CHANGES IN THE S0 AND S1 PROPERTIES DURING DARK-ADAPTATION IN OXYGEN-EVOLVING PHOTOSYSTEM-II-ENRICHED THYLAKOID MEMBRANES

Analysis of oxygen and fluorescence flash yield patterns reveal two types of period 4 behavior. Two types of oxygen-evolving center have been characterized, those with few misses which induce fluorescence oscillations (however, instead of misses a small proportion of active centers, about 10%, are lost after each flash of a series) and the others responsible for the highly damped oxygen-yield oscillations (Delrieu, M.J. and Rosengard, F. (1988) Biochim. Biophys. Acta, 936, 39-49). In this paper, further investigation of the fluorescence yield patterns shows that in the oxygen-evolving centers responsible for the period 4 fluorescence oscillations (and only in these centers), a change in the S0 and S1 properties develops during dark adaptation, affecting the S state advancement only on the first flash of a series. The miss factor (around 1-4%) was greatly increased on the first flash of a series for the S0 --> S1 and S1 --> S2 transitions (1) when the relatively high flash energy was decreased, (2) during the (short) dark period that followed one or three pre-flashes, (3) after partial Cl- or Ca2+ depletion. There are two possible explanations of the misses on the first flash only: (a) either after the first flash no reaction occurs in a percentage of S0 and S1 state centers and the miss factors are therefore alpha-0 and alpha-1, or (b) a reaction occurs after the first flash, and the reaction results in the formation of inactive S0, S1 and S2 state centers (the miss factors are then alpha-0, alpha-1 and alpha-2). The centers studied represent a minor fraction of the O2-evolving centers at an ambient temperature. In these centers, a structural reorganization in the S0 and S1 states during dark adaptation could account for misses. This process is generally reversed by one flash.