High-Resolution Temperature-Jump Measurements in Biochemistry

Abstract

Spectrophotometric relaxation methods offer an available time range from the ns- to the sec-region. They require much less material than Stopped Flow techniques but need also a very high signal resolution which is especially important in biochemical applications. Signal resolution is limited by photon noise in the short time range and by light flux instabilities in the long time range, but also by the transient response of the apparatus and transient distortions due to the perturbation method, by nonlinearities of the photodetectors, improper signal balancing, etc. A careful analysis of these errors and application of appropriate technical measures resulted in the construction of a temperature-jump apparatus with a differential signal resolution of up to 10 ppm. The effective time resolution has been improved by convolution analysis of the measured signal. In the long time range, cooling of the sample following the temperature-jump can introduce serious errors and has been corrected for by an analog deconvolution circuit. ^{1, 2, 3}