Shuichi Osanai

Effects of complexation between liposome and poly(malic acid) on aggregation and leakage behaviour

The design and development of novel pH-sensitive liposomes were investigated to improve the release of liposome-encapsulated chemicals. Stable liposomes comprising of L-alpha-dipalmitoylphosphatidylcholine (DPPC) and poly(carboxylic acid) were prepared and characterized. Poly(malic acid) (PMLA) was chosen as a fusogen, because of its excellent biodegradability in physiological regions. Octyl groups introduced in the poly(malic acid) worked as anchors at the surface of the liposomes and made a remarkable contribution to complexing. The interaction between the liposomes and the polyacids was studied in terms of the change in size of the liposomes. The influences of molecular weight and amounts of polymer upon their characteristics, especially fusion, were discussed. The influences of pH change with respect to the association behavior of the liposomes such as aggregation and fusion were estimated by the particle size of the liposomes, turbidimetry of the solution and resonance energy transfer assay. From the results of these studies, it was shown that more tightly complexed liposomes aggregated and fused more positively with increasing acidity of the solution. The leakage of calcein entrapped in the inner aqueous phase of the liposomes increased with decreasing pH. The effect of pH on the liposome aggregation in a solution qualitatively paralleled that found in the leakage behavior.

Generation of an optically active octahedral cobalt complex by a chiral autocatalysis

Abstract Optically active cis-[CoBr(NH3)(en)2]Br2 could be readily obtained by the reaction of optically inactive [Co(H2O)2{(OH)2Co(en)2}2](SO4)2 with ammonium bromide in a water suspension. The optically active cis-[CoBr(NH3)(en)2]Br2 was not readily racemized in its aqueous solution, indicating it not to be produced by total spontaneous resolution but by asymmetric synthesis. This synthesis was exclusively observed when the weight ratio of[Co(H2O)2{(OH)2Co(en)2}2](SO4)2 to water was above 0.31. Since the crystal of each enantiometer of cis-[CoBr(NH3)(en)2]Br2 introduced into the reaction system lead to the preferential production of the same enantiomer, chiral autocatalysis was shown to be performed during the reaction. In the concentrated suspension, crystallization of cis-[CoBr(NH3)(en)2]Br2 that was produced by the reaction would be started during the relatively early stage of the reaction. If several crystals to be initially produced are enantiomerically unequivalent by statistical fluctuation, it may cause the spontaneous generation of the enantiomeric predominance.

Aldose epimerization by Ni(II): effect of ether-containing alkylenediamine ligands

Abstract Several N -substituted ethylenediamine (en) Ni(II) derivatives containing ether linkages were prepared in order to study the effect of ligand structure on C-2 epimerization of aldohexoses. The reagent consisted of a Ni(II)-alkylenediamine derivative in methanol. The presence of ether linkages in the ligand increased the solubility of the complexes, and resulted in an increase in the rate of epimerization. Epimerization occurred rapidly under mild conditions, and the same equilibrium point was reached regardless of whether the reaction was started from glucose or mannose. Among the ligands studied, N , N ′-dialkylethyl-enediamine was the most active in C-2 epimerization.

Intra-Complex Energy Transfer of Europium(III) Complexes Containing Anthracene and Phenanthrene Moieties

Laser excitation and luminescence studies were carried out for an ethanol solution of tris(hexafluoroacetylacetonato)europium(III), Eu(hfac)(3)(H(2)O)(2) (1), and n-hexane solutions of tris(hexafluoroacetylacetonato)europium(III) bis(9-diisopropylphosphorylanthracene), Eu(hfac)(3)(DiPAnO)(2) (2), and tris(hexafluoroacetylacetonato)europium(III) bis(2-diisopropylphosphorylphenanthrene), Eu(hfac)(3)(DiPPheO)(2) (3). The absorption spectra of 2 and 3 in n-hexane are interpreted by assuming that the central Eu(III) ion weakly interacts with the DiPAnO and DiPPheO moieties. The emission spectroscopic studies revealed that (1) Eu(hfac)(3)(DiPAnO)(2) emits only fluorescence from the DiPAnO moiety and (2) Eu(hfac)(3)(DiPPheO)(2) gives luminescence from the central Eu(III) ion, and (3) Eu(hfa)(3)(H(2)O)(2) and Eu(hfac)(3)(DiPPheO)(2) afford emission from both the (5)D(1) and (5)D(0) states of the Eu(III) ion upon 355 nm laser excitation. The intracomplex energy transfer processes are presented on the basis of absorption, emission and laser excitation studies.

Nickel(II)-Catalyzed Rearrangements of Free Sugars

C-2 Epimerization of aldoses and ketoses catalyzed by the Ni(II) complex is described. Both epimerization and the preparation of side-chained sugars proceed in the ternary nickel complex through stereospecific rearrangement of the carbon skeleton, that is, from (1-13C)-D-glucose into (2-13C)-D-mannose and from (2-13C)-D-fructose into (2-13C)-D-hamamelose, and vice versa. The structure of the ligand in the complex plays an important role during the epimerization. The epimerization proceeds more smoothly in both methanolic and aqueous solutions with a more hydrophobic ligand such as N,N′-higher alkylated ethylenediamine. Due to their ability to self-aggregate in water, the organized metallomicelles can provide an appropriate reaction system for the epimerization of aldoses. The chirality of the ligand contributes to the shift of the equilibrium between the two C-2 epimers.

