Showing papers on "Thiocyanate published in 1982"

Structural considerations in the metabolism of nitriles to cyanide in vivo.

Abstract: In order to investigate structure-activity relationships that influence metabolism of nitriles to CN-, thiocyanate was measured, as an index of CN- release, in urine of rats given equimolar doses of nitriles. Significantly more SCN- was excreted after po than after ip administration of saturated (C2-C5) nitriles, but SCN- excretion was the same after both routes for n-hexanenitrile. Among saturated nitriles, SCN- excretion was maximal for the C3 and C4 compounds, propionitrile, n-butyronitrile, and isobutyronitrile, after both po and ip administration. SCN- excretion was not elevated after administration of the tertiary nitrile trimethylacetonitrile. Administration (po) of the unsaturated nitriles acrylonitrile, crotonitrile, and 3-butenenitrile yielded 37%, 5.6%, and 29% of the dose as SCN-, whereas after ip injection 4.5%, 4.6%, and 18% of the doses were excreted as SCN-, respectively. After iv injection of acrylonitrile, urinary SCN- content was not elevated, whereas 45% of an iv dose of the saturated analog propionitrile was excreted as SCN-. These results suggest that length of the carbon chain, presence of substituents at the alpha-carbon, position of double bonds, and, for some compounds, route of administration, are important factors influencing the release of CN- from nitriles.

Lactoperoxidase-catalyzed oxidation of thiocyanate: polarographic study of the oxidation products.

Abstract: The lactoperoxidase-catalyzed oxidation of thiocyanate (SCN-) was studied by two different polarographic techniques: direct current polarography and linear sweep voltammetry. The main oxidation product at pH 6.5, with a half-wave potential (E1/2) of -0.39 to -0.44 V, was identified as hypothiocyanite (OSCN-) ion. The E1/2 for OSCN- was not available in the literature. The identification of OSCN- was based on a close correlation between the current of the OSCN- peak and the concentration of chemically assayed OSCN-. Also the specific rates of decay of the current and that of chemically detectable OSCN- were similar, and both curves followed apparent first-order kinetics. Subsequently, the addition of a reducing agent (2-mercaptoethanol) resulted in immediate disappearance of both chemically detectable OSCN- and the OSCN- wave in the polarograms. All three components of the lactoperoxidase (LPO) system (SCN-, H2O2, and LPO) were needed to produce the OSCN- peak. Addition of excess H2O2 or H2O2-LPO to an OSCN--SCN- mixture resulted in a formation of a new peak with a characteristic peak potential (Ep) of -0.20 to -0.25 V. The generation of this new peak was associated with a simultaneous, markedly enhanced decrease of OSCN- concentration, indicating a possible reaction between H2O2 (or H2O2-LPO) and OSCN-. No equivalent reaction was obtained by the addition of buffer alone. This new peak may represent higher oxy acids of SCN- (O2SCN-, O3SCN-), formed in the oxidation of OSCN- by H2O2 or by H2O2-LPO. This type of reaction can explain why, in solutions which already contain OSCN- (e.g., in saliva), the addition of H2O2 results in the formation of highly reactive, short-lived antimicrobial products in addition to OSCN-.

Extraction of Am(III) and Eu(III) from aqueous ammonium thiocyanate by dihexyl-N,N-diethylcarbamolymethylphosphonate and related compounds

Abstract: The extraction behavior and separation factors of Am(III) and Eu(III) from low acid ammonium thiocyanate solutions were studied using dihexyl-N,N-diethylcarbamoylmethylphosphonate (DHDECMP) and related compounds. It was found that very dilute (<0.1 M) solutions of ammonium thiocyanate were sufficient to allow quantitative extraction of Am(III) with DHDECMP. Significant differences between DHDECMP and dibutylbutylphosphonate (DB[BP]) in the extraction of Am(III) and Eu(III) from thiocyanate were found and indicate chelation is occurring with DHDECMP, unlike the situation in the low acid lithium nitrate system. Infrared spectroscopy of the extracted complexes of La(III) and extraction studies with dihexyl-N,N-diethylcarbamoylethylphosphonate (DHDECEP), dihexyl-N,N-diisobutylcarbamoylmethylphosphonate (DHDIBCMP), and di-(2-ethylbutyl)-N,N-diethylcarbamoylmethylphosphonate (DEBDECMP) confirm that chelation occurs with thiocyanate complexes of Am(III) and Eu(III). Separation factors, α, for Am(III) an...

