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CHLOROPHYLL a AND CAROTENOID AGGREGATES AND ENERGY MIGRATION IN MONOLAYERS AND THIN FILMS
Author(s) -
SINESHCHEKOV V. A.,
LITVIN F. F.,
DAS M.
Publication year - 1972
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.1751-1097.1972.tb06238.x
Subject(s) - fucoxanthin , monolayer , chlorophyll a , chlorophyll , absorption (acoustics) , carotenoid , zeaxanthin , chlorophyll c , chemistry , chlorophyll b , molecule , absorption spectroscopy , pigment , analytical chemistry (journal) , photochemistry , fluorescence , materials science , chlorophyll fluorescence , lutein , chromatography , organic chemistry , optics , food science , physics , biochemistry , composite material
— The spectra of absorption, fluorescence and excitation of monolayers and thin films containing chlorophyll a together with a carotenoid ( cis ‐β‐carotene, trans ‐β‐carotene, fucoxanthin, or zeaxanthin), were measured at — 196°C. The concentration ratios used, (Chl)/(Car), were 6:1, 4:1, 3:1, 2:1, 1:1 and 1:3, and the area densities, 3·70, 2·55, 1·76, 0·71, 0·37 and 0·17 nm 2 /pigment molecule. In dilute monolayers, (3·70 nm 2 /molecule), with a constant concentration ratio (Chl)/(Car) = 3:1, evidence of three β‐carotene forms, with absorption bands at 460, 500 and 520 nm (C 460 , C 500 and C 520 ), and of a chlorophyll a form with an absorption band at 669–672 (Chl 669–672 ) was found. On increasing the density to 0·2–0·3 nm 2 /molecule, a conversion of C 460 and C 520 into C 500 , was observed, and several more additional (probably more strongly aggregated) chlorophyll a forms appeared, with absorption bands at 672–733 nm. With excess carotene [(Chi)/(Car) = 1:3] the forms C 460 , C 500 , C 520 and Chl 669–672 were present even in the most dense films (0·2–0·3 nm 2 /molecule). The same was found with other carotenoids: if one of the pigments was in excess, aggregated forms of the other tended to disappear. In the transfer of energy from carotenoids to chlorophyll a , C 500 was found to be the main donor. In layers with a concentration ratio (Chl)/(Car) = 3:1, the efficiency of transfer was less than 10 per cent at the lowest density used (3·70 nm 2 /molecule); it increased to 50 per cent, as the density was increased to 0·20 nm 2 /molecule. When the relative concentration of the carotenoid was increased to (Chl)/(Car) = 1:1, the efficiency of energy transfer dropped to 25 per cent even at 0·20 nm 2 /molecule. It seems that the efficiency of energy transfer between carotene molecules (prior to its transfer to chlorophyll a ) is low, and effective transfer occurs only between β‐carotene and immediately adjacent chlorophyll a molecules.