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PubMed2004

Determination of primary and secondary standards and characterization of appropriate salt bridges for pH measurements in formamide.

For the first time, the standardization for pH measurements is here implemented in the domain of superpermittive media. The nonaqueous solvent studied is formamide (epsilon = 109.5 at 298.15 K) for which three primary standards and two secondary standards have been determined, whose excellent internal consistency has also been demonstrated by specific cell measurements. A comparison of the pH scale in formamide with the aqueous scale has been duly tried by accounting for the primary medium effect on the H+ ion. Furthermore, as a result of an ad hoc supplementary systematic investigation, three salt bridges of appropriate level of equitransference in formamide, that is, NH(4)Cl, NH(4)Br, and NH(4)I, have been characterized for abating the liquid junction potentials intervening in the pH-measuring cell to enable the user to carry out regular pH measurements and related controls.

Journal Article↗
PubMed2002

Rate acceleration of the Baylis-Hillman reaction in polar solvents (water and formamide). Dominant role of hydrogen bonding, not hydrophobic effects, is implicated.

A substantial acceleration of the Baylis-Hillman reaction between cyclohexenone and benzaldehyde has been observed when the reaction is conducted in water. Several different amine catalysts were tested, and as with reactions conducted in the absence of solvent, 3-hydroxyquinuclidine was found to be the optimum catalyst in terms of rate. The reaction has been extended to other aldehyde electrophiles including pivaldehyde. Attempts to extend this work to acrylates was only partially successful as rapid hydrolysis of methyl and ethyl acrylates occurred under the base-catalyzed and water-promoted conditions. However, tert-butyl acrylates were sufficiently stable to couple with relatively reactive electrophiles. Further studies on the use of polar solvents revealed that formamide also provided significant acceleration and the use of 5 equiv of formamide (optimum amount) gave faster rates than reactions conducted in water. Using formamide, further acceleration was achieved in the presence of Yb(OTf)(3) (5 mol %). The scope of the new conditions was tested with a range of Michael acceptors and benzaldehyde and with a range of electrophiles and ethyl acrylate. The origin of the rate acceleration is discussed.

Journal Article↗
PubMed1988

Effect of peroxidase inhibitors on an in vivo metabolite of the urinary bladder carcinogen N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide in rats.

Peroxidase metabolism of 2-amino-4-(5-nitro-2-furyl)thiazole (ANFT) was evaluated in vitro and in vivo. In vitro metabolism of ANFT was characteristic of the hydroperoxidase activity of prostaglandin H synthase. The peroxidase inhibitors, 6-n-propyl-2-thiouracil and methimazole, significantly reduced ANFT binding to trichloroacetic acid precipitable material and glutathione conjugate formation. Isolated perfused kidneys rapidly converted the glutathione conjugate to its corresponding mercapturic acid (ANFT-MA). With both radiochemical and electrochemical techniques, ANFT-MA was identified in the urine of rats given N-[14C]-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide, the carcinogenic N-formyl analogue of ANFT. ANFT was the major urinary metabolite with N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide not detected. A 30-min pretreatment with 6-n-propyl-2-thiouracil and methimazole significantly reduced urinary excretion of ANFT-MA in rats given N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (150 mg/kg) from 14.8 +/- 2.1 (SE) to 7.9 +/- 0.8 and 6.2 +/- 1.1 nmol/18 h, respectively. Peroxidase inhibitor pretreatment did not alter the excretion of ANFT or prostaglandin E2. These results provide further in vitro and in vivo support for the involvement of peroxidases, i.e., the hydroperoxidase activity of prostaglandin H synthase, in ANFT metabolism.

Acetylcysteine↗
PubMed1984

Biotransformation of the bladder carcinogen N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide in mice.

The biotransformation of N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (FANFT), a potent urinary bladder carcinogen, was studied in mice. About 82% of radioactivity was excreted as 14CO2 within 36 hr after intragastric administration of N-[4-(5-nitro-2-furyl)-2-thiazolyl]-[14C]formamide, suggesting its deformylation to 2-amino-4-(5-nitro-2-furyl)thiazole ( ANFT ). The latter was formed in vitro as a product following incubation of FANFT with mouse liver homogenates. Chromatographic analysis of mouse urine obtained 24 hr after the i.p. administration of N-[4-(5-nitro-2-furyl)-[2-14C]thiazolyl]formamide revealed excretion of ANFT and unmetabolized FANFT, suggesting the prevalence of the deformylation reaction in vivo. In addition, at least two more metabolites were present in urine. One of these metabolites exhibited chromatographic properties similar to those exhibited by a compound derived from the in vitro nitroreduction of ANFT . This metabolite was isolated from urine of FANFT-fed animals and from in vitro enzymatic reduction of ANFT with mouse liver homogenates. The isolated products had chromatographic and spectral properties and a mass spectral fragmentation pattern similar to that of a compound obtained by catalytic reduction of ANFT with palladium and activated carbon. Spectroscopic analyses established the structural identity of the chemical reduction product as 1-[4-(2-aminothiazolyl)]-3-cyano-1-propanone ( ATCP ). Since the chromatographic properties of the enzymatically derived product and the urinary metabolite were identical to those of a compound obtained by chemical reduction, they must be structurally the same and thus correspond to ATCP . About 5% of the urinary metabolites of FANFT is ATCP , and thus ATCP is quantitatively a minor excretory product. ATCP was far less active than was ANFT of FANFT in the Ames mutagenicity assay with Salmonella typhimurium TA.

