important effects of cations in increasing the binding and regulating the equilibria of receptor association-dissociation were observed when these studies were conducted , not in the tris-hcl buffer commonly used in opioid binding assays , but in n-tris [ hydroxymethyl ] -methyl-2-aminoethanesulphonate ( k+ ) buffer ( tes-koh ; 10 mm , ph 7.5 ) : it was found that ionic species of tris can substitute for divalent cations .
C0007447
cations
C0007448
divalent cations