title: Photoinduced isomerization of the photoactive yellow protein (PYP) chromophore: interplay of two torsions, a HOOP mode and hydrogen bonding.
abstract: We report on a detailed theoretical analysis, based on extensive ab initio calculations at the CC2 level, of the S(1) potential energy surface (PES) of the photoactive yellow protein (PYP) chromophore. The chromophore's photoisomerization pathway is shown to be fairly complex, involving an intimate coupling between single-bond and double-bond torsions. Furthermore, these torsional modes are shown to couple to a third coordinate of hydrogen out-of-plane (HOOP) type whose role in the isomerization is here identified for the first time. In addition, it is demonstrated that hydrogen bonding at the phenolate moiety of the chromophore can hinder the single-bond torsion and thus facilitates double-bond isomerization. These results suggest that the interplay between intramolecular factors and H-bonding determines the isomerization in native PYP.
authors: Theoretische Chemie, Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany. evgeniy.gromov@pci.uni-heidelberg.de
authors: Evgeniy V
authors: EV
authors: Gromov
authors: Irene
authors: I
authors: Burghardt
authors: Horst
authors: H
authors: Köppel
authors: Lorenz S
authors: LS
authors: Cederbaum
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D020607:Halorhodospira halophila / Q000737:chemistry* / Q000378:metabolism; D006860:Hydrogen Bonding; D008027:Light; D008958:Models, Molecular; D055668:Photochemical Processes / Q000528:radiation effects; D020283:Photoreceptors, Microbial / Q000737:chemistry* / Q000378:metabolism; D013237:Stereoisomerism; D013816:Thermodynamics; D054159:Torsion, Mechanical
chemical_list: D001426:Bacterial Proteins; D020283:Photoreceptors, Microbial; C050162:photoactive yellow protein, Bacteria