Concentration of Diynoic Acids in Bicellar Mixtures Derived from Those Phase Separation

Abstract

Bicellar mixtures containing diacetylene molecules, such as diynoic acids, can be used as parent materials for functional membranes. A bicellar mixture consisting of a diynoic acid—10,12-tricosadiynoic acid (TCDA)—, a phospholipid—1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)—, and a detergent—3-[(3-cholamidopropyl) dimethylammonio]-2-hydroxypropanesulfonate (CHAPSO)—was evaluated for its morphology and packing of TCDA molecules in its bicellar mixture. A TCDA/DMPC vesicle was prepared at different molar ratios, TCDA/DMPC = 2/8, 5/5, and 8/2; a TCDA/DMPC/CHAPSO bicellar mixture was prepared by mixing a CHAPSO solution with a TCDA/DMPC vesicle solution as a detergent at different composition ratios, x _TCDA/DMPC = [TCDA/DMPC]/([TCDA/DMPC]+[CHAPSO]), of 1.0, 0.70, 0.50, and 0.30. A DMPC molecule formed a bilayer membrane structure and was used to suppress its precipitation. The packing density of the TCDA/DMPC/CHAPSO bicellar mixtures was increased by mixing a CHAPSO molecule in x _TCDA/DMPC = 1.0 to 0.70 or 0.50. A TEM image of a TCDA/DMPC/CHAPSO bicellar mixture showed many discoidal assemblies at x _TCDA/DMPC = 0.5 of TCDA/DMPC = 5/5. Polymerization of the TCDA molecules in the bicellar mixture by UV light suggested an ordered arrangement of TCDA. Polymerization at x _TCDA/DMPC = 0.70 and 0.50 correlated with improved packing density.

graphical abstract Fullsize Image