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At least 973 records · Page 54Linked to original sources
PubMed2003

Cyanide binding study of neuronal nitric oxide synthase: effects of inhibitors and mutations at the substrate binding site.

In order to understand the heme distal structure of neuronal nitric oxide synthase (nNOS), we studied cyanide binding to the ferric wild-type and substrate binding site mutants, Glu592Ala and Tyr588His, of the isolated oxygenase domain in the absence and presence of substrates and inhibitors. Cyanide bound to isolated heme-bound oxygenase domains (nNOSox) in the absence of the substrates with the dissociation constant (K(d)) of 3.1 mM. The presence of the substrates, L-Arg and NHA, did not change the K(d) value. However, cyanide binding was almost abolished in the presence of inhibitors such as NAME, thiocitrulline and 7-NI. The effect of the inhibitors were not observed for the Glu592Ala mutant, while similar strong inhibiting effects were observed for the Tyr588His mutant. We discuss the binding fashion of those inhibitors to the heme substrate binding site of nNOS.

Arginine↗
PubMed1997

Hydrogen cyanide polymers from the impact of comet P/Shoemaker-Levy 9 on Jupiter.

Hydrogen cyanide polymers--heterogeneous solids ranging in color from yellow to orange to brown to black--may be among the organic macromolecules most readily formed within the Solar System. The non-volatile black crust of comet Halley, for example, as well as the extensive orange-brown streaks in the atmosphere of Jupiter, might consist largely of such polymers synthesized from HCN formed by photolysis of methane and ammonia. Laboratory studies of these ubiquitous compounds point to the presence of polyamidine structures synthesized directly from hydrogen cyanide. These would be converted by water to polypeptides which can be further hydrolyzed to alpha-amino acids. Other polymers and multimers with ladder structures derived from HCN would also be present and might well be the source of the many nitrogen heterocycles, adenine included, detected by thermochemolytic analysis. The dark brown color arising from the impacts of comet P/Shoemaker-Levy 9 on Jupiter could therefore be mainly caused by the presence of HCN polymers, whether originally present, deposited by the impactor or synthesized from freshly formed HCN. Spectroscopic detection of these predicted macromolecules and their hydrolytic and pyrolytic by-products would strengthen significantly the hypothesis that cyanide polymerization is a preferred pathway for prebiotic and extraterrestrial chemistry.

Evolution, Chemical↗
PubMed2000

Effect of chronic cyanide intoxication on memory in albino rats.

Cyanide is a chemical widely used in industry, and is a major environmental pollutant. Its toxicity is caused by inhibition of cytochrome oxidase resulting in histotoxic hypoxia. The effect of sublethal doses of cyanide on memory and hippocampal neurotransmitters was studied in male Wistar strain albino rats. Cyanide reduced the memory along with reduction in the levels of dopamine and 5-hydroxytryptamine in the hippocampus. Pre-existing malnutrition in the animals exaggerated these effects.

Animals↗
PubMed2002

Does prolonged oral exposure to cyanide promote hepatotoxicity and nephrotoxicity?

Long-term exposure to cyanide and/or its main metabolite, thiocyanate, has been associated with goiter, pancreatic diabetes and several neurological disorders. However, very little is found in the literature relating the nephrotoxic and hepatotoxic effects of these substances. Thus, the objective of the present study was to verify the effects of prolonged exposure to potassium cyanide (KCN) in these organs. Forty-six male adults rats, weighing approximately 200 g at the beginning of the experiment, were distributed into five groups-four experimental and one control. Experimental groups were dosed with target doses of 0.3, 0.9, 3.0 or 9.0 mg KCN/kg per day, in the drinking water, during 15 days and the control groups received only tap water. At the end of this experiment, all rats were subjected to euthanasia and plasma samples were obtained in order to determine thiocyanate and thyroidal hormones levels and fragments of thyroid, kidney and liver were collected. Rats treated with the highest cyanide dose (9.0 mg KCN/kg per day) showed lower body weight gain. An increase in the thiocyanate levels was verified in all experimental groups. The histopathologic study revealed hydropic degeneration of the renal tubular epithelial cells in those animals, which received KCN at the dose of 3.0-9.0 mg/kg per day. This study also showed hydropic degeneration of the hepatocytes of those animals, which received KCN at a dose of 9.0 mg/kg per day, and in the thyroid gland an increase was observed in the number of reabsorption vacuoles on follicular colloid, in a dose-dependent manner, in all animals of the experimental groups.

