Excess electron transfer through one set of DNA duplexes comprising either one or two metal-mediated thymine-Hg -thymine base pairs was studied. Towards this end, the metal-mediated base pair(s) were introduced between an artificial nucleoside bearing a N,N,N',N'-tetramethyl-1,5-diaminonaphthalene derivative (dN, acting as a photoinducible electron donor) and 5-bromo-2'-deoxyuridine (dB, acting as an electron acceptor). Upon one-electron reduction, dB loses a bromide ion. The amount of unreacted dB remaining after irradiation-determined by LC/ICP-MS-was used to evaluate the charge-transfer efficiency across the metal-mediated base pair(s). Reference measurements with canonical adenine:thymine base pairs prove the applicability of this approach for the detection of charge transfer in DNA. The data indicate that, for the set of DNA duplexes under investigation, excess electron transfer across a thymine-Hg -thymine base pair proceeds with low efficiency, comparable to the transfer across a thymine:thymine mispair. Two contiguous thymine-Hg -thymine base pairs effectively shut down excess electron transfer.
SummaryThe imidazole–Ag(I)–imidazole base pair is one of the best-investigated artificial metal-mediated base pairs. We show here that its stability can be further improved by formally replacing the imidazole moiety by a 2-methylimidazole or 4-methylimidazole moiety. A comparison of the thermal stability of several double helices shows that the addition of one equivalent of Ag(I) leads to a 50% larger increase in the melting temperature when a DNA duplex with methylated imidazole nucleosides is applied. This significant effect can likely be attributed to a better steric shielding of the metal ion within the metal-mediated base pair.
Th formation of metal base pairs is a versatile method for the introduction of metal cations into nucleic acids that has been used in numerous applications including the construction of metal nanowires, development of energy, charge-transfer devices and expansion of the genetic alphabet. As an alternative, enzymatic construction of metal base pairs is an alluring strategy that grants access to longer sequences and offers the possibility of using such unnatural base pairs (UBPs) in SELEX experiments for the identification of functional nucleic acids. This method remains rather underexplored, and a better understanding of the key parameters in the design of efficient nucleotides is required. We have investigated the effect of methylation of the imidazole nucleoside (dIm nMe TP) on the efficiency of the enzymatic construction of metal base pairs. The presence of methyl substituents on dImTP facilitates the polymerase-driven formation of dIm 4Me À Ag I À dIm and dIm 2Me TPÀ Cr III À dIm base pairs. Steric factors rather than the basicity of the imidazole nucleobase appear to govern the enzymatic formation of such metal base pairs. We also demonstrate the compatibility of other metal cations rarely considered in the construction of artificial metal bases by enzymatic DNA synthesis under both primer extension reaction and PCR conditions. These findings open up new directions for the design of nucleotide analogues for the development of metal base pairs.
DNA‐mediated charge transfer represents a topical area of research. The influence of the site‐specific introduction of a metal ion into the base pair stack is a matter of current debate. In their communication on page 10244 ff., U. Karst, J. Müller et al. contribute to this debate by reporting an experimental study on excess electron transfer across a metal‐mediated base pair within a DNA double helix. To this end, LC/ICP‐MS was applied for the first time to quantify the electron‐transfer efficiency. The data suggest that a thymine–HgII–thymine base pair influences charge transfer in the same way as a thymine:thymine mispair does.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.