title: Measurements of single nucleotide electronic states as nanoelectronic fingerprints for identification of DNA nucleobases, their protonated and unprotonated states, isomers, and tautomers.
abstract: Several nanoelectronic techniques have been explored to distinguish the sequence of nucleic acids in DNA macromolecules. Identification of unique electronic signatures using nanopore conductance, tunneling spectroscopy, or other nanoelectronic techniques depends on electronic states of the DNA nucleotides. While several experimental and computational studies have focused on interaction of nucleobases with different substrates, the effect of nucleic acid biochemistry on its electronic properties has been largely unexplored. Here, we present correlated measurements of frontier molecular orbitals and higher-order electronic states for four DNA nucleobases (adenine, cytosine, thymine, and guanine), and first-principle quantum chemical density functional theoretical (DFT) computations. Using different pH conditions in our experiments, we show that small changes in the biochemical state of these nucleic acids strongly affect the intrinsic electronic structure, measured using scanning tunneling spectroscopy (STS). In our experimental measurements and computations, significant differences were observed between the position of frontier orbitals and higher-energy states between protonated and unprotonated nucleic acids, isomers, and different keto-enol tautomer's formed in these nucleotides, leading to their facile identification. Furthermore, we show unique "electronic fingerprints" for all nucleotides (A, G, T, C) using STS, with most distinct states identified at acidic pH. These results can have important implications for identification of nucleic acid sequences in DNA molecules using a high-throughput nanoelectronic identification technique.
authors: †Department of Chemical and Biological Engineering, ‡Renewable and Sustainable Energy Institute, §BioFrontiers Institute, and ∥Materials Science and Engineering, University of Colorado, Boulder, Colorado, 80309, United States.
authors: Josep Casamada
authors: JC
authors: Ribot
authors: †Department of Chemical and Biological Engineering, ‡Renewable and Sustainable Energy Institute, §BioFrontiers Institute, and ∥Materials Science and Engineering, University of Colorado, Boulder, Colorado, 80309, United States.
authors: Anushree
authors: A
authors: Chatterjee
authors: †Department of Chemical and Biological Engineering, ‡Renewable and Sustainable Energy Institute, §BioFrontiers Institute, and ∥Materials Science and Engineering, University of Colorado, Boulder, Colorado, 80309, United States.
authors: Prashant
authors: P
authors: Nagpal
mesh_terms: D000225:Adenine / Q000737:chemistry*; D003596:Cytosine / Q000737:chemistry*; D055590:Electromagnetic Phenomena; D006147:Guanine / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007536:Isomerism; D008956:Models, Chemical; D008957:Models, Genetic; D015394:Molecular Structure; D009711:Nucleotides / Q000737:chemistry*; D011522:Protons; D011789:Quantum Theory; D013057:Spectrum Analysis; D013941:Thymine / Q000737:chemistry*
chemical_list: D009711:Nucleotides; D011522:Protons; D006147:Guanine; D003596:Cytosine; D000225:Adenine; D013941:Thymine