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1.
Enzymatic synthesis of
A cell-free particulate enzyme preparation of Mycobacterium smegmatis ATCC 607 catalyzed the transfer of labeled mannose from GDP[14C]mannose to methyl-α-mannopyranoside (an exogenously added acceptor) to form a product that was characterized to be
. This tranmannosylase activity was specific for both the sugar nucleotide donor and methyl monosaccharide acceptor. The reaction was stimulated by the addition of various metal ions and had a pH optimum of 6.0. The apparent Km of this transmannosylase reaction for methyl-α-
-mannopyranoside was 35 mM.The possible relationship between this “artificial” mannosyl-transfer system and the “natural” system which leads to the formation of the oligomannosides and glycoproteins is discussed. 相似文献
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Determination of
Ichiro Ono Keizo Matsuda Sachiko Kanno 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1997,692(2)
A simple, rapid and sensitive two column-switching high-performance liquid chromatographic (HPLC) method with ultraviolet detection at 210 nm has been developed for the determination of
(AY4166, I) and its seven metabolites in human plasma and urine. Measurements of I and its metabolites were carried out by two column-switching HPLC, because metabolites were classified into two groups according to their retention times. After purification of plasma samples using solid-phase extraction and direct dilution of urinary samples, I and each metabolite were injected into HPLC. The calibration graphs for plasma and urinary samples were linear in the ranges 0.1 to 10 μg ml−1 and 0.5 to 50 μg ml−1, respectively. Recoveries of I and its seven metabolites were over 88% by the standard addition method and the relative standard deviations of I and its metabolites were 1–6%. 相似文献
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Synthesis of methyl
-Ribose was converted into methyl
and this, on tin-mediated allylation, gave a mixture of the 2-O-allyl and 3-O-allyl derivatives which were separated by chromatography. The more polar isomer was characterised as the 3-O-allyl derivative after conversion via
(which was also synthesised from
) into the known
. Methyl
was converted into methyl
via methyl
. 相似文献
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Manual and automated determination of
Daisy B. Whigan Alan E. Schuster 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1995,664(2)
This paper describes the determination of
and its metabolite (E)-5-(2-bromovinyl)uracil in urine. The method involves sample clean-up by liquid-liquid extraction with ethyl acetate followed by high-performance liquid chromatographic (HPLC) analysis. The sample preparation may be performed either manually or automatically using a Zymark Py-robotic system. The chloro analog of the parent compound, CV-araU, is used as the internal standard. As low as 0.1 μg of analyte per ml of urine can be measured. This sensitivity is adequate for pharmacokinetic studies but could be improved quite easily if necessary. 相似文献
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Process for the isolation of preparative quantities of
Paul A. Kroon Maria T. Garcia Conesa Ian J. Colquhoun Gary Williamson 《Carbohydrate research》1997,300(4)
Specific enzymes were used to hydrolyse sugarbeet pulp to facilitate the isolation of
in preparative amounts. The feruloylated arabinose disaccharide was purified by chromatography on Sephadex LH-20 and Bio-Gel P-2 and the structure confirmed by NMR and UV spectroscopy and high-performance liquid chromatography. 相似文献
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C, N CP MAS and high resolution multinuclear NMR study of methyl
Four new derivatives of methyl
were studied by 1H, 13C, 15N NMR in CDCl3 solutions and by 13C, 15N NMR in the solid state. The replacement of one aryl substituent by another has no influence on the proton and carbon chemical shifts within the sugar moiety, in solution. The differences in 13C chemical shifts Δ = δliquid - δsolid are significant for C-3 (deshielding of -3.4 to -3.8 ppm), C-5 and OMe but not observed for C-2, where the ureido substituent is linked, thus indicating that this fragment of the structure is rigid. The values of Δ in 15N chemical shifts of N-3′ are -2.3 to -2.8 ppm (increase of shielding in the solids); the effect of replacement of substituent at aromatic ring is larger than the contribution of intermolecular H-bond interaction. The values of 15.5–16.1 Hz for 1JC-1′-N and 21.2–21.5 Hz for 1JCO-N indicate that the two C---N-3′ bonds are of significant double bond character. 相似文献
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12.
