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.     

Vibrational spectra and crystal structure of ethyl methyl sulfide-mercury(II) chloride complex

The crystal structure of the ethyl methyl sulfide-mercury(II) chloride complex, CH₃SCH₂CH₃· HgCl₂, has been determined by X-ray diffraction. The conformation about the CS-CC axis of the complex is trans, which is different from the conformation of crystalline ethyl methyl sulfide. The Raman and IR spectra of the complex have been measured. Observed wavenumbers of the CH₂ rocking and C-C stretching vibrations of the complex are close to those of the trans form of ethyl methyl sulfide in the liquid state, but the wavenumber of the C-S stretching vibration shifts on formation of the S-Hg bond.     

Studies on pyrazines. Part 28 . Deoxydative acetoxylation of pyrazine N-oxides

Deoxydative acetoxylation of 3-methoxy-, 3-phenyl-, 3-methyl-, 3-chloro-, and 3-methoxycar-bonylpyrazine 1-oxides furnished predominantly 2-acetoxy-6-substituted pyrazines, some of which were more selectively prepared by addition of zinc bromide and triethylamine to the reaction. Regioselectivity of the acetoxylation is discussed based upon heat of formation by AMI and AMI-COSMO for all possible isomers of each set.     

Self-crosslinkable polymers. IV. Copolymerization of 1-ethenyl-4-(2,3-epoxy-1-propoxy)benzene with vinylpyridines

Soluble and self-crosslinkable linear copolymers with pendant epoxy and pyridyl groups were obtained from 1-ethenyl-4-(2,3-epoxy-1-propoxy)benzene (M₁) and vinylpyridines (M₂) by the action of α,α′-azobisisobutyronitrile. The monomer reactivity ratios were determined in tetrahydrofuran at 60°C (r₁, r₂, and vinylpyridine given): 0.467, 0.638, 4-vinylpyridine; 0.556, 1.25, 2-vinylpyridine; 0.639, 1.38, 5-ethyl-2-vinylpyridine. The Q and e values for 1-ethenyl-4-(2,3-epoxy-1-propoxy)-benzene were calculated as 1.3–1.6 and ?1.1–?1.3, respectively, with the reported Q–e values for these vinylpyridines. The intrinsic viscosities of the copolymers were found to be 0.15–0.30 in tetrahydrofuran at 30°C and to be dependent on the copolymer composition. The copolymers with these vinylpyridines were amorphous, had no clear melting points, and became insoluble crosslinked polymers under heating without further addition of any curing agents.     

Heat capacity and magnetic phase transition of two-dimensional metal-assembled complex (NEt<Subscript>4</Subscript>)[{Mn<Superscript>III</Superscript>(salen)}<Subscript>2</Subscript>Fe<Superscript>III</Superscript>(CN)<Subscript>6</Subscript>]

Summary Heat capacity measurements of the two-dimensional metal-assembled complex, (NEt₄)[{Mn^III(salen)}₂Fe^III(CN)₆] [Et=ethyl, salen= N,N’-ethylenebis(salicylideneaminato) dianion], were performed in the temperature range between 0.2 and 300 K by adiabatic calorimetry. A ferrimagnetic phase transition was observed at T_c1=7.51 K. Furthermore, another small magnetic phase transition appeared at T_c2=0.78 K. Above T_c1, a heat capacity tail arising from the short-range ordering of the spins characteristic of two-dimensional magnets was found. The magnetic enthalpy and entropy were evaluated to be ΔH=291 J mol^-1 and ΔS=27.4 J K^-1 mol^-1, respectively. The experimental magnetic entropy agrees roughly with ΔS=Rln(5·5·2) (=32.5 J K^-1 mol^-1; R being the gas constant), which is expected for the metal complex with two Mn(III) ions in high-spin state (spin quantum number S=2) and one Fe(III) ion in low-spin state (S=1/2). The heat capacity tail above T_c1 became small by grinding and pressing the crystal. This mechanochemical effect would be attributed to the increase of lattice defects and imperfections in the crystal lattice, leading not only to formation of the crystal with a different magnetic phase transition temperature but also to decrease of the magnetic heat capacity and thus the magnetic enthalpy and entropy.     

Interaction of toxic lectin ricin with epithelial cells of rat small intestine in vitro.

To clarify the mechanism of oral toxicity of ricin, the interaction of ricin with the epithelial cells isolated from rat small intestine was compared in vitro with those of other plant lectins by two different determinations, i.e., viability and cytotoxicity. After incubation of the cells for 1 h at 37 degrees C with ricin, B-chain, castor bean hemagglutinin (CBH), soybean agglutinin (SBA), wheat germ agglutinin (WGA), concanavalin A (Con A), and peanut agglutinin (PNA), respectively, followed by staining with trypan blue, ricin and ricin B-chain as well as CBH and SBA were found to have effectively reduced the number of viable cells. On the contrary, only ricin inhibited protein synthesis in the cells and the effect was blocked by D-galactose. Additional experiments employing [125I]-labeled ricin strongly suggested that ricin was first bound via its B-chain to the galactosyl residues on the cell surface followed by internalization into cells as the whole 62 kDa molecule. These results infer first that ricin, as well as other lectins mentioned above, was able to reduce viability of the epithelial cells of rat small intestine by direct binding to the cell surface. The second effect, specific to ricin, was the inhibition of cellular protein synthesis.     

Effects of (+)-, (-)- and (+/-)-indenestrols A and B on microtubule polymerization.

Indenestrol A (IA) is a metabolite of diethylstilbestrol (DES), and indenestrol B (IB) is an analog of IA. IA was simply obtained from E,E-dienestrol in the presence of dilute sulfuric acid, and a mixture of IA and IB was formed by thermal cyclization of E,E-dienestrol. In order to elucidate the effects of optically active IA and IB on microtubule assembly, the IA and IB enantiomers were separated to greater than 99% purity by high-pressure liquid chromatography using a chiral column. The di(4-bromobenzoate) of (-)-IB was analyzed by X-ray crystallography and its absolute structure was determined as C(3)-S. The (+)-, (-)-, and (+/-)-indenestrols A and B were shown to be inhibitors of microtubule assembly in vitro using microtubule proteins from porcine brain. (+/-)-IB is more active than (+/-)-IA, and the order of inhibitory activity of the enantiomers on microtubule assembly was (+)-IB greater than (+)-IA greater than (-)-IA greater than (-)-IB.