SEARCH · PubMed Health

Results for “DIMETHYLFORMAMIDE”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 649 records · Page 36Linked to original sources

PubMed1995

Determination of urinary valproylcarnitine by gas chromatography-mass spectrometry with selected-ion monitoring.

A modified method for the determination of valproylcarnitine in urine samples of patients receiving sodium valproate by gas chromatography-mass spectrometry with selected-ion monitoring is described. The chemically analogous internal standard 2-ethylpentanoylcarnitine was added to the urine samples. Valproic acid and its metabolites were removed by extraction with chloroform at pH 5.0. The samples were then applied onto a C18 Sep-Pak column. Inorganic and water soluble compounds were washed out with water. Valproylcarnitine and internal standard were eluted with methanol and were derivatized to the corresponding acyl-containing lactones by heating at 100 degrees C for 60 min in dimethylformamide. Urinary valproylcarnitine levels of epileptic patients receiving valproate were determined according to the present method. The data obtained might be useful for diagnosis of carnitine deficiency.

Calibration↗

PubMed2005

1H NMR studies of homo and mixed ligand complexes of Tl+ ion with several polyazamacrocycles.

Proton NMR was used as a probe to study the interaction of the Tl(+) ion with 9-18-membered macromonocyclic tri-, tetra-, and hexaamines in dimethylformamide (DMF) solution. A study of proton chemical shift of ligands as a function of Tl(+) ion to ligand mole ratio revealed that the complexation reactions occur in a stepwise manner. Formation of a 1:1 complex is followed by the addition of a second complexant molecule to form a homo-sandwich complex for triazamacrocycle ligands and a mixed ligand complex in the case of hexamethylhexacyclen (HMHCY) and 1,4,7-triazacyclononane ([9]aneN(3)). The formation constants of resulting 1:1 and 1:2 (homo and mixed ligand sandwich) complexes in DMF solution were evaluated from computer fitting of the chemical shift-mole ratio data. The mixed ligand complexes may be more stable than the parent complex in which both ligands are the same. The influence of cavity size and substitution of methyl groups on nitrogen atoms of the macrocyclic ring the stability of the resulting complexes is discussed. The geometries of the tri- and tetraazamacrocycle ligands and their Tl(+) ion complexes were optimized by an ab initio method, and the calculated binding energies of resulting complexes were compared. Both the experimental and theoretical studies revealed that, in the presence of methyl groups, the stability of triazamacrocycle complexes with Tl(+) ion was decreased.

Dimethylformamide↗

PubMed2004

Studies on the methyl isocyanate adducts with globin.

Isocyanates such as methylisocyanate (MIC), an intermediate in the synthesis of carbamate pesticides, or diisocyanates, used in the production of plastics, are highly reactive toxic compounds that spontaneously bind to biological macromolecules. In vivo formation of stable adducts with blood protein globin offers possibilities for biomonitoring of internal exposure to various reactive species. Thus, biomonitoring of the isocyanates through determination of their specific adducts with globin is a challenge. In this study, we characterized the adducts formed in human globin upon treatment with 100-fold molar excess of MIC. The globin was subject to enzymatic hydrolysis with pronase, and the hydrolysate was analysed by high performance liquid chromatography with positive atmospheric pressure chemical ionization mass spectrometric detection (HPLC/APCI-MS). The two major MIC adducts were those with N-terminal Val and side-chain of Lys, as confirmed by comparison with the synthetic standards. About 20 other adducts were observed, and several of them were tentatively identified using their MS and MS/MS spectra. Whereas detection of the adducts with Tyr and His was expected, the adducts with Trp and Phe, and a Lys adduct containing two MIC moieties, were probably analytical artifacts resulting from the transcarbamoylation during globin hydrolysis rather than products of direct carbamoylation. The other detected products were MIC-Val-His, derived from the N-terminal dipeptide of globin beta-chain, and dipeptides consisting of MIC-Lys attached to Gly, Val, Leu, Thr, and Glu. Failure to detect the corresponding non-modified dipeptides suggests that the pronase action may be hampered by the amino acid modification. MIC is known as a metabolic intermediate of the industrial solvents N,N-dimethylformamide (DMF) and N-methylformamide (MF) in humans and rats. The HPLC/APCI-MS analysis of globin from rats injected with DMF or MF, 1000 mg/kg, revealed the presence of the MIC adducts with both Val and Lys. The level of the Val adduct in globin from the DMF-dosed rats, determined using Edman degradation and GC/MS, was ca. 40 nmol/g, which is a level common in workers occupationally exposed to DMF. This suggests that also the Lys adduct in such human globin samples can be feasible to analysis and is therefore considered for further studies as a potential biomarker of exposure to DMF.

