What is cardiolipin? Cardiolipin is a specialized phospholipid found primarily in the inner mitochondrial membrane. Think of it as part of the structural foundation that keeps the mitochondrial energy-producing machinery organized and functioning properly. It helps stabilize the proteins involved in the electron transport chain (ETC), supports formation of respiratory-chain supercomplexes, helps maintain mitochondrial membrane architecture, and is particularly important for Complex IV and ATP synthase function. When cardiolipin becomes oxidized or its organization deteriorates, mitochondrial efficiency can decline. Electron leakage and reactive oxygen species can increase, membrane structure becomes less stable, and ATP production may suffer. SS-31: cardiolipin is basically its home turf This is where SS-31 (elamipretide) becomes especially interesting. SS-31 is a mitochondria-targeting tetrapeptide with an affinity for cardiolipin in the inner mitochondrial membrane. Rather than functioning primarily as a conventional free-radical scavenger, its interaction with cardiolipin appears to influence the membrane environment and mitochondrial protein function. A simplified way to picture it is: SS-31 → cardiolipin interaction → improved inner-membrane organization/function → more efficient electron transport → improved mitochondrial bioenergetics This can help explain findings associated with SS-31 such as improved electron-transfer efficiency, reduced pathological ROS production, preservation of cristae structure, and improved ATP-generating capacity under mitochondrial stress. Importantly, saying SS-31 simply "repairs cardiolipin" is an oversimplification. It's more accurate to say that SS-31 interacts with cardiolipin and helps normalize cardiolipin-dependent mitochondrial membrane function. NAD+: important to mitochondria, but it doesn't target cardiolipin NAD+ works very differently. NAD+ is a metabolic coenzyme and electron carrier. During cellular metabolism: