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Time-resolved fluorescence anisotropy studies on the interaction of biologically active polycations with phospholipid membranes

1990; Elsevier BV; Volume: 1021; Issue: 1 Linguagem: Inglês

10.1016/0005-2736(90)90384-z

1879-2642

Tomiki Ikeda, Bong Lee, Hideki Yamaguchi, Shigeo Tazuke,

Molecular Sensors and Ion Detection

Interaction of a polymeric in-chain quaternary ammonium salt with phospholipid bilayer membranes was studied by time-resolved fluorescence spectroscopy with the aid of a picosecond time-rcorrelated single photon counting system (instrument response function, 70 ps FWHM). Particular attention was paid to a phenomenon of polycation-induced fluidization of the membranes, which was well evaluated by time-resolved fluorescence anisotropy measurements. The fluorescence anisotropy, r(t), of 1,6-diphenyl-1,3,5-hexatriene (DPH) embedded in the membranes was analyzed based on the wobbling-in-cone model. Strong interaction was observed between the polycation and a negatively charged phosphatidic acid membrane as demonstrated by a large decrease of residual polarization value on adding the polycation to the acidic phospholipid dispersion. This means that the cone angle of the wobbling-in-cone motion of the DPH molecule increases by the addition of the polycaton, indicative of the polycation-induced fluidization of the acidic membrane. On the other hand, r(t) of DPH embedded in a zwitterionic phosphatidylcholine membrane was not affected significantly by the addition of the polycation, which is presumably due to non-binding of the polycation to the zwitterionic membrane. Our results clearly indicate that the polycationic disinfectant interacts strongly with negatively charged membranes, inducing fluidization of the membranes.