RESUMO
Aqueous solutions of lysergic acid diethylamide (LSD) are extremely sensitive to light in the near-ultraviolet region of the spectrum. This rather efficient photoreaction yields a variety of products which have very low affinity for LSD-binding sites on plasma membranes from Fasciola hepatica. Since this photoreaction may be elicited by normal white fluorescent lighting in the laboratory, it represents a potential source of error in determining the binding affinity of LSD. Utilizing this photoreactivity advantageously, [3H]LSD was used to photolabel membrane proteins. Covalent binding of [3H]LSD was shown to be a function of the duration of illumination and was inhibited by 5-hydroxytryptamine and nonradioactive LSD. Sodium dodecylsulfate (SDS) polyacrylamide gel electrophoresis of [3H]LSD labeled membranes from F. hepatica showed two proteins which were selectively labeled by the photoreactive [3H]LSD. This method of direct photolabeling with non-derivatized [3H]LSD may allow identification of LSD-binding proteins in a variety of systems.
