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PubMed1986

Solubilization of the iron molybdenum cofactor of Azotobacter vinelandii nitrogenase in dimethylformamide and acetonitrile.

The iron molybdenum cofactor of Azotobacter vinelandii nitrogenase has been solubilized for the first time in dimethylformamide and acetonitrile. These solutions have the ability to reconstitute the inactive nitrogenase of the UW 45 mutant of A. vinelandii and exhibit an S = 3/2 EPR signal similar to that for the cofactor in N-methylformamide. Our ability to obtain solutions of FeMoco in these solvents seemingly refutes a previous hypothesis concerning the necessity of solvents with a dissociable proton for iron molybdenum cofactor solubility and should facilitate the spectroscopic characterization of this important species.

Acetonitriles↗
PubMed1961

Spectroscopic evidence for complexing of acetic acid with bovine serum albumin, gramicidin, and dimethylformamide.

Acetic acid has a major effect on the absorption spectra of bovine serum albumin, gramicidin, and dimethylformamide in the region, 255 to 200 mmu. Increasing the concentration of acetic acid causes progressively decreasing absorbency accompanied by a large and progressively increasing red shift of the absorption maximum. The decrease in absorbency is interpreted in terms of a reversible complexing of acetic acid with these molecules and the red shift in terms of a non-specific solvent effect.

Acetates↗
PubMed1989

Derivatization of N-methyl and cyclic amino acids with dimethylformamide dimethyl acetal.

Six amino acids containing either an N-methyl or a cyclic secondary amine were converted to volatile derivatives by reaction with dimethylformamide dimethyl acetal. The amine functionalities were formylated by way of an amide acetal intermediate while the carboxylic acid groups were esterified directly. The resulting N-formyl esters were stable to solvent extraction and exhibited gas chromatography-mass spectrometry properties suitable for assay development.

Amino Acids↗
PubMed1999

High-performance liquid chromatographic determination of n-methylformamide, a biological index for occupational exposure to dimethylformamide.

This report describes an analytical method for the biological monitoring of workers exposed to N,N-dimethylformamide (DMF), a solvent widely used in the chemical industry. The human main metabolites of DMF are N-hydroxymethyl-N-methylformamide (HMMF) and the minor metabolites N-methylformamide (NMF) and N-acetyl-S-(N-methylcarbamoyl)cysteine. The metabolite selected by the American Conference of Governmental Hygienists for occupational biomonitoring purposes, is NMF measured by gas chromatographic analysis, as during it HMMF may be converted to the minor metabolite NMF. HMMF and NFM can be measured independently using HPLC analysis. The procedure proposed here involves the thermal transformation of the primary metabolite HMMF into the minor metabolite NMF, which is then determined by HPLC. This method makes it possible to determine, using HPLC, both metabolites of DMF by measuring only one peak, thus offering two major advantages: (i) it increases the sensitivity of the test and (ii) it deploys only one reference standard.

Calibration↗
PubMed2001

Inactivation of rat liver cytochrome P450 (P450) by N,N-dimethylformamide and N,N-dimethylacetamide.

N,N-dimethylformamide (DMF), an organic solvent widely used in industry, is bioactivated by cytochrome P450 (P450) to reactive metabolites which are believed to be responsible for the hepatotoxicity observed in animals and humans. A decrease of the activating enzyme has been reported in rats treated with DMF, although the specific P450 isoform(s) involved and the nature of the reactive species responsible for this and the other toxic effects are still being investigated. In the present work, the effect of DMF and of the structurally related N,N-dimethylacetamide (DMAc) on the activating enzyme and the nature of the reactive species involved in the mechanism of P450 inactivation by the two chemicals were investigated in vitro. Incubation of liver microsomes from pyridine-induced rats with either substrate resulted in a dose-dependent (0-20 mM) loss of P450 (up to 28 and 24% for DMF and DMAc, respectively), microsomal haem (up to 24 and 20% for DMF and DMAc, respectively), but not protoporphyrin IX content. Moreover, bubbling of CO through the incubation mixture gave almost complete protection against substrate-dependent P450 inactivation, and the spin trapping agent N-tert-butyl-alpha-phenylnitrone, but neither glutathione nor vitamin C, provided a significant protection against DMF- or DMAc-dependent haem loss. Finally, electron spin resonance analysis of microsomal incubations in presence of DMF or DMAc showed spectral evidence for a carbon centered radical intermediate. The results indicate, overall, that both compounds are metabolized in vitro by P450, probably CYP2E1, to free radical metabolites which attack the haem prosthetic group, leading to suicidal enzyme inactivation.

