A mechanistic study of electron transfer from the distal termini of electrode-bound, single-stranded DNAs

Takanori Uzawa, Ryan R. Cheng, Ryan J. White, Dmitrii E. Makarov, Kevin W. Plaxco

Research output: Contribution to journalArticlepeer-review

52 Scopus citations

Abstract

Electrode-bound, redox-reporter-modified oligonucleotides play roles in the functioning of a number of electrochemical biosensors, and thus the question of electron transfer through or from such molecules has proven of significant interest. In response, we have experimentally characterized the rate with which electrons are transferred between a methylene blue moiety on the distal end of a short, single-stranded polythymine DNA to a monolayer-coated gold electrode to which the other end of the DNA is site-specifically attached. We find that this rate scales with oligonucleotide length to the -1.16 ± 0.09 power. This weak, approximately inverse length dependence differs dramatically from the much stronger dependencies observed for the rates of end-to-end collisions in single-stranded DNA and through-oligonucleotide electron hopping. It instead coincides with the expected length dependence of a reaction-limited process in which the overall rate is proportional to the equilibrium probability that the end of the oligonucleotide chain approaches the surface. Studies of the ionic strength and viscosity dependencies of electron transfer further support this "chain-flexibility" mechanism, and studies of the electron transfer rate of methylene blue attached to the hexanethiol monolayer suggest that heterogeneous electron transfer through the monolayer is rate limiting. Thus, under the circumstances we have employed, the flexibility (i.e., the equilibrium statistical properties) of the oligonucleotide chain defines the rate with which an attached redox reporter transfers electrons to an underlying electrode, an observation that may be of utility in the design of new biosensor architectures.

Original languageEnglish
Pages (from-to)16120-16126
Number of pages7
JournalJournal of the American Chemical Society
Volume132
Issue number45
DOIs
StatePublished - Nov 17 2010

Funding

FundersFunder number
National Institute of Biomedical Imaging and BioengineeringR01EB002046

    ASJC Scopus subject areas

    • Catalysis
    • General Chemistry
    • Biochemistry
    • Colloid and Surface Chemistry

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