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PubMed1985

Thermodynamics of the reaction of ferric myoglobin from Aplysia limacina with azide and fluoride. Dependence of enthalpy changes on pH.

The effect of pH on the enthalpy changes for binding of azide and fluoride to ferric myoglobin from Aplysia limacina, which lacks the distal histidine, has been investigated. Over the whole pH range explored (3.8 to 9.5), -delta H degrees values for the formation of the hemoprotein-ligand complexes are: (1) much greater than the variations in -delta G degrees; (2) always negative; and (3) show a dependence upon pH characterized by a maximum for azide and a minimum for fluoride binding, centered at pH 4.55 (identical to pHch). This value agrees well with that expected from the linear correlation between pHch and the simple function "Lys+Arg-Glu-Asp-2" proposed by Beetlestone and others. Data reported here greatly extend the pH range for which the linear correlation between the net charge of the macromolecule and pHch has been found to hold, and indicate unequivocally that the pH dependence of -delta H degree for the binding of anionic ligands does not uniquely require the presence of the histidyl residue at the distal position.

Animals↗
PubMed1992

Nonsteroidal estrogens bearing acyl azide functions: potential electrophilic and photoaffinity labeling agents for the estrogen receptor.

In an effort to develop novel affinity labeling agents for the estrogen receptor, we have synthesized two nonsteroidal ligands, a 1-aroyl-2-aryl tetralin system (1) and a 2-aryl-3-aroylbenzo[b]thiophene system (2). These agents, patterned after the Lilly antiestrogens trioxifene and LY 117018, respectively, embody acyl azide functions as part of a benzoyl chromophore. The acyl azide group has weak acylating activity, suitable for electrophilic affinity labeling, but this function is also photoreactive and, in its particular embodiment within these ligands, it could provide an efficient photochemical route to the highly reactive singlet acyl nitrene. The tetralin system (1) was prepared in nine steps from 6-methoxy-1-tetralone, and the benzothiophene system (2) was prepared in four steps from a known substituted benzo[b]thiophene precursor. In competitive binding assays, both compounds show reasonable binding affinity for the rat and lamb uterine estrogen receptor: estradiol = 100%, 1 = 3%, and 2 = 12%. When assayed by indirect receptor consumption assays, both compounds appear to have substantial capacity for irreversible binding (electrophilic reaction) with the receptor. This reactivity, which suggests that acylation of the receptor has occurred, is photoreversible. The nature of this ligand-receptor interaction is being investigated further.

Affinity Labels↗
PubMed1986

Synthesis and mutagenicity of the two stereoisomers of an azide metabolite (azidoalanine).

The L- and D-isomers of azidoalanine (azide metabolite) have been chemically synthesized with 60% yield using corresponding N-(tert-butoxycarbonyl)-serine as starting materials. The mutagenic properties of synthesized L-azidoalanine are very similar to those of azide and in vivo synthesized azidoalanine. Synthetic D-azidoalanine shows very low mutagenic activity on Salmonella typhimurium TA1530 strain compared to that of the L-isomer. Thus a stereoselective process is involved in azidoalanine mutagenicity. The data presented in this study suggest that further biochemical activation is required for L-azidoalanine to produce its mutagenic activity.

Alanine↗
PubMed1991

Dimeric and tetrameric hemoglobins from the mollusc Scapharca inaequivalvis. Reaction of the oxidized derivatives with azide and fluoride.

The reaction of the oxidized derivatives of the dimeric (HbI) and tetrameric (HbII) Scapharca inaequivalvis hemoglobins with azide and fluoride has been studied. The two oxidized hemoglobins have specific characteristics. Oxidized HbI consists of a dimeric high-spin aquomet form which is in a pH-dependent association-dissociation equilibrium with a monomeric low-spin hemichrome. In contrast, in HbII the high-spin aquomet derivative is only a transient species that converts itself into a tetrameric hemichrome which in turn dissociates into lower molecular weight forms. The reaction of oxidized HbI with azide and fluoride can be described in terms of a simple reaction scheme which assumes that external ligands bind only to the aquomet derivative. In the case of HbII, the reaction route is the same; however, the situation is complicated by the fact that in the dissociated hemichromes the internal protein ligand can no longer be displaced. Therefore, irreversible processes take place whose relevance depends primarily on the affinity of the external ligand for the ferric heme iron.

