Description General description Native, human, activated C1s complement component. Present in human serum at 31 µg/ml. Non-activated C1s is found in circulating blood plasma as a Ca2+-dependent dimer in association with one C1q molecule and two C1r molecules to form the first component of complement (C1). Ensuing C1q binding to classical pathway activators, each C1r protein is cleaved to form activated C1r enzyme. Dimeric C1r enzyme cleaves, and thus activates, each C1s molecule into two disulfide-linked fragments of M.W. 59,000 and 28,000. The 28,000 peptide contains the C1s enzymatic active site. Activated C1s continues activation via the classical pathway by cleaving, and thus activating, C2 and C4. Native, human, activated C1s complement component. Present in human serum at 31 µg/ml. Nonactivated C1s is found in circulating blood plasma as a Ca2+-dependent dimer in association with one C1q molecule and two C1r molecules to form the first component of complement (C1). Ensuing C1q binding to classical complement pathway activators, each C1r protein is cleaved to form activated C1r enzyme. Dimeric C1r enzyme cleaves, and thus activates, each C1s molecule into two disulfide-linked fragments of M.W. 59 kDa and 28 kDa. The 28 kDa peptide contains the C1s enzymatic active site. Activated C1s continues activation via classical pathway by cleaving, and thus activating, C2 and C4. Packaging 250 μg in Plastic ampoule Please refer to vial label for lot-specific concentration. Warning Toxicity: Standard Handling (A) Physical form In 130 mM NaCl, 50 mM sodium phosphate, pH 7.2. Preparation Note Prepared from serum that has been shown by certified tests to be negative for HBsAg and for antibodies to HIV and HCV. Reconstitution Following initial thaw, aliquot and freeze (-70°C). Other Notes Cooper, N.R. 1985. Adv. Immunol. 37, 151. Sim, R.B. 1981. Methods Enzymol. 80, 6.