Affordable Access

Publisher Website

The photocycle of bacteriorhodopsin at high pH and ionic strength:I. Effects of pH and buffer on the absorption kinetics

Authors
Journal
Biochimica et Biophysica Acta (BBA) - Bioenergetics
0005-2728
Publisher
Elsevier
Publication Date
Volume
1319
Issue
1
Identifiers
DOI: 10.1016/s0005-2728(96)00116-8
Keywords
  • Bacteriorhodopsin
  • Ph
  • Photoselection
  • Anisotropy

Abstract

Abstract A fitting analysis resolved the kinetics in the microsecond to second time range of the absorption changes in the bacteriorhodopsin photocycle at pH=8.0–9.5 in 3 M KCl into seven exponential components. The time constants and/or amplitudes of all components are strongly pH-dependent. In the pH range studied, the logarithms of the pH-dependent time constants varied linearly with pH. The maximum absolute value of the corresponding slopes was 0.4, in contrast with the theoretically expected value of 1 for unidirectional reactions coupled directly to proton exchange with the bulk phase. This indicates that the extracted macroscopic rate constants are not identical to the microscopic rate constants for the elementary photocycle reaction steps. Unexpected differences were found in the kinetic parameters in CHES and borate buffers.

There are no comments yet on this publication. Be the first to share your thoughts.