Hiroshi Hachisako

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

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 1H 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 fibrous 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.

Functional organic gels Chirality induction through formation of highly-oriented structure

Abstract An L-glutamate derivative having one carboxylic and two dodecylamide groups form highly-oriented aggregates in benzene, which interact with a cationic achiral dye to produce extremely strong exciton coupling around the absorption band of the dye.

Reversible gelation in cyclohexane of pyrene substituted by dialkyl L-glutamide: photophysics of the self-assembled fibrillar network

Abstract l- Glutamic acid-derived compound with pyrenyl group was able to form organic gels in benzene, cyclohexane, and so on. The gels were produced through the formation of highly oriented aggregates and a remarkable development of their fibrous polymer networks. Our scopes of this study are to present the salient features of the photophysics of pyrene in the highly oriented fibrillar network in cyclohexane and to describe spectroscopic measurements used either to detect pyrene association prior to excitation or to confirm the absence of aggregated pyrenes. The concentration and the temperature affected the gel-formation. The sol in the concentration below critical gel concentration includes nanoassemblies with highly oriented aggregates of the compound. Functionalization of l -glutamide derivative with different head groups using electron accepting pyrene and electron-donating N,N-dimethylaniline (DMA) chromophores was also performed to detect the exciplex formation as the mimicry of the photoinduced electron transfer process in the photosynthesis. Upon cooling from 60 to 10 °C, red shifted fluorescence from 446 to 456 nm ascribed to the charge transfer from DMA to pyrene was observed in the mixed system of pyrene- and DMA-containing l -glutamide derivatives in cyclohexane.

Novel self-assembling organogelators by combination of a double chain-alkylated L-glutamide and a polymeric head group

This communication introduces a new class of self-assembling organogelators composed of a double chain-alkylated L-glutamide with a polymeric head group.

Specific bindings of methyl orange to chiral bilayer membranes with β-alanyl-L-glutamoyl head groups [1]

Abstract Interactions between methyl orange and cationic bilayer membranes constructed from a dialkyl amphiphile with a β-alanyl-L-glutamoyl head group were investigated. The chiral bilayers undergo a gel to liquid crystal phase transition to give rise to the reversible chirality change from - 8 × 104 to + 11 × 104 deg cm2 dmol−1 near the phase transition temperature. Methyl orange combines with the cationic membranes to give three kinds of spectra, belonging to the surface-oriented chiral dimer and the monomer and incorporated achiral monomer, in response to the phase transition of the bilayer membrane.

Functional organic gels. Enantioselective elution using chiral gels from amino acid-derived lipids

Abstract The L-glutamic acid-derived lipids form organic gels in benzene, which show enantioselective elution of N-dansyl L-phenylalanine from organic gels to aqueous phases. Differential scanning calorimetry and circular dichroism measurements demonstrate that this enantioselectivity occurred through highly-oriented structures of aggregated lipids like those of aqueous lipid membrane systems.

Chirally arranged monomeric dyes on helical bilayer membranes

Abstract Strong exciton coupling around the absorption band of monomeric dyes was induced by helical bilayer membranes formed from various L-glutamic acid-derived amphiphiles which contain three amides per molecule. The mirror-image of the circular dichroism spectra was observed by the corresponding D-isomers. No similar induction was observed by the corresponding ester-type amphiphiles which could not produce helices. It is assumed that dyes are helically arranged on helical bilayer membranes, resulting in an induction of chirality even in monomeric dyes.

Thermal isomerization process in benzene gels of l-glutamic acid-derived lipids with spiropyran head groups

First-order kinetic behaviour during the thermal isomerization process of lipids with photochromic spiropyran head groups in benzene strongly depends on the dispersion state of the lipids and this enables the determination of their critical aggregation concentrations.

Supramolecular receptors from α-amino acid-derived lipids

Anionic lipids derived from L-, D-, DL-glutamic acids, L-aspartic acid, L-lysine, L-ornithine, and L-2,4-diaminobutyric acid were prepared and the way in which structurally related, solvatochromic cationic styryl dyes were incorporated into these lipid aggregates were investigated. The L- or D-glutamic acid-derived lipids with glutaric acid headgroups aggregated to form specific hydrophobic cavities which exhibited inclusion ability for the styryl dyes mainly based on the planarity recognition. The formation of such specific hydrophobic cavities can be achieved not only by introducing amide groups capable of complementary hydrogen bondings between neighbouring lipids in the aggregates but also by introducing appropriate spacer methylenes into, for example, glutarate headgroups. Side-chain methylenes of the amino acid residue were also found to play a significant role in the formation of specific hydrophobic cavities as well as the spacer methylenes. Such cavities were also formed for appropriately designed L-lysine- and L-ornithine-derived lipids. These results indicate that the specific incorporation is not peculiar to the glutamic acid-derived lipids but a general phenomenon for the aggregates from appropriately designed L-amino acid-derived lipids. A difference in the manner of assembly of L-glutamic acid residues between L-, D-isomers, and DL-mixtures in the lipid aggregates is suggested not only by the λmax shift of incorporated styryl dyes but also by aggregate morphologies as evidenced by the TEM observations. These results suggest that the two-dimensional assembly of pure enantiomeric α-amino acid residues in appropriately designed lipids can produce specific hydrophobic cavities unless the DL-mixture phase-separates into two enantiomeric components.

Lipid membrane analogues. Formation of highly-oriented structures and their phase separation behaviour in benzene

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.