FURTHER STUDIES ON EOSIN HEMOLYSIS. 



By carl L. a. SCHMIDT and G. F. NORMAN. 



{From the Department of Biochemistry aiid Pharmacology of the University of 



California, Berkeley.) 



(Received for publication, May 18, 1922.) 



It is a well known fact that if a dilute solution of a photosensitive 

 substance such as eosin is added to a suspension of washed red blood 

 cells and the mixture is exposed to sunlight, hemolysis of the red cells 

 promptly takes place, while no action is observed when the mixture is 

 kept in the dark. Busck (1) and later Sellards (2) found that the 

 addition of certain substances such as blood serum and egg white to 

 solutions of photobiologic sensitizers results in decreasing or completely 

 inhibiting the toxic action, but no protection is afforded to cells by 

 the addition of glucose, starch, or gelatin. Recognizing that there 

 are fundamental differences in the chemical make-up of those sub- 

 stances which afford protection and those which do not, Schmidt and 

 Norman (3) carried out experiments to determine the relation between 

 the amino-acid content of the protein molecule and protective action. 

 They found that eosin hemolysis can be prevented by the addition of 

 tyrosine, tryptophane, and proteins which contain these amino-acids. 

 Certain other organic compounds which contain the hydroxyphenyl 

 ring also afford protection. They pointed out that the inability of 

 gelatin to protect red blood cells against eosin hemolysis is due to the 

 absence of the above essential amino-acids. As a tentative explanation 

 of this phenomenon, they consider that the protection afforded by 

 certain substances against the photodynamic effect of eosin may 

 possibly be due to the absorption of the active rays by the protective 

 substance. 



Since the publication of these experiments, we noted a striking 

 similarity between the substances which protect red blood cells against 

 hemolysis by eosin, and the substances which were found by Gortner 

 and Holm (4) to react with the Folin and Denis (5) phosphotungstic- 

 phosphomolybdic reagent to give a characteristic blue color. These 



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