408 Dr. A. Compton. The Influence of the Hydrogen 



It only remains for me to record my great indebtedness to Dr. S. G. Platts 

 for the assistance which he has rendered me throughout a considerable part 

 of this investigation. 



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Ehrlich and Sachs, " Ueber den Mechanismus der Amboceptorenwirkung," ' Berl. Klin. 



Wochschr.,' vol. 39, p. 492 (1902). 

 Markl, " Ueber Hemmung der Hamolyse durch Sake," ' Zeitschr. f. Hygiene,' vol. 39, 



p. 87 (1902). 



Muir and Browning, " On the Filtration of Serum Complement," ' Jour. Path, and Bact.,' 

 vol. 13, p. 232 (1909). 



Nolf, " Le Mecanisme de la Globulolyse," ' Annales Inst. Pasteur,' vol. 14, p. 656 (1900). 

 Sachs and Terruuchi, " Die Inaktivierung der Komplement im Salzfreien Medium," 



' Berl. Klin. Wochschr.,' vol. 44, p. 467 (1907). 

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Exper. Therap.,' vol. 20, p. 1. (1913). 



The Influence of the Hydrogen Concentration upon the Optimum 



Temperature of a Ferment. 

 By Arthur Compton, M.B., D.Sc. (N.U.I.), Imperial Cancer Eesearch Fund. 

 {Communicated by Prof. W. Bulloch, F.R.S. Beceived December 17, 1914.) 



The present investigation is an outcome of previous work,* resulting in 

 the discovery that the optimum temperature of any ferment, or ferment 

 function, occurring in a given enzymic preparation, is independent of the 

 concentration both of the substrate and of the enzyme, the duration of the 

 action being constant. To follow up this observation it was felt desirable to 

 investigate in a similar way the influence, if any, of the reaction, that is of 

 the hydrogen ion concentration of the medium, on the optimum temperature 

 of enzyme action : the more so because enzymes, as regards their activity, 

 are known to be extremely sensitive to this factor — some requiring an acid, 

 others a neutral, and others again an alkaline medium in which to act. The 

 question, moreover, is of special interest on account of the fact that 

 Sorensen, in his classical researches on the vole, of the ionic concentration of 

 the medium in activating enzymes, alludes to it, and predicts in regard to 

 it that, when investigated, the optimum temperature will no doubt be found 

 to vary with the hydrogen ion concentration of the medium.f That 



* Arthur Compton, ' Eoy. Soc. Proc.,' B, vol. 87, p. 245 (1914) ; B, vol. 88, p. 258 (1914). 

 t S. P. L. Sorensen, ' Comptes Bend us des Travaux du Laboratoire de Carlsberg,' vol. 8, 

 p. 148 (1909). 



