BSA (Bovine serum albumin,CAS:9048-46-8), a globulin in bovine serum, contains 607 amino acid residues, has a molecular weight of 66.446 KDa and an isoelectric point of 4.7. Bovine serum albumin has a wide range of applications in biochemical experiments.
The role of BSA（bovine serum albumin）
Bovine serum albumin (BSA) is generally used as a stabilizer in storage solutions and reaction solutions for restriction enzymes or modified enzymes, because some enzymes are unstable or have low activity at low concentrations. After adding BSA, it may play a "protection" or "carrier" role. Many enzymes can greatly increase their activity after adding BSA. Enzymes that do not need to add BSA will not be affected by the addition of BSA. For most substrate DNA, BSA can make the digestion more complete, and can achieve repeated cutting. At 37℃, when the digestion reaction exceeds 1h, BSA can make the enzyme more stable, because in the reaction buffer without BSA, many restriction enzymes can only survive 10"20min or even shorter time at 37℃ And BSA can bind to the metal ions and other chemical substances in the buffer or substrate DNA that inhibit the activity of restriction enzymes.
Classification and selection of bovine serum albumin 
1.BSA (the lowest grade BSA), this is BSA in the ordinary sense, as long as the main component is BSA products can become bovine serum albumin, so it also covers other grades of BSA, so customers should pay attention Its purity (usually for industrial production).
2.The fifth component of BSA. This is a biotechnology-grade product with the widest application range. Some manufacturers have very low BSAV fatty acids and endotoxins and can be directly used for cell culture, with high purity and even any related applications. Experiment (Elisa experiment, WB experiment).
3.BSA (no essential fatty acid), the fatty acid content is very low, the fatty acid content is less than 0.002% (w/w), or the fatty acid concentration in 1% BSA solution is less than 2 µmol/L (can be used to determine the release of Free fatty acid concentration, etc.).
4.BSA (no protease), or Protease-free bovine serum albumin, or Protease Free BSA, the product does not contain DNAse enzyme, protease and IgG (used for radioimmunity, enzyme-linked immunoassay and as a diluent or blocking Agent, etc.).
5.BSA(cell culture grade) is only 98% pure, but requires extremely low fatty acid content and endotoxin content (cell culture and cell culture related experiments, etc.).
6.BSA, high purity, with a purity of over 99% (gold-labeled grade, production of gold-labeled antibodies, etc.).
7.Cross-linked BSA: freeze-dried powder, containing monomer (66000), dimer (132000), trimer (198000), tetramer (264000), etc. (determine the molecular weight of unknown proteins, and can also be used for biochemical Teaching experiments to explore the conditions of electrophoresis, verify the results of electrophoresis, etc.).