Scientists developed a lab method that uses a special UV detector with HPLC to quickly tell apart small protein pieces (peptides) that contain the aromatic building blocks phenylalanine, tyrosine, or tryptophan. They showed it works on opioid fragments and a sleep‑related peptide, but the work is purely about identifying these molecules, not about how they affect health.

Diode-array UV detection has been adapted for analysis of opioid peptides and their metabolic fragments differing in aromatic amino acid content. In combination with high-performance liquid chromatography, the technique allowed a direct and rapid discrimination between peptides containing phenylalanine, tryptophan and tyrosine, or a combination of these residues. Enkephalin fragments with either tyrosine or phenylalanine, or both, were identified after digestion of the pentapeptide with proteolytic activity recovered from human cerebrospinal fluid. The N-terminal tyrosine-containing fragment of dynorphin A was identified after hydrolysis of the peptide by a cerebrospinal fluid endopeptidase. The study was extended to the analysis of some non-opioid peptides. The Tyr1 analogue of delta-sleep-inducing peptide was easily distinguished from the authentic compound with a tryptophan at the N-terminus. Results indicated that the technique was useful for discriminating between dipeptides differing in aromatic residues that were unresolved by high-performance liquid chromatography.