Amino acids fluorescent thiohydantoins

Figure 14. Chromatography of a mixture of fluorescent amino acid derivatives. Each amino acid was reacted with fluorescein isothiocyanate and then converted to the thiohydantoin. The mixture, containing about 5 pmol of each derivative, was run on an Ultrasphere octyl column at pH 5.0. Detection was made with a Schoeflel FS 970 fluorometer at 274-nm excitation.

Fluorescein isothiocyanate was proposed by Maeda el al. as a fluorescent end-group reagent [218] analogous to phenylisothiocyanate in the Edman method. A procedure for the determination of free amino acids by formation of fluorescent thiohydantoins with fluorescein isothio-cytinate was reported by Kawauchi ef al. [219]. 

Figure 9. Formation of fluorescent thiohydantoins by reaction of an isothiocyanate with an amino acid. X = fluorophore.

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