Azide

Design, synthesis, and unraveling the antibacterial and antibiofilm potential of 2-azidobenzothiazoles: insights from a comprehensive in vitro study

The present study reports the synthesis of 2-azidobenzothiazoles from substituted 2-aminobenzothiazoles using sodium nitrite and sodium azide under mild conditions. All the synthesized compounds were examined for their antibacterial activity against Gram (+) bacteria, Staphylococcus aureus (ATCC 25923), Enterococcus faecalis (ATCC 51299), Bacillus cereus (ATCC 10876) and Gram (-) bacteria, Escherichia coli (ATCC 10536), Pseudomonas aeruginosa (ATCC 10145), Klebsiella pneumonia (ATCC BAA-2146)and clinical isolates of Gram (+) Methicillin Resistant S. aureus (MRSA) and Multi Drug Resistant E. coli. The Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values by broth dilution method revealed that compound 2d exhibited significant antibacterial potential against E. faecalis and S. aureus with MIC of 8 μg/mL, while other synthesized compounds had only moderate effects against all the tested species. The compound significantly inhibited the biofilm formation of the bacterial strains below its MIC. The selective cytotoxicity of Compound 2d towards bacterial cells was evidenced on extended exposure of Human Embryonic Kidney-293 cell line to higher concentrations of the compound. Hence, the present study confirmed that compound 2d can be a potential drug candidate for future development as an antibacterial drug.

Frequency and spectrum of M2 mutants and genetic variability in cyto-agronomic characteristics of fenugreek induced by caffeine and sodium azide

Trigonella foenum graecum L. (Fenugreek) is a valuable medicinal plant cultivated for decades for its therapeutic characteristics. Still no pronounced improvement concerning wild form was accomplished as it is a self-pollinating crop. Induced mutagenesis is encouraged as a remarkable tool on this plant to circumvent the genetic bottleneck of cultivated germplasms. As a result, novel allelomorphic combinations for short-term agronomic attributes were developed. Fenugreek cultivar Pusa Early Bunching, selected for the present experiment, was mutagenized with five doses (0.2%, 0.4%, 0.6%, 0.8%, and 1.0%) of caffeine and sodium azide (SA) to evaluate its impact on the qualitative and quantitative traits of M₁ and M₂ generation conducted in a Complete Randomized Block Design (CRBD), replicated five times during 2019-2020 and 2020-2021, respectively. The frequency of induced phenotypic variations was assessed in M₂ progenies, resulting in the identification and isolation of a broad spectrum of mutants with altered phenotypes. Mutagenic effectiveness and efficiency were found to be maximum at lower concentrations of the mutagen treatments and highest in SA, followed by caffeine. Various morphological mutants with modified characters were observed at different concentrations in M₂ generation. The spectrum of mutations was wider in SA than in caffeine, as caffeine produced 51 while SA produced 54 individual mutants under seven major categories. The maximum frequency of morphological mutants was associated with leaf, followed by plant size, plant growth habit, pod, seed size, seed shape, and seed color. Morphological and structural variations in the guard cells of stomata and seeds were observed through scanning electron microscopy. The variations created in the economically important traits may enrich the genetic diversity of this plant species. Moreover, these morphological mutants may serve as a source of elite genes in further breeding programs of fenugreek.

Potent mutagenicity of an azide, 3-azido-1,2-propanediol, in human TK6 cells

Sodium azide is a strong mutagen that has been successfully employed in mutation breeding of crop plants. In biological systems, it is metabolically converted to the proximate mutagen azidoalanine, which requires further bioactivation to a putative ultimate mutagen that remains elusive. The nature of the DNA modifications induced by azides leading to mutations is also unknown. Other mutagenic organic azido compounds seem to share the same bioactivation pathway to the ultimate mutagenic species as they induce point mutations dependent on the same DNA repair pathways. We investigated mutations induced by the representative mutagen 3-azido-1,2-propanediol (azidoglycerol, AZG) in the human TK6 cell line. Until now, azides have been considered to be non-mutagens and non-carcinogens in mammals, including humans, as judged only by the conventional clastogenicity chromosomal aberration types of bioassays. Here, we show the potent mutagenicity of AZG in cultured human cells, comparable to alkylating agents such as methyl methanesulfonate at concentrations with similar lethality. The potent ability of an organic azide to induce base substitutions in a mammalian system raises an alert with respect to human exposure to organic and inorganic azido compounds.