Animals↗
PubMed2003

Elution and decomposition of cyanide in soil contaminated with various cyanocompounds.

Standard soil samples contaminated with various standard cyanocompounds were prepared. Column elution experiments and analyses were conducted. Compounds with an easy capacity for dissociation to ions, such as KCN and potassium hexacyanoferrate(III), were found to be eluted by forming free cyanide even in fresh water. Hexacyanoferrate(II) salts, such as potassium hexacyanoferrate(II) and iron(III) hexacyanoferrate(II), were found not to be dissociated in water, but were dissociated and diffused under alkaline conditions (pH >13). Hexacyanoferrate(II) ion was found to be more easily dissociated in water with a higher pH. Column tests as above were also conducted for soil samples taken from a former paint ink factory using iron(III) hexacyanoferrate(II), cyanogen chloride, potassium cyanate, copper cyanide, as well as potassium cyanide, as raw materials. It was demonstrate that iron(III) hexacyanoferrate(II) was dissociated and eluted under alkaline conditions. The elution rate was reduced when the contaminated soil was sandwiched with standard soil layers.Further, it was found that the Fe(CN)(6)(4-) ion eluted with NaOH from hexacyanoferrate acid in soil, were easily decomposed into cyanic acid or other byproducts by UV with the addition of ozone and H(2)O(2).

Ferrocyanides↗
PubMed1998

Effects of 2-amino-7-phosphonohepatanoic acid, melatonin or NG-nitro-L-arginine on cyanide or N-methyl-D-aspartate-induced neurotoxicity in rat cortical cells.

When cortical neuronal cells were exposed to potassium cyanide (0.01, 0.05, 0.1, 0.5, or 1.0 mM) or N-methyl-D-aspartate (NMDA: 0.005, 0.01, 0.05, 0.1, or 0.2 mM) for 24 h at 37 degrees C in a 95% air and 5% CO2 environment, lactate dehydrogenase (LDH) efflux into the extracellular fluid from the cortical cells was significantly increased in a concentration dependent manner and morphological changes were observed. The increased LDH efflux and the morphological changes in cortical cells induced by potassium cyanide or NMDA were blocked by co-exposure to 2-amino-7-phosphonoheptanoic acid (AP7: 1.0 mM), a selective antagonist of the NMDA receptor, melatonin (1.0 mM), a potent hydroxyl and peroxyl radical scavenger, or NG-nitro-L-arginine (1.0 mM), an inhibitor of nitric oxide (NO) synthase. These results suggest that activation of NMDA receptor and NO synthase and/or free radical formation may contribute to the development of neurotoxicity induced by cyanide or NMDA.

2-Amino-5-phosphonovalerate↗
PubMed2000

Acute cyanide poisoning: a case report.

A case of attempted homicide by cyanide ingestion is reported. The victim, a 19-year-old woman, unknowingly ingested cyanide and presented to the Emergency Department unresponsive, in shock, and in profound metabolic acidosis. The differential diagnosis of this presentation and the patient's successful treatment are reviewed. The important management issues surrounding the treatment of cyanide poisoning are discussed.

Acidosis↗
PubMed2002

Rapid quantitation of cyanide in whole blood by automated headspace gas chromatography.

Cyanide (CN), a chemical asphyxiant, is a rapidly acting and powerful poison. We have developed a sensitive, rapid, simple, and fully automated method for measuring CN in whole blood. The assay is based on the use of gas chromatography (GC) with nitrogen-phosphorus detection and acetonitrile as an internal reference. Following the automated addition of phosphoric acid to the blood sample, the released hydrogen cyanide is analyzed using a fully automated headspace GC system. The assay, validated on human blood samples spiked with potassium cyanide and on clinical samples from fire victims who had smoke inhalation injury, can detect CN at a wide range of concentrations (30-6000 microg/l) in about 17 min (including incubation and GC run time, and <2 min for manual sample preparation). This automated, high-throughput, simple, and sensitive method is suitable for the rapid diagnosis of CN in clinical and forensic specimens.

