SITE‐SELECTION SPECTROSCOPY OF CHLOROPHYLL <i>b</i> IN MEMBRANES OF LECITHIN VESICLES AND IN OTHER SOLVENTS

Fünfschilling, J.; Walz, D.

doi:10.1111/j.1751-1097.1983.tb03356.x

Cited by 18 publications

(4 citation statements)

References 18 publications

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“…It was suggested that Chl molecules are located just below the membrane surface [213]. The spectroscopic and fluorescence data point to the polar environment of Chl tetrapyrrol macroring rather than to its direct contact with the aqueous phase [214,215]. Most likely this polar environment is formed by the domains of the ester groups of lecithin molecules.…”

Section: Chlorophyll-containing Membranesmentioning

confidence: 95%

Photoinduced electron transfer across membranes

Lymar

Parmon

Zamaraev

1991

Topics in Current Chemistry

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Section: Chlorophyll-containing Membranesmentioning

confidence: 95%

Photoinduced electron transfer across membranes

Lymar

Parmon

Zamaraev

1991

Topics in Current Chemistry

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“…A possible explanation for the increasing kqm-values above n = 4 is that the average positions of the bipyridinium rings of the viologens become increasingly closer to the interior of the membrane with increasing n from n = 5 to 8. This change in location would bring the electron-accepting parts of the molecules closer to the chlorin rings of the Chl molecules, which are probably oriented with the rings located close to the membrane-water interface, but folded back towards the interior of the membrane (Oettmeier et al, 1976;Funfschilling et al, 1983;Ford and Tollin, 1984). The great sensitivity of electron transfer reactions to the distance between the donor and acceptor (Miller et al, 1982) could then account for the 20-fold increase in k," of octyl viologen relative to that of methyl, ethyl, propyl, and butyl viologens.…”

Section: Triplet Quenchingmentioning

confidence: 99%

Chlorophyll Photosensitized Electron Transfer in Phospholipid Bilayer Vesicle Systems: Correlations Between Kinetic Parameters and Solubilities of Viologen Acceptors *

Ford

Tollin

1986

Photochem & Photobiology

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Abstract— Twelve viologens (quaternary 4,4′‐bipyridinium ions) are investigated as electron acceptors in vesicle suspensions containing chlorophyll‐a (Chl) using laser flash photolysis. The structures of the viologens, which determine how they and their reduced radicals partition between the water and bilayer membrane phases, are systematically varied in order to probe the effects of acceptor solubility on the kinetics of photosensitized electron transfer reactions. The effectiveness of the viologens as quenchers of the Chl triplet excited state increases as they become less soluble in water, because the viologens are more likely to be incorporated into the membrane, but the efficiency of radical formation decreases and the rate of the reverse electron transfer reaction increases. The data obtained with a homologous series of di‐alkyl viologens are analyzed quantitatively using a kinetic model which includes the partition coefficients of the viologens and their radicals. For the most part, the reactivities of the viologen species are proportional to their concentrations in the membrane phase, but the locations and mobilities of the viologens in the membrane phase also have to be considered. In order for the Chl and viologen radicals to separate efficiently. the viologen radical has to be able to diffuse from the membrane to the water phase at a rate that competes effectively with reverse electron transfer within the radical pair complex (> 105 s−1).

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“…This agrees with the expectation that the porphyrin cation is held in a rather narrow energetic well in the polar region of the bilayer. Both energy calculations (Brasseur et al, 1984) and site selection spectroscopy (Funfschilling and Walz, 1983) place the ring of chl a in the polar region of the bilayer. The variable Ameasures the probability that a donor species is at the closest distance to P+, and should be proportional to the added donor concentration since no saturation is observed (see below).…”

Section: Decay Of Photovoltage As a Function Of Ferricyanide And Ferrmentioning

confidence: 99%

Distributed kinetics of decay of the photovoltage at the lipid bilayer-water interface

Liu¹,

Mauzerall²

1985

Biophysical Journal

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The decay kinetics of the photovoltage formed on pulsed illumination of a chlorophyll a- (chl a-) containing lecithin-bilayer adjacent to a ferricyanide solution on one side show characteristics of a system with distributed rate constants, i.e., the decay approaches linearity in log of time. The kinetics can be explained by a distribution of the chl cation over a few angstroms depth in the interfacial region of the bilayer and a rate constant exponentially dependent on distance as expected from tunneling theory. Addition of the donor ferrocyanide both increases the average rate and sharpens the distribution. There is a competitive inhibition by ferricyanide of the reaction of pigment cation with ferrocyanide. Removal of oxygen increases the rate of decay when an acceptor, methyl viologen or anthraquinone-2-sulfonate, forms oxygen-sensitive radicals. The cation charge does not cross the bilayer on a time scale of less than 0.01 s. These data define a reaction localized precisely in the finite interfacial region of the lipid bilayer-water interface.

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SITE‐SELECTION SPECTROSCOPY OF CHLOROPHYLL b IN MEMBRANES OF LECITHIN VESICLES AND IN OTHER SOLVENTS

Cited by 18 publications

References 18 publications

Photoinduced electron transfer across membranes

Photoinduced electron transfer across membranes

Chlorophyll Photosensitized Electron Transfer in Phospholipid Bilayer Vesicle Systems: Correlations Between Kinetic Parameters and Solubilities of Viologen Acceptors *

Distributed kinetics of decay of the photovoltage at the lipid bilayer-water interface

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