Updates and Original Case Studies Focused on the NMR-Linked Metabolomics Analysis of Human Oral Fluids Part I: Emerging Platforms and Perspectives

1H NMR-based metabolomics analysis of human saliva, other oral fluids, and/or tissue biopsies serves as a valuable technique for the exploration of metabolic processes, and when associated with ’state-of-the-art’ multivariate (MV) statistical analysis strategies, provides a powerful means of examining the identification of characteristic metabolite patterns, which may serve to differentiate between patients with oral health conditions (e.g., periodontitis, dental caries, and oral cancers) and age-matched heathy controls. This approach may also be employed to explore such discriminatory signatures in the salivary 1H NMR profiles of patients with systemic diseases, and to date, these have included diabetes, Sjörgen’s syndrome, cancers, neurological conditions such as Alzheimer’s disease, and viral infections. However, such investigations are complicated in view of quite a large number of serious inconsistencies between the different studies performed by independent research groups globally; these include differing protocols and routes for saliva sample collection (e.g., stimulated versus unstimulated samples), their timings (particularly the oral activity abstention period involved, which may range from one to 12 h or more), and methods for sample transport, storage, and preparation for NMR analysis, not to mention a very wide variety of demographic variables that may influence salivary metabolite concentrations, notably the age, gender, ethnic origin, salivary flow-rate, lifestyles, diets, and smoking status of participant donors, together with their exposure to any other possible convoluting environmental factors. In view of the explosive increase in reported salivary metabolomics investigations, in this update, we critically review a wide range of critical considerations for the successful performance of such experiments. These include the nature, composite sources, and biomolecular status of human saliva samples; the merits of these samples as media for the screening of disease biomarkers, notably their facile, unsupervised collection; and the different classes of such metabolomics investigations possible. Also encompassed is an account of the history of NMR-based salivary metabolomics; our recommended regimens for the collection, transport, and storage of saliva samples, along with their preparation for NMR analysis; frequently employed pulse sequences for the NMR analysis of these samples; the supreme resonance assignment benefits offered by homo- and heteronuclear two-dimensional NMR techniques; deliberations regarding salivary biomolecule quantification approaches employed for such studies, including the preprocessing and bucketing of multianalyte salivary NMR spectra, and the normalization, transformation, and scaling of datasets therefrom; salivary phenotype analysis, featuring the segregation of a range of different metabolites into ‘pools’ grouped according to their potential physiological sources; and lastly, future prospects afforded by the applications of LF benchtop NMR spectrometers for direct evaluations of the oral or systemic health status of patients at clinical ‘point-of-contact’ sites, e.g., dental surgeries. This commentary is then concluded with appropriate recommendations for the conduct of future salivary metabolomics studies. Also included are two original case studies featuring investigations of (1) the 1H NMR resonance line-widths of selected biomolecules and their possible dependence on biomacromolecular binding equilibria, and (2) the combined univariate (UV) and MV analysis of saliva specimens collected from a large group of healthy control participants in order to potentially delineate the possible origins of biomolecules therein, particularly host- versus oral microbiome-derived sources. In a follow-up publication, Part II of this series, we conduct censorious reviews of reported observations acquired from a diversity of salivary metabolomics investigations performed to evaluate both localized oral and non-oral diseases. Perplexing problems encountered with these again include those arising from sample collection and preparation protocols, along with 1H NMR spectral misassignments.

Screen-printed Microsensors Using Polyoctyl-thiophene (POT) Conducting Polymer As Solid Transducer for Ultratrace Determination of Azides

Two novel all-solid-state potentiometric sensors for the determination of azide ion are prepared and described here for the first time. The sensors are based on the use of iron II-phthalocyanine (Fe-PC) neutral carrier complex and nitron-azide ion-pair complex (Nit-N₃⁻) as active recognition selective receptors, tetradodecylammonium tetrakis(4-chlorophenyl) borate (ETH 500) as lipophilic cationic additives and poly(octylthiophene) (POT) as the solid contact material on carbon screen-printed devices made from a ceramic substrate. The solid-contact material (POT) is placed on a carbon substrate (2 mm diameter) by drop-casting, followed, after drying, by coating with a plasticized PVC membrane containing the recognition sensing complexes. Over the pH range 6-9, the sensors display fast (< 10 s), linear potentiometric response for 1.0 × 10⁻²–1.0 × 10⁻⁷ M azide with low detection limit of 1.0 × 10⁻⁷ and 7.7 × 10⁻⁸ M (i.e., 6.2–4.8 ng/ml) for Fe-PC/POT/and Nit-N₃⁻/POT based sensors, respectively. The high potential stability and sensitivity of the proposed sensors are confirmed by electrochemical impedance spectroscopy (EIS) and constant-current chronopotentiometry measurement techniques. Strong membrane adhesion and absence of delamination of the membrane, due to possible formation of a water film between the recognition membranes and the electron conductor are also verified. The proposed sensors are successfully applied for azide quantification in synthetic primer mixture samples. Advantages offered by these sensors are the robustness, ease of fabrication, simple operation, stable potential response, high selectivity, good sensitivity and low cost.

