Abstract
The interactions between anionic random copolypeptides and cationic bilayer membrane composed of distearyldimethylammonium chloride (DSACl) were investigated and the effect of hydrophobicity of the anionic copolypeptide on these interactions was thermodynamically elucidated. The anionic copolypeptides, poly(L-glutamic acid)s containing various amounts of γ-methyl L-glutamate as a hydrophobic residue (MG/GA (X/100−X)), X is a mol% of γ-methyl L-glutamate residues have been prepared by saponification reaction of poly(γ-methyl L-glutamate) (PMG, M̅v=4400) whose length along the α-helix rod is almost comparable with the thickness (37 Å) of the bilayer membrane formed by DSACl. The partition of MG/GA into the DSACl membrane interior was shown to decrease by decreasing the degree of hydrophobicity of MG/GA. As a result, the incorporation of the copolypeptide could not occur with MG/GAs containing more than 30 mol% L-glutamic acid residue, which was almost localized at the membrane surface. It was shown that the concentration of MG/GA in the bilayer membrane above Tc was higher than that below Tc. Temperature dependence of the partition equilibrium of MG/GA between the membrane surface and membrane interior also showed positive changes in enthalpy and entropy, respectively, accompanied by the incorporation of the copolypeptide into the membrane. It was also shown that the sodium ion permeability through the bilayer membrane had a maximum value when MG/GA with 12 mol% L-glutamic acid residue was incorporated into the membrane.
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Higuchi, M., Kinoshita, T., Takizawa, A. et al. Effect of Hydrophobicity of Anionic Copolypeptides on the Structure and Functions of Cationic Bilayer Membrane. Polym J 21, 295–302 (1989). https://doi.org/10.1295/polymj.21.295
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DOI: https://doi.org/10.1295/polymj.21.295
