Factor XI Inhibitor Plasma
Factor XI Inhibitor Plasma is manufactured from normal citrated human plasma depleted of Factor XI using antibodies directed to FXI immobilized on agarose beads. A polyclonal antibody inhibitory to FXI has been added to provide FXI neutralizing activity. The neutralizing antibody activity is determined by Nijmegen-modified Bethesda Inhibitor Assay and has values reported in Bethesda Units. Our Factor XI Inhibitor Plasma is produced with three levels of inhibitor titre or neutralizing activity ranging from:
Mild Factor XI Inhibitor (1-10 BU/mL)
Moderate Factor XI Inhibitor (>10-50 BU/mL)
Strong Factor XI Inhibitor (>50-200 BU/mL)
Frozen or Lyophilized formats available
Only the highest quality citrated plasma is used as starting material and in many cases the parent plasma is available as control material. Our Factor XI Inhibitor Plasma can be used for further manufacturing or research use only applications.
Frozen Factor XI Inhibitor Plasma
Product Code: INH11-DP
Presentation: Frozen Factor XI Inhibitor Plasma
Preparation/Handling: Thaw 1 ml vials in 37oC water bath for 5 minutes; for bulk volumes, thawing time will be dependent on bottle size.
Storage and Stability: Plasma is shipped frozen and should be stored below -60oC. Product is stable until date stated on vial label when stored at -60oC. Once thawed, plasma is stable for 4 hours at 2-8oC in original vial.
Certificate of Analysis: available upon request
Description of Factor XI (FXI)
Factor XI (FXI, plasma thromboplastin antecedent) is a coagulation protein produced in the liver that circulates in plasma at approximately 5 μg/mL (30 nM). The mass of FXI is 160 kDa as determined by SDS-PAGE under non-reducing conditions and 80 kDa upon reduction. FXI consists of two identical 80 kDa subunits linked by disulphide bonds. Each subunit consists of a tandem repeat of four apple domains followed by a serine protease catalytic domain. Cleavage of FXI by activated factor XII or thrombin converts each subunit into a two-chain form and generates two active sites per FXIa molecule. The mass of FXIa is 160 kDa unreduced, but upon reduction FXIa migrates as a heavy chain of 50 kDa and a light chain of 30 kDa. The catalytic site of FXIa resides in the light chain. In plasma, FXI or FXIa circulates in non-covalent 1:1 complex with high molecular weight kininogen, which acts as a cofactor in the activation of FXI by activated factor XII. The activity of FXIa is regulated by platelets and by several proteinase inhibitors including, in order of decreasing importance, C1-inhibitor, α2antiplasmin, α1antitrypsin and antithrombin. Heparin has relatively little effect on the rate of inhibition of FXIa by antithrombin. The only known natural substrate for activated FXI (FXIa) is factor IX (Christmas factor) and the only cofactor required for this reaction is ionized calcium1-3.
References and Reviews
- Wuillemin WA, Minnema M, Meijers JCM, Roem D, Erenberg AJM, Nuijens JH, ten Cate H, Hack EC; Inactivation of Factor XIa in Human Plasma Assessed by Measuring Factor XIa-Protease Inhibitor Complexes: Major Role for C1-Inhibitor. Blood 85:1517, 1995.
- DeLa Cadena R, Watchtfogel YT, Colman RW, in Hemostasis and Thrombosis, 3rd Edition, eds. RW Colman, J Hirsh, VJ Marder and EW Salzman, pp. 219-240, J.B. Lippincott Co., Philadelphia, 1994.
- Baglia FA, Seaman FS, Walsh, PN; The Apple 1 and 4 domains of Factor XI Act to Synergistically Promote the Surface-Mediated Activation of Factor XI by Factor XIIa. Blood 85:2078, 1995.