membrane aggregation induced by either divalent or trivalent cations followed saturation kinetics with increasing cation concentration and the apparent dissociation constants of these cations for the membranes were estimated to be at 4-6 mm for divalent cations ( ca2+ , mn2+ , and sr2+ ) and 1-2 mm for trivalent cations ( lu3+ , tb3+ , and la3+ ) .
C0007448
divalent cations
C0007447
cations