We describe adsorption and identification of the binding sites of [Ru(NH3)(6)](3+) (RuHex) molecules in a closely packed monolayer of a 13-base ss-DNA on Au(111) electrodes by electrochemical in situ scanning tunneling microscopy (STM), cyclic voltammetry and interfacial capacitance data. In situ STM at single-molecule resolution shows that RuHex adsorbs only at the domain borders and near defects. Together with the electrochemical data that show a negative redox potential shift for RuHex adsorbed to DNA strands, this strongly suggests that RuHex binds only to the exposed phosphate groups in the DNA backbone.
Grubb, M., Wackerbarth, H., Wengel, J., & Ulstrup, J. (2007). Direct imaging of hexaamine-ruthenium(III) in domain boundaries in monolayers of single-stranded DNA. Langmuir, 23(3), 1410-1413. https://doi.org/10.1021/la062555z