Preparation, testing and characterization of doped TiO2 active in the peroxidation of biomolecules under visible light

Doped TiO2 samples using different preparative procedures were synthesized using either urea or thiourea leading to N- or S-doped TiO2. Photocatalytic peroxidation and oxidation (mineralization) of phosphatidylethanolamine (PE) lipid with doped TiO2 were carried out under light irradiation lambda > 410 nm. The formation of conjugated double bonds in PE molecules was followed to detect the formation of peroxy radicals (peroxidation index) under light excitation (lambda > 410 nm) when doped TiO2 was used. The kinetics of CO2 production was monitored during the mineralization of PE. Colored TiO2 powders were studied in detail by different and complementary physicochemical techniques. The band gap energies of colored TiO2 were determined by diffuse reflectance spectroscopy (DRS). The visible absorption shoulder of TiO2 was observed to follow Urbach's law. The variation of the transient decay after 354 nm laser pulse excitation does not correlate with the different N- and S-TiO2 doping levels introduced by the addition of urea or thiourea. This suggests that the states (recombination centers or traps) introduced by the doping are not effective in varying the decay kinetics within the nanosecond and microsecond time scale. Elemental analysis shows comparable amounts of S- and N-doping of TiO2 when thiourea is used as dopant. X-ray diffraction reveals no rutile in S-TiO2 samples heated to 600 degrees C, suggesting that the addition of sulfur precludes rutilization during sample crystallization. X-ray photoelectron spectroscopy (XPS) of the S-TiO2 samples confirms the preferential localization of S on the 20 topmost layers of S-TiO2 upon calcination at 500 degrees C for 2 h.     

Convenient preparation of 4-arylmethyl- and 4-hetarylmethyl thiazoles by regioselective cycloaddition reactions of 3-sulfanyl- and selanylpropargyl alcohols

Complete details of thiazole syntheses by scandium-catalyzed cycloaddition reactions of 1-aryl- and 1,1-bisaryl-3-phenylsulfanylpropargyl alcohols with thioamides are described. Reactions of 1,1-bisarylpropargyl alcohols with thioamides and selenamide in MeNO₂/H₂O resulted in 4-bisarylmethyl-1,3-thiazoles 4aa-ic and 4H-4,4-bisaryl-1,3-thiazines 5ea-ga in high yields. Reactions in MeNO₂/D₂O resulted in 4-bisaryldeuteriomethyl-1,3-thiazoles 10ca-ia with high deuterium purity. Reactions of dialkyl and alkyl aryl propargyl alcohols are also described.     

Tropical representation of Weyl groups associated with certain rational varieties

Starting from certain rational varieties blown-up from N(P¹), we construct a tropical, i.e., subtraction-free birational, representation of Weyl groups as a group of pseudo-isomorphisms of the varieties. We develop an algebro-geometric framework of τ-functions as defining functions of exceptional divisors on the varieties. In the case where the corresponding root system is of affine type, our construction yields a class of (higher order) q-difference Painlevé equations and its algebraic degree grows quadratically.     

Scandium-catalyzed carbon-carbon bond formations using alpha-organosulfanyl and organoselanyl-alpha-fluoroacetic acid derivatives

The scandium-catalyzed reactions of alpha-organosulfanyl and organoselanyl-alpha-fluoroacetates 1-2, acetamides 3-4 and acetonitrile 5 with soft nucleophiles proceeded to give the products 6a-b, 7a-c, 8a-c, 9a-e in good to high yields. We also successfully performed the scandium-catalyzed intramolecular cyclization reactions and obtained the unique 5-methylene-2-oxotetrahydropyrans 16-17.     

Synthesis and pharmacological profile of an orally-active growth hormone secretagogue, SM-130686

Hypothalamic hormones physiologically regulate pulsatile release of growth hormone (GH) from the anterior pituitary gland. Since the discovery of these hormones in the 1970s, several new chemically synthesized peptidyl and non-peptidyl derivatives have been proved to stimulate and amplify GH secretion, and this series of molecules has been named the growth hormone secretagogues (GHSs). One of these compounds led to the discovery of a GPCR-type receptor for GHSs (GHS-R), and subsequently the endogenous ligand for the receptor has been identified, and is referred to as ghrelin. The identification of GHSs as physiological regulators of GH secretion encouraged us to examine our GHSs pharmacologically. We previously reported that novel oxindole derivatives have been identified as GHS-R agonists from our internal chemical library. Among these derivatives, (+)-6-carbamoyl-3-(2-chlorophenyl)-(2-diethylaminoethyl)-4-trifluoromethyloxindole (SM-130686, 37S) was found to have potent activity in vitro with a good pharmacokinetic profile in rats (bioavailability of 28%). In this article, we review the synthesis and pharmacological evaluation of SM-130686. SM-130686 binds specifically to GHS-R and increases the Ca(2+) concentration in Chinese hamster ovary cells expressing recombinant GHS-R. Maximal enhancement of the intracellular Ca(2+) concentration induced by SM-130686 treatment was approximately 55% that induced by ghrelin, suggesting that SM-130686 may be a partial GHS-R agonist. Also, in in vivo studies, oral administration of SM-130686 increased body length and fat-free mass gain. We compare the pharmacological profile of SM-130686 with other GHSs, including GHRH and ghrelin, and discuss the therapeutic usefulness of GHSs against several disorders, as well as for treatment of GH deficiency.     

Microwave-assisted organic functionalization of silica surfaces: Effect of selectively heating silylating agents

Microwave (MW)-assisted (2.45 GHz) organic functionalization of silica surfaces was investigated using (3-chloropropyl)dimethylsilanes with alkoxy, allyl, or aryl leaving groups in heptane or toluene at 80 °C. ²⁹Si and ¹³C CP/MAS spectroscopy confirmed the 3-chloropropyldimethylsilyl moiety was covalently grafted onto silica for all the samples. The effect of MW irradiation on the loading amount strongly depended on the leaving group as well as the solvent; using methoxysilane and p-anisylsilane in heptane caused a distinct acceleration. The correlation with the dielectric loss factors of the silylating agents suggested that the MW acceleration effect resulted from selectively heating the strongly MW-absorbing silylating agent. For the grafting reaction in toluene, the MW effect was not observed possibly because toluene masked the selective heating effect of the silylating agent.     

Doping effect on the carrier scattering in iron-pnictide superconductors studied by charge transport

In order to reveal the role of “carrier doping” in the iron-based superconductors, we investigated the transport properties of the oxygen-deficient iron-arsenides LnFeAsO_1−y (Ln=La, Ce, Pr and Nd) over a wide doping range. We found that the effect of “doping” in this system is mainly on the carrier scattering rather than carrier density, quite distinct from that in high-T_c cuprates. In the case of La system with lower T_c, the low temperature resistivity is dominated by T² term and fairly large magnetoresistance is observed. On the other hand, in the Nd system with higher T_c, carriers are subject to stronger scattering showing nearly T-linear resistivity and small magnetoresistance. Such strong scattering appears intimately correlated with high-T_c superconductivity in the iron-based system.     

Entropy and Nonlinear Nonequilibrium Thermodynamic Relation for Heat Conducting Steady States

Among various possible routes to extend entropy and thermodynamics to nonequilibrium steady states (NESS), we take the one which is guided by operational thermodynamics and the Clausius relation. In our previous study, we derived the extended Clausius relation for NESS, where the heat in the original relation is replaced by its “renormalized” counterpart called the excess heat, and the Gibbs-Shannon expression for the entropy by a new symmetrized Gibbs-Shannon-like expression. Here we concentrate on Markov processes describing heat conducting systems, and develop a new method for deriving thermodynamic relations. We first present a new simpler derivation of the extended Clausius relation, and clarify its close relation with the linear response theory. We then derive a new improved extended Clausius relation with a “nonlinear nonequilibrium” contribution which is written as a correlation between work and heat. We argue that the “nonlinear nonequilibrium” contribution is unavoidable, and is determined uniquely once we accept the (very natural) definition of the excess heat. Moreover it turns out that to operationally determine the difference in the nonequilibrium entropy to the second order in the temperature difference, one may only use the previous Clausius relation without a nonlinear term or must use the new relation, depending on the operation (i.e., the path in the parameter space). This peculiar “twist” may be a clue to a better understanding of thermodynamics and statistical mechanics of NESS.     

Distribution of inorganic arsenic and methylated arsenic in marine organisms

Inorganic arsenic and methylated arsenic compounds in 60 specimens of marine organisms were investigated by hydride generation derivatization and cold-trap gas chromatography–mass spectrometry (GC MS). Chloroform–methanol extracts from seaweeds, shellfish, fish, crustaceans and other marine organisms were separated into water-soluble and lipid-soluble fractions. The arsenic compounds in each fraction were identified and analysed as arsine, methylarsine, dimethylarsine and trimethylarsine. Trimethylarsenic compounds were distributed mainly in the water-soluble fraction of muscle of carnivorous gastropods, crustaceans and fish. The amounts of dimethylated arsenic compounds were found to be larger than that of trimethylated arsenic in the lipid-soluble fraction of fish viscera. Dimethylated arsenic compounds were distributed in the water-soluble fraction of Phaeophyceae.