The stoichiometry of binding of the aurovertins to mitochondrial ATPases: revision of the molar absorption coefficient.

The purity of aurovertins A, B, and D, which inhibit the mitochondrial ATPase and show fluorescence enhancement when bound, has been determined by high-resolution proton nuclear magnetic resonance. This technique demonstrated that solvent molecules, especially water, are tightly bound to crystalline aurovertins B and D. The molar absorption coefficient for aurovertins A, B, and D at the longest wavelength maximum (367.5-369 nm) has been determined to be 38,500 liter x mol(-1) x cm(-1). This correct molar absorption coefficient should enable correct binding stoichiometries for aurovertin to ATPases to be determined.