Bovine albumin Fraction V (pH 7.0)

Standard grade, lyophilised Albumin. Bovine serum albumin (BSA) is added as a stabilizing component for proteins/enzymes to several enzyme reaction and storage buffers. The concentration usually ranges from 0.01% (0.1mg/mL) to 3% (30mg/mL). BSA is added to the 10X concentrated buffers of DNA-modifying enzymes or restriction enzymes in a concentration of 0.5mg/mL. Alternatively, BSA can be substituted by gelatin for such purposes at the same concentration. Besides, albumin is applied as a blocking agent for blocking unbound surfaces of blotting membranes in immunoblots (3%) or ELISAs (3% in PBS) or for the dilution of antisera and antibody-stock solutions, respectively. In ELISAs, BSA is frequently replaced by non-fat dried milk. This fraction of albumin has been manufactured by a combination of the heat-shock method and alcohol precipitation. Albumin is stable as powder (3 years) or in solution (biological buffers like PBS, one year at +4°C to -20°C). Stock solutions are prepared in concentrations up to 20%. If crystals are formed during storage of the solutions, they can be redissolved by warming up to 37°C and mixing. Usually, sodium azide is added at a final concentration of 2 mM (or 0.02 - 0.2%) to prevent microbial contaminations.