This 250µg container of native, human C4 complement component is a glycoprotein composed of three non-identical subunits of M.W. of 93 kDa (α), 75 kDa (β), and 32 kDa (γ) linked by disulfide bonds. It is present in normal human serum at 400 µg/mL. On activation of complement via the classical pathway, the C1s subcomponent of the C1 complex is converted to an active serine protease that cleaves the C4 α-chain at peptide bond 77, resulting in production of C4a (M.W. 8740) and C4b fragments (M.W. 193 kDa). The released C4a peptide is one of the three complement-derived anaphylatoxins. The nascent C4b fragment can form a covalent ester bond with target surfaces. This covalent attachment of C4b to target acceptors is required for continuation of activation via classical pathway. The biological activity is greater than or equal to 60% of the C4 activity present in freshly drawn normal human serum on a mg to mg basis. It is prepared from serum that has been shown by certified tests to be negative for HBsAg and for antibodies to HIV and HCV. Material: Complement C4, Human. Form: Liquid. Formulation: In PBS, pH 7.2. Molar Mass: 200000. Specific Activity: Greater Than 3 x 105 C4H50 units/mg. Purity: Greater Than Or Equal To 90% By SDS-PAGE. Storage: Below -70°C. Ship: Dry Ice Only, Standard Handling. Quantity: 250µg. EMD Chemicals® #: 204886-250UG.