The digestion products formed by the action of papain on egg albumin.

AN ultracentrifuge study of the action of papain on egg albumin was made in this laboratory [Svedberg & Eriksson, 1933; 1934], but with the centrifugal forces and methods of measurement then available it was not possible to separate effectively the digestion products obtained. It was therefore thought advisable to use the improved apparatus now in the laboratory to extend these observations. As the ultracentrifuge data still proved insufficient for definite conclusions measurements were also made by other physical methods. Experimental procedure. The egg albumin was prepared by S0rensen's method [S0rensen, 1917; S0rensen & Hoyrup, 1918]. It was crystallized three times, dissolved and dialysed against distilled water, and then electrodialysed. The solution was evaporated in vacuo over sulphuric acid and over phosphorus pentoxide, and stored in the dry state in the dark. The papain used was Merck's Papainotinum 1: 350. Its activity was tested according to directions given by Willstatter & Grassmann [1924] and found to give results comparable with theirs. The papain activation with HCN and the treatment of the digestion mixture of papain and egg albumin were carried out in the manner recommended by Willstatter & Grassmann [1924; 1926]. All digestion was done at 400 in acetate buffer of pH 5.0. The papain solution was in each case activated at 40° for 2 hours before it was added to the egg albumin. Two different sets of concentrations of digestion mixture and protein solution were used: (a) those used by Willstatter & Grassmann forpapain activation tests (only slight digestion occurred with these proportions so they were not used in later work), and (b) those concentrations used by Willstiitter & Grassmann in egg albumin digestion. These concentrations were as follows: