Immobilized bovine aprotinin, also known as trasylol or iniprol, is a reversible inhibitor of a range of serine proteases including trypsin, chymotrypsin, plasmin, and kallikrein. Binding occurs at a range of physiological conditions with elution of target proteases at very high or very low pH values. The agarose resin is easily removed by centrifugation or filtration and is reusable.

Immobilized Aprotinin Digestion Protocol
1. Make a digestion 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 aprotinin with at least three column volumes of binding buffer. 3. Resuspend the washed immobilized aprotinin gel in binding buffer then add the resin to your protein sample. 4. Incubate mixture with gentle agitation for 30 minutes at room temperature. 5. Separate the immobilized aprotinin from the binding reaction by centrifugation or gravity filtration. Retain supernatant as your serine protease depleted protein sample. 6. To elute bound active enzymes and regenerate immobilized aprotinin gel, thoroughly wash the resin with binding buffer then elute with 0.1M Glycine, 0.1M NaCl, pH 2.9. Collect elution into 1M Tris-HCl, pH 7.4 to restore neutral pH if desired.