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PubMed1979

Reaction of azide radicals with amino acids and proteins.

The azide radical N3 reacts selectively with amino acids, in neutral solution preferentially with tryptophan (k (N3 + TrpH) = 4.1 X 10(9) dm3 mol(-1s-1) and in alkaline solution also with cysteine and tyrosine (k(N3 + CyS-) = 2.7 X 10(9) dm3 mol-1s-1) and k(N3 + TyrO-) equals 03.6 X 10(9) dm3 mol-1s-1). Oxidation of the enzyme yADH by N3 involves primary attacks, mainly at tryptophan residues, and subsequent slow secondary reactions. N3-induced inactivation of yADH is likely to occur upon oxidation of tryptophan residues in the substrate binding pocket (58-TrpH and 93-TrpH) since the substrate ethanol although unreactive with N3, protects yADH and since elADH, which does not contain tryptophan in the substrate pocket, is comparatively resistant against N3-attack. N3 exhibits low reactivity with nucleic acid derivatives and it is inert towards aliphatic compounds such as methanol and sodium dodecylsulphate.

Alcohol Oxidoreductases↗
PubMed2001

Catalase catalyzes nitrotyrosine formation from sodium azide and hydrogen peroxide.

Sodium azide (NaN3) is known as an inhibitor of catalase, and a nitric oxide (NO) donor in the presence of catalase and H2O2. We showed here that catalase-catalyzed oxidation of NaN3 can generate reactive nitrogen species which contribute to tyrosine nitration in the presence of H2O2. The formation of free-tyrosine nitration and protein-bound tyrosine nitration by the NaN3/catalase/H2O2 system showed a maximum level at pH 6.0. Free-tyrosine nitration induced by peroxynitrite was inhibited by ethanol and dimethylsulfoxide (DMSO), and augmented by superoxide dismutase (SOD). However, free-tyrosine nitration induced by the NaN3/catalase/H2O2 system was not affected by ethanol, DMSO and SOD. NO2- and NO donating agents did not affect free-tyrosine nitration by the NaN3/catalase/H2O2 system. The reaction of NaN3 with hydroxyl radical generating system showed free-tyrosine nitration, but no formation of nitrite and nitrate. The generation of nitrite (NO2-) and nitrate (NO3-) by the NaN3/catalase/H2O2 system was maximal at pH 5.0. These results suggested that the oxidation of NaN3 by the catalase/H2O2 system generates unknown peroxynitrite-like reactive nitrogen intermediates, which contribute to tyrosine nitration.

Animals↗
PubMed1958

Effects of potassium, sodium, and azide on the ionic movements that accompany activity in frog nerves.

Stimulation of intact or desheathed frog sciatic nerves produced an increase in the sodium content and a decrease in the potassium content of this tissue. In desheathed preparations the magnitudes of the changes in ionic contents decreased as the concentration of the potassium in the bathing solution was increased, while changing the external sodium concentration produced small effects on the ionic shifts. During tetanization, the rate of decline of the compound action potential also decreased as the external potassium concentration increased. Eliminating the activity respiration with 0.2 mM azide did not greatly modify the changes in sodium and potassium distribution that accompanied activity in either intact or desheathed nerves.

Action Potentials↗
PubMed2000

Abscission of Azolla branches induced by ethylene and sodium azide.

Treatment with ethylene accelerated the abscission of branches of Azolla filiculoides plants. An Azolla plantlet treated with ethylene at 10 microl liter(-1) divided into 4-5 fragments after a lag period of 6-8 h. Ethylene-induced abscission was effectively inhibited by cycloheximide and was associated with an increase in the activities of cellulase and polygalacturonase. At the fracture surface abscised after treatment with ethylene, dissolution of the primary walls of the abscission zone cells was apparent. However, the middle lamella between abscission zone cells was still present. Immunoelectron microscopy using anti-unesterified pectin (JIM5) and anti-methylesterified pectin (JIM7) monoclonal antibodies revealed the presence of both JIM5 and JIM7 epitopes in the wall between abscission zone cells of branches before abscission occurred. In the middle lamella remaining after ethylene-induced abscission, only JIM7 epitopes were observed. The features of ethylene-induced abscission described herein were different from those of the rapid abscission induced by sodium azide, which implies that they are mediated by different mechanisms. The possible mechanisms are discussed.