Animals↗
PubMed1991

Phthalocyanine-sensitized lipid peroxidation in cell membranes: use of cholesterol and azide as probes of primary photochemistry.

Various phthalacyanine (Pc) derivatives of phototherapeutic interest have been shown to be efficient type II (singlet oxygen, 1O2) sensitizers in aqueous and non-aqueous solutions. However, primary Pc photochemistry in biological environments, e.g. cell membranes, has not been studied in a definitive manner. To address this question, we used endogenous cholesterol in the erythrocyte ghost as a mechanistic reporter lipid Membranes sensitized with chloroaluminum Pc tetrasulfonate (AlPcS) and exposed to white light at 10 degrees C underwent lipid peroxidation, as indicated by the accumulation of hydroperoxides and thiobarbituric acid reactivity. Specific analysis of cholesterol photo-products by thin layer chromatography and high performance liquid chromatography revealed the presence of 3 beta-hydroxy-5 alpha-cholest-6-ene-5-hydroperoxide (5 alpha-OOH), with much smaller amounts of 3 beta-hydroxycholest-5-ene-7 alpha-hydroperoxide (7 alpha-OOH) and 5 alpha-cholest-6-en-3 beta, 5-diol and cholest-5-en-3 beta, 7 alpha-diol (5 alpha-OH and 7 alpha-OH). Identification of 5 alpha-OOH as a major photoproduct provides unambiguous evidence for large scale 1O2 intermediacy. Azide inhibited lipid peroxidation in a dose-dependent fashion, providing additional support for a type II mechanism. However, the 1O2 quenching constant from Stern-Volmer analysis was approximately 50 times lower than that determined for a non-membrane probe, lactate dehydrogenase. The latter value agreed with literature values. A probable explanation is that membrane-bound dye generates most of the 1O2 involved in lipid peroxidation. Although azide can intercept any 1O2 escaping into (or formed in) the medium, it has limited access to 1O2 generated on the membrane and reacting (or being quenched) near its site of origin.

Azides↗
PubMed2006

Interactions of sodium azide with triazine herbicides: effect on sorption to soils.

Sodium azide (NaN(3)) is one of the biocides commonly used to inhibit microbial growth during sorption experiments. However, a few reports have suggested that NaN(3) can react with the analyte of interest. In this study, the interactions of NaN(3) with triazine herbicides were investigated and the effect of atrazine transformation on its sorption to soil was evaluated. The concentration of atrazine in the presence of NaN(3) decreased significantly over period of time. After 14 days, only 38% of the initial atrazine concentration (10 mg l(-1)) was detected in a solution containing 1,000 mg l(-1) NaN(3) at pH 5.5. The magnitude and the rate of atrazine transformation increased with increase in NaN(3) load and with decrease in pH. In contrast to atrazine behavior, the concentrations of prometon and ametryn did not change during the experiment. GC/MS analysis indicated that the chlorine atom of atrazine is replaced by the azide group yielding 2-azido-4-(ethylamino)-6-(isopropylamino)-s-triazine. Atrazine transformation by NaN(3) significantly affected sorption of herbicide to soil. The presence of NaN(3) affects indirectly the sorption of atrazine due to competitive effect of its derivative. Our results demonstrated that the application of NaN(3) as a biocide in sorption-desorption experiments must be carefully evaluated. This issue is vital for sorption experiments conducted over long periods of time or/and with concentration of NaN(3) higher than 100 mg l(-1).

Adsorption↗
PubMed2005

On the vibrational spectra and structural parameters of methyl, silyl, and germyl azide from theoretical predictions and experimental data.