A unique benzimidazole-naphthalene hybrid molecule for independent detection of Zn2+ and N3- ions: Experimental and theoretical investigations

Single crystal X-ray structurally characterized benzimidazole-naphthalene hybrid (NABI) functions as a unique dual analyte sensor that can detect Zn²⁺ cation and N₃^- anion independently. The NABI forms chelate with Zn²⁺ to inhibit internal charge transfer (ICT) and CHN isomerisation resulting chelation enhanced fluorescence (CHEF). On the other hand, the sensing of N₃^- is based on formation of supramolecular H-bonded rigid assembly. The association constant of NABI for Zn²⁺ and N₃^- ions are 19 × 10⁴ M^-1 and 11 × 10² M^-1, respectively. Corresponding limit of detections (LOD) are 6.85 × 10^-8 and 1.82 × 10^-7 M, respectively. NABI efficiently detects intracellular Zn²⁺ and N₃^- ions with no cytotoxicity on J774A.1cells under fluorescence microscope. DFT studies unlock underlying spectroscopic properties of free NABI and Zn²⁺/N₃^- bound forms.

A curcumin derived probe for colorimetric detection of azide ions in water

A curcumin based probe (CUC-P) having an active alkyne moiety has been synthesised for selective detection of azide (N₃⁻) ions in aqueous medium.

A metal-free turn-on fluorescent probe for the fast and sensitive detection of inorganic azides

Sodium azide is toxic and widely used in agricultural, commercial products, and research laboratories. Thus it is of a significant environmental concern and there is a need for the development of a rapid detection method. A fluorogenic dibenzylcyclooctyne derivative (Fl-DIBO) is herein described as a fluorescent probe for the rapid detection of inorganic azide via Strain-Promoted Azide-Alkyne Cycloaddition (SPAAC). Fl-DIBO was found to be highly selective toward NaN3 in comparison to other common anions with good sensitivity and detection limit of 10μM.

New potentiometric transducer based on a Mn(II) [2-formylquinoline thiosemicarbazone] complex for static and hydrodynamic assessment of azides

A new potentiometric transducer for selective recognition of azide is characterized and developed. The PVC plasticized based sensor incorporates Mn(II) [2-formylquinoline thiosemicarbazone] complex in the presence of tri dodecyl methyl ammonium chloride (TDMAC) as a lipophilic cationic additive. The sensor displayed a near-Nernstian response for azide over 1.0×10(-2)-1.0×10(-5) mol L(-1), with an anionic slope of -55.8±0.6 mV decade(-1) and lower limit of detection 0.34 µg mL(-1). The sensor was pH independent in the range 5.5-9 and presented good selectivity features towards several inorganic anions, and it is easily used in a flow injection system and compared with a tubular detector. The intrinsic characteristics of the detector in a low dispersion manifold were determined and compared with data obtained under a hydrodynamic mode of operation. This simple and inexpensive automation, with a good potentiometric detector, enabled the analysis of ~33 samples h(-1) without requiring pre-treatment procedures. The proposed method is also applied to the analysis of trace levels of azide in primer mixtures. Significantly improved accuracy, precision, response time, stability and selectivity were offered by these simple and cost-effective potentiometric sensor compared with other standard techniques. The method has the requisite accuracy, sensitivity and precision to determine azide ions.

Permeabilization and inhibition of the germination of spores of Aspergillus niger for gluconic acid production from glucose

In this study, the role of citral to permeabilize the spores of Aspergillus niger and replace sodium azide in the bioconversion medium was studied. Further, characterization of glucose oxidase of spores was carried out by exposing both permeabilized and unpermeabilized spores to different pressures (1, 2, 2.7 kb) and temperatures (60, 70, 80, 90 degrees C). Unpermeabilized spores after exposure to high temperatures were permeabilized by freezing before using as catalyst in the bioconversion reaction. Results showed that citral permeabilized the spores and could inhibit spore germination in the bioconversion medium. Rate of reaction was significantly increased from 1.5 to 4.35 g/Lh which was higher than the commercial glucose oxidase 2g/Lh). Glucose oxidase activity of A. niger was resistant to pressure. However, pressure treatment could not permeabilize them. Behaviour of fresh and permeabilized spores to temperature varied significantly. Glucose oxidase activity of fresh spores exposed to high temperature was unaffected at 70 degrees C till 15 min and 84% of relative activity was retained even after 1h at 70 degrees C while permeabilized spore got inactivated at 70 degrees C for 15 min, which followed the same pattern as commercial glucose oxidase. Cellular membrane integrity was lost due to permeabilization by freezing which resulted in heat-inactivation of glucose oxidase when spores were permeabilized before heat treatment. Thus, glucose oxidase of spore remains heat stable when unpermeabilized and active while permeabilized and its reaction rate is higher than the commercial glucose oxidase.

TILLMore, a resource for the discovery of chemically induced mutants in barley

A sodium azide-mutagenized population of barley (cv. 'Morex') was developed and utilized to identify mutants at target genes using the 'targeting induced local lesions in genomes' (TILLING) procedure. Screening for mutations at four agronomically important genes (HvCO1, Rpg1, eIF4E and NR) identified a total of 22 new mutant alleles, equivalent to the extrapolated rate of one mutation every 374 kb. All mutations except one were G/C to A/T transitions and several (approximately 68%) implied a change in protein amino acid sequence and therefore a possible effect on phenotype. The high rate of mutation detected through TILLING is in keeping with the high frequency (32.7%) of variant phenotypes observed amongst the M(3) families. Our results indicate the feasibility of using this resource for both reverse and forward genetics approaches to investigate gene function in barley and related crops.

