title: Polycation induced potential dependent structural transitions of oligonucleotide monolayers on Au(111)-surfaces.
abstract: We have studied self-assembled molecular monolayers (SAMs) of several 3'-C3-SH conjugated single-strand (ss) and double-strand (ds) 20-base oligonucleotides (ONs) immobilized on single-crystal, atomically planar Au(111)-electrode surfaces in the presence of the triply positively charged base spermidine (Spd). This cation binds strongly to the polyanionic ON backbone and stabilizes the ds-form relative to the ss-form. A combination of chemical ON synthesis, melting temperature measurements, cyclic voltammetry (CV), and in situ scanning tunneling microscopy (STM) in aqueous biological buffer under electrochemical potential control was used. Spd binding was found to increase notably the ds-ON melting temperature. CV displays capacitive features associated with ss- and ds-ON. A robust capacitive peak around -0.35 V versus saturated calomel electrode (SCE), specific to ds-ON and highly sensitive to base pair mismatches, was consistently observed. The peak is likely to be caused by surface structural reorganization around the peak potential and located close to reported peak potentials of several DNA intercalating or covalently tethered redox molecules reported as probes for long-range electron transfer.
authors.affiliation: Department of Chemistry, Building 207, and Nano•DTU, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Princia
authors.initials: P
authors.lastname: Salvatore
authors.forename: Kasper K
authors.initials: KK
authors.lastname: Karlsen
authors.forename: Allan G
authors.initials: AG
authors.lastname: Hansen
authors.forename: Jingdong
authors.initials: J
authors.lastname: Zhang
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Nichols
authors.forename: Jens
authors.initials: J
authors.lastname: Ulstrup
mesh_terms: D001483:Base Sequence; D017931:DNA Primers; D055664:Electrochemical Techniques; D006046:Gold / Q000737:chemistry*; D016252:Microscopy, Scanning Tunneling; D009690:Nucleic Acid Conformation; D011073:Polyamines / Q000737:chemistry*; D000071228:Polyelectrolytes
chemical_list: D017931:DNA Primers; D006046:Gold; D011073:Polyamines; D000071228:Polyelectrolytes