This work is a part of an investigation concerning the influence of genetic and nutritive factors on protein composition of some leguminous plants (N~LsSON et al. 1954, !V~ELLANDER et al. 1958). The protein of legumes is of particular interest because it is synthesized from nitrogen fixed by a symbiosis between root nodule bacteria, Rhizobium, and the legume. One object of the investigation consequently is to show whether differences occur in the protein of legumes fed by symbiotieally fixed nitrogen and by nitrogenous fertilizer.
It was found necessary to study separately the different proteins in the plant material concerning amino acid composition, enzymatic degradation and so forth. It was also highly desirable to have a quantitative method for estimation of the relative amount of the proteins under investigation. The work described here deals with isolation of pea proteins, determination of their purity by means of free electrophoresis and assay of the amino acids after complete hydrolysis by chromatography according to 1VfooR~ and ST~. IN (1951). The amino acid composition of pea proteins was earlier studied by DANIELSSON and LIs (1952). However, with the methods used by these authors, partly physical and partly chemical, only a limited number of amino acids could be determined.
Pea proteins may be divided into: 1. Albumins soluble in distilled water, and 2. Globulins insoluble in distilled water. The albumin is not homogenous but consists of at least three electrophoretically separable fractions. In this work no attempts have been made to separate these fractions. The globulin fraction consists of two well-defined proteins, vicilin and legumin.
Method of preparation The three protein fractions, albumin, vicilin and legumin have been prepared chiefly according to the description formulated by DA~I~LSSO~r (1950). The preparation was made as follows: 500 g. of ripe peas (Torsdag II) were allowed to swell overnight in 1 1. of 0.1 phosphate buffer PH 7.0 which contained sodium chloride to a concentration of