6-membered ring of the Trp. Recently, there is considerable interesting in how rapidly the solvent and protein environment responds to the suddent large dipole increase caused by excitation of Trp. We are modelling the dynamics of this shift with our QM-MM simulations to see why controversial, long relaxation times appear in some experiments.


Xu J, Toptygin D, Graver KJ, Albertini RA, Savtchenko RS, Meadow ND, Roseman S, Callis PR, Brand L, Knutson JR, "Ultrafast Fluorescence Dynamics of Tryptophan in theProteins Monellin and IIAGlc ." J. Am. Chem. Soc. 128 ASAP (2006)

Vivian JT, Callis PR, "Mechanisms of Tryptophan Fluorescence Shifts in Proteins." Biophys. J. 80 2093-2109 (2001)