The ability of the DNA double helix to transport electrons underlies many life‐centered biological processes and bio‐electronic applications. However, there is little consensus on how efficiently the base pair π‐stacks of DNA mediate electron transport. This minireview scrutinizes the current state‐of‐the‐art knowledge on electron transfer (ET) properties of DNA and its long‐range ability to transfer (mediate) electrical signals at electrified interfaces, without being oxidized or reduced. Complex changes an electric field induces in the DNA structure and its electronic properties govern the efficiency of DNA‐mediated ET at electrodes and allow addressing the existing phenomenological riddles, while recently discovered rectifying properties of DNA contribute both to our understanding of DNA′s ET in living systems and to advances in molecular bioelectronics. 相似文献
Whether the DNA base pair stack might serve as a medium for efficient, long-range charge transfer has been debated almost since the first proposal of the double-helical structure of DNA. The consequences of long-range radical migration through DNA are important with respect to understanding carcinogenesis and mutagenesis. Double-helical DNA has in its core a stacked array of aromatic heterocyclic base pairs, and this molecular π stack represents a unique system in which to explore the chemistry of electron transfer. We designed a family of metal complexes which bind to DNA by intercalative stacking within the helix; these metallointercalators may be usefully applied in probing DNA-mediated electron transfer. Here we describe a range of electron transfer reactions we carried out which are mediated by the DNA base paired stack. In some cases, DNA serves as a bridge, and spectroscopic analyses permit us to probe how the π stack couples DNA-bound donors and acceptors. These studies point to the sensitivity of coupling to DNA intercalation. However, if the DNA π stack effectively bridges donors and acceptors, the base-pair stack itself might serve not only as a conduit for electron transfer in DNA, but also in reactions initiated from a remote position. We carried out a series of reactions involving oxidative damage to DNA arising from the remotely positioned oxidant on the helix. The implications of long-range charge migration through DNA to effect damage are substantial. As in other DNA-mediated charge transfers, these reactions are highly dependent on DNA intercalation and the integrity of the intervening base-pair stack, but not on molecular distance. Furthermore, a physiologically important DNA lesion, the thymine dimers, can be reversed in a reaction initiated by electron transfer. This repair reaction can also be promoted from a distance as a result of long-range charge migration through the DNA base pair stack. 相似文献
We report a simple solution based method for the gold (Au) metallization of DNA resulting in a Au nanowire network. Advantage
of solution based approach is that it allows the removal of excess gold (Au+3) ions by extraction with tetraoctylammonium bromide (TOAB) in order to avoid non specific metallization. Further it has been
shown that Au metallized DNA obtained in aqueous phase can be transferred to organic phase using hexadecyl aniline (HDA).
Au metallized DNA has potential application in nanoscale devices. 相似文献
Regardless of its position within the DNA film , cross-linked daunomycin (DM) is efficiently reduced electrochemically, indicating that the electron transfer exhibits a shallow distance dependence. Upon the introduction of an intervening cytosine–adenine (CA) mismatch, the electrochemical response is dramatically attenuated (shown schematically). Therefore, the DNA double helix can facilitate long-range electron transfer, but only in the presence of a well-stacked pathway. 相似文献
Hopping between bases of similar redox potentials is the mechanism by which charge transport occurs through DNA. This was shown by rate measurements performed with double strands 1 – 3 . This mechanism explains why hole transfer displays a strong sequence dependence, and postulates that electron transfer in unperturbed DNA should not be dependent on the sequence. 相似文献
No benefit from base stacking is observed for rates of electron transfer in DNA. This conclusion was drawn from experiments with a new DNA assay in which a radical cationic site, generated by strand cleavage, can be reduced by the guanine bases in the same DNA (the electron transfer is indicated by arrows in the diagram). The distance dependence of this electron transfer step is determined by the chemical yield of the reduction product. 相似文献
Zip it up : Attachment of porphyrins onto complementary DNA strands leads to zipper‐porphyrin arrays and, in the presence of eleven modifications, an increase in the melting temperature of the duplex. Mixed zinc and free‐base porphyrin arrays undergo energy transfer from the zinc porphyrin to the free‐base porphyrin in the annealed duplex but not in the denatured form (see scheme), giving access to reversible formation of potential photonic wires.
The directionality of the hole-transfer processes between DNA backbone and base was investigated by using phosphorodithioate [P(S−)=S] components. ESR spectroscopy in homogeneous frozen aqueous solutions and pulse radiolysis in aqueous solution at ambient temperature confirmed initial formation of G.+-P(S−)=S. The ionization potential of G-P(S−)=S was calculated to be slightly lower than that of guanine in 5′-dGMP. Subsequent thermally activated hole transfer from G.+ to P(S−)=S led to dithiyl radical (P-2S.) formation on the μs timescale. In parallel, ESR spectroscopy, pulse radiolysis, and density functional theory (DFT) calculations confirmed P-2S. formation in an abasic phosphorodithioate model compound. ESR investigations at low temperatures and higher G-P(S−)=S concentrations showed a bimolecular conversion of P-2S. to the σ2-σ*1-bonded dimer anion radical [-P-2S 2S-P-]− [ΔG (150 K, DFT)=−7.2 kcal mol−1]. However, [-P-2S 2S-P-]− formation was not observed by pulse radiolysis [ΔG° (298 K, DFT)=−1.4 kcal mol−1]. Neither P-2S. nor [-P-2S 2S-P-]− oxidized guanine base; only base-to-backbone hole transfer occurs in phosphorodithioate. 相似文献
Benzophenone (BP) and drugs containing the BP chromophore, such as the non-steroidal anti-inflammatory drug ketoprofen, have been widely reported as DNA photosensitizers through triplet–triplet energy transfer (TTET). In the present work, a direct spectroscopic fingerprint for the formation of the thymine triplet (3Thy*) by through-bond (TB) TTET from 3BP* has been uncovered. This has been achieved in two new systems that have been designed and synthesized with one BP and one thymine (Thy) covalently linked to the two ends of the rigid skeleton of the natural bile acids cholic and lithocholic acid. The results shown here prove that it is possible to achieve triplet energy transfer to a Thy unit even when the photosensitizer is at a long (nonbonding) distance. 相似文献