title: QM/MM Study of Substituent and Solvent Effects on the Excited State Dynamics of the Photoactive Yellow Protein Chromophore.
abstract: Substituent and solvent effects on the excited state dynamics of the Photoactive Yellow Protein chromophore are studied using the average solvent electrostatic potential from molecular dynamics (ASEP/MD) method. Four molecular models were considered: the ester and thioester derivatives of the p-coumaric acid anion and their methylated derivatives. We found that the solvent produces dramatic modifications on the free energy profile of the S1 state: 1) Two twisted structures that are minima in the gas phase could not be located in aqueous solution. 2) Conical intersections (CIs) associated with the rotation of the single bond adjacent to the phenyl group are found for the four derivatives in water solution but only for thio derivatives in the gas phase. 3) The relative stability of minima and CIs is reverted with respect to the gas phase values, affecting the prevalent de-excitation paths. As a consequence of these changes, three competitive de-excitation channels are open in aqueous solution: the fluorescence emission from a planar minimum on S1, the trans-cis photoisomerization through a CI that involves the rotation of the vinyl double bond, and the nonradiative, nonreactive, de-excitation through the CI associated with the rotation of the single bond adjacent to the phenyl group. In the gas phase, the minima are the structures with the lower energy, while in solution these are the conical intersections. In solution, the de-excitation prevalent path seems to be the photoisomerization for oxo compounds, while thio compounds return to the initial trans ground state without emission.
authors.affiliation: Área de Química Física, University of Extremadura , Avda. Elvas s/n, Edif. José Ma Viguera Lobo 3a planta, Badajoz, 06006 Spain.
authors.forename: Francisco F
authors.initials: FF
authors.lastname: García-Prieto
authors.affiliation: Área de Química Física, University of Extremadura , Avda. Elvas s/n, Edif. José Ma Viguera Lobo 3a planta, Badajoz, 06006 Spain.
authors.forename: Aurora
authors.initials: A
authors.lastname: Muñoz-Losa
authors.affiliation: Department of Chemistry-Ångström, The Theoretical Chemistry Programme, Uppsala University , Box 518, 751 20 Uppsala, Sweden.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Fdez Galván
authors.affiliation: Área de Química Física, University of Extremadura , Avda. Elvas s/n, Edif. José Ma Viguera Lobo 3a planta, Badajoz, 06006 Spain.
authors.forename: M Luz
authors.initials: ML
authors.lastname: Sánchez
authors.affiliation: Área de Química Física, University of Extremadura , Avda. Elvas s/n, Edif. José Ma Viguera Lobo 3a planta, Badajoz, 06006 Spain.
authors.forename: Manuel A
authors.initials: MA
authors.lastname: Aguilar
authors.affiliation: Área de Química Física, University of Extremadura , Avda. Elvas s/n, Edif. José Ma Viguera Lobo 3a planta, Badajoz, 06006 Spain.
authors.forename: M Elena
authors.identifier: http://orcid.org/0000-0002-5252-2893
authors.initials: ME
authors.lastname: Martín
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D005740:Gases / Q000737:chemistry; D056004:Molecular Dynamics Simulation; D020283:Photoreceptors, Microbial / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D011789:Quantum Theory; D012997:Solvents / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D005740:Gases; D020283:Photoreceptors, Microbial; D012997:Solvents; C050162:photoactive yellow protein, Bacteria; D014867:Water