Photoaffinity labeling of whole cells by flashed light: a simple apparatus for high-energy ultraviolet flashes

A simple apparatus for the photolysis of affinity labels is described. A commercial quartz tube produces high-energy flashes (wavelength from 200 to 1000 nm). A single flash is normally sufficient to activate photoaffinity labels in the presence of cells. Flash photolysis has several advantages over continuous irradiation, e.g. there is no need for cooling and photolabeling may be performed after different preincubation periods. The above apparatus is therefore suitable for investigations on time-dependent uptake of substrates by intact cells. Examples are demonstrated by photoaffinity labeling of rat liver cells by [3H]cyclosporin-diaziridine.