Consecutive Silver(I) Ion Incorporation into Oligonucleotides containing Cytosine-Cytosine Mispairs

Herein, the consecutive incorporation of Ag^I ion into the dsDNA containing adjacent C-C mispairs is demonstrated. The melting temperature (T_m ) was 8 ^° C higher for DNA containing three C-C mispairs upon the addition of three Ag^I ions as compared to the Ag^I -free DNA, and no T_m was obtained in the presence of excess Ag^I ion, indicating a stable bridging of C-Ag^I -C upon the incorporation of the stoichiometric amount of Ag^I per C-C mispair. The circular dichroism (CD) spectra of the dsDNA showed a negative peak at ∼270 nm in the presence of excess Ag^I , implying that significant structural changes and a potential aggregation of DNA occurred. Subsequently, the Ag^I -mediated DNA strands are immobilized on Au surfaces. Their electrochemical properties are monitored using CV, EIS and SECM showing increased overpotentials and charge-transfer resistances, and decreased the rate constant in the presence of an excess of Ag^I , respectively. These results are further supported by the XPS and sulfide-Au reductive desorption measurements.