Hexane-solubilised reaction centre proteolipid complexes of Rhodopseudomonas sphaeroides

Photoelectric currents across planar bilayer membranes containing bacterial reaction centers. Response under conditions of single electron turnover

“…The dark reverse current of Fig. 3 A has a relaxation half-time of 60 ms. An identical half-time has been determined for the back reaction, Q, to (BChl)2*, in alkane-solubilized RC (15,22) and chromatophore membranes (26,27). The time-course of the back reaction from Q, can be also obtained from a study of the kinetics with which the (BChl)2 regain photocurrent activity between two light pulses.…”

“…Electron Transfer from (BChl)2 to Q,,. Spectroscopic measurements have shown that the addition of ubiquinone-10 to the membrane-forming solution results in an increased number of RC with a bound Q1, and a partial reconstitution of Q17-to-Q1I electron transfer (15,22,23).…”

“…In some experiments, the octane phase was centrifuged at 104,000 g for 45 min to pellet the RC-phospholipid. This second centrifugation step rids the preparation of any quinone dislodged from the RC during the extraction (15,22,23).…”

“…Spectrophotometric measurements have shown that the alkane-solubilized RC retain their characteristic spectral and photochemical properties (15,22,23). The extraction procedure, however, incurs a loss (-50%) of Q, binding.…”

“…Addition of ubiquinone-10 (Sigma Chemical Co., St. Louis, Mo.) to the membrane-forming solution, followed by brief sonication (5 s), reconstitutes Q, binding, and also serves to reconstitute partial Q,, binding (15,22,23). RC membranes were formed from either RC-phospholipid-octane solutions supplemented with ubiquinone-10 or from solutions without extra quinone.…”