Calibration↗
PubMed1983

Binding of metal cyanide complexes to bovine liver rhodanese in the crystalline state.

Bovine liver rhodanese, which catalyzes the transfer of sulfur atoms between a variety of sulfur donor and sulfur acceptor substrates, is inhibited by metal cyanide complexes [Volini, M., Van Sweringen, B., & Chen, F.-Sh. (1978) Arch. Biochem. Biophys. 191, 205-215]. Crystallographic studies are described which reveal the binding mode of four different metal cyanides to bovine liver rhodanese: Na[Au(CN2], K2[Pt(CN)4], K2[Ni(CN)4], and K2[Zn(CN)4]. It appears that these complexes bind at one common site at the entrance of the active site pocket, interacting with the positively charged side chains of Arg-186 and Lys-249. This observation explains the inhibition of rhodanese by this class of compounds. For the platinum and nickel cyanide complexes virtually no other binding sites are observed. The gold complex binds, however, to three additional cysteine residues, thereby also displacing the extra sulfur atom which was bound to the essential Cys-247 in the sulfur-rhodanese complex. The zinc complex binds to completely different additional sites and forms complexes with the side chains of Asp-101 and His-203. Possible reasons for these different binding modes are discussed in terms of the preference for "hard" and "soft" ligands of these four metal ions.

Animals↗
PubMed1984

Acceleration of the NAD cyanide adduct reaction by lactate dehydrogenase: the equilibrium binding effect as a measure of the activation of bound NAD.

The binary complex of NAD and lactate dehydrogenase reacts reversibly with cyanide to produce a complex (E X NAD-CN) whose noncovalent interactions are similar to those in the E X NADH complex (where E is one-fourth of the tetrameric dehydrogenase). The reaction apparently is a simple bimolecular nucleophilic addition at the 4 position of the bound nicotinamide ring; viz., cyanide does not bind to the enzyme prior to reaction. The value of the dissociation constant for E X NAD-CN is about 1 X 10(-6) M and is independent of pH over the range of 6-8. The equilibrium constant for the reaction of cyanide with E X NAD is about 400-fold larger than that for the nonenzymic process after a statistical correction. This increment in Ke is accounted for by a 220-fold increase in the rate of the forward enzymic reaction (20 M-1 s-1) as compared with an approximately 2-fold decrease for the reverse process (9 X 10(-5) s-1). Thus, the increased value of the rate constant for bond formation in the enzymic reaction is attributed to an equilibrium binding effect that is translated almost entirely into a rate effect on that step (bond formation). Since the nonenzymic reaction is sensitive to solvent composition, this equilibrium binding effect likely is produced by environmental effects at the nicotinamide/dehydronicotinamide part of the coenzyme binding site on the enzyme.

Animals↗
PubMed1996

Infrared spectroscopy of the cyanide complex of iron (II) myoglobin and comparison with complexes of microperoxidase and hemoglobin.

The cyanide complex of FeIIMb prepared and maintained at temperatures below 0 degrees C is sufficiently stable to permit spectroscopic characterization and allow comparison with free HCN and other ferric and ferrous CN complexes. The visible absorption spectrum of FeIIMb-CN has a split alpha band maxima at 571 and 563 nm, suggesting distortion in the x-y plane of the porphyrin. FeIIMb-CN, like the CO complex, was found to be optically active by circular dichroism. The C-N stretching frequencies for the CN-ferrous complexes are very sensitive to parameters within the heme pocket. The values are as follows: FEIIMb at pH 8, 2057 cm-1 with a shoulder appearing at 2078 cm-1 at pH 5.6; FeIIMp, 2034 cm-1. In contrast, the frequencies for C-N stretch differ little among ferric heme complexes, ranging from 2123 to 2125 cm-1 for myoglobin, hemoglobin, and microperoxidase. These values compare with free HCN (2094 cm-1) or CN- (2080 cm-1). Quantum chemical modeling of the neutral iron-porphyrin complex with imidazole and cyanide and of its anion was used to explain the effects of the cyanide coordination and of iron reduction on the C-N stretching frequencies. The lower nu C-N for FeIIMb-CN relative to the ferric complex is attributed to the appearance of additional electron density on all the anti-bonding CN orbitals. The extra electron density was also used to explain that the band width of C-N stretching mode was greater in the ferrous complexes than in the ferric complex. Finally, the calculation shows that sigma donation weakens the Fe-C bond, in qualitative agreement with the spontaneous dissociation of CN- from FeIIMb at -5 degrees C. The sensitivity of CN complexes of ferrous heme proteins to the heme pocket environment and the ability to correlate spectroscopic parameters with calculated electron density suggest that infrared spectroscopy of the CN ligand is an appropriate tool to study ferrous heme proteins.

