Cholesterol protects phosphatidylcholine liposomes from N,N-dimethyldodekanamine N-oxide influence

Abstract

The interaction of N,N-dimethyldodekanamine N-oxide (C₁₂(CH₃)₂NO) with egg yolk phosphatidylcholine (EYPC) liposomes containing cholesterol (CHOL) in molar ratios n_CHOL:n_EYPC = 0-0,8 was studied. The perturbation of CHOL-EYPC bilayers in unilamellar liposomes (ULL) was observed by the leakage of fluorescent probe calcein. The dependence of fluorescence intensity on the C₁₂(CH₃)₂NO concentration is composed of three parts. D_T^PERT and D_T^REL were evaluated as the total C₁₂(CH₃)₂NO concentrations, causing the onset of the intensive leakage of calcein and the total release of calcein, respectively. More detergent is needed to perturb the membrane when the amount of CHOL in bilayer increases. The process of CHOL-EYPC ULL solubilization induced by C₁₂(CH₃)₂NO also consists of three stages. D_T^SAT and D_T^SOL were determined turbidimetrically as the total C₁₂(CH₃)₂NO concentrations, causing the onset of bilayer – micellar phase transition and the completion of solubilization, respectively. Both D_T^SAT and D_T^SOL increase with the increasing n_CHOL:n_EYPC. The structure of liposomes is still preserved at total calcein release (D_T^REL) for all n_CHOL:n_EYPC