Effects of hydrostatic pressure on the kinetics of electron transfer in an isolated system of chloroplast cytochrome bf complex, plastocyanin and P700.

The effects of pressure on the kinetics of redox reactions in and around the chloroplast cytochrome bf complex were studied using a reconstituted system consisting of Photosystem I (PS I) particles, cytochrome bf complex and plastocyanin (PC), all derived from pea chloroplasts. There were no significant permanent effects of pressure in the range 0.1–191 MPa on the reaction kinetics, or on the shape of the absorption spectra of components studied. Discernable effects on rate-coefficients of increasing pressure were observed on the reduction of P700+ by PCI, on the reduction of PCII by ascorbate, and on the oxidation of decyl plastoquinol by the bf complex. The volumes of activation ΔV# were determined from the dependence of the rate-coefficient on pressure using: