Differential pulse voltammetric determination of P(V) following adsorptive accumulation of alpha-[PMo(12)O(40)](3-) on a polypyrrole-modified glassy carbon electrode

On the basis of the formation and pre-concentration of an α-Keggin-type [PMo₁₂O₄₀]³⁻ complex, a novel voltammetric method was developed for the determination of trace levels of P(V). The α-[PMo₁₂O₄₀]³⁻ complex was formed by heating a 5×10⁻⁴ M Mo(VI)-0.2 M HCl-40% (v/v) CH₃CN system containing a trace amount of P(V) at 70 °C for 30 min. During the electrochemical polymerization of pyrrole in the α-[PMo₁₂O₄₀]³⁻ solution, the α-[PMo₁₂O₄₀]³⁻ complex was accumulated into the polypyrrole film on a glassy carbon electrode. The differential pulse voltammetric peak current due to the α-[PMo₁₂O₄₀]³⁻ complex incorporated in the polypyrrole film was linearly dependent on the P(V) concentration in the range of 5×10⁻⁹-5×10⁻⁷ M; a detection limit of 2×10⁻⁹ M was achieved.     

Preparation of light-stable micelles with azo dyes from a nonamphiphilic random block copolymer

Light-stable micelles with azo dyes were prepared by micelle formation of a nonamphiphilic diblock copolymer containing azobenzene and UV absorbent at ca. 1 mol% as the unit ratios. The nonamphiphilic block copolymer consists of two different kinds of random copolymer blocks: poly[4-(phenylazophenoxymethyl)styrene-co-vinylphenol] (P(AS-co-VPh)) and poly[4-(2-hydroxybenzophenoxymethyl)styrene-co-styrene] (P(HBS-co-St)). This random block copolymer, P(AS-co-VPh)-b-P(HBS-co-St) formed the micelles in the presence of 1,4-butanediamine (BDA) through hydrogen bond cross-linking between the VPh units via BDA. The micelles had the azobenzene moieties at the cores and the UV absorbents at the coronas. The micelles showed a small color difference in color fading experiments, in comparison with the unimers and with micelles having no UV absorbent at the coronas. It is significant that the diblock copolymer forms the micelles and has the UV absorbents at the coronas to suppress the color fading. Furthermore, the chain length of ,-diamines had no effect on the hydrodynamic radius of the micelles, but affected the aggregation number and the cmc.     

Plaunol A and B,new anti-ulcer diterpenelactones from Crotonsublyratus

Two new diterpenelactones named plaunol A ($\text{2}$) and B ($\text{3}$) exhibiting anti-Shay ulcer activity were isolated from Thai medicinal plant, $\text{Croton}$$\text{sublyratus}$. Structure of $\text{2}$ was determined by X-ray analysis of its $\text{p}$-bromobenzoate and structure of $\text{3}$ was deduced from the results of chemical correlation and the spectral data.     

Lipid peroxidation of the erythrocyte membrane caused by stimulated polymorphonuclear leukocytes in the presence of ferritin

Lipid peroxidation of erythrocyte membrane was caused by phorbol myristate acetate (PMA)-stimulated polymorphonuclear leukocytes (PMN) in the presence of ferritin. PMN themselves were not peroxidized. A lag period was observed before the start of the peroxidation reaction. In contrast, ferritin iron was continuously released by PMA-stimulated PMN, suggesting that accumulation of free iron in the reaction system was important for proceeding of the peroxidation reaction. Superoxide dismutase, catalase, hydroxyl radical scavengers and an iron chelator, diethylenetriaminepenta-acetic acid, inhibited the lipid peroxidation, indicating that the lipid peroxidation is initiated by a hydroxyl radical generated from the interaction of H2O2 with ferrous iron released from ferritin.     

A New Synthesis of 3-Deoxy-D-Manno-Octulosonic Acid (KDO) From D-Mannose Via Condensation of Dioxene

Abstract

The title compound has long been known as an essential component of lipopolysaccharides (LPS) and capsular polysaccharides which exist in the outer membrane of Gram-negative bacteria. KDO has attracted additional attention as a consequence of some remarkable discoveries; i) mutants unable to produce KDO are non-viable.¹ ii) KDO is not present in mammalian cells,² iii) the 2-deoxy analog of β-KDO represents a new class of synthetic antimicrobial agent.^3,4 Although syntheses of KDO have been reported by many groups,^5–8 a more efficient synthetic method endowed with the potential for synthesis of not only complex glycoconjugates but also biologically significant analogs is required.     

Permselective monolayer membrane based on two-dimensional cross-linked polysiloxane LB films for hydrogen peroxide detecting glucose sensors

Novel two-dimensional (2D) cross-linked polysiloxane LB films were prepared and applied for glucose sensing as H2O2-permselective films in order to block other electroactive interferences, such as L-ascorbic acid, L-cysteine, uric acid and acetaminophen; the 2D cross-linked polysiloxane monolayers were remarkably effective in eliminating interfering responses and had a rapid response for glucose, even though the films were only a monolayer thick.     

Direct detection of formate ligation in cytochrome c oxidase by ATR-FTIR spectroscopy

The IR signature of binding of formate to the heme a(3-)Cu(B) binuclear site of bovine cytochrome c oxidase has been obtained by perfusion ATR-FTIR spectroscopy. The data show unequivocally that formate binds in its anionic form despite its binding being electroneutral overall. The bound formate can be distinguished from free ligand by the binding-induced sharpening and downshifting of vibrational bands. Formate ligation also causes shifts of vibrational modes of heme a(3) and its substituents and perturbation of histidine residues. The association of the accompanying protonation change with a carboxylate or tyrosine can be ruled out and may involve a histidine metal ligand or, more likely, a simple displacement into the bulk phase of a hydroxide ligand to heme a(3) or CU(B), a reaction which would account for stoichiometric proton uptake and maintenance of net charge within the binuclear center domain.