HPLC Analysis of Methylated Amino Acids : Methylated Amino Acids on HPLC

Various naturally occuring methylated amino acid derivatives were resolved on high performance liquid chromatography (HPLC), using o-phthadialdehyde as a fluorogenic reagent. We separated .$\varepsilon$-N-monomethyllysine, $\varepsilon$-N- dimethyllysine, and $\varepsilon$-N-acetyllysine from lysine derivatives. $N^{G}$-Monomethylarginine and $N^{G}$-dimethylarginine were separated from arginine derivatives. However, $\varepsilon$-N-monomethyllsine and $\varepsilon$-N-trimethyllysine, $N^{G}$, $N^{G}$-dimethylarginine and $N^{G}$, $N^{G}$-dimethylarginine were not resolved under the conditions employed. S-Methylmethionine, S-methylcysteine, and 1-N-methylhistidine or 3-N-methylhistidine were clearly separated from their reference amino acids, even though 1-N-methyl-and 3-N-methylhistidine coul not be separated.