FORMATION OF THE INTERMEDIATE, AQUOHYDROXOBIS (ETHYLENEDIAMINE)COBALT(III) COMPLEX, IN THE PREPARATION OF CIS-BROMOAMMINEBIS (ETHYLENEDIAMINE)COBALT(III) BROMIDE BY THE REACTION OF BIS[BIS(ETHYLENEDIAMINE)COBALT(III)-μ-DIHYDROXO]DIAQUOCOBALT(II) SULFATE WITH AMMONIUM BROMIDE IN WATER

Abstract The production of cis-[CoBr(NH3)(en)2]Br2 by reaction of [Co(H2O)2{(OH)2Co(en)2}2](SO4)2 with ammonium bromide in water was investigated. The reaction seems to proceed through the intermediate, [Co(H2O)(OH)(en)2]2+, and then convert to the product, cis-[CoBr(NH3)(en)2]2+. This is supported by the observation that the absorption spectrum of the reaction solution immediately after the disappearance of the starting complex was different from that of cis-[CoBr(NH3)(en)2]2+ but was quite similar to that of [Co(H2O)(OH)(en)2]2+. In order to confirm this reaction pathway, cis-[Co(H2O)(OH)(en)2]Br2 was prepared and reacted with ammonium bromide producing the expected complex, cis-[CoBr(NH3)(en)2]Br2.

(+)589-Λ-Amminebromobis(ethylenediamine-N,N')cobalt(III) Dibromide

The absolute configuration of (+)589-cis-[CoBr(C2H8N2)2(NH3)]2+ was confirmed to be Λ. The ethylenediamine five-membered chelate rings take the lel2 conformation. There are N—H⋯Br intermolecular hydrogen bonds with N⋯Br distances from 3.267 (9) to 3.715 (8) A.

Long chain carboxylic acids containing ether linkage. IV. The antibacterial activities of 0-(2-alkylaminoethyl)-3-oxypropionic and N-(2-alkyloxyethyl)-3-aminopropionic acids.

The carboxylic amphoteric surfactants containing ether and substituted amine groups such as 0-(2-alkylaminoethyl)-3-oxypropionic-and N-(2-alkyloxyethyl)-3-aminopropionic acids were synthesized, and their antibacterial activities in terms of growth inhibition ofStaphylococcus aureus andEscherichia coli were examined. The structural effect, such as bonding position of ether and amino groups, and the chain length effect between undecyloxy-, dodecyloxy- and tridecyloxy radicals were examined, but no definite correlation between positional isomers and chain length and antibacterial activities was observed. Furthermore, to study the effect of the increase of the number of ether or amino groups on the antibacterial activities, N-(2-(2-dodecyloxyethyl)-aminoethyl)-3-aminopropionic acid and N-(2-(2-dodecyloxyethyl)oxyethyl)-3-aminopropionic acid were synthesized. Their antibacterial activities were almost as effective as the corresponding amino or ether acids. Moreover aqueous solution of these substituted propionic acids showed better surface activities at pH 4.0, 7.0 and 10.0.

Glass transition behavior of octyl β-d-glucoside and octyl β-d-thioglucoside/water binary mixtures

The lyotropic behavior and glass-forming properties of octyl β-D-glucoside (C8Glu) and octyl β-D-thioglucoside (C8SGlu)/water binary mixtures were evaluated using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). The results clearly indicate that the mixture forms a glass in the supercooling state of liquid crystalline phases such as cubic, lamellar, and smectic. The glass transition temperature (T(g)) of the mixture was strongly dependent on solute concentration, with a higher concentration correlating with a higher T(g). The experimental T(g) was consistent with the predicted value calculated using the Couchman-Karasz equation in both the C8Glu and C8SGlu/water mixtures. The change of heat capacity at T(g) showed the two bending points under variation of concentrations. And the highest temperature of phase transition from lamellar to isotropic solution was observed at around 50% molar concentration. It was expected that non-percolated state of water existed in extremely higher concentration ranges.

Long-chain carboxylic acids containing ether linkage III. The antibacterial and antifungal activities of the amine salts of someB-alkoxypropionic acids

Octylamine, dodecylamine, octadecylamine and triethanolamine salts ofβ-dodecyloxy- andβ-tetradecyloxypropionic acids, without or with one and with two oxyethylene groups between the alkoxy group and the propionic acid group, were prepared and examined as the growth inhibiting agents againstStaphylococcus aureus andPenicillium. Some of them were also tested againstTrichophyton asteroides, T. interdigitale, T. granulosus, Epidermophyton floccosum andMicrosporum canis. The effects of the alkyloxy, oxyethylene and amine groups on antibacterial and antifungal activities were determined. The dodecyl radical was more potent than the tetradecyloxy radical. The enhancing effect of the oxyethylene group was obscure in the amine salts. The most effective amine was dodecylamine and its salt ofβ-dodecyloxypropionic acid showed almost the same effectiveness as that of its mercury salt againstTrichophyton. As for the soluble amine salts, it was confirmed that their surface activities had nothing to do with their antibacterial and fungicidal powers.