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Electronic structure of the photoactive yellow protein chromophore: Ab initio study of the low-lying excited singlet states

Paper ID Volume ID Publish Year Pages File Format Full-Text
28090 44059 2007 17 PDF Available
Title
Electronic structure of the photoactive yellow protein chromophore: Ab initio study of the low-lying excited singlet states
Abstract

The excited electronic states of the p-coumaric acid thio-ester chromophore of the Photoactive Yellow Protein (PYP) are characterized in view of identifying the key factors determining the chromophore's isomerisation. These factors include the anionic nature of the chromophore, the presence of sulfur (rather than oxygen or nitrogen) in the ester moiety, and the presence of a hydrogen-bonding environment stabilizing the phenolate moiety. Two twisted stationary S1 structures are identified, corresponding to a twist around the double bond conjugated with the aromatic ring, and the single bond adjacent to the ring, respectively. The latter structure is accessed directly by relaxation from the Franck–Condon (FC) geometry. These structures are shown to entail a substantial polarization effect (increasing charge separation when moving towards the twisted geometry). Further, an inversion of charge character is observed for the double-bond twisted minimum, which can be accounted for by the vicinity of an S1–S0 conical intersection. The S1–S0 gap at the minimum geometries depends in a sensitive fashion on the α-carbonyl heteroatom. Based upon these observations for the intrinsic properties of the chromophore, we further address the effect of the Arg52 residue, which acts as a counter-ion in the native protein environment.

Keywords
PYP; PYP chromophore; Excited states; cis–trans isomerisation; CC2 method; EOM-CCSD method; Conical intersection; Polarization; Effects of the protein environment
First Page Preview
Electronic structure of the photoactive yellow protein chromophore: Ab initio study of the low-lying excited singlet states
Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 190, Issues 2–3, 15 August 2007, Pages 241–257
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering