242 



J. TIBBS 



inhibition was increased only slightly, but cyanide became very ef- 

 fective. It was found that whilst \0~-M NaF inhibited the optical den- 

 sity change, 10- 2 M NaCl and 10" 2 M NaCN had no effect. Unfortu- 

 nately the experiment could not be rounded off readily by making 

 measurements in 10 _1 M salt solutions since the salt itself, at this con- 

 centration, caused some slight optical density changes which confused 

 the interpretation. 



Measurements were always made within a few hours of isolation of 

 the preparation. This was quite essential since five preparations which 

 showed the optical density change in freshly prepared suspensions 

 were quite inactive after storage overnight at 2°C. Such storage re- 

 sulted in no loss of enzyme activity, and therefore it would appear 

 that this deterioration on storing was the result of some structural 

 disintegration. Flagella and certain kinds of sperm tails are, of course, 



0.060 



| 2 3 4 5 6 



CONCENTRATION OF Mg + + (mM) 



Fig. 4. Effect of Mg++ on the reduction in optical density at 520 m /t 

 obtained 20 min after addition of ATP to perch sperm tails (same prepara- 

 tion as illustrated in Fig. 2) in presence of EDTA. # , no EDTA; A, 1-25 

 mM EDTA; ■, 2.5 mM EDTA. 