Acetamides↗
PubMed1978

Gas--liquid chromatographic determination of carbamazepine and phenylethylmalonamide in plasma after reaction with dimethylformamide dimethylacetal.

A previously published procedure for the gas chromatographic analysis of carbamazepine has been modified and expanded to allow simultaneous determination of phenylethylmalonamide, a metabolite of primidone. Internal standards that closely resemble each compound are used, and derivatives are made by reaction with dimethylformamide dimethylacetal. This change of internal standard for carbamazepine and the use of a commercial, pretested column-packing material eliminate the major pitfalls of the original method.

Carbamazepine↗
PubMed1988

Gas chromatographic method for the determination of N-acetyl-S-(N-methylcarbamoyl)cysteine, a metabolite of N,N-dimethylformamide and N-methylformamide, in human urine.

A simple method has been developed for the determination of N-acetyl-S-(N-methylcarbamoyl)cysteine in human urine. Treatment of a urine sample (1 ml) with ethanol (2 ml) and potassium carbonate (1.5 g) produces ethyl N-methylcarbamate, which is extracted into ethanol and measured by packed column gas chromatography with nitrogen-sensitive detection. The limit of quantitation in human urine is 1 microgram/ml and the between-sample coefficient of variation is 5-11%. Simultaneously, N,N-dimethylformamide, N-methylformamide and formamide can also be determined.

Acetylcysteine↗
PubMed2002

Improved gas chromatographic-mass spectrometric determination of the N-methylcarbamoyl adduct at the N-terminal valine of globin, a metabolic product of the solvent N,N-dimethylformamide.

A sensitive method for determination of the N-methylcarbamoyl adduct at the N-terminal valine of globin, a new metabolic product of the industrial solvent N,N-dimethylformamide (DMF), has been developed and validated. The method includes conversion of the adduct by the Edman degradation to 3-methyl-5-isopropylhydantoin (MVH), which is followed by optimized gas chromatographic analysis with mass spectrometric detection at m/z 114. The recovery of MVH from terminal N-methylcarbamoylvaline was determined using a model dipeptide to be 90%. Calibration of the method is done with MVH, employing 3-methyl-5-isobutylhydantoin as the internal standard. The limit of detection is 0.2 nmol MVH/g globin when a 100-mg sample is used. Within- and between-day precision is 4-10%. The method has been used to determine the background levels of MVH in unexposed subjects. Further, toxicokinetic studies in volunteers laid the grounds for setting the reference value for biological monitoring of occupational exposure to DMF.

Calibration↗
PubMed1998

Salt-steered partitioning of proteins in polymeric two-phase systems based on N,N-dimethylformamide.

The polymeric two-phase (liquid liquid) system, based on N,N-dimethylformamide (DMFA) and the two polymers Ficoll and poly(ethylene glycol). has been investigated. The partitioning of the water-insoluble protein fraction, zein (from corn), was affected by the addition of various salts that were soluble in DMFA. The effect of the salts has been correlated to their partition coefficients. The data have been fitted to a theory for partitioning of polyelectrolytes in aqueous two-phase systems. The two-phase system has been used for partial fractionation of zein by counter-current distribution.

Chemistry Techniques, Analytical↗
PubMed1999

Simultaneous determination of two human urinary metabolites of N,N-dimethylformamide using gas chromatography-thermionic sensitive detection with mass spectrometric confirmation.

