On the Determination of the 5-State Distribution in the Kok Model

Abstract

Abstract We use the Markow chain theory to analyze the oscillation pattern of oxygen evolution during water oxidation in photosystem II under short saturating light flashes. We propose a method based on the standard least square deviation (test X2) to determine the number of 5-states in the Kok model. As pointed out by Burda et al. (1995) this information is amongst others important for the interpretation of the role of calcium for oxygen evolution. A specific mathematical representation for a situation when the S4 state is longer living than generally assumed is introduced which requires an explicit extension of the Kok model to five states. The higher stability is modelled by introducing additional decay channels, e.g. a nonvanishing probability for the transition of S3 to the S0 state and a further transition probability for the transition from S3 to S4. Our analysis is extended to the case of damped oscillations of oxygen evolution caused, for example, by the lack of electron acceptor or the short life time of photosystem II particles.