172 



PROTEINS OF SEA URCHIN EGG 



that the intrinsic viscosity of the protein fraction isolated by 

 precipitation by 50% saturation with ammonium sulfate does not 

 vary upon fertilization, thus indicating that no appreciable 

 changes of shape and; or hydration of these protein molecules 

 occurs at fertilization. However, the increase of viscosity induced 

 by urea was considerably greater in the fraction extracted from 

 fertilized than in the one from unfertilized eggs, and a greater 



5 . 10 15 20 25 30 

 Time o[ incubahon in minutes 



Fig. 2. Release of nonprotein N from the fraction precipitated at 50% 

 saturation of ammonium sulfate from an extract of unfertilized (^) and 

 fertilized (•) eggs of Arbacia lixiila during trypsin digestion. (Calculated 

 from tlje data of Giardina and Monroy.) 



amount of phenolic groups was exposed in the former than in the 

 latter as a result of this treatment (Ceas, Impellizzeri, and Mon- 

 roy, 1955). 



These experiments give evidence that, although no changes in 

 the molecular configuration of the proteins of our fraction after 

 fertilization has been demonstrated thus far, these molecules 

 seem to undergo some sort of internal reaiTangement. The ex- 



