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PubMed2002

Solute-solvent interactions in micellar electrokinetic chromatography: IV. Characterization of electroosmotic flow and micellar markers.

A wide study of the compounds and procedures mostly used to determine the electroosmotic flow (EOF) and micelle elution times has been done in seven different micellar electrokinetic chromatography (MEKC) systems. These systems are formed from mixtures of an aqueous buffer with the surfactants sodium dodecyl sulfate, lithium dodecyl sulfate, lithium perfluorooctane sulfonate, sodium cholate, sodium deoxycholate, tetradecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide. The solvation parameter model has been used to evaluate the usefulness of the compounds studied as EOF or micellar markers in each of the seven MEKC systems. It is demonstrated that methanol, acetonitrile and formamide are the best EOF markers, and that dodecanophenone is the best micellar marker.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2001

Improvement of an in-gel tryptic digestion method for matrix-assisted laser desorption/ionization-time of flight mass spectrometry peptide mapping by use of volatile solubilizing agents.

The combination of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), in-gel enzymatic digestion of proteins separated by two-dimensional gel electrophoresis and searches of molecular weight in peptide-mass databases is a powerful and well established method for protein identification in proteomics analysis. For successful protein identification by MALDI-TOF mass spectrometry of peptide mixtures, critical parameters include highly specific enzymatic cleavage, high mass accuracy and sufficient numbers and sequence coverage of the peptides which can be analyzed. For in-gel digestion with trypsin, the method employed should be compatible both with enzymatic cleavage and subsequent MALDI-TOF MS analysis. We report here an improved method for preparation of peptides for MALDI-TOF MS mass fingerprinting by using volatile solubilizing agents during the in-gel digestion procedure. Our study clearly demonstrates that modification of the in-gel digestion protocols by addition of dimethyl formamide (DMF) or a mixture of DMF/N,N-dimethyl acetamide at various concentrations can significantly increase the recovery of peptides. These higher yields of peptides resulted in more effective protein identification.

Amino Acid Sequence↗
PubMed1988

Cyanide utilization and degradation by microorganisms.

Various microorganisms can produce (cyanogenesis) or degrade cyanide. They degrade cyanide either to detoxify it, or to use it as a source of nitrogen for growth. Significant amounts of cyanide are formed as a secondary metabolite by a wide range of fungi and a few bacteria by decarboxylation of glycine. When cyanide has been formed by the snow mould fungus it is degraded by conversion to carbon dioxide and ammonia via an unknown pathway. In contrast, cyanogenic bacteria either do not further catabolize cyanide or they convert it into beta-cyanoalanine by addition to cysteine or O-acetylserine. Several non-cyanogenic fungi that are pathogens of cyanogenic plants are known to degrade cyanide by hydration to formamide by the enzyme cyanide hydratase. Such fungi can be immobilized and used in packed-cell columns to continuously detoxify cyanide. ICI Biological Products Business market a preparation of spray-dried fungal mycelia, 'CYCLEAR', to detoxify industrial wastes. Novo Industri have also introduced a cyanidase preparation to convert cyanide directly into formate and ammonia. Bacteria have been isolated that use cyanide as a source of nitrogen for growth. Because cyanide, as KCN or NaCN, is toxic for growth, the bacteria (Pseudomonas fluorescens) have to be grown in fed-batch culture with cyanide as the limiting nutrient. Cyanide is converted to carbon dioxide and ammonia (which is then assimilated) by an NADH-linked cyanide oxygenase system.

Bacteria↗
PubMed2003

General suitability of techniques for in situ detection of apoptosis in small intestinal epithelium.

