生物素（biotin，B）广泛分布于动、植物组织中，常从含量较高的卵黄和肝组织中提取，分子量244．31Da．生物素化反应快速、高效且不易被干扰。生物素化的分子能通过生物素与链霉亲和素、亲和素互作，且不受高热、pH、蛋白酶解的影响。

Biotin (B) is widely distributed in animal and plant tissues, and is often extracted from high content yolk and liver tissue with a molecular weight of 244.31 Da. The biotinylation reaction is fast, efficient and not susceptible to interference. Biotinylated molecules interact with streptavidin and avidin by biotin and are not affected by hyperthermia, pH, and proteolysis.

生物素分子有两个环状结构（如图），其中Ⅰ环为咪唑酮环，是与亲和素结合的主要部位；II环为噻吩环，C2上有一戊酸侧链，其末端羧基是结合抗体和其他生物大分子结构，经化学修饰后，生物素可成为带有多种活性基团的衍生物——活化生物素。活化生物素可以在蛋白质交联剂的介导下，与已知的几乎所有生物大分子偶联，包括蛋白质，核酸，多糖，脂类等。

The biotin molecule has two cyclic structures (pictured), wherein the I ring is an imidazolidone ring, which is the main site of binding to avidin; the ring II is a thiophene ring, and the C2 has a valeric acid side chain, and the terminal carboxyl group is Combined with antibodies and other biomacromolecules, biotin can be chemically modified to become a derivative with multiple reactive groups - activated biotin. Activated biotin can be conjugated to almost all known biomacromolecules, including proteins, nucleic acids, polysaccharides, lipids, etc., mediated by protein crosslinkers.

生物素与链霉亲和素、亲和素的结合特异且高效，因此这一互作在生物技术的许多领域有着广泛的应用。

The combination of biotin with streptavidin and avidin is specific and efficient, so this interaction has been widely used in many fields of biotechnology.