The infrared and Raman spectra of methyl, silyl, and germyl azide (XN3 where X=CH3, SiH3 and GeH3) have been predicted from ab initio calculations with full electron correlation by second order perturbation theory (MP2) and hybrid density function theory (DFT) by the B3LYP method with a variety of basis sets. These predicted data are compared to previously reported experimental data and complete vibrational assignments are provided for all three molecules. It is shown that several of the assignments recently proposed [J. Mol. Struct. (Theochem.) 434 (1998) 1] for methyl azide are not correct. Structural parameters for CH3N3 and GeH3N3 have been obtained by combining the previously reported microwave rotational constants with the ab initio MP2/6-311+G(d,p) predicted values. These "adjusted r0" parameters have very small uncertainties of +/-0.003 A for the XH distances and a maximum of +/-0.005 A for the heavy atom distances and +/-0.5 degrees for the angles. The predicted distance for the terminal NN bond which is nearly a triple bond is much better predicted by the B3LYP calculations, whereas the fundamental frequencies are better predicted by the scaled ab initio calculations. The results are discussed and compared to those obtained for some similar molecules.

Azides↗
PubMed2006

Theoretical investigation of the structure and vibrational spectra of carbamoyl azide.

Molecular structure and vibrational frequencies of carbamoyl azide NH2CO-NNN have been investigated with ab initio and density functional theory (DFT) methods. The molecular geometries for all the possible conformers of the molecule were optimized using DFT-B3LYP, DFT-BLYP and MP2 applying the standard 6-311++G** basis set. From the calculations, the molecule was predicted to exist predominantly in cis conformation with the cis-trans rotational barrier of about 7.91-9.10 kcal/mol depending on the level of theory applied. The vibrational frequencies and the corresponding vibrational assignments of carbamoyl azide in Cs symmetry were examined theoretically and the calculated Infrared and Raman spectra of the molecule in the cis conformation were plotted. Observed frequencies for normal modes were compare with those calculated from normal mode coordinate analysis carried out on the basis of ab initio and DFT force fields using the standard 6-311++G** basis set of the theoretical optimized geometry. Theoretical IR intensities and Raman activities are reported.

Azides↗
PubMed2002

Association of pharaonis phoborhodopsin with its cognate transducer decreases the photo-dependent reactivity by water-soluble reagents of azide and hydroxylamine.

pharaonis phoborhodopsin (ppR; also pharaonis sensory rhodopsin II, psRII) is a receptor of the negative phototaxis of Natronobacterium pharaonis. In halobacterial membrane, ppR forms a complex with its transducer pHtrII, and this complex transmits the light signal to the sensory system in the cytoplasm. In the present work, the truncated transducer, t-Htr, was used which interacts with ppR [Sudo et al. (2001) Photochem. Photobiol. 74, 489-494]. Two water-soluble reagents, hydroxylamine and azide, reacted both with the transducer-free ppR and with the complex ppR/t-Htr (the complex between ppR and its truncated transducer). In the dark, the bleaching rates caused by hydroxylamine were not significantly changed between transducer-free ppR and ppR/t-Htr, or that of the free ppR was a little slower. Illumination accelerated the bleach rates, which is consistent with our previous conclusion that the reaction occurs selectively at the M-intermediate, but the rate of the complex was about 7.4-fold slower than that of the transducer-free ppR. Azide accelerated the M-decay, and its reaction rate of ppR/t-Htr was about 4.6-fold slower than free ppR. These findings suggest that the transducer binding decreases the water accessibility around the chromophore at the M-intermediate. Its implication is discussed.

Archaeal Proteins↗
PubMed1999

Azide reduces the hydrophobic barrier of the bacteriorhodopsin proton channel.

