EFFECT OF RADIATION ON PROTEINS 309 



by calculation, that the loss of charge of the colloidal particles is propor- 

 tional to the energy absorbed in the sol as a whole for both beta rays and 

 X-rays. For equal absorption of the sol as a whole the absorption of 

 X-rays by the colloidal particles, in the case of both eerie hydroxide 

 sol and colloidal copper, will be greater than for beta rays. The mass 

 coefficient of X-ray absorption for copper and cerium is about 40 times 

 that of water and for beta radiation about twice that of water. Since 

 the effect is the same for the two types of radiation, this indicates that 

 the discharge of the colloid is due to ionization of the solvent, not to 

 ionization of the colloidal particles. The fact that only positively charged 

 suspensoids are coagulated is attributed to the mobility of the electrons 

 formed in the ionization of water. The positive ions formed would be 

 too large to penetrate the skin of solvent molecules surrounding each 

 colloidal particle, and discharge it, as could be done by the more mobile 

 electrons. 



Similar effects are reported by Fernau and Wolfgang (22) for both 

 eerie hydroxide sol and ferric hydroxide sol. A fall in viscosity followed 

 by a rise in viscosity with gel formation followed radiation by beta and 

 gamma rays, or by gamma rays only, though the effect was more marked 

 when beta rays were present. In general, it may be stated, therefore, 

 that X-rays and radium rays will produce aggregation in positively 

 charged suspensoids, probably as a result of the discharge of the charged 

 particles by the electrons freed in the ionization of the solvent (water), 

 and will disperse negatively charged suspensoids making them more 

 stable. The effect of ultra-violet radiation on suspensoids is less definite. 

 The results reported so far indicate a slow coagulating effect independent 

 of the charge on the colloid which is attributed to the absorption of H+ 

 and 0H~ ions formed by ultra-violet radiation which is not short enough 

 to liberate electrons. 



EFFECT OF RADIATION ON EMULSOIDS 



Proteins are emulsoid colloids and may be charged either positively 

 or negatively as their charge is due to ionization of the salts formed with 

 acids and bases. They differ in their degree of hydration and the dis- 

 tinction between globulins and albumins is made on the basis of solubility. 

 Globulins are hydrated only when they are charged so that salt-free 

 globulin at the isoelectric point is nonhydrated and precipitates. Albu- 

 mins are hydrated independently of their charge so that they stay in 

 solution even at the isoelectric point, although at this point they are in a 

 condition of minimum hydration. Globulins therefore are distinguished 

 from albumins by their physical properties and are defined as proteins 

 not soluble in water but soluble in acid, alkaH, and dilute neutral salt 

 solutions. This makes it difficult to distinguish between globulins and 

 denatured albumins as a denatured albumin is no longer soluble at the 

 isoelectric point. 