Human health effects of sodium azide exposure: a literature review and analysis

Sodium azide, used mainly as a preservative in aqueous laboratory reagents and biologic fluids and as a fuel in automobile airbag gas generants, has caused deaths for decades. Its exposure potential for the general population increases as the use of airbags increase. In order to characterize the known health effects of sodium azide in humans and the circumstances of their exposure, the authors conducted a systematic review of the literature from 1927 to 2002 on human exposure to sodium azide and its health effects. The most commonly reported health effect from azide exposure is hypotension, almost independent of route of exposure. Most industrial exposures are by inhalation. Most laboratory exposures or suicide attempts are by ingestion. Most of the reported cases involved persons working in laboratories. The time between exposure and detection of hypotension can predict outcome. Fatal doses occur with exposures of >or=700 mg (10 mg/kg). Nonlethal doses ranged from 0.3 to 150 mg (0.004 to 2 mg/kg). Onset of hypotension within minutes or in less than an hour is indicative of a pharmacological response and a benign course. Hypotension with late onset (>1 hour) constitutes an ominous sign for death. All individuals with hypotension for more than an hour died. Additional health effects included mild complaints of nausea, vomiting, diarrhea, headache, dizziness, temporary loss of vision, palpitation, dyspnea, or temporary loss of consciousness or mental status decrease. More severe symptoms and signs included marked decreased mental status, seizure, coma, arrhythmia, tachypnea, pulmonary edema, metabolic acidosis, and cardiorespiratory arrest. The signs and symptoms from lower exposures (<700 mg) are physiological responses at the vascular level and those at or above are toxicological responses at the metabolic level. There is no specific antidote for sodium azide intoxication. Recommended preventive measures for sodium azide exposure consist of education of people at high risk, such as laboratory workers, regarding its chemical properties and toxicity, better labeling of products containing sodium azide, and strict enforcement of laboratory regulations and access control.

Chalcone isomerase gene from rice (Oryza sativa) and barley (Hordeum vulgare): physical, genetic and mutation mapping

The barley and rice chalcone flavonone isomerase (Cfi) genes were isolated and identified by homology to the maize Cfi gene. Structure analysis indicated high similarity except that the barley gene lacked intron 3. The maize Cfi gene has been mapped to three loci, but only a single locus was detected in barley and rice. This explains the lack of observed mutants in maize while a single locus anthocyanin-less 30 (ant30), with four alleles ant30-245, ant30-310, ant30-272 and ant30-287 has been described in barley. Based on biochemical analysis it has been suggested that these mutants are in the Cfi gene resulting in absence of anthocyanin. In order to provide molecular evidence for or against this hypothesis we sequenced the four ant30 alleles and compared them to their respective wild-type alleles. The three sodium azide induced mutants ant30-245, ant30-272 and ant30-287 showed single base changes resulting in two non-sense and one mis-sense mutations affecting the protein function. The 1-nitroso-5,6-dihydrouracil induced mutant ant30-310 had one base substitution and a 25 bp deletion. These observations are in accordance with the conclusion that the ant30 phenotype is caused by mutations in the Cfi gene. The nature of the mutants induced is in line with the proposed mechanism of action for the mutagens used.

Mutagenicity of sodium azide and its metabolite azidoalanine in Drosophila melanogaster

The mutagenic and toxic activities of sodium azide (NaN(3) ) and its organic metabolite L-azidoalanine [N(3)-CH(2)-CH(NH)(2)-COOH] were examined in the different stages of spermatogenesis in Drosophila melanogaster. Both azide and azidoalanine were toxic to the injected males, but azidoalanine was significantly less toxic than sodium azide. Following the injection with 0.2 microl of these compounds in the hemocoel of young adult wild-type males, the minimum concentrations of these compounds with complete toxic effects (zero survival) were 40 mM sodium azide and 160 mM azidoalanine. Sex-linked recessive lethals were scored by the Muller-5 method in three successive broods, representing sperms (brood A), spermatids (brood B), and a compiled group of meiotic and premeiotic germ cell stages (brood C). The results provide strong experimental evidence that azidoalanine is significantly (p<0.01) mutagenic to all stages of spermatogenesis in Drosophila melanogaster. Sodium azide, however, was not significantly (p>0.05) mutagenic and did not increase the rate of sex-linked recessive lethals over those produced by the control group injected with 0.45% NaCl. These results indicate the requirement of metabolic activation of azide in Drosophila as a prerequisite for its mutagenic effects.

