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  • Title: [Spectral-luminescent properties of separate aggregated forms of pigments in solutions].
    Author: Zen'kevich EI, Kochubeev GA, Losev AP, Gurinovich GP.
    Journal: Mol Biol (Mosk); 1978; 12(5):1002-11. PubMed ID: 739987.
    Abstract:
    The aggregated forms of protochlorophyll a (PChl), 4-vinyl-protochlorophyll a (4VPChl) and chlorophyll a (Chl) in binar mixtures of dioxane-water was investigated. The aggregates are oligomer particles of pigment molecules having considerable degrees of fluorescence polarisation which points to their ordered structure. Two types of fluorescent associates I and II have been discovered. By its electronic spectrum I is similar to the molecular pigment but has smaller quantum yield B congruent to 10(-2) and the lifetime of fluorescence tau congruent to 3--4.10(-9) sec. Associates of type I spontaneously transform into associates of type II which have narrower bands of electronic spectrum than the monomer, very low B congruent to 10(-3)--10(-4) and tau congruent to 2--4.10(-10) sec. In contrast with the decreasing of B and the band intensities in CD spectrum conditioned by rotational strength increase by factor of 100 under transformation from I to II. It follows from these data that the antibatic connection possibly exists between excitation deactivation in associates and their optical activity. From data on splitting the associate CD spectra of type I and II the excitation interaction energy V12 congruent to 75 cm-1 was estimated. The reasons of increasing of rotational strength under transformation from I to II and the overturn of the sign dependence of bands in CD spectrum in some cases are discussed.
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