Purification of a Crude Mitochondrial Fraction by Density‐Gradient Centrifugation

Most mitochondria prepared by differential centrifugation are contaminated to some extent by lysosomes, peroxisomes, tubular Golgi membranes, and small amounts of endoplasmic reticulum. Density gradient centrifugation using a variety of density media--sucrose, Percoll, Nycodenz, Iodixanol--is described here and is used to prepare purer fractions of mitochondria. The resulting gradient can be analyzed for three marker enzymes: succinate dehydrogenase (mitochondria), b-galactosidase (lysosomes), and catalase (peroxisomes).