To solve the problem of high temperature or long reaction time in hydrothermal synthesis of carbon dots （CDs）, a novel method based on the promoting carbonization by hydrochloric acid as catalysis was developed in p...To solve the problem of high temperature or long reaction time in hydrothermal synthesis of carbon dots （CDs）, a novel method based on the promoting carbonization by hydrochloric acid as catalysis was developed in present work. The acid catalyzed carbon dots （ACDs） were prepared facilely from tryptophan and phenylalanine at 200 ~C for 2 h. In our findings, the acids could promote significantly the formation of the ACDs＂ carbon core, as a result of the accelerating of the carbonization due to the easy deoxidation. The ACDs showed an average size of 4.8 nm, and consisted of high carbon crystalline core and various surface groups. The ACDs exhibited good optical properties and pH-dependent photoluminescence （PL） intensities. Furthermore, the ACDs were safe and biocompatible. The experimental results demonstrated that such new ACDs were connected with DNA-aptamer by EDC/NHS reaction maintaining both the bright fluorescence and recognizing ability on the cancer cells, which so could be served as an effective PL sensing platform. The resultant DNA-aptamer with ACDs （DNA-ACDs） could stick to human breast cancer cells （MCF-7） specifically, and exhibited high sensitivity and selectivity, indicating the potential applications in the cancer cells targeted imaging fields.展开更多
DNA methylation is an essential epigenetic modification, and found to be dynamically changed due to the ob- servation of active DNA demethylation. During active demethylation, 5-methylcytosine （5mC） was oxidized ste...DNA methylation is an essential epigenetic modification, and found to be dynamically changed due to the ob- servation of active DNA demethylation. During active demethylation, 5-methylcytosine （5mC） was oxidized step- wise by ten-eleven translocation （TET） enzymes into 5-hydroxymethylcytosine （5hmc）, 5-formylcytosine （5fC）, and 5-carboxylcytosine （5caC）. Then, the subsequent excision of 5fC and 5caC combined with base excision repair further restored cytosine, which completes the demethylation process. Here, we report that 5-formylcytosine and 5-carboxylcytosine significantly reduce the activity of HhaI DNA methyltransferase to methylate target cytosines when present on the hemi-modified sequence of the complementary DNA. This finding demonstrates that 5fC and 5caC function as more than intermediates for active DNA demethylation.展开更多
基金This work was supported by the Major Program of National Natural Science Foundation of China （No. 21334005）, the National Natural Science Foundation of China （Nos. 21304021 and 21432008）, and the National Basic Research Program of China （Nos. 2010CB732203 and 2012CB720603）.
文摘To solve the problem of high temperature or long reaction time in hydrothermal synthesis of carbon dots （CDs）, a novel method based on the promoting carbonization by hydrochloric acid as catalysis was developed in present work. The acid catalyzed carbon dots （ACDs） were prepared facilely from tryptophan and phenylalanine at 200 ~C for 2 h. In our findings, the acids could promote significantly the formation of the ACDs＂ carbon core, as a result of the accelerating of the carbonization due to the easy deoxidation. The ACDs showed an average size of 4.8 nm, and consisted of high carbon crystalline core and various surface groups. The ACDs exhibited good optical properties and pH-dependent photoluminescence （PL） intensities. Furthermore, the ACDs were safe and biocompatible. The experimental results demonstrated that such new ACDs were connected with DNA-aptamer by EDC/NHS reaction maintaining both the bright fluorescence and recognizing ability on the cancer cells, which so could be served as an effective PL sensing platform. The resultant DNA-aptamer with ACDs （DNA-ACDs） could stick to human breast cancer cells （MCF-7） specifically, and exhibited high sensitivity and selectivity, indicating the potential applications in the cancer cells targeted imaging fields.
文摘DNA methylation is an essential epigenetic modification, and found to be dynamically changed due to the ob- servation of active DNA demethylation. During active demethylation, 5-methylcytosine （5mC） was oxidized step- wise by ten-eleven translocation （TET） enzymes into 5-hydroxymethylcytosine （5hmc）, 5-formylcytosine （5fC）, and 5-carboxylcytosine （5caC）. Then, the subsequent excision of 5fC and 5caC combined with base excision repair further restored cytosine, which completes the demethylation process. Here, we report that 5-formylcytosine and 5-carboxylcytosine significantly reduce the activity of HhaI DNA methyltransferase to methylate target cytosines when present on the hemi-modified sequence of the complementary DNA. This finding demonstrates that 5fC and 5caC function as more than intermediates for active DNA demethylation.