Some oxygen-donor complexes of cyclopentadienyluranium(IV)N-thiocyanate; steric considerations and stability

Abstract: The oxygen-donor complexes [U(cp)(NCS)3L2][cp =η-C5H5, L = Me3CCONMe2(dmpva), Me2CHCONMe2(dmiba), PPh3O, and P(NMe2)3O (tdpo)] have been prepared and i.r. and u.v.–visible (solution and solid reflectance) spectra are reported for them. Analogous complexes with L = MeCONMe2(dma), EtCONMe2(dmpa), EtCONEt2(depa), pyridine, and 2,2′-bipyridyl could not be isolated and disproportionation to [U(cp)3(NCS)] and [U(NCS)4Lx] occurred. The observations are discussed in terms of the steric crowding about the uranium atom using a cone-packing model.

Stepwise sequence determination from the carboxyl terminus of peptides.

Abstract: The thiocyanate method for stepwise degradation of peptides from their COOH termini [Stark, G. R. (1968) Biochemistry 7, 1796] has been investigated. The method involves first the reaction of the COOH-terminal residue with thiocyanate in an activation solvent of acetic acid and acetic anhydride and then cleavage of the COOH-terminal residue as its 2-thiohydantoin by acetohydroxamate in aqueous solution. The two steps of the degradation have been studied by using model peptides, and conditions have been developed for the rapid efficient removal and identification of the COOH-terminal residue of short peptides. The methods have been applied to peptides that have been covalently attached to insoluble supports. In this solid phase version of the degradation, a highly substituted porous glass activated with N,N'-carbonyldiimidazole has been prepared for use as the insoluble support. A number of peptides have been coupled to the porous glass, and several rounds of the degradation have been performed on immobilized peptides. High-pressure liquid chromatography provides a rapid, sensitive identification method for the 2-thiohydantoins. In addition, gas-liquid chromatography of the amino acid 2-thiohydantoins and reconversion to the parent amino acid have been used to identify the cleaved residues. The method of sequential degradation has been applied to a number of short model peptides such as Gly-Leu-Tyr, Met-enkephalin, and Val-Leu-Ser-Glu-Gly and has been used to determine the COOH-terminal sequence of 4 residues of a 22-residue cyanogen bromide fragment of pygmy sperm whale myoglobin.

Raman study of vibrational and rotational dynamics of thiocyanate anion in aqueous solutions

Abstract: The Raman spectra of the CN stretching mode of linear SCN- ions have been recorded in aqueous LiSCN, NaSCN and KSCN solutions at concentrations 1–10 M and at temperatures 30, 55 and 80°C. The vibrational and rotational correlation functions are calculated. The vibrational width of about 27–50 cm-1 in these thiocyanate solutions is attributed to the vibrational dephasing due to interactions between a SCN- ion and surrounding water molecules and cations. The observed vibrational correlation functions are analysed by the stochastic line shape theory of Kubo, in which homogeneous and inhomogeneous broadening are treated simultaneously, and both contributions to the spectra are extracted. The inhomogeneous contribution is found to increase with decreasing the temperature and in 10 M LiSCN solution at temperatures below 55°C the band is found to be broadened predominantly by inhomogeneous processes. Even in dilute solutions inhomogeneously slow modulation is found to exist besides the fast process which gives t...

Simultaneous determination of cyanide and thiocyanate by high performance liquid chromatography.

Abstract: A sensitive, simple and specific method was developed for the simultaneous determination of cyanide and thiocyanate by high performance liquid chromatography with a strong base anion exchanger column. For detection, colorimetry based on the Konig reaction was employed with chloramine T, pyridine and barbituric acid as reagents. This method was applied to the determination of cyanide and thiocyanate in human urine.

