Theoretical Study on Redox Potential Control of Iron-Sulfur Cluster by Hydrogen Bonds: A Possibility of Redox Potential Programming

The effect of hydrogen bonds around the active site of Anabaena [2Fe-2S] ferredoxin (Fd) on a vertical ionization potential of the reduced state (IP(red)) is examined based on the density functional theory (DFT) calculations. The results indicate that a single hydrogen bond increases the relative stability of the reduced state, and shifts IP(red) to a reductive side by 0.31–0.33 eV, regardless of the attached sulfur atoms. In addition, the IP(red) value can be changed by the number of hydrogen bonds around the active site. The results also suggest that the redox potential of [2Fe-2S] Fd is controlled by the number of hydrogen bonds because IP(red) is considered to be a major factor in the redox potential. Furthermore, there is a possibility that the redox potentials of artificial iron-sulfur clusters can be finely controlled by the number of the hydrogen bonds attached to the sulfur atoms of the cluster.     

Excitation of the isoscalarE2 resonance in12C by proton inelastic scattering

Proton inelastic excitation spectra of¹²C have been measured imposing a coincidence with alpha decay to⁸Be_g.s. and⁸Be_2.9MeV. In plane angular correlations have been obtained for the main structures observed in the spectra. Comparison with DWBA correlation functions permits a 2⁺ assignment for all the groups in the 20–30MeV excitation range. The percentage of theE2-EWSR exhausted in the same range is in agreement, within the uncertainties indicated, with that derived from the inelastic scattering of other particles.     

Hard gamma as probe of nuclear dynamics

Experimental results concerning the ⁵⁸Ni + ⁵⁸Ni at 30 MeV/u and ⁵⁸Ni + ¹⁹⁷Au at 30 and 45 MeV/u reactions are presented. The emission mechanism of hard photons has been exploited to get information on the time evolution of the reactions. From the measured hard gamma multiplicity associated to different classes of heavy residues a quantitative estimate of the reaction centrality has been obtained. Moreover, evidence of a prompt Intermediate Mass Fragment (IMF) emission is shown for the Ni + Au reaction at 45 MeV/u for central collisions exploring the correlation function between thermal photons and IMF’s.     

Effect of estradiol and ethynylestradiol on microtubule distribution in Chinese hamster V79 cells.

The effects of estradiol (E2) and ethynylestradiol (EE2) on the chromosome number and cellular microtubule architecture of Chinese hamster V79 cells were studied using fluorescent anti-tubulin antibody. Treatment with 20 microM E2 for 48 h induced only a small amount of tetraploid cells, but the normal microtubule network was disrupted completely by only 3 h of treatment. This data reveals that E2 has higher microtubule-disruptive activity than diethylstilbestrol in V79 cells.     

Synthesis of eight-membered ring compounds using enyne metathesis

[reaction: see text] A novel procedure for synthesizing eight-membered ring compounds was developed using ruthenium-catalyzed enyne metathesis. When a CH2Cl2 solution of enyne connected with catechol, o-amino phenol, or o-phenylenediamine was stirred in the presence of benzylidene ruthenium carbene complex (10 mol %) at room temperature overnight, an eight-membered ring compound was obtained in high yield. In a similar manner, monocyclic 1,4-diaza- or 1-oxa-4-azacyclooctene derivative was obtained in high yield.     

Nucleotide sequence of aminoglycoside 6'-N-acetyltransferase [AAC(6')] determinant from Serratia sp. 45.

Gene for aminoglycoside 6'-N-acetyltransferase [AAC(6')] from Serratia sp. 45 was cloned into E. coli. The enzyme produced in E. coli carrying the recombinant plasmid was compared to the Serratia enzyme. Both enzymes acetylated the 6'-C position of amikacin, dibekacin, tobramycin, sisomicin, gentamicin C1a and kanamycin but effected gentamicin C1, gentamicin C2 and micronomycin minimally. No significant difference in optimal pH, isoelectric point or molecular weight was detected. The nucleotide sequence of the gene was determined. Initiating with a GTG codon for methionine, it was composed of 552 base pair coding for 184 amino acids. The molecular weight of the enzyme was about 20418. Comparison of the amino acid sequence of this AAC(6') with the amino acid sequence of aacA4 gene from Serratia marcescens (G. Tran Van Nhieu and E. Collatz, J. Bacteriol., 169, 5708(1987)) showed 98.3% homology.     

