The methods for detecting carcinogens and mutagens with the Salmonella mutagenicity test were described previously (Ames et al., 1975b). The present paper is a revision of the methods. Two new tester strains, a frameshift strain (TA97) and a strain carrying an ochre mutation on a multicopy plasmid (TA102), are added to the standard tester set. TA97 replaces TA1537. TA1535 and TA1538 are removed from the recommended set but can be retained at the option of the investigator. TA98 and TA100 are retained. We discuss other special purpose strains and present some minor changes in procedure, principally in the growth, storage, and preservation of the tester strains. Two substitutions are made in diagnostic mutagens to eliminate MNNG and 9-aminoacridine. Some test modifications are discussed.

Revised methods for the salmonella mutagenicity test

Graphene quantum dots (GQDs) have various alluring properties and potential applications, but their large-scale applications are limited by current synthetic methods that commonly produce GQDs in small amounts. Moreover, GQDs usually exhibit polycrystalline or highly defective structures and thus poor optical properties. Here we report the gram-scale synthesis of single-crystalline GQDs by a facile molecular fusion route under mild and green hydrothermal conditions. The synthesis involves the nitration of pyrene followed by hydrothermal treatment in alkaline aqueous solutions, where alkaline species play a crucial role in tuning their size, functionalization and optical properties. The single-crystalline GQDs are bestowed with excellent optical properties such as bright excitonic fluorescence, strong excitonic absorption bands extending to the visible region, large molar extinction coefficients and long-term photostability. These high-quality GQDs can find a large array of novel applications in bioimaging, biosensing, light emitting diodes, solar cells, hydrogen production, fuel cells and supercapacitors.

/pdf/gram-scale-synthesis-of-single-crystalline-graphene-quantum-1r7399salb.pdf

Gram-scale synthesis of single-crystalline graphene quantum dots with superior optical properties

The nitrated polycyclic aromatic hydrocarbons constitute a group of chemicals of environmental concern which display a broad spectrum of mutagenic, genotoxic and carcinogenic properties. Some members of the group are the most potent direct-acting bacterial mutagens while others exhibit low levels of potencies which require metabolic activation mixtures. Bacterial mutagenicity is dependent upon reduction of the nitro function. In mammalian cell systems the genetic and genotoxic effects of these nitrated chemicals include the induction of unscheduled DNA synthesis, sister-chromatid exchanges, chromosomal aberrations, gene mutations and cell transformation. The qualitative as well as quantitative expression of these effects is dependent upon the species and tissue of origin as well as culture history of the cell which in turn determine their enzymic capabilities and the conversion of these nitroarenes to ultimate mutagens and genotoxicants. In eukaryotic cells the following bioactivation pathways have been recognized: (a) reduction of the nitro moiety, (b) ring oxidation (the nature of which is influenced by the nitro function) followed by reduction of the nitro group, and (c) ring oxidation without concomitant reduction of the nitro moiety.

Mutagenicity and genotoxicity of nitroarenes: All nitro-containing chemicals were not created equal

Reported values for the absorption cross section of particulate carbon per unit mass range from under 4 to over 20 m2/g, and the intermediate value of 10 m2/g is used by many as a standard gram-specific absorption cross section for atmospheric soot. In order to better understand the possible variations in absorption by atmospheric carbon, we reevaluated its optical properties in terms of the material composition and morphology of soot and the electrodynamics of spherules agglomerated into loose (ramiform) aggregates. Primary particles ranging in composition from paracrystalline graphite to low-density air/graphite volume mixtures are considered. The effects on extinction efficiency of aggregation and of internal mixing of carbon with sulfate are considered in detail. We also compare our results with estimates of specific absorption of internally mixed soot that are based on several homogeneous mixing rules (effective medium approximations), On the basis of our modeling of the optical properties of aggregates of graphitic carbon grains, we conclude that 10 m2/g may be over 50% too high in many cases, and we suggest that the mass absorption coefficient for the light-absorbing carbon in diesel soot at a wavelength of 0.550 μm may often be less than 7 m2/g, although variations in optical constants and, especially, the specific gravity of the absorbing material make it difficult to assign a specific numerical value. Adhesion of carbon grains to sulfate droplet surfaces is expected to enhance their absorption by no more than about 30%. Soot randomly positioned within droplets, however, can display averaged absorption enhancement factors of about 2.5–4 for hosts with refractive indices ranging from 1.33–1.53, respectively, and radii ≳0.20 μm. Nonetheless, calculations indicate that for realistic dry particle populations, αa < 10 m2/g for graphitic carbon in the atmosphere unless (1) most of it is encapsulated, and (2) the geometric mean radius of the hosts is larger than about 0.06 μm (which corresponds to a mass median diameter of 0.34 μm). These results suggest the importance of the determination of the physical state of the soot particles and their immediate environment when ascribing characteristic values for their absorption and scattering efficiencies.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/1998JD100069

