AUTONOMOUS PH OSCILLATIONS IN AN IMMOBILIZED PAPAIN MEMBRANE SYSTEM

Dynamic behaviours, particularly autonomous pH oscillations, of a papa in membrane system were investigated experimentally with the aid of nu merical simulation. The experiments were conducted by exposing one sid e of a thin papain-entrapping polyacrylamide-gel slab to an external s olution of constant substate (N-alpha-benzoyl-L-arginine ethyl ester) concentration while keeping the other side of the slab in close contac t with a flat ion-selective field-effect transistor pH-sensor. A regio n of autonomous self-sustained pH oscillations in the parameter plane of external-substrate and membrane-enzyme concentrations, established via numerical computation, was used to guide the choice of experimenta l parameters. Several sets of autonomous pH oscillations were recorded , and one of them appeared to be almost self-sustained. Experimentally observed autonomous oscillations and numerically simulated self-susta ined oscillations were compared and the causes for their discrepancies were discussed.