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Martin Castelnovo

Laboratoire de Physique — Laboratoire Joliot-Curie
Ecole Normale Supérieure de Lyon

It has been shown indirectly with biochemical experiments that electrophoretic mobility of mononucleosomes depends on its positioning along DNA. Now this property is widely used to detect qualitatively nucleosome repositioning due either to thermal fluctuations or to the action of remodeling factors. But taken alone, these kind of experiments do just indicate that a change occured either on the conformation of nucleosome, and/or on its charge distribution, since electrophoresis of colloidal particles is mostly sensitive to these two intrinsic properties. No quantitative conclusions can be reached with respect to the precise position of nucleosome along DNA. Physical modeling of electrophoresis might help extracting this information from the experiments. This is the purpose of the present work, where we discuss an original approach to compute the electrophoretic mobility of rigid nucleo-protein complexes like nucleosomes. The model allows to address theoretically the influence of complex position along DNA, as well as wrapped length of DNA on the electrophoretic mobility of the complex.