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At least 19 recordsLinked to original sources
PubMed1981

Temperature dependence of resonance Raman spectra of metmyoglobin and methemoglobin azide. Detection of resonance-enhanced bound azide vibrations and iron-azide stretch.

Resonance Raman spectroscopy has been employed to study the thermal spin equilibria in metmyoglobin azide [Fe(III)Mb-N3] and methemoglobin azide [Fe(III)-Hb-N3]. The effect of temperature on Raman intensities permits us to assign lines to either high- or low-spin species. With excitation at 647.1 nm the intensity of an 15N3 isotope-sensitive mode at approximately 411 cm-1 was found to increase with decreasing temperature, indicating that its origin may not be the high-spin charge-transfer band at approximately 640 nm as suggested by Asher & Schuster [Asher, S. A. & Schuster, T. M. (1979) Biochemistry 18, 5377]. Instead, it may be enhanced via the weaker low-spin z-polarized charge-transfer band at approximately 650 nm which was identified by Eaton & Hochstrasser [Eaton, W. A., & Hochstrasser, R. M. (1968) J. Chem. Phys. 49, 985]. Our normal coordinate analysis on the model azide-Fe-imidazole and the polarized nature of the line allow us to establish that the approximate 411-cm-1 mode in Fe(III)Mb-N3 and Fe(III)Hb-N3 is assignable to the Fe-N3 stretch of low-spin species. Furthermore, we assign the out of plane azide mode (low spin) to the depolarized line at 573 cm-1 (15N3 isotope sensitive), which was previously assigned as the Fe-N3 stretch by Desbois et al. [Desbois, A., Lutz, M., & Banerjee, R. (1979) Biochemistry 18, 1510]. No internal vibrations of bound azide excitation at 406.7 nm, we have observed the enhancement of the antisymmetric azide stretch (both high and low spin), out of plane bending (low spin), and Fe-N3 stretch (low spin), indicating the existence of at least two charge-transfer transitions underlying the strong Soret band. The following four types of charge transfer are discussed in the light of our present resonance Raman data: (1) porphyrin (pi) leads to high-spin Fe (d pi), (2) azide (n) leads to low-spin iron (dz2), (3) azide (pi) leads to low-spin iron (dz2), and (4) azide (pi) leads to porphyrin (pi) (high spin).

Animals↗
PubMed1991

Medicinal azides. Part 8. The in vitro metabolism of p-substituted phenyl azides.

1. A series of p-substituted aromatic azides was synthesized and their metabolism investigated in suspensions of mouse liver microsomes and mouse hepatocytes. Metabolite analysis was performed by h.p.l.c. 2. On incubation with microsomes under anaerobic conditions p-nitro, p-cyano- and p-chlorophenyl azide afforded metabolites which co-chromatographed with the respective aromatic amines. The rate at which p-nitrophenyl azide was metabolically reduced was approximately 20-fold that observed for p-cyano- and p-chlorophenyl azide. 3. Phenyl azide, p-methoxyphenyl azide and the aliphatic congener, phenethyl azide, did not furnish detectable amounts of metabolites on incubation with microsomes under anaerobic conditions. When phenyl azide and p-methoxyphenyl azide were incubated with hepatocytes or microsomes under aerobic conditions the resulting chromatograms furnished peaks which co-eluted with authentic p-hydroxyphenyl azide. 4. The microsomal reduction of p-nitrophenyl azide was dependent upon the presence of viable microsomes and NADPH, and on the absence of oxygen above the incubation medium.

Aerobiosis↗
PubMed1980

Resonance Raman spectra of manganese myoglobin and its azide complex. Assignment of a new charge-transfer band to azide (pi) to porphyrin (pi) transition.

