Tunneling or Hopping? A Direct Electrochemical Observation of Electron Transfer in DNA

Abstract

We developed an axis-mode donor-DNA-acceptor electrochemical system to distinguish whether electron transfer in DNA occurs by tunneling or hopping. In the axismode, rigid stem-loop DNA was designed with the redox probe Ag + embedded at the axis of the strand through a C−Ag + −C mismatch, which was immobilized onto the electrode surface in a saturated manner. Thus, the rotation, swing, and bending of the DNA strand were restricted and then the number of Ag + , the distance L between Ag + and the electrode, and the chemical environment could be precisely controlled. In addition, fast scan cyclic voltammetry was applied to realize the in situ redox reaction of Ag + , without diffusion away from the electrode and the ensuing deconstruction of the stem-loop DNA. In this case, as a direct indicator of rate, the peak Faradaic current i p was extracted and used to fit the tunneling mechanism i ∝ exp (−βL) and the hopping mechanism i ∝ L −η . The value of β was determined to be 0.100 Å −1 , which is consistent with the range of 0.1∼1.5 Å −1 reported previously, while η was determined to be 0.677, which is completely beyond the correct range of 1 ≤ η ≤ 2, demonstrating that electron transfer in DNA occurs by tunneling instead of hopping or that tunneling dominates. Additionally, current additivity and the irrelevance of the base sequence illustrate this point again. Thus, the possibility of independent parallel tunneling currents in DNA strands is revealed, which is helpful for recognizing the feasibility of DNA-based wires and devices.

Heterobimetallic Base Pair Programming in Designer 3D DNA Crystals

“…We believe that an enhanced understanding of mmDNA base pairing will contribute to the design and self-assembly of DNA architectures based on the unique electronic properties and reactivity of these base pairs, as well as introduce new methods for a more complete analysis of different modes of DNA base pairing. The existence of heterobimetallic base pairs in each tested homopyrimidine base pair and their highly-specific environmental requirements provide an exciting foothold for tunable topological nanowires. , Previous studies have shown homobimetallic binding modes with silver­(I), as well as heterometal/counterion complexes with potassium­(I), strontium­(II), or barium­(II), but the presence of two different transition metals in a single DNA base pair has not, to our knowledge, been demonstrated previously. As such, future physical studies of mmDNA should include heterobimetal base pairs, which greatly diversify the DNA chemical design language.…”

“…The existence of heterobimetallic base pairs in each tested homopyrimidine base pair and their highly-specific environmental requirements provide an exciting foothold for tunable topological nanowires. 12,51 Previous studies have shown homobimetallic binding modes with silver(I), 16 as well as heterometal/counterion complexes with potassium(I), strontium(II), or barium(II), 52 but the presence of two different transition metals in a single DNA base pair has not, to our knowledge, been demonstrated previously. As such, future physical studies of mmDNA should include heterobimetal base pairs, which greatly diversify the DNA chemical design language.…”

Integrated Plastic Microfluidic Device for Heavy Metal Ion Detection

“…The sensors’ principle of operation relies on the differences in charge transport observed across single- and double-stranded DNA and the coverage of the surfaces with nanoparticles. By tuning the deposited nanoparticles’ size and inter-particle distance, an intermediate conductivity state can be attained, whereby electron hopping in between adjacent nanoparticles occurs and is further enhanced through the bridging effect of linkers, including that of organic molecules [ 36 ]. When the coverage of the sensor surfaces with nanoparticles exceeds this percolation threshold, electrical conductivity jumps up several orders of magnitude due to the formation of continuous electron paths or conducting networks that are insensitive to the presence of linkers.…”

Portable Detection of Lysine Acetyltransferase Activity in Lung Cancer Cells Based on a Miniature Electrochemical Sensor

“…This efficiency is due to the rapid conversion from Cu(II) to Cu(0) and back to Cu(II) before it can escape from the electrode surface. Conversely, a noticeable decrease in the current intensity is observed in standard CV tests at a scan rate of 0.1 V/s (Figure 1E), illustrating a slower transition of Cu, unable to remain stably on the electrode surface, 31 a challenge in electrochemistry that our work addresses. Furthermore, we explored the effect of electrode cleaning on the signal output.…”