A Concerted Two-Step Activation of Photoinduced Electron-Transport Across Lipid Membrane

Matsuo, Taku; Itoh, Kengo; Takuma, Keisuke; Hashimoto, K.; Nagamura, Toshihiko

doi:10.1246/cl.1980.1009

Cited by 38 publications

(10 citation statements)

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“…A two-step photoactivation of electron transfer across the membrane was also assumed for theSystem 16 of Table 1,wherein asurfactant porphyrin, ZnC12TPyP +, served as a photosensitizer [63]. The presence of an intermediate electron carrier in membranes (vitamin Kl or derivatives of alloxazine) leads to a significant increase in the electron phototransfer rate.…”

Section: = ~Tkq + Ko~°kt + K~mentioning

confidence: 99%

“…Such an influence of the carriers, which are known to be the quenchers of the excited porphyrin, is explained in terms of the two-quantum mechanism of electron phototransfer activation involving the participation of electron carriers. According to the scheme suggested by Matsuo and his co-workers [63], the absorption of the light quantum on the outer side of the membrane results in the reduction of AQDS 2-and in the oxidation of ZnC~2TPyPo+,t by the reaction of the type (13). Absorption of the second light quantum on the inner surface leads to the formation of the triplet excited porphyrin and subsequent reduction of the electron carrier, C, embedded into the membrane:…”

Section: = ~Tkq + Ko~°kt + K~mentioning

confidence: 99%

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Photoinduced electron transfer across membranes

Lymar

Parmon

Zamaraev

1991

Topics in Current Chemistry

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Section: = ~Tkq + Ko~°kt + K~mentioning

confidence: 99%

Section: = ~Tkq + Ko~°kt + K~mentioning

confidence: 99%

Photoinduced electron transfer across membranes

Lymar

Parmon

Zamaraev

1991

Topics in Current Chemistry

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“…(i) In chlorophyll-containing liposomes, the photoreduction of Fe(CN)'-is reported to be enhanced by the addition of proton carriers (11). (ii) In Zn-porphyrin-containing vesicles, the photoreduction of 9, 10-anthraquinone 2,6-disulfonate is stimulated by the addition of electron mediators such as 1,3-dibutylalloxazine and 1,3-didodecylalloxazine (12). (iii) In chlorophyll-containing bilayer lipid membranes (13) or in cyanine dye-containing monolayer assemblies (14), vectorial electron transport across the lipid barrier is enhanced by applying transmembrane electric fields by means of electrodes.…”

mentioning

confidence: 99%

Photosensitized electron transport across lipid vesicle walls: Enhancement of quantum yield by ionophores and transmembrane potentials

Laane

Ford

Otvos

et al. 1981

Proc. Natl. Acad. Sci. U.S.A.

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The photosensitized reduction of heptylviologen in the bulk aqueous phase of phosphatidylcholine vesicles containing EDTA inside and a membrane-bound tris(2,2'-bipyridine)ruthenium(2+) derivative is enhanced by a factor of6.5 by the addition ofvalinomycin in the presence ofK+. A 3-fold stimulation by gramicidin and carbonyl cyanide m-chlorophenylhydrazone is observed. The results suggest that, under these conditions, the rate of photoinduced electron transfer across vesicle walls in the absence of ion carriers is limited by cotransport of cations. The rate of electron transfer across vesicle walls could be influenced further by generating transmembrane potentials with K+ gradients in the presence of valinomycin. When vesicles are made with transmembrane potentials, interior more negative, the quantum yield of heptylviologen reduction is doubled, and, conversely, when vesicles are made with transmembrane potentials, interior more positive, the quantum yield is decreased and approaches the value found in the absence of valinomycin.In recent years, light-induced electron-transfer processes have been extensively investigated with the aims of understanding the mechanism of natural photosynthesis and of designing artificial systems that will decompose water by sunlight to produce chemical energy in the form of H2 (1-3). A basic concept in the design of such systems is the use of dyes to photosensitize electron-transfer reactions that produce chemical species capable of oxidizing and reducing water. A major problem accompanying the dissociation of water by sunlight involves the back reactions of the intermediary redox species, whereby the potential energy of the photochemical process is degraded. One way to control the forward and backward reactions is to separate the photooxidized and photoreduced species by a phospholipid vesicle wall (4-9).As a model for studying photosensitized electron transfer across vesicle walls, we have used the system described earlier (9, 10). An amphiphilic Ru2+ complex incorporated in the membrane mediates vectorial electron transfer from EDTA trapped in the inner compartment of the vesicle suspension to heptylviologen added to the bulk aqueous phase. Recent evidence suggests that electron transfer through the vesicle wall can be accomplished by an electron-exchange mechanism between

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“…Photoinitiated electron transfer reactions in lipid membranes, both planar and vesicular, have been studied extensively and are becoming well characterized as a model for biological electron transfer (see Hong, 1976 for review; Ilani and Mauzerall, 1981;Liu and Mauzerall, 1985;Ford and Tollin, 1984;Woodle and Mauzerall, 1986;Woodle et al, 1987). Bilayer lipid membranes have also proved useful as an organized system for separation of aqueous reactants on either side with bilayer bound components mediating the reaction (see Fendler 1984 for review;Ford ef al., 1979;Krakover et al, 1981;Matsuo et al, 1980;Runquist and Loach, 1981;Tunuli and Fendler, 1981;Bienvenue et al, 1984;Ilani and Krakover, 1987). The photodependent processes can be either photoinitiated or photodriven.…”

Section: Introductionmentioning

confidence: 99%

Photoinduced Electron Transfer Across Lipid Bilayers Containing Magnesium Octaethylporphyrin

Ilani

Woodle

Mauzerall

1989

Photochem & Photobiology

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Both photoinitiated (thermodynamically downhill) and photodriven (thermodynamically uphill) electron transfer reactions across lipid bilayers are sensitized by magnesium octaethyl porphyrin (MgOEP). It is shown that the reaction mechanism is via reduction of photoexcited MgOEP at the reducing (ascorbate) side of the bilayer and the charge carrier is likely the neutral protonated MgOEP anion. The MgOEP cation (or its neutral form) does not contribute to charge passage across the bilayer even though it is readily formed at the acceptor (ferricyanide or methyl viologen) side of the membrane. Photoelectric measurements on planar bilayers show that the time constant for reduction of excited MgOEP is about 10 microseconds with 10 mM ascorbate. The membrane transport of the mediator appears to be rate limiting when the reaction is photoinitiated and the interfacial reaction appears to be limiting when the reaction is photodriven. The quantum yield of the process is about 0.1 in the latter case and about 0.02 in the former. The former yield is increased to about 0.15 in the presence of a redox mediator, duroquinone. In these systems, the magnesium porphyrin is both sensitizer and trans membrane redox mediator.

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A Concerted Two-Step Activation of Photoinduced Electron-Transport Across Lipid Membrane

Cited by 38 publications

References 8 publications

Photoinduced electron transfer across membranes

Photoinduced electron transfer across membranes

Photosensitized electron transport across lipid vesicle walls: Enhancement of quantum yield by ionophores and transmembrane potentials

Photoinduced Electron Transfer Across Lipid Bilayers Containing Magnesium Octaethylporphyrin

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