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PubMed2003

Mass spectrometric study of aliphatic alpha-carbonyl azides.

A series of derivatives of 2-azidoacetic acid and 2-azidoacetone were synthesized and their behaviour under electron ionization conditions was investigated. This paper reports the electron ionization fragmentation mechanisms for five aliphatic alpha-carbonyl azides, which were clarified by accurate mass measurements and B/E linked scans. The substituent influences the abundance and the nature of the ions resulting from the molecular ion fragmentation.

Anti-HIV Agents↗
PubMed2000

Rapid inhibition by sodium azide of the phosphoinositide-mediated calcium response to serotonin stimulation in human platelets: preservation in Alzheimer's disease.

The effect of sodium azide (NaN(3)) upon platelet Ca(2+) signalling has been investigated. A 60 s preincubation with 1 mM NaN(3) reduced the Ca(2+) response to 1 microM serotonin without a corresponding reduction in the responses to 52 mU/ml thrombin or 70 microM beta-amyloid(25-35) (A beta(25-35)). The effect of NaN(3) upon the response to serotonin, which was not blocked by either glutathione ethyl ester (GTEE) or dithiothreitol (DTT), was similar in platelets obtained from patients with Alzheimer's disease and from age- and gender-matched controls. After a preincubation time of 5 min was used, the Ca(2+) response to thrombin was greatly reduced by 1 mM NaN(3), but not by 50 microM 4-hydroxynonenal (HNE, 50 microM). Platelet levels of HNE and malondialdehyde were not significantly affected by up to 30 min of incubation with NaN(3) at room temperature. It is concluded that the rapid effect of NaN(3) upon the Ca(2+) response to serotonin in human platelets is not mediated by an inhibition of cytochrome c oxidase, and is due to an action proximal to phosphoinositide-specific phospholipase C.

Adult↗
PubMed1982

An investigation into the feasibility of using azide-insensitive ATPase and ConA as yeast plasma membrane markers.

Cytochemical localization of Concanavalin A binding sites in protoplasts of Candida tropicalis, investigated with glycosylated-ferritin and electron microscopy, showed that the lectin was specifically bound to the external protoplast surface. Thus, the plasma membranes have been labelled with 125I-Concanavalin A and followed through the isolation procedure. Relative distribution of 125I-radioactivity and azide-insensitive ATPase activity in the obtained fractions, suggested that this enzyme was an equivocal plasma membrane marker. Despite the presence of internal Concanavalin A binding sites, Concanavalin A could be used unambiguously as an exogenous plasma membrane marker of intact protoplasts.

Adenosine Triphosphatases↗
PubMed1998

Intratubular application of sodium azide inhibits loop of Henle reabsorption and tubuloglomerular feedback response in anesthetized rats.

Sodium azide (NaN3, AZ) is a potent inhibitor and uncoupler of oxidative phosphorylation as well as a nitrovasodilator after being converted to nitric oxide (NO). We studied the effect of intratubular application of AZ on loop of Henle reabsorption and tubuloglomerular feedback (TGF) employing renal micropuncture experiments in nephrons with superficial glomeruli of anesthetized Munich-Wistar-Fromter rats. During perfusion of Henle's loop downstream from an obstructing wax block, AZ (3x10(-5) mol/l and 3x10(-4) mol/l) concentration-dependently increased early distal tubular flow rate and sodium and potassium ion concentration (V(ED), [Na+]ED, [K+]ED). In comparison, application of furosemide (10(-4) mol/l), the action of which is restricted to the water-impermeable thick ascending limb of Henle's loop (TALH) and the macula densa, similarly increased [Na+]ED and [K+]ED, but did not affect V(ED). The effect of AZ on loop of Henle reabsorption appeared to be predominantly localized upstream to the TALH since (1) AZ significantly inhibited net fluid reabsorption (the latter being completely abolished at 3x10(-4) mol/l), (2) the effect of AZ on [Na+]ED and [K+]ED could be mimicked by perfusing the Henle's loop at a flow rate that caused a comparable increase in V(ED) (reflecting a comparable load to TALH), and (3) the effects of AZ and furosemide were additive. In spite of the increase in [Na+]ED and [K+]ED, intratubular application of AZ caused a concentration-dependent inhibition of TGF response, the latter being assessed as the fall in early proximal tubular stop flow pressure during perfusion of Henle's loop at increasing flow rate. Like AZ and furosemide, the NO donor sodium nitroprusside (10(-4) mol/l) blunted the TGF response, but in contrast to furosemide or AZ, it caused a minor decrease in V(ED), without changing [Na+]ED or [K+]ED. The inhibitory effect of AZ on TGF was abolished by the NO scavenger carboxy PTIO. In summary, AZ inhibits both reabsorption in the water-permeable segment of Henle's loop and the TGF response. The effect on reabsorption may be linked to metabolic inhibition rather than NO release, whereas the blunted TGF response appears to involve conversion to NO.