The enhancement of bound azide vibrations at 650 [depolarized (dp), bending] and 2039 cm-1 (dp, antisymmetric stretch) upon excitation at approximately 400-460 nm indicates the existence of a new charge-transfer transition in manganese(III) myoglobin-azide complex. The assignments of these two vibrational modes are based on the agreement of their 15N3 isotope shifts (22 and 70 cm-1) with the calculated values (22 and 69 cm-1), the depolarized nature, and their close proximity to the corresponding vibrations in ionized azide. The Mn-(III)-N3 stretch has not been observed in the present study although the Fe(III)-N3 stretch at 413 cm-1 (polarized) was reported [Asher, S. A., Vickery, L. E., Schuster, T. M., & Sauer, K. (1977) Biochemistry 16, 5849]. The RR spectra of MnIIIMb-azide between 150 and 300 cm-1 differ dramatically from those of FeIIIMb-azide exicted in the 640-nm charge-transfer band or near the Soret band. There are lines at 170 and 282 cm-1 (both polarized) in the MnIIIMb-azide spectra which exhibit extremely large resonance enhancements and are unshifted by 15N3 isotope substitution. These two lines, having no analogue in other heme protein spectra, may be tentatively assigned to the out-of-plane porphyrin ring vibrations, with the latter involving significant Mn(III)-N(pyrrole) stretch. The enhancement of non totally symmetric azide modes suggests that the charge-transfer state may be mixed with other excited electronic states (possibly band Va or band VI) via Herzberg-Teller vibronic couplings. The lack of enhancement of the Mn(III)-N3 stretch leads to our present assignment of azide (pi) to porphyrin (pi) charge-transfer transition rather than azide (pi) to metal (dz2) or azide (n) to metal (dz2).

Azides↗
PubMed1989

Sodium azide mutagenesis in mammals: inability of mammalian cells to convert azide to a mutagenic intermediate.

Sodium azide is unique among mutagens. It is highly mutagenic in many plant and bacterial species but marginally mutagenic in mammalian cells. A possible explanation for this difference in mutagenic efficiency may lie in the inability of mammalian cells to convert azide to the putative ultimate mutagen. Normal human fibroblasts and Chinese hamster cells or cell-free extracts from these cell lines were treated with azide and the sonicates tested for mutagenicity in Salmonella strain TA1530. The data suggest that neither cell line was capable of converting azide to a mutagenic intermediate. In addition, both cell lines expressed the enzyme O-acetylserine(thio)-lyase which is responsible for the conversion of azide to azidoalanine, the putative mutagenic intermediate. Although mammalian cells possess the enzyme responsible for the conversion of azide to azidoalanine, they appear incapable of converting azide into a mutagenic intermediate in appreciable quantities. Further, the data support the conclusion that azide may be further modified in mammalian cells to an intermediate that is not genotoxic.

Animals↗
PubMed1991

Efficient and selective photoaffinity labeling of the estrogen receptor using two nonsteroidal ligands that embody aryl azide or tetrafluoroaryl azide photoreactive functions.

3-(4-Azido-2,3,5,6-tetrafluorobenzoyl)-6-hydroxy-2-(4- hydroxyphenyl)benzo[b]thiophene 1 (tetrafluoroaryl azide, TFAA) and its protio analogue 3-(4-azidobenzoyl)-6- hydroxy-2-(4-hydroxyphenyl)benzo[b]thiophene 2 (protioaryl azide, PAA), photoaffinity labeling (PAL) reagents for the estrogen receptor (ER), have been prepared in high specific activity tritium-labeled form (19 Ci/mmol) and shown to undergo selective and efficient photocovalent attachment to ER from rat uterus. Both azides 1 and 2 demonstrate high binding affinity for ER as determined by both a competitive binding assay (relative binding affinities: estradiol = 100; TFAA = 9.3; PAA = 66) and a direct binding assay (Kd: estradiol = 0.24 nM; TFAA = 2.64 nM; PAA = 0.37 nM). When unlabeled TFAA and PAA are irradiated at greater than 315 nm, they demonstrate site-specific photoinactivation of ER that reaches 43% and 55%, respectively, by 30 min. Specific photocovalent attachment to ER can be effected by irradiation of the tritium-labeled azides; the covalent attachment efficiency is good (1 = 20-30%, 2 = ca. 25%) and the selectivity of ER labeling is high. Characterization of the photolabeled proteins by SDS-polyacrylamide gel electrophoresis shows specific labeling of a major component at Mr 60,000 and a minor species at Mr 46,000, the same two species that are labeled by [3H]tamoxifen aziridine, a well-characterized affinity label for ER. The ER-specific antibodies H222Sp gamma and D547Sp gamma show a clean precipitation of only these two species. In the MCF-7 human breast cancer cell line, PAA is a full estrogen agonist in terms of stimulation of cell proliferation and induction of progesterone receptor. These two azides provide the first system in which the photocovalent attachment efficiency of an aryl azide can be compared to its tetrafluorosubstituted aryl azide analogue in a complex biological receptor system. Azides 1 and 2 are the most efficient and selective PAL reagents prepared to date for ER, and they should be useful in further studies of the hormone-binding domain of this protein.

