No abstract

The ultrahigh-resolution mass spectrometry (UHR-MS) coupled with isotope labeling is of increasing attentions in elucidating the transform mechanisms of dissolved organic matter (DOM).However, there is a paucity of automated formula assignment algorithm applicable to halogenated disinfection byproducts (Xn-DBPs), particurally for iodinated organic compounds, and deuterated DOM . Herein, for the first time, we have developed a novel formula assignment algorithm based on deuterium-labeled UHR-MS, namely FTMSDeu, and the algorithm was applied to determine precursor molecules of Xn-DBPs and evaluate the relative contribution of electrophilic addition and electrophilic substitution reactions in Xn-DBPs formation according to the hydrogen/deuterium exchange of DOM molecules. Furthermore, tandem mass spectrometry with homologous-based network analysis was employed to validate the formula assignment accuracy (41%) of FTMSDeu for iodinated disinfection byproducts (In-DBPs). And the remaining In-DBPs compounds were assigned with the empirical rule of minimum number of non-oxygen heteratoms.The electrophilic substitution accounted for 82%-98%, 71%-89%, and 43%-45% of Xn-DBPs formation for Xn-DBPs containing chlorine, bromine, and iodine, respectively, manifesting the dominant role of electrophilic substitution in chlorine disinfection under conditions of low bromine and iodine concentrations. The absence of presumed Xn-DBPs precursors in some treatments in this study also suggests that Xn-DBPs formation include secondary reactions (e.g., oxidation, hydrolysis) in addition to electrophilic addition and/or substitution of halogens. These findings highlight the significance of isotopically labeled UHR-MS techniques in revealing the transformation of DOM in natural and engineered systems.

No abstract

Background: Helicobacter pylori infection poses a risk of the occurrence of gastrointestinal diseases, such as gastric cancer. Its incidence rate is significantly reduced by eradication, and thereby, eradication therapy is generally performed. Disulfiram is an oral prescription drug mainly used for the treatment of alcohol dependence. In recent years, reports have been made on its anticancer and antibacterial effects, and thus, it has recently become an interesting subject. This study aimed to examine the antibacterial activity of disulfiram, investigate the presence or absence of its antibacterial activity on H. pylori, and determine whether it could be a new bactericidal drug against drug-resistant H. pylori. Materials and Methods: Drug-sensitive strains of H. pylori and amoxicillin-resistant, clarithromycin-resistant, and metronidazole-resistant strains were used, and a growth inhibition test of H. pylori using disulfiram was performed. Furthermore, the expression of urease, vacuolating cytotoxin A (VacA), and CagA, the virulence proteins of H. pylori, was quantitatively analyzed using the Western blotting method. In addition, for H. pylori used in this study, the 16SrDNA sequence, a ribosomal gene involved in protein production, was analyzed to examine the presence or absence of gene mutation. Results: Disulfiram suppressed the growth of 7 out of 12 H. pylori strains at 1 µg/mL, and no correlation was observed between their susceptibility/resistance to current eradication antimicrobial drugs and disulfiram resistance. Disulfiram reduced the expression levels of urease, VacA, and CagA proteins. H. pylori, which showed resistance to disulfiram, tended to have fewer gene deletions/insertions in the 16S rDNA sequence; however, no specific mutation was detected. Conclusion:Disulfiram has a bactericidal effect on H. pylori at low concentrations, suggesting that it can be used as a supplement for current H. pylori eradication drugs.

The infection caused by Helicobacter pylori is associated with several diseases, including gastric cancer. Several methods for the diagnosis of H. pylori infection exist, including endoscopy, the urea breath test, and the fecal antigen test, which is the serum antibody titer test that is often used since it is a simple and highly sensitive test. In this context, this study aims to find the association between different antibody reactivities and the organization of bacterial genomes. Next-generation sequences were performed to determine the genome sequences of four strains of antigens with different reactivity. The search was performed on the common genes, with the homology analysis conducted using a genome ring and dot plot analysis. The two antigens of the highly reactive strains showed a high gene homology, and Western blots for CagA and VacA also showed high expression levels of proteins. In the poorly responsive antigen strains, it was found that the inversion occurred around the vacA gene in the genome. The structure of bacterial genomes might contribute to the poor reactivity exhibited by the antibodies of patients. In the future, an accurate serodiagnosis could be performed by using a strain with few gene mutations of the antigen used for the antibody titer test of H. pylori.