On the Synthesis of a32P-Labelled Edman Reagent for the Sensitive Identification of Amino-Acid Derivatives

A phosphorus-32 containing derivative of phenylisothiocyanate was prepared to increase the sensitivity of amino-acid sequence determination. The respective compound 2-(4-isothiocyanatophenoxy)-1,3,2-dioxaphosphinane 2-oxide showed about the same reactivity, stability, and polarity as the Edman reagent itself. A repetitive yield of 94% was obtained in the stepwise degradation of insulin B chain using a solid phase sequencer. The synthesis of this radioactive reagent was achieved within 5 h but with a specific activity of 1 Ci/mol. Eight amino acids were reacted with the 32P-labelled reagent and identified by autoradiography after two dimensional thin-layer chromatography.