ARGININE AND ARGININE-CONTAINING PROTEINS 57 



The procedures of Serra and Thomas differ in certain details 

 and, at the date of this writing, no comparison of the two has been 

 made. An advantage of the method of Thomas is that it does not 

 employ cooling in an ice bath during the reaction because of the 

 substitution of hypochlorite for hypobromite. Serra mounts his 

 sections in glycerol after several transfers through this medium and 

 he has reported that in this fashion the color, otherwise stable for 

 only a short time, is stabilized for months. 



Serra Method for Arginine and Arginine-Containing Proteins 



SPECIAL REAGENTS 



Acetic- Alcohol-Formalin Fixative. Add a few drops of glacial 



acetic acid to each 10 ml. of a mixture of 2 vol. 96% alcohol and 



1 vol. formalin. 

 1% a-Naphwl in 96% Alcohol. Store in a refrigerator. Dilute 



1:10 with 40% alcohol before use. 

 4% Sodium Hydroxide. 

 2% Sodium Hypobromite. With stirring and cooling, add 2 g. or 



approximately 0.7 ml. bromine to 100 ml. 5% sodium hydroxide. 



Store in a refrigerator. 

 40% Urea. 



PROCEDURE 



1. Fix the material in the acetic-alcohol-formalin mixture. Wash 

 well in water. 



2. Transfer to a watch glass kept at 0-5° in an ice bath, and 

 treat for 15 min. at this temperature with a mixture of 0.5 ml. a- 

 naphthol soln., 0.5 ml. 1 N sodium hydroxide, and 0.2 ml. 40% urea. 



3. Add 2 ml. 2% hypobromite, and after 3 mih. stir in 0.2 ml. 

 urea soln. and then 0.2 ml. of the hypobromite. The maximum color 

 develops in 3-5 min.; intensify it by a subsequent treatment with 

 the hypobromite for 3 min. 



4. Pass through four glycerol baths, leaving for 2-3 min. in 

 each. In glycerol the color is stable for months even at room tem- 

 perature. The fading is inhibited by storage in the cold. 



Result. An orange-red color characterizes a positive reaction. 



