2-Oxo-1,3-dioxoles as specific substrates for measurement of arylesterase activity

Various 4-arylthiomethyl-2-oxo-1,3-dioxole derivatives IIIa-o were synthesized. Their hydrolysis rates by arylesterase (EC 3.1.1.2) and cholinesterase (EC 3.1.1.8) in human serum were evaluated. Some of them were not hydrolyzed by cholinesterase, but were hydrolyzed easily by arylesterase. Among the substrates, sodium 4-((5-methyl-2-oxo-1,3-dioxol-4-yl)methylthio)benzenesulfonate (IIIg) was selected for its substrate reactivity toward arylesterase and its good water solubility. In addition, neither aliesterase (EC 3.1.1.1), acetylesterase (EC 3.1.1.6) nor cholesterol esterase (EC 3.1.1.13) hydrolyzed the compound. IIIg is thus concluded to be a specific substrate for arylesterase. Our assay system for serum arylesterase using IIIg can be readily applied to an automatic analyzer in the diagnosis of liver cirrhosis.     

Selective determination of microbial cells by graphite electrode modified with adsorbed 4,4′-bipyridine

The concentrations of microbial cells in suspensions can be measured with a graphite electrode modifed with adsorbed 4,4′-bipyridine, by using cyclic volummetry or differential pulse volummetry. The relationship between the peak current and the cell concentration for Saccharomyces cerevisiae is linear over the range 0.03 × 10⁸—2.0 × 10⁸ cells ml^?1. Yeast, gram-positive bacteria and gram-negative bacteria gave different peak potentials, which may be useful for classification purposes. Electron transfer between the microbial cells and the 4,4′-bipyridine-modified electrode is mediated by coenzyme A in the cell wall.     

Parametrization of the equations-of-motion method for conjugated hydrocarbons

The equations-of-motion (EOM ) method has been parametrized for the evaluation of the “π → π*” transition energies and moments of conjugated hydrocarbons. In this new semiempirical scheme, the effect of the dynamical screening by σ electrons is explicitly included.     

Formal total synthesis of hemibrevetoxin B by a convergent strategy

Concise construction of the trans-fused 7/7/6/6 tetracyclic ether part of hemibrevetoxin B (1) was achieved by a convergent strategy based on coupling reaction of an acyl anion equivalent, reductive cyclization of an α,ε-dihydroxyketone, and introduction of a methyl group at the central ring junction by the Nicolaou method. The resultant tetracyclic ether was transformed into the known intermediate, which was already converted to 1 by the Yamamoto group, thereby completing the formal total synthesis of 1.     

Profiling and comprehensive expression analysis of ABC transporter solute-binding proteins of Bacillus subtilis membrane based on a proteomic approach

We analyzed ABC transporter solute-binding proteins (SBPs) of the Bacillus subtilis membrane using a proteomic approach. We prepared a washed cell membrane fraction that was insoluble in 134 mM nondetergent sulfobetaine and then extracted proteins using mixtures of detergents in a stepwise manner. The membrane proteins were resolved by three two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) or two one-dimensional (1-D) PAGE procedures, electroblotted, and digested in the presence of 5% or 80% acetonitrile. Thereafter, matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF MS) identified 637 proteins corresponding to 15.9% of the total cellular proteins. We predicted that among these, 256 were membrane proteins, 101 were lipoproteins or secretory proteins and 280 were soluble proteins containing peripheral proteins that function in both the cytoplasm and the cell membrane such as SecA and FtsY. Among the 637 proteins, we identified 30 SBPs among 38 importers predicted by a bioinformatic search of the genome. We confirmed expression of the genes for the 30 SBPs using DNA microarray analysis. We compared the 2-D gel separation profiles of submembrane fractions solubilized by 1% n-dodecyl-beta-D-maltoside from cells cultured on Luria Bertani (LB), S7, and S7 medium without glutamate as well as DNA microarray data on LB and S7. The results suggested that YcdH, YtmK and YurO are binding proteins for Mn(++), glutamate and glucose, respectively, and that YqiX and YxeM are binding proteins for amino acids (tryptophan in S7 medium).     

Synthesis of functionalized porphyrins as oxygen ligand receptors

Oxophilic synthetic receptors were designed and synthesized using a porphyrin scaffold, with the aim of constructing a preorganized complementary binding site for phenols and carbohydrates. We pursued three strategies for phenol recognition: (1) Lewis acid/Lewis base combinations serving as a hydrogen bond donor and acceptor for the OH group, (2) Lewis base/pi-pi stacking, targeting both the OH group and the aromatic moiety of phenols, and (3) exchange of the axial hydroxyl ligand on a trivalent and oxophilic metal center of aluminum porphyrin. For the recognition of acidic phenols, the most promising recognition motif was Lewis base/pi-pi stacking, which can bind to phenols with a hydrogen bond and pi-pi stacking interactions. [5-(8-Quinolyl)-10,15,20-triphenylporphyrinato]zinc binds to p-nitrophenol with a binding constant of 540 M(-)(1) in CHCl(3) at 25 degrees C. For carbohydrate recognition, we designed the metalloporphyrin receptor having 8-quinolyl groups and o-carbomethoxymethoxyphenyl groups, where these Lewis basic parts serve as the cooperative hydrogen bonding sites for the hydroxyl groups of glucoside. The receptor binds to beta-octyl glucoside with a binding constant of 7.35 x 10(4) M(-)(1) in CHCl(3) at 15 degrees C, demonstrating importance of formation of a highly ordered hydrogen bonding network between the receptor and the guest. These binding features have significant implications for the rational design of oxophilic artificial receptors.     

