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Determination of the DNA conformation in highly dehydrated environments by means of Frequency Modulation AFM

Mercredi 11 décembre 2013 10:30 - Duree : 1 heure
Lieu : Room 018, Central Building, ESRF - 6 Rue Jules Horowitz - Grenoble

Orateur : Andrea CERRETA (University of Fribourg - Switzerland)

In recent years DNA is creating an increasing interest for applications in fields of research not necessarily connected to biology. Part of this interest is due to its self-assembling properties and to the possibility of forming a wide variety of both 2D and 3D nanostructures [1, 2]. Moreover, a considerable amount of literature has been published concerning the DNA conduction properties. It is supposed that a charge can move along DNA through a hopping mechanism between G sites and consequently the distance between them, and in general the DNA sequence, influence the charge transfer rate [3]. The importance not only of the base content, but also of the DNA structure has been pointed out in [4]. DNA can be used as a versatile building block for applications in various fields of nanotechnology. Some of its possible uses will most likely be implemented in non-physiological conditions. Therefore the DNA structure has to be somehow assessed in environments such as air or UHV at nanometer and sub-nanometer scale. The measurements presented in this seminar are meant to be a characterization of the DNA structure once it is firmly attached to a substrate and put in a highly dehydrated environment.

I will discuss different Frequency Modulation (FM) AFM based approaches, which allowed revealing the DNA structure at high resolution. One consisted of performing a series of spectroscopy curves along the molecular axis. Applying this method, it was possible to correlate the variation of AFM tip-DNA forces with the major/minor groove structure. The second was based on constant height scanning of DNA molecules at close separation. This method allowed obtaining frequency shift maps of the DNA molecules that showed a better level of lateral resolution than the classical FM AFM scanning. I will also discuss van der Waals based models of the AFM tip-molecule interaction, which quantitatively explain the dependence of the measured DNA height on the tip properties (material, apex radius). [1] F. A. Aldaye, A. L. Palmer, H. F. Sleiman, Science 321 (2008), 1795-1799. [2] A. V. Pinheiro, D. Han,W.M. Shih, and H. Yan, Nature Nanotechnology 6 (2011), 763-772. [3] B. Giese, Accounts of Chemical Research 33, 9 (2000), 631-636. [4] G. B. Schuster, Accounts of Chemical Research 33, 4 (2000), 253-260.

Contact : claudine.romero@esrf.fr

Discipline évènement : (Physique)
Entité organisatrice : (ESRF)
Nature évènement : (Séminaire)
Evènement répétitif : (Séminaire ESRF)
Site de l'évènement : Polygone scientifique

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