Cellulase↗
PubMed1990

The structure of iron superoxide dismutase from Pseudomonas ovalis complexed with the inhibitor azide.

The 2.9 A resolution structure of iron superoxide dismutase (FeSOD) (EC 1.15.1.1) from Pseudomonas ovalis complexed with the inhibitor azide was solved. Comparison of this structure with free enzyme shows that the inhibitor is bound at the open coordination position of the iron, with a bond length of 2.0 A. The metal moves by 0.4 A into the trigonal plane to produce an orthogonal geometry at the iron. Binding of the inhibitor also causes a movement of the axial ligand (histidine 26) away from the metal, a lengthening of the iron-histidine bond, and a rotation of the histidine 74 ring. The inhibitor possesses contacts in the binding pocket with a pair of conserved tryptophan residues and with the side chains of tyrosine 34 and glutamine 70. This glutamine is conserved between all FeSODs, but is absent in MnSOD. Comparisons with MnSOD show that a different glutamine which possesses the same interactions in the active site as Gln70 in FeSOD is conserved at position 154 in the overall SOD sequence, implying that while manganese and FeSODs are structural homologues in a global sense, their functional and evolutionary relationship is that of second-site mutation revertants.

Amino Acid Sequence↗
PubMed1982

5-Isothiocyanato-1-naphthalene azide and rho-azidophenylisothiocyanate. Synthesis and application in hydrophobic heterobifunctional photoactive cross-linking of membrane proteins.

Two hydrophobic, heterobifunctional azidoarylisothiocyanates have been synthesized. The reagents are applicable for group-directed modification of membrane-integrated protein segments and subsequent photo-induced cross-linking with neighbouring membrane constituents. Both 5-isothiocyanato-1-naphthalene azide and p-azidophenylisothiocyanate are chemically characterized with respect to structure and photosensitivity. The reagents compete for the documented phenylisothiocyanate binding site(s) in bacteriorhodopsin and to the anion-exchange protein (band 3) of human erythrocytes. Photoactivation of azidoarylisothiocyanate-labeled membrane proteins leads to homopolymers when cross-linked in purple membranes or in vesicles enriched in the anion-exchange protein.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1991

NMR study of Galeorhinus japonicus myoglobin. 1H-NMR evidence for a structural alteration on the active site of G. japonicus myoglobin upon azide ion binding.

The heme molecular structure of the met-azido form of the myoglobin from the shark Galeorhinus japonicus has been investigated by 1H NMR. A nuclear Overhauser effect (NOE) was clearly observed among the heme peripheral side-chain proton signals of this complex, which undergoes thermal spin equilibrium between high-spin (S = 5/2) and low-spin (S = 1/2) states, and the NOE connectivities provided the assignment of the resonances from the heme C13(1)H2 and C17(1)H2 protons. Chemical shift inequivalence of these proton resonances not only provided information about the orientation of these methylene protons with respect to the heme plane, but also allowed characterization of the time-dependent build-up of the NOE between them, which yields the correlation time for the internal motion of the inter-proton vector. The relatively large mobility found for the C17(1)H2 group suggests that the carboxyl oxygen of the heme C17 propionate is not anchored to the apo-protein by a salt bridge. It has been shown that the ferric high-spin form of G. japonicus Mb possesses a penta-coordinated heme [Suzuki, T. (1987) Biochim. Biophys. Acta 914, 170-176; Yamamoto, Y., Osawa, A., Inoue, Y., Chûjô, R. & Suzuki, T. (1990) Eur. J. Biochem. 192, 225-229] and that the conformation of both heme propionate groups is fixed with respect to the heme, as well as the apo-protein, by a salt bridge [Yamamoto, Y., Inoue, Y., Chûjô, R. & Suzuki, T. (1990) Eur. J. Biochem. 189, 567-573]. Therefore the weakening or interruption of the interaction between the C17 propionate and His FG3 upon the changes of the coordination and spin state of the heme iron, during azide ion binding to ferric high-spin G. japonicus Mb, is attributed to the displacement of the FG corner of the apoprotein away from the heme C17 propionate group. A similar structural alteration has been revealed by X-ray structural analyses of unliganded and liganded forms of ferrous hemoproteins [Baldwin, J. & Chothia, C. (1979) J. Mol. Biol. 129, 175-220; Phillips, S.E.V. (1980) J. Mol. Biol. 142, 531-554].