The sensitivity of a nitroxide spin label to the polarity of its environment has been used to estimate the hydrophobic barrier of the proton channel of the transmembrane proton pump bacteriorhodopsin. By means of site-specific mutagenesis, single cysteine residues were introduced at 10 positions located at the protein surface, in the protein interior, and along the proton pathway. After reaction with a methanethiosulfonate spin label, the principle values of the hyperfine tensor A and the g-tensor were determined from electron paramagnetic resonance spectra measured at 170 K. The shape of the hydrophobic barrier of the proton channel is characterized in terms of a polarity index, DeltaA, determined from the variation of the hyperfine coupling constant Azz. The maximum of the hydrophobic barrier is found to be close to the retinal chromophore in the proton uptake pathway. The effect of the asymmetric distribution of charged and polar residues in the proton release and uptake pathways is clearly reflected in the behavior of the hydrophobic barrier. The presence of azide reduces the barrier height of both the cytoplasmic and extracellular channels. This finding supports the view of azide and other weakly acidic anions as catalysts for the formation of hydrogen-bonded networks in proton pathways of proteins.

Azides↗
PubMed1997

Mitochondrial toxins in models of neurodegenerative diseases. I: In vivo brain hydroxyl radical production during systemic MPTP treatment or following microdialysis infusion of methylpyridinium or azide ions.

Mitochondrial electron transport chain (ETC) function is selectively reduced in multiple tissues, including brain, from patients with Parkinson's disease (PD) and Alzheimer's disease (AD). The ETC defects are specific to each illness, involve complex I in PD and complex IV in AD, are transferable with mitochondrial DNA (mtDNA) and lead to increased production of reactive oxygen species (ROS) in mtDNA-deficient clonal neuronal cells hybridized with mtDNA ('cybrids') from PD or AD patients. C57BL/6 mice treated with MPTP developed elevated tissue hydroxyl radical ('OH) levels in striatum and ventral midbrain but not cerebellum. In brain microdialysis in awake rats, striatal 'OH output increased 3-5-fold after infusion of methylpyridinium ion (MPP+), a complex I inhibitor, or sodium azide, a complex IV inhibitor. Elevated 'OH after MPP+ was blocked stereospecifically by infusion of the nitric oxide synthase (NOS) inhibitor nitro-L-arginine or by the NMDA channel blocker MK801. Neither NOS inhibition nor NMDA blockade altered azide-induced 'OH production. ETC inhibition in vivo increases production of toxic 'OH, but the underlying mechanisms vary as a function of which ETC complex is inhibited. These results support the concept of developing oxygen free radical scavengers for both AD and PD and further suggest that inhibition of NOS and blockade of NMDA receptor function may alter progression of idiopathic PD.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2002

One-step synthesis of non-anomeric sugar isothiocyanates from sugar azides.

Tandem Staudinger-aza-Wittig reaction of primary azidodeoxy sugars with triphenylphosphine-carbon disulfide affords the corresponding primary deoxyisothiocyanato sugars in high yield. No products arising from O --> N acyl migration or formation of dimeric carbodiimides were observed. Interestingly, a polymer-supported triarylphosphine can advantageously replace triphenylphosphine, thus limiting the purification step to a simple filtration process. The reaction also allows the preparation of 5-deoxy-5-isothiocyanato sugars, a hitherto unknown class of compounds, from the corresponding azide precursors. Secondary sugar azides bearing the azido group at an endocyclic carbon atom afforded much lower isothiocyanation yields under these reaction conditions.

Azides↗
PubMed1983

Spectral properties and reactivity towards azide of Dicrocoelium dendriticum met-hemoglobin.

The spectroscopic properties of Dicrocoelium dendriticum met-hemoglobin, investigated between pH 3.8 and 10.5, display two proton-induced transitions with apparent pK values of 8.1 and 4.7. The spectral changes, over the pH region 6.5 to 10.5, correspond to the high to low spin transition usually observed in ferric hemoproteins. The relaxation time (tau = 3.2 ms at the pK) associated with this transition is closely similar to that observed in Aplysia limacina met-myoglobin, but approximately 1000-fold slower than that of sperm whale met-myoglobin. The spectral changes associated with the more acid transition are in the opposite direction and have not been resolved by the temperature jump method. The rate constants for the reaction of azide with Dicrocoelium dendriticum met-hemoglobin were measured between pH 3.8 and 6.7 by the temperature jump method. Two kinetic schemes, both consistent with the pH dependence of the apparent rate constant for binding of azide, were identified. No objective way of discriminating between the two models is available. However, one of them is amenable to a physical interpretation based on a comparison with the structural, kinetic and spectral properties of other monomeric hemoproteins.