Animals↗
PubMed2003

One-pot TiO2-catalyzed synthesis of nucleic bases and acyclonucleosides from formamide: implications for the origin of life.

A novel one-pot TiO2-catalyzed synthesis of nucleobases and acyclonucleosides from formamide is reported. Since formamide can be formed under prebiotic conditions, these reactions have implications for the origin of life. While a number of purine derivatives have been found as products of non-TiO2-catalyzed reactions, important compounds that would not otherwise occur (namely, thymine, 5-hydroxymethyluracil, and acyclonucleosides) are formed in acceptable yields by TiO2-catalyzed reactions. Moreover, TiO2 selectively affects the rates of degradation of nucleobases, as single units and when embedded in polynucleotides.

Base Sequence↗
PubMed2005

Synthesis and degradation of nucleic Acid components by formamide and cosmic dust analogues.

We show the unprecedented one-pot synthesis of a large suite of pyrimidines (including cytosine and uracil) and purines from formamide in the presence of cosmic-dust analogues (CDAs) of olivines. Since the major problem in the origin of informational macromolecules is the instability of their precursors, we also investigate the stabilizing effect of CDAs on the intrinsic instability of oligonucleotides in formamide.

Catalysis↗
PubMed1983

Ion-exchange high-performance liquid chromatography of oligodeoxyribonucleotides using formamide.

The superiority of buffer systems containing formamide for the ion-exchange high-performance liquid chromatographic separation of oligodeoxyribonucleotide mixtures generated in solid-phase syntheses is illustrated. The resolutions achieved are compared to those achieved with the same mixtures in other eluting solvents. The use of formamide systems is recommended for oligodeoxyribonucleotide purification in general and is particularly valuable where the oligonucleotide of interest is highly self-complementary and/or rich in deoxyguanosine residues.

Chromatography, High Pressure Liquid↗
PubMed1984

Use of S1 nuclease and formamide in combination for the reassociation studies on GC-rich DNA.

The optimal parameters in the use of nuclease S1 in DNA reassociation kinetics in the presence of formamide have been determined. The conditions are especially suitable for the study of DNA rich in mole percent GC. A 10-fold dilution of the reassociation samples leading to a decrease in both NaCl and formamide concentrations, consequently resulting in a lowering of Tm by only 1.5 degree C, and the S1 digestion at temperatures identical to the reassociation assay in order to retain the stability of the duplex, are two important aspects of this system. Under these conditions, the kinetics of reassociation followed the theoretically predicted pattern, while the earlier reported methods have shown lower values.

Chemical Phenomena↗
PubMed1985

Differentiation of apurinic/apyrimidinic sites and single-strand breaks in DNA by formamide- and alkaline-sucrose gradient sedimentation.

The excision repair of DNA damaged by physical or chemical agents may produce either apurinic/apyrimidinic (AP) sites or single-strand breaks (SSB) in the DNA. Alkaline-sucrose gradient sedimentation and alkaline elution, techniques generally used for the study of DNA repair which depend upon high pH to denature the DNA, cannot differentiate between these possibilities. A simple method for the quantitative measurement of SSB in DNA which leaves any AP sites intact is presented. This method relies upon the separation by size of the fragments resulting from the denaturation of the DNA under neutral conditions by sedimentation through gradients of sucrose in formamide. By combining the use of both formamide- and alkaline-sucrose sedimentation methods, we can quantify both AP sites and SSB in DNA.

Apurinic Acid↗
PubMed1977

Solvent denaturation of globular proteins: unfolding by the monoalkyl- and dialkyl-substituted formamides and ureas.