Sodium azide induces mitotic recombination in Drosophila melanogaster larvae

Sodium azide (NaN3), a potent mutagen for bacteria and barley, was tested for somatic mutation and mitotic recombination induction in wing imaginal disc cells of Drosophila melanogaster. Comparisons were made among inversion-free flr3/mwh, inversion-heterozygous TM3, Ser/mwh, and inversion-free, high bioactivation OR(R), flr3/mwh flies. Third instar larvae were exposed chronically for 48 h to sodium azide at 0.5, 0.63, 0.75, 0.88 and 1.0 mM. The frequencies of spots per wing obtained in the three kinds of progeny scored were compared. In inversion-free flies, sodium azide induced large single and total spots at all concentrations tested, and small single and twin spots at 0.75 mM and higher concentrations. In contrast, it failed to increase the frequency of small and large single spots in inversion-heterozygous flies. In high bioactivation flies (which are inversion-free), sodium azide increased the frequency of large single spots at 0.63, 0.88 and 1.0 mM and the frequency of total spots at 0.63 mM. From the absence of genotoxic activity observed in inversion-heterozygous flies it is concluded that sodium azide induces exclusively mitotic recombination in wing somatic cells of Drosophila melanogaster larvae after chronic exposure. This recombinogenic activity is reduced in the presence of high bioactivation capacity.

Vicia faba chromosomal aberration assay

A collaborative study involving laboratories in six countries was initiated under the sponsorship of the International Programme on Chemical Safety (IPCS) to determine the sensitivity, efficiency and reliability of the Vicia faba root tip meristem chromosomal aberration assay using a standardized protocol. The six laboratories that participated in this study were located in the Slovak Republic, India, Japan, Poland, Sweden and the USA. All laboratories adhered to a standardized protocol for the Vicia faba chromosomal aberration assay. Four coded chemicals, azidoglycerol (AG), N-methyl-N-nitrosourea (MNU), sodium azide (NaN3) and maleic hydrazide (MH) were tested with the Vicia faba chromosomal aberration assay. Of the four chemicals, three (MH, AG and MNU) were found to be clastogenic and gave a concentration related response. However, the results of NaN3 were equivocal which might be explained by the stability of NaN3. The conclusions from this study suggest that the Vicia faba chromosomal aberration bioassay is an efficient and reliable short-term bioassay for the rapid screening of chemicals for clastogenicity.

Effects of deuterium labeling on azido amino acid mutagenicity in Salmonella typhimurium

The mutagenic effects of azide (N3-) anion in bacterial test systems require the formation of the novel mutagenic metabolite, 3-azido-L-alanine (AZAL). Although the mechanism of AZAL-induced mutagenicity is unknown, subsequent bioactivation of this metabolite appears likely. Earlier studies have shown that other azide-containing amino acids are mutagenic as well. In fact, the mutagenic potency of the synthetic AZAL homologue, L-2-amino-4-azidobutanoic acid (HomoAZAL), was several times that of AZAL. To gain insight into the biochemical processing and mutagenicity of azido amino acids in Salmonella typhimurium, several specifically deuterium-labeled azido amino acids have been prepared and tested for mutagenic potency. In addition, the effect of (aminooxy)acetic acid (AOA) (a potent inhibitor of pyridoxal-dependent processes) on AZAL-induced mutagenesis was examined. The results showed that 2-deuterium substitution of AZAL resulted in a slight increase in mutagenic potency, while AOA treatment resulted in no change in AZAL potency. Taken together these findings did not support the involvement of pyridoxal-dependent processes in AZAL bioactivation. In contrast, deuterium substitution adjacent to the azide group in HomoAZAL and 5-azido-L-norvaline (N3-Norval) resulted in a large decrease in mutagenic potency when compared to the non-deuterium labeled compounds. These observations are consistent with a bioactivation mechanism involving rate-limiting C-H bond cleavage in the formation of the ultimate mutagen. Moreover, this effect of deuterium labeling points to processing of the azide-containing side chain as a key feature in the mutagenic activation mechanism.

Precision mapping of quantitative trait loci

Adequate separation of effects of possible multiple linked quantitative trait loci (QTLs) on mapping QTLs is the key to increasing the precision of QTL mapping. A new method of QTL mapping is proposed and analyzed in this paper by combining interval mapping with multiple regression. The basis of the proposed method is an interval test in which the test statistic on a marker interval is made to be unaffected by QTLs located outside a defined interval. This is achieved by fitting other genetic markers in the statistical model as a control when performing interval mapping. Compared with the current QTL mapping method (i.e., the interval mapping method which uses a pair or two pairs of markers for mapping QTLs), this method has several advantages. (1) By confining the test to one region at a time, it reduces a multiple dimensional search problem (for multiple QTLs) to a one dimensional search problem. (2) By conditioning linked markers in the test, the sensitivity of the test statistic to the position of individual QTLs is increased, and the precision of QTL mapping can be improved. (3) By selectively and simultaneously using other markers in the analysis, the efficiency of QTL mapping can be also improved. The behavior of the test statistic under the null hypothesis and appropriate critical value of the test statistic for an overall test in a genome are discussed and analyzed. A simulation study of QTL mapping is also presented which illustrates the utility, properties, advantages and disadvantages of the method.