Two human urinary metabolites of the industrial solvent N,N-dimethylformamide (DMF), N-hydroxymethyl-N-methylformamide (HMMF) and N-acetyl-S-(N-methylcarbamoyl)cysteine (AMCC), were assayed using a new analytical method (gas chromatography and thermionic sensitive detection). Clean-up of urine samples includes a liquid-liquid extraction step followed by a solid-phase extraction step to separate HMMF and AMCC from other urine components. During clean-up, AMCC is converted into ethyl-N-methylcarbamate (EMC), and during gas chromatography, HMMF is degraded in the injector to N-methylformamide (NMF). All the validation data necessary for a quantitative procedure are given. The method was applied to urine samples from workers exposed to DMF and from the general population. The results were confirmed by mass spectrometric determination. For this purpose a further liquid-liquid extraction step was introduced in the clean-up procedure. Background levels of AMCC in the general population were identified.

Acetylcysteine↗
PubMed1997

Investigation of the feasibility of directly-coupled HPLC-NMR with 2H detection with application to the metabolism of N-dimethylformamide-d7.

The use of 2H NMR spectroscopy as a detector for HPLC has been investigated using the continuous flow method in which rat urine containing metabolites of N-dimethylformamide-d7 was employed as a test case. Three xenobiotic-related species, including DMF-d7 itself, were detected. It is shown that for small molecules which give relatively sharp 2H NMR resonances, 2H HPLC-NMR spectroscopy is a feasible technique. For larger molecules, the resulting broad lines are likely to preclude the determination of detailed structural information. However, extension of the approach is possible by the use of selectively 2H-labelled xenobiotics to determine HPLC retention times of metabolites with continuous-flow 2H NMR spectroscopy detection, followed by stop-flow 1H HPLC-NMR spectroscopy for structural characterisation.

Animals↗
PubMedDate not supplied

Formamide and dimethylformamide: reproductive assessment by continuous breeding in mice.

Reproductive toxicity in Swiss mice, during chronic exposure to formamide (FORM) or dimethylformamide (DMF), was evaluated using the Reproductive Assessment by Continuous Breeding Protocols. FORM administered in drinking water at 0, 100, 350, and 750 ppm (approximately 20 to 200 mg/kg/d) reduced fertility and litter size in F0 animals without generalized toxicity at 750 ppm FORM. Crossover matings suggested that females were the affected sex. After F1 mating, FORM reduced F2 litter size, increased days to litter, reduced relative ovarian weight, and lengthened estrous cycles at 750 ppm. The No-Observed-Adverse-Effect-Level for generalized toxicity was 750 ppm for the F0 and 350 ppm for the F1 generation. Reproductive performance was normal at 350 ppm for both F0 and F1 mice. Chronic exposure to DMF in drinking water at 0, 1000, 4000, and 7000 ppm (approximately 200 to 1300 mg/kg/d) reduced fertility by the first litter at 4000 ppm, reduced body weight in F0 females at 7000 ppm, and increased liver weights at all doses in both sexes. A crossover mating at 7000 ppm identified F0 females as the affected sex. F1 postnatal survival was reduced at > or =4000 ppm DMF. F1 mating reduced F2 litter size and live pup weight at > or =1000 ppm. At necropsy, body weight of F1 males and females was reduced at > or =4000 ppm. DMF-treated pups (both F1 and F2) and F1 adults had cranial and sternebral skeletal malformations. Only DMF caused overt developmental toxicity. A No-Observed-Adverse-Effect-Level for DMF was not established.

Animals↗
PubMed2000

Vibrational spectroscopic studies on ion solvation of lithium perchlorate in propylene carbonate + N,N-dimethylformamide mixtures.

