Role of nucleobase energetics and nucleobase interactions in single-stranded peptide nucleic acid charge transfer.


Journal Article

Self-assembled monolayers of single-stranded (ss) peptide nucleic acids (PNAs) containing seven nucleotides (TTTXTTT), a C-terminus cysteine, and an N-terminus ferrocene redox group were formed on gold electrodes. The PNA monomer group (X) was selected to be either cytosine (C), thymine (T), adenine (A), guanine (G), or a methyl group (Bk). The charge transfer rate through the oligonucleotides was found to correlate with the oxidation potential of X. Kinetic measurements and computational studies of the ss-PNA fragments show that a nucleobase mediated charge transport mechanism in the deep tunneling superexchange regime can explain the observed dependence of the kinetics of charge transfer on the PNA sequence. Theoretical analysis suggests that the charge transport is dominantly hole-mediated and takes place through the filled bridge orbitals. The strongest contribution to conductance comes from the highest filled orbitals (HOMO, HOMO-1, and HOMO-2) of individual bases, with a rapid drop off in contributions from lower lying filled orbitals. Our studies further suggest that the linear correlation observed between the experimental charge transfer rates and the oxidation potential of base X arises from weak average interbase couplings and similar stacking geometries for the four TTTXTTT systems.

Full Text

Duke Authors

Cited Authors

  • Paul, A; Bezer, S; Venkatramani, R; Kocsis, L; Wierzbinski, E; Balaeff, A; Keinan, S; Beratan, DN; Achim, C; Waldeck, DH

Published Date

  • May 2009

Published In

Volume / Issue

  • 131 / 18

Start / End Page

  • 6498 - 6507

PubMed ID

  • 19382798

Pubmed Central ID

  • 19382798

Electronic International Standard Serial Number (EISSN)

  • 1520-5126

International Standard Serial Number (ISSN)

  • 0002-7863

Digital Object Identifier (DOI)

  • 10.1021/ja9000163


  • eng