Preparation and characterization of a new rhenium(V) complex containing the
Monica Santimaria Theodosia Maina Ulderico Mazzi Marino Nicolini 《Inorganica chimica acta》1995,240(1-2)
A new phosphine derivatized peptide tetradentate ligand containing the PN2S donor atom set,
cysteinyl methyl ester, was synthesized in good yields by coupling a phosphine group to protected Gly-
-Cys dipeptide. Complexation of the new ligand with rhenium proceeded in satisfactory yields by substitution reaction on ReVOCl3(PPh3)2 in a 1.2:1 molar ratio. The resulting rhenium complex was characterized by IR, FAB-MS, 1H and 31P NMR spectroscopy and was found to be neutral and diamagnetic. These studies revealed, that rhenium (V) in a trans-ReOCl2+ cor coordinates with the PN2S2− donor atom set formed by one neutral phosphine, one neutral thioether and two deprotonated amide groups of the ligand forming a neutral complex. High performance liquid chromatography tests verified the purity and high stability of the complex in solution for long periods of time. In alkaline organic media the complex transforms to an equally stable, more hydrophilic analogue, in which the methyl ester group of cysteine is hydrolyzed to the free carboxylate. 相似文献
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Cytogenetic evaluation of occupational exposure to external γ-rays and internal
M. Bauchinger E. Schmid H. Braselmann 《Mutation Research - Genetic Toxicology and Environmental Mutagenesis》1997,395(2-3)
Chromosome analyses were performed on peripheral lymphocytes from seven radiation workers exposed to external γ-radiation within maximum annual permissible dose limits during 11 to 22 years of employment. Five years prior to blood sampling, six workers had additionally incorporated the α-emitting radionuclide
which contributed between five to 25% of the total accumulated whole body dose in five workers and about 70% in one worker. For the radiation workers as a group, both the mean frequencies of symmetrical translocations measured by fluorescence in situ hybridisation (FISH)/chromosome painting and dicentrics+ring chromosomes scored in first division metaphases of conventional preparations were significantly elevated compared with respective controls. The mean biodosimetry estimate for the group was 270 mSv when based on stable translocations which compares well with the mean dose of 247 mSv based on official dosimetry records. The lower mean dose estimate of 160 mSv based on unstable dicentrics is compatible with the well-known loss of dicentrics from the circulating blood with time after exposure. 相似文献
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15.
α-
Jean-Paul Mornon Dyna Halaby Marc Malfois Patrick Durand Isabelle Callebaut Annette Tardieu 《International journal of biological macromolecules》1998,22(3-4)
New results obtained from a two-dimensional sequence analysis of the small heat shock protein (shsp) family are described. It is confirmed that the conserved C-terminal α-crystallin domain is essentially made of β-strands, most probably two groups of β-strands separated by a large loop. A direct correspondence between the putative β-strands that have been identified in shsps and the seven β-strands of a classical immunoglobulin-like fold is proposed. The hypothesis that the shsp family could belong to the immunoglobulin superfamily (IgSF) is consistent with the ubiquitous distribution and the multifunctional properties of the crystallins that are now emerging. 相似文献
16.
Mass spectrometric quantification of the mu opioid receptor agonist Tyr-
Olga O. Grigoriants Jih-Lie Tseng Robert R. Becklin Dominic M. Desiderio 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1997,695(2)
The mu opioid receptor agonist Tyr-
-Arg-Phe-Lys-Amide (
-Arg2-Lys4-Dermorphin1-4amide=DALDA) was infused continuously for 2 h into sheep. The presence of DALDA in ovine plasma was determined by reversed-phase high-performance liquid chromatography (RP-HPLC) and mass spectrometry (MS) in plasma samples that were obtained at different times during and following that infusion. A stable isotope-incorporated internal standard, deuterated DALDA (d5-DALDA), was used for the MS quantification of DALDA via the protonated molecule ion, (M+H)+, of DALDA and of d5-DALDA. Time-course data (μg DALDA ml−1 plasma vs. time) were obtained. Tandem MS (MS–MS) provided the product-ion spectrum of the (M+H)+ ion of DALDA in one of the samples to confirm the amino acid sequence of DALDA. 相似文献
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Reaction of FcCCo3(CO)9 with 2,3-bis(diphenylphosphino)maleic anhydride (bma). X-ray diffraction structure and redox properties of
The reaction between the tricobalt cluster FcCCo3(CO)9 (1) (where Fc = ferrocenyl) and the redox-active diphosphine ligand 2,3-bis(diphenylphosphino)maleic anhydride (bma) affords the new cluster
(3) in refluxing 1,2-dichloroethane or toluene. The cluster FcCCo3(CO)7(bma) (2), a logical precursor to 3, was observed in solution by IR spectroscopy when cluster 1 and bma were refluxed in the low boiling point solvent CH2Cl2; however, putative 2 could not be isolated due to its rapid conversion to the final product 3. Cluster 3 has been fully characterized in solution by IR and NMR (13C and 31P) spectroscopy and in the solid state by X-ray diffraction analysis.
, as the CH2Cl2 solvate, crystallized in the triclinic space group
for 3602 observed reflections with 13σ(I). Cyclic voltammetric investigations of 3 in CH2Cl2 reveal the presence of three reversible redox responses assigned to the 0/1+, 0/1−1, and 1−/2− redox couples. The nature of the HOMO and the two lowest unoccupied molecular orbitals (LUMO and SUMO) in 3 has been determined by carrying out extended Hückel calculations on the model compound
, the results of which are discussed relative to the observed electrochemistry of 3 and related cluster compounds. 相似文献
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