title: Photocurrent from oriented membrane films containing acid-blue and acid-purple bacteriorhodopsin and its mutants.
abstract: This paper investigates the fast photocurrent components, B1 and B2, from oriented bacteriorhodopsin (BR) membrane films at low pH, under pulsed laser excitation. Adding chloride ion changes the acid-blue BR to its acid-purple form. In the presence of chloride, the acid-purple BR shows a positive B2 component in the same direction as that of BR at neutral pH, indicating a rapid intramolecular charge transfer. In the absence of chloride, the acid-blue BR shows only a negative B1 with multi-components, indicating a rapid charge separation process associated with retinal photoisomerization. The multi-components in B1 are possibly formed due to the heterogeneity of the acid-blue BR. In addition, BR mutants, D85N and D115N, at low pH and in the presence of chloride, generate the B2 component as well. The observation of chloride-dependent B2 component in various cases at low pH, is in favor of a possible transient chloride ion transfer, although the nature of the charge being transferred cannot be identified so far.
authors.affiliation: Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta 30332-0400, USA. jwang@chemistry.gatech.edu
authors.forename: J
authors.initials: J
authors.lastname: Wang
mesh_terms: D001436:Bacteriorhodopsins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D009154:Mutation
chemical_list: D001436:Bacteriorhodopsins