The present study was designed to evaluate different techniques for the in situ detection of apoptosis in human and rat small intestinal epithelium. The techniques included light microscopy (LM) and transmission electron microscopy (TEM) observation of epoxy resin-embedded tissue, scanning electron microscopy (SEM), TUNEL assay, and antibodies directed against caspase cleavage products of caspase 3, cytokeratin 18 (CK 18), and apoptotic single-strand DNA (ssDNA). All techniques, if the labeling was positive, showed apoptotic cells exclusively at the villus tip. LM and TEM were the most reliable and revealed morphological signs typical of cells that have died via apoptosis. SEM indicated the extension of the process. The antibody recognizing cleaved caspase 3 could be considered an appropriate marker for apoptotic epithelial cells in human and rat small intestine. However, the majority of epithelial cells lining the proximal small intestinal villus contained only low levels of intact CK 18. Therefore, sufficient amounts of cleaved CK 18 for immunohistochemical detection were not generated during apoptosis, rendering the application of the antibody inappropriate. The antibody detecting formamide-denatured ssDNA in apoptotic cells was both suitable and reliable; however, the particular staining procedure used compromised the tissue preservation. In comparison to this, the TUNEL assay was less reliable. Although it was performed with a commercially available ready-to-use kit, its application conditions had to be adjusted for each specimen on the basis of the findings produced by other techniques.

Aged↗
PubMed1994

[Antimycobacterial indole derivatives].

1,3-Dinitro-2-(indol-3'-yl)-propanes 3 are synthesized by Michael reaction of nitromethane with the indolylnitroethenes 2. Reaction of the aldehydes 4 and 10 with the benzylamines 12 as well as the reaction of the indolylalkylamines 6a and 9a with the benzaldehydes 11 lead to Schiff bases which are reduced to N-benzyl-(indol-3-ylmethyl)-amines 13 and N-benzyl-(indol-3-ylethyl)-amines 14, respectively; tert amines 16 are synthesized via the formamides 15, amines 18 are prepared according to Mannich. Inhibitory effects on Mycobacterium tuberculosis H 37 Ra are investigated, a structure-activity relationship is discussed.

Anti-Bacterial Agents↗
PubMed1995

1H-, 13C-, and 113Cd-NMR study of the Cd(II) complex of a blocked peptide, Z-Cys-Ala-Pro-His-OMe, in organic solvents.

The Cd(II) complex of a peptide, Z-Cys-Ala-Pro-His-OMe was prepared and characterized by absorption, CD, 1H-, 13C-, and 113Cd-nmr, and nuclear Overhauser effect spectroscopy (NOESY) spectra to show the coordination of cysteine thiolate and histidine imizazole to Cd(II) ion. The NOESY spectra in dimethyl formamide showed that the cysteine residue was in proximity to the histidine residue. These results reveal the chelation of Z-Cys-Ala-Pro-His-OMe to Cd(II) ion in solution. Temperature-dependent dissociation equilibrium of histidine imidazole in solution was observed in this complex. Structural features of the chelating peptide are discussed.

Amino Acid Sequence↗
PubMed2002

Arylsulfotransferase from Clostridium innocuum-A new enzyme catalyst for sulfation of phenol-containing compounds.

Arylsulfotransferase (AST, EC 2.8.2.22), an enzyme capable of sulfating a wide range of phenol-containing compounds was purified from a Clostridium innocuum isolate (strain 554). The enzyme has a molecular weight of 320 kDa and is composed of four subunits. Unlike many mammalian and plant arylsulfotransferases, AST from Clostridium utilizes arylsulfates, including p-nitrophenyl sulfate, as sulfate donors, and is not reactive with 3-phosphoadenosine-5'-phosphosulfate (PAPS). The enzyme possesses broad substrate specificity and is active with a variety of phenols, quinones and flavonoids, but does not utilize primary and secondary alcohols and sugars as substrates. Arylsulfotransferase tolerates the presence of 10 vol% of polar cosolvents (dimethyl formamide, acetonitrile, methanol), but loses significant activity at higher solvent concentrations of 30-40 vol%. The enzyme retains high arylsulfotransferase activity in biphasic systems composed of water and nonpolar solvents, such as cyclohexane, toluene and chloroform, while in biphasic systems with more polar solvents (ethyl acetate, 2-pentanone, methyl tert-butyl ether, and butyl acetate) the enzyme activity is completely lost. High yields of AST-catalyzed sulfation were achieved in reactions with several phenols and tyrosine-containing peptides. Overall, AST studied in this work is a promising biocatalyst in organic synthesis to afford efficient sulfation of phenolic compounds under mild reaction conditions.

Animals↗
PubMed1980

Chelating, film-forming, and coagulating ability of the chitosan-glucan complex from Aspergillus niger industrial wastes.

