[Interaction of 3-[3H]-2-n-nonyl-4-hydroxyquinoline-N-oxide with submitochondrial particles of beef heart. II. Determination of the binding sites].

The binding of 3H-NQNO in submitochondrial particles was determined by measuring the radioactivity in the supernatants as well as in the sediments after centrifugation of particles suspensions containing different amounts of 3H-NQNO. From the binding data Scatchard plots were constructed showing a large amount of aspecific binding depending on the particles preparation and concentration. In the presence of saturating concentrations of either antimycin or unlabelled NQNO (2-n-Nonyl-4-hydroxy-quinolinee-N-oxide) that remove or prevent the specific binding of 3H-NQNO, it is possible to evaluate the aspecific component of 3H-NQNO binding and to subtracte it from the experimental binding data by graphyc correction according to (3). The straight line from the corrected points gives the specific binding parameters: number of specific binding sites: about 0,5 moles 3H-NQNO/ moles cytochrome b and KD= 50 nM.