Thermal properties and mixing state of diol-water mixtures studied by calorimetry, large-angle X-ray scattering, and NMR relaxation

Differential scanning calorimetry (DSC) has been performed on aqueous mixtures of three diols, which involve a linear carbon chain, HO-(CH 2) n -OH ( n = 3, 4, and 5), over the whole mole fraction range of diols. The DSC results have shown the alkyl chain parity for the freezing process of the aqueous mixtures: aqueous mixtures of 1,3-propanediol (PrD) and 1,5-pentanediol (PeD) are kept in the supercooled state or vitrified over a wide mole fraction range, while those of 1,4-butanediol (BuD) are easily crystallized. The structure of PrD-water mixtures has been elucidated by using the large-angle X-ray scattering (LAXS) technique. It has been suggested that the structural change of PrD-water mixtures occurs at PrD mole fractions of x PrD = 0.4 and 0.8: in the range of x PrD < or = 0.4 where the tetrahedral-like structure of water predominates, in the range of 0.4 < x PrD < 0.8 where both PrD and water structures coexist, and in the range of x PrD > or = 0.8 where the inherent structure of PrD is mainly formed. (17)O and (1)H NMR relaxation measurements have been made on aqueous mixtures of ethylene glycol (EG, n = 2), PrD, and BuD to clarify the dynamics of H 2 (17)O and diol molecules. The (17)O NMR relaxation rates have suggested that the rotational motion of water molecules is gradually retarded in the diol-water mixtures with increasing diol content and that the restriction of the motion is more remarkable in the order of EG < PrD < BuD. On the basis of all the results, together with comparison with those of methanol-water, ethanol-water, and 1-propanol-water mixtures previously reported, the mixing state of diol-water mixtures has been discussed at the molecular level.     

Electroreductive intramolecular coupling of 1-indolealkanones

The electroreduction of 1-indolealkanones in isopropanol gave five-, six-, and seven-membered trans-cyclized products stereospecifically. On the other hand, the electroreduction of 3-methoxycarbonyl-1-indolealkanones afforded mixtures of two diastereomers of the corresponding trans- and cis-cyclized products. The DFT calculations for the radical anions support that the reductive couplings of 1-indolealkanones and 3-methoxycarbonyl-1-indolealkanones proceed through different reaction mechanisms.     

Efficient short step synthesis of Corey's tamiflu intermediate

Corey's tamiflu intermediate was synthesized from a bicyclolactam adduct obtained by base-catalyzed Diels-Alder reaction of N-nosyl-3-hydroxy-2-pyridone with ethyl acrylate. A compound that has the same array of functional groups with the Corey's intermediate was obtained in four steps from the DA adduct in 47% overall yield. The intermediate itself was also prepared efficiently by simply changing the protective group.     

Bacterial hydrolytic dehalogenases and related enzymes: occurrences, reaction mechanisms, and applications

Dehalogenases catalyze the cleavage of the carbon-halogen bond of organohalogen compounds. They have been attracting a great deal of attention partly because of their potential applications in the chemical industry and bioremediation. In this personal account, we describe occurrences, reaction mechanisms, and applications of bacterial hydrolytic dehalogenases and related enzymes, particularly L-2-haloacid dehalogenase, DL-2-haloacid dehalogenase, fluoroacetate dehalogenase, and 2-haloacrylate reductase. L-2-Haloacid dehalogenase is a representative enzyme of the haloacid dehalogenase (HAD) superfamily, which includes the P-type ATPases and other hydrolases. Structural and mechanistic analyses of this enzyme have yielded important insights into the mode of action of the HAD superfamily proteins. Fluoroacetate dehalogenase is unique in that it catalyzes the cleavage of the highly stable C--F bond of a fluorinated aliphatic compound. In the reactions of L-2-haloacid dehalogenase and fluoroacetate dehalogenase, the carboxylate group of Asp performs a nucleophilic attack on the alpha-carbon atom of the substrate, displacing the halogen atom. This mechanism is common to haloalkane dehalogenase and 4-chlorobenzoyl-CoA dehalogenase. DL-2-Haloacid dehalogenase is unique in that a water molecule directly attacks the substrate, displacing the halogen atom. The occurrence of 2-haloacrylate reductase was recently reported, revealing a new pathway for the degradation of unsaturated aliphatic organohalogen compounds.     