Waste mycelia of Aspergillus niger from a citric acid production plant are simply treated with boiling 30-40% NaOH aqueous solutions for 4-6 hr to obtain the insoluble chitosan-glucan complex whose infrared, ESR, and x-ray diffraction spectra are reported. A number of transition- and post-transition-metal ions are chelated and collected by chitosan-glucan with higher yields than by animal chitosan. Immediate flocculation occurs upon mixing chitosan-glucan dispersions with alginate and polymolybdate solutions. Membranes are also obtained from chitosan-glucan dispersions in acetic acid or in chloral and dimethyl formamide mixtures.

Aspergillus niger↗
PubMed1989

Separation of some antihistamines on impregnated TLC silica plates.

Different metal salts have been tried as impregnating reagents for developing TLC separation schemes for some antihistamines on silica gel 'G' plates, using a new solvent system benzene + dimethyl formamide + acetic acid (30:10:7). Spots were visualized by spraying with a solution of Dragendroff's reagent.

Chromatography, Thin Layer↗
PubMed2001

High performance liquid chromatography analysis of 9-(2',3'-dideoxy-2'beta-fluoro-D-threo-penta furanosyl) adenine and its metabolite in human plasma using solid-phase extraction on a polyfluorinated reversed stationary phase.

A quick and sensitive reversed-phase HPLC method has been developed for the analysis of 2'-beta -fluoro-2',3'-dideoxy adenosine (F-ddA), the acid-stable anti-AIDS drug, and its metabolite 2'-fluoro-2',3'-dideoxy inosine (F-ddI) in human plasma using polyfluorinated stationary phase column (Fluo fix, 15 cm, 4.0 mm i.d., 5 microm particle size). The mobile phase consisted of ammonium phosphate buffer solution (10 mM) adjusted with phosphoric acid 85% to pH 6.8:dimethyl formamide (97:3, v/v). F-ddA and F-ddI were monitored by UV-visible detector at 258 and 247 nm, respectively. The recoveries of F-ddA and F-ddI from plasma using a C(18) solid-phase extraction cartridge were 99.2% and 99.7%, respectively.

Anti-HIV Agents↗
PubMed1981

Mass spectrometry of 2-substituted 5-nitro-2-furyl thiazoles. Identification of microsomal nitroreduction products by electron impact mass spectrometry.

The electron impact mass spectral fragmentation of nitro heterocyclic carcinogens N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide, 2-amino-4-(5-nitro-2-furyl)thiazole, 2-methyl-4-(5-nitro-2-furyl)thiazole and 2-methylamino-4-(5-nitro-2-furyl)thiazole were studied. The molecular ions undergo two modes of cleavage: one giving [M-84]+ ions which include the 2-substituted thiazole ring, while the other gives rise to the fragment [M-74]+ ions. The products of anaerobic microsomal nitroreduction of 2-methyl-4-(5-nitro-2-furyl)thiazole were isolated and purified by high-pressure liquid chromatography. The metabolites undergo different fragmentation patterns compared to the parent nitro analogs. Metabolites from anaerobic enzymatic reduction showed identical gas chromatographic, high-pressure liquid chromatographic and thin-layer chromatographic properties to the chemically synthesized material. The metabolites were identified as 1-(2-methyl-4-thiazolyl)-3-cyano-1-propenone and 1-(2-methyl-4-thiazolyl)-3-cyano-1-propane by mass spectral fragmentation pattern.

Animals↗
PubMed1990

A rapid and highly sensitive method for the quantitative determination of dexamethasone in plasma, synovial fluid and tissues by combined gas chromatography/negative ion chemical ionization mass spectrometry.

A new, simple and highly sensitive assay is developed for the quantitative measurement of very low levels of dexamethasone in human plasma, synovial fluid and tissues following a topical administration of the drug. Dexamethasone and the internal standard, flumethasone, are measured by gas chromatography/negative ion chemical ionization mass spectrometry with methane as the reagent gas. After a three-step extraction procedure, the two compounds of interest are converted to their trimethylsilyl ether derivatives using trimethylsilylimidazole and formamide as the base catalyst. Under soft derivatization conditions only one chromatographic peak corresponding to the trisubstituted derivative is observed. The mass spectrometer is focused to monitor abundant and stable characteristic high-mass ions (m/z 446 and 464) which are generated in the ion source by an electron capture process. This assay requires only 1 ml of plasma or 0.5 ml of synovial fluid and the detection limit of the method is equal to 0.1 ng ml-1 with a relative standard deviation lower than 6%.

