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Laboratoire Pierre Aigrain

Accueil du site > La recherche au L.P.A. > Physique du vivant > Groupe de Biophysique > Publications

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Publications du groupe Physique du vivant

La plupart des articles sont disponibles en texte intégral. Liste maintenue à jour par HAL.

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Unzipping DNA with Optical Tweezers : High Sequence Sensitivity and Force Flips

Biophys. J. 82, 1537 (2002)

U. Bockelmann, Ph. Thomen, B. Essevaz-Roulet, V. Viasnoff and F. Heslot,
Force measurements are performed on single DNA molecules with an optical trapping interferometer that combines subpiconewton force resolution and millisecond time resolution. A molecular construction is prepared for mechanically unzipping several thousand-basepair DNA sequences in an in vitro configuration. The force signals corresponding to opening and closing the double helix at low velocity are studied (...)

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Mechanical opening of DNA by micromanipulation and force measurement

C. R. Physique 3, 585 (2002)

U. Bockelmann, B. Essevaz-Roulet, Ph. Thomen and F. Heslot,
In this paper we summarize part of our work on the mechanical unzipping of DNA. We have prepared molecular constructions which allow us to attach the two complementary strands of one end of a single DNA molecule of the bacteriophage l separately to a glass microscope slide and a microscopic bead. In a first series of experiments, a soft microneedle acting as a force sensor is attached to the bead and its deflection is measured with (...)

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Rotational Drag on DNA : A Single Molecule Experiment

Phys. Rev. Lett. 88, 248102 (2002)

Ph. Thomen, U. Bockelmann and F. Heslot
Within a single-molecule configuration, we have studied rotational drag on double stranded linear DNA by measuring the force during mechanical opening and closing of the double helix at different rates. The molecule is cranked at one end by the effect of unzipping and is free to rotate at the other end. In this configuration the rotational friction torque t on double stranded DNA leads to an additional contribution to the opening force. It is shown (...)

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Dynamics of the DNA duplex formation studied by single molecule force measurements

[Biophys. J 87:3388-3396 (2004)]

U. Bockelmann, P. Thomen and F. Heslot,
Within a single-molecule configuration, we have studied rotational drag on double stranded linear DNA by measuring the force during mechanical opening and closing of the double helix at different rates. The molecule is cranked at one end by the effect of unzipping and is free to rotate at the other end. In this configuration the rotational friction torque t on double stranded DNA leads to an additional contribution to the opening force. It is shown (...)

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Single-molecule study of RuvAB-mediated Holliday-junction migration

PNAS 2004 Vol 101 no. 32 | 11611-11616 (2004)

A. Dawid, V. Croquette, M. Grigoriev and F. Heslot,
Branch migration of Holliday junctions is an important step of genetic recombination and DNA repair. In Escherichia coli, this process is driven by the RuvAB complex acting as a molecular motor. Using magnetic tweezers, we studied the RuvAB-directed migration of individual Holliday junctions formed between two 6-kb DNA molecules of identical sequence, and we measured the migration rate at 37°C and 1 mM ATP. We directly demonstrate that (...)

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Unravelling the Mechanism of RNA-Polymerase Forward Motion by Using Mechanical Force.

[Phys. Rev. Lett. 94, 128102 (2005)]

Philippe Thomen, Pascal J. Lopez, and François Heslot
Polymerases form a class of enzymes that act as molecular motors as they move along their nucleic acid substrate during catalysis, incorporating nucleotide triphosphates at the end of the growing chain and consuming chemical energy. A debated issue is how the enzyme converts chemical energy into motion [J. Gelles and R. Landick, Cell 93, 13 (1998)]. In a single molecule assay, we studied how an opposing mechanical force affects the (...)

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Single molecule study of DNA conductivity in aqueous environment

[Phys. Rev. E 73, 031925 (2006)]

O. Legrand, D. Côte, and U. Bockelmann
The dc electrical conductivity of double stranded DNA is investigated experimentally. Single DNA molecules are manipulated with subpiconewton force and deposited on gold nanoelectrodes by optical traps. The DNA is modified at its ends for specific bead attachments and along the chain to favor charge transfer between the DNA base pair stack and the electrodes. For an electrode separation of 70 nm we find, in aqueous environment, electrical resistances (...)

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DNA mechanics as a tool to probe helicase and translocase activity.

[Nucleic Acids Res. 34(15):4232-44 (2006)]

Lionnet T, Dawid A, Bigot S, Barre FX, Saleh OA, Heslot F, Allemand JF, Bensimon D, Croquette V.
Helicases and translocases are proteins that use the energy derived from ATP hydrolysis to move along or pump nucleic acid substrates. Single molecule manipulation has proved to be a powerful tool to investigate the mechanochemistry of these motors. Here we first describe the basic mechanical properties of DNA unraveled by single molecule manipulation techniques. Then we demonstrate how the (...)

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Mechanically controlled DNA extrusion from a palindromic sequence by single molecule micromanipulation.

[Phys. Rev. Lett. 96 (18):188102 (2006)]

Alexandre Dawid, Fabien Guillemot, Camille Breme, Vincent Croquette, François Heslot
A magnetic tweezers setup is used to control both the stretching force and the relative linking number DeltaLk of a palindromic DNA molecule. We show here, in absence of divalent ions, that twisting negatively the molecule while stretching it at approximately 1 pN induces the formation of a cruciform DNA structure. Furthermore, once the cruciform DNA structure is formed, the extrusion of several kilo-base (...)

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