Carboxyhaemoglobin and plasma thiocyanate: complementary indicators of smoking behaviour?

Abstract: Carboxyhaemoglobin and plasma thiocyanate concentrations were measured in 79 non-smokers and 360 cigarette smokers. The mean levels were 0.73% and 7.09% carboxyhaemoglobin and 40 . 2 and 133 . 8 mumol thiocyanate/1 plasma respectively. With 1 . 6% carboxyhaemoglobin and 73 . 0 mumol thiocyanate/1 plasma as critical values the concentrations of carboxyhaemoglobin in 96.6% of subjects and of thiocyanate in 93.4% were compatible with reported smoking status. This difference between the two tests is significant (p less than 0 . 005). Statistical combination of the carboxyhaemoglobin and thiocyanate results, with the use of linear discrimination analysis, only marginally improved their diagnostic efficiency (96.8% of subjects were grouped correctly). This analysis did, however, successfully regroup 21 of 26 individuals with contradictory carboxyhaemoglobin and thiocyanate classifications. It is concluded that in this study determination of thiocyanate added little to the information obtained from carboxyhaemoglobin measurements alone.

The effects of short-term fasting on the excretion of sulfur compounds in healthy subjects.

Abstract: The urinary excretion of sulfur-containing compounds was studied before, on the third, and on the seventh day of fasting in 10 healthy subjects. The excretion of total sulfur, inorganic sulfate, ester sulfate, “non-sulfate sulfur”, methionine, cystathionine, cysteine, N-acetylcysteine, taurine, thiosulfate and thiocyanate was decreased during fasting, whereas the excretion of mercaptoacetate was unaltered and that of mercaptolactate increased. The excretion of inorganic sulfate, taurine and thiocyanate was also decreased when calculated relative to that of total sulfur, suggesting that these compounds are derived mainly from dietary sulfur amino acids. The output of ester sulfate, methionine, cystathionine, cysteine and thiosulfate was unaltered in relation to that of total sulfur, indicating that these compounds are derived from both dietary and endogenous sulfur amino acids, liberated during protein catabolism. By contrast, the excretion of mercaptolactate and mercaptoacetate was increased relative to that of total sulfur, suggesting that these compounds are derived mainly from endogenous sulfur amino acids formed by the enchanced protein catabolism seen during fasting.

Lactoperoxidase and thiocyanate protect bacteria from hydrogen peroxide.

Abstract: Lactoperoxidase and thiocyanate were shown to protect Escherichia coli and three oral streptococcal species from the bactericidal effect of hydrogen peroxide under aerobic conditions. Lactoperoxidase in the absence of thiocyanate was also protective for two of the bacterial species in a dilution medium but potentiated hydrogen peroxide toxicity for the other two under the same conditions. The products of the reaction between hydrogen peroxide and thiocyanate in the presence of lactoperoxidase were not bactericidal except in the case of E. coli, and then only under special conditions. The results demonstrate the effectiveness of lactoperoxidase and thiocyanate in protecting living cells from hydrogen peroxide toxicity. Although the effect on human cells was not examined in this study, extrapolation of these results to the cells of the oral mucosa would suggest an important protective role of lactoperoxidase and thiocyanate against the toxic effects of hydrogen peroxide in the oral cavity.

Effect of inorganic phosphate and benzyl thiocyanate on the activity of anhydrotetracyline oxygenase in Streptomyces aureofaciens.

