On the Cytochromes of Anaerobically Cultured Yeast 



229 



Removal of intact cells and gross cellular debris, 



ISminat 1000 x g. 



Centrifugation for 30 min at 4000 x g — Fraction I. 



Centrifugation of supernatant I for 60 min at 25,000 X g — Fraction II. 



Centrifugation of supernatant II for 60 min at 105,000 X g — Fraction III. 



All these operations are carried out at about 0°C. At each stage the frac- 

 tionation is followed by examination with a phase-contrast microscope. 



For the fractionation of yeast cultured anaerobically all the operations are 

 carried out under nitrogen to avoid induction by oxygen of respiratory enzymes. 



(c) Morphological and Spectrographic Properties of Fractions Isolated from 

 Aerobic Yeast 



Study of the different fractions by electron microscopy shows that fraction I 

 is a practically pure preparation of mitochrondria ; fraction II, rich in granules 

 organized in clusters and various debris, contains hardly any mitochondria; 



3-9 



3-9 



(7) 



I 3-5 



o 



"5.3-3 

 O 



3-7 

 •3-5 

 3-3 



Fig. 4. 



2 



4 



3 



5 



3-6 

 3-4 

 32 

 30 



38 

 3-6 

 3-4 



550 



600 

 A, 



550 



600 



m// 



Spectra of fractions I and III of aerobically grown yeast cells harvested 

 during the exponential phase of growth. 



A, Fractionation in polyvinylpyrrolidone 



B. Fractionation in lactose 



Curves 1, fraction 1 reduced with succinate; curves 2 and 4, fraction I reduced 

 with Na2S204; curves 3 and 5, fraction III reduced with NaaSgOi. 