Absorption↗
PubMed2000

Purification and properties of a novel azide-sensitive ATPase of Exiguobacterium aurantiacum.

Exiguobacterium aurantiacum BL77/1 possesses at least two distinct membrane-bound ATPases. One of them was solubilized with decanoyl N-methylglucamide, a non-ionic detergent, and purified by successive chromatography on DEAE-Sepharose and hydroxyapatite. The purified ATPase appears to consist of a single polypeptide component with an apparent molecular mass of 54 kDa. Among the triphosphates of various nucleosides tested, ATP was the best substrate. The enzyme exhibited a Km of 0.5 mM for ATP and a Vmax of 109 micromol ATP (mg protein)(-1) min(-1); the optimum pH for activity was near 6.5. The enzyme was sensitive to azide and inactivated by N,N'-dicyclohexylcarbodiimide. Analysis of the inhibition kinetics by N,N'-dicyclohexylcarbodiimide suggested that binding of the drug to a single carboxyl group per ATPase molecule is sufficient for inactivation.

Adenosine Triphosphatases↗
PubMed2003

Formation of platinated GG cross-links on DNA by photoactivation of a platinum(IV) azide complex.

Platinum(II) diam(m)ine complexes such as cisplatin are effective anticancer drugs but have accompanying side effects. We are exploring the design of platinum complexes with low toxicity that could be photoactivated selectively at the target site. We show here that the Pt(IV) azide complex cis, trans-[Pt(en)(N(3))(2)(OH)(2)] is unreactive towards DNA until irradiated with visible light. Transcription mapping studies of a 212-bp fragment of pSP73KB plasmid DNA treated with cis, trans-[Pt(en)(N(3))(2)(OH)(2)] and irradiated with visible light showed that the platination sites were similar to those observed for cisplatin, and were mainly in GG sequences. HPLC analysis of enzymatic digests of an irradiated sample of a 40-bp DNA duplex treated with the same complex also revealed preferential formation of GG cross-links. Since such DNA lesions are thought to be responsible for the induction of apoptosis in cancer cells by platinum drugs, the use of unreactive photoactivatable platinum pro-drugs may become an effective strategy for the design of a new generation of platinum anticancer complexes.

Antineoplastic Agents↗
PubMed2003

Theoretical potential functions and vibrational analysis for halocarbonyl azides CXO-NNN (X=F, Cl and Br).

The structural stability of halocarbonyl azides CXO-NNN (X=F, Cl and Br) was investigated by DFT and MP2 calculations using the 6-311++G** basis set. From the calculations, the molecules were found to have an s-cis<--> s-trans conformational equilibrium with cis being the lower -energy form. Full energy optimizations were carried out for the transition states and the minima at the B3LYP/6 -311++G** and MP2/6 -311++G** levels, from which the rotational barriers were calculated to be of the order 8-10 kcal x mol(-1). The vibrational frequencies were computed at the DFT -B3LYP level and the vibrational assignments for the normal modes of the stable conformers were made on the basis of normal coordinate calculations.

Azides↗
PubMed1987

(1-Pyrene)sulfonyl azide: a fluorescent probe for measuring the transmembrane topology of acetylcholine receptor subunits.

(1-Pyrene)sulfonyl azide (PySA), a fluorescent, lipophilic photolabel, was used as a probe for the transmembrane topology of the acetylcholine receptor (AchR) subunits. Photolabeling of native, alkaline-extracted, and reconstituted AchR membrane preparations resulted in the labeling of all the AchR subunits. However the reconstituted AchR membrane preparations incorporated twice as much PySA into each mole of the AchR complex. Photolabeling of all subunits of the AchR does not appear to alter the agonist concentration response of AchR-mediated cation translocation.

Animals↗
PubMed1980

Labeling of chromatophore membranes and reaction centers from the photosynthetic bacterium Rhodospirillum rubrum with the hydrophobic marker 5-[125I]iodonaphthyl-1-azide..