Sodium azide mutagenesis: preferential generation of A.T-->G.C transitions in the barley Ant18 gene

The molecular basis for the absence of anthocyanins and proanthocyanidins in four independent sodium azide-induced ant18 mutants of barley was examined by sequencing the gene encoding dihydroflavonol 4-reductase in these mutants. Sodium azide generated 21 base substitutions, which corresponds to 0.17% of the 12,704 nucleotides sequenced. Of the substitutions, 86% were nucleotide transitions, and 14% were transversions. A.T-->G.C base pair transitions were about 3 times more frequent than G.C-->A.T transitions. No deletions or mutation hot spots were found. The absence of dihydroflavonol 4-reductase activity in ant18-159, ant18-162, and ant18-164 plants is caused by missense mutations in the respective genes. By using microprojectile bombardment, a plasmid harboring the wild-type Ant18 gene was introduced into ant18-161 mutant cells and resulted in the development of anthocyanin pigmentation, which demonstrates that the mutation is corrected by expression of the introduced gene. On the other hand, a plasmid derivative with the two ant18-161-specific base transitions at the 5' splice site of intron 3 prevented complementation. It is concluded that the absence of detectable mRNA for dihydroflavonol 4-reductase in ant18-161 cells is due to the mutations in the pre-mRNA splice donor site.

Mutagenic activity of 6-azido deoxyhexoses and azido alcohols in Salmonella typhimurium and its inhibition by a structure-similar carbon source in the medium

6-Azido-6-deoxy (AZd) derivatives of D-glucose, D-mannose, D-altrose, D-allose, L-idose, D-galactose, D-galactonic acid and D-galactitol, 3-azido-1,2-propanediol (azidoglycerol), 3,1-diazido-2-propanol (diazidoglycerol) and (at much higher doses) 2-azidoethanol were mutagenic in Salmonella typhimurium strains TA100 and TA1535. The mutagenic response was similar to that induced by sodium azide, i.e., the azido compounds failed to induce mutations in strain TA98, and mutagenesis was independent of plasmid pKM101, and independent of external activation. The specific mutagenicity (his+ rev/mmole) of AZd-glucose and AZd-galactose was decreased with increasing concentrations of D-glucose or D-galactose in the minimal agar medium and enhanced 100-fold or more when 0.2% citrate rather than 0.2% glucose served as the carbon source in the medium. Similarly, the mutagenic efficiency of azidoglycerol was inhibited by glycerol but not by D-glucose or D-galactose; however, the mutagenicity of sodium azide was not influenced by any of these carbon sources in the medium. The inhibition of the mutagenic action of azido hexoses and azido alcohols by non-azido structural analogs is assumed to reside in competition in transmembrane transport or for the metabolic pathways.

Structure of the Hordeum vulgare gene encoding dihydroflavonol-4-reductase and molecular analysis of ant18 mutants blocked in flavonoid synthesis

A full-length cDNA clone encoding barley dihydroflavonol-4-reductase was isolated from a kernel-specific cDNA library by screening with the cDNA of the structural gene (A1) for this enzyme from maize. Subsequently, the gene corresponding to the barley dihydroflavonol-4-reductase cDNA was cloned and sequenced. The gene contains three introns at the same positions as in the Zea mays gene, corresponding to the positions of the first three of the five introns present in the genes of Petunia hybrida and Antirrhinum majus. In vitro transcription and translation of the Hordeum vulgare cDNA clone yielded a protein which converts dihydroquercetin into 2,3-trans-3,4-cis-leucocyanidin with NADPH as cofactor. The protein has a deduced amino acid sequence of 354 residues and a molecular weight of 38,400 daltons. Dihydroflavonol reductases of barley, maize, petunia and snapdragon are highly polymorphic in the NH2- and C-terminal parts of the polypeptide chain while a central region of 324 residues contains 51% identical amino acids. This identity increases to 81% when only the barley and maize enzymes are compared. Recessive mutants in the Ant18 gene tested so far lack dihydroflavonol-4-reductase activity and accumulate small amounts of dihydroquercetin but have retained activity for at least two other enzymes in the flavonoid pathway. In testa-pericarp tissue of mutants ant18-159, ant18-162 and ant18-164, wild-type levels of steady state mRNA for dihydroflavonol reductase have been measured, while mRNA for this enzyme is not transcribed in mutant ant18-161. These data are consistent with the proposal that the Ant18 locus carries the structural gene for dihydroflavonol-4-reductase of barley.

Poisonings in laboratory personnel and health care professionals

A case report of an unresponsive chemist presenting to the emergency department is presented; in retrospect, the patient was discovered to have intentionally ingested cyanide. A review of literature regarding ingestions in laboratory and health care personnel reveals five common points encountered in these personnel: barbiturates, carbon monoxide, cyanide, azides, and methemoglobin-inducing chemicals. Key diagnostic findings, in the absence of history of exposure, are discussed for these five agents.

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.

