Since we showed quinone-dependent rescue of ATP levels under conditions of impaired mitochondrial complex I function (Figure 3) and NQO1-dependent metabolism is described to increase NAD+/NADH ratio [9], we investigated the role of quinones on cellular metabolism in cybrids harboring either wild type (WT) mitochondria or mitochondria from MELAS patients. Here, NQO1 is linked to MELAS.