Affinity Labels↗
PubMed1995

Interference of sodium azide with the quantitation of bilirubin: modification of Fog's method to eliminate azide interference.

Interference of sodium azide with bilirubin estimation was studied at different concentrations of sodium azide. At an azide concentration (0.08% or 12.3 mM), 99% inhibition of the color reaction was observed. Similar results were obtained when the effect of sodium azide was studied by fixing bilirubin concentration and increasing the azide concentration. The decrease in color reaction can be explained on the basis of competition of the two compounds, i.e., bilirubin and sodium azide for diazosulfanilic acid. The method was modified to measure the concentration of bilirubin in various serum samples containing different amounts of sodium azide.

Azides↗
PubMed2002

The chemistry of amine-azide interconversion: catalytic diazotransfer and regioselective azide reduction.

Azides have proven to be useful precursors to amines in organic syntheses. This report describes an improvement of the diazotransfer reaction and the first example of a regioselective azide reduction of compounds containing multiple azides. The use of a specific ratio of solvents and zinc chloride as a catalyst resulted in a more efficient diazotransfer reaction capable of delivering >90% conversion per amine with shorter reaction times than those previously reported. Azides can be reduced with good regioselectivity in moderate yields by a modification of the Staudinger reaction using trimethylphosphine at low temperatures. Electronic factors determine the selectivity for azide reduction, and the reaction is predictable by NMR analysis of the starting material. Several examples for the diazotransfer and regioselective azide reduction reactions are given, and a mechanistic hypothesis for both is proposed.

Amines↗
PubMed1995

Acquisition of azide-resistance by elevated SecA ATPase activity confers azide-resistance upon cell growth and protein translocation in Bacillus subtilis.

We isolated four azide-resistant secA mutants of Bacillus subtilis and found that all of them were the result of a single amino acid replacement of threonine 128 of SecA by alanine or isoleucine. In the presence of 1.5 mM sodium azide, cell growth and protein translocation of the wild-type strain were completely inhibited, but those of the azide-resistant mutant strains were not. Wild-type and two mutant SecA proteins were purified. Both the basal level and the elevated ATPase activity of the mutant SecA proteins were threefold higher than those of the wild-type SecA. The elevated ATPase activity of the SecA mutants was reduced upon the addition of 1.5 mM sodium azide by only 5-10% as compared with 40% for that of the wild-type. These results indicate that the elevated ATPase activity of the SecA mutants is resistant to sodium azide and that is also required for the protein translocation process of B. subtilis.

Adenosine Triphosphatases↗
PubMed2001

A novel approach for the formation of carbon-nitrogen bonds: azidation of alkyl radicals with sulfonyl azides.

Two preparatively attractive methods for the azidation of alkyl radicals are described. Secondary and tertiary alkyl iodides and dithiocarbonates are easily converted into the corresponding azides, either by reaction with ethanesulfonyl azide in the presence of dilauroyl peroxide, or by treatment with benzenesulfonyl azide and hexabutylditin in the presence of a radical initiator. Interestingly, intramolecular tandem radical cyclization-azidation processes can be performed in high yields.

Journal Article↗
PubMed1987

B-cells purified using azide give different responses in vitro to B-cells purified without azide.

Some established techniques for B-cell enrichment include azide in the media. Here, B-cells were enriched using a technique which transiently exposed the cells of 15 mM sodium azide. After 3-4 days in culture, the precursor frequency of autoantibody-secreting cells in this population was 0.113%. In contrast, when B-cells were enriched using a technique which eliminated their exposure to sodium azide, the number of autoantibody-secreting precursor cells detected in cultures was increased up to 20-fold. Therefore, it is concluded that transient exposure to azide affects functional activities of B-cells in vitro.

Animals↗
PubMed1990

Azide-resistant mutants of Escherichia coli alter the SecA protein, an azide-sensitive component of the protein export machinery.

Escherichia coli azi mutants, whose growth is resistant to millimolar concentrations of sodium azide, were among the earliest E. coli mutants isolated. Genetic complementation, mapping, and DNA sequence analysis now show that these mutations are alleles of the secA gene, which is essential for protein export across the E. coli plasma membrane. We have found that sodium azide is an extremely rapid and potent inhibitor of protein export in vivo and that azi mutants are more resistant to such inhibition. Furthermore, SecA-dependent in vitro protein translocation and ATPase activities are inhibited by sodium azide, and SecA protein prepared from an azi mutant strain is more resistant to such inhibition. These studies point to the utility of specific inhibitors of protein export, such as sodium azide, in facilitating the dissection of the function of individual components of the protein export machinery.

