Kazuo Ohbu

Effect of quaternary ammonium substitution of hydroxyethylcellulose on binding of dodecyl sulfate

The binding behavior of sodium dodecyl sulfate (SDS) to quater-nary ammonium substituted hydroxyethylcellulose (cationic cellu-lose) of varying degree of substitution was studied by the following measurements: binding isotherms of SDS to cationic cellulose, dye solubilization of the cationic cellulose/SDS complex, partial molal volume of each cationic cellulose, and spin-lattice relaxation time of SDS protons in the course of binding. Binding isotherms showed features similar to that observed for the globular protein/SDS system. The molecular processes of complex formation between cationic cellulose and SDS is discussed based on these results.

Effect of alkali metal ions on gel formation in the 12-hydroxystearic acid/soybean oil system

It has been known that 12-hydroxystearic acid (12HSA) forms a thermoreversible gel with a fibrous associated network in organic solvents. Mechanically durable gels were induced by the addition of small amounts of alkali metal ions, which can be supplied in the form of alkali metal salts of 12HSA (abbreviated as 12HS-M), even at a lower concentration range of gelling agent than with 12HSA alone. The structure of the networks was investigated by infrared spectrometry (IR), circular dichroism (CD) and scanning electron microscopy (SEM). The experiments were carried out over a total concentration range of 0.1≈4.0 wt/vol% of 12HSA and 12HS-M in soybean oil. 12HS-Na showed more effective gel forming power than any other alkali metal ions. The molar ratio of 12HSA/12HS-Na for obtaining optimal gel forming effect was 100:1. The intensity of the absorption bands of the IR spectra, due to the hydrogen-bonded hydroxyl groups, remained constant regardless of the amount of added 12HS-Na. A remarkable molar ellipticity decrease was observed with an increase in the concentration of 12HS-Na, although the maximum wavelength of the CD spectrum, originating from the chirality of 12HSA, remained constant. By SEM observation, linearly extended fibrils were observed with the addition of 12HS-Na. These results suggest that the mechanical trengthening of the gel by alkali metal ions is due to alteration of the dispersed state of the helically grown fibrous crystals of 12HSA.

Formation of fractal porous silica by hydrolysis of TEOS in a bicontinuous microemulsion

Abstract Mesoporous silica particles have been prepared by hydrolysis of TEOS (Si(OC2H5)4) in bicontinuous microemulsions containing polyoxyethylene (POE) dodecylether, isooctane and water. TEOS was dissolved in a continuous water phase and hydrolyzed by the dispersed water at around the phase inversion temperature (60°C). Undulating solid materials with layered mesostructures were produced from middle-phase microemulsions in the three phase region (o/w=0.2–0.7). On the other hand, the solids obtained from the lower aqueous phase in the three phase region were found to have a heterogeneous disordered structure. Measurements of the fractal dimensions were performed in the macropore region using a box-counting method for the outline of the SEM texture. We found that the macropore size distribution in the particles prepared from the middle-phase microemulsion follows the fractal rule with a dimension of 1.7. From the results of nitrogen adsorption/desorption curves on the silica, a steep increase in the adsorption amounts was observed at a relative pressure below 0.2, and adsorption/desorption hysteresis was also observed at a relative pressure between 0.3 and 0.5. These studies suggest that the silica synthesized in the bicontinuous microemulsion mesostructure has a very broad size range from micro to macropores with a fractal distribution.

Crystal structures of methyl 6-O-n-alkanoyl-β-d-glucopyranosides

Abstract The crystal structures of methyl 6-O-n- octanoyl -β- d - glucopyranoside 1 and methyl 6-O-n- decanoyl -β- d - glucopyranoside 2, which are types of glycosurfactants, were determined by X-ray analysis. Anhydrous crystals were obtained from a diethyl ether-acetone solution. The crystals are monoclinic, and the space group is P21 with Z = 2. The cell dimensions are as follows: 1, a = 7.760(1), b = 7.373(1), c = 15.514(1) A , β = 102.91(1)° ; 2, a = 7.724(1), b = 7.351(1), c = 16.957(2) A , β = 94.81(1)° . The glucopyranoside moieties are in a 4C1 chair conformation and the conformation of the alkyl chain is the all-trans type. The molecules are arranged parallel to the a–c plane in a bilayer structure where alkyl chains are interdigitated. The sugar moieties are stacked to form a hydrophilic zone elongated parallel to the ab plane and arranged with a packing structure similar to that of methyl β- d -glucopyranoside in spite of a substituted long alkyl chain. Hydrogen bondings of sugar moieties are found only between the bilayers.

A study on the adsorption of dialkyldimethyl ammonium chloride

A study was made on the structure, adsorption behavior toward fabrics and dependence upon particle size of an aqueous dispersion of di(hydrogenated tallow)dimethyl ammonium chloride (purified Arquad 2HT), the most widely used softener base. From the results of analyses by X-ray diffraction, differential scanning calorimetry (DSC) and electron microscopy, it was found that the dispersed phase of Arquad 2HT dispersion consisted of hydrated particles having a similar structure to that of the multilayered liposomes (or vesicles) of phospholipids and that these particles were adsorbed onto fabrics by softening treatment It was also found that finely dispersed particles showed better softening and antistatic performances in addition to a superior storage stability, due to their higher rate and uniformity of adsorption compared to roughly dispersed particles.

