性能描述

溶解性：Streptavidin is soluble in water at 1 mg/mL, or in phosphate buffered saline (PBS). Solutions in PBS or water can be stored several months at 4°C or for more than a year as frozen aliquots.

Streptavidin is a protein produced by the bacterium Streptomyces avidinii. It has four binding sites for biotin,as does avidin. Both have been used extensively as probes in immunochemical systems, conjugated to antibodies, enzymes or fluorochromes. However, avidin is highly basic (pI ~ 10.5), compared to streptavidin (pI
~ 5-6). Avidin has a slightly higher binding capacity for biotin than streptavidin does, but it has glycosylated side chains which give higher backgrounds in blotting techniques than does streptavidin, which is not a glycoprotein.4 Streptavidin is more resistant than avidin to dissociation into subunits by guanidinium chloride.

链霉亲和素(streptavidin下称SA)是与亲和素(svidin下称AV)有相似生物学特性的一种蛋白质。
链霉亲和素(SA)是streptomyces avidinii菌的分泌物，其分子量及结合生物素的能力与鸡蛋清中的亲和素相似，等电点6.0，非特异性结合远比亲和素低。
一 、来源：SA 是Streptomyces avicllrdi菌培养过程中的分泌产物，主要通过2一亚氨基生物索亲和层析法提纯，1L培养液中含蛋白10~60mg 。
二、分子量 ：链霉亲和素是四聚体蛋白，大小为66KDa。一分子链霉亲和素可以高度特异性地与四分子生物素结合，两者之间的亲和力极为强烈，链霉亲和素-生物素复合物的解离常数处于 10 mol/L 数量级，这一性质常用于分子生物学用途[1]。其中一条完整的SA肽链中有159个氨基酸残基，分子量为16450。
三、比消光系数：消光系数与蛋白中Tyr含量有关， 由于SA 中Tyr的含量比AV 多，所以SA的比消光系数也较AV 为高，两者分别为E 1mg/mL=3．40和E1mg/mL=1.57。在282nm 上这两种蛋白结合生物素后并不改变其消光系数，而在233nm上，它们结合生物素后郡便其消光系数值增高，现在一般都是利用蛋白的这种吸光特点来测定它们的活性。