374 



SCIENCE 



[N. S. Vol. XXXVII. No. 949 



ture, it seemed possible that the speed of the 

 coagulation might not be greatly affected by 

 temperature. 



In order to test this matter, crystallized egg 

 albumin was prepared by the method of Hop- 

 kins and Pinkus. The albumin was recrystal- 

 lized seven times; the ammonium sulfate was 

 not dialyzed out. A 5 per cent, solution of 

 this albumin was placed in quartz test tubes 

 and exposed to the light from a quartz mer- 

 cury vapor lamp. The temperature was con- 

 trolled by keeping the quartz test tubes in 

 water baths automatically maintained at vari- 

 ous temperatures and so arranged as to give 

 the tubes equal illumination. The amount 

 of coagulation was estimated by measuring 

 the amount of deposit in the test tubes after 

 centrifuging in sedimentation tubes. The re- 

 sult of these experiments indicated that the 

 temperature coefficient equals or exceeds two. 



Of especial interest is the behavior of the 

 tubes which were kept at 0° C. These tubes 

 were still clear after being exposed to the 

 light for 35 hours, while those exposed at 

 higher temperatures contained coagulum. 

 If the tubes which had been exposed at 0° C. 

 were warmed a few degrees their contents be- 

 gan to coagulate. If they were put back into 

 the ice water as soon as the coagulum began 

 to appear the reaction was reversed and the 

 tubes cleared up. This result could be ob- 

 tained only by cooling the tubes to 0° C. as 

 soon as the coagulum began to appear. 



We are dealing here with at least two reac- 

 tions, first, the change produced by the light, 

 and, second, the production of a visible coag- 

 ulum.' Only the latter has a temperature co- 

 efficient as high as two. To demonstrate this 

 it is only necessary to expose tubes at various 

 temperatures for a few hours, turn off the 

 light, remove the tubes from the bath at 0° C. 

 and place them in a warm bath. Although the 

 tubes are perfectly clear when removed from 



= In the presence of certain salts some proteins 

 in solution may be denatured by heat, but no 

 visible coagulum forms until the salts are dialyzed 

 out. Whether this has any relation to the phe- 

 nomenon here described can not be discussed at 



the ice water, a coagulum appears as soon as 

 they begin to warm up. The amount of this 

 coagulum is about the same as if the tubes 

 had been kept in the warm bath during the 

 entire period of exposure to the light. It is 

 therefore evident that the action of the light 

 is about the same at 0° C. as at the higher 

 temperatures. We are apparently justified in 

 concluding that the light produces a substance 

 which promotes coagulation and produces it 

 about as rapidly at the lower temperature as 

 at the higher, but that this substance is un- 

 able at 0° C. to bring about any visible coagu- 

 lation, at least during the time of this ex- 

 periment. Evidently the temperature coeffi- 

 cient of the light reaction is very low in this 

 case, as is the rule in light reactions. The 

 method of the experiment yielded only ap- 

 proximate results, since the tubes which were 

 kept at 0° C. and which remained clear dur- 

 ing the exposure allowed a better penetration 

 of light than those maintained at higher tem- 

 peratures in which coagulum formed. The 

 highest temperature was only 50° C 



These experiments allow an interpretation 

 of the results of Blackman and Matthei" ac- 

 cording to whom the process of photosynthesis 

 has a temperature coefficient as high as two. 

 It is of course highly improbable that a photo- 

 chemical reaction has a temperature coeffi- 

 cient which is so high. It seems much more 

 probable that in photosynthesis, as in the coag- 

 ulation above described, light acts almost in- 

 dependent of temperature in producing a sub- 

 stance which then undergoes a reaction with 

 other substances, and that it is this latter re- 

 action which has the high temperature coeffi- 

 cient. 



The time-temperature curve of the coagu- 

 lation of proteins by heat has been worked 

 out with great care by Chick and Martin.* 



= ' ' Experimental Researches on Vegetable As- 

 similation and Respiration. III. On the Effect of 

 Temperature on Carbon-dioxide Assimilation," 

 Phil. Trans. Eoy. Soc. of London, B., 197: 47- 

 105, 1904. 



* " On the Heat Coagulations of Proteins, ' ' 

 Journal of Physiology, 40: 404, 1910; ibid., 43: 

 1, 1911. 