Polyacrylamide gel electrophoresis of several proteins in the presence of sodium oligooxyethylene dodecyl ether sulfates or a commercially available analog

The behavior of water-soluble proteins and a typical membrane protein in polyacrylamide gel electrophoresis was studied in the presence of sodium oligooxyethylene dodecyl ether sulfates with a defined number of oxyethylene units or a commercially available analog with distribution and heterogeneity for the oxyethylene chain length and alkyl group, respectively. It was concluded that most water-soluble proteins do not interact with the anionic surfactants as long as their oxyethylene chain lengths are sufficiently long; the commercially available surfactant binds exceptionally well to beta-lactoglobulin without causing denaturation and subsequent dissociation; such surfactants are expected to solubilize membrane proteins without causing denaturation as judged from the result with Na+,K+-ATPase and are promising as new solubilizing agents for membrane proteins which enable efficient electrophoretic analysis or separation after the solubilization.

Crystal structures of methyl 6-O-acyl-α-d-galactopyranosides

Abstract The crystal structures of methyl 6-O- n-octanoyl -α- d -galactopyranoside (1) and methyl 6-O- n-decanoyl -α- d -galactopyranoside (2) were investigated by X-ray analysis. Anhydrous crystals obtained from methanol solution by slow evaporation are monoclinic, and the space group is P21 with Z = 2. The cell dimensions are as follows, 1: a = 5.774(1), b = 8.013(1), c = 19.183(1) A , β = 98.50(1)°; 2 : a = 5.762(1), b = 8.003(1), c = 21.227(2) A , β = 93.93(1)° . The galactopyranoside ring is nearly in a 4C1 chair conformation but slightly distorted to twist boat and the alkyl chain is in all-trans conformation. In these crystals, molecules are arranged in a bilayer structure with interdigitated alkyl chains. The hydrogen bonding linkages between sugar moieties, which are found only between the layers, form an infinite chain through the crystal. 1 and 2 show higher melting points than those of corresponding β- d -glucopyranosides. The results indicate the important role of the sugar in the crystal.

Bilayer structure of glycolipid crystals. Thermal stability of the crystal and state of the alkyl chain

The role of alkyl chains in the stabilization of a bilayer structure of glycolipids in the crystalline state has been studied for a series of methyl 6-O-acyl-β-D-glucopyranosides and methyl 6-O-acyl-α-D-galactopyranosides. Thermal properties and crystal structures of these glycolipids with an odd number of alkyl carbon atoms in the acyl moiety have been investigated by thermal analysis and X-ray methods. The melting temperatures of methyl 6-O-acyl-β-D-glucopyranosides, which are lower than those of the corresponding methyl 6-O-acyl-α-D-galactopyranosides, decrease with increasing number of alkyl carbon atoms from one to seven, but increase for longer alkyl chains. The α-galactosides show only a monotonic decrease in melting temperature with increasing alkyl chain length. In the crystals, the molecules form a bilayer structure with interdigitated alkyl chains. The arrangement of sugar moieties in the crystals differs between the β-glucosides and the α-galactosides, but they are almost the same among sugar derivatives with various alkyl chain lengths. The packing of the acetyl moiety in a crystal of methyl 6-O-α-D-galactoside is different from that of the other α-galactoside derivatives with longer alkyl chains. The carbonyl oxygen atom causes steric hindrance with adjacent alkyl chains, and such unfavorable intermolecular contact explains the relatively low thermal stability of the crystal. On the other hand, the contribution of the β-glucoside to thermal stability is ascribed to the well-ordered packing of the long alkyl chain moiety.

Light scattering study on the micellar systems solubilizing a fatty acid

The effect of oleic acid on the aggregational behavior of the α-sulfonated fatty acid methyl ester sodium salt (α-SFMe) and sodium linear C12/C14-alkylbenzene-sulfonate (LAS) has been studied using a light-scattering method. The solubilizing capacity of α-SFMe was larger than that of LAS, and depended both on the number of micelles in the surfactant solution and the solubilized amount per micelle.When the micellar weights for the α-SFMe and LAS systems were determined at the various oleic acid/surfactant ratios, the micellar weights initially decreased by small amounts of solubilizate and then increased with the further increase in the solubilized amounts. It was found that the solubilization process is accompanied by a reconstitution of the micelles.

Crystal structures of glycolipids with odd and even numbered alkyl chains

The effect of the alkyl chain on the thermal stability of crystals for a series of glycolipids, methyl 6-O-alkanoylglycopyranosides, was investigated using thermal analysis, X-ray structures and molecular mechanics. Glycolipids with two types of sugar moieties, α-galactopyranoside and β-glucopyranoside carrying an alkyl chain with various numbers of carbon atoms, 1–11, and 1–13, respectively, were used for the analyses. All the crystals have bilayer structures with interdigitated alkyl chains. The crystal packing is significantly affected by the sugar moieties but the same for individual sugar derivatives for a variety of alkyl chain lengths. Alkyl chains with an even number of carbon atoms in the α-galactoside derivatives have temperature factors (thermal parameters) which are higher than those for alkyl chains with an odd number of carbon atoms. Alkyl chains with an even number of carbon atoms in the β-glucosides have a disordered structure with two alternate conformations while the remaining derivatives have well ordered alkyl chains. The mean lengths of the hydrogen bonds in the β-glucosides with an even number of carbon atoms in the alkyl chain are longer than those with an odd number of carbon atoms, but a slight difference only is observed in the α-galactosides. The thermal stability of the α-galactosides with an odd number of carbon atoms in the alkyl chain is higher than that of α-galactosides with an even number of carbon atoms. On the other hand, the opposite behavior is observed for the β-glucosides. The difference in the melting points between β-glucosides with an odd and even number of carbon atoms in the alkyl chain is greater than the difference for the corresponding α-galactosides. The difference in the thermal stability is suggested to be related to the packing of the sugar moieties in the crystal based on molecular mechanics calculations.