BIOPHEN™ Factor XIa

In presence of Phospholipids (PLPs), calcium and thrombin, activated FXI present in the tested sample is able to activate Factor IX (in excess and without Factor IXa) into FIXa, that forms an enzymatic complex with its cofactor, Factor VIII:C, also supplied in the assay at a constant concentration and in excess. This complex activates Factor X, present in the assay system, into Factor Xa, which generated amount is directly related to the amount of Factor XIa to be measured. Generated Factor Xa is then measured by its specific activity on a Factor Xa chromogenic substrate (SXa-11). Factor Xa cleaves the substrate and releases pNA. Finally, there is a direct relationship between the amount of Factor XIa in the assayed sample and the Factor Xa activity generated, measured by the amount of pNA released, and measured at 405nm.