title: Comparison of the supramolecular structures of two glyco lipids with chiral and nonchiral methyl-branched alkyl chains from natural sources.
abstract: Two alkyl glycosides with the same type of disaccharide headgroups (melibiose) and different methyl-branched alkyl chains, short chiral [(2R,4R,6R,8R)-2,4,6,8-tetramethyldecyl, extracted from an animal source] and long nonchiral (3,7,11,15-tetramethylhexadecyl, from a plant source), were synthesized. The supramolecular aggregate structure formed in dilute solutions was investigated by small-angle neutron scattering and surface tension measurements. The lyotropic phase diagram was studied by differential scanning calorimetry and water penetration scans. The thermotropic phase behavior was investigated by polarizing microscopy. The compounds showed unusual phase behavior: (i) The liquid-crystalline polymorphism is reduced to only form smectic A phases in the pure state; the formation of lyotropic phases such as hexagonal or lamellar phases was not observed. (ii) The compound with the longer nonchiral alkyl chain is more soluble in water than the one with the shorter chiral chain, most likely because of the different flexibilities of the chains. (iii) For the long-chain compound, the formation of micelles is observed, whereas the short-chain compound forms large disklike/bilayer aggregates. The method of methylation of the chain controls the self-assembly and can explain different biological functions for either plants (variable temperature) or animals (constant temperature).
authors.affiliation: Institute of Organic Chemistry, University of Hamburg, Martin Luther King Platz 6, D-20146 Hamburg, Germany.
authors.forename: Götz
authors.initials: G
authors.lastname: Milkereit
authors.forename: Vasil M
authors.initials: VM
authors.lastname: Garamus
authors.forename: Jun
authors.initials: J
authors.lastname: Yamashita
authors.forename: Masakatsu
authors.initials: M
authors.lastname: Hato
authors.forename: Michael
authors.initials: M
authors.lastname: Morr
authors.forename: Volkmar
authors.initials: V
authors.lastname: Vill
mesh_terms: D000818:Animals; D006017:Glycolipids / Q000138:chemical synthesis / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry*; D015394:Molecular Structure; D010316:Particle Size; D013500:Surface Tension; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D006017:Glycolipids; D046911:Macromolecular Substances; D014867:Water