Chromatophores of the photosynthetic bacterium Rhodospirillum rubrum and isolated reaction centers were labeled with the lipophilic membrane marker 5-[125I]iodonaphthyl-1-azide. The two smaller reaction center proteins L and M bind more label than the larger subunit H, a fact supporting the proposed localisation of the 3 subunits obtained with hydrophilic labels. Besides these integral proteins the lipids, among them mainly the pigments and the quinones, are highly labeled suggesting a hydrophobic environment around these molecules and a preferred reactivity to iodonaphthylazide. Such a hydrophobic environment may be of great importance for the function of the photosynthetic reaction centers especially for the charge separation and the primary reactions in electron transport.

Azides↗
PubMed1980

Chloramphenicol-induction of a second cyanide-and azide-insensitive mitochondrial pathway in Ustilago maydis.

Growth of wild type Ustilago maydis in presence of chloramphenicol results in increased resistance of cyanide-insensitive respiration to hydroxamic acid derivatives. The biphasic nature of the Dixon plots for hydroxamate inhibition of mitochondrial alternative respiration suggested involvement of two cyanide-sensitive systems. This hypothesis was confirmed by the analysis of kinetic data. One of the two systems exhibits normal sensitivity to hydroxamates and appears similar to that present in mitochondria from cells grown in control medium. In contrast, the inducible system is characterised by resistance to hydroxamates and lower substrate affinity. With excess substrate and AMP in reaction mixutre the two systems have equal participation in the cyanide-insensitive respiration of chloramphenicol-treated mitochondria. In the absence of AMP, however, the inducible oxidase seems to exhibit much higher affinity for oxygen. The new system appears responsible also for changes in sensitivity of alternative respiration to low temperatures. It differs from the hydroxamate resistant systems recently reported for other fungi in its high activity and its complete insensitivity to azide and cyanide.

Adenosine Monophosphate↗
PubMed1983

EXAFS investigation of the binuclear cupric site in met T2D Rhus laccase and its azide bound derivative.

EXAFS analysis of met T2D Rhus laccase and its azide bound derivative indicates an average of 0.33 S at 2.09 A and 3-4 N (or O) atoms at 2.00 A per copper atom for the three copper centers. Using the plastocyanin Cu(II) EXAFS spectrum to model the type 1 site in laccase, a difference EXAFS spectrum for the type 3 site is generated; this spectrum enables assignment of the one S ligand in met T2D to the type 1 site and indicates no evidence of a detectable copper scatterer for the coupled binuclear copper site. Implications regarding type 3 optical features and related studies on the hemocyanins are also discussed.

Azides↗
PubMed1985

4-Fluoro-3-nitrophenyl azide, a selective photoaffinity label for type B monoamine oxidase.

The effects of 4-fluoro-3-nitrophenyl azide (FNPA) on types A and B monoamine oxidase in rat brain cortex were studied using serotonin and phenylethylamine as substrates respectively. FNPA competitively inhibited the oxidative deamination of both serotonin (Ki = 3 microM) and phenylethylamine (Ki = 0.78 microM) in the dark. Upon photoirradiation in the presence of FNPA, a photodependent inhibition of type B MAO activity resulted. This photodependent inhibition was apparently irreversible since there was no recovery of activity upon washing of the photolyzed FNPA-enzyme mixture. Additional evidence for the photoinduced covalent binding of FNPA to type B MAO is that non-competitive inhibition kinetics resulted after photolysis. The specificity of the photodependent incorporation of FNPA to type B MAO was shown by the protective effect of phenylethylamine and by decreased [3H]pargyline labeling after the enzyme was photolyzed with FNPA. Under the same experimental conditions, only minimal photodependent inhibition of type A MAO by FNPA was found. The observed difference in the efficiencies of the photodependent inactivation of the two types of MAO by FNPA suggests that there is a conformational or a structural difference in the active sites of the two types of MAO. The active site of type B MAO could be characterized by utilizing FNPA as a photoaffinity labeling probe.

Affinity Labels↗
PubMed1987

Photoaffinity labeling of beef liver monoamine oxidase-B by 4-fluoro-3-nitrophenyl azide.

4-Fluoro-3-nitrophenyl azide (FNPA) competitively inhibited beef liver monoamine oxidase-B (MAO-B) in the dark (Ki = 2.8 microM). Upon irradiation in the presence of FNPA, a concentration-dependent photoinactivation of MAO-B was observed. The kinetic analysis showed that the photoinactivation of MAO-B resulted in a decrease in Vmax but no change in Km. This result suggests that an irreversible linkage may be formed between the enzyme and the photolyzed FNPA. When [3H]FNPA was photoirradiated with the purified MAO-B, a single radioactive band associated with MAO-B was observed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The photo-dependent incorporation could be protected by phenylethylamine, the substrate for MAO-B, in a concentration-dependent manner. Complete tryptic-chymotryptic digestion of [3H]FNPA-labeled MAO-B resulted in three radioactive peaks on Sephadex G-25 column chromatography. With the same digestion and separation procedures, only one major radioactive peak was observed for the [3H]pargyline-labeled MAO-B, and its elution volume was different from that of [3H]FNPA-labeled peptides. These results suggest that, upon photolysis, FNPA may incorporate into a region in the active site of MAO-B which may be different from the pargyline binding site--the FAD prosthetic group of the enzyme.

