Table of Contents
Laser Chemistry
Volume 19 (1999), Issue 1-4, Pages 179-185

Time-Resolved Step-Scan Ftir Investigations on the M1→M2 Transition in the Light-Driven Proton Pump Bacteriorhodopsin

Institut für Biophysik und Strahlenbiologie, Albert-Ludwigs-Universität Freiburg, Albertstr. 23, Freiburg D-79104, Germany

Received 6 April 1997

Copyright © 1999 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Using time-resolved step-scan FTIR spectroscopy, it has become possible to identify two different M states in the 5 to 300 μs time range, which clearly differ from the MN state. The identification has become possible by measuring a pure BR→KL difference spectrum at 100 ns, which can be used to correct for the contributions of this intermediate in the later difference spectra. The subtraction of the later corrected difference spectra thus represent L→M1, M2 difference spectra with varying relative amount of the two M states. The comparison of these spectra clearly reveals differences in the amide-II spectral range, and possibly also in the amide-I range. From these observations it can be concluded that the two M states do not differ in the chromophore structure but in the protein structure.