Membrane-spanning symmetric and asymmetric diyne amphiphiles

Abstract

Symmetric membrane-spanning diyne amphiphiles of different molecular designs, e.g. single-chain and identical or mixed double-chain compounds, have been synthesized, starting from 10,12-docosadiyne-1,22-diol (1) and 10,12-docosadiynylenedihydrogendimaleate (2), respectively. Esterification of 2 and/or addition of functional thiols at the maleic acid double bond yield symmetric α,ω-dipolar diyne amphiphiles which show structural resemblance to lipids found in the biomembranes of archaebacteria. Asymmetric membrane-spanning diyne amphiphiles are obtained by a straightforward route from 22-hydroxy-10,12-docosadiynoic acid (12) by acylation with functional aromatic dicarboxylic acid anhydrides. Vesicles are formed from a number of symmetric and asymmetric diyne lipid analogues on dispersion in aqueous media, as shown by light- and freeze-fracture electron microscopy and dye entrapment experiments. Stabilization of lecithin liposome membranes towards temperature-induced dye release is effected by incorporation of a macrocyclic membrane-spanning diyne amphiphile. Ultraviolet irradiation of dispersions from asymmetric diynes yields blue and red solutions, indicating that topotactical diacetylene polymerization takes place in these lipid assemblies.