Browsing by Author "Peyrard, M"

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    Melting of highly oriented fiber DNA subjected to osmotic pressure
    (ACS Publications, 2015-03-15) Wildes, AR; Khadeeva, LZ; Trewby, W; Valle-Orero, J; Studer, AJ; Garden, JL; Peyrard, M
    A pilot study of the possibility to investigate temperature-dependent neutron scattering from fiber-DNA in solution is presented. The study aims to establish the feasibility of experiments to probe the influence of spatial confinement on the structural correlation and the formation of denatured bubbles in DNA during the melting transition. Calorimetry and neutron scattering experiments on fiber samples immersed in solutions of poly(ethylene glycol) (PEG) prove that the melting transition occurs in these samples, that the transition is reversible to some degree, and that the transition is broader in temperature than for humidified fiber samples. The PEG solutions apply an osmotic pressure that maintains the fiber orientation, establishing the feasibility of future scattering experiments to study the melting transition in these samples. © 2015 American Chemical Society
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    Small-angle scattering as a tool to study the thermal denaturation of DNA
    (IOP Science, 2014-10-02) Wood, K; Knott, RB; Tonchev, O; Angelov, D; Theodorakopoulos, N; Peyrard, M
    DNA thermal denaturation is the breaking of the base pairs, leading to a splitting of the two strands of the double helix. While it is easy to measure the fraction of open base pairs $(f)$ vs. temperature, determining the fraction $(p)$ of fully open molecules is much harder. Previously, the simultaneous recording of f and p could only be achieved for special sequences. We show that small-angle scattering of X-rays or neutrons allows the measurement of p for any sequence. We illustrate the method with a SAXS investigation of two sequences designed to exhibit different melting profiles and compare the SAXS data with nano-calorimetric measurements of the melting curve. © 2014, EPLA.
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    Thermal denaturation of A-DNA
    (IOP Science, 2014-11-07) Valle-Orero, J; Wildes, AR; Theodorakopoulos, N; Cuesta-López, S; Garden, JL; Danilkin, SA; Peyrard, M
    The DNA molecule can take various conformational forms. Investigations focus mainly on the so-called 'B-form', schematically drawn in the famous paper by Watson and Crick [1]. This is the usual form of DNA in a biological environment and is the only form that is stable in an aqueous environment. Other forms, however, can teach us much about DNA. They have the same nucleotide base pairs for 'building blocks' as B-DNA, but with different relative positions, and studying these forms gives insight into the interactions between elements under conditions far from equilibrium in the B-form. Studying the thermal denaturation is particularly interesting because it provides a direct probe of those interactions which control the growth of the fluctuations when the 'melting' temperature is approached. Here we report such a study on the 'A-form' using calorimetry and neutron scattering. We show that it can be carried further than a similar study on B-DNA, requiring the improvement of thermodynamic models for DNA.© 2014 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.