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SPECTROSCOPIC STUDIES OF CHLOROPHYLL a AGGREGATES FORMED BY AQUEOUS DIMETHYL SULFOXIDE
Author(s) -
UEHARA KAKU,
MIMURO MAMORU,
TANAKA MAKOTO
Publication year - 1991
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1991.tb03643.x
Subject(s) - dimethyl sulfoxide , chemistry , fluorescence , photochemistry , aqueous solution , dimer , monomer , chlorophyll , absorption (acoustics) , chlorophyll a , molecule , quantum yield , micelle , polymer , organic chemistry , materials science , biochemistry , physics , quantum mechanics , composite material
— 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.