Bovine Serum Albumin

Bovine serum albumin (BSA) is a plasma protein with a calculated molecular weight (MW) of 66,430 Daltons (Da). The major protein in bovine serum, BSA assists in regulation of blood colloidal osmotic pressure. BSA is used in different applications such as immunochemistry, protein quantitation, and cell culture.

This BSA product is specifically tested for the following properties:

• very low FA content / essentially fatty acid free
• low globulin content / essentially globulin free

BSA is a known fatty acid (FA) carrier. Thus when BSA is used specifically in cell culture, control over specific FA′s used to culture cell lines is important, because different cell lines can be variably sensitive to particular fatty acids. Fatty acid-free BSA thus is useful for cell culture work, where the specific FA content must be stringently controlled, so that researchers can control the specific fatty acids needed for their particular cell lines. Fatty acid-free albumin also allows for optimal and maximum binding sites for the specific fatty acids that researchers wish to use in their particular cell culture experiments. Use of FA-free BSA also addresses concerns about endogenous FA′s potentially in non-FA-free BSA.

Certain conformational and primary-sequence epitopes of BSA are suspected allergens in human beef and milk allergies.

Purified by a combination of heat shock and ethanol fractionation

Serum albumin may be referred to as Fraction V. This naming convention is taken from the original Cohn method of fractionating serum proteins using cold ethanol precipitation. Serum albumin was found in the fifth ethanol fraction using Cohn′s method. Since then, the term "Fraction V" has been used by some to describe serum albumin regardless of the method of preparation. Others have used this term to describe serum albumin purified by ethanol fractionation methods that have been highly modified since the original Cohn method was described. Sigma-Aldrich manufactures and distributes serum albumins purified from a variety of primary methods including the true Cohn fractionation method, modified ethanol fractionation methods, heat shock and chromatography. Additional purification steps may include crystallization or charcoal filtration.