Differential metabolism of sodium azide in maize callus and germinating embryos

Sodium azide is a potent mutagen of maize (Zea mays L.) kernels that may have potential as a point mutagen for inducing biochemical mutations in maize tissue cultures. Azide mutagenicity was evaluated in friable, embryogenic maize callus and a nonregenerable maize suspension culture by determining the number of resistant variant cell lines able to grow on media containing inhibitory concentrations of lysine plus threonine (LT). The number of LT-resistant variants selected from either culture type did not increase in response to azide treatment. In addition, there was no increase in somatic mutations in more than 100 plants regenerated from azide treated LT-resistant lines. The levels of mutagenic metabolite of azide (presumably azidoalanine), were determined by bioassay in the two azide-treated maize callus types and compared to levels of mutagenic metabolite in embryos isolated from azide-treated kernels. The two types of maize tissue cultures and isolated embryos contained similar levels of mutagenic metabolite 4 h after azide treatment indicating similar uptake and conversion of azide to mutagenic metabolite in the three tissues. Mutagenic metabolite in azide-treated embryos did not significantly decrease after 40 h. However, mutagenic metabolite levels in both azide-treated tissue cultures decreased to near background levels within 20 h providing evidence for rapid metabolism of the azide mutagenic metabolite. The lack of evidence for azide mutagenicity in maize callus and its known potent mutagenicity in kernels appears to be associated with specific differences in azide metabolism between callus tissues and kernel embryos.

Azidoalanine mutagenicity in Salmonella: effect of homologation and alpha-methyl substitution

Azide mutagenicity in susceptible non-mammalian systems involves the requisite formation of L-azidoalanine, a novel mutagenic amino acid. The biochemical mechanism(s) of azidoalanine-induced mutagenesis, however, is not known. Previous studies of the structural requirements for azidoalanine mutagenicity suggested the importance of free L-amino acid character, and that bioactivation of azidoalanine to the ultimate mutagenic species is required. To gain more insight into possible enzymatic processing, the alpha-methyl analogue, alpha-methyl-azidoalanine, and the homologue, 2-amino-4-azidobutanoic acid, were synthesized and tested for mutagenic potency in Salmonella typhimurium strain TA1530. In addition, azidoacetic acid, a possible azidoalanine metabolite, was prepared and tested. The results show that alpha-methyl substitution effectively blocks the mutagenic effects of azidoalanine with alpha-methyl-azidoalanine being nearly devoid of mutagenic activity. In contrast, homologation of azidoalanine to yield 2-amino-4-azidobutanoic acid produces a marked increase in molar mutagenic potency. As with azidoalanine, the mutagenic activity of this homologue is associated with the L-isomer. Azidoacetic acid, however, was only very weakly mutagenic when tested as either the free acid or ethyl ester. This low mutagenic potency may indicate that bioactivation does not involve the entry of azide-containing azidoalanine catabolite into the Kreb's cycle. The high potency of 2-amino-4-azidobutanoic acid may be indicative of more efficient bioactivation and/or greater intrinsic activity. Importantly, the latter finding clearly shows that potent azido-amino acid mutagenicity is not limited to azidoalanine alone.

Metabolic activation of the mutagen azide in biological systems

Inorganic azide (N3-) mutagenicity is mediated through a metabolically synthesized organic azide, L-azidoalanine (N3-CH2-CH(-NH2)-COOH). L-Azidoalanine appears to be formed by the action of O-acetylserine (thiol)-Lyase (EC 4.2.99.8) using O-acetylserine and azide as substrates. In both plants and bacteria tested, azide substitutes for the natural substrate sulfide (S2-) in this reaction. Azide (L-azidoalanine) mutagenesis is highly attenuated by a deficiency in the excision of UV-like DNA damage (uvr-). Thus a premutation lesion recognizable by the bacterial excision-repair enzymes must be formed. Mutagenesis appears to proceed from this by 'direct mispairing' pathway. Azide (L-azidoalanine) mutagenicity is highly specific and involves a stereoselective process, but the molecular nature of the specificity has not been determined.

Mutagenic activity of promutagens in plants: indirect evidence of their activation

This review summarizes data concerning mutagenic activity of promutagens in various plant in vivo assays. These data are compared with the present knowledge about the metabolism of xenobiotics and activation of promutagens in plants obtained by biochemical studies and by the separation of the activation process from the genetic endpoints assayed for the mutagenicity. The article documents a differential response of plant species in the endogenous transforming of various classes of promutagens into mutagens. Attention is devoted to the following types of promutagens: nitrosamines, polycyclic aromatic hydrocarbons and aromatic amines, aflatoxins, pyrrolizidine alkaloids, diallate, styrene, vinylchloride, ethanol, cycasin, nitrofurans, sodium azide, s-triazine herbicides, 1,2-dibromoethane and maleic hydrazide.