Animals↗
PubMed1977

Induction of DNA single-strand breaks in barley by sodium azide applied at pH 3.

Sodium azide (1 to 50 mM), adjusted to pH 3 and applied for 2 h to presoaked barley seeds, induced a dose-dependent frequency of single-strand breaks in DNA of non-germinating embryos. This was demonstrated by sedimentation analyses of isolated DNA samples in alkaline sucrose gradients and in neutral sucrose gradients with 80% formamide. The doses applied also inhibited dose dependently the root length, seed germination and partially the seedling height. Only the sub-lethal doses (10 and 12.5 mM) induced a low frequency of chromatid breaks and translocations in the root tip metaphases. The sedimentation rate (in alkaline sucrose gradients) of calf thymus DNA treated with sodium azide at pH 3, was similar to that of the control DNA treated with buffer (pH 3) alone.

Azides↗
PubMed2004

Sodium-azide versus ProClin 300: influence on the morphology of UHMWPE particles generated in laboratory tests.

Ultra-high molecular-weight polyethylene (UHMWPE) has been used in total joint replacement for the last three decades and is currently the best polymer available for this use. Nevertheless, the wear of UHMWPE remains a serious clinical problem. Polyethylene wear debris has been identified as a cause of osteolysis and a major factor reducing the life of the total hip arthroplasty. Debris generated at the articular surfaces enters the periprostethic tissue where it is phagocyted by macrophages. Studies have shown that particles in the 0.1-10microm size range are particularly important in causing adverse cellular reactions resulting in osteolysis. The morphology, size, mass, and number of wear particles produced in a hip joint simulator are influenced by the tribological conditions used during the experiment. This paper shows that the morphology of the UHMWPE particles generated in vitro is influenced by the type of lubricant used. This study compared, quantitatively and qualitatively, particles generated in vitro using bovine calf serum as lubricant with two different preservatives: sodium azide and ProClin 300. No significant difference was observed with regards to wear between the two types of lubricant used. Quantitative analysis of the wear particles showed that particles generated in serum with sodium azide were not [corrected] morphologically different from those produced in serum with ProClin 300 [corrected]

Animals↗
PubMed2000

The ferric form of the three human embryonic hemoglobins and their reactions with azide ions.

The ferric forms of the three human embryonic hemoglobins exhibit pH titration's with pKa values in the range 8.25-8.6, which correlate with the reduced proteins affinity for oxygen. Azide ions bind to each ferric protein in a process consisting of two separate binding steps. The equilibrium constants for this process are in the 10-30 microM range and can be assigned to the individual chain within the proteins as reactivity appears independent of the nature of the partner chain. The kinetics of the azide binding reactions occur on the second time scale at mM ligand concentrations and also indicate the presence of two distinct processes that have been assigned to each of the two chains within the proteins. Non of these processes indicate any evidence of heme-heme interactions within the ferric form of the proteins. These findings are discussed in comparison with previously reported properties of adult ferric hemoglobin.

Adult↗
PubMed1998

1H NMR studies of azide binding to cytochrome c.

The binding of azide ion to the heme iron of ferricytochrome c in D2O is studied using 1H NMR methods at pH 7.0 and 300 K or 315 K. Some hyperfine shifted resonances arising from heme peripheral protons and resonances of side-chain protons of some amino acid residues in N3-cyt c have been assigned using 2D EXSY and DQF-COSY methods. The majority of the heme pocket side-chain proton signals have been identified. The 1D nuclear overhauser effect (NOE) difference spectra and 2D NOESY spectrum are presented and changes in NOE patterns between the heme and certain residues, and several residues around the axial ligand are interpreted in terms of changes in the pocket structure. Interpretation of NOE data indicates that conformation changes are obvious on the Met80 side of the heme cavity in the environment of the axial ligand in N3-cyt c. In addition, kinetics analysis of azide binding to cyt c is studied using 2D EXSY method.

Animals↗