Optical density measurements for different concentrations of swollen - unswollen mitochondria. Isolated rat liver mitochondria were treated with high dose calcium (300 μ M) to ensure complete swelling . Subsequently treated and untreated control mitochondria were purified by free flow electrophoresis as described in . Purified control mitochondria and Ca2+-swollen mitochondria (termed M2 mitochondria in ), were mixed at different ratios and optical readings performed at 260 nm. The numbers below the columns show the ratio of unswollen/swollen mitochondria in percentages.