Animals↗

PubMed2005

Photocatalytic oxidation of gaseous DMF using thin film TiO2 photocatalyst.

The heterogeneous photocatalytic oxidation of gaseous N,N'-dimethylformamide (DMF) widely used in the manufacture of synthetic leather and synthetic textile was investigated. The experiments were carried out in a plug flow annular photoreactor coated with Degussa P-25 TiO2. The oxidation rate was dependent on DMF concentration, reaction temperature, water vapor, and oxygen content. Photocatalytic deactivation was observed in these reactions. The Levenspiel deactivation kinetic model was used to describe the decay of catalyst activity. Fourier transform infrared (FTIR) was used to characterize the surface and the deactivation mechanism of the photocatalyst. Results revealed that carbonylic acids, aldehydes, amines, carbonate and nitrate were adsorbed on the TiO2 surface during the photocatalytic reaction. The ions, NH4+ and NO3-, causing the deactivation of catalysts were detected on the TiO2 surface. Several treatment processes were applied to find a suitable procedure for the regeneration of catalytic activity. Among these procedures, the best one was found to be the H2O2/UV process.

Air Pollution, Indoor↗

PubMed2005

Dechlorination of polychlorinated organic compounds by electrochemical reduction with naphthalene radical anion as mediator.

Electrochemical reduction with electrochemically generated naphthalene radical anion in N,N-dimethylformamide was applied to the dechlorination of five representative POPs, namely HCB, lindane, DDT, PCP and aldrin. Rapid and complete dechlorination was possible for lindane and DDT to give nearly quantitative yields of benzene and 1,1-diphenylethane, respectively. HCB was reduced through complex reaction pathways to yield unknown products. Dechlorination of PCP and aldrin beyond dichlorinated compounds was difficult because of their very negative reduction potential. The reaction pathways for each dechlorination were proposed with the identification of intermediates.

Chromatography, High Pressure Liquid↗

PubMed2005

Liquid chromatography determination of natural dyes in extracts from historical Scottish textiles excavated from peat bogs.

Textiles excavated from Scottish sites belonging now to the collections of the National Museums of Scotland, including seventeenth century textiles from peat bogs in the Scottish Highlands and Islands, were selected for analysis by high performance liquid chromatography with photodiode array detection (PDA HPLC) to detect whether any dyes remained and, if so, to identify their biological sources. Dye components were identified in 36 of the 81 samples analysed. Although it was not possible to identify the exact sources of the dyestuffs because of the wide-spread occurrence of these natural dyes components, the study has shown that textiles previously not thought to have been coloured had detectable traces of dye. Before the historical textiles were analyzed, an improved extraction procedure that combined the routine acid hydrolysis method with one using dimethylformamide (DMF) was applied. The DMF method enabled increased recovery of major flavonoid and anthraquinoid compounds, and very high efficiency of recovery of indigotin even in textiles with no colour visible, thereby complementing the acid hydrolysis method already in use. Extracts from historical thread samples were analysed by PDA HPLC using a reversed-phase gradient system comprising of a C18 column (150 mm x 4.6 mm i.d., 25 +/- 1 degrees C) with water, methanol and o-phosphoric acid at an eluent flow rate of 1.2 ml/min. A preliminary investigation to improve the detection limits further for a selection of natural dyes was made by comparing results from the 4.6mm internal diameter (i.d.) column with a narrow bore C18 column (2.1 mm i.d.). An increase in the detector response was observed for narrow-bore column proving its possibility of enhancement of sensitivity.

Animals↗

PubMed2004

Miscellaneous hydrocarbon solvents.

The solvents discussed in this article are common solvents not categorized as halogenated, aromatic, or botanical. The solvents discussed are categorized into two groups: hydrocarbon mixtures and single agents. The hydrocarbon mixtures discussed are Stoddard solvent, naphtha, and kerosene. The remaining solvents described are n-hexane, methyl n-butyl ketone, dimethylformamide, dimethyl sulfoxide, and butyl mercaptans. Effects common to this group of agents and their unique effects are characterized. Treatment of exposures and toxic effects of these solvents is described, and physiochemical properties and occupational exposure levels are listed.

Alkanes↗

PubMed2005

Improved protein-adsorption-resistant property of PES/SPC blend membrane by adjustment of coagulation bath composition.

