title: Robust charge transport in DNA double crossover assemblies.
abstract: BACKGROUND
  Multiple-stranded DNA assemblies, encoded by sequence, have been constructed in an effort to self-assemble nanodevices of defined molecular architecture. Double-helical DNA has been probed also as a molecular medium for charge transport. Conductivity studies suggest that DNA displays semiconductor properties, whereas biochemical studies have shown that oxidative damage to B-DNA at the 5'-G of a 5'-GG-3' doublet can occur by charge transport through DNA up to 20 nm from a photo-excited metallointercalator. The possible application of DNA assemblies, in particular double crossover (DX) molecules, in electrical nanodevices prompted the design of a DNA DX assembly with oxidatively sensitive guanine moieties and a tethered rhodium photo-oxidant strategically placed to probe charge transport.
  
  
  RESULTS
  DX assemblies support long-range charge transport selectively down the base stack bearing the intercalated photo-oxidant. Despite tight packing, no electron transfer (ET) crossover to the adjacent base stack is observed. Moreover, the base stack of a DX assembly is well-coupled and less susceptible than duplex DNA to stacking perturbations. Introducing a double mismatch along the path for charge transport entirely disrupts long-range ET in duplex DNA, but only marginally decreases it in the analogous stack within DX molecules.
  
  
  CONCLUSIONS
  The path for charge transport in a DX DNA assembly is determined directly by base stacking. As a result, the two closely packed stacks within this assembly are electronically insulated from one another. Therefore, DX DNA assemblies may serve as robust, insulated conduits for charge transport in nanoscale devices.
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena 91125, USA.
authors.forename: D T
authors.initials: DT
authors.lastname: Odom
authors.forename: E A
authors.initials: EA
authors.lastname: Dill
authors.forename: J K
authors.initials: JK
authors.lastname: Barton
mesh_terms: D020137:Base Pair Mismatch; D001483:Base Sequence; D004247:DNA / Q000737:chemistry* / Q000648:ultrastructure*; D004553:Electric Conductivity; D004563:Electrochemistry; D004591:Electrophoresis, Polyacrylamide Gel; D007364:Intercalating Agents / Q000737:chemistry; D015394:Molecular Structure; D009841:Oligonucleotides / Q000138:chemical synthesis / Q000378:metabolism; D010083:Oxidants, Photochemical; D010782:Photolysis; D012238:Rhodium / Q000737:chemistry; D013329:Structure-Activity Relationship
chemical_list: D007364:Intercalating Agents; D009841:Oligonucleotides; D010083:Oxidants, Photochemical; D004247:DNA; D012238:Rhodium