Effects of sodium azide on sea urchin embryos and gametes

Sodium azide (SA) was tested on sea urchin embryos and gametes (Paracentrotus lividus). Developing embryos were exposed to SA (10(-6) to 10(-3) M) up to pluteus larval stage, or for shorter intervals before or after hatching. Developmental defects in SA-exposed embryos consisted mainly of gut abnormalities, without any detectable differences between pre- or post-hatch-exposed embryos. SA-induced damage to gut was exerted during gastrulation, as evident by lectin binding of extracellular matrix. No mitotic damage was observed in SA-exposed embryos, nor could pH-related variations be detected in SA-induced embryotoxicity at pH's ranging from 8 to 6. Concurrently, no effect ensued in the exposure of unfertilized eggs to SA (10(-5) to 10(-2) M) both in terms of fertilization success and of offspring quality. When sperm were suspended in filtered seawater at pH's ranging from 8 to 6, and SA levels ranging from 10(-5) to 10(-2) M, fertilization success of SA-exposed sperm appeared to be modulated by pH, by displaying three distinct dose-response trends at pH 8, 7, or 6. The consequences of sperm pretreatment on offspring quality failed to show any significant SA-induced changes on larval malformations or mortality, while confirming the previously reported pH-induced increase of developmental defects in the offspring of acid-exposed sperm (Pagano et al.: Teratogenesis Carcinogen Mutagen 5:113-121, 1985).

Suicidal sodium azide ingestion

Sodium azide (NaN3) is a highly reactive, toxic, widely used chemical. Although industrial exposure is common, fatal ingestion is rare. We describe the case of a 30-year-old man who ingested 15 to 20 g of sodium azide. He became comatose within two hours and eventually expired from a combination of acidosis, respiratory depression, and ventricular fibrillation. In sufficient doses, sodium azide is rapidly fatal and there is no effective treatment.

Interaction of the mutagenic metabolite of sodium azide, synthesized in vitro, with DNA of barley embryos

The in vitro synthesized sodium azide mutagenic metabolite (azidoalanine) produced single-strand breaks and proteinase K-sensitive sites in isolated, germinating barley embryos. In contrast with sodium azide, the efficiency of DNA damage induction was lower, and both types of DNA lesions were totally or partially repaired in the course of subsequent 24 h incubation of the embryos. The mutagenic azide metabolite did not inhibit DNA replication, while azide did so even at doses which are not highly mutagenic. The metabolite labelled with 14C at the amino acid residue was taken up with a similar efficiency both into barley embryos germinating for 2 days and into cells of Salmonella typhimurium TA100. The majority of the radioactivity was incorporated into proteins, less into RNA and a negligible amount into DNA.

Investigation of partial sterility in advanced generation, sodium azide-induced lines of spring barley

The partial sterility found in several advanced generation, sodium azide-induced lines of spring barley (Hordeum vulgare L.) was investigated. Plants of mutant lines were reciprocally crossed with plants of their untreated mother lines. Spike sterility was measured in the selfed offspring of the plants crossed and in F1 and F2 progeny. Pollen sterility and endosperm development were analyzed in the selfed offspring of the plants crossed. Results indicated that the sterility was inherited in the mutant lines and was not caused by translocations, inversions, endosperm lethals, embryo-endosperm lethals, or major gene mutations. Furthermore, the sterility was not cytoplasmically inherited, and was essentially eliminated in the F1 and F2 of crosses between partially sterile lines and their fertile parents. Results suggest that the sterility may be caused by an environmental interaction with deleterious, homozygous recessive, minor gene mutations that were in the heterozygous condition when the mutant lines were originally selected.

High mutagenic activity of 3-azido-1,2-propanediol (azidoglycerol, AG) in strain D7 of Saccharomyces cerevisiae

3-Azido-1,2-propanediol (azidoglycerol, AG) showed a high mutagenicity in strain D7 of Saccharomyces cerevisiae. At 5 mM it increased the spontaneous frequency of isoleucine revertants 3500 times and the frequency of gene convertants 3000 times during 24 h of growth, reducing the growth rate to 30%. In non-growth conditions, treatment with 150 mM of AG for 3 h reduced cell survival to 60% and enhanced the frequency of isoleucine revertants 490 times and tryptophan-independent convertants 50 times. At equal survival levels, AG was found to be 3000-fold more mutagenic and 200-fold more convertogenic than sodium azide.

Synthesis and enantioselective mutagenicity of azidoalanine in Salmonella typhimurium

Azide mutagenicity involves the requisite formation of the putative novel aminoacid metabolite, beta-azidoalanine. The role of this metabolite, however, is unclear. In order to confirm the identity of this metabolite and provide additional information on possible stereochemical requirements for mutagenicity, authentic racemic and L-azidoalanine were synthesized by an unambiguous route and tested for mutagenicity in Salmonella typhimurium TA100, TA1535, hisG46 and Escherichia coli WP2-. A marked antipodal potency ratio was observed in strains TA100 and TA1535 when racemic and L-azidoalanine were compared. The mutagenic activity resided primarily in the L-isomer. The molar potency of L-azidoalanine in TA100 and TA1535 was nearly identical to that of azide. The lack of mutagenic response for racemic or L-azidoalanine in hisG46 and E. coli WP2- was like that reported for azide and is consistent with similar modes of action for these agents.

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.