Surface enhanced fluorescence of Merocyanine 540 dimers at membrane water interface of gel phase lipid vesicle.

TYMCZYSZYN E.; BERNIK D

Buenos Aires - Argentina

Congreso; III Congreso Iberoamericano de Biofísica; 1997

Partition of water soluble Merocyanine 540 dye into lipid membranes gives origin to the coexistence of different species. Tail to head dimers absorb at 530 nm and have been reported as non or slightly fluorescent (Waggoner and Grinvald. Ann N.Y. Acad Scie.) However, most of the assays have been carried out at temperature at which the membranes were in the liquid-crystalline phase state. A fluorescent signal al 650 nm was reported by Stillwel et al. (Biochem. Biophys. Acta 1146(1993)pp 136-144) as sensor of the lipid packing, but no assignment of this band to any dye specie was done. In a subsequent work. We have demonstrated that the fluorescent signal at 630 nm corresponds to the absorption band at 530, that is to dimer associated to the lipid membrane (Bernik and Disalvo, Biochem. Biophys.Acta 1146(1993)pp169-177 and Chem.Phys.Lipids 82(1996)pp111-123). Although fluorescent dimers are not usually found in solution, fluorescent dimers in absorbed states has been previously repoted(Kemnitz et.al, J.Phys.Chem.90(1986)pp5094-5101). Based on the excitonic theory of Kasha (McRae and Kasha, J.Chem.Phys.28(1958)pp721) the fluorescent character of dimer depends on the relative orientation of the monomers. IN this work, we analyze the possible explanation of dimer fluorescent and its ability as packing sensor in lipid bilayer surfaces.