For interphase synchronization, HeLa cells were synchronized with 2 mM thymidine for 19 h, and these interphase cells were harvested. For mitotic synchronization, HeLa cells were treated with 2 mM thymidine for 19 h, followed by a 9 h release in fresh medium, allowing the cells to enter the mitotic phase. Mitotic cells were then harvested by mitotic shake-off. Crude mitochondria were subsequently isolated from both the harvested interphase and mitotic cells. The mitochondrial samples were directly subjected to LC-MS/MS analysis.