To improve surface protein-adsorption-resistant property of polyethersulfone (PES) membranes, soybean phosphatidylcholine (SPC) was added to PES casting solution. The blend membranes were prepared by a phase inversion method in a wet process. The surface of PES/SPC blend membranes was characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). XPS data revealed that the phosphorylcholine (PC) groups were concentrated at the surface by changing the composition of coagulation bath. Addition of N,N-dimethylformamide (DMF) in coagulation bath could prolong coagulation time and facilitate the migration of SPC from polymer bulk to membrane surface. The PES/SPC blend membranes dramatically reduced BSA and fibrinogen adsorption compared to PES control membrane due to effective immobilization of PC groups at the surface of PES/SPC blend membranes.

Adsorption↗

PubMed2005

Antioxidant activity of different sulfate content derivatives of polysaccharide extracted from Ulva pertusa (Chlorophyta) in vitro.

Polysaccharide extracted from Ulva pertusa (Chlorophyta) is a group of sulfated heteropolysaccharide; for simplicity, the sulfated polysaccharide is referred to as ulvan in this paper. In this study, different sulfate content ulvans were prepared with sulfur trioxide/N,N-dimethylformamide (SO3-DMF) in formamide, and their antioxidant activities were investigated including scavenging activity of superoxide and hydroxyl radicals, reducing power and metal chelating ability. As expected, we obtained several satisfying results, as follows: firstly, high sulfate content ulvans had more effective scavenging activity on hydroxyl radical than natural ulvan. Secondly, comparing with natural ulvan, high sulfate content ulvans exhibited stronger reducing power. Thirdly, HU4 (sulfate content, 30.8%) and HU5 (sulfate content, 32.8%) showed more pronounce chelating ability on ferrous ion at high concentration than other samples.

Antioxidants↗

PubMed2005

Fragmentation pathway for glutamine identification: loss of 73 Da from dimethylformamidine glutamine isobutyl ester.

A fragmentation mechanism for the neutral loss of 73 Da from dimethylformamidine glutamine isobutyl ester is investigated. Understanding this mechanism will allow to improve the identification and quantification of 15N-labeled and unlabeled glutamine and the distinguishing of glutamine and glutamic acid by electrospray ionization (ESI)-tandem mass spectrometry. Before mass spectrometry analysis, glutamine and glutamic acid are derivatized with dimethylformamide dimethyl acetal and isobutanol to form dimethylformamidine isobutyl ester. Derivatization conditions are modified based on an existing method to ensure complete derivatization of glutamic acid and to prevent the hydrolysis of glutamine. The fragmentation mechanism of dimethylformamidine glutamine isobutyl ester is studied and possible fragmentation pathways are proposed. Based on the fragmentation mechanism, a quantification method is developed to quantify both 15N-labeled and unlabeled glutamine and glutamic acid at a series of different neutral losses by performing multiple-reaction monitoring (MRM) scans in a triple-quadrupole mass spectrometer. Labeled glutamine includes 15N-amide labeled, 15N-amine labeled glutamine and glutamine 15N-labeled at both amide and amine positions. Deuterium labeled glutamine and glutamic acid are used as internal standards. Isotope effects are characterized for 15N labeled and deuterium labeled glutamine. It is found that the same method can be used to distinguish aspartic acid from asparagine. This study will improve the application of MS/MS for amino acid quantification and stable isotope labeling metabolism studies.

Butanols↗

PubMed2006

Effects of water-miscible solvents and polyhydroxy compounds on the structure and enzymatic activity of thermolysin.

The effect of organic solvents (n-propanol, isopropanol, dimethylformamide and dimethylsulfoxide) on the structure, activity and stability of thermolysin was the focus of this investigation. Results show the ability of the solvents to cause mixed inhibition of thermolysin, which was indicated by kinetic and structural studies (near-UV CD spectra and intrinsic fluorescence). Inhibitory effect of the solvents increased with increments in solvents logP. Thermoinactivation of thermolysin was studied at 80 degrees C in 50% of solvents and showed that with the increase in solvent hydrophobicity, thermal stability of the enzyme decreased. For the stabilization of thermolysin at high temperature, additives such as glycerol, sorbitol and trehalose were employed. In the presence of DMF with a relatively low logP, trehalose was shown to be a good stabilizer, whereas glycerol had a marked stabilization effect in the presence of n-propanol and isopropanol with a relatively high logP. Consequently, it was concluded that the stabilizing effect of additives can be correlated with the logP of solvents.

1-Propanol↗

PubMed2005

Determination of DMF modified DNA base N4-methylcarbamoylcytosine in human urine using off-line sample clean-up, two-dimensional LC and ESI-MS/MS detection.

