The specific interaction between LSD and serotonin-binding protein.

Abstract

In this report, we describe the chemical interaction between lysergic acid (LSD) and serotonin-binding protein (SBP) by a three-dimensional spectroscopic technique. This instrument records simultaneously the activation and fluorescence spectra, and plots fluorescence intensity level by a series of isointensity contours. Free LSD exhibits maximum fluorescence at 435 nm with excitation maximum at 330 nm. While SBP-bound LSD shifted its fluoresence and excitation maximum to 465 nm and 375 nm respectively. These results suggest that the drug-protein interaction caused an extensive delocalization of the molecular orbital electrons and thereby lengthen the electronic conjugation of the drug molecule. Such shift was not observed when LSD was incubated with bovine serum albumin under the same condition. This technique is sensitive and requires a small volume of samples. It permits us to determine both free and bound drug in the same sample and provides us specific information about the drug and protein interaction.