The effects of the monoalkyl and dialkyl-substituted formamide series of denaturants on the native conformation of sperm whale myoglobin, horse heart cytochrome c, and Glycera dibranciata (single chain) hemoglobin have been investigated by spectral measurements in the Soret region (409 and 422 nm) and optical rotation measurements (265nm). The effectiveness of these two classes of protein denaturants is similar to the other straight-chain compounds of the urea, amide, and alcohol classes, examined in previous investigations from our laboratory. Their denaturing effectiveness is found to increase with increasing chain length or hydrocarbon content of the substituent alkyl groups. Application of the Peller and Flory equation to the denaturation data of the formamides shows that both the polar and the nonpolar group contributions to the protein-denaturant interactions have to be taken into account in order to correctly predict the observed denaturation midpoints. Additivity of the hydrophobic, KHø, and the polar, Kp, group contributions to the binding constants, KB = nKHø + Kp, with n = 1 or 2 for the mono- of the di-alkyl substituted denaturants gave best account of the experimental data. The KHø values used were based on free energy transfer data of various alkyl groups or the Scheraga-Nemethy theory of hydrophobic bonding. The assumption of group contributions of the denaturant to KB were also applied to the denaturation data of the unsubstituted amides and some examples of the monoalkyl and symmetrically substituted dialkyl ureas, taken from the literature.

Cytochrome c Group↗
PubMed1987

Deionization of formamide with Biorad AG501-X(D).

We have studied different conditions of the deionization of formamide with Biorad mixed bed resin AG501-X(D) and find that contrary to the popular usage, drying the resin before deionization produces the best results. In a typical deionization procedure, conductivity initially goes down, reaches a minimum plateau and finally goes up again. The initial rate of deionization, the minimum conductivity reached at the plateau and the rate of final rise in conductivity depend on whether the resin is dry or wet (i.e., straight from the bottle) and on the amount of resin used. In general, wet resin produced faster initial deionization, higher minimum conductivity and quicker final rise in conductivity. Surprisingly, a smaller amount (5%) of resin worked better than a larger amount (20%). With smaller amount of resin, although initial deionization was slower, the minimum conductivity achieved was lower and the final rise in conductivity was slower. This was partly due to the fact that the conductivity of formamide increases faster with increasing amount of water in it.

Chromatography, Ion Exchange↗
PubMed1988

Open channel noise. IV. Estimation of rapid kinetics of formamide block in gramicidin A channels.

Blocking events in currents through biological ion channels occur over a wide range of characteristic times. The interruptions in single-channel currents from blocking events may be characterized by the direct measurement of gap durations or by analyzing open-channel current histograms, provided that the events are not much shorter than the time resolution of single-channel recordings (approximately 10 microseconds). Here we present a method for the characterization of channel block on a much faster time scale by combining open-channel noise measurements with subsequent model fits according to a theoretical approach (Frehland, E. 1978. Biophysical Chemistry. 8:255-265). Although the bandwidth limitations in open-channel noise experiments are the same as in conventional single-channel experiments, from the dependence of the mean current and the spectral density of the noise on the concentration of the blocking agent, kinetics of very brief blocking events can be estimated. As an example we have analyzed the open-channel noise of K+ currents through the gramicidin A channel in the presence of various concentrations of formamide, a weak blocker, at neutral pH. We estimate the blocking and unblocking rates to be approximately 10(7)s-1 at 1 M formamide and discuss possible mechanisms for the blocking process.

Electric Conductivity↗
PubMed2002

Potential of formamide and N-methylformamide in nonaqueous capillary electrophoresis coupled to electrospray ionization mass spectrometry. Application to the analysis of beta-blockers.

A nonaqueous capillary electrophoresis (NACE) method, coupled with either UV or electrospray mass spectrometry (ESI-MS), is described for the simultaneous analysis of seven beta-blockers. The same electrolyte, namely 25 mM ammonium formate and 1 M formic acid, was used with different investigated organic solvents. In addition to frequently used organic solvents such as methanol (MeOH) and acetonitrile (MeCN), formamide and its derivatives were investigated. Formamide (FA) and N-methylformamide (NMF) present several interesting physico-chemical properties, one of them being a high dielectric constant (e). Since FA and NMF possess a high UV cutoff, beta-blockers with an absorbance above 250 nm were selected as model compounds in order to compare NACE-UV and NACE-MS performances. FA and NMF showed different selectivity compared to water, MeOH or MeCN, and also demonstrated a higher efficiency in terms of the number of theoretical plates (especially NMF). To overcome their unfavorable optical properties, hyphenation with MS detection appears as a promising technique, thanks to its benefits in terms of selectivity, sensitivity and universality. The practical compatibility of FA and NMF with ESI-MS detection in combination with a sheath liquid configuration was demonstrated. In comparison to UV detection, sensitivity was increased, while a high efficiency was maintained. In addition, the low and stable generated currents observed were evidences for the successful hyphenation with ESI-MS. Hence, FA and NMF seemed to be promising alternatives in NACE-ESI-MS, either used as pure organic solvent or as a mixture with MeOH or MeCN.

