Ribosomes from rat liver mitochondria. I. Isolation procedure and contamination studies.

The isolation of 55 S particles from mitochondria has been reported. Evidence has been presented which emphasizes the importance of adequate control of contamination during preparation of mitochondria. A satisfactory mitochondrial purification method was attained through the use of radioactive microsomal fractions and electron microscopy to assess the contamination of mitochondria and ribosomes isolated from mitochondria prepared by (a) extensive washing by differential centrifugation in various media, (b) purification in continuous sucrose density gradients, and (c) sedimentation through discontinuous density gradients.