The peroxidase-NADH biochemical oscillator: experimental system, control variables, and oxygen mass transport

Experimental control variables are defined and characterized to provide good reproducibility of oscillatory behavior, and allow other investigators to perform additional studies under consistently defined conditions. Fifteen variables are recognized and described. Oxygen mass transport has a large effect on the overall appearance of the oscillation, and is quantitatively related to stirring and several other variables. These conditions combine to yield a single, experimentally measurable oxygen mass-transport constant. Stirring is controlled with precision motor which is used to explore the mass-transport constant and mixing time as a function of stirrer rotation rate. Oscillatory behavior is examined under identical conditions with and without the modifiers Methylene Blue and 2,4-dichlorophenol (DCP). Omission of DCP from the system does not appreciably change oscillatory behavior under the specified conditions. Slightly damped oscillations are maintained for six hours. The acidic degradation of NADH is significantly affected by illumination from the deuterium lamp used in UV-visible absorption measurements. The importance and value of an analytical approach to this complex system is emphasized throughout.