Rapid identification of amino acid derivatives from the sequenator

A simple procedure is described for converting thiazolinones, from the protein sequenator, to the more stable phenylthiohydantoins without using the conventional HCI conversion procedure. The thiazolinones are applied to a silica gel plate and converted to phenylthiohydantoins by heating at 140 for 5-10 min, in the presence of heptafluorobutyric acid, prior to chromatography. After chromatography, measurements of the yields of the derivatives on the plate can be made with a variable-wave-length thin-layer chromatography scanner. This is shown to be a useful adjunct for identifications.