A Two-Dimensional System for the Separation of Ammo-Acids and Peptides on Paper

A RAPID, reproducible, semi-quantitative assay of the amino-acid composition of peptides is of great value in amino-acid sequence studies. Many of the common techniques of paper chromatography present difficulties in the subsequent quantitative estimation of the amino-acids. Dixon et al.¹ have described the separation of amino-acids by use of high voltage paper electrophoresis at pH 3.6, followed by paper chromatography in n-propanol-pyrophosphate buffer. Using electrophoresis at pH 2.2 (4 per cent v/v formic acid, 0.3 per cent pyridine), followed by chromatography in n-butanol; n-butyl acetate; acetic acid; water (19:1:5:25), we have obtained a separation of the amino-acids (Fig. 1) which is rapid and reproducible. We have also found this system useful in the comparison of peptides from a series of proteolytic digests.