5-Hydroxymethylcytosine (5hmC) was present in T-even phage and mammalian DNA. 5hmC in phage is formed by hydroxymethylation of the cytosine base in deoxycytidylate (dCMP) by deoxycytidylate hydroxymethylase (CH), whic...5-Hydroxymethylcytosine (5hmC) was present in T-even phage and mammalian DNA. 5hmC in phage is formed by hydroxymethylation of the cytosine base in deoxycytidylate (dCMP) by deoxycytidylate hydroxymethylase (CH), which uses the solvent water as the hydroxyl group donor. By contrast, 5hmC is formed in mammal zygotes by the oxidation of 5-methylcytosine (5mC). 5hmC was also present in a nucleoside antibiotic mildiomycin and its formation is governed by a cytidylate hydroxymethylase MilA. However, the catalytic mechanism remains unknown. In the present study, we purified His-tagged MilA and fed its in vitro reaction with H218O. The LC-MS analysis of the product revealed that 18O was incorporated into the hydroxymethylated CMP (HmCMP), and the secondary MS result of 18O-labeled HmCMP indicated that 18O was incorporated into the cytosine of HmCMP. The results demonstrate that MilA uses solvent water as the hydroxyl group donor like CH. Moreover, Thr102 of MilA was predicted as potential critical amino acid anchoring one molecule of water for hydroxylation. Finally, organizational context comparison in microbial genomes reveals that six homologous ORFs originally annotated as putative thymidylate synthase (TS) are more likely to be CMP hydroxymethylase.展开更多
The antioxidant capacity and changes in chemical composition of two grape varieties, the new hybrid BRS-Carmem and the Bord6 grape （Vitis labrusca） and of their products （juice, wine and vinegar） were evaluated by...The antioxidant capacity and changes in chemical composition of two grape varieties, the new hybrid BRS-Carmem and the Bord6 grape （Vitis labrusca） and of their products （juice, wine and vinegar） were evaluated by several techniques. The DPPH method was used to measure the antioxidant capacity, whereas, the total phenolic contents （TPC） were measured by Folin-Ciocalteau method. Overall chemical composition was also monitored by ESI-MS fingerprints and UPLC-MS analysis. For both grape varieties, the highest （and similar） antioxidant capacity and TPC were observed for the wine and vinegar samples followed by the grapes and then the juices. In addition, ESI-MS fingerprints and UPLC-MS analysis in the negative ion mode indicated substantial changes in chemical composition from grape to juice and wine, and then to vinegar.展开更多
基金supported by the National Natural Science Foundation of China (31170083)the Ministry of Science and Technology (2012CB721004)the Shanghai Municipal Council of Science and Technology
文摘5-Hydroxymethylcytosine (5hmC) was present in T-even phage and mammalian DNA. 5hmC in phage is formed by hydroxymethylation of the cytosine base in deoxycytidylate (dCMP) by deoxycytidylate hydroxymethylase (CH), which uses the solvent water as the hydroxyl group donor. By contrast, 5hmC is formed in mammal zygotes by the oxidation of 5-methylcytosine (5mC). 5hmC was also present in a nucleoside antibiotic mildiomycin and its formation is governed by a cytidylate hydroxymethylase MilA. However, the catalytic mechanism remains unknown. In the present study, we purified His-tagged MilA and fed its in vitro reaction with H218O. The LC-MS analysis of the product revealed that 18O was incorporated into the hydroxymethylated CMP (HmCMP), and the secondary MS result of 18O-labeled HmCMP indicated that 18O was incorporated into the cytosine of HmCMP. The results demonstrate that MilA uses solvent water as the hydroxyl group donor like CH. Moreover, Thr102 of MilA was predicted as potential critical amino acid anchoring one molecule of water for hydroxylation. Finally, organizational context comparison in microbial genomes reveals that six homologous ORFs originally annotated as putative thymidylate synthase (TS) are more likely to be CMP hydroxymethylase.
文摘The antioxidant capacity and changes in chemical composition of two grape varieties, the new hybrid BRS-Carmem and the Bord6 grape （Vitis labrusca） and of their products （juice, wine and vinegar） were evaluated by several techniques. The DPPH method was used to measure the antioxidant capacity, whereas, the total phenolic contents （TPC） were measured by Folin-Ciocalteau method. Overall chemical composition was also monitored by ESI-MS fingerprints and UPLC-MS analysis. For both grape varieties, the highest （and similar） antioxidant capacity and TPC were observed for the wine and vinegar samples followed by the grapes and then the juices. In addition, ESI-MS fingerprints and UPLC-MS analysis in the negative ion mode indicated substantial changes in chemical composition from grape to juice and wine, and then to vinegar.
