The amino-acid composition of the protein material in soil.

Recent work (Kojima, 1947 a; Bremner, 1949) has shown that a considerable fraction of the organic nitrogen of soil is in the form of protein, about onethird of it being liberated as Oc-amino nitrogen by acid or alkaline hydrolysis. No method of separating this protein material from other soil constituents has yet been found and information about its amino-acid composition is scattered and incomplete. The following amino-acids have been isolated as hydrolysis products of soil organic matter: leucine (Suzuki, 1906-8; Robinson, 1911; Lathrop, 1917; Kojima, 1947 b), isoleucine (Robinson, 1911; Kojima, 1947 b), valine (Kojima, 1947 b), alanine and proline (Suzuki, 1906-8), arginine and histidine (Schreiner & Shorey, 1910a, b; Lathrop, 1917; Tokuoka & Dyo, 1937), lysine (Shorey, 1913; Lathrop, 1917), aspartic acid (Suzuki, 1906-8; Kojima, 1947 b) and tyrosine (Lathrop, 1917). The presence of large amounts of extraneous material in soil hydrolysates makes preparative work so difficult that few workers have attempted more than qualitative isolation of some of the amino-acids present. In consequence the results obtained by isolation are too limited to permit deductions regarding the amino-acid distribution in soil. The object of the present investigation was to identify the various amino-acids liberated by hydrolysis of soil protein and to determine whether or not the proteins in different soils are similar in their amino-acid composition. Themethod used for aminoacid analysis, that of partition chromatography on paper, permitted a comparison of the amino-acid distribution in a variety of soils. Preliminary results of this work have already appeared (Bremner, 1950). MATERIALS, METHODS AND RESULTS