312 



LIGHT AND LIFE 



the rate constant (compared with that at 0.05 M concentration) was increased 

 l)v more than ;")()"„. With (onceiitrations ol less than 0.01 M tlie rate constant 

 decreased again. 



Recalling the complications that phosphate may cause in certain enzyme 

 .systems, we ran anotlier series of experiments using Tris buffer and found 

 essentially the same results. As a further check we tried barbital buffer but, 

 for solubility reasons, could work only at relatively low concentrations. Here, 

 again, a striking change was observed in the activity of the enzyme, depend- 

 ing on the concentration of the buffer. 



These results are summarized in Figure B, which is self-explanatory. The 

 differences in activity of the luciferase are in no way due to changes in p\l 

 of the buffers on dilution, for this was especially looked into. 



O 

 O 



2.0 



< 1.5 



O 

 o 



UJ 

 < 



> 



< 



_J 

 LU 



1.0- 



0.5 



0.0 



0.3 



It is very evident from these results that not only the kind of buffer used, 

 but its concentration as well, must be carefully controlled when studying the 

 kinetics of this luminescent reaction. 



