tokens: Potato mitochondria were prepared from 2 kg of tubers in batches of 200 g with 200 ml of a homogenization buffer containing 0 . 4 M mannitol , 25 mM MOPS ( pH 7 . 8 ) , 1 mM EGTA , 8 mM cysteine and 1 mg / ml fatty acid - free BSA .