The commonly used methods for amino acid analysis of peptides and proteins, including the method of Moore and Stein, require about 10v7 to 5 x 1O-g mole of sample. However, such amounts are not always available and there is an urgent demand for new and more sensitive methods of amino acid analysis.
The most sensitive of the modern methods (down to 1O-11 to l&lo mole), which was suggested by Gray and Hartly in 1963 (1)) is based upon the luminescence of the amino acid dansyl derivatives (DNS-amino acids) in the visible region of the spectrum excited by UV light. The discovery of these fluorescent derivatives stimulated the elaboration of methods of separation of DNS-amino acids, the best of which is thin-layer chromatography (2-7). Some problems in the quantitative analysis of DNS-amino acids are considered in the paper of Seiler et al. (8).
The present paper provides a description of the design of an apparatus for the ultramicrodetermination of DNS-amino acids directly in the thin layer of adsorbant after separation.
To verify the possibility of practical application of the apparatus we investigated the kinetics of splitting of C-terminal amino acids of ribonuclease catalyzed by carboxypeptidase A. The data obtained are compared with the published results.
Two-dimensional thin-layer chromatography was performed under the optimum conditions described by Belenky et al. ( 7). BASIS OF THE METHOD According to the dynamic theory of thin-layer chromatography elaborated by Belenky et al. (9), the distribution of substance in a chroma-227