Adrenergic beta-Antagonists↗
PubMed2001

A possible prebiotic synthesis of purine, adenine, cytosine, and 4(3H)-pyrimidinone from formamide: implications for the origin of life.

The synthesis of prebiotic molecules is a major problem in chemical evolution as well as in any origin-of-life theory. We report here a plausible new prebiotic synthesis of naturally occurring purine and pyrimidine derivatives from formamide under catalytic conditions. In the presence of CaCO(3) and different inorganic oxides, namely silica, alumine, kaolin, and zeolite (Y type), neat formamide undergoes the formation of purine, adenine, cytosine, and 4(3H)-pyrimidinone, from acceptable to good yields. The role of catalysts showed to be not limited to the improvement of the yield but it is also relevant in providing a high selectivity in the products distribution.

Catalysis↗
PubMed2000

IR study of dickite-formamide intercalate, Al2Si2O5(OH)4-H2NCOH.

Direct intercalation of formamide (FAM) in dickite occurs spontaneously when samples are treated by ultrason. The X-ray diffraction patterns show that this intercalation increases the d001 spacing from 7.19 to 10.77 A. It is concluded from infrared studies that hydrogen bonds are formed between C=O groups of formamide and inner surface hydroxyls of dickite, indicated by the shift of the hydroxyl bands from 3708, 3654 cm(-1) and 3622 for natural dickite to 3575, 3520, 3450 and 3612 cm(-1) for FAM-intercalated dickite.

Aluminum Silicates↗
PubMed1997

Binding of formamides to liver alcohol dehydrogenase.

Amides are analogs of aldehydes and potent inhibitors of liver alcohol dehydrogenases. They can be used for structural studies and for inhibiting the metabolism of alcohols that form toxic products. We studied N-alkyl amides that bind to the enzyme-NADH complex and act as uncompetitive inhibitors against varied concentrations of ethanol (millimolar Kii values, at pH 8 and 25 degrees C): N-propylacetamide (16), delta-valerolactam (1.6), N-formylpiperidine (0.14), N-isobutylformamide (0.028), N-(cyclohexylmethyl)-formamide (0.011), and N-cyclohexylformamide (0.0087). The lower affinity of delta-valerolactam and N-propylacetamide can be explained by steric hindrance with Phe93 of the enzyme. Replacing Phe93 with Ala in the S48T/F93A mutated enzyme, which resembles the natural alpha-isoenzyme of primates, improved binding of delta-valerolactam by 210-fold. The structures of horse liver enzyme complexed with NADH and N-cyclohexylformamide or N-formylpiperidine were determined by X-ray crystallography at 2.5 A resolution. In both complexes, the carbonyl oxygens of the inhibitors bind to the catalytic zinc and form a hydrogen bond to the hydroxyl group of Ser48 of the enzyme. The six-membered rings bind in overlapping, but rotated, positions that optimize hydrophobic interactions. The binding modes of the unreactive formamides appear to resemble the Michaelis complexes of the analogous substrates, with the re face of the carbonyl carbon suitably positioned to accept a hydrogen from NADH.

Alcohol Dehydrogenase↗
PubMed2002

The cold origin of life: A. Implications based on the hydrolytic stabilities of hydrogen cyanide and formamide.

It has been suggested that hydrogen cyanide (HCN) would not have been present in sufficient concentration to polymerize in the primitive ocean to produce nucleic acid bases and amino acids. We have measured the hydrolysis rates of HCN and formamide over the range of 30-150 degrees C and pH 0-14, and estimated the steady state concentrations in the primitive ocean. At 100 degrees C and pH 8, the steady state concentration of HCN and formamide were calculated to be 7 x 10(-13) M and 1 x 10(-15) M, respectively. Thus, it seems unlikely that HCN could have polymerized in a warm primitive ocean. It is suggested that eutectic freezing might have been required to have concentrated HCN sufficiantly for it to polymerize. If the HCN polymerization was important for the origin of life, some regions of the primitive earth might have been frozen.

Cold Temperature↗
PubMed1978

Fractionation of water-insoluble protein using sephacryl S-200 in formamide.

The ability of Sephacryl S-200 to fractionate water-insoluble protein by gel permeation chromatography was investigated. Elution of protein standards from colums of Sephacryl S-200 equilibrated with formamide, an excellent solvent for both hydrophobic and hydrophilic proteins, was molecular weight dependent. Advantages of chromatography of water-insoluble proteins using Sephacryl S-200 include rapidity, recovery of protein free of detergent or solvent, safety, ability to purify large amounts of protein, and ability to separate proteins as large as 100,000 daltons. Separation of water-insoluble polypeptides in a crude preparation of gliadin in formamide demonstrated the practicality of the method.

Chromatography, Gel↗