Electrochemistry and in situ scanning tunnelling microscopy of pure and redox-marked DNA- and UNA-based oligonucleotides on Au(111)-electrode surfaces.
We have studied adsorption and electrochemical electron transfer of several 13- and 15-base DNA and UNA (unlocked nucleic acids) oligonucleotides (ONs) linked to Au(111)-electrode surfaces via a 5'-C6-SH group using cyclic voltammetry (CV) and scanning tunnelling microscopy in aqueous buffer under electrochemical potential control (in situ STM). 2,2',6',2''-Terpyridine (terpy) onto which the transition metal ions Fe(2+/3+), Os(2+/3+) and Ru(2+/3+) could be coordinated after UNA monolayer formation was attached to UNA via a flexible linker. The metal centres offer CV probes and in situ STM contrast markers, and the flexible UNA/linker a potential binder for intercalation. CV of pure and mercaptohexanol diluted ON monolayers displayed reductive desorption signals but also, presumably capacitive, signals at higher potentials. Distinct voltammetric signals arise on metal binding. Those from Ru-binding are by far the strongest and in accord with multiple site Ru-attachment. In situ STM disclosed molecular scale features in varying coverage on addition of the metal ions. The Ru-derivatives showed a bias voltage dependent broad maximum in the tunnelling current-overpotential correlation which could be correlated with theoretical frames for condensed matter conductivity of redox molecules. Together the data suggest that Ru-units are bound to both terpy and the UNA-DNA backbone.
Department of Chemistry, Building 207, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
Allan G
AG
Hansen
Princia
P
Salvatore
Kasper K
KK
Karlsen
Richard J
RJ
Nichols
Jesper
J
Wengel
Jens
J
Ulstrup
D004247:DNA / Q000737:chemistry*; D055664:Electrochemical Techniques; D004566:Electrodes; D004579:Electron Transport; D006046:Gold / Q000737:chemistry*; D016252:Microscopy, Scanning Tunneling; D009841:Oligonucleotides / Q000737:chemistry*; D010084:Oxidation-Reduction; D028561:Transition Elements / Q000737:chemistry
D009841:Oligonucleotides; D028561:Transition Elements; C477371:locked nucleic acid; D006046:Gold; D004247:DNA