Use of DMPC and DSPC lipids for verapamil and naproxen permeability studies by PAMPA.ДЄlvarez-Figueroa, M J Contreras-Garrido, B C Soto-Arriaza, M A Moreover, the incorporation of the anesthetic into DMPC bilayers with or without cholesterol results in a reduction of the lipid order parameters both in the plateau and in the tail regions of the acyl chains, this effect being greater with the charged form of the anesthetic.Г‚В«Г‚В less An increase in temperature results in a deeper penetration of the anesthetic into the bilayer. The present study suggests that the location of tetracaine in the cholesterol-containing system is different from that in pure phosphatidylcholine bilayers: the anesthetic sits higher in the membrane. For phosphatidylcholine bilayers, it has been proposed that the charged tetracaine at low pH is located mostly at the phospholipid headgroup level while the uncharged tetracaine intercalates more deeply into the bilayer. ThemoreГ‚В Г‚В» lower partition coefficients for the DMPC/cholesterol system at both pH values suggest that cholesterol, which increases the order of the lipid chains, decreases the solubility of tetracaine into the bilayer.

The higher partition coefficients obtained at pH 9.5 reflect the hydrophobic interactions between the uncharged form of the anesthetic and the hydrocarbon region of the bilayer. The partition coefficients of the anesthetic in the membrane have been measured at both pH values for phosphatidylcholine bilayers with and without cholesterol. Experiments were performed at pH 5.5, when the anesthetic is primarily charged, and at pH 9.5, when it is primarily uncharged. The interactions of local anesthetic tetracaine with multilamellar dispersions of 1,2- dimyristoyl-sn-glycero-3-phosphocholine ( DMPC) and cholesterol have been investigated by deuterium nuclear magnetic resonance of specifically deuteriated tetracaines, DMPC and cholesterol. Interactions of the local anesthetic tetracaine with membranes containing phosphatidylcholine and cholesterol: a /sup 2/H NMR study Whereas Cd2+ does not bind to the neutral DMPC, it binds to charged DMPA up to a 0.8ГўЛ†в™Ў Cd/lipid ratio. The binding of Cd2+ to the model membranes Di-myristoyl L-ГЋВ±-phosphatidic acid (DMPA) and Di-myristoyl L-ГЋВ±- phosphatidylcholine ( DMPC) was studied by time differential perturbed angular correlation (TDPAC) on111mCd, via its nuclear quadrupole interaction. DLS experiments are also consistent with partial liposome solubilization at PFOA/lipid molar ratios > 1, which suggests the formation of mixed PFOA-lipid micelles. These findings suggest that PFOAГўв‚¬в„ўs effect on the phase behavior of phosphatidylcholines depends on the cooperativity and state (i.e., gel versus liquid phase) of the membrane.

PFOA caused swelling of DMPC but not DPPC and DSPC liposomes at 37Г‚вЊ in the DLS experiments, which suggests that PFOA partitions more readily into bilayers in the fluid phase. Although PFOAГўв‚¬в„ўs effect on the on Tm and the transition width decreased in the order DMPC > DPPC > DSPC, its relative effect on the phase behavior was largely independent of the phosphatidylcholine. PFOA caused a linear depression of the main phase transition temperature Tm while increasing the width of the phase transition of all three phosphatidylcholines.

The chain length dependence of the interaction of PFOA, a persistent environmental contaminant, with dimyristoyl- ( DMPC), dipalmitoyl- (DPPC) and distearoylphosphatidylcholine (DSPC) was investigated using steady-state fluorescence anisotropy spectroscopy, differential scanning calorimetry (DSC) and dynamic light scattering (DLS). PARTITIONING OF PERFLUOROOCTANOATE INTO PHOSPHATIDYLCHOLINE BILAYERS IS CHAIN LENGTH-INDEPENDENT

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