Streptavidin (APC)

Streptavidin is a 55 kDa (subunit MW 14 kDa) biotin-binding protein isolated from Streptomyces avidini. Streptavidin is superior to avidin, because it does not contain carbohydrate like avidin and has no net charge at neutral pH. Streptavidin~biotin system is routinely used in Immunohistochemistry (IHC). Extinction Coefficient 1% A280=32.0; Purity: Streptavidin used is 99% pure by HPLC; Eletrophoretically homogenous, single band, Protein content: > 95%; Activity 14.8 units/ mg, one unit bunds 1.0 microgram of d-biotin; Protease activity: 0.000018 units/mg; Isoelectric point: 7.0 +/- determined by Isoelectric focusing. Allophycocyanin is a protein from the light-harvesting phycobiliprotein family, along with phycocyanin, phycoerythrin and phycoerythrocyanin. It is an accessory pigment to chlorophyll. Allophycocyanin absorbs and emits red light (650 & 660?nm max, respectively), and is readily found in Cyanobacteria (also called blue-green algae), and red algae. Phycobilin pigments have fluorescent properties that are used in immunoassay kits. Allophycocyanin can be isolated from various species of red or blue-green algae, each producing slightly different forms of the molecule. It is composed of two different subunits (α and β) in which each subunit has one phycocyanobilin (PCB) chromophore. The subunit structure for APC has been determined as (αβ)3. The molecular weight of APC is 105,000 Daltons. Absorption max: 652 nm, additional adsorption 625 nm, Emission max. 657.5 nm, Extinction Coefficient: 2.4 1 (mg/ml), A650/A280=4, A650/A620=1.25.