Oxygen evolution by Photosystem II: The contribution of backward transitions to the anomalous behaviour of double-hits revealed by a new analysis method |
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Authors: | Pascal C. Meunier |
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Affiliation: | (1) Department of Biochemistry, University of Cambridge, Tennis Court Road, CB2 1QW Cambridge, UK;(2) Present address: Department of Biological Sciences, Purdue University, Lilly Hall of Life Sciences, 47907 West Lafayette, IN, USA |
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Abstract: | Backward transitions in the analysis of oxygen production under flashing light were introduced by Packham et al., 1988, Photosynth. Res. 15: 221–232. In order to take backward transitions into account, a new method of analysis is presented: the eigenvalue method. This method is based on the recurrence relation of oxygen production with four coefficients (also known as the four sigma coefficients). It shows less susceptibility to round-off errors than other methods and permits the computation of double-hits directly from the coefficients, which was not possible before. With it we discovered that the inconsistent behaviour of double-hits observed previously under low flash intensities or low flash frequencies was mainly due to the inclusion of the backward transitions into the double-hit probability. In these conditions backward transitions seemed to be due either to the combination of an S-state deactivation and a miss, or to two S-state deactivations and a single-hit.In the presence of 3-(3, 4-Dichlorophenyl)-1, 1-dimethylurea (DCMU), the previous methods of sigma analysis failed. In contrast, the new method resolved all four S-state probabilities; thus it has the further advantage of being more robust (robustness being defined as the ability to yield a meaningful answer under difficult conditions).Abbreviation: DCMU 3-(3, 4-Dichlorophenyl)-1, 1-dimethylurea |
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Keywords: | Photosystem II S-states oxygen evolution probabilities flashing light |
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