(1) On different days, the standard protocol was repeated with the diluent containing different divalent ion concentrations.(2) In an alternative model, two pairs of the negatively charged residues would chelate two divalent cations.(3) However, EDTA is not ideal because it also binds essential divalent cations such as calcium and zinc.(4) Our observations support the claim that monovalent or divalent cations are not necessary to polymerize G-actin into F-actin.(5) Experiments with erythrocytes were repeated with either sodium sulfate or sodium nitrate replacing the divalent ion at the same concentration.
