Protein S (PS) is a vitamin K-dependent glycoprotein produced in the liver and circulates at levels of 20 ug/ml in plasma. PS is a single chain molecule of 69kD that acts as a cofactor in the proteolytic inactivation of factors VIIIa and Va by activated Protein C (APC). Approximately 60% of PS in plasma circulates as a complex with C4-binding protein (C4BP). Only the uncomplexed or “free” form of PS has cofactor activity and these forms can be quantified in plasma afterprecipitating the complexed form with cold polyethylene glycol precipitation. PS is subject to cleavage by thrombin resulting in a loss of cofactor activity. Patients with deficiencies of Protein S (quantitative and qualitative) are generally believed to be at risk of vascular thrombosis.
PS in plasma and other fluids can be measured by capturing onto a microtitre plate coated with a sheep antibody which can bind free and complexed human PS. The captured PS is detected with goat anti-human PS IgG conjugated to HRP. Bound antibody conjugate activity is expressed by incubation with substrate, ortho-phenylene diamine (OPD). The color generated is proportional to the concentration of PS initially present in the sample.
Materials Supplied:Antibodies for 5x96 well plates
Kit Components:P9108-07A: PS Capture Antibody: 1x500ul Supplied as a liquid in 50% glycerol. Purified by immunoaffinity chromatography. PS IgG Pab ShxHu for coating ELISA plates.
P9108-07B: PS (HRP) Dection Antibody: 1x500ul Supplied as a liquid in 50% glycerol. Purified by immunoaffinity chromatography. PS (HRP) GtxHu for detection of captured PS.
Storage and Stability:For long-term storage, aliquot and store at -20°C. Aliquots are stable for at least 6 months at -20°C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.
