Home / Products / Bovine Serum Albumin (BSA)
CAS 9048-46-8 Carrier Protein / Blocking Reagent Carrier Protein / Blocking Reagent Cell Culture Grade

Bovine Serum Albumin (BSA)

IUPAC: Albumin from Bovine Serum (Fraction V) View on PubChem
CAS NUMBER
9048-46-8
MOL. FORMULA
N/A
MOL. WEIGHT
~66,430 Da (66.5 kDa)
Get Commercial Quote Request Sample Request COA
Scientific Overview

BSA's structure comprises 583 amino acid residues organized into three homologous domains formed by six a-helices, stabilized by 17 intrachain disulfide bridges and a single free sulfhydryl group. This structural stability, combined with its carrier-protein binding capacity, explains its dual role in the lab: as a stabilizer that protects labile enzymes and proteins from degradation in solution, and as a blocking reagent that saturates non-specific binding sites in ELISA, Western blot, and immunohistochemistry protocols. The "Fraction V" designation originates from the classical Cohn cold-ethanol fractionation method, where serum albumin was isolated in the fifth ethanol fraction --- a naming convention still used today regardless of the specific purification method (Cohn fractionation, heat-shock, or chromatographic).

Bovine Serum Albumin (BSA), also known as "Fraction V," is a water-soluble, single-chain globular protein isolated from bovine blood serum. Synthesized in the liver, its primary physiological role is regulating colloidal osmotic pressure in blood, while its hydrophobic binding cleft makes it a versatile carrier for fatty acids, hormones, and drugs --- properties that underlie its extensive use across biochemistry, immunoassays, and cell culture.

Full Technical Data
Chemical Name Bovine Serum Albumin (BSA), Fraction V
CAS Number 9048-46-8
IUPAC Name Albumin from Bovine Serum (Fraction V)
Molecular Formula N/A
Molecular Weight ~66,430 Da (66.5 kDa) g/mol
Reaction Scheme
Bovine Blood Serum
NA
NA
Bovine Serum Albumin (Fraction V)
NA
Commercial Applications

Immunoassay Blocking Reagent

Standard blocking agent in ELISA, Western blot, and immunohistochemistry to prevent non-specific antibody binding.

Cell Culture Media Supplementation

Used as a carrier protein and antioxidant supplement in serum-free and specialized cell culture formulations.

Protein Quantification Standard

Reference standard in Bradford, BCA, and other colorimetric protein assay methods.

Enzyme & Protein Stabilization

Applied as a stabilizing excipient for labile enzymes and low-concentration proteins in solution.

Market Therapeutic Focus
CARRIER PROTEIN / BLOCKING REAGENT PHARMACEUTICAL MANUFACTURING CELL & GENE THERAPY / BIOPROCESSING DIAGNOSTICS & IMMUNOASSAYS ACADEMIC & INDUSTRIAL RESEARCH CRO/CDMO
Scientific Literature

The Amino Acid Sequence of Bovine Serum Albumin

Authors: Hirayama, K. et al.

Biochem. Biophys. Res. Commun.

DOI: 10.1016/S0006-291X(05)80105-9

Serum Albumin: Structure and Ligand Binding

Authors: Peters, T.

Adv. Protein Chem.

DOI: 10.1016/S0065-3233(08)60411-8

Bovine Serum Albumin as a Blocking Agent in Immunoassays

Authors: Various

J. Immunol. Methods (immunoassay methodology reference)

Peer Queries & FAQs
Why is BSA called "Fraction V"?
The name originates from the Cohn cold-ethanol fractionation method, where serum albumin was isolated in the fifth of several sequential ethanol precipitation fractions; the term persists today across various purification methods.
What's the difference between standard BSA and specialty grades (protease-free, fatty acid-free, etc.)?
Specialty grades undergo additional purification to remove specific contaminants (residual proteases, bound fatty acids, IgG, endotoxin, or nucleases) that could interfere with sensitive downstream applications like enzyme assays or molecular biology work.
Why is BSA used as a blocking reagent in immunoassays?
Its abundant surface binding sites saturate non-specific protein-binding interactions on assay surfaces (membranes, plates), reducing background signal and improving detection specificity for the target antibody-antigen interaction.
What is the recommended storage condition?
Store lyophilized powder at 2--8°C (or as specified by grade); reconstituted solutions should be stored frozen as aliquots to preserve stability and avoid repeated freeze-thaw cycles.

Need a Custom Derivative or Labeled Analog?

Our R&D centers specialize in the design and process development of complex heterocyclic and chiral molecules — mg to kg scale.

Request Custom Synthesis Quote Check Manufacturing Scale