Synthesis and stability of N-ε-phospholysine derivatives

Abstract

N-ε-Phosphorylated lysine (pLys) residues have been understudied due to their presumed instability to withstand the conventional acidic conditions used in phosphoprotein and phosphopeptide analysis. While some efforts have been made to develop non-hydrolysable pLys surrogates, less progress has been made on developing methods to prepare authentic pLys residue and its derivatives. This study provides a synthetic route to N-ε-phosphorylated lysine models and assesses their pH-dependent stability by use of ³¹P NMR and HPLC. While the pLys models expectedly showed instability at lower pH (3.5), they showed unexpected stability in moderately acidic conditions (pH 5.0). In addition, the pLys models were sufficiently stable when analyzed utilizing HPLC gradients with an acid modifier (0.1 % TFA).