Kinetic Study on Alpha-Form Crystallization of Mixed-Acid Triacylglycerols POP,PPO, and Their Mixture

The crystallization behavior of the metastable α form of triacylglycerols (TAGs) plays a critical role as a precursor for the crystallization of more stable β′ and β forms for various applications in food and pharmaceutical products. However, precise analysis of the crystallization kinetics of α has not been performed, likely due to its rapid and complex behavior. This paper presents the observation results of the initial stages of the isothermal crystallization kinetics of α forms of 1,3-dipalmitoyl-2-oleoyl-glycerol (POP), 1,2-dipalmitoyl-3-oleoyl-rac-glycerol (rac-PPO), and molecular compound (MC) crystals of a POP/rac-PPO (1/1) mixture (MCPOP/PPO) using synchrotron radiation time-resolved X-ray diffraction and polarized optical microscopy. In all the TAGs, α crystals with a worm-like morphology started to grow rapidly in the first stage. Then, the α crystals slowly transformed into more stable forms in different manners for different TAG samples. In POP, the conversion was simple, as the α-2 form transformed into γ-3, whereas in rac-PPO, the lamellar distance values of the α-2 form continuously decreased with time and changed into the α-3 form. In the MCPOP/PPO crystals, in contrast, separate crystallization of α-2 of a rac-PPO fraction initially occurred, followed by the crystallization of α-2 of POP, and the two α forms merged into α-2 of MCPOP/PPO. This separate crystallization was caused by large differences in the crystallization kinetics of the α forms of POP and rac-PPO.     

Chalcogenide-Lewis acid mediated reactions of electron-deficient alkynes with aldehydes

Reactions of but-3-yn-2-one (2) with aldehydes 1 in the presence of a Lewis acid and dimethyl sulfide (3 a) predominantly gave (E)-alpha-(halomethylene)aldols 4-5 in high yields, while reactions of methyl propiolate (6 a) mainly afforded (Z)-3-halogeno-2-(hydroxymethyl)acrylates 7-8 in low to moderate yields. A reaction of dimethyl acetylenedicarboxylate (10) with 1 a in the presence of TiCl(4) and 1,1,3,3-tetramethylthiourea (3 c) produced maleate (E)-11 (40 %) and butenolide 12 (40 %). When a reaction of 6 a with 1 a was carried out in the presence of TiBr(4) and 3 a (0.2 equiv) at -20 degrees C for 60 h, 3-(methylthio)-2-(hydroxyalkyl)acrylate 9 a was obtained in an 8 % yield. Experiments were conducted in order to elucidate the formation mechanism of 9 a, and it was made clear that 9 a was formed via the processes of the Michael addition of sulfide 3 a to alkynoate 6 a and an aldol reaction with 1 a and demethylation.     

Novel immobilized zinc(II) affinity chromatography for phosphopeptides and phosphorylated proteins

Immobilized metal ion affinity chromatography (IMAC) is now a widely accepted technique for the separation of natural or artificial products that is beginning to find industrial applications. Here, we introduce a novel procedure for the separation of phosphopeptides and phosphorylated proteins by immobilized zinc(II) affinity chromatography. The phosphate-binding site of the affinity gel is an alkoxide-bridged dinuclear zinc(II) complex, the 1,3-bis[bis(pyridin-2-ylmethyl)amino]propan-2-olato dizinc(II) complex (Phos-tag), which is linked to a highly cross-linked 4% (w/v) agarose. The affinity gel (Phos-tag agarose) was prepared by the quantitative reaction of N-hydroxysuccinimide-activated Sepharose and a Phos-tag derivative having a 2-aminoethylcarbamoyl group in dry CH3CN. Phosphopeptides were retrieved in a quantitative and highly selective manner by a spin column method using Phos-tag agarose at room temperature. Furthermore, in this study, we demonstrate a simple, rapid, and reusable affinity column chromatography for the separation of phosphorylated proteins such as ovalbumin, alpha(s1)-casein, and beta-casein at physiological pH.     

