Probing the metal-ion-binding strength of the hydroxyl group

Studies have demonstrated that for monodentate primary binding sites the intensity of the hydroxyl-metal-ion interaction increases with the decreasing charge present in the coordinating atom. With regard to biological systems the observations made with hydroxyacetate are certainly of more relevance. Despite the negatively charged carboxylate group, which constitutes the primary binding site, still formation degrees of 71%, 75%, and 91% are reached for Mg((HOAc)cl ⁺, Mn(HOAc)cl ⁺, and Zn(HOAc)cl ⁺, respectively. A further point that warrants emphasis is the observation that with N-hydroxyethylglycinate (HOGly ^-), which offers the bidentate glycinate-like unit as the primary binding site, participation of the hydroxyl group in metal-ion coordination increases dramatically, leading in general to formation degrees of above 99.5% for the M(HOGly) ⁺ species. It is hoped that the presented results initiate searches for metal-ion-hydroxyl group interactions in proteins, but especially in nucleic acids.