Fast Stages of Photoelectric Processes in Biological Membranes

Abstract

Chromatophores of photosynthetic bacteria Rhodospirillum rubrum, Rhodopseudomonas .sphaeroides and Chromatium minutissimum were associated with a collodion film impregnated with a decane solution of asolectin. A very short light flash inducing a single turnover of the chromatophore photosynthetic redox system was found to induce the formation of an electric potential difference amounting to 60 mV, directed across the film as measured with an orthodox electrometer technique. The main phase of the photoelectric response had a z value of < 200 ns. Addition of menadione and some other redox mediators increases the main phase amplitude and induces a slower phase (z = 200 ps). In Ch. rninutissimurn chromatophores that retained their endogeneous cytochrome c pool, one more electrogenic phase was revealed (z = 20 ps). Redox titrations of the electric response and bacteriochlorophyll absorption at 430 nm as well as measurements of the kinetics of cytochrome c oxidation have indicated that the fastest electrogenic phase is due to electron transfer from bacteriochlorophyll to Feubiquinone, the 20-11s phase to cytochrome c2+ -bacteriochlorophyll oxidoreduction, and the 200-ps phase to Fe-ubiquinone-oxidation by a secondary quinone. In the decay of the photoelectric response, a 30-ms phase was identified which was explained by a reverse electron transfer from reduced Fe-ubiquinone to oxidited bacteriochlorophyll. The difference in the fast kinetics of photoelectric generation by the bacteriochlorophyll system from those by bacterial and animal rhodopsins has been discussed.

Photoelectric studies of the transmembrane charge transfer reactions in photosystem I pigment‐protein complexes

“…In the absence of soluble electron donors and acceptors, the kinetics of dark reduction of P700 + is characterized by back reactions from one of the bound acceptors [11]. The direct electrometrical method developed in our laboratory [8,9,17,18] was used to monitor the flash‐induced photoelectric responses of the proteoliposomes containing PS I complexes from the cyanobacterium Synechocystis sp. PCC 6803 adsorbed on the surface of a phospholipid‐impregnated collodion film.…”

“…However, because the kinetic phase with a time constant of ∼220 ns was obtained as a decay‐cleared trace rather than an actually measured kinetic curve, it was reasonable to use a direct electrometric method of detection of transmembrane electric potential difference (Δ ψ ) generation within the time range from 200 ns to ∼100 ms. The system based on phospholipid‐impregnated collodion film developed in our laboratory [8,9] seems to be well adapted for the measurement of photovoltage kinetics on the microsecond to millisecond time scale.…”

Electrogenic Protonation of the Secondary Quinone Acceptor QB in Spinach Photosystem II Complexes Incorporated into Lipid Vesicles

“…Generation of the transmembrane potential differ ence was recorded using a direct electrometric technique with resolution of 100 nsec as described in [23]. The tech nique includes an arrangement of specimens on the sur face of a collodion phospholipid impregnated film sepa rating two partitions of the measuring cell, and recording ∆Ψ with light protected Ag/AgCl macroelectrodes.…”

THE INWARD H+ PATHWAY IN BACTERIORHODOPSIN: THE ROLE OF M412 AND P(N)560 INTERMEDIATES*

“…1988; Kaulen et a/., 1990). For methods of measurements of spectral, pH, electric and light scattering responses, see Drachev et al (1981Drachev et al ( , 1984Drachev et al ( , 1986Drachev et al ( , 1987Drachev et al ( , 1989 and Danshina et al (1991). As a light source, a Quantel laser (532 nm, 30 mJ, t,,?…”