Tadamasa Terai

Characteristics of the charge transfer surface complex on titanium( iv ) dioxide for the visible light induced chemo-selective oxidation of benzyl alcohol

This paper deals with the oxidation of benzyl alcohol by O2 on pure TiO2 under visible light irradiation, and it was found that the benzyl alcohol is converted into benzaldehyde with high selectivity (>99%). In order to understand the origins of the visible light induced photocatalysis, surface characterizations of the charge transfer complex formed by the interaction of benzyl alcohol with the TiO2 was extensively performed by investigating the effect of heat-treatment on TiO2 or its chemical modification with hydrofluoric acid. Moreover, the study of the kinetic isotope effect (KIE) for the oxidation of benzyl alcohol showed that the α-deprotonation from benzyl alcohol is the rate determining step (RDS), the process of which is assisted by the terminal OH groups of TiO2. Photo-electrochemical investigations were also incorporated to demonstrate the reaction mechanism behind the visible light induced photocatalytic reaction.

Ethyl esterification of docosahexaenoic acid in an organic solvent-free system with immobilized Candida antarctica lipase

Ethyl docosahexaenoate (EtDHA) is regarded as a potentially useful pharmaceutical substance on account of its beneficial physiological activities. We attempted the ethyl esterification of docosahexaenoic acid (DHA) in an organic solvent-free system using Candida antarctica lipase, which acts strongly on DHA and ethanol. Esterification of 88% was attained by shaking a mixture of DHA/ethanol (1:1, mol/mol) and 2 wt% immobilized C. antarctica lipase at 30 degrees C for 24 h. However, even in the presence of an excess amount of ethanol, the extent of esterification could not be raised above 90%. To attain a higher level of esterification, a two-step reaction was found to be effective. The first step was performed in a mixture of DHA/ethanol (1:1, mol/mol), and the reaction mixture was then dehydrated. In the second step, the resulting mixture was shaken at 30 degrees C for 24 h with 5 molar equivalents of ethanol against the remaining DHA using 2 wt% immobilized lipase. By means of this two-step procedure, 96% esterification was attained. Repetition of the first and second reactions showed that the immobilized lipase was reusable for at least 50 cycles. In addition, DHA remaining in the second-step reaction mixture was removed by a conventional alkali refining process, giving purified EtDHA with a high yield.

Purification and characterization of a novel cholesterol esterase from Pseudomonas aeruginosa, with its application to cleaning lipid-stained contact lenses.

With the aim of developing a new cholesterol esterase for eliminating lipids on used contact lenses, microorganisms were screened for the enzyme activity. A Pseudomonas aeruginosa isolated from soil was found to produce a desirable enzyme. The enzyme had an isoelectric point of 3.2, and molecular mass of 58 kDa. The optimal temperature was around 53°C at pH 7.0, and the optimal pH was from 5.5 to 9.5. The enzyme was stable between pH 5 and 10 for 19 h at 25°C, and retained its activity up to 53°C on 30 min of incubation at pH 7.0. The rates of hydrolysis of cholesteryl esters of different fatty acids were in the following order: linoleate>oleate>stearate>palmitate>caprylate>myristate> laurate, caprate>caproate>butyrate, acetate. Addition of (tauro)cholate to a final concentration of 100 mM markedly promoted the hydrolysis of triglycerides of short-, medium-, and long-chain fatty acids. When used with taurocholate, the enzyme acted as an effective cleaner for contact lenses stained with lipids consisting of cholesteryl oleate, tripalmitin, and stearyl stearate.

Enzyme-catalyzed synthesis of a bioactive oligopeptide in nearly anhydrous solvents with polyethylene glycol-modified proteases

An oligopeptide, L-arginyl-glycyl-L-aspartyl-L-serine, having cell attachment activity was synthesized from the respective aminoacids carrying suitable protecting residues, by using carboxymethyl polyethylene glycol (PEG)-modified proteases in organic solvents. Papain, trypsin, and alpha-chymotrypsin were modified with PEG. Organic solvents used were 1,1,1-trichloroethane, chloroform and chloroform/ethyl cellosolve (1:1) mixture. Identification of the products was done by gel permeation chromatography (GPC) and thin layer chromatography (TLC).

Crystal and molecular structure of 10,20-epoxy-grayanotoxin-II

The photooxidation with HgO in benzene and the hydrolysis with 2%-KOH in methanol of the grayanotoxin (GTX) derivative (4) gave a 10,20-epoxy-grayanotoxin-II(5). The crystal structure of (5) has been determined by X-ray diffraction at room temperature. The crystal is monoclinic, space group P21, with a = 14.248(10) Å, b = 6.670(10) Å, c = 9.990(10) Å, α = 105.507(8)°, V = 914.9(2) Å3, Z = 2. The structure was solved by direct methods and refined by full-matrix least squares methods to a final R1 = 0.046 (wR2 = 0.0833) for 1161 independent reflections. The molecule has a pentacyclic structure consisting of two five-membered, one six-membered, one seven-membered, and one three-membered rings. The three-membered ring is connected with the seven-membered ring by spiro-type bond.

Crystal and molecular structure of grayanotoxin VII

The crystal and molecular structure of a grayanotoxin VII is presented. The crystal is monoclinic, space group P21, with a = 7.647(1) Å, b = 11.7591(7) Å, c = 10.0873(6) Å, β = 91.143(8)°, V = 906.9(1) Å3, Z = 2. The structure was solved by direct methods and refined by full-matrix least-squares methods to a final R = 0.057 for 1494 independent reflections. The molecule has a tetracyclic structure consisting of two five-membered, one six-membered, and one seven-membered rings.

Crystal and molecular structure of a new diterpenyl glycoside from Pteris cretica L.

The crystal and molecular structure of a new diterpenyl glycoside, Ptr-1, is presented. The crystal is triclinic, space group P1, with a = 8.2414(8) Å, b = 13.0826(9) Å, c = 6.1427(8) Å, α = 95.345(9)°, β = 111.589(8)°, γ = 96.726(7)°, V = 604.9(1) Å3, Z = 1. The structure was solved by direct methods and refined by full-matrix least-squares methods to a final R = 0.049 (Rw = 0.099) for 1872 independent reflections. The molecular structure is based on a glycopyranosyl group and a tetracyclic group. The glycopyranosyl group is β-D-allopyranosyl group. The tetracyclic group consists of 1 five-membered and 3 six-membered rings.

Crystal and molecular structure of iso-grayanotoxin II

AbstractThe crystal and molecular structure of a grayanotoxin derivative, iso-grayanotoxin II, is presented. The crystal is orthorhombic, space group

Enzymatic Synthesis of Steryl Esters of Polyunsaturated Fatty Acids

P2_1 2_1 2_1 ,{\text{ with }}a{\text{ = 12}}{\text{.357(1) }}{\AA}{\text{, }}b{\text{ = 23}}{\text{.354(1) }}{\AA}{\text{, }}c = 6.284(2){\text{ }}{\AA}{\text{, }}V = 1813.3(6)\,{\AA}^3 {\text{, }}Z = 4