Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Production of long monomolecular G4-DNA

The above molecules were used as the starting point for designing new procedures for complexation with metal ions and production of µm-long monomolecular G4-DNA nanowires [1]. Synthesis of the above DNA-derivatives was optimised and complemented by characterization using standard (bio) chemical methods [1], Atomic and Electrostatic Force Microscopy (AFM and EFM) [1,2], Scanning Tunnelling Microscopy (STM) [3,4] and Spectroscopy (STS) [5], electrical transport measurements, and theory [6].

The efficiency of the method for the synthesis of G4-DNA was optimised. G4-DNA was originally synthesized from long polyG-polyC double-stranded DNA that is produced enzymatically with Klenow exonuclease minus DNA polymerase. The strands were separated chromatographically at high pH, and the G4-DNA molecules were formed upon lowering of the pH. It was found that dCTP (cytosine tri-phosphate) can be replaced during the enzymatic synthesis with an oligomer of cytosine (typically 20-mer), to obtain a double helix of polyG with unconnected oligomers of C. This improved dramatically the separation yield of the polyG from the fragmented oligomers of C under basic conditions, and hence enabled us to obtain much higher yields in G4-DNA production, although less size uniformity on the surface is observed [7]

[1] A.B. Kotlyar, N. Borovok, T. Molotsky, H. Cohen, E. Shapir, D. Porath, "Long Monomolecular Guanine-Based Nanowires", Adv. Mater. 17, 1901 (2005) (with journal cover - cover of the year).
[2] Hezy Cohen, Tomer Sapir, Natalia Borovok, Tatiana Molotsky, Rosa Di Felice, Alexander B. Kotlyar and Danny Porath, "Polarizability of G4-DNA Observed by EFM Measurements" - Submitted.
[3] E. Shapir, H. Cohen, N. Borovok, A.B. Kotlyar, D. Porath, High-resolution STM imaging of novel poly(G)-poly(C) DNA molecules , J. Phys. Chem. B 110, 4430-4433 (2006).
[4] E. Shapir, J. Yi, H. Cohen, A. Kotlyar, G. Cuniberti, and D. Porath, "The puzzle of contrast inversion in DNA STM imaging", J. Phys. Chem. B Lett. 109, 14270 (2005).
[5] E. Shapir, A. Calzolari, C. Cavazzoni, D. Ryndyk, G. Cuniberti, R. Di Felice, and D. Porath, "Electronic structure of single DNA molecules resolved by transverse scanning tunneling spectroscopy" - Submitted.
[6] R. Di Felice, A. Calzolari, A. Garbesi, S.S. Alexandre, J.M. Soler, "Strain-dependence of the electronic properties in periodic quadruple helical G4-wires", J Phys. Chem. B 109, 22301 (2005); A. Calzolari, R. Di Felice, E. Molinari, A. Garbesi, J. Phys. Chem. B 108, 2509 (2004); J. Phys. Chem. B 108, 13058 (2004); M. Cavallari, A. Calzolari, A. Garbesi, and R. Di Felice, "Stability and Migration of Metal Ions in G4-wires by Molecular Dynamics Simulations", J. Phys. Chem. B 110, 26637 (2006).
[7] N. Borovok et. al., "Enzymatic Synthesis of long uniform poly(dG) strands and their folding into G4-DNA nanostructures" - Submitted.

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