Affinity Labels↗
PubMed1985

Alkali lability and rapid initiation of excision repair following photoaffinity damage by ethidium azide.

DNA damage and repair provoked by ethidium azide (EA) photoaffinity labeling in mouse leukemia cells was studied by measuring sedimentation properties of nucleoids in neutral sucrose gradients, and it was found that the strand opening step was faster than that which followed damage of cells by ultraviolet (UV) light. The two insults were compared at levels of damage which gave the same overall rates of repair synthesis in intact cells and which required the same length of time to complete repair, as judged by the restoration of supercoiling of the isolated nucleoids. In the case of UV, single-strand breaks in DNA were detectable at 30 min, maximum at 2 h, and the superhelical properties restored at 21 h. With photoaffinity labeling, single-strand breaks were prominent immediately, even when photolabeling of cells was done on ice, but restoration of DNA supercoiling still required 21 h. Photolabeling of isolated nucleoids or isolated viral DNA with EA failed to introduce DNA strand breaks. However, it was discovered that photoaffinity labeling of DNA with EA resulted in alkali labile sites shown by single strand breaks produced on alkaline sucrose sedimentation or by alkali exposure followed by sedimentation on neutral formamide gradients. These results suggest that the drug attachment sites should be identifiable by the location of such single strand breaks.

Affinity Labels↗
PubMed1995

The nitric oxide donors, azide and hydroxylamine, inhibit the programmed cell death of cytokine-deprived human eosinophils.

Azide and hydroxylamine release nitric oxide (NO) enzymatically in biological conditions. We observed that both compounds were able to inhibit in vitro the programmed cell death of human eosinophils from peripheral blood. This protective effect could be mimicked by permeable cGMP analogs and by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine. Moreover, the soluble guanylate cyclase inhibitor LY-83583 inhibited in a dose-response manner the effects of the NO donors. Consequently, via the increase of eosinophil survival, NO could contribute to the amplification of inflammatory and allergic processes. This effect appears to be mediated, at least in part, by the soluble guanylate pathway.

1-Methyl-3-isobutylxanthine↗
PubMed1987

Analysis of azide-insensitive Ca2+-dependent ATPase activity in atrial specimens from patients with coronary or valvular heart disease.

The activity of the azide-insensitive Ca2+-dependent ATPase (highly enriched in myofibrillar ATPase activity) was studied in specimens of both right and left atria which were taken from patients with ischemic and/or valvular heart disease during coronary by pass and/or valvular substitution. A significantly lower enzymatic activity was found in atrial specimens from patients with left ventricular heart failure in comparison to the atrial fragments obtained from the patients with normal heart function. Such an inhibition reflected a significant increase in the Km of the enzyme for ATP and was associated with a concomitant reduction in Vmax, both more evident in the left atrial fragments. Moreover, tissue homogenates of atrial specimens from failing hearts exhibited a lower protein SH group content when compared to the atrial homogenates from the heart with normal left ventricular heart function.

Azides↗
PubMed1996

Azide, cyanide, fluoride, imidazole and pyridine binding to ferric and ferrous native horse heart cytochrome c and to its carboxymethylated derivative: a comparative study.

Azide, cyanide, fluoride, imidazole, and pyridine binding to ferric and ferrous native horse heart cytochrome c and to its carboxymethylated derivative has been investigated, from the thermodynamic viewpoint, at pH 7.5 and 25.0 degrees C. Ligand affinity for ferric and ferrous carboxymethylated cytochrome c is higher by about 30- and 400-fold, respectively, than that observed for the native protein. The results here reported: (i) allow the estimation, for the first time, of the ligand-independent free energy associated with the heme-iron sixth coordination bond in ferric and ferrous native cytochrome c, which turns out to be +8.4 kJ mol-1 and +14.6 kJ mol-1, at 25.0 degrees C, respectively, and (ii) suggest an interplay between redox, structural, ligand binding, and recognition properties of cytochrome c.

Animals↗