Adipose Tissue↗
PubMed2006

New chemical constituents from the endophyte Streptomyces species LR4612 cultivated on Maytenus hookeri.

From solid cultures of the biologically important endophyte Streptomyces species LR4612, cultivated on Maytenus hookeri, four new and two known compounds were isolated. The new compounds were identified as (2S*,3S*)-5-amino-3-hydroxy-5-oxopentan-2-yl 3-(formylamino)-2-hydroxybenzoate (1), N-[(3R*,4R*)-3-amino-3,4-dihydro-4-methyl-2,6-dioxo-2H,6H-1,5-benzodioxocin-10-yl]formamide (2), (5beta,6alpha)-6,11-dihydroxyeudesmane (3), and 5-(6,7-dihydroxy-6-methyloctyl)furan-2(5H)-one (4); the known compounds were elucidated as sorbicillin (5) and N-acetyltyramine (6). The structures were established by HR-ESI-MS and in-depth NMR analyses.

Maytenus↗
PubMed2003

Electron-transfer chemistry of the iron-molybdenum cofactor of nitrogenase: delocalized and localized reduced states of FeMoco which allow binding of carbon monoxide to iron and molybdenum.

The electron-transfer chemistry of the isolated iron-molybdenum cofactor of nitrogenase (FeMoco) has been studied by electrochemical and spectroelectrochemical methods. Two interconverting forms of the cofactor arise from a redox-linked ligand isomerism at the terminal iron atom; this is attributed to rotamerism of an anionic N-methyl formamide ligand bound at this site. FeMoco in its EPR-silent oxidised state is shown to undergo three successive one-electron transfer steps. We argue that the first and second redox processes are associated with electron-transfer delocalised over the iron-sulfur core of the cofactor, whilst the third irreversible process is localised on molybdenum. This is strongly reinforced by spectroelectrochemical studies under (12)CO and (13)CO which reveal two independent carbon monoxide binding sites that are specifically associated with the second (iron core) and third (molybdenum) electron-transfer processes and which give rise to terminal nu((12)CO) bands at 1885 and 1920 cm(-1) respectively. Moreover, in parallel with earlier studies on the enzyme system, it is shown that at low CO concentration, carbon monoxide binds to the cofactor in bridging modes, with nu(CO) bands at 1835 and 1808 cm(-1) that are interconverted by single-electron transfer. Importantly we show that the contentious overall 2e difference in the assignment of the metal oxidation levels in the resting state of the enzyme-bound cofactor, arising from analysis of (57)Fe ENDOR and Mössbauer data, can be resolved in the light of the electron-transfer chemistry of the isolated cofactor described herein.

Binding Sites↗
PubMed2005

Contrasting behavior in azide pyrolyses: an investigation of the thermal decompositions of methyl azidoformate, ethyl azidoformate and 2-azido-N, N-dimethylacetamide by ultraviolet photoelectron spectroscopy and matrix isolation infrared spectroscopy.

The thermal decompositions of methyl azidoformate (N3COOMe), ethyl azidoformate (N3COOEt) and 2-azido-N,N-dimethylacetamide (N3CH2CONMe2) have been studied by matrix isolation infrared spectroscopy and real-time ultraviolet photoelectron spectroscopy. N2 appears as an initial pyrolysis product in all systems, and the principal interest lies in the fate of the accompanying organic fragment. For methyl azidoformate, four accompanying products were observed: HNCO, H2CO, CH2NH and CO2, and these are believed to arise as a result of two competing decomposition routes of a four-membered cyclic intermediate. Ethyl azidoformate pyrolysis yields four corresponding products: HNCO, MeCHO, MeCHNH and CO2, together with the five-membered-ring compound 2-oxazolidone. In contrast, the initial pyrolysis of 2-azido-N,N-dimethyl acetamide, yields the novel imine intermediate Me2NCOCH=NH, which subsequently decomposes into dimethyl formamide (HCONMe2), CO, Me2NH and HCN. This intermediate was detected by matrix isolation IR spectroscopy, and its identity confirmed both by a molecular orbital calculation of its IR spectrum, and by the temperature dependence and distribution of products in the PES and IR studies. Mechanisms are proposed for the formation and decomposition of all the products observed in these three systems, based on the experimental evidence and the results of supporting molecular orbital calculations.

