A 1H-NMR study of the influence of n-alcohols on the stoichiometry of melittin-induced permeability of phospholipid vesicles

Effect of some potassium selective crown ethers on the permeability and structure of a phospholipid membrane

The effect of some new crown ethers on the cation efflux and phase transition parameters of dipalmitoyl phosphatidylcholine liposomes was studied. The effects were correlated with the lipophilicity of the crown ethers. The results indicate that the presence of two crown ring structures in one crown either molecule is a prerequisite for the increase of ion permeability of liposomes. The effective crown ethers decrease the temperature, enthalpy and cooperativity of the gel-to-liquid crystalline phase transition. The crown ethers increase membrane permeability for potassium and, to a lesser extent, for rubidium and sodium. The ratio of permeability increase for potassium/rubidium significantly correlates with the lipophilicity of the crown ethers.

Interaction of monoamine oxidase inhibitory drugs with some phospholipids

The effect of 17 monoamine oxidase inhibitory drugs (propargylamine derivatives) on the phase transition parameters of some synthetic phospholipids has been studied by differential scanning calorimetry. The drugs modified the thermal behaviour of phospholipids proving the existence of phospholipid-drug interactions. Phosphatidylethanolamine, phosphatidylcholine and phosphatidic acid equally interact with the monoamine oxidase inhibitory drugs. Significant correlations were found between the change of the phase transition parameters of phospholipids and the hydrophilic and hydrophobic molecular parameters of drugs. Calculations suggest that both hydrophilic (between the head group of phospholipids and the polar propargylamine group of drugs) and hydrophobic (between the apolar fatty acid chains of phospholipids and the lipophilic substructures of drugs) forces are involved in the phospholipid-drug interaction. Chloro substitution in the hydrophobic moiety of drugs enhances considerably the strength of interaction.

Interaction of phospholipids with proteins, peptides and amino acids. New advances 1987-1989

1. The review deals with the recent achievements in the study of the various interactions of phospholipids with proteins, peptides and amino acids. The interactions are classified according to the hydrophobic, hydrophilic or mixed character of the interactive forces. The effect of the interaction on the structure and biological activity of the interacting biomolecules is discussed.

31P- and 1H-NMR investigations of the effect of n-alcohols on the hydrolysis by phospholipase A2 of phospholipid vesicular membranes

31P- and 1H-NMR spectroscopy of small, unilamellar egg yolk phosphatidylcholine (PC) vesicles in the presence of the lanthanide ion Dy3+ have been used to study the effect of various n-alcohols on the permeability induced by the action of the enzyme phospholipase A2 (PLA2). The method allows the monitoring of the number of PC and lysoPC molecules in the outer and inner monolayers. The results indicate that the initial rate of hydrolysis of PC by PLA2 is increased by all the n-alcohols but in a chain-length dependent manner and that the maximum rate occurs at n = 8 (octan-1-ol). The subsequent rate is dependent upon the rate of transbilayer lipid exchange (flip-flop) of PC molecules from the inner to the outer monolayer. The vesicles only become permeable to the Dy3+ ions when lysoPC is mobilised in the flip-flop process of exchange of lipid molecules between the two monolayers. The n-alcohols affect both the time taken to initiate flip-flop of inner monolayer PC and the subsequent rate of permeability to Dy3+. The n-alcohols are seen to affect all the above rates in an identical chain-length dependent manner, indicating a common cause for all observations which we identify as the degree of clustering of the n-alcohol molecules in the bilayer. The results are discussed in terms of the chain-length dependent mechanism of n-alcohol interactions with the membrane and the mechanism by which the vesicles become permeable to Dy3+ ions.