A sensitive internal standard method for the analysis of a DNA-adduct of N,N-dimethylformamide (N4-methylcarbamoylcytosine, NMC-C) in human urine has been developed. A sample pre-treatment involving an acidic hydrolysis is followed by the sample clean-up performed with solid-phase extraction (SPE) technique using a cation-exchange resin. A two-dimensional liquid chromatography is used to separate the target analyte from the matrix using first a C18 reversed phase column with incorporated hydrophilic moieties and then a C8 bonded reversed phase column for the final separation. Quantification is carried out by positive electrospray ionisation and mass spectrometry detection of the transitions from molecule ions to product ions (169-->112 and 172-->115) for the analyte and the labelled internal standard, respectively. The detection limit in urine reaches down to 8 ng/L (48 pmol/L). In the general population NMC-C could not be detected. In 10 out of 32 urine samples of occupationally to DMF exposed subjects NMC-C could be detected. The concentrations ranged up to 172 ng/L (1023 pmol/L) with a 95th percentile of 121 ng/L (720 pmol/L).

Air Pollutants, Occupational↗

PubMed2005

Development of a solid phase microextraction-gas chromatography method to determine N-hydroxymethyl-N-methylformamide and N-methylformamide in urine.

A headspace solid phase microextraction (SPME) method has been developed to determine metabolites of dimethylformamide, N-hydroxymethyl-N-methylformamide, and N-methylformamide (NMF) as NMF in urine by gas chromatography with nitrogen-phosphorus detector (GC-NPD). An SPME holder with a 65-microm PDMS/DVB fiber coating was used. Optimal desorption conditions were 250 degrees C for 1 min, adsorption at 80 degrees C for 15 min, and 3.00 mL of sample in the headspace vial. The method presented good resolution, repeatability, recovery, detection limit, ruggedness and response linearity.

Chromatography, Gas↗

PubMed2005

Effect of charge transfer bands on the photo-induced DNA cleavage activity of [1-(2-thiazolylazo)-2-naphtholato]copper(II) complexes.

Ternary copper(II) complex [Cu(TAN)(O2CMe)] (1), where H-TAN is 1-(2-thiazolylazo)-2-naphthol, is prepared and structurally characterized by X-ray crystallography. The complex has a distorted square pyramidal (4+1) CuN2O3 coordination geometry with the acetate showing chelating axial-equatorial binding mode and TAN as a tridentate ligand bonded to the metal in the basal plane. Complex 1 is one-electron paramagnetic and displays ligand-to-metal charge transfer bands at 575 and 398 nm in dimethylformamide. The reactions of 1 with bases (B) like 1,10-phenanthroline (phen) and kanamycin-A (kan-A) afford ternary complexes of formulation [Cu(TAN)B]+ (B=phen, 2; kan-A, 3) under in situ reaction conditions. Complexes 2 and 3, prepared to explore their DNA binding and photo-induced DNA cleavage activity, display good binding propensity to calf thymus (CT) DNA giving a relative order: 2-3>1. The apparent binding constant (Kapp) for 1 is determined as 9.8 x 10(5)M(-1) from fluorescence quenching experiments using ethidium bromide. The quenching constants (K) values of 1-3, obtained from the Stern-Volmer plots, are 0.28, 0.52 and 0.49, respectively. All the complexes show photo-induced DNA cleavage activity when irradiated with a monochromatic UV light of 365 nm wavelength. A 200 microM complex 1 cleaves approximately 75% supercoiled (SC) DNA on 2h exposure time at 365 nm. A 50 microM solution of 1 in presence of 100 microM phen and kanamycin-A cleaves approximately 99% and approximately 60% SC DNA to its nicked circular form, respectively, for an exposure of 30 min. The complexes also exhibit significant cleavage of SC DNA on irradiation with visible light of wavelengths 532, 575 and 632.8 nm. Control experiments reveal the minor groove binding nature of the complexes. The cleavage reactions involve the formation reactive hydroxyl species as significant inhibition in the presence of dimethyl sulfoxide (DMSO) and catalase is observed. There is no apparent inhibition in cleavage in the presence of singlet oxygen quenchers like sodium azide. The cleavage activity has been found to be higher at the CT band position of 575 nm in comparison to those at 532 and 632.8 nm. The results indicate the involvement of the CT band in the photo-excitation process.

Binding Sites↗

PubMed2005

Application of 2-acetylbutyrolactone to spectrofluorimetry: fluorescence properties of Schiff bases derived from 2-acetylbutyrolactone and spectrofluorimetric determination of primary amine-containing compounds.

