Excited state reactions of amphiphilic Zn(II) porphyrin incorporated into liposomes as models for biological electron transfer |
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Authors: | Masao Kaneko |
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Affiliation: | (1) The Institute of Physical Chemical Research, Wako, 351-01 Saitama, Japan |
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Abstract: | The amphiphilic porphinato zinc(II) complex (ZnP) containing four substituted amphiphilic alkyl chains was embedded in the liposomes of l,2-dipalmitoyl-sn-glycero-3phosphocholine. The distance from the embedded ZnP to the outer phase was changed from 9 to 27 ? by changing the substituted alkyl chain length. The electron transfer from the excited Zn complex to methylviologen (MV2+) or benzoquinone (BQ) added in the outer aqueous phase was studied. At first, quenching reactions were analyzed based on dynamic and static reaction models of the excited state. For the MV2+ quencher, only the triplet excited state of the embedded ZnP reacted, and electron transfer occurred at a distance less than 12 ?. In BQ both the singlet and the triplet excited states reacted, and the reaction of the singlet state was a static one indicating that BQ is incorporated into the liposomes. The distribution of the BQ molecule in the quenching sphere of ZnP was presented based on calculations assuming a stepwise incorporation into the quenching sphere. |
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Keywords: | Zinc porphyrin liposome quenching methylviologen benzoquinone electron transfer quenching models |
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