Polymerization of Amino Acids in Liposomal Membrane under Reduced Pressure and Normal Pressure

Abstract

Incorporation of polypeptides with hydrophobic side groups into lipid bilayers was achieved by the polymerization of N-carboxy anhydrides of γ-dodecyl l-glutamate and of γ-benzyl d-glutamate in DMPC liposomal membrane under reduced pressure and normal pressure. The effects of polypeptide conformations on the barrier properties of liposomal membrane incorporating polypeptide were examined. There was little difference in the trapping volume when liposomes prepared under reduced pressure and normal pressure were compared. The incorporation of polypeptides into the membrane bilayer had a tendency to decrease the volume trapping efficiencies. It was found that in the membrane-free aqueous phase, polymerization of N-carboxy amino acid anhydrides promoted formation of β-structure and in the membrane bilayer formation of α-helix structure was enhanced. The content of α-helical polypeptide was maximum for liposomes prepared under reduced pressure. The activation energies for water permeation across the liposomal membrane were lowered by the incorporation of polypeptdes into the membrane bilayer. The incorporation of α-helical polypeptide was more ceffective than that of β-structured one for the lowering of activation energies. The permeability barrier properties of liposomal membrane were larger for liposome incorporating poly(γ-dodecyl l-glutamate) (PDOLG) than for liposome incorporating poly(γ-benzyl d-glutamate)(PBDG). This seems to be due to a difference in miscibilities with lipid in the membrane bilayer.

Liposome-Assisted Selective Polycondensation of α-Amino Acids and Peptides

“…These hydrophobic chains enabled the amino acids to be anchored in an organized way to the liposome, and due to the increased local concentration on the surface, oligomerization was possible. Several variations of this main idea have been published in the literature. − This kind of polycondensation on liposomes is based on the interaction between amino acid derivatives and the lipidic surface. This type of interaction was proposed to be central in prebiotic chemistry and precellular, chemical evolution. − The possible relevance of surfactant aggregates to the origin of life at large has been emphasized by our group on the basis of self-reproducing micelles and vesicles. − …”

“…Several variations of this main idea have been published in the literature. [23][24][25][26][27] This kind of polycondensation on liposomes is based on the interaction between amino acid derivatives and the lipidic surface. This type of interaction was proposed to be central in prebiotic chemistry and precellular, chemical evolution.…”