Polymerization of coordinated monomers. IV. Copolymerization of methyl methacrylate– and methacrylonitrile–Lewis acid complexes with styrene

Complexes of methyl methacrylate and methacrylonitrile with Lewis acids (SnCl₄, AlCl₃, and BF₃) were copolymerized with styrene at ?75°C under irradiation with a high-pressure mercury lamp in toluene solution. The resulting copolymers consisted of equimolar amount of methyl methacrylate or methacrylonitrile and styrene, regardless of the molar ratio of monomers in the feed. NMR spectroscopy showed the copolymers to have an alternate sequence. The tacticities of the copolymers varied with the complex to have an alternate sequence. The tacticities of the copolymers varied with the complex species: the copolymer from the SnCl₄ complex system had a higher cosyndiotactieity, while those from the AlCl₃ and the BF₃ complex systems showed coisotacticity to predominate over cosyndiotacticity. NMR spectroscopic investigation of the copolymerization system indicated the presence of a charge-transfer complex between the styrene and the methyl methacrylate coordinated to SnCl₄. The concentration of the charge-transfer complex was estimated to be about 30% of monomer pairs at ?78°C at a 1:1 molar ratio of feed. The growing end radicals were identified as a methyl methacrylate radical for the AlCl₃ complex–styrene system and a styrene radical for the SnCl₄ complex–styrene system by the measurement of the ESR spectra of the copolymerization systems under or after irradation with a high-pressure mercury lamp. The tacticity of the resulting polymer appears to be controlled by the structure of the charge transfer complex. In the case of the SnCl₄ complex a certain interaction of SnCl₄ with the growing end radical seems to be a factor controlling the polymer structure. These copolymerizations can be explained by an alternating charge-transfer complex copolymerization scheme.     

Diastereoselective Iodocarbocyclization Reaction of 2- or 3-Oxy-4-pentenylmalonate Derivatives

1,2- Or 1,3-asymmetric induction in the iodocarbocyclization reaction of 4-pentenylmalonate derivatives having a stereogenic center at an allylic or a homoallylic position has been investigated. The iodocarbocyclization reactions of 3-oxy-4-pentenylmalonate derivatives proceeded with high cis-selectivity through stereoelectronic control of the oxygenated substituent at an allylic position. In the reaction of (S)-2-siloxy-4-pentenylmalonate, an excellent diastereoselectivity was achieved through the utilization of double stereodifferentiation with a chiral titanium catalyst. Furthermore, as an application of the present reaction, the asymmetric syntheses of cyclosarkomycin and a synthetic intermediate of brefeldin A from optically pure 2- and 3-oxy-4-pentenylmalonate derivatives are also described.     

BLUE and NEAR ULTRAVIOLET REVERSIBLE PHOTOREACTION IN THE INDUCTION OF FUNGAL CONIDIATION

Abstract— The effects of blue light and near UV light on the induction of conidiation in the fungus, Aliernuriu tomato, were investigated. Induction of conidiation was repeatedly controlled by alternating doses of near UV light and blue light. When the final light was near UV, conidiation was induced and conidia developed in the following darkness; when it was blue, the induction of conidiation was suppressed. When conidiation was induced by irradiation with a light mixed with near UV and blue, not only the time lag for inducing conidiation but also the amount of conidia formed were regulated by the fluence rates of both those lights.
Thus, 'mycochrome' is considered to function as a photoreceptor system in the induction of conidiation of this fungus.     

Synthesis of directly linked zinc(II) porphyrin-imide dyads and energy gap dependence of intramolecular electron transfer reactions

A series of zinc(II) porphyrin-imide dyads (ZP-Im), in which an electron donating ZP moiety is directly connected to an electron accepting imide moiety in the meso position, have been prepared for the examination of energy gap dependence of intramolecular electron transfer reactions with large electronic coupling. The nearly perpendicular conformation of the imide moiety towards the porphyrin plane has been revealed by Xray crystal structures. The energy gap for charge separation, 1ZP* - Im --> ZP+ - Im-, is varied by changing the electron accepting imide moiety to cover a range of about 0.8 eV in DMF. Definitive evidence for electron transfer has been obtained in three solvents (toluene, THF, and DMF) through picosecond-femtosecond transient absorption studies, which have allowed us to determine the rates of photoinduced charge separation, 1ZP* - Im --> ZP+ - Im-, and subsequent thermal charge recombination ZP+ - Im- --> ZP - Im. The free-energy gap dependence (energy gap law) has been probed from the normal to the nearly top region for the charge separation rate alone, and only the inverted region for the charge recombination rate. Although both of the energy gap dependencies can be approximately reproduced by means of the simplified semiclassical equation, when we take into consideration the effect of the high frequency vibrations replaced by one mode of averaged frequency, many features, including the effects of solvent polarity and the electron tunneling matrix element on the energy gap law, differ considerably from those of the previously studied porphyrin-quinone systems, which have weaker interchromophore electronic interactions.