Comment on “An Apparent General Solution for the Kinetic Models of the Bacteriorhodopsin Photocycles”

Richard Hendler has presented a detailed comparison of reversible homogeneous models (RHM) and unidirectional parallel models (UPM) for the bacteriorhodopsin photocycle1 using data from his own laboratory2 and the data of Xie et al.3 He makes an apparently valid criticism of the analysis of the latter data as fitted to an RHM model (K T L T M1 T M2 T N T O f bR) by van Stokkum and Lozier4 that we will discuss in the next paragraph. Unfortunately, he fails to appreciate that the polarization of measuring and actinic beams must be properly set to avoid kinetics of physical motions of the excited and unexcited chromophores admixing with the absorption changes due to the photochemical cycle, as has been shown by many authors,5-12 and thus his own analysis is seriously flawed. This will be discussed in turn below. First, we will discuss Hendler’s criticism of van Stokku