EFFECT OF RADIATION ON PROTEINS 315 



increase in the number of particles on both sides of the isoelectric point 

 so that the formation of aggregates after radiation is independent of 

 the charge on the particles. 



As X-rays and gamma rays are so little absorbed by protein solutions, 

 it requires days of radiation to produce a measurable degree of denatur- 

 ation, whereas short exposures to ultra-violet radiation will produce 

 a marked effect. 



Viscosity, pH and Other Changes. — Fernau and Pauli (20) found that 

 protein solutions were more acid after exposure to radium. Wels (59) 

 and Wels and Thiele (62) state that unbuffered protein solutions, exposed 

 to X-rays, are made more acid on the alkaline side of the isoelectric point 

 and more alkaline on the acid side. 



The viscosity of serum albumin is increased only at the isoelectric 

 point after exposure to X-rays. Serum globulin shows an increase on 

 both sides of the isoelectric point, but it is necessary to radiate six hours 

 or more to produce a perceptible change (38, 59, 62). 



The results with X-rays and gamma rays are not so extensive as 

 those reported with ultra-violet radiation, but as far as they go they 

 show that the same effect is produced by all three types of radiation, 

 i.e., they all denature proteins and decrease their solubility. The small 

 absorption of X-rays and gamma rays makes the effects produced by 

 them less pronounced unless a very long radiation is given. 



GENERAL CONCLUSIONS 



In regard to suspensoids it can be stated that positively charged 

 lyophobe suspensoids precipitate and positively charged lyophile sus- 

 pensoids set to a gel when radiated by X-rays, or by the beta and gamma 

 rays of radium. 



Emulsoid colloids, such as proteins, are denatured by ultra-violet 

 radiation. The denaturation occurs whether the colloid is positively 

 or negatively charged, whether it is radiated in oxygen or nitrogen. As 

 far as present results go, they indicate that similar effects are produced 

 by X-rays and by beta and gamma rays, although only after a prolonged 

 radiation and possibly by an entirely different mechanism. After 

 denaturation, proteins flocculate if brought to the isoelectric point and 

 are more easily precipitated by salts, alcohol, or heat. This decrease 

 in solubility is more marked in albumins as is also the accompanying 

 increase in absorption. Denaturation is accompanied, or followed by, 

 an increase in viscosity and decrease in surface tension which are more 

 marked in globulins. 



There is good evidence, in the case of suspensoids, for believing that 

 the effect of X-rays, beta rays, and gamma rays is primarily due to an 

 ionization of the solvent and that subsequent interaction of electrons 

 with the positively charged suspensoid particles brings about precipi- 



