| Abstract: | Abstract— Photochemical reaction centers from Rhodopseudomonas spheroides were subjected to pressures ranging from 1 to 6000 atm. Optical absorption, fluorescence and photochemical activities were studied under these conditions. Absorption spectra showed bathychromic shifts of the long-wave bands attributed to bacteriopheophytin and bacteriochlorophyll (the latter as P800 and P870). The quantum efficiency of photochemical oxidation of P870 was diminished at high pressure. The quantum yield of P870 fluorescence showed a parallel decline, as if high pressure introduced a quenching process that competed with both photochemistry and fluorescence. The original efficiencies were largely restored when the pressure was returned to 1 atm. The efficiency of oxidation of mammalian cytochrome c, coupled to the photochemical oxidation of P870 in reaction centers, was lowered by high pressure. This effect was more pronounced than the effect on P870 oxidation, and was irreversible. The kinetics of recovery of P870 following its photochemical oxidation showed effects of high pressure. The main effect was the appearance, at high pressure, of slow recovery suggesting the trapping of electrons. This effect was partly irreversible. |