The infrared (IR) and Raman spectra are reported for solutions of lithium perchlorate in propylene carbonate (PC), N,N-dimethylformamide (DMF) and PC + DMF mixtures. The band splittings of symmetric ring deformation for PC and O=CN deformation for DMF suggest that there is a strong interaction between lithium cations and solvent molecules. The solvent molecules have been assigned to two types, the free and complexed molecules. By a comparison of the intensity for the corresponding bands, it has been concluded that Li+ cations are preferentially solvated by DMF molecules in the LiClO4/PC-DMF solutions. This has been explained by the difference in values of donor number.

Carbonates↗
PubMed1982

Kinetics and equilibria of active site core extrusion from spinach ferredoxin in aqueous N,N-dimethylformamide/Triton X-100 solutions.

The nature and reactivity of each species participating in core extrusion of the [2Fe-2S] cluster of spinach ferredoxin by benzenethiol have been investigated in a novel aqueous medium containing 10-40% (v/v) N,N-dimethylformamide (DMF) plus 5-6% (v/v) of the nonionic detergent, Triton X-100. By use of visible absorption and circular dichroism spectroscopies, it is found that prior to addition of benzenethiol, modifications of the ferredoxin induced by DMF are reversible. Both the extent and rate of modification are dependent on DMF concentration and on ionic strength. At ferredoxin concentrations near 0.1 mM, complete modification by DMF is shown to be unnecessary for quantitative core extrusion provided that the benzenethiol concentration is greater than or equal to 50 mM and the DMF concentration is greater than or equal to 10% (v/v). When benzenethiol is added after DMF, core extrusion occurs in two phases. Our interpretation is that the rapid phase corresponds to core extrusion of that portion of the ferredoxin already modified by DMF and that the slower phase corresponds to modification of the remaining portion of the ferredoxin by DMF. When DMF solutions containing benzenethiol and Triton X-100 in various ratios are mixed with aqueous solutions of spinach ferredoxin, the rate of core extrusion appears to be determined both by the rate at which the ferredoxin is modified and by the Triton/benzenethiol ratio. Under all conditions examined we observe significantly faster rates of core extrusion from spinach ferredoxin in aqueous Triton/DMF than in 80/20 (v/v) hexamethylphosphoramide/water, a previously used core extrusion medium. Our results suggest a catalytic role for the micellar phase.

Binding Sites↗
PubMed2005

Rheological studies utilizing various lots of zein in N,N-dimethylformamide solutions.

Rheological studies were carried out on solutions of zein in N,N-dimethylformamide (DMF), where the specific lot of zein, concentration, time, and temperature were varied. DMF is a good solvent for zein, giving clear, relatively low viscosity solutions. It was found that all of the zein solutions behaved in a non-Newtonian fashion. At high concentration and elevated temperature, zein solutions will increase in viscosity with time. A temperature study on the rate of viscosity rise illustrated that at temperatures above 40 degrees C, the rate of viscosity rise increased in a non-Arrhenius fashion. There can be significant lot to lot variations in commercially obtained zein that gives rise to differences in viscosity and rate of viscosity rises. With the samples studied, viscosity was found to double from one lot of zein to another. Size exclusion chromatography suggests that compositional differences between the lots drive the observed differences in viscosity.

Dimethylformamide↗
PubMed2005

Experimental and theoretical study of the surface-controlled dissolution of cylindrical particles. Application to solubilization of potassium hydrogen carbonate in hot dimethylformamide.

In this paper we present a mathematical model for the surface-controlled dissolution of cylindrical solid particles. This is employed to interpret experimental data published previously for the dissolution of potassium bicarbonate in dimethylformamide at elevated temperatures. Significant kinetic differences in assuming cylindrical rather than spherical shapes are reported with the former representing a closer approximation to the true shape of the particles as revealed by scanning electron microscopy. From the fits of experimental data to the cylindrical model for the surface-controlled dissolution, the dissolution rate constant, k, for the dissolution of KHCO(3) in DMF was found to be (9.6 +/- 1.6) x 10(-9) mol cm(-2) s(-1) at 100 degrees C, and the activation energy for the dissolution was 34.5 kJ mol(-1) over the temperature range of 60-100 degrees C. Comparison between cylindrical and spherical dissolution theory highlights the importance of considering the particle shapes for realistic modeling of surface-controlled dissolution kinetics.

