1 Phenomenological Characterization of Bacteriorhodopsin – D 85 N Photocycle

An operational characterization of the molecular photocycle of a genetic variant of bacteriorhodopsin, BR–D85N, is presented. Steady-state bleach spectra and pump–probe absorbance data are obtained with thick hydrated films containing BR–D85N embedded in a gelatin host. Simple twoand three-state models are used to analyze the photocycle dynamics and extract relevant information such as pure-state absorption spectra, photochemical-transition quantum efficiencies, and thermal lifetimes of dominant states appearing in the photocycle, the knowledge of which should facilitate the analysis and design of optical applications based on this photochromic medium. The remarkable characteristics of this material and their implications from the viewpoint of optical data storage and processing are discussed.