The Chiral Bilayer Effect Stabilizes Micellar Fibers

Dihelical fibers several micrometers in length and gels were obtained by spontaneous aggregation of octyl L- and D-gluconamides. The single strands have the thickness of a bimolecular layer. No fibers are formed from the racemate. The tendency of the chiral amphiphiles to aggregate to very long fibers instead of three-dimensional crystals is rationalized with a “chiral bilayer effect”. This effect is caused by the slowness of rearrangements from tail-to-tail hydrophobic bilayers to crystals, in which the molecular sheets are arranged in a head-to-tail fashion. Thermograms which indicate slow rearrangements in ageing gels are also reported

Functionalisation of bolaamphiphiles with mononuclear bis(2,2'-bipyridyl)ruthenium(II) complexes for application in self assembled monolayers

A novel ruthenium(II) polypyridyl complex connected competently to a bolaamphiphile, containing amide linkages to provide rigidity via hydrogen bonding in the monolayer, has been prepared. The ruthenium(II) complexes of this ligand and of the intermediates in the synthesis were prepared by modification of the coordinated ligands, demonstrating the synthetic versatility and robustness of this family of complexes. All ruthenium complexes were characterised by electrochemical and spectroscopic techniques and were found to have similar properties to the parent complex [Ru(bipy)[3]][2][+], and remain versatile photosensitisers, with well-defined properties, despite extensive substitution of the bipy ligand

Light-induced electron transfer from a water-soluble porphyrin to an anthraquinone in the center of bilayer lipid membranes

A bolaamphiphilic anthraquinone was synthesized and embedded in the hydrophobic center of positively and negatively charged vesicle membranes. It cannot be reduced by borohydride, but quenches triplet and singlet excited states of water-soluble Zn-meso-tetramethyl-pyridiniumporphyrinate. The apparent quenching constants were [math]

Lipid Bilayer Fibers from Diastereomeric and Enantiomeric N-Octylaldonamides

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.