title: Excitation energies of a water-bridged twisted retinal structure in the bacteriorhodopsin proton pump: a theoretical investigation.
abstract: The first proton transfer in the bacteriorhodopsin photocycle takes place during the L → M transition. Structural details of the pre proton transfer L intermediate have been investigated using experiments and computations. Here, we assess L-state structural models by performing hybrid quantum mechanical/molecular mechanical molecular dynamics and excitation energy calculations. The computations suggest that a water-bridged twisted retinal structure gives the closest agreement with the experimental L/bR shift in the excitation energy.
authors.affiliation: Karlsruhe Institute of Technology, Institute of Physical Chemistry, Karlsruhe, Germany.
authors.forename: Tino
authors.initials: T
authors.lastname: Wolter
authors.forename: Kai
authors.initials: K
authors.lastname: Welke
authors.forename: Prasad
authors.initials: P
authors.lastname: Phatak
authors.forename: Ana-Nicoleta
authors.initials: AN
authors.lastname: Bondar
authors.forename: Marcus
authors.initials: M
authors.lastname: Elstner
mesh_terms: D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000378:metabolism; D056004:Molecular Dynamics Simulation; D017434:Protein Structure, Tertiary; D011522:Protons; D011789:Quantum Theory; D012545:Schiff Bases / Q000737:chemistry; D013696:Temperature; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D011522:Protons; D012545:Schiff Bases; D014867:Water; D001436:Bacteriorhodopsins