Animals↗
PubMed1999

Comparative FTIR analysis of the microenvironment of in cyanide-treated, high pH-treated and iron-depleted photosystem II membrane fragments.

FTIR difference spectra due to light-induced formation were measured in control PS II membrane fragments and in samples where the magnetic interaction with the non-heme iron center in its high-spin Fe2+ state is eliminated by three different methods, i.e., extraction of the non-heme iron center, treatment with cyanide, and incubation at high pH (pH = 11). The results obtained reveal that (i) the most pronounced band at 1479 cm-1 reflecting the C../--O stretching mode of in the semiquinone anion radical remains invariant to "iron depletion" while it shifts by 4 and 2 cm-1 to lower frequencies upon cyanide and high pH treatments, respectively, (ii) peaks observed in the 2600-3000 cm-1 region which arise from Fermi resonance of harmonics and combinations of the imidazole ring modes with the hydrogen-bonding NH stretching vibrations are not affected upon iron depletion but are lost in cyanide and high pH-treated samples, and (iii) all three treatments give rise to some similar changes in the amide I bands of the protein backbones and in imidazole ring modes of the coupled histidine. These results show that the hydrogen-bonding interaction of is virtually unaffected upon non-heme iron depletion; in particular, the strong hydrogen bond between QA and a histidine side chain (most likely His 215 of the D2 subunit) is not changed. In marked contrast, drastic changes take place in the hydrogen bonding between QA and His upon CN- and high pH treatments. The straightforward interpretation is that the hydrogen bond is lost upon these treatments. Despite the striking difference in the effect of hydrogen-bonding interaction, all three treatments lead to similar structural pertubations on the protein conformational changes due to formation and ring vibrations of the coupled histidine side chain. On the basis of the data presented in the study, it is inferred that, concerning the hydrogen bond interaction, the microenvironment of is close to the native state when a suitable iron depletion is performed. Accordingly, the previously reported conclusion on the hydrogen-bonding pattern of in PS II [MacMillan, F., Lendzian, F., Renger, G., and Lubitz, W. (1995) Biochemistry 34, 8144-8156] studied by using iron-depleted preparations most likely reflects the situation in an intact PS II.

Cyanides↗
PubMed2001

Cyanide complexes of iron corrolates: spin delocalization and autoreduction.

Complex formation of (7,13-dimethyl-2,3,8,12,17,18-hexaethylcorrolato)iron chloride, [(7,13-Me(2)Et(6)C)FeCl], with cyanide ion in dimethylformamide, DMF-d(7), was studied by (1)H NMR spectroscopy. It is found that a bis-cyanide complex is formed initially, in which the electron configuration is a low-spin Fe(III) corrolate(2-*). This complex is not stable, and it is readily reduced with an excess of cyanide in the solution. The reduction occurs at the corrole ring instead of on the iron center giving the monocyanide complex of the low-spin Fe(III) corrole, [(7,13-Me(2)Et(6)C)FeCN](-). Thus, this is a case where an axial ligand serves as a reducing agent of the macrocycle and not of the metal.

Cations↗
PubMed2005

Mechanism and scope of the cyanide-catalyzed cross silyl benzoin reaction.

