Two Metal Ions Coordinated to a Purine Residue Tolerate Each Other Well

The catalytic sites of ribozymes generally contain two or more metal ions. Guanine is the nucleobase most often involved in binding to metal ions. The repulsion between two M2+ ions simultaneously coordinated to guanine in aqueous solution was investigated by using complex 1 (see picture; dien=diethylenetriamine, R=C2H5) as a model, for which the stability constants for the binding of Mg2+ and Cu2+ were determined.