Animals↗
PubMed1974

Development of a selective enterococcus medium based on manganese ion deficiency, sodium azide, and alkaline pH.

Rogosa broth, without its salt supplement and dissolved in deionized water, was adapted for the selective isolation and enumeration of enterococci. This medium supported good growth of enterococci, but it suppressed growth of other lactic acid bacteria. The sensitivity and specificity of the medium were tested after addition of various increasing concentrations of NaN(3) against known strains of enterococci and other bacteria. Many strains of Streptococcus faecium showed low azide tolerance; optimal growth was obtained at a concentration of 0.01% NaN(3), which totally or partially inhibited unrelated species of lactic acid bacteria. The selectivity of the medium was further increased by pH adjustment to 9.6. Carbonate and Tween 80 were added to overcome partial inhibition of enterococcal growth by the new combination of selective conditions. The final medium was evaluated in agar form in isolations from human and animal feces, polluted water, meat, and dairy products. Counts were obtained after 16 to 17 h of incubation at 37 C. The isolates satisfactorily conformed to the group characteristics of enterococci.

Azides↗
PubMed2006

Identification of PhIL1, a novel cytoskeletal protein of the Toxoplasma gondii pellicle, through photosensitized labeling with 5-[125I]iodonaphthalene-1-azide.

The pellicle of the protozoan parasite Toxoplasma gondii is a unique triple bilayer structure, consisting of the plasma membrane and two tightly apposed membranes of the underlying inner membrane complex. Integral membrane proteins of the pellicle are likely to play critical roles in host cell recognition, attachment, and invasion, but few such proteins have been identified. This is in large part because the parasite surface is dominated by a family of abundant and highly immunogenic glycosylphosphatidylinositol (GPI)-anchored proteins, which has made the identification of non-GPI-linked proteins difficult. To identify such proteins, we have developed a radiolabeling approach using the hydrophobic, photoactivatable compound 5-[(125)I]iodonaphthalene-1-azide (INA). INA can be activated by photosensitizing fluorochromes; by restricting these fluorochromes to the pellicle, [(125)I]INA labeling will selectively target non-GPI-anchored membrane-embedded proteins of the pellicle. We demonstrate here that three known membrane proteins of the pellicle can indeed be labeled by photosensitization with INA. In addition, this approach has identified a novel 22-kDa protein, named PhIL1 (photosensitized INA-labeled protein 1), with unexpected properties. While the INA labeling of PhIL1 is consistent with an integral membrane protein, the protein has neither a transmembrane domain nor predicted sites of lipid modification. PhIL1 is conserved in apicomplexan parasites and localizes to the parasite periphery, concentrated at the apical end just basal to the conoid. Detergent extraction and immunolocalization data suggest that PhIL1 associates with the parasite cytoskeleton.

Amino Acid Sequence↗
PubMed1998

Evaluation of the oxolinic acid--esculin--azide medium for the isolation and enumeration of faecal streptococci in a routine monitoring programme for bathing waters.

m-Enterococcus agar (m-Ent) has been generally considered the reference medium for faecal streptococci in bathing waters. However, it shows several shortcomings, and therefore it is important to test newly developed media that can guarantee more precise results. In this sense, the recently described oxolinic acid--esculin--azide agar medium (OAA) and m-enterococcus agar (m-Ent) were comparatively evaluated for the detection of faecal streptococci from seawater and fresh water. The OAA medium showed a significantly higher relative recovery percentage and specificity for both types of water than m-Ent. A similar spectrum of species was recorded from both media, Enterococcus faecium being predominant in fresh water and Enterococcus faecalis, in seawater. The superior performance of the OAA medium in both types of bathing waters, added to the fact that it does not require the use of complementary confirmative tests, makes this medium an excellent candidate to be employed for monitoring programmes.

Azides↗
PubMed2005

Sodium azide dilates coronary arterioles via activation of inward rectifier K+ channels and Na+-K+-ATPase.

