The rational design of complementary DNA sequences can be used to create nanostructures that self-assemble with nanometer precision. DNA nanostructures have been imaged by atomic force microscopy and electron microscopy. Small-angle X-ray scattering (SAXS) provides complementary structural information on the ensemble-averaged state of DNA nanostructures in solution. Here we demonstrate that SAXS can distinguish between different single-layer DNA origami tiles that look identical when immobilized on a mica surface and imaged with atomic force microscopy. We use SAXS to quantify the magnitude of global twist of DNA origami tiles with different crossover periodicities: these measurements highlight the extreme structural sensitivity of single-layer origami to the location of strand crossovers. We also use SAXS to quantify the distance between pairs of gold nanoparticles tethered to specific locations on a DNA origami tile and use this method to measure the overall dimensions and geometry of the DNA nanostructure in solution. Finally, we use indirect Fourier methods, which have long been used for the interpretation of SAXS data from biomolecules, to measure the distance between DNA helix pairs in a DNA origami nanotube. Together, these results provide important methodological advances in the use of SAXS to analyze DNA nanostructures in solution and insights into the structures of single-layer DNA origami.

Drop-casting [Fe(bpp)2][BF4]2 (bpp = 2,6-di[pyrazol-1-yl]pyridine) onto HOPG affords chain-of-beads nanostructures. SAMs of bpp derivatives with sulfur-containing tethers are also described.

We report the design and assembly of chiral DNA nanotubes with well-defined and addressable inside and outside surfaces. We demonstrate that the outside surface can be functionalised with a chiral arrangement of gold nanoparticles to create a plasmonic device and that the inside surface can be functionalised with a track for a molecular motor allowing transport of a cargo within the central cavity.

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A convenient preparative route to the unsymmetrical bidentate phosphines R2P(CH2),PPh2 (R = M e or Et; n = 3 or 4) is described. This involves the synthesis of unsymmetrical diphosphonium salts, [ R2PhP(CH2),PPh3] Br2, and diphosphine oxides, R2P(0) (CH2),PPh2, as intermediates. The symmetrical ligand Et,P(CH,),PEt, was also prepared by the same route. New co-ordination complexes