Step-scan FT-IR difference spectroscopy with 100-ns time resolution is applied to the membrane protein bacteriorhodopsin. The experimetal setup and data acquisition are described in great detail. The IR absorbance changes accompanying bacteriorhodopsin's photocycle are presented in a three-dimensional representation. The data quality allows one, for example, to resolve the biphasic rise of the photocycle-intermediate M. A bacteriorhodopsin's proton pump model based on the FT-IR works is presented.
Robin Rammelsberg, Benedikt Hessling, Harald Chorongiewski, and Klaus Gerwert, "Molecular Reaction Mechanisms of Proteins Monitored by Nanosecond Step-Scan FT-IR Difference Spectroscopy," Appl. Spectrosc. 51, 558-562 (1997)