Adenosine Triphosphatases↗
PubMed2004

Base-promoted reactions of bridged ketones and 1,3- and 1,4-haloalkyl azides: competitive alkylation vs azidation reactions of ketone enolates.

The reactions of 1,3- and 1,4-haloalkyl azides with enolates of 2-norbornanone (and a ring-expanded analog) afford polycyclic 1,2,3-triazolines in good yields. The reaction occurs by the initial azidation of the ketone enolate, followed in order by triazoline formation and O-alkylation. An interesting element of this process is the preferential reaction of the alkyl azide with an enolate anion as opposed to the more familiar reaction of the alkyl halide (including Cl and I derivatives). Reactions of acyclic or monocyclic enolates generally lead to 1,2,3-triazoles but none of the alternative C-alkylation product.

Alkylation↗
PubMed2003

Fragmentation of carbohydrate anomeric alkoxyl radicals. A new synthesis of chiral beta-iodo azides, vinyl azides, and 2H-azirines.

[reaction: see text] The reaction of 3-azido-2,3-dideoxy-hexopyranose compounds from the d-gluco, d-galacto, d-lacto, and l-arabino carbohydrate series, with (diacetoxyiodo)benzene and iodine, generated 2-azido-1,2-dideoxy-1-iodo-alditols with one carbon less than the starting carbohydrate. These beta-iodo azides could be transformed by dehydroiodination into vinyl azides, which in turn afforded 3-monosubstituted 2H-azirines under thermal conditions. These beta-iodo azides and 2H-azirines may be interesting chiral synthons for the preparation of more complex heterocyclic systems.

Alcohols↗
PubMed2004

Crystal structure and magnetic interactions in nickel(II) dibridged complexes formed by two azide groups or by both phenolate oxygen-azide, -thiocyanate, -carboxylate, or -cyanate groups.

Tridentate/tetradentate Schiff base ligands L(1) and L(2), derived from the condensation of o-vanillin or pyridine-2-aldehyde with N,N-dimethylethylenediammine, react with nickel acetate or perchlorate salt and azide, cyanate, or thiocyanate to give rise to a series of dinuclear complexes of formulas [Ni(L(1))(micro(1,1)-N(3))Ni(L(1))(N(3))(OH(2))].H(2)O (1), [[Ni(L(1))(micro(1,1)-NCS)Ni(L(1))(NCS)(OH(2))][Ni(L(1))(micro-CH(3)COO)Ni(L(1))( NCS) (OH(2))]] (2) [[2A][2B]], [Ni(L(1))(micro(1,1)-NCO)Ni(L(1))(NCO)(OH(2))].H(2)O (3), and [Ni(L(2)-OMe)(micro(1,1)-N(3))(N(3))](2) (4), where L(1) = Me(2)N(CH(2))(2)NCHC(6)H(3)(O(-))(OCH(3)) and L(2) = Me(2)N(CH(2))(2)NCHC(6)H(3)N. We have characterized these complexes by analytical, spectroscopic, and variable-temperature magnetic susceptibility measurements. The coordination geometry around all of the Ni(II) centers is a distorted octahedron with bridging azide, thiocyanate/acetate, or cyanate in a micro(1,1) mode and micro(2)-phenolate oxygen ion for 1-3, respectively, or with a double-bridging azide for 4. The magnetic properties of the complexes were studied by magnetic susceptibility (chi(M)) versus temperature measurements. The chi(M) nus T plot reveals that compounds 1 and 4 are strongly ferromagnetically coupled, 3 shows a weak ferromagnetic behavior, and 2 is very weakly antiferromagnetically coupled.

Journal Article↗
PubMed2004

Trimethylsilylnitrate-trimethylsilyl azide: a novel reagent system for the synthesis of 2-deoxyglycosyl azides from glycals. Application in the synthesis of 2-deoxy-beta-N-glycopeptides.

A novel reagent system comprising Me(3)SiN(3) and 20 mol % of Me(3)SiONO(2) permits conversion of glycals to 1-azido 2-deoxy sugars in one step in fair to good yields. Galactals offer higher stereoselectivities than do the glucals. Reduction of the azide group with Ph(3)P-H(2)O to amino functionality followed by coupling with amino acids leads to the synthesis of novel 2-deoxy-beta-N-glycopeptides irrespective of the geometry of initial azido sugars. Using this protocol, a new gamma-sugar amino acid derivative is also procured.

Azides↗