Reaction of 3',5'-di-O-acetyl-2'-deoxyguansoine with hypobromous acid

Effect of bromide on the degradation kinetics of antibiotic resistance genes during water chlorination

Degradation of antibiotic resistance genes (ARGs) in water chlorination can be influenced by bromide (Br-), a common component in water matrices; however, detailed kinetic information on this process is limited. This study investigated the degradation kinetics tetA and blaTEM-1 genes, contained within the plasmid pWH1266, when exposed to bromine, chlorine, and chlorine with varying concentrations of Br- across a pH range of 7.0-8.5. The degradation of four ARG amplicons, measured using quantitative polymerase chain reaction, was observed to pursue second-order kinetics with bromine, exhibiting k of 4.0 × 102 - 1.6 × 103 M-1 s-1 at pH 7.0 and 2.6 × 102 - 9.6 × 102 M-1 s-1 at pH 8.5. These k values increased linearly with the length of the ARG sequences (209-1136 bps), yielding sequence-independent k of 1.2 and 7.4 × 10-1 (M AT + GC)-1 s-1 at pH 7.0 and 8.5, respectively. The degradation rate of ARGs during chlorination increased with rising Br- concentration due to the bromine formation through the reaction between chlorine with Br-, which subsequently degrades ARGs more rapidly than chlorine. This behavior was successfully simulated using a kinetic model derived from the reaction kinetics of bromine and chlorine reactions with ARGs. The existence of dissolved organic matter extracts only marginally decreased the enhanced degradation of ARGs with Br-, while ammonia significantly inhibited this process during chlorination, both with and without Br-, due to the low reactivity of NH2Cl and NH2Br toward ARGs. These findings highlight the importance of Br- in ARG degradation during water chlorination and the need for further studies in diverse water matrices.

Reactions of 3′,5′-di-O-acetyl-2′-deoxyguansoine and 3′,5′-di-O-acetyl-2′-deoxyadenosine to UV light in the presence of uric acid

Introduction

Recently, it was revealed that uric acid is a photosensitizer of reactions of nucleosides on irradiation with UV light at wavelengths longer than 300 nm, and two products generated from 2′-deoxycytidine were identified. In the present study, UV reactions of acetylated derivatives of 2′-deoxyguansoine and 2′-deoxyadenosine were conducted and their products were identified.

Findings

Each reaction of 3′,5′-di-O-acetyl-2′-deoxyguansoine or 3′,5′-di-O-acetyl-2′-deoxyadenosine with UV light at wavelengths longer than 300 nm in the presence of uric acid generated several products. The products were separated by HPLC and identified by comparing UV and MS spectra of the products with previously reported values. The major products were spiroiminodihydantoin, imidazolone, and dehydro-iminoallantoin nucleosides for 3′,5′-di-O-acetyl-2′-deoxyguansoine, and an adenine base and a formamidopyrimidine nucleoside for 3′,5′-di-O-acetyl-2′-deoxyadenosine.

Conclusions

If these damages caused by uric acid with sunlight occur in DNA of skin cells, mutations may arise. We should pay attention to the genotoxicity of uric acid in terms of DNA damage to dGuo and dAdo sites mediated by sunlight.

Formation of 8-S-L-Cysteinyladenosine from 8-Bromoadenosine and Cysteine

When 8-bromoadenosine was incubated with cysteine at pH 7.2 and 37°C, an exclusive product was generated. This product was identified as a cysteine substitution derivative of adenosine at the 8 position, 8-S-L-cysteinyladenosine. The reaction accelerated as pH increased from mildly acidic to basic conditions. The isolated cysteine adduct of adenosine decreased with a half-life of 15 h at pH 7.2 and 37°C. Similar results were obtained for the incubation of 8-bromo-2'-deoxyadenosine and 8-bromoadenosine 3',5'-cyclic monophosphate with cysteine. These results suggest that 8-bromoadenine in nucleotides, RNA, and DNA can react with thiols, resulting in adducts under physiological conditions.

Recent Advances in the Synthesis of Hydantoins: The State of the Art of a Valuable Scaffold

The review highlights the hydantoin syntheses presented from the point of view of the preparation methods. Novel synthetic routes to various hydantoin structures, the advances brought to the classical methods in the aim of producing more sustainable and environmentally friendly procedures for the preparation of these biomolecules, and a critical comparison of the different synthetic approaches developed in the last twelve years are also described. The review is composed of 95 schemes, 8 figures and 528 references for the last 12 years and includes the description of the hydantoin-based marketed drugs and clinical candidates.

Reaction of Thymidine with Hypobromous Acid in Phosphate Buffer

When thymidine was treated with hypobromous acid (HOBr) in 100 mM phosphate buffer at pH 7.2, two major product peaks appeared in the HPLC chromatogram. The products in each peak were identified by NMR and MS as two isomers of 5-hydroxy-5,6-dihydrothymidine-6-phosphate (a novel compound) and two isomers of 5,6-dihydroxy-5,6-dihydrothymidine (thymidine glycol) with comparable yields. 5-Hydroxy-5,6-dihydrothymidine-6-phosphate was relatively stable, and decomposed with a half-life of 32 h at pH 7.2 and 37°C generating thymidine glycol. The results suggest that 5-hydroxy-5,6-dihydrothymidine-6-phosphate in addition to thymidine glycol may have importance for mutagenesis by the reaction of HOBr with thymine residues in nucleotides and DNA.

Formation of the carboxamidine precursor of cyanuric acid from guanine oxidative lesion dehydro-guanidinohydantoin

DNA damage under oxidative stress leads to oxidation of guanine base. The identification of the resulting guanine lesions in cellular DNA is difficult due to the sensitivity of the primary oxidation products to hydrolysis and/or further oxidation. We isolated dehydroguanidino-hydantoin (DGh) (or oxidized guanidinohydantoin), a secondary oxidation product of guanine, and showed that this lesion reacts readily with nucleophiles such as asymmetric peroxides and transforms to 2,4,6-trioxo-1,3,5-triazinane-1-carboxamidine residue. Further hydrolysis of this intermediate leads to cyanuric acid and finally to urea residue. This work demonstrates a new possible pathway for the formation of the well-known carboxamidine precursor of cyanuric acid lesion.