Preparation and characterization of insulin-loaded acrylic hydrogels containing absorption enhancers

The objectives of this study were to prepare insulin-loaded acrylic hydrogel formulations containing various absorption enhancers, to perform in vitro and in vivo characterization of these formulations, and to evaluate the factors which affecting insulin availability on rectal delivery of insulin using this hydrogel system. The acrylic block copolymer of methacrylic acid and methacrylate, Eudispert, was used to make the hydrogel formulations. As absorption enhancers, 2,6-di-O-methyl-beta-cyclodextrin (DM-beta-CyD), lauric acid (C12), or the sodium salt of C12 (C12Na), were incorporated into the hydrogels. In an in vitro release test, the release rate of insulin from the hydrogels decreased as the polymer concentration of the hydrogel increased. The addition of C12Na to the hydrogel further increased the insulin release rate, which was greater at higher concentrations of the enhancer. A portion of the C12Na was found to remain bound to the acrylic polymer in dissolution medium. Serum insulin levels were determined at various time points after the administration of insulin solution or insulin-loaded (50 units/kg body weight) Eudispert hydrogels containing 5% (w/w) of C12, C12Na, or DM-beta-CyD to in situ loops in various regions of the rat intestine. The most effective enhancement of insulin release was observed with formulations containing C12Na. The bioavailability of insulin from the hydrogels was lower than that from the insulin solutions. Hydrogel formulations containing 7% or 10% Eudispert remained in the rectum for 5 h after rectal administration. However, the 5% (w/w) C12Na solution stained with Evan's-blue had diffused out and the dye had reached the upper intestinal tract within 2 h. Finally, the rectal administration of insulin-loaded hydrogels, containing 4%, 7%, or 10% (w/w) Eudispert and 5% (w/w) of enhancer (C12, C12Na, or DM-beta-CyD) to normal rats was shown to decrease serum glucose concentrations. The greatest effect was found with insulin-loaded 7% (Eudispert) hydrogel containing C12Na which having cosiderable large insulin release rate and bioadhesive characteristics.     

Extraction-spectrophotometric determination of traces of antimony in copper and lead metals and in lead-base alloy with pyrocatechol violet and tri-n-octylamine

A sensitive spectrophotometric method is described for the determination of antimony in copper and lead metals and in lead-base alloy. Optimal conditions have been established for the extraction and determination of antimony. Antimony (III) is extracted from a potassium iodide—sulfuric acid or a hydrobromic—sulfuric acid medium with toluene and converted to an antimony-pyrocatechol violet (PV) complex. The complex is then extracted with tri-n-octylamine (TOA) and the absorbance of the resulting ternary Sb(III)—PV-TOA complex is measured at 555 nm. As little as 0.5 p.p.m. of antimony in copper metal and 0.2 p.p.m. of antimony in lead metal and lead-base alloy can be determined.     

Biosynthesis of yatein in Anthriscus sylvestris

Little is known about the biosynthesis of yatein, in spite of its importance as a typical heartwood lignan and a key biosynthetic intermediate of the antitumor lignan podophyllotoxin. The present study, based on individual administration of [13C]phenylalanine and deuterium labelled lignans and simultaneous administration of two distinct lignans labelled with deuterium atoms to Anthriscus sylvestris, established the two independent branch pathways from matairesinol, one to afford yatein via thujaplicatin, 5-methylthujaplicatin, and 4,5-dimethylthujaplicatin and the other to bursehernin via pluviatolide. The latter pathway did not lead to yatein, eliminating the presence of a metabolic grid from matairesinol to yatein.