Synthesis and characterization of novel 1,3,4-oxadiazole- or 1,3,4-thiadiazole-containing wholly conjugated polyazomethines

A series of thermally stable and semiconducting polyazomethines containing 1,3,4-oxadiazole or 1,3,4-thiadiazole ring in the polymer backbone were synthesized by the simple solution poly-condensation of dialdehydes with the preformed nuclei with aromatic diamines under mild conditions. To elucidate the structure and also structure-property relationships of the polymers, model compounds were prepared under the same reaction conditions. These polyazomethines having a wholly conjugated system were yellow powders and had reduced viscosities up to 0.38 dL/g in concentrated sulfuric acid and electric conductivity as high as 10^?11 S cm^?1 at room temperature. Thermogravimetry showed that all the polymers were heat resistant up to around 400°C, in both air and nitrogen atmospheres. Their completely black colored charge-transfer complexes were prepared by iodine-doping of the polymers. The room temperature conductivity of the polymers was found to be markedly increased up to the orders of 10^?6–10^?7 S cm^?1 upon doping. The highest value attained was 4.8 x 10^?6 S cm^?1. Comparison of electronic spectra of the polymers with those of the model compounds indicated the π-electrons in the polymers are extensively delocalized along the polymer main chain.     

Multi-way PLS modeling of structure–activity data by incorporating electrostatic and lipophilic potentials on molecular surface

We devised and elaborated a surface-based three-dimensional-quantitative structure–activity relationship (3D-QSAR) method, which had been proposed in the previous study. This approach can be applied to more general case where both the electrostatic and lipophilic potentials on molecular surface simultaneously change. The 3D coordinates of all sampling points on molecular surface are projected into a 2D map by Kohonen neural network (KNN). Each node in the map is coded by the associated molecular electrostatic potential (MEP) or molecular lipophilic potential (MLP) values. The electrostatic and lipophilic KNN maps are generated for each compound and the four-way array is constructed by collecting two KNN maps of all samples. The correlation between four-way array and biological activity is examined by four-way partial least-squares (PLS). For validation, the structure–activity data of estrogen receptor antagonists was investigated. The four-way PLS model gave the high statistics at calibration and validation stages. The coefficients of the four-way PLS model back-projected on molecular surface had a reasonable 3D distribution and it was nicely consistent with active site of the estrogen receptor which was recently made clear by X-ray crystallography.     

Total synthesis of paracentrone, C31-allenic apo-carotenoid

The stereocontrolled total synthesis of a C31-allenic apo-carotenoid, paracentrone, was achieved by the convergent C20 + C11 = C31 strategy. The key elements of our synthesis were the Pd-catalyzed cross-coupling to stereoselectively construct the conjugated polyene backbone skeleton and the designed geometrical isomerization at the central double bond of the conjugated polyene chain. In addition, the terminal oxygenated cyclohexane ring having the allenic moiety was prepared by the highly diastereoselective Sharpless epoxidation under our own reaction conditions.     

Radiation-Induced degradation of polyethylene: Polymer structure and stability

The radiation-stability of annealed and quenched polyethylene (PE) was estimated by gel, FTIR, and mechanical property (elongation at break) measurements. Although both types of PE showed an equal probability in gel and carbonyl formation, the resistance to γ-ray irradiation as probed by elongation at break (%) was superior in quenched PE compared to annealed PE. This difference is discussed from the viewpoint of polymer structure, especially the number of the tie molecules, of annealed and quenched PE.     

Direct synthesis of novel 2-imino-1,3-selenazolidine derivatives from O-methanesulfonyl β-amino alcohol hydrochlorides

Recently, we have reported that 4,5-dialkylsubstituted 2-imino-1,3-azolidine derivatives (1) strongly inhibit inducible nitric oxide synthase (iNOS). To our knowledge, only few methods have been reported for the synthesis of 4,5-dialkylsubstituted 2-imino-1,3-selenazolidine derivatives (2), which are the selenium analogue of 1. Herein, we report the direct synthesis of 2 from the corresponding O-methanesulfonyl β-amino alcohol hydrochlorides using potassium selenocyanate and evaluation for the inhibitory activity against iNOS of the newly synthesized selenazolidine derivatives.     

Recognition of liposome-bound antigens by antipeptide antibody

In order to clarify the effects of the differences in physical states of antigens on recognition by antibodies in immunoassays, the binding characteristics of an antipeptide polyclonal antibody to the peptide and the corresponding protein were studied. The reactivity in the immunoliposome assay (ILA), as well as in the double-antibody sandwich ELISA, was identical to that in the solution. These results indicate that the conformation of liposome-bound antigen is changed little by coupling to liposomes and is almost the same as that of the native antigen in the liquid phase. It is desirable to assay by double-antibody sandwich ELISA or ILA to detect native proteins, and the latter is very easily performed.     

