The labeling of newly synthesized DNA in cells to identify cell proliferation is an important experimental technique. The most accurate methods incorporate [(3)H]thymidine or 5-bromo-2'-deoxyruidine (BrdU) into dividing cells during S phase, which is subsequently detected by autoradiography or immunohistochemistry, directly measuring the newly synthesized DNA. Recently, a novel method was developed to detect DNA synthesis in proliferating cells based on a novel thymidine analog, 5-ethynyl-2'-deoxyuridine (EdU). EdU is incorporated into DNA and subsequently detected with a fluorescent azide via "click" chemistry. This novel technique is highly sensitive and does not require DNA denaturation. However, it was also found that EdU exhibits time-dependent inhibition effects on cell growth. Therefore, here we report a novel deoxycytidine analog, 5-ethynyl-2'-deoxycytidine (EdC), that can be used to detect DNA synthesis in vitro and in vivo at a similar sensitivity level compared with EdU. Furthermore, the EdC-induced cytotoxicity is much less than that of EdU when combined with thymidine. This will be a potential application for the long-term detection of proliferating cells.

中文翻译：

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5-乙炔基-2'-脱氧胞苷作为DNA标记的新剂：检测增殖细胞

在细胞中标记新合成的DNA以识别细胞增殖是一项重要的实验技术。最准确的方法是在S期将[（3）H]胸苷或5-溴2'-脱氧钌（BrdU）整合到分裂细胞中，随后通过放射自显影或免疫组织化学法对其进行检测，直接测量新合成的DNA。最近，基于新型胸苷类似物5-乙炔基-2'-脱氧尿苷（EdU），开发了一种检测增殖细胞中DNA合成的新方法。将EdU掺入DNA中，然后通过“点击”化学方法用荧光叠氮化物检测。这项新技术非常敏感，不需要DNA变性。然而，还发现EdU对细胞生长表现出时间依赖性抑制作用。所以，在这里，我们报告了一种新型的脱氧胞苷类似物5-乙炔基-2'-脱氧胞苷（EdC），可用于在体外和体内检测DNA合成，其灵敏度与EdU相似。此外，当与胸苷联合使用时，EdC诱导的细胞毒性远小于EdU。这将是长期检测增殖细胞的潜在应用。