INTRALIPOSOMAL DISTRIBUTION OF TRIMETHYLE STER OF CHLORINE E(6) WHEN CHANGING THE LIPID BILAYER PHASE STATE

Unilamellar liposomes of dimyristoyl-phosphatidylcholine have been cho sen as suitable models in studies aimed at defining the influence of m embrane phase state on the intramembrane distribution of hydrophobic p hotosensitizer trimethyl ester of chlorine e(6)(TME). The intramembran e localization pattern was studied by fluorescence quenching technique with the watersoluble quencher anthraquinone-2,6-dis ulfonate. The re sults obtained indicate that a considerable increase of quenching effi ciency observed For liposomes with pigment:lipid ratio higher 1:800 do es not reflect the change of TME distribution between outer and inner monolayer but occurs as the result of excitation energy transfer. A dr astic decrease of quenching rate is observed when liposomal membrane s tate changes from gel to liquid crystalline state. On the basis of dat a on membrane partition coefficient it was determined that phase trans ition-dependent membrane and water bulk. Following the data on studies of pigment fluorophors accessibility to the quencher it has been esti mated that about 80% and 66% of TME molecules are localized in outer l ipid monolayer when DMPC liposomes are in gel and liquid crystalline s tate.