DERIVING REACTION-MECHANISMS FROM KINETIC SPECTROSCOPY - APPLICATION TO LATE RHODOPSIN INTERMEDIATES

A general algebraic approach to the kinetic analysis of time-dependent absorption data is presented that allows the calculation of possible kinetic schemes. The kinetic matrices of all possible reaction mechani sms are calculated from experimental eigenvalues and eigenvectors deri ved from the decay constants and amplitude spectra (b-spectra) of the global exponential fit to the time-dependence of the absorption data. The eigenvalues are directly related to the decay constants, and the e igenvectors are obtained by decomposing the b-spectra into spectral co mponents representing the intermediates, The analysis method is applie d to the late intermediates (lumi, meta I, meta-380, and meta II) of t he rhodopsin photoreaction. The b-spectra are decomposed into lumi, me ta I, meta-380, and rhodopsin spectra, The meta-380 component is parti tioned into isospectral meta I-380 and meta II components based on phy sical criteria, The calculated kinetic matrices yield a number of reac tion mechanisms (linear scheme with back reactions, branched schemes w ith equilibrium steps, and a variety of square models) consistent with the photolysis data at 25 degrees C, The problems associated with iso spectral intermediates (meta I-380 and meta II) are treated successful ly with this method.