核酸Nucleic acid

每个核苷酸由含氮碱基、五碳糖和磷酸组成。DNA 的糖是 2-脱氧核糖，碱基为 A、G、C、T；RNA 的糖是核糖，碱基以 U 代替 T。磷酸与糖交替连接构成骨架，碱基伸向一侧，序列按 5′→3′ 方向书写。磷酸基在生理 pH 下带负电，所以核酸是多聚阴离子，在 260 nm 有强紫外吸收。

Each nucleotide has a nitrogenous base, a five-carbon sugar and a phosphate. In DNA the sugar is 2-deoxyribose and the bases are A, G, C and T; in RNA the sugar is ribose and U replaces T. Alternating phosphate and sugar form the backbone with the bases projecting to one side, and sequences are written 5′→3′. The phosphates are negatively charged at physiological pH, so nucleic acids are polyanions, and they absorb strongly at 260 nm.

1869 年米舍尔从脓细胞的细胞核中分离出一种富含磷的物质，称为“核素”；1889 年奥尔特曼改称核酸。科塞尔鉴定出五种碱基，获 1910 年诺贝尔生理学或医学奖。1944 年艾弗里等用肺炎球菌转化实验证明 DNA 是遗传物质；1950 年查加夫发现 A = T、G = C 的规律；1953 年沃森和克里克根据富兰克林和威尔金斯的 X 射线衍射数据提出 DNA 双螺旋结构。

In 1869 Miescher isolated a phosphorus-rich substance from the nuclei of pus cells, calling it nuclein; Altmann renamed it nucleic acid in 1889. Kossel identified the five bases and received the 1910 Nobel Prize in Physiology or Medicine. In 1944 Avery and colleagues showed with pneumococcal transformation that DNA is the genetic material, in 1950 Chargaff found the rules A = T and G = C, and in 1953 Watson and Crick, using X-ray data from Franklin and Wilkins, proposed the double helix.

中心法则描述了 DNA 复制、转录为 RNA、翻译为蛋白质的信息流。核酸化学催生了 PCR（1983 年）、DNA 测序（1977 年桑格法）、基因工程、CRISPR 基因编辑（2020 年诺贝尔化学奖）和 mRNA 疫苗。核酸也可作催化剂（核酶），支持“RNA 世界”生命起源假说。

The central dogma describes the flow of information from DNA replication to transcription into RNA and translation into protein. Nucleic acid chemistry has given us PCR (1983), DNA sequencing (Sanger's method, 1977), genetic engineering, CRISPR genome editing (Nobel Prize in Chemistry 2020) and mRNA vaccines. Nucleic acids can also be catalysts (ribozymes), supporting the RNA-world hypothesis of life's origin.