SPECTROSCOPIC STUDIES OF CHLOROPHYLL a AGGREGATES FORMED BY AQUEOUS DIMETHYL SULFOXIDE |
| |
Authors: | KAKU UEHARA MAMORU MIMURO MAKOTO TANAKA |
| |
Affiliation: | Department of Applied Chemistry, College of Engineering, University of Osaka Prefecture, Mozu-Umemachi, Sakai, Osaka 591;National Institute for Basic Biology, Myodaiji, Okazaki, Aichi 444, Japan |
| |
Abstract: | Characteristic chlorophyll (Chl) a aggregates formed in aqueous dimethyl sulfoxide (DMSO) were investigated spectroscopically. Four chlorophyll forms were found with increasing DMSO concentration; they are called A-672, A-683, A-695 and A-665 according to the wavelengths of their absorption maxima. Transformation occurred only in this order. Reverse transformation could not be realized. A-683 and A-695 were apparently formed by the interaction of Chl a with DMSO in the linear dimer and linear polymer arrangements, respectively. Coordination of the Mg atom with a DMSO O atom and interaction between the S atom of one DMSO molecule and the O atom of an other DMSO molecule should lead to formation of a sandwich-type complex of partially overlapping chlorophyll macrocycles (Chl a-DMSO)n. A-672 and A-665 were assigned to Chl a micelles and to dissolved monomeric Chl a in DMSO, respectively. Fluorescence spectra showed that the A-683 was highly fluorescent, while the A-695 was less fluorescent. Energy migration within the A-695 form to a trap with a low fluorescence yield might be responsible for this difference in the emission intensity. |
| |
Keywords: | |
|
|