DISINTEGRATION OF VIRUSES 



33 



determining the manner in which the rate constant k changes with temperature 

 reduces to a determination of the change in the equilibrium constant with tem- 

 perature. Two relationships derived from elementary thermodynamics should be 

 recalled: 



and 

 Therefore, 



and In K 



-AP° = RT In K 

 Apo = AH° - TAS° 

 -Ah° + tAs° = RT In K 



R RT 



-By combining equations (7) and (10), one obtains: 



In k=con8t + Ml_Ml 1 

 R R T 



(8) 

 (9) 



Uo) 

 (11) 



Af°, As° and AH° are the standard free energy, standard entropy change, and 

 standard heat of reaction respectively. R is the gas constant and T is the 

 absolute temperature. Thus, when In k is plotted against 1 , a straight line 

 should be obtained. Its slope should be _ A-H° , where T Ah° is the stand- 

 ard heat of the reversible reaction V — ^^ V*. ""8 — This is sometimes called the 

 energy of activation. "^ 



The thermal denaturation of tobacco mosaic vims was studied at several 

 different temperatures and the specific reaction velocity for each y/aa obtained. 

 Then the log of K was plotted against the reciprocal of the absolute temper- 

 ature, as is seen in Figure 26. 



2.86 



2.90 



2.94 

 1/T '^ 10^ 



2.98 



3.02 



FIGURE 26 - VELOCITY CONSTA.V'^a FOR THERMAL DEl'ATURATION OP TOBACCO 

 UOSAIG VIRUS PROTEIN AT pH 7 PLOTTED AS A FUNCTION OF ABSOLUTE TEM- 

 PERATURE ACGORDI?K> TO THE ARRHENH'S EQUATION: UPPER CUR-'/E i^OR SYSTEM'S 

 WITH INITIAL VIRUS CONCENTRATION OF 3 mg/cc; LOVER CUR"'/li FOR SYSTEliS 

 TflTK INITIAL VIRUS CONCENTRATION OF 6 mg/cc. (K.A.I^uf f er and W.C. 

 Price, J. Biol. Ghem. 140, 509 (1941) ). 



