IONIZATION OF PROTEINS AND ANTAGONISTIC 
SALT ACTION. 
By JACQUES LOEB. 
(From the Laboratories of The Rockefeller Institute for Medical Research.) 
(Received for publication, January 30, 1918.) 
ie 
In 1899 Wolfgang Pauli! and the writer? independently reached 
the conclusion that electrolytes when acting on proteins formed 
ion-protein compounds. The writer anticipated that these ion- 
proteins would explain the mystery of many life phenomena. He 
was especially interested in one of the most universal physiologi- 
eal actions of salts; namely, the antagonistic salt action, for which 
the annihilation of the effects of a high concentration of a salt 
with univalent cation, e.g. NaCl, by a low concentration of a 
salt with bivalent cation, e.g. CaCle, is perhaps the best known 
example. Although he and many others tried to demonstrate 
- this type of antagonism in proteins they never succeeded. It 
was a further disappointing fact that Hardy® found that globulins 
apparently form electrically neutral compounds with neutral 
salts and this seemed to harmonize with the older observations 
of Liebermann and Bugarszky. Paulit had expressed the idea 
that a low concentration of salts ionizes globulins and thereby 
causes their solution, but even he assumed not a real chemical 
combination but adsorption between the globulin and the salt. 
Meanwhile, many workers, and especially Pauli and his pupils, 
had developed a number of methods for discriminating between 
the chemical behavior of ionized and non-ionized proteins, but 
1 Pauli, W., Arch. ges. Physiol., 1899, xxviii, 314. 
2 Loeb, J., Arch. ges. Physiol., 1899, Ixxv, 303; Am. J. Physiol., 1900, 
lil, 327. 
3 Hardy, W. B., J. Physiol., 1905-06, xxxiii, 251. 
4 Pauli, Fortschr. naturwiss. Forschung, 1912, iv, 223. 
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