Isethionic acid is a calcium binder and anionic detergent that enhances mitochondrial calcium binding capacity by competitively binding to calcium binding sites on the outer mitochondrial membrane. Isethionic acid can inhibit calcium-activated mitochondrial respiration. Isethionic acid inhibits barnacle (Balanus amphitrite) larvae with LC50s of 23 µg/mL (24 h) and 17 µg/mL (48 h), respectively. Isethionic acid can inhibit the attachment of barnacle larvae (complete inhibition at 10 µg/mL) and regulate mitochondrial calcium transport, and can enhance ATP-dependent calcium uptake at high calcium concentrations. Isethionic acid can be used to study the mechanism of mitochondrial calcium metabolism.