Immobilized corn trypsin inhibitor is ideal for highly specific reversible binding of Factor XIIa and trypsin in physiologic solutions. The resin is easily removed by centrifugation or filtration following the reaction and captured enzyme can be eluted with chaotropic salt. Immobilized corn trypsin inhibitor is reusable and useful for a range of applications including purification of active Factor XIIa, removal of catalytic trypsin from digest reactions, and depletion of trace residual Factor XIIa from pure zymogen preparations of Factor XII.

Immobilized CTI Protocol
1. Make a binding buffer consisting of 0.1M Tris-HCl, 0.15M NaCl, pH 7.4 (or other suitable physiological buffer such as PBS).
2. Wash desired amount of immobilized CTI with at least three column volumes of binding buffer.
3. Resuspend the washed immobilized CTI gel in binding buffer then add the resin to your protein sample.
4. Incubate mixture with gentle agitation for 5 minutes at room temperature.
5. Separate the immobilized CTI from the binding reaction by centrifugation or gravity filtration. Retain supernatant as your Factor XIIa/Trypsin depleted protein sample.
6. To elute bound active enzymes and regenerate immobilized CTI gel, thoroughly wash the resin with binding buffer then elute with 3M Sodium Thiocyanate, 0.1M Sodium Acetate, pH 5.0.
7. Remove chaotropic salt by extensive dialysis against 4mM Sodium Acetate, 0.15M NaCl, pH 5.3 (or similar appropriate storage buffer with low pH).