30 



INFLUENCE OF TEMPERATURE ON BIOLOGICAL SYSTEMS 



and diffusion rate of both ki and k4 was identical within the Umits of ex- 

 perimental error for both sets of data. Since the data at 405 m/x. were close 

 to the noise limit, their spread was greater. Hence, the rate data pre- 

 sented here are based on the cuvette determination at 230 m^a. 



The variation of k/ with temperatures from 5° to 45°C at pH 7.5 is 

 shown in figure 3. The data at 45°C demanded working quite rapidly since 



the enzvme starts to dena- 



.1 - 



12.6 k col/mole 



ture within 5 minutes at 

 45°C. The graph of log k/ 

 against T~^ shows a linear 

 relationship within experi- 

 mental error. The slope of 

 this line shows the value of 

 AHa to be 2± 0.2 Cal/mole. 

 This value is close to those 

 obtained by Chance (3). 



As noted earlier, the con- 

 stant ki' is a combination 

 of both ki and k4 . To test 

 if the value of AHa was 

 common to both of these 

 constants, we measured pi/e 

 as a function of tempera- 

 ture in an independent set 

 of experiments. The results 

 are also plotted in figure 5. 

 Here, Pi/e, and not the log, 

 is plotted since the linear 

 scale gave a straighter line. 

 If ki and k4 both had the 

 same temperature depend- 

 ence, this line should have 

 been parallel to the T~^ 

 axis, in contrast to its exper- 

 imentally observed slope. 

 An identical set of experi- 

 ments with the flow system gave values for ki + k4 . 



An independent series of measurements was carried out at 25°C at vari- 

 ous viscosities of the suspending medium. Chemically pure glycerol was 

 mixed in appropriate proportions with buffer, distilled water and reactants. 

 The results of these measurements are summarized in figure 4. The varia- 

 tion of pi/e with fluidity (reciprocal of viscosity) is similar to that found 



7.600 ■ 

 7.550 - 

 7500 - 

 7450 

 7400 

 7350 

 7300|- 

 7 250 



Fig. 



ture. 



3. Variation of k/ and Pi/e witli tempera- 