Effects of mixing on extinction by carbonaceous particles

Nitroarenes are postulated to play a principal part among mutagens/carcinogens which are induced in the combustion process and, in addition, are widely distributed in the environment. This review deals with the following points concerning nitroarene toxicity. Data on the mutagenicity of nitroarenes obtained by short-term bioassays are expected to provide us with sufficient information for us to determine their genotoxicity and carcinogenicity. Therefore, mutagenicity detected with Salmonella, Escherichia, and yeast test systems is discussed. Genotoxicity in mammalian cells is also important for determining the mutagenic properties of nitroarenes. In this article, mutagenicity in Chinese hamster ovary cells, sister chromatid exchanges, and cell transformation is summarized. The metabolism of nitroarenes in vivo and in vitro is of importance for determining their behavior and active forms. Therefore, current studies regarding metabolism of nitroarenes are described. Carcinogenicity of nitroarenes for animals has been reported by many workers. In this review, the incidence and histological features of tumors induced by nitroarenes are described. Furthermore, the possible association between human lung cancer and nitroarenes is discussed. Sources of nitroarenes in the environment are given. The results of various chemical tests for identifying nitroarenes are summarized, and speculation on the risk of nitroarenes for humans is presented.

Mutagenicity and Carcinogenicity of Nitroarenes and Their Sources in the Environment

Extracts of selected xerographic toners and copies were found to be mutagenic in the Salmonella assay. The activity was independent of the xerographic hardware and process and was traced to nitropyrenes present as impurities in the carbon black, the toner colorant. Manufacturing process changes resulted in a substantial reduction of the nitropyrene content of the carbon black and thus in the mutagenicity of the corresponding toners. Nitropyrenes are potent frameshift mutagens, and possible mechanisms for their biological action are discussed.

http://science.sciencemag.org/content/sci/209/4460/1039.full.pdf

Nitropyrenes: isolation, identificaton, and reduction of mutagenic impurities in carbon black and toners.

A comparison of carbon black with soot.

An automated method for measuring the non-porous surface area of carbon black is disclosed. The method comprises passing a small sample of a CTAB-carbon black dispersion through a disposable filter to separate the carbon black with adsorbed CTAB from the filtrate containing unadsorbed CTAB. The filtrate next passes through a measuring loop and a high pressure liquid chromatography column to separate the CTAB from the other filtrate components. The CTAB is next sensed by a detector and an integrator calculates the amount of CTAB adsorbed by the carbon black and the non-porous surface area of the carbon black. The integrated apparatus for carrying out this method is also described. Once the carbon black and the CTAB are mixed, there is no further handling of the sample. The system is entirely automated and takes only a few minutes for the CTAB area determination. Measuring temperatures can also be fixed. This results in much more reproducible CTAB numbers for a particular carbon black.

Apparatus for measuring the non-porous surface area of carbon black

Method for measuring non-porous surface area of carbon black

L'invention concerne un systeme ferme pour determiner automatiquement la quantite de bromure de cetyltrimethylammonium adsorbee par du noir de carbone dans une dispersion bromure de cetyltrimethylammonium - noir de carbone. Selon l'invention, il comprend un recipient 2 contenant la dispersion, un moyen pour forcer la dispersion a sortir du recipient, un filtre regle en temperature 7 en communication avec le recipient pour former un filtrat de la dispersion, un circuit de mesure 9 mesurant une quantite specifiee du filtrat, une colonne de chromatographie liquide haute pression 10 separant le bromure de cetyltrimethylammonium du restant du filtrat, un detecteur 13 de la presence du bromure de cetyltrimethylammonium separe et un integrateur 14 pour determiner la quantite de bromure de cetyltrimethylammonium detecte par le detecteur et mettre cette quantite en rapport avec la quantite du bromure de cetyltrimethylammonium adsorbee par le noir de carbone. L'invention s'applique notamment a la mesure et a l'analyse, notamment du noir de carbone.

Sanders Daniel R

Papers

Nitropyrenes: isolation, identificaton, and reduction of mutagenic impurities in carbon black and toners.

A comparison of carbon black with soot.

Apparatus for measuring the non-porous surface area of carbon black

Method for measuring non-porous surface area of carbon black

Procede et dispositif pour mesurer l'aire superficielle non poreuse d'un noir de carbone au moyen de bromure de cetyltrimethylammonium