Detection of highly oriented aggregation of L-glutamic acid-derived lipids in dilute organic solution

Abstract

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.

Polymer functionalization by luminescent supramolecular gels

“…Supramolecular gels involve a minimum concentration required to form a physical gel state, which is known as the critical gelation concentration. 22 However, supramolecular gels visually appear to be in a solution state at concentrations below this and thus are often referred to as manifesting supramolecular functionality. This is because there is generally a minimum concentration required for molecules to aggregate, known as the minimum aggregation concentration.…”

“…22,[30][31][32][33][34][35][36][37][38][39][40][41][42][43] When the functional group is hydrophilic, such as an amino (G-C 2 -NH 2 ) or pyridinium (G-C 2 -Py + ) group (Figure 3), the glutamide will form tubular and helical bilayer membranes in polar solvents such as water 31,44-46 and acetonitrile. 46 However, the glutamide forms fibrous aggregates in nonpolar solvents such as benzene, and the solution gels at concentrations above the critical gelation concentration.…”

Self‐Assembled Nanofibrillar Aggregates with Amphiphilic and Lipophilic Molecules

“…Peptide-based organogelators have a plural number of hydrogen bondable moieties. 10 [28,31] as a typical example possesses three amide bonds around an L-glutamic moiety, which works as a good organogelator. TEM and SEM observations showed a three-dimensional network with fibrillar aggregates in its organogel and xerogel.…”

“…The minimum diameter of the aggregates in the picture is 20 nm, which is 2-3 times larger than the molecular length estimated by SAXS. [31] However, if two of the three amide bonds are replaced by the ester bonds, no gelation is observed even when their concentration is 10 times higher than former. It was also confirmed that addition of trifluoroacetic acid as an inhibitor for hydrogen bonding causes gel-to-sol transition.…”

“…Spectroscopic observations provide information on molecular orientations, packing states and lateral diffusion behavior. UV-visible, [19,27,[31][32][33][34] Fourier transform infrared (FT-IR), circular dichroism (CD), [8,9,19,31,[34][35][36] fluorescence [37,38] and nuclear magnetic resonance (NMR) [39] spectrometers have been widely used for investigation and analysis on the molecular orientation. Typical investigations are found in chromophore-containing lipid systems.…”