Hawk-Seq™ differentiates between various mutations in Salmonella typhimurium TA100 strain caused by exposure to Ames test-positive mutagens

A precise understanding of differences in genomic mutations according to the mutagenic mechanisms detected in mutagenicity data is required to evaluate the carcinogenicity of environmental mutagens. Recently, we developed a highly accurate genome sequencing method, ‘Hawk-Seq™’, that enables the detection of mutagen-induced genome-wide mutations. However, its applicability to detect various mutagens and identify differences in mutational profiles is not well understood. Thus, we evaluated DNA samples from Salmonella typhimurium TA100 exposed to 11 mutagens including alkylating agents, aldehydes, an aromatic nitro compound, epoxides, aromatic amines, and polycyclic aromatic hydrocarbons (PAHs). We extensively analysed mutagen-induced mutational profiles and their association with the mechanisms of mutagens. Hawk-Seq™ sensitively detected mutations induced by all 11 mutagens, including one that increased the number of revertants by approximately two-fold in the Ames test. Although the sensitivity for less water-soluble mutagens was relatively low, we increased the sensitivity to obtain high-resolution spectra by modifying the exposure protocol. Moreover, two epoxides indicated similar 6-dimensional or 96-dimensional mutational patterns; likewise, three SN1 type alkylating agents indicated similar mutational patterns, suggesting that the mutational patterns are compound category-specific. Meanwhile, an SN2 type alkylating agent exhibited unique mutational patterns compared to those of the SN1 type alkylating agents. Although the mutational patterns induced by aldehydes, the aromatic nitro compound, aromatic amines, and PAHs did not differ substantially from each other, the maximum total base substitution frequencies (MTSFs) were similar among mutagens in the same structural groups. Furthermore, the MTSF was found to be associated with the carcinogenic potency of some direct-acting mutagens. These results indicate that our method can generate high-resolution mutational profiles to identify characteristic features of each mutagen. The detailed mutational data obtained by Hawk-Seq™ can provide useful information regarding mutagenic mechanisms and help identify its association with the carcinogenicity of mutagens without requiring carcinogenicity data.

Selective Formation of Herbicides by Selenium-Catalyzed Oxidative-Reductive Carbonylation of CO

The oxidative-reductive carbonylation of dimethyamine and aromatic nitro-compound catalyzed by selenium to yield herbicides has been studied. The selectivity of herbicide is above 99%. In the reaction there is a phase-transfer process.The catalyst can also be separated from the product by simple phase separation.

High performance Pd nanocrystals supported on SnO2-decorated graphene for aromatic nitro compound reduction

We reported a hybrid material of ultrafine Pd nanocrystals grown on an excellent support of SnO2-decorated graphene nanosheets for the highly efficient reduction of a representative aromatic nitro compound.