Bicarbonates↗
PubMed2001

N-methylcarbamoylated valine of hemoglobin in humans after exposure to N,N-dimethylformamide: evidence for the formation of methyl isocyanate?

N,N-Dimethylformamide (DMF) is reported to cause testicular germ-cell tumors in exposed workers. The reports, however, are not in line with results obtained in animal and in vitro experiments, where DMF was shown not to be mutagenic and also not to be carcinogenic. Considerable interest raised on the formation of a reactive intermediate, presumably methyl isocyanate (MIC), during metabolism of DMF in humans over the last years. We report the formation of N-methylcarbamoylated valine of hemoglobin (Hb) in blood samples from workers exposed to DMF in the polyacrylic fiber industry. N-Methylcarbamoylated Hb was formed by the reaction of MIC with Hb. For this purpose, Hb adducts were monitored by means of a modified Edman degradation involving the release of the N-terminal valine adduct in form of 3-methyl-5-isopropylhydantoin (MIH). For internal standardization of the method, 3-ethyl-5-isopropylhydantoin (EIH) was used. Separation and analysis of MIH and EIH were carried out by gas chromatography and mass spectrometry with electron impact ionization (GC/EI-MS). Hb adducts in form of MIH were quantified in blood samples from exposed persons in concentrations between 26.1 and 412.0 nmol of MIH/g of globin. The observed adducts were proven to be identical to those derived from the in situ reaction between Hb and MIC. Taken together with the fact that only N-methylcarbamoylated Hb can undergo ring closure to the corresponding hydantoin, the reaction is indirect evidence for the occurrence of MIC in vivo. The formation of MIC directly in the cell and its possible distribution through the human body may lead to critical effects after exposure to DMF. Adducts were determined not to be totally specific for exposure to DMF since an identical adduct was also found in blood samples from the general population. However, concentrations were lower by a factor of about 100. The sources for background adducts are currently unknown.

Antisickling Agents↗
PubMed2000

DNA damage by dimethylformamide: role of hydrogen peroxide generated during degradation.

Dimethylformamide (DMF) has been suspected to associate with cancers in exposed workers, whereas there has been inadequate evidence for carcinogenicity in experimental animals. We demonstrated that H(2)O(2) was generated during the degradation of DMF under aerobic conditions, and that the amount of H(2)O(2) was enhanced by exposure to solar light or by the contamination of trace metal. Experiments using (32)P-5'-end-labeled DNA fragments revealed that the degraded DMF induced DNA damage in the presence of Cu(II). However, purified DMF did not induce DNA damage even in the presence of Cu(II). Addition of purified DMF enhanced DNA damage induced by H(2)O(2) in the presence of Cu(II). The degraded DMF caused Cu(II)-mediated DNA cleavage frequently at thymine and cytosine residues. The similar pattern of site-specific DNA damage was observed with purified DMF and H(2)O(2). Bathocuproine and catalase inhibited the DNA damage, indicating the involvement of Cu(I) and H(2)O(2). A typical free hydroxy radical scavenger showed no inhibitory effect on the DNA damage. Addition of purified DMF enhanced about 3-4-fold 8-oxo-7, 8-dihydro-2'-deoxyguanosine formation induced by H(2)O(2) and Cu(II). ESR spectroscopic study demonstrated that carbon-centered radicals and nitrogen-centered radicals were generated in the reaction mixture of DMF, H(2)O(2), and Cu(II). Inhibitory effects of scavengers on radical formation and DNA damage suggest that carbon-centered radicals and/or nitrogen-centered radicals may contribute to the DNA damage. These results suggest that H(2)O(2) generation during DMF degradation is related to the possible carcinogenic activity of DMF.

Copper↗