In contrast to avidin, though, streptavidin is not glycosylated, which makes the protein less prone to nonspecific binding in IHC applications. Thermo Fisher Scientific products are made with a recombinant form of streptavidin, having a mass of ~53 kDa and a near-neutral pI.

Streptavidin (SA) is a biotin-binding protein isolated from Streptomyces avidinii, and is similar in size and affinity for biotin. These features of avidin make detecting or purifying biotin-labeled proteins or other molecules particularly useful for a number of biomedical applications. The bond between biotin and avidin is formed very rapidly, and once formed, is unaffected by extremes in pH, temperature, organic solvents and other denaturing agents. However, because of its carbohydrate content and basic pI, avidin exhibits relatively high nonspecific binding properties.Īvidin–biotin binding is the strongest known non-covalent interaction between a protein and ligand. Extensive chemical modification has little effect on the activity of avidin, making it especially useful for protein purification.

The extent of glycosylation on avidin is very high carbohydrates account for about 10% of the total mass of the tetramer. Avidin has a basic isoelectric point (pI) of 10 to 10.5 and is stable over a wide range of pH and temperatures. Each subunit consists of 128 amino acids and binds one molecule of biotin thus, a total of four biotin molecules can bind to a single avidin molecule. It contains four identical subunits having a combined mass of 67 to 68 kDa. The extraordinary affinity of avidin (AV) for biotin allows biotin-containing molecules in a complex mixture to be specifically bound to avidin. Avidin is a glycoprotein found in the egg white and tissues of birds, reptiles and amphibia.

Iclip biotin