Dear Editor, DNA methylation, which often occurs at the 5-carbon position of cytosine （5mC） located in CpG dinucleotide, is a key epigenetic hallmark and serves as a major epigenetic mechanism for establishing X-in...Dear Editor, DNA methylation, which often occurs at the 5-carbon position of cytosine （5mC） located in CpG dinucleotide, is a key epigenetic hallmark and serves as a major epigenetic mechanism for establishing X-inactivation, parental imprinting and silencing retrotransposable elements during early embryogenesis in mammals. Accumulative evidence also suggests that DNA methylation plays key roles in transcriptional regulation [1].展开更多
A novel catalyst, MgFe 2O 4, for hydroxylation of phenol with hydrogen peroxide was synthesized via coprecipitation method from an aqueous solution containing Fe(NO 3) 3·9H 2O and Mg(NO 3) 2·6H 2O with ammon...A novel catalyst, MgFe 2O 4, for hydroxylation of phenol with hydrogen peroxide was synthesized via coprecipitation method from an aqueous solution containing Fe(NO 3) 3·9H 2O and Mg(NO 3) 2·6H 2O with ammonia. The X ray diffraction peaks of the catalyst show that the as prepared sample has engendered MgFe 2O 4 crystal with spinel structure, which is also confirmed by its IR spectrum. In the hydroxylation of phenol with hydrogen peroxide, MgFe 2O 4 catalyst exhibited high activity after a short induction period. In particular, the addition of a little amount of acetic acid in the reaction liquid can effectively shorten the induction period. Under the same reaction conditions, the diphenol selectivity over MgFe 2O 4 is higher than that over TS 1, furthermore, the reaction time is shortened greatly. The experimental phenomena can be explained by the free radical mechanism.展开更多
Two kinds of micro organism, Arthrobacter sp. AX86(1,4 dehdrogenator)and Absidia sp. A28(11α hydroxylator)were used in this experiment.Two different fermentation techniques were performed to accomplish the multiple c...Two kinds of micro organism, Arthrobacter sp. AX86(1,4 dehdrogenator)and Absidia sp. A28(11α hydroxylator)were used in this experiment.Two different fermentation techniques were performed to accomplish the multiple conversional reactions for producing 16β methyl 11α,17α,21 trihydroxy 1,4 pregnadiene 3,20 dione(Ⅲ)from 16β methyl 3β,17α,21 trihydroxy 5α pregnane 20 one 21 acetate(I):1)To produce product(Ⅲ)by means of a two step fermentation method which were independently performed first by Arthrobacter and next by Absiaia, and 2)the product was obtained by a sequential fermentation system of aforesaid two micro organisms in a single fermentor without isolation of the intermediates from the mixture.Our results showed that in both fermentation systems high yield of product was obtained.However,according to the technical simplicity,shorter duration of fermentation cycle and efficient yield of product,the second method is better than the first one.展开更多
文摘Dear Editor, DNA methylation, which often occurs at the 5-carbon position of cytosine （5mC） located in CpG dinucleotide, is a key epigenetic hallmark and serves as a major epigenetic mechanism for establishing X-inactivation, parental imprinting and silencing retrotransposable elements during early embryogenesis in mammals. Accumulative evidence also suggests that DNA methylation plays key roles in transcriptional regulation [1].
文摘A novel catalyst, MgFe 2O 4, for hydroxylation of phenol with hydrogen peroxide was synthesized via coprecipitation method from an aqueous solution containing Fe(NO 3) 3·9H 2O and Mg(NO 3) 2·6H 2O with ammonia. The X ray diffraction peaks of the catalyst show that the as prepared sample has engendered MgFe 2O 4 crystal with spinel structure, which is also confirmed by its IR spectrum. In the hydroxylation of phenol with hydrogen peroxide, MgFe 2O 4 catalyst exhibited high activity after a short induction period. In particular, the addition of a little amount of acetic acid in the reaction liquid can effectively shorten the induction period. Under the same reaction conditions, the diphenol selectivity over MgFe 2O 4 is higher than that over TS 1, furthermore, the reaction time is shortened greatly. The experimental phenomena can be explained by the free radical mechanism.
文摘Two kinds of micro organism, Arthrobacter sp. AX86(1,4 dehdrogenator)and Absidia sp. A28(11α hydroxylator)were used in this experiment.Two different fermentation techniques were performed to accomplish the multiple conversional reactions for producing 16β methyl 11α,17α,21 trihydroxy 1,4 pregnadiene 3,20 dione(Ⅲ)from 16β methyl 3β,17α,21 trihydroxy 5α pregnane 20 one 21 acetate(I):1)To produce product(Ⅲ)by means of a two step fermentation method which were independently performed first by Arthrobacter and next by Absiaia, and 2)the product was obtained by a sequential fermentation system of aforesaid two micro organisms in a single fermentor without isolation of the intermediates from the mixture.Our results showed that in both fermentation systems high yield of product was obtained.However,according to the technical simplicity,shorter duration of fermentation cycle and efficient yield of product,the second method is better than the first one.
