Identification of amino acid phenylthiohydantoins by multicomponent analysis of ultraviolet spectra.

Mixtures of amino acid phenylthiohydantoins ( PTHs ) can be identified and quantitated by multicomponent analysis of their ultraviolet spectra. For this analysis, the direct absorbance spectra were converted to their first derivatives. Then the multicomponent analysis routine resident in the spectrophotometer was used. The entire process requires less than one minute. Mixtures of two amino acid phenylthiohydantoins with extreme spectral similarity were accurately quantitated with the method. (We used mixtures of PTH-Asp-PTH-Glu and PTH-Ile-PTH-Leu.) The ability to identify amino acid phenylthiohydantoins by analysis of their ultraviolet spectra may provide a simple method for confirmation of the identification of the amino acid PTH obtained during protein sequencing.