  We present in this paper an original approach to compute the electrophoretic
mobility of rigid nucleo-protein complexes like nucleosomes. This 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. The
predictions of the model are in qualitative agreement with experimental results
on mononucