Effects of Flavonols on the Magnitude of Dipole Potential of Phospholipid Bilayers

Abstract

The changes in K+-nonactin steady-state membrane conductance were measured to estimate the changes in the dipole potential (Δφd) of phospholipid bilayers (DOPS, DOPE, DOPC) after two-side addition of quercetin or myricetin into membrane bathing solution (0.1M KCl pH7.4). Table presents the results of the approximation of the obtained data by Langmuir adsorption isotherm. The maximum dipole potential change Δφd(∞) depends on flavonol and membrane types. It is larger in case of quercetin than for myricetin. This difference may be attributed to higher hydrophobicity of quercetin compared with myricetin. The smaller values of |Δφd(∞)| in the case of DOPS and DOPE than for DOPC may be resulted from smaller effective surface density of dipoles due to electrostatic repulsion between serine residues and negative spontaneous curvature of DOPE relative to membranes made from the phospholipid with neutral spontaneous curvature, DOPC. Comparison of dissociation constants (K) shows that flavonol affinity for DOPE-bilayers is smaller than that for DOPS and DOPC-membranes. The study was supported in part by RFBR, the Grant of the President of RF (#MK-1813.2012.4) and the Russian State Contract #8119 (MES, FTP, SSEPIR).