Photoinduced Charge Separation Process of Porphyrin in Liposomal Membrane
| Autor: | Kiyoyuki Watanabe, Hiroaki Komatsu, Yuzaburo Fujita, Keiko Togawa, Takashi Katsu |
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| Rok vydání: | 1984 |
| Předmět: | |
| Zdroj: | NIPPON KAGAKU KAISHI. :345-353 |
| ISSN: | 2185-0925 0369-4577 |
| DOI: | 10.1246/nikkashi.1984.345 |
| Popis: | Meso-IX-Cn, and Zn-meso-IX-Cn with long hydrocarbon chains were synthesized (Scheme 1)to investigate the photoinduced charge separation process in the DPPC liposomal membrane from the inner EDTA (electron donor) to the outer MV2+ (electron acceptor) via excited porphyrins (Fig.1). There were three types of porphyrins in the forms of monomer, oligomer, and aggregated solid in the membrane (Figs.6, 7, and 8), and the monomer was the most efficient form for the photoelectron transfer through the membrane. The optimum concentration ratio of pigment/lipid was found to be-1/100 (Fig.9). From the result of temperature dependency measurements of photoelectron transfer efficiency, meso-IX-Cn's were classified into three types (Fig.4). Among these, the Type II porphyrins exhibited higher activities at low temperature range. Incorporation of the Type II porphyrins in the membrane caused an increase in fluidity at the microenvironment of the pigment (Fig.5), and the efficiency of photoelectron transfer increased with fluidity (Figs.8 and 9). The optimum chain length was found to be around C. (Fig.4).The position of the prophyrin in the membrane had also a significant effect on the transfer efficiency (Fig.10 and Table 1), and a large efficiency was observed with the porphyrin positioned mainly at the hydrophilic region in the membrane. The effect of the membrane potential induced by the transport of K+ with Val was not so large as that was reported by Glavin et al.; because, in the present work, the porphyrin, meso-IX-Cn used as the photosensitizer was found to act as a proton carrier, and this canceled efficiently the potential imbalance induced by the electron transfer (Figs.12, 13, and 14). It was suggested that the photoelectron transfer through the membrane occurred by the electron-exchange mechanism between the inner excited porphyrin and the porphyrin cation radical photoproduced at the outer interface. |
| Databáze: | OpenAIRE |
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