DISINTEGRATION OP VIRUSES 



37 



2 4 6 



TIME IN HOURS 



8 



10 



FIGURE 29 - LOG CONCEirTRATION OP TOBACCO 1!0SAIC VIRUS PROTEm 

 PLOTTED A3 A FniGTIOi: OP TIl^E EXPOSURE TO 6 M urea. (M.A. lAuffer, 

 j-A.c.s. 65, 1793 I1943J )' 



The reaction was f 

 urea denaturation 

 a process of the f 

 strate that the fi 

 overwhelrr.irrgly bet 

 ir.only encountered, 

 mosaic virus, the 

 fixed set of condi 

 when the data are 

 obtained by chemic 



ollowed cherr.ically in this case. This would i 

 of tobacco mosaic virus, in common with heat d 

 irst order. Again statistical procedures were 

 t of these data to the equation of a first ord 

 ter than to the equations of any other reactio 

 Just as in the case of the thermal denaturat 

 specific reaction rate for the urea denaturati 

 tions can be calculated from the slope of the 

 plotted in the manner here illustrated, whethe 

 al or turbidimetric methods. 



ndicate that 

 enaturation, is 

 used to demon- 

 er reaction is 

 n orders com- 

 ion of tobacco 

 on under a 

 line obtained 

 r the data are 



A series of experiments was carried out to determine the influence of 

 several variables upon the magnitude of the specific reaction velocity. Be- 

 cause of the convenience, the turbidimetric method was used throughout the fol- 

 lowing experiments. In the first stages of this work, Stanley and I discovered 

 that urea denaturation of tobacco mosaic virus proceeded faster at 0° C. than 

 at room temperature, but also faster at 40° C. than at room, temperature, isawden 

 and Pirie later confirmed this unusual behavior, more recently, the more ex- 

 tensive data presented in figure 30 have been obtained. The specific reaction 

 velocity is plotted against the absolute temperature. The U-shaped relationship 

 obtained is obviously a very unexpected behavior, quite contrary to the sense of 

 usual rate theory which requires that reaction velocities decrease steadily as 

 temperature decreases. Hov;ever, that this condition may be general for urea 

 denaturation of proteins is indicated by the fev/ reports available in the liter- 

 ature. Hopkins in 1930 reported that the denaturation of egg albumin bi' urea 

 has a negative differential rate temperature coefficient over the temperature 

 range to 37° C. More recently, Clark reported a positive differential rate 

 temperature coefficient for egg albumin in urea, in 1938 Diebold and juhling 

 shoT/ed that fibrinogen has a positive temperature coefficient of denaturation 

 in urea. In 1939 Drabkin reported that carboxy hemoglobin also has a positive 

 terr.perature coefficient of urea denaturation over the temperature range 20 to 

 38° G. It seems likely that in each of these cases only one horn of t.-ie tem- 

 perature rate function v/as being investigated. 



