A double-chain alkyl lipid with an isoquinoline-containing headgroup was derived from L-glutamide. This worked as an organogelator in benzene, cyclohexane, a cyclohexanes-ethanol mixture, and so forth. Transmission electron microscope observation showed that the gelation was brought about through the formation of a fibrillar network, and circular dichroism (CD) spectra indicate that the fibrillar aggregates were based on highly ordered structures. The critical aggregation concentration (cac) was estimated by detecting the enhancement of CD strength due to molecular orientation. The cac's were dependent on solvents and always lower than the critical gelation concentration. This indicates that the sol state includes supramolecular aggregates inside which the lipids are well developed. In addition, it was confirmed that the chirality and morphology of the aggregates are remarkably perturbed by chelating with metal chlorides. In the case of CuCl2 which can form a square planar coordination, the chirality enhancement was observed, but in the case of CoCl2 and ZnCl2 which can form an octahedral coordination state, serious morphological change was observed with remarkable decrease of the chirality.
Aggregation structures in organic gels and xerogels formed from l-glutamic acid-derived lipids were investigated by scanning and transmission electron microscopies, X-ray analyses, and 1 H NMR and IR spectroscopic methods. These analyses showed that the gels were produced through the formation of highly oriented aggregates based on a single layer and a remarkable development of their ® brous morphology. We also describe how the critical aggregation concentration can be observed at a concentration below the critical gel concentration by using a dye-complexation method with a cyanine dye, NK-77.
L-Glutamate derivatives 1 and 2 having two N-dodecylamide groups formed highly-oriented aggregates in benzene, which underwent phase transition and phase separation behaviours analogous to those of lipid membranes.
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