Adaptation of an Inexpensive Ultraviolet-Visible Spectrophotometer for Enzyme Kinetic Work

Abstract

A Perkin-Elmer Model 202 spectrophotometer was modified to permit sensitive recording of absorbance changes with time by installing a retransmitting slidewire internally. The slidewire, which may be of a standard commercial type, was supplied with an exciting voltage from a battery-powered external circuit consisting of a fixed resistor and two ten-turn potentiometers to permit the use of a variable scale expansion. The output of the slidewire was connected directly to a self-balancing recording potentiometer of a type in common use. This adaptation makes possible an amplification of pen response by a factor of more than four without exceeding the capabilities of the spectrophotometer, It does not interfere with the normal function of the instrument in recording spectra. The modified instrument has been used in the kinetic analysis of several enzyme-catalyzed reactions.

This work was supported by funds made available from a National Science Foundation research grant.