BIS-CATECHOL-SUBSTITUTED REDOX-REACTIVE ANALOGS OF HEXAMETHONIUM AND DECAMETHONIUM - STIMULATED AFFINITY-DEPENDENT REACTIVITY THROUGH IRON PEROXIDE CATALYSIS

Symmetrically bis-catechol-substituted analogues (1 and 2, respectivel y) of hexamethonium and decamethonium were synthesized and investigate d as redox-activated affinity reagents toward the neurotoxin-binding s ites of the nicotinic acetylcholine receptor (nAcChR), purified from T orpedo californica electroplax. These reagents bound to nAcChR with K- d = 1.8 X 10(-8) and 2.3 x 10(-7) M for 1 and 2, respectively. In the presence of a metal, Fe(II)/Fe(III), and peroxide, both reagents produ ced a rapid and efficient half-of-sites inactivation of neurotoxin-bin ding sites in the nAcChR in a concentration-dependent manner, which pa ralleled the extent of receptor binding of the reagents. In the absenc e of Fe(II)/Fe(III) peroxide, redox-dependent inactivation occurred fo r both 1 and 2 more slowly and only at concentrations much higher (10( 3)-10(4) times) than those necessary to produce significant binding to nAcChR. However, receptor inactivation in the absence of added metal peroxide was still more efficient for 1 and 2 than observed previously for [(trimethylammonio)methyl] catechol (3), the prototypic redox-dep endent affinity reagent after which 1 and 2 were patterned. Thus, the new reagents reported are expected to provide more efficient and selec tive conditions for redox-dependent inactivation at nAcChR and other m acromolecular sites to which such reagents may be directed.