2-Acetylbutyrolactone (ABL) has been characterized for use as a fluorogenic reagent for the spectrofluorimetric determination of primary amines. The reagent forms strongly fluorescent Schiff bases upon the reaction with primary amines in acid-catalized aqueous solutions or in dimethylformamide (DMF). Sulfamethoxazole (SMX) and ampicillin sodium (AMP Na) were used as model amines of type ArNH(2) and RNH(2), respectively. The reaction conditions, fluorescence spectral properties and the stability of the derivatives have been investigated. The chemistry and the pathway of the reaction have been discussed. Calibration data, accuracy, precision, limits of detection, limits of quantification and other aspects of analytical merit were presented in the text. The utility of ABL for the analysis of the model drugs in pharmaceutical preparations was demonstrated. The results indicated that the proposed methods are equally accurate and precise as the official or other reported methods.

4-Butyrolactone↗

PubMed2004

A study of vehicles for dosing rodent whole embryo culture with non aqueous soluble compounds.

In rodent whole embryo culture (WEC), finding vehicles for non-aqueous-soluble compounds has been problematic due to developmental toxicity associated with many solvents. The purpose of this study was to identify alternative vehicles for insoluble compounds. In WEC, we evaluated carrier solutions containing bovine serum albumin (BSA) and glycerol as well as the solvents, formamide, dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and ethanol, for relative teratogenicity and delivery of the insoluble teratogen, all-trans retinoic acid (RA). At a concentration of <or=0.04%, formamide and DMF exhibited no significant toxicity to cultured rat embryos and were effective at delivering RA to the embryo. The BSA and glycerol carrier solutions were not teratogenic, although both inhibited robust formation of yolk sac vasculature. Both solutions delivered RA to the cultured rat embryos at higher doses. In summary, all four solvents/solutions may have utility as vehicles dependent upon the chemical properties of the compound to be solubilized.

Animals↗

PubMed2004

Lead as own luminescent sensor for determination.

In our experiments, it was observed that adding bromide to Pb2+ solution of N,N'-dimethylformamide (DMF), the highly emissive cluster Pb4Br11(3-) can be formed and the fluorescence intensity of the formed cluster is proportional to the concentration of Pb2+, based on which, a novel, simple approach that uses the emission from itself as the sensor for determination of Pb2+ is proposed. Under the optimum conditions, the linear range and detection limit is 1.0 x 10(-7) to 1.0 x 10(-5) mol l(-1) (correlation coefficient r = 0.9997) and 7.6 x 10(-9) mol l(-1), respectively. Foreign substrates effects were also investigated. The proposed method has been successfully applied to the determination of lead in the synthetic samples. The mechanism of the reaction is also studied.

Cations, Divalent↗

PubMed2005

Synthesis of the catechols of natural and synthetic estrogens by using 2-iodoxybenzoic acid (IBX) as the oxidizing agent.

A method for the synthesis of 2-hydroxyestrone/estradiol, 4-hydroxyestrone/estradiol, 3'-hydroxydiethylstilbestrol, 3'-hydroxyhexestrol, and 3'-hydroxydienestrol is reported, in which 2-iodoxybenzoic acid (IBX) and the corresponding phenolic estrogen are reacted. Treatment of the natural estrogens, estrone/estradiol, with stoichiometric amounts of IBX in dimethylformamide initially yielded a mixture of estrone/estradiol-2,3- and -3,4-quinones, which were reduced in situ to the corresponding catechols by treatment with a 1 M aqueous solution of ascorbic acid. Chromatographic separation of the reaction products afforded 2- and 4-hydroxyestrone/estradiol in good overall yields (79%). In the case of the synthetic estrogens containing two identical phenolic rings, protection of one ring is a prerequisite for the synthesis of the monocatechol. Thus, diethylstilbestrol and dienestrol were protected at one phenol ring as their methyl ethers. The resulting monophenols were treated with stoichiometric amounts of IBX for 1 h, followed by treatment with 1 M aqueous ascorbic acid to obtain the corresponding catechols in more than 70% yield. Furthermore, the catechol of diethylstilbestrol, protected at one ring, was reduced by catalytic hydrogenation at the C3-C4 double bond to obtain 3'-hydroxyhexestrol in 90% yield. Removal of the protected methoxy groups of the synthetic estrogen catechols was carried out by treatment with a 1 M solution of boron tribromide in dichloromethane. This method is highly efficient for the preparative scale synthesis of catechols of both natural and synthetic estrogens.

Boron↗