Significant efficiency improvement of the black dye-sensitized solar cell through protonation of TiO2 films

This paper describes the influence of acid pretreatment ofTiO2 mesoporous films prior to dye sensitization on the performance of dye-sensitized solar cells based on [(C4H9)4N]3[Ru(Htcterpy)(NCS)3] (tcterpy = 4,4',4"-tricarboxy- 2,2',2"-terpyridine), the so-called black dye. The HCl pretreatment caused an increase in overall efficiency by 8%, with a major contribution from photocurrent improvement. It is speculated, from the analysis of incident photon-to-electron conversion efficiency, UV-vis absorption spectra, redox properties of the dye and TiO2, and the impedance spectra of the dye-sensitized solar cells, that photocurrent enhancement is attributed to the increases in electron injection and/or charge collection efficiency besides the improvement of light harvesting efficiency upon HCl pretreatment. Open-circuit photovoltage (V(oc)) remained almost unchanged in the case of significant positive shift of flat band potential for TiO2 upon HCl pretreatment. The suppression of electron transfer from conduction band electrons to the I3- ions in the electrolyte upon HCl pretreatment, reflected by the increased resistance at the TiO2/dye/electrolyte interface and reduced dark current, resulted in a V(oc) gain, which compensated the V(oc) loss due to the positive shift of the flat band. Using the HCl pretreatment approach, 10.5% of overall efficiency with the black dye was obtained under illumination of simulated AM 1.5 solar light (100 mW cm(-2)) using an antireflection film on the cell surface.     

Lithium ion effect on electron injection from a photoexcited coumarin derivative into a TiO2 nanocrystalline film investigated by visible-to-IR ultrafast spectroscopy

The dynamics of ultrafast electron injection from a coumarin derivative (NKX-2311), which is an efficient photosensitizer for dye-sensitized solar cells, into the conduction band of TiO(2) nanocrystalline films have been investigated by means of femtosecond transient absorption spectroscopy in a wide wavelength range from 600 nm to 10 mum. In the absence of Li(+) ions, electron injection into the TiO(2) conduction band occurred in about 300 fs. In the presence of Li(+) ions, however, electron injection occurred within approximately 100 fs, and the oxidized dye generated was found to interact with nearby Li(+) ions. Possible positions of Li(+) ion attachment to the dye molecule were examined by means of semiempirical molecular orbital calculations. The electron injection efficiency was found to increase by a factor of 1.37 in the presence of Li(+) ions. The effects of Li(+) ions on the energy of the TiO(2) conduction band and the electronic interaction between the dye molecule and Li(+) ions are discussed, and the major cause for the acceleration of electron injection was suggested to be a conduction-band shift of TiO(2).     

Photochemical immobilization of protein on the inner wall of a microchannel and Its application in a glucose sensor

A new protein immobilization technique has been developed for patterning enzymes in a specific position inside a microchannel. First, bovine serum albumin (BSA) was adsorbed onto the internal surface of a polydimethylsiloxane microchannel. The microchannel was then filled with the conjugate solution of a photoreactive cross-linker, 4-azido-2,3,5,6-tetrafluorobenzoic acid succinimidyl ester (ATFB-SE), and an enzyme, horseradish peroxidase (HRP). An irradiation by a He-Cd laser activated the azido group of the conjugates and these conjugates became covalently attached to the adsorbed BSA on the microchannel. The enzyme turnover was observed from only the HRP zone. This technique was successfully applied to the enzymatic glucose sensor. Glucose oxidase (GOD) and HRP were sequentially patterned in a single microchannel, i.e., the HRP zone was located downstream from the GOD zone. The calibration curve of a glucose standard solution was linear over the range of 0-128 μM with a correlation coefficient of 0.993. Compared to the traditional method using a 96-well microtiter plate, the present technique on the microchip shortened the reaction time from 30 min to 4.8 s, i.e., to 1/375.     

