OXIDATION-REDUCTION REACTIONS OF P700 AND CYTOCHROME f IN FRACTION 1 PARTICLES PREPARED FROM SPINACH CHLOROPLASTS BY FRENCH PRESS TREATMENT

David (Dave) Charles Fork (1929-2020): a gentle human being, a great experimenter, and a passionate researcher

We provide here an overview of the remarkable life and outstanding research of David (Dave) Charles Fork (March 4, 1929-December 13, 2021) in oxygenic photosynthesis. In the words of the late Jack Edgar Myers, he was a top 'photosynthetiker'. His research dealt with novel findings on light absorption, excitation energy distribution, and redistribution among the two photosystems, electron transfer, and their relation to dynamic membrane change as affected by environmental changes, especially temperature. David was an attentive listener and a creative designer of experiments and instruments, and he was also great fun to work with. He is remembered here by his family, coworkers, and friends from around the world including Australia, France, Germany, Japan, Sweden, Israel, and USA.

The discovery and function of plastocyanin: A personal account

A brief autobiographical account is presented of the early research that led to the discovery of the copper protein plastocyanin and the identification of its function as an electron carrier in plant photosynthesis. A discussion follows of different approaches employed for the determination of the functional site of plastocyanin in relation to cytochrome f. A summary is provided of a heated controversy about the involvement of two or three light reactions in photosynthesis and an experiment is described that has contributed to resolution of the controversy through the identification of the functional site of plastocyanin. An early history of photosynthesis research in Japan is also discussed.

The kinetics and specificity of electron transfer from cytochromes and copper proteins to P700

The rates of electron transfer to P700 from plastocyanin and cytochrome f have been compared with those from three other c-type cytochromes and azurin, a copper protein resembling plastocyanin. Three different disruptive techniques were used to expose P700; digitonin, Triton X-100 and sonication. The following rate constants were measured at 25 degrees C, pH 7.0, with digitonin-treated chloroplasts: plastocyanin, 8 x 10(7)M(-1) x s(-1); red-algal cytochrome c-553, 1.9 x 10(7)M(-1) x s (-1); Pseudomonas cytochrome c-551, 8 x 10(6)M(-1) x s (-1); azurin, less than or = 3 x 10(5)M(-1) x s (-1); cytochrome f, less than or = 2 x 10(4)M(-1) x s (-1); mammalian cytochrome c, less than or = 2 x 10(4)M(-1) x s (-1). For electron transfer from plastocyanin, the effects of ionic strength, pH and temperature were also studied, and saturation effects found in earlier work were avoided by a full consideration of the various secondary reactions and inclusion of superoxide dismutase. The relative rates are discussed in relation to photosynthetic electron transport.