Sodium azide (NaN(3)), a potent vasodilator, causes severe hypotension on accidental exposure. Although NaN(3) has been shown to increase coronary blood flow, the direct effect of NaN(3) on coronary resistance vessels and the mechanism of the NaN(3)-induced response remain to be established. To address these issues without confounding influences from systemic parameters, subepicardial coronary arterioles were isolated from porcine hearts for in vitro study. Arterioles developed basal tone at 60 cmH(2)O intraluminal pressure and dilated acutely, in a concentration-dependent manner, to NaN(3) (0.1 microM to 50 microM). The NaN(3) response was not altered by the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester or endothelial removal. Neither inhibition of phosphoinositol 3-kinase and tyrosine kinases nor blockade of ATP-sensitive, Ca(2+)-activated, and voltage-dependent K(+) channels affected NaN(3)-induced dilation. However, the vasomotor action of NaN(3) was significantly attenuated in a similar manner by the inward rectifier K(+) (K(IR)) channel inhibitor Ba(2+), the Na(+)-K(+) ATPase inhibitor ouabain, or the guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ). Ba(2+), in combination with either ouabain or ODQ, nearly abolished the vasodilatory response. However, there was no additive inhibition by combining ouabain and ODQ. The NaN(3)-mediated vasodilation was also attenuated by morin, an inhibitor of phosphatidylinositolphosphate (PIP) kinase, which can regulate K(IR) channel activity. With the use of whole cell patch-clamp methods, NaN(3) acutely enhanced Ba(2+)-sensitive K(IR) current in isolated coronary arteriolar smooth muscle cells. Collectively, this study demonstrates that NaN(3), at clinically toxic concentrations, dilates coronary resistance vessels via activation of both K(IR) channels and guanylyl cyclase/Na(+)-K(+)-ATPase in the vascular smooth muscle. The K(IR) channels appear to be modulated by PIP kinase.

Animals↗
PubMed2004

C-reactive protein does not relax vascular smooth muscle: effects mediated by sodium azide in commercially available preparations.

C-reactive protein (CRP), an acute-phase protein and newly recognized indicator of cardiovascular risk, may have direct actions on the vascular wall. Previous studies suggest that CRP is a vasodilator that activates smooth muscle K(+) channels. We examined the reported vasoactive properties of CRP and further explored its mechanisms of action. CRP decreased blood pressure in rats and increased coronary flow in open-chest dogs at a constant coronary perfusion pressure. CRP relaxed rat aortic rings and mesenteric small arteries that were contracted with phenylephrine. Relaxation was not affected by endothelial denudation or inhibition of nitric oxide (NO) synthase but was blocked by inhibition of soluble guanylate cyclase or K(+) channels. CRP solutions remained effective, i.e., elicited vasodilation, even after boiling or enzymatic digestion, which suggests the presence of a nonprotein contaminant. Sodium azide (NaN(3), 0.1%) is the preservative used for commercially available CRP and a potential source of NO. NaN(3) elicited the same cardiovascular effects as CRP preparations at equal concentrations, and its actions were blocked by inhibition of guanylate cyclase and K(+) channels. NaN(3)-free CRP, prepared by gel-filtration centrifugation and confirmed by electrophoresis, had no effect on vascular tone. Inhibition of vascular smooth muscle catalase with 3-amino-1,2,4-triazole completely prevented the effects of NaN(3) and NaN(3)-containing CRP solutions. We demonstrate that the acute vasoactive properties of commercially available CRP preparations are attributable to NaN(3) (and subsequent production of NO by catalase); therefore, this study suggests a reappraisal of the acute role of CRP in regulating vascular tone.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1987

Use of azide and hydrogen peroxide as an inhibitor for endogenous peroxidase in the immunoperoxidase method.

We describe a simple and effective method for inhibition of endogenous peroxidase activity in the immunoperoxidase technique. Specimens are pre-treated with a mixture of azide and hydrogen peroxide, which is then followed by an indirect immunoperoxidase procedure. Comparison studies showed no significant loss of antigenicity or morphological details by this pre-treatment. The method is most useful for evaluating cell-specific antigens on specimens that have abundant endogenous peroxidase activity, such as blood and bone marrow.

Azides↗
PubMed2005

Application of intramolecular 1,3-dipolar cyclic addition of azide and olefin; construction of (pyrrolidine-2-ylidene)glycinate and glycinamides.

