Duplex Healing of Selectively Thiolated Guanosine Mismatches through a Cd2+ Chemical Stimulus.

ABSTRACT

The on-column selective conversion of guanosine to thioguanosine (tG) yields modified oligomers that exhibit destabilisation over the fully complementary duplex. Restoration to a stabilised duplex is induced through thio-directed Cd2+ coordination; a route for healing DNA damage. Short oligomers are G-specifically thiolated through a modified on-column protocol without the need for costly thioguanosine phosphoramidites. Addition of Cd2+ ions to a duplex containing a highly disrupted tG central mismatch sequence, 3'-A6 tG4 T6 -5', suggests a (tG)8 Cd2 central coordination regime, resulting in increased base stacking and duplex stability. Equilibrium molecular dynamic calculations support the hypothesis of metal-induced healing of the thiolated duplex. The 2 nm displacement of the central tG mismatched region is dramatically reduced after the addition of a chemical stimuli, Cd2+ ions, returning to a minimized fluctuational state comparable to the unmodified fully complementary oligomer.