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Photosynthetic pigments from etiolated cucumber (Cucumis sativus var. Beit Alpha improved, Hazera Co., Gedera) cotyledons were extracted by direct immersion of the intact cotyledons into the solvent N,N-dimethylformamide (DMF). The solvent is especially efficient when pigment concentration is low; time and tools are saved and the loss of pigment that(More)
Seemingly contradicting results raised a debate over the ability of DNA to transport charge and the nature of the conduction mechanisms through it. We developed an experimental approach for measuring current through DNA molecules, chemically connected on both ends to a metal substrate and to a gold nanoparticle, by using a conductive atomic force(More)
Controlled formation of complex nanostructures is one of the main goals of nanoscience and nanotechnology. Stable Protein 1 (SP1) is a boiling-stable ring protein complex, 11 nm in diameter, which self-assembles from 12 identical monomers. SP1 can be utilized to form large ordered arrays; it can be easily modified by genetic engineering to produce various(More)
Three types of DNA: approximately 2700 bp polydeoxyguanylic olydeoxycytidylic acid [poly(dG)-poly(dC)], approximately 2700 bp polydeoxyadenylic polydeoxythymidylic acid [poly(dA)-poly(dT)] and 2686 bp linear plasmid pUC19 were deposited on a mica surface and imaged by atomic force microscopy. Contour length measurements show that the average length of(More)
DNA and DNA-based polymers are of interest in molecular electronics because of their versatile and programmable structures. However, transport measurements have produced a range of seemingly contradictory results due to differences in the measured molecules and experimental set-ups, and transporting significant current through individual DNA-based molecules(More)
We propose a model hamiltonian for describing charge transport through short homogeneous double stranded DNA molecules. We show that the hybridization of the overlapping π orbitals in the base-pair stack coupled to the backbone is sufficient to predict the existence of a gap in the nonequilibrium current-voltage characteristics with a minimal number of(More)
Attempts to resolve the energy-level structure of single DNA molecules by scanning tunnelling spectroscopy span over the past two decades, owing to the unique ability of this technique to probe the local density of states of objects deposited on a surface. Nevertheless, success was hindered by extreme technical difficulties in stable deposition and(More)
G4-DNA, a quadruple helical motif of stacked guanine tetrads, is stiffer and more resistant to surface forces than double-stranded DNA (dsDNA), yet it enables self-assembly. Therefore, it is more likely to enable charge transport upon deposition on hard supports. We report clear evidence of polarizability of long G4-DNA molecules measured by electrostatic(More)
We describe a method for the preparation of novel long (hundreds of nanometers), uniform, inter-molecular G4-DNA molecules composed of four parallel G-strands. The only long continuous G4-DNA reported so far are intra-molecular structures made of a single G-strand. To enable a tetra-molecular assembly of the G-strands we developed a novel approach based on(More)