Oscillations in Biochemistry

Abstract

I first wish to demonstrate an oxidation-reduction reaction involving ordinary inorganic chemicals, a reaction that oscillates, not forever, just for an hour or so. This is the Zaikin-Zhabotinskii reaction whose constituents are water, sulfuric acid, sodium bromate and bromide, malonic acid, and phenanthroline ferrous sulfate. Let me quote Dr. Winfree [8]: “In this aqueous solution phenanthroline catalyzes the oxidation decarboxylation of malonic acid. The reaction oscillates with a period of several minutes, turning from red to blue where phenanthroline is reversibly oxidized. Pseudo waves sweep across the solution (in a petrie dish) at variable speed. In addition, blue waves propagate in concentric rings at fixed velocity from pacemaker centers of varying frequency. Unlike the pseudo waves, these waves are blocked by impermeable barriers. They are not reflected. They annihilate each other when they collide. The outermost wave surrounding a pacemaker is eliminated each time the outside fluid undergoes its spontaneous red-blue-red transition. Because of uniform propagation velocity and mutual annihilation of waves that collide, higher frequency pacemakers control domains which expand at the expense of domains belonging to pacemakers of lower frequency: each slow pacemaker is eventually dominated by the regular arrival of waves at intervals shorter than its period.” One can tilt the petrie dish briefly and generate spiral waves! The Zaikin Zhabotinskii reaction [9,11] is exceedingly complex; and there is dispute between experimental investigators about aspects of the reaction, such as the origin of the circular and the spiral waves and the pacemaker centers.