A Light Intensity Measurement System for the Analytical Ultracentrifuge

Abstract

Light intensity measurements are required by absorbance, fluorescence, turbidity and low-angle light scattering detectors in order to determine the concentration distributions encountered in analytical ultracentrifugation. By using four fast analog-to-digital converters operating in parallel, a data acquisition system has been developed for the analytical ultracentrifuge that can acquire light intensity readings from three detectors (e.g. photomultipliers, avalanche photodiodes, etc.) simultaneously. For each detector, up to forty thousand intensity readings are acquired during each rotor revolution, for up to ten revolutions. Software synchronizes data acquisition with the spinning rotor. The use of continuous light sources allows simultaneous acquisition of dozens of intensity readings from all of the samples. Data acquisition is fast, allowing rapid radial scanning of samples. This data acquisition scheme is used in the Aviv Biomedical AU-FDS fluorescence detection retrofit system for the Beckman XLI analytical ultracentrifuge. It also will be used for the updated XLI absorbance system, as well as the next generation of analytical ultracentrifuge.