Polycation Induced Potential Dependent Structural Transitions of Oligonucleotide Monolayers on Au(111)-Surfaces

Abstract

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.

Redox Potentials and Electronic States of Iron Porphyrin IX Adsorbed on Single Crystal Gold Electrode Surfaces

“…Gold surfaces and gold nanomaterials are widely used in electrochemistry, fuel cells, biosensors, and drug transport. , The Au surfaces affect the electronic properties of adsorbed molecules and biomolecules. Such interactions have been mapped in detail for Au–S surface linked molecules and biomolecules − and apply broadly . Studies that directly compare different surfaces using voltammetry combined with in situ single-molecule structural mapping and computational support seem, however, needed to obtain a coherent view of the complex metalloporphyrin adsorption on metallic surfaces.…”

Electrochemical single-molecule conductivity of duplex and quadruplex DNA

“…Fig.1A illustrates photo-induced ET/HT and random "hopping" of the excess charge along the strand, interrupted by "quenching" (k 1 …k Nf ) and eventual trapping. Fig.1B 36,37 . Such signals can also show weak distance dependence and high sensitivity to base pair mismatch 37 .…”

“…Fig.1B 36,37 . Such signals can also show weak distance dependence and high sensitivity to base pair mismatch 37 . Polaron conductivity 29 is an attractive notion, as much fewer "hops" are needed, but electrochemical polaron signals have not been identified either.…”

Voltammetry and molecular assembly of G-quadruplex DNAzyme on single-crystal Au(111)-electrode surfaces – hemin as an electrochemical intercalator

“…Electron or hole "hopping", with full vibrational relaxation between each single-charge hop has emerged as an attractive mechanism for photo-induced OGN electronic conductivity. This notion is, however, faced with challenges in interfacial electrochemical ET in redox marked surface immobilized OGN molecules [11][12][13][17][18][19][20] . Much lower energies than in photochemical ET are involved here, questioning the feasibility of actual electron or hole generation (reduction and oxidation) in the nucleobase pairs in the electrochemical potential ranges accessible.…”