Electronic Processes and Photoelectric Aspects of Bilayer Lipid Membranes

Abstract

— Owing to the complexity of biological membranes, many model systems have been studied in order to gain insight into the molecular mechanism of specific functions. One such model membrane extensively investigated in the past decade is the so‐called bilayer lipid membrane (BLM). With suitable modifications, a BLM less than 100 A thick separating two aqueous solutions has been used as a model for a variety of biological membranes. This paper is devoted to a review of the properties and electronic processes of modified BLM. Recent experiments using these membranes which contain photosynthetic pigments or dyes have demonstrated that, upon illumination, an EMF and a current can be generated. The connection between the photoelectric BLM and light‐sensitive biological membranes and the rationale for this work are described. Additionally, the effects of physical chemical parameters such as electric field, temperature, light intensity, duration of illumination and chemical agents (electron acceptors, donors, uncouplers, etc.) on the photoresponses of BLM are discussed. Other results indicate that BLM containing photoactive compounds behave similar to that of a silicon solar cell with one side of the membrane reducing and the other side oxidizing. The transverse pathway for the electron across the BLM could be provided by carotenoids such as β‐carotene. Photoelectric BLM of this type represents a unique kind of energy transducing system and may well be useful in the conversion of solar energy into electricity and/or other forms of energy.

Bluelight-induced, flavin-mediated transport of redox equivalents across artificial bilayer membranes

“…Preliminary but highly significant results obtained with these systems demonstrate that bluelight is capable of inducing reversible pH-and potential gradients across the vesicle membrane. Taking the relatively high activation energies of about 40 kJ/M for these membrane-associated redox processes into account [48], the results presented exclude a purely electronic transmembranous pathway as suggested for membrane-bound carotenoids in photosynthetic membranes [2,58,59].…”

“…These 'systems include phytochrome [14,28], rhodopsin [34,37,61], bacteriorhodopsin [17,40], stentorin [54,55] and chlorophyll [5,11]. More artificial pigment/membrane systems have been described as well [4,7,8,18,19,20,23,24,26,35,59]. However, due to the ubiquitous appearance of flavins, so far the bluelight receptor flavin has escaped clear-cut identification+ purification, and as a result, reconstitution.…”

Photoinduced interaction of riboflavin dye with different reducing agents in aqueous and liposome media

“…The photoeffects in lipid membranes containing dyes have been widely studied for many years (Tien, 1976(Tien, , 1989Barber, 1979;Antonili et al, 1982). We have also reported the photoeffects which cause the photovoltage generation in phospholipid liposome containing phenosafranin, thionine, riboflavin and dioctadecyloxacarbocyanine dyes (Bhowmik et al, 1988aSen Varma and Bhowmik, 1990, 1991, 1992Sen Varma et al, 1995).…”

Effect of plastocyanin and phycocyanin on the photosensitivity of chlorophyll-containing bilayer membranes

“…Membranes containing monogalactosyl diglyceride were found to be extremely stable and were most susceptible to enhancement of photosensitivity by introduction of the proteins. The plastocyanin and C-phycocyanin when used together appeared to operate synergistically.Photovoltaic effects of pigmented bilayer membranes have been studied intensively in recent years and a large number of the contributions from several laboratories have been reviewed [3,11,22]. Such membranes containing the appropriate pigments are photosensitive if a gradient in redox potential, pH or electrical potential is created across the membrane.…”

“…Photovoltaic effects of pigmented bilayer membranes have been studied intensively in recent years and a large number of the contributions from several laboratories have been reviewed [3,11,22]. Such membranes containing the appropriate pigments are photosensitive if a gradient in redox potential, pH or electrical potential is created across the membrane.…”