laboratoire de physique statistique
 
 
laboratoire de physique statistique

Publications

Rechercher
2009 


Jean-François ALLEMAND 


4
P U B L I C A T I O N S



 
2009
Measurement of the Torque on a Single Stretched and Twisted DNA Using Magnetic Tweezers - Mosconi, Francesco and Allemand, Jean Francois and Bensimon, David and Croquette, Vincent
PHYSICAL REVIEW LETTERS 102 (2009) 
LPS


Abstract : We deduced the torque applied on a single stretched and twisted DNA by integrating the change in the molecule's extension with respect to force as it is coiled. While consistent with previous direct measurements of the torque at high forces (F > 1 pN), this method, which is simple and does not require a sophisticated setup, allows for lower force estimates. We used this approach to deduce the effective torsional modulus of DNA, which decreases with force, and to estimate the buckling torque of DNA as a function of force in various salt conditions.
Single-molecule Visualization of Binding Modes of Helicase to DNA on PEGylated Surfaces - Yokota, Hiroaki and Han, Yong-Woon and Allemand, Jean-Francois and Xi, Xu Guang and Bensimon, David and Croquette, Vincent and Ito, Yoshihiro and Harada, Yoshie
CHEMISTRY LETTERS 38308-309 (2009) 
LPS


Abstract : Binding modes of helicase to various DNA substrates were visualized by single-molecule fluorescence imaging on silicate coverslips coated with poly(ethylene glycol) (PEG) which minimizes the background noise from nonspecific protein adsorption. The results clearly show that the helicase has higher affinity for double-stranded DNA (dsDNA) with a single-stranded DNA (ssDNA) tail than that without one and that multiple helicases can bind to 4.7-kilonucleotide (knt) ssDNA. The study reported here will enhance the capabilities of single-molecule fluorescence studies on DNA-protein interactions.
Bacterial translocation motors investigated by single molecule techniques - Allemand, Jean-Francois and Maier, Berenike
FEMS MICROBIOLOGY REVIEWS 33593-610 (2009) 
LPS


Abstract : Translocation of DNA and protein fibers through narrow constrictions is a ubiquitous and crucial activity of bacterial cells. Bacteria use specialized machines to support macromolecular movement. A very important step toward a mechanistic understanding of these translocation machines is the characterization of their physical properties at the single molecule level. Recently, four bacterial transport processes have been characterized by nanomanipulation at the single molecule level, DNA translocation by FtsK and SpoIIIE, DNA import during transformation, and the related process of a type IV pilus retraction. With all four processes, the translocation rates, processivity, and stalling forces were remarkably high as compared with single molecule experiments with other molecular motors. Although substrates of all four processes proceed along a preferential direction of translocation, directionality has been shown to be controlled by distinct mechanisms.
Single DNA/protein studies with magnetic traps - Meglio, Adrien and Praly, Elise and Ding, Fangyuan and Allemand, Jean-Francois and Bensimon, David and Croquette, Vincent
CURRENT OPINION IN STRUCTURAL BIOLOGY 19615-622 (2009) 
LPS


Abstract : Magnetic traps provide a simple technique to pull and twist a variety of biomolecules and monitor the resulting change in extension. They have been used with great success to investigate the interaction of stretched and supercoiled DNA and DNA fibers (e.g. chromatin) with a great variety of enzymes. In this small review we will address their recent use in the study of topoisomerases, gyrase, DNA translocases and various structural proteins.