Oxopropyl E-(pyrrolidine-2-ylidene)glycinamide (5c) and allyl E-(pyrrolidine-2-ylidene)glycinate (5d) were effectively synthesized from 2,3,5-tri-O-benzyl-4-O-tert-butyldimethylsilyl(TBDMS)-D-arabinal (7) using intramolecular 1,3-dipolar cyclic reaction of azide and olefin as a key reaction. These results proved this cyclic reaction should be applicable for the synthesis of various (pyrrolidine-2-ylidene)glycinate and glycinamide. In addition, the development of a synthetic route for the precursor of an unsaturated cyclic dehydro amino acid involved in azinomycins (carzinophilin) using relating glycinate, methyl E-(pyrrolidine-2-ylidene)glycinate (5a) was described.

Alkenes↗
PubMed1989

[Synthesis and reactivity of anthracene-1-carbonyl azide as a fluorescent derivatization reagent for alcohols].

Anthracene-1-carbonyl azide was found to be a sensitive fluorescent derivatization reagent for primary and secondary alcohols for high-performance liquid chromatography. Reaction conditions were investigated for cholestanol. The reagent reacts with alcohols in benzene in the presence of 4-dimethylaminopyridine to give the corresponding fluorescent urethanes at 100 degrees C for 50 min. The detection limit for cholestanol was 250 fmol for an injection volume of 10 microliters. Tertiary alcohols and phenols do not produce fluorescent derivatives under these conditions.

Alcohols↗
PubMed2003

Protective effect of benidipine against sodium azide-induced cell death in cultured neonatal rat cardiac myocytes.

We investigated the effect of benidipine, a calcium antagonist, against sodium azide (NaN(3))-induced cell death in cultured neonatal rat cardiac myocytes with increase of LDH release, depletion of cellular ATP contents, and collapse of mitochondrial membrane potential (DeltaPsi) as indicators. Cells were treated with 1 mmol/L NaN(3) for 18 h. Benidipine concentration-dependently inhibited NaN(3)-induced cell death. The protective effect of benidipine was compared with those of amlodipine, nifedipine, candesartan, and captopril. Calcium antagonists exhibited a protective effect and the IC(50) values of benidipine, amlodipine, and nifedipine were 0.65, 90, and 65 nmol/L, respectively. NaN(3)-induced cell death was inhibited completely with the calpain inhibitor. It was considered that the sustained elevation of [Ca(2+)](i) might be implicated in NaN(3)-induced cell death. Benidipine, moreover, concentration-dependently preserved cellular ATP contents and maintained DeltaPsi the extent of the control level. In conclusion, benidipine exhibited the protective effect at an approximately 100-fold lower concentration than those of amlodipine and nifedipine in the NaN(3)-induced cardiac cell death model. It was considered that both the inhibition of Ca(2+) influx and the preservation of cellular ATP contents might play an important role in the protective effect of benidipine.

Adenosine Triphosphate↗
PubMed1988

Medicinal azides. Part 3. The metabolism of the investigational antitumour agent meta-azidopyrimethamine in mouse tissue in vitro.

1. The experimental antitumour agent meta-azidopyrimethamine is deactivated by reduction of the azide moiety to yield meta-aminopyrimethamine. This reaction was followed by h.p.l.c. subsequent to incubation of the drug with homogenates prepared from liver, kidney, spleen, intestine and heart of mice. Reducing activity was highest in liver homogenate and was time dependent. Following the incubation of 530 nmol meta-azidopyrimethamine with liver homogenate equivalent to 1 g liver for 30 min under air, 84% of the agent was reduced to meta-aminopyrimethamine. 2. Reducing activity was markedly lower in incubations containing subcellular fractions obtained from liver homogenate. Under aerobic conditions the 700 g and 12,500 g supernatant fractions were able to reduce 57% and 23%, respectively, of the amount of meta-azidopyrimethamine initially present. The respective pellets possessed weak reducing ability, but on reconstitution of the supernatants with their corresponding pellets most of the reducing activity as observed in the whole homogenate was recovered. 3. Microsomes and mitochondria reduced the drug only when incubations were performed in the presence of nitrogen but not under air. 4. A fraction of the reducing activity measured in the tissue homogenates was non-enzymatic, as heat-inactivated homogenates retained less than 10% of the activity exhibited by the untreated homogenates. Neither bovine serum albumin nor glutathione could reduce meta-azidopyrimethamine under the conditions of the tissue incubations, whereas dithiothreitol was a powerful reductant. The mixed enzymatic and non-enzymatic nature, the tissue distribution and the diffuse subcellular localisation of meta-azidopyrimethamine reducing activity resemble features of the bioreduction of N-oxides.

Animals↗