Characterization of two ‘mitochondrial’ particulates from rat brain

¹ Department of Physiology, University of Kansas, Lawrence, Kansas

Two particulate fractions were isolated from a preparation of rat brain mitochondria and some of the physical and chemical properties were studied. The distinguishing physical difference was the color; the heavier, more densely packed particles (P) were dark, while the lighter, loosely packed particles (W) were almost white. The amount of (P) and (W) are approximately equal. P has a higher concentration of protein than W but the nucleic acid (RNA and DNA) concentration is about the same. The per cent water of W is slightly greater than P. The P fraction was capable of oxidative-phosphorylation with several tricarboxylic acid cycle intermediates but W had no oxidative capacity. P appears to undergo the typical ‘swelling’ of mitochondria whereas W does not. P and W both increase in amount with the neonatal maturation of the brain.