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PHOTODYNAMIC ACTION OF MEROCYANINE 540 IN ARTIFICIAL BILAYERS AND NATURAL MEMBRANES: ACTION SPECTRA AND QUANTUM YIELDS
Author(s) -
SINGH RAVINDER J.,
FEIX JIM B.,
PINTAR THOMAS J.,
GIROTTI ALBERT W.,
KALYANARAMAN B.
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.tb03661.x
Subject(s) - merocyanine , membrane , action (physics) , chemistry , biophysics , photochemistry , physics , biology , biochemistry , quantum mechanics , photochromism
— The action spectra and quantum yields for singlet oxygen ( 1 O 2 ) generation by merocyanine 540 (MC540) in liposomes and isolated erythrocyte membranes were obtained using electron spin resonance techniques. Oxygen consumption was measured by spin label oximetry in the presence of histidine for fully‐saturated dimyristoylphosphatidylcholine vesicles, mono‐unsaturated 1‐palmitoyl‐2‐oleoylphosphatidylcholine vesicles and erythrocyte membranes. The quantum yield for the photogeneration of 1 O 2 by membrane‐bound MC540 in aqueous buffer was determined to be 0.065 ± 0.005, which is approx. 1/10 of the value determined for Rose Bengal under similar conditions. Using unilamellar liposomes and isolated erythrocyte membranes containing MC540 at different monomer/dimer ratios, we have observed that the action spectra of 1 O 2 generation closely overlap the absorption spectra of the monomeric dye in these systems. It is likely that factors which affect the monomer‐dimer equilibrium of MC540 will influence the production of 1 O 2 . These findings have important implications for the phototherapeutic efficacy of MC540.