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Deep ultraviolet initiated excited state dynamics of riboflavin and flavin mononucleotide
Author(s) -
Ghosh Sudeb,
Puranik Mrinalini
Publication year - 2018
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.5428
Subject(s) - flavin mononucleotide , photoexcitation , excited state , chemistry , flavin group , solvation , raman spectroscopy , resonance raman spectroscopy , excitation , resonance (particle physics) , molecular physics , atomic physics , photochemistry , molecule , optics , physics , biochemistry , enzyme , organic chemistry , quantum mechanics
Abstract Flavins are cofactors in several light‐activated enzymes and therefore their excited states are found to involve in many photobiological processes. Excited state dynamics of flavin compounds corresponding to their first singlet state (S 1 ) has been studied using a plethora of techniques, whereas studies related to highly absorbing ultraviolet excited states are lacking. Here, we study the ultrafast excited state dynamics of riboflavin and flavin mononucleotide using resonance Raman intensity analysis upon photoexcitation into their most intense absorption band centered at 266 nm. Resonance Raman cross sections of each flavin band are quantitatively measured across the 266‐nm absorption band (257–280 nm), and Raman excitation profiles are constructed. We have used Lee and Heller's time‐dependent wave packet theory to simulate the experimental Raman cross sections in a self‐consistent manner. The simulation results in instantaneous structural changes along with solvation dynamics, through linewidth broadening within tens of femtoseconds following photoexcitation. Major structural changes were observed through contraction and elongation of several ring stretching coordinates, affecting at a different site when compared with the S 1 excitation. The value of the total reorganization energy was determined to be 1,665 cm −1 (and 1,602 cm −1 for flavin mononucleotide) with a contribution of 1,310 cm −1 from the inertial response of water. We find upon excitation, the first solvation shell inertially responds with an ultrafast timescale of <30 fs for both the molecules. Our results can be useful to determine the structure and dynamics of flavoenzymes by using flavin as a probe following excitation within their 266‐nm absorption band.