Abstract: The level of anhydrotetracycline oxygenase (an enzyme catalyzing the penultimate reaction in the biosynthesis of tetracycline) inStreptomyces aureofaciens was substantially influenced by the amount of inorganic phosphate and by the presence of benzyl thiocyanate in the cultivation medium. Phosphate decreased the specific activity of the enzyme, particularly when added to a growing culture. On the other hand, benzyl thiocyanate increased the specific activity of the enzyme. Its effect was most conspicuous in the growth phase. The effect of benzyl thiocyanate was more pronounced in the low-production strain than in the producing variant. Inorganic phosphate and benzyl thiocyanate did not influence the enzyme activityin vitro. Phosphate added to the growing cultures was readily absorbed by the cells. During this time the enzyme synthesis was repressed, derepression occurred only after exhaustion of phosphate from the medium. The stimulatory efect of benzyl thiocyanate on the enzyme synthesis was not reversed by the inorganic phosphate added.

Denitrosation of N-acetyl-N1-nitrosotryptophan in acid solution

Abstract: The denitrosation of DL-N-acetyl-N1-nitrosotryptophan has been studied kinetically in water in the acid range 4 × 10–2–1M-H2SO4 and also at lower acidities in buffer solutions pH 2–6. The reaction gave DL-N-acetyltryptophan and nitrous acid quantitatively and was not significantly reversible under these conditions. First-order behaviour was found for both the nitrosamine and acid in the sulphuric acid reactions, and the reaction was also acid-catalysed in the pH region 2–6. The reaction rate constant was unaffected by the addition of N-acetyltryptophan. In 0.04M-H2SO4 the rate constant was unchanged by the addition of bromide ion, thiocyanate ion, iodide ion, and thiourea, and the kinetic solvent isotope effect kH2O/kD2O was 1.3 at 0.7M-H2SO4 and 1.1 at 0.1M- H2SO4. However at pH 6 catalysis was observed by chloride, bromide, thiocyanate, azide, and iodide ion with increasing efficiency along this sequence. As the concentration of the nucleophile was increased the reaction rate constant tended to become independent of the nucleophile concentration. Thus N-acetyl-N1-nitrosotryptophan behaves as a typical nitrosamine at very low acidities around pH 6, whereas at higher acidities it shows a pattern of behaviour reminiscent of that shown by nitrosamides. The pH–rate profile for denitrosation shows clearly that there are two pathways associated with the acid-catalysed reaction, one predominant at around pH 4–7 and the other at acidities greater than pH 1. The former is associated with nucleophilic catalysis and the latter is not. The results are discussed in terms of two possible sites of protonation of the substrate (at O and C-3), and the changing effective rate limiting step, as the nucleophile concentration is changed. N-Acetyl-N1-nitrosotryptophan can be used to nitrosate (or diazotise) other species such as 4-nitroaniline, but only in the absence of a nitrous acid trap, indicating that this nitrosamine is not a direct nitrosating agent towards amines under these conditions. A minor photochemical decomposition pathway has been established for N-acetyl-N1-nitrosotryptophan at pH 6, but it was not examined in detail.

Crystal structure of catena-poly-(thiocynato-N)cadmium-di-µ-(thiocyanato-N)-(thiocyanato-N)cadmium-tris-µ-(4-t-butyl-1,2,4-triazole-N1:N2). A new, alternating zig-zag chain containing N-bonded, bridging thiocyanate

Abstract: the structure of [Cd2(NCS)4(butrz)3]∞(butyl = 4-t-butyl-1,2,4-triazole) consists of zig-zag chain with alternating bridges of three butrz groups and two unusual N-bonded isothiocyanate anions; the octahedral co-ordination around each cadmium ion is completed by a monodentate isothiocyanate anion.

Determination of thiocyanate, thiosulfate, sulfite and nitrite by high performance liquid chromatography coupled with electrochemical detection

Abstract: High performance liquid chromatography with an electrochemical detector (Yanaco Model VMD-101) was used to determine SCN-, S2O32-, SO32- and NO2-. Those anions were separated on a TSK-GEL IEX-520 QAE (anion exchanger) column, with a mobile phase of 0.05 M sodium phosphate buffer (pH 7.5) containing 0.05 M NaNO3 and were detected electrochemically at 0.9 V vs. Ag/AgCl. The minimum detectable amounts of SCN-, S2O32-, SO32- and NO2- were 0.015, 0.05, 2.5, 0.012 ppm, respectively.