| Abstract: | 1. From the 57Fe hyperfine interaction in EPR spectra of reduced submitochondrial particles from the yeast Candida utilis, grown with 57Fe, it is concluded that all Fe-S centers in these particles detectable in spectra at 35-80 K are 2Fe-2S]2-(2-; 3-) centers. These are the centers 1 of NADH and succinate dehydrogenase, the Rieske Fe-S center and possibly center 2 of succinate dehydrogenase. 2. The signals of the reduced particles detectable only at temperatures below 20 K are 4Fe-4S]2-(2-; 3-) clusters. These are the centers 2,3 and 4 of NADH dehydrogenase. 3. EPR spectra of the 2Fe-2S]3- centers of Complex I and II, but not that of Complex III, display a great inequality of the Fe nuclei in the effective hyperfine interaction in the x-y direction. |
