K Walinska

Electroporation of polyprenol-phosphatidylcholine bilayer lipid membranes

Abstract The electrochemical measurements showed that tetracosaprenol (C 120 ) isolated from leaves of Spermatophyta influenced some properties of phosphatidylcholine macrovesicular bilayer lipid membranes. The current–voltage characteristics, the membrane conductance–temperature relationships and the membrane breakdown voltage have been measured for different mixtures of tetracosaprenol and DOPC. The membrane conductance, the permeability coefficient for Cl − ions and the activation energy of ion migration across the membrane were determined. Tetracosaprenol decreases the membrane breakdown voltage and the activation energy, increases the membrane conductance and the membrane ionic permeability for Cl − ions. These results indicate that long-chain polyprenols modify bilayer lipid membranes by the formation of fluid microdomains and point to the importance of transmembrane electrical potential in the dynamics and aggregation behaviour of polyisoprenols in membranes. The results also indicate that electrical transmembrane potential can accelerate the formation of pores in lecithin–polyprenol bilayers at the microdomains border.

The effect of hexadecaprenyl diphosphate on phospholipid membranes.

In the present study we investigated phospholipid bilayer membranes and phospholipid vesicles made from dioleoylphosphatidylcholine (DOPC) or its mixture with the phosphate ester derivative of long-chain polyprenol (hexadecaprenyl diphosphate, C(80)-PP) by electrophysiological and transmission electron microscopy (TEM) techniques. The membrane conductance-temperature relationships and the membrane breakdown voltage have been measured for different mixtures of C(80)-PP/DOPC. The current-voltage characteristics, the membrane conductance, the activation energy of ion migration across the membrane and the membrane breakdown voltage were determined. Hexadecaprenyl diphosphate decreases the membrane conductance, increases the activation energy and the membrane breakdown voltage for the various values of C(80)-PP/DOPC mole ratio. The analysis of TEM micrographs shows several characteristic structures, which have been described. The data indicate that hexadecaprenyl diphosphate modulates the surface curvature of the membranes by the formation of aggregates in liquid-crystalline phospholipid membranes. The properties of modified membranes can result from the presence of the negative charges in the hydrophilic part of C(80)-PP molecules and can be modulated by the concentration of this compound in membranes. We suggest that the dynamics and conformation of hexadecaprenyl diphosphate in membranes depend on the transmembrane electrical potential.

Modulation of properties of phospholipid membranes by the long-chain polyprenol (C160).

The electrical measurements of phospholipid bilayers and the studies of phospholipid vesicles by using the transmission electron microscopy (TEM) showed that dotriacontaprenol (C(160)) isolated from leaves of Spermatophyta influences some properties of membranes. The current-voltage characteristics, the membrane conductance-temperature relationships, the membrane breakdown voltage and the membrane capacitance have been measured for different mixtures of C(160)/DOPC. The membrane conductance, the activation energy of ion migration across the membrane and the membrane thickness were determined. Dotriacontaprenol decreases the membrane breakdown voltage, the activation energy and the membrane capacitance, and increases the membrane conductance and the membrane hydrophobic thickness. The analysis of TEM micrographs shows several characteristic structures, which have been described. The results indicate that dotriacontaprenol increases the membrane elasticity and modulates the surface curvature of the membranes by the formation of fluid microdomains. We suggest that the long polyprenols facilitate the formation of transmembrane, ions-conductive pores.

Properties of hexadecaprenyl monophosphate/dioleoylphosphatidylcholine vesicular lipid bilayers.

Abstract. In our study we investigated hemispherical phospholipid bilayer membranes and phospholipid vesicles made from hexadecaprenyl monophosphate (C80-P), dioleoylphosphatidylocholine (DOPC) and their mixtures by voltammetric and transmission electron microscopy (TEM) techniques. The current-voltage characteristics, the membrane conductance-temperature relationships and the membrane breakdown voltage have been measured for different mixtures of C80-P/DOPC. The membrane hydrophobic thickness and the activation energy of ion migration across the membrane have been determined. Hexadecaprenyl monophosphate decreased in comparison with DOPC bilayers, the membrane conductance, increased the activation energy and the membrane breakdown voltage for the various value of C80-P/DOPC mole ratio, respectively. The TEM micrographs of C80-P, DOPC and C80-P/DOPC lipid vesicles showed several characteristic structures, which have been described. The data indicate that hexadecaprenyl monophosphate modulates the surface curvature of the membranes by the formation of aggregates in liquid-crystalline phospholipid membranes. We suggest that the dynamics and conformation of hexadecaprenyl monophosphate in membranes depend on the transmembrane electrical potential. The electron micrographs indicate that polyprenyl monophosphates with single isoprenyl chains form lipid vesicular bilayers. The thickness of the bilayer, evaluated from the micrographs, was 11 ± 1 nm. This property creates possibility of forming primitive bilayer lipid membranes by long single-chain polyprenyl phosphates in abiotic conditions. It can be the next step in understanding the origin of protocells.

Comparison of the influence of the polyprenol structure on model membranes

Abstract Polyprenols have been found in many bacterial and plant membrane fractions. Long-chain polyprenols with 12–100 isoprene residues have been isolated from the green leaves of Spermatophtyta. The pattern of polyprenols is species-specific. Polyprenyl phosphates are obligatory intermediates in the biosynthesis of sugar polymers and formation of glycoproteins. Model membranes (BLM and liposomes) made from phospholipid and polyprenols with different number of isoprene residues were investigated in the present study. The electrical (the membrane breakdown voltage and the membrane capacitance) and mechanical properties (the membrane hydrophobic thickness and membrane Youngs modulus) of model membranes were measured by the voltammetric technique. The vesicle morphology was analysed by TEM. Polyprenols change studied parameters of membranes appear to increase the fluidity of phospholipid bilayers and destabilize membranes. This effect depends on the number of isoprene units in the polyprenol molecule. The micrographs show that lipid vesicles prepared from PC are regular whereas lipid vesicles prepared from prenol/ phospholipid, besides regular structures, form several irregular characteristic structures. The results can be regarded as the evidence that lipids may directly influence the activity of biological membranes by changing their fluid-crystalline properties. Some functions of polyprenols in bilayers are connected with modification of some properties of the membranes.