Thiocarbonyl induced heterocumulenic Pauson-Khand type reaction: expedient synthetic method for thieno[2,3-b]indol-2-ones

The first examples of C[double bond, length as m-dash]S induced Pauson-Khand type reactions are described; 2-alkynylphenyl isothiocyanates were converted to 3-substituted-2H-thieno[2,3-b]indol-2-ones in the presence of a stoichiometric amount of Mo(CO)(6) or Co(2)(CO)(8), or a catalytic amount of Rh catalyst under an atmospheric pressure of carbon monoxide.     

Design of nanostructured ceria-based solid electrolytes for development of IT-SOFC

A considerable interest has been shown in the application of doped ceria (CeO₂) compounds for “intermediate” (300–500 °C) temperature operation of solid oxide fuel cells. The microdomains with ordered structure of oxygen vacancy were observed in the microstructure of the M-doped CeO₂-sintered bodies (where M: Gd, Y, and Dy). We have previously shown that the conductivity of doped CeO₂-sintered bodies was lower when the sintered body contained large microdomains within grains. As a consequence of this observation, we have examined the grain size dependence and dopant content on conductivity in specimens where we adjust the microdomain size and a degree of oxygen vacancy ordering in the microdomains by controlling the microstructure. The microdomain size control in Dy-doped CeO₂ specimens was obtained by combining pulsed electric current sintering and conventional sintering. Using these techniques, we were able to improve the conductivity in Dy-doped CeO₂ specimens to a point where it became comparable to that of the more conventional Gd-doped CeO₂ specimens. It is concluded that by combining ultimate high-resolution analysis of these nanostructures with the adjusting processing route design, it is possible to further develop these materials in CeO₂-doped fuel cell application.     

Arginine-modified DNA aptamers that show enantioselective recognition of the dicarboxylic acid moiety of glutamic acid

We have screened glutamic acid-binding aptamers from a modified DNA pool containing arginine residues using the method of systematic evolution of ligands by exponential enrichment (SELEX). Thirty-one modified DNA molecules were obtained from the enriched pool after the 17th round of selection, and their binding affinities for the target were evaluated by binding assays using affinity gels. Three modified DNA molecules having higher affinity were sequenced and we determined their affinity and specificity for the target by surface plasmon resonance (SPR) measurements. The SPR studies indicated that two of these three aptamers distinguished the dicarboxylic acid moiety of the D-isomer from that of the L-isomer; however, the third aptamer did not show enantioselectivity.     

Surface modification of polydimethylsiloxane with photo-grafted poly(ethylene glycol) for micropatterned protein adsorption and cell adhesion

In this study, we applied photo-induced graft polymerization to micropatterned surface modification of polydimethylsiloxane (PDMS) with poly(ethylene glycol). Two types of monomers, polyethylene glycol monoacrylate (PEGMA) and polyethylene glycol diacrylate (PEGDA), were tested for surface modification of PDMS. Changes in the surface hydrophilicity and surface element composition were characterized by contact angle measurement and electron spectroscopy for chemical analysis. The PEGMA-grafted PDMS surfaces gradually lost their hydrophilicity within two weeks. In contrast, the PEGDA-grafted PDMS surface maintained stable hydrophilic characteristics for more than two months. Micropatterned protein adsorption and micropatterned cell adhesion were successfully demonstrated using PEGDA-micropatterned PDMS surfaces, which were prepared by photo-induced graft polymerization using photomasks. The PEGDA-grafted PDMS exhibited useful characteristics for microfluidic devices (e.g. hydrophilicity, low protein adsorption, and low cell attachment). The technique presented in this study will be useful for surface modification of various research tools and devices.