Kaempferol (3, 5, 7, 4'tetrahydroxyflavone) inhibited the rate of state 3 substrate oxidation, but not the state 4 rate. This, along with the kaempferol inhibition of substrate-driven calcium-phosphate deposition, provided evidence that kaempferol was acting specifically on the phosphorylation mechanism and not on electron transfer. Kaempferol, however, did not inhibit ATP-driven contraction wh...