1158 



BIOLOGICAL EFFECTS OF RADIATION 



attempt was made to segregate the effective rays of the ultra-violet or to 

 determine their intensity and the amount of absorption responsible for 

 the effect produced. Too often no attempt was made to control experi- 

 mental conditions, such as temperature, hydrogen ion concentration, 

 evaporation, etc. 



The preparation of crystalline enzymes as reported by Sumner and 

 by Northrop naturally removed a great obstacle in studying enzyme 

 chemistry. Previously, although very active enzymic preparations were 

 made, there was always the question of the role that unknown impurities 



1.0 



0.8 



0.6 





0.4 



0.2 



0.05 

 



M 



180 



220 260 300 340 

 Wave-length in m}i 



380 



played in producing various experi- 

 mental results. In irradiation, the 

 question of protective action and 

 absorption by these impurities is a 

 very important one, and might 

 appreciably modify the results ob- 

 tained from an impure preparation. 

 However, the question of the crys- 

 talline nature of enzymes has not yet 

 been proved to the satisfaction of all 

 investigators. In any case, great 

 strides have been made in the prep- 

 aration of more active enzymes and 

 in purification procedures. 



Kubowitz and Haas (50), at 

 Warburg's suggestion, determined the 

 absorption spectrum and destruction 

 Fig. 1.— The outlined curve shows the ^^^ve of purified urease. They were 



absorption spectrum of urease as directly ^ i i i 



measured, the crosses designating the unable to prepare crystals, but they 

 points where the absorption has been obtained just as active a preparation 



calculated from the inactivation measure- i i n t i 



Haas, as that reported by Sumner. Light 

 sources used were a mercury-arc lamp 

 and various metallic spark sources. A monochromator served to split 

 up the light with fluorspar or quartz optics, and the intensity of each 



o 



wave-length employed, ranging from 1960 to 3660 A, was measured by 

 means of a bolometer. The curve of the absorption spectrum of the 

 urease coincided with the curve of the destruction of the enzyme, there 

 being a slight destruction of urease activity at 2650 A, with a very rapid 



o 



destruction by wave-lengths shorter than 2500 A (see Fig. 1). 



Hussey and Thompson (36) irradiated a pepsin solution made from 

 granular pepsin dissolved in water acidified to pH 4.4. with 0.1 M HCl 

 for periods of 1, 2, 3, and 4 hr., with a quartz-mercury-vapor lamp. 

 (The experimental arrangements were as previously described for Thomp- 

 son and Hussey, 89.) The enzyme was inactivated by the irradiation, 

 and they concluded that the effective radiations were those of the ultra- 



ments. (After Kubowitz and 

 Biochem. Zeitsch. 257: 337-343. 1933.) 



