Separation of tryptophan from DSIP, a Trp-nonapeptide, by adsorption to aluminum oxide.

Delta sleep-inducing peptide (DSIP) has been found to induce sleep as well as extra-sleep effects. Although the presence of endogenous DSIP-like material has been demonstrated, the metabolic fate of injected DSIP has not been clarified so far. A major obstacle in monitoring degradation of DSIP has been the lack of an easy method to separate DSIP from tryptophan (Trp). Cleavage of the N-terminal Trp apparently represents the first and most important step in the metabolism of the peptide. Adsorption to aluminum oxide has been found to separate the two compounds and optimal conditions for the separation are described. Quantitative determination of the degradation of DSIP in plasma or serum is now rapidly achieved. The method should help to advance metabolic studies of DSIP. Other applications such as extraction of DSIP from solutions are also possible.