Binding Behaviors for Different Types of DNA G-Quadruplexes: Enantiomers of [Ru(bpy)2(L)]2+ (L=dppz, dppz-idzo)

Polymorphic DNA G-quadruplex recognition has attracted great interest in recent years. The strong binding affinity and potential enantioselectivity of chiral [Ru(bpy)(2)(L)](2+) (L=dipyrido[3,2-a:2,3-c]phenazine, dppz-10,11-imidazolone; bpy=2,2-bipyridine) prompted this investigation as to whether the two enantiomers, and , can show different effects on diverse structures with a range of parallel, antiparallel and mixed parallel/antiparallel G-quadruplexes. These studies provide a striking example of chiral-selective recognition of DNA G-quadruplexes. As for antiparallel (tel-Na+) basket G-quadruplex, the enantiomers bind stronger than the enantiomers. Moreover, the behavior reported here for both enantiomers stands in sharp contrast to B-DNA binding. The chiral selectivity toward mixed parallel/antiparallel (tel-K+) G-quadruplex of both compounds is weak. Different loop arrangements can change chiral complex selectivity for both antiparallel and mixed parallel/antiparallel G-quadruplex. Whereas both and isomers bind to parallel G-quadruplexes with comparable affinity, no appreciable stereoselective G-quadruplex binding of the isomers was observed. In addition, different binding stoichiometries and binding modes for and enantiomers were confirmed. The results presented here indicate that chiral selective G-quadruplex binding is not only related to G-quadruplex topology, but also to the sequence and the loop constitution.