Lipid bilayer fibers from diastereomeric and enantiomeric N-octylaldonamides

Abstract

The aggregation behavior of eight diastereomeric N-octylaldonamides, three enantiomers (galacton, mannon, glucon), and corresponding racemates was investigated mainly by electron microscopy. Head groups with a sterically undisturbed all-anti conformation (galacton, mannon) lead to "whisker"-type aggregates, which appear as rolled up, bilayer sheets in both aqueous and 1,2-xylene gels. One pair of 1,3-syn-positioned OH groups in the all-anti conformation neighboring on the amide group, lead to extremely thin helical whiskers of high curvature in water (glucon) or 1,2-xylene (talon). If the outer OH groups are in syn positions in the all-anti chain conformations, the N-octylamides become highly water-soluble (allon, altron, idon) and form rolled up, bilayer sheets in 1,2-xylene (gulon). The length-to-diameter ratios in the aggregates are often higher than 10^4. The fibers are stabilized by amide hydrogen bonds and/or the hydrophobic effect. They can be conceived as models for prebiotic assemblies, which may lead to condensation biopolymers in aqueous media.