2l6 E. C. SLATER, M. J. BAILIE AND J, BOUMAN 



"total DPN" over and above (DPN ++DPNH). Since, however, we have 

 used Purvis' procedure with only minor modifications, we did not think 

 it so likely that his results were due to an analytical error. A few prepara- 



TABLE IV 



Percentage of Rat-Liver Mitochondria Preparations Containing 



"Extra DPN" 



Purvis [ii] Present work 



No. of preparations 63 48 



Percentage with ''Extra DPN" 



less than — 0-4 /xmole/g. protein 



between — 0-4 and o /.tmole/g. protein 



o and 0-4 /nmole/g. protein 



0-4 and 0-8 /imole/g. protein 



more than 08 /imole/g. protein 



99 99 



TABLE V 



Effect of Added Substrate (90 sec. at 0°) on Forms of Diphosphopyridine 

 Nucleotide in Rat-Liver Mitochondria 



Mitochondria suspended in 018 m sucrose. Unpublished results of Dr. J. L. 

 Purvis, some of which were reported by Slater and Hiilsmann [29]. Values in 

 jLtmoles/g. protein. 



* Total DPN minus (DPN" + DPNH). Total DPN determined by incubation 

 in absence of substrate with dinitrophenol at 30 . 



tions gave results resembling those of Purvis. Table IV shows that whereas 

 Purvis found that 90% of his preparations contained more than 0-4 

 /umole/g. protein "extra DPN", only 2o"o of our preparations contained 



