An inexpensive computerized enzyme kinetics system based on a Gilford spectrophotometer and an Apple IIe microcomputer

A microcomputer-controlled data acquisition system for spectrophotometric enzyme kinetics measurements has been assembled. The system uses an Apple IIe computer which is interfaced to the binary coded decimal output of a Gilford spectrophotometer. No analog-to-digital converter had to be purchased. A BASIC program which collects timed absorbance readings every 500 ms, plots the data in real time, performs a linear regression of the data to measure the reaction rate, and calculates the enzyme activity concentration is given in full. Details describing the interfacing of the computer to the spectrophotometer are presented which will permit other laboratories to readily assemble their own systems using this hardware. Kinetic data acquired by the system are highly reproducible and agree well with data processed much more slowly by manual techniques from strip chart recordings.