A Digital pH Stat for Automated Kinetic Analysis

[摘要] A "pH stat" that spectrophotometrically monitors pH and electrolytically generates either acid or base has been developed to follow the rates of certain enzyme-catalyzed reactions. The pH is monitored by coupling a pH indicator to the main reaction. As reaction proceeds, the instrument coulometrically pulses titrant into the photometer cell as required to maintain a constant pH. Generation is accomplished with Pt and Ag-AgCl electrodes. Constant-current conditions are used so that a given number of pulses corresponds to a constant reaction interval. A series of flip-flops counts the pulses as they occur; a timing circuit records the time required to generate a set number of pulses. A reciprocal time computer provides automated readout in units of absolute enzyme activity. Initial experiments on the acetylcholinesterase system (pH 7.60) show linear enzyme dependence curves with scatter of 2% or less. The change in pH during a single cycle is less than 0.05 units and the precision for replicate samples is about 2%.

[学科分类] 过敏症与临床免疫学