Ceramide content of purified intact mitochondria and inner mitochondrial membrane (IMM) as quantified by LC-MS/MS. Both fractions contain six ceramide isoforms ranging from 16- to 24- carbon units in length, with C24-ceramide being the predominant species in intact mitochondria. C16-, C18-, and C24:1- ceramide are found in near-equivalent quantities in the IMM as compared to intact mitochondria, whereas C20-, C22, and C24-ceramide are present in much lower quantities. This suggests that these latter ceramides are primarily found in the outer mitochondrial membrane. Data represent the means ± SEM, n = 4.