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Title: Role of excited state solvent fluctuations on time-dependent fluorescence Stokes shift

We explore the connection between the solvation dynamics of a chromophore upon photon excitation and equilibrium fluctuations of the solvent. Using molecular dynamics simulations, fluorescence Stokes shift for the tryptophan in Staphylococcus nuclease was examined using both nonequilibrium calculations and linear response theory. When the perturbed and unperturbed surfaces exhibit different solvent equilibrium fluctuations, the linear response approach on the former surface shows agreement with the nonequilibrium process. This agreement is excellent when the perturbed surface exhibits Gaussian statistics and qualitative in the case of an isomerization induced non-Gaussian statistics. However, the linear response theory on the unperturbed surface breaks down even in the presence of Gaussian fluctuations. Experiments also provide evidence of the connection between the excited state solvent fluctuations and the total fluorescence shift. These observations indicate that the equilibrium statistics on the excited state surface characterize the relaxation dynamics of the fluorescence Stokes shift. Our studies specifically analyze the Gaussian fluctuations of the solvent in the complex protein environment and further confirm the role of solvent fluctuations on the excited state surface. The results are consistent with previous investigations, found in the literature, of solutes dissolved in liquids.
Authors:
;  [1]
  1. Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803 (United States)
Publication Date:
OSTI Identifier:
22493196
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 143; Journal Issue: 17; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; EQUILIBRIUM; EXCITATION; EXCITED STATES; FLUCTUATIONS; FLUORESCENCE; ISOMERIZATION; LIQUIDS; MOLECULAR DYNAMICS METHOD; PHOTONS; PROTEINS; SIMULATION; SOLUTES; SOLVATION; SOLVENTS; STAPHYLOCOCCUS; STATISTICS; SURFACES; TIME DEPENDENCE; TRYPTOPHAN