In this work, cross silyl benzoin addition reactions between acylsilanes (1) and aldehydes (2) catalyzed by metal cyanides are described. Unsymmetrical aryl-, heteroaryl-, and alkyl-substituted benzoin adducts can be generated in moderate to excellent yields with complete regiocontrol using potassium cyanide and a phase transfer catalyst. From a screen of transition metal cyanide complexes, lanthanum tricyanide was identified as an improved second-generation catalyst for the cross silyl benzoin reaction. A study of the influence of water on the KCN-catalyzed cross silyl benzoin addition revealed more practical reaction conditions using unpurified solvent under ambient conditions. A sequential silyl benzoin addition/cyanation/O-acylation reaction that resulted in two new C-C bonds was achieved in excellent yield. The mechanism of cross silyl benzoin addition is proposed in detail and is supported by crossover studies and a number of unambiguous experiments designed to ascertain the reversibility of key steps. No productive chemistry arises from cyanation of the more electrophilic aldehyde component. Formation of the carbon-carbon bond is shown to be the last irreversible step in the reaction.

Acylation↗
PubMed2004

A novel stereospecific synthesis of glycosyl cyanides from 1,2-O-sulfinyl derivatives.

[reaction: see text] An efficient synthesis of 1,2-trans-glycosyl cyanides via 1,2-O-sulfinyl monosaccharides is described. Such S(N)2-type displacements at the anomeric center are stereospecific and are best performed with sodium cyanide in the presence of ytterbium triflate. Significantly, the resulting 1,2-trans-glycosyl cyanides have a free hydroxyl group at C-2 ready for further modification.

Cyanides↗
PubMed2006

Acridinium salt based fluorescent and colorimetric chemosensor for the detection of cyanide in water.

A new, selective chemosensor has been developed to detect cyanide in water at micromolar concentrations. The acridinium salt used in this sensor system is prepared in a single step from an acridine orange base. Detection is based on the irreversible, 1:1 stoichiometric, nucleophilic addition of cyanide to the 9-position of the acridinium ion. This process induces a large decrease in fluorescence intensity and a marked color change. The selectivity of the system in aqueous media for CN- over other anions is remarkably high. Also, the sensitivity of both the fluorescence- and colorimetric-based assay is below the 1.9 microM suggested by the World Health Organization (WHO) as the maximum allowable cyanide concentration in drinking water. Thus, the chemodosimeter should be applicable as a practical system for the monitoring of CN- concentrations in aqueous samples. [structure: see text]

Acridine Orange↗
PubMed1998

Ammonia from iron(II) reduction of nitrite and the Strecker synthesis: do iron(II) and cyanide interfere with each other?

The question of whether the production of ammonia, from the reduction of nitrite by iron(II), is compatible with its use in the Strecker synthesis of amino acids, or whether the iron and the cyanide needed for the Strecker synthesis interfere with each other, is addressed. Results show that the presence of iron(II) appears to have little, or no, effect on the Strecker synthesis. The presence of cyanide does interfere with reduction of nitrite, but the reduction proceeds at cyanide/iron ratios of less than 4:1. At ratios of about 2:1 and less there is only a small effect. The reduction of nitrite and the Strecker can be combined to proceed in each other's presence, to yield glycine from a mixture of nitrite, Fe+2, formaldehyde, and cyanide.

Ammonia↗
PubMed2001

Cyanide-induced alterations to the biophysical conformations of the isolated fish liver.

The purpose of this study is to examine the applicability of an infared spectroscopic methodology for the study of an environmental problem. The effect of cyanide concentrations on the biophysical conformation of the fish liver homogenate was determined by using an attenuated total reflectance (ATR)/Fourier transform infrared (FT-IR) microspectroscopy. Alive male model fish, Tilapia Zillii, was used. The liver from fish was isolated and homogenized in pH 8.0 Tris buffer solution. The results indicate that the IR peak intensity increased markedly in the C-H stretching range (3000-2800 cm-1), ester C = O stretching of lipids (1743 cm-1) and carbohydrate bands (1195-950 cm-1), but decreased in the amide I at 1649 cm-1 and the free asymmetric stretching band of phosphate at 1261 cm-1 with the increase of KCN concentrations. The marked release of hepatic enzymes and glutathione into homogenate induced by cyanide might account for the higher IR spectral peak intensity of fish liver tissue after treatment with KCN. The cyanide was also found to induce the protein structure of fish liver homogenate from alpha-helical conformation to beta-conformation.

Animals↗