Thermal decomposition behavior of bis-aminimides and their application to polymerization of epoxide

Bis-aminimide compounds [bis-N, N,-dimethyl-N,-(2-hydroxypropyl)-amine-N,′-adipimide ( 1 ) and bis-trimethylamine adipimide ( 2 )] were found to exhibit different thermal decomposition behavior and polymerization efficiency for an epoxide (phenyl glycidyl ether, PGE). The thermal decomposition rate of 1 was much higher than that of 2. It seemed that hydrogen bonding enhanced the decomposition rate. Compound 1 was thermolyzed to give a diisocyanate and a tertiary aminoalcohol, which subsequently reacted with each other to give a urethane. When 2 was heated, the isocyanate generated from 2 remained unreacted. PGE reacted with thoseaminimides to give different products, depending on their thermolyzed products. Mixtures of diisocyanate, tertiary amine, and PGE were used in the model reactions, and the thermal reaction between the expected decomposition products of aminimides was investigated in the presence and absence of PGE. The amount of high molecular weight fraction in PGE + 2 is greater than that of PGE + 1 . In the former, the free isocyanate groups may act as a chain extender to give higher molecular weight fractions.     

Miniaturization in carbohydrate analysis

Recent progress of microchip electrophoresis (ME) of carbohydrates is overviewed. Carbohydrate analysis by ME encounters difficulties such as lack of electric charge and deficiency of a chromophore/fluorophore in analyte molecules, however, it benefits from the accumulated knowledge of capillary electrophoresis (CE) and rapid separation of simple sugars also by ME, with high column efficiency comparable to CE, has become possible. Analysis at high pH, with electrochemical detection, is a promising approach because carbohydrates can be ionized by weak dissociation of the hydroxyl groups and the in situ formed ionic species can be effectively separated by the zone electrophoresis mode. The separated species can be sensitively monitored by electrochemical detection on a gold or copper electrode. Ionization as borate complexes and refractometric detection is also possible, though sensitivity is lower. Introduction of UV-absorbing or fluorescent tags is potentially useful but the time-consuming derivatization processes sacrifice the rapidity of ME. Examples of ME of carbohydrates as 1-phenyl-3-methyl-5-pyrazolone (PMP; for simple mono- and oligosaccharides with UV detection), 8-aminopyrene-1,3,6-trisulfonate (APTS; for oligosaccharides ladders with LIF detection), and 4-nitro-2,1,3-benzoxadiazole (NBD-F; for amino sugars and aminoalditols with LIF detection) derivatives are presented, with details of the analytical conditions. Since ME in a short separation channel enables rapid analysis within 1 min, it presents an ideal tool for clinical analysis, as shown in a few papers reporting protocols for specific blood glucose assay. Finally, the usefulness of microfluidic reactors and microarrays for enzyme-assisted carbohydrate analysis as well as glycan profiling is pointed out.     

Synthesis of polyesters having quaternary ammonium groups in the side chains and preparation of their blends with poly(vinyl alcohol)

Triethyl-2,3-propanediolammonium chloride (TPC) was prepared and used for the preparation of polyester and copolyesters having quaternary ammonium groups in the side chains. The polycondensation of isophthaloyl dichloride with TPC and other dihydroxy compounds was performed by the organic phase/organic phase interfacial polycondensation method using N,N-dimethylacetamide/n-heptane or trimethyl phosphate/n-heptane as reaction media in the presence of tetramethyl ethylenediamine. Blend films were prepared from these polyesters and poly(vinyl alcohol) by casting from aqueous or aqueous NaOH solution. The electrical conductivity of the blend films is remarkably affected by the moisture content and in the order of 10^?5 ～ 10^?8 S/cm in the presence of moisture. © 1994 John Wiley & Sons, Inc.     

A novel inhibitor for Fe-type nitrile hydratase: 2-cyano-2-propyl hydroperoxide

Nitrile hydratase (NHase) is a non-heme iron or non-corrin cobalt enzyme having two post-translationally modified ligand residues, cysteine-sulfinic acid (alphaCys112-SO(2)H) and -sulfenic acid (alphaCys114-SOH). We studied the interaction between Fe-type NHase and isobutyronitrile (iso-BN) which had been reported as a competitive inhibitor with a K(i) value of 5 microM. From detailed kinetic studies of the inhibitory effect of iso-BN on Fe-type NHase, we found that authentic iso-BN was hydrated normally and that the impurity present in commercially available iso-BN inhibited NHase activity strongly. The inhibitory compound induced significant changes in the UV-vis absorption spectrum of NHase, suggesting its interaction with the iron center. This compound was purified by using reversed-phase HPLC and identified as 2-cyano-2-propyl hydroperoxide (Cpx) by (1)H and PFG-HMBC NMR spectroscopy. Upon addition of a stoichiometric amount of Cpx, NHase was irreversibly inactivated, probably by the oxidation of alphaCys114-SOH to Cys-SO(2)H. This result suggests that the -SOH structure of alphaCys114 is essential for the catalytic activity. The oxygen atom in Cys-SO(2)H is confirmed to come from the solvent H(2)O. The oxidized NHase was found to induce the UV-vis absorption spectral changes by addition of Cpx, suggesting that Cpx strongly interacted with iron(III) in the oxidized NHase to form a stable complex. Thus, Cpx functions as a novel irreversible inhibitor for NHase.