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Duplex DNA monolayers were self-assembled on gold through a disulfide linkage and both B- and M-DNA conformations were studied using X-ray photoelectron spectroscopy (XPS). The film thickness, density, elemental composition and ratios for samples were analyzed and compared. The DNA surface coverage, calculated from both XPS and electrochemical measurements, was approximately 1.2 × 1013 molecules/cm2 for B-DNA. All samples showed distinct peaks for C 1s, O 1s, N 1s, P 2p and S 2p as expected for a thiol-linked DNA. On addition of Zn2+ to form M-DNA the C 1s, P 2p and S 2p showed only small changes while both the N 1s and O 1s spectra changed considerably. This result is consistent with Zn2+ interacting with oxygen on the phosphate backbone as well as replacing the imino protons of thymine (T) and guanine (G) in M-DNA. Analysis of the Zn 2p spectra also demonstrated that the concentration of Zn2+ present under M-DNA conditions is consistent with Zn2+ binding to both the phosphate backbone as well as replacing the imino protons of T or G in each base pair. After the M-DNA monolayer is washed with a buffer containing only Na+ the Zn2+ bound to the phosphate backbone is removed while the Zn2+ bound internally still remains. 相似文献
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Dorthe Lindegaard David O. Wood Jesper Wengel Jeremy S. Lee 《Journal of biological inorganic chemistry》2006,11(1):82-87
M-DNA is a complex formed between duplex DNA and divalent metal ions (Zn2+, Cu2+ or Ni2+) at pHs above 8. Previous results showed that the fluorescence of an electron donor fluorophore was quenched when an acceptor
flourophore was placed in the opposite end of an M-DNA duplex suggesting electron transfer through the duplex and indicating
M-DNA may operate as a better conductor than B-DNA. To further investigate the properties of M-DNA, oligodeoxynucleotides
were prepared with fluorescein (Fl) as an electron donor placed at different positions along the helix. An internal position
of the chromophore was made possible by attaching it to the extra hydroxyl arm in the branched monomer 4′-C-hydroxymethylthymidine. Upon excitation of the donor fluorophore, it was demonstrated that electrons could be injected into
the side of an M-DNA helix thereby extending the range of nanoelectronic structures that can be prepared from DNA.
Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users. 相似文献
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