Determination of low levels of 4-fluorophenylalanine incorporation into proteins.

This paper describes a rapid method for the determination of low levels of 4-fluorophenylalanine biosynthetically incorporated into proteins. Precolumn derivatization with phenylisothiocyanate followed by reverse-phase high-performance liquid chromatography enables determination of the amino acid composition of the protein as well as accurate detection of a 1-3% substitution of phenylalanine by fluorophenylalanine.