نتایج جستجو برای: 5. لویکان
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غزنه از شهرهای ایالت زابلستان قدیم به شمار می رفت که در دوران پیش از اسلام مهد تمدن های مهمی چون یونانی، کوشانی و هپتالی بوده است. با فتح سیستان و زابلستان توسط سپاهیان مسلمان، این شهر به یک پایگاه نظامی تبدیل شد. خاندان لُویَکان از بقایای حاکمان پیش از اسلام، در سه قرن نخست هجری به عنوان خراجگذار صفاریان و سامانیان در حکومت غزنه و زابلستان باقی مانده بودند. این شهر در قرن چهارم هجری پایتخت حاکما...
We investigated systematically the effects of Tet-induced oxidation products of 5-methylcytosine on Dnmt1- and DNMT3a-mediated cytosine methylation in synthetic duplex DNA. We found that the replacement of 5-methylcytosine at a CpG site with a 5-hydroxymethylcytosine, 5-formylcytosine, 5-carboxylcytosine or 5-hydroxymethyluracil resulted in altered methylation of cytosine at both the opposite a...
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Nucleotide variants, especially those related to epigenetic functions, provide critical regulatory information beyond simple genomic sequence, and they define cell status in higher organisms. 5-Methylcytosine, which is found in DNA, was until recently the only nucleotide variant studied in terms of epigenetics in eukaryotes. However, 5-methylcytosine has turned out to be just one component of a...
Cytosine can undergo modifications, forming 5-methylcytosine (5-mC) and its oxidized products 5-hydroxymethylcytosine (5-hmC), 5-formylcytosine (5-fC) and 5-carboxylcytosine (5-caC). Despite their importance as epigenetic markers and as central players in cellular processes, it is not well understood how these modifications influence physical properties of DNA and chromatin. Here we report a co...
The Ten-eleven translocation (TET) proteins have been recently identified as critical regulators in epigenetic modification, especially in the methylation of cytosine in DNA. TET-mediated DNA oxidation plays prominent roles in a wide variety of physiological and pathological processes, especially in tumor and neural development. TET proteins execute stepwise enzymatic conversion of 5-methylcyto...
We present a chemical method to selectively tag and enrich thymine modifications, 5-formyluracil (5-fU) and 5-hydroxymethyluracil (5-hmU), found naturally in DNA. Inherent reactivity differences have enabled us to tag 5-fU chemoselectively over its C modification counterpart, 5-formylcytosine (5-fC). We rationalized the enhanced reactivity of 5-fU compared to 5-fC via ab initio quantum mechanic...
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