Journal Article↗
PubMed1979

Synthesis of difuran derivatives and their biological activity.

Visnaginone and khellinone react with chloroacetamide and chloroacetonitrile in dimethyl formamide to give either the cyclised benzo[1,2-b : 5,4-b']difuran or the open form depending on the heating period. The antibacterial activity of the compounds was tested.

Anti-Bacterial Agents↗
PubMed1993

The fate of cryopreserved nerve isografts and allografts in normal and immunosuppressed rats.

Donor Schwann cells, perineurial cells, and vasculature are known to survive in grafts of peripheral nerve. In the present study, we attempted to cryopreserve nerve to determine whether these cellular components of nerve would survive after transplantation and support host axonal regeneration through the graft. Four-centimeter lengths of peroneal nerves were removed from inbred adult American Cancer Institute (ACI) rats and placed into vials that contained a cryoprotective mixture of dimethyl sulfoxide and formamide (DF) at room temperature. Each vial with nerves in DF was cooled at a rate of 1-1.5 degrees C/minute down to -40 degrees C at which point the vials were plunged into liquid nitrogen at -196 degrees C. After 5 weeks of storage, the nerves were thawed and DF removed. Some of the cryopreserved-thawed ACI nerves were transplanted as isografts into the legs of ACI rats. Other ACI nerves were used as allografts and inserted into immunologically normal Fischer (FR) rats that were untreated or were immunosuppressed with the drug Cyclosporin A (Cy-A). At surgery, only one end of the nerve graft was joined to the cut proximal end of the peroneal nerve of the host. The cellular elements of ACI grafts were present at 5 weeks in grafts removed from ACI rats and FR rats treated with Cy-A. Non-immunosuppressed FR rats rejected ACI nerves as did FR rats in whom Cy-A was stopped after 5 weeks of treatment. All surviving ACI grafts underwent Wallerian degeneration and consisted of columns of Schwann cells, which in their proximal portion were associated with regenerating host axons. The donor perineurial sheath and vasculature were also present in surviving grafts. ACI isografts only were examined 20 weeks postoperatively. All normal tissue components survived in these older grafts and contained regenerated and myelinated host axons throughout their 4 cm lengths. These results demonstrated that the cellular elements of nerve can be cryopreserved, and after transplantation, survive and function. Because nerves survived after prolonged cryopreservation, it seems feasible to establish a nerve bank from which grafts can be withdrawn to repair gaps in injured nerves. However, cryopreserved nerves used as allografts remain immunogenic and require immunosuppression for their survival.

Animals↗
PubMed1988

Flow cytometric detection of ribosomal RNA in suspended cells by fluorescent in situ hybridization.

A method using flow cytometry and fluorescent in situ hybridization (ISH) to detect RNA in cells is described. L1210 murine leukemia cells were fixed with 1% formaldehyde in HEPES buffered Hank's balanced salt solution (HH) followed by 70% ethanol. Endogenous RNAses were blocked by diethylpyrocarbonate treatment. Single-stranded sense and antisense RNA probes, labeled with biotin-11-UTP, were transcribed from a 2.1 kb 28S ribosomal RNA (rRNA) gene fragment subcloned into the pGEM2 plasmid. For good results, it was essential that the probes were degraded to 100-150 nucleotides before use. Hybridization was performed at 45 degrees C in 50% formamide, 5 x SSC, 0.5% SDS. Hybrids were detected with streptavidin-FITC by flow cytometry. Antisense rRNA probe signal was 100 times higher than the background. The hybrids were largely resistant to RNAse and melted at high temperature. The sense probe also gave a signal (5 times background), which was not RNAse resistant and was attributed to the presence of internal inverted repeats in the ribosomal RNA. When sufficient background reduction can be achieved, it is expected that as few as ten mRNA molecules per cell can be detected with the fluorescent in situ hybridization method.

Animals↗