Synthetic studies on diuretics. 5-(3,3-N,S-substituted-2-propenoyl)-2,3-dihydro-2- benzo[b]furancarboxylic acids

6,7-Dichloro-2,3-dihydro-2-benzo[b]furancarboxylic acid derivatives having a 3,3-N,S-disubstituted-2-propenoyl group at the 5-position were prepared by alkylation of 5-(thiocarbamoyl)acetyl derivatives of the 2,3-dihydro-2-benzo[b]furancarboxylic acid ester or by acetal exchange reaction of 5-[3,3-bis(alkylthio)-2-propenoyl] derivatives. Synthesis of 5-[4 and/or 5-(di)substituted-4-thiazolin-2-ylidene]acetyl-2,3- dihydro-2-benzo[b]furancarboxylic acids was also achieved by the reaction of 2-halo-1-methoxyethyl isothiocyanate with the 5-acetyl derivative in the presence of base or through sulfide contraction of 2-[[6,7-dichloro-2-methoxycarbonyl-2,3-dihydrobenzo[b]furan-5-yl) carbonyl)-methylthio]thiazolium bromide. Some of the compounds which were synthesized showed potent natriuretic activities in rats and mice. The structure-activity relationship is also discussed.     

Photoinduced amino-imino tautomerization reaction in 2-aminopyrimidine and its methyl derivatives with acetic acid

The electronic absorption and fluorescence spectra of 2-aminopyrimidine (2APM), 2-amino-4-methylpyrimidine (2A4MPM), and 2-amino-4,6-dimethylpyrimidine (2ADMPM) with acetic acid (AcOH) were measured in isooctane (2,2,4-trimethylpentane) at room temperature. From the absorption spectra, a hydrogen-bonded complex formation of the 2APM/AcOH, 2A4MPM/AcOH, and 2ADMPM/AcOH systems was recognized in isooctane. The enthalpy changes (-DeltaH) for the complex formation were estimated to be ca. 41.2-45.1 kJ mol-1 and increased in proportion to the numbers of the methyl group introduced into the 2APM. The -DeltaH values refer to the formation of the hydrogen-bonded 1:1 complex between the ring nitrogen atom and NH2 group of the aminopyrimidine and the OH and CO groups of AcOH, respectively. In the 2A4MPM/AcOH double hydrogen-bonded complex the OH group of AcOH is thought to be linked to the ring nitrogen at the 1-postion of 2A4MPM. The fluorescence spectral results indicate that the double proton transfer reaction takes place during the excited state, and gives rise to an imino-tautomer vibration emission, from analogy with the fluorescences of 1-methyl-2(1H)-pyrimidinimine (MPMI), 1,4-dimethyl-2(1H)-pyrimidinimine (DMPMI), and 1,4,6-trimethyl-2(1H)-pyrimidinimine (TMPMI). The fluorescence quantum yields of the imino-tautomers also increased in proportion to the numbers of the methyl group introduced into the 2APM.     

A Normal (0, 1)-Polytope None of Whose Regular Triangulations Is Unimodular

A normal (0,1) -polytope none of whose regular triangulations is unimodular is constructed. Received April 1, 1997, and in revised form June 20, 1997.     

Polysulfonylated cyclodextrins. Part 13: Chemistry of cyclomaltoheptaose tetrasulfonates providing a complete 6-O-sulfonylated cyclomaltoheptaoses library

Five regioisomeric cyclomaltoheptaose (β-cyclodextrin) tetramesitylenesulfonates were prepared and each of them was isolated by a combination of reversed and ordinary phase chromatographic separations. The positions of the substituents on each regioisomer were unambiguously determined using interresidual NOEs. As a result of this study, an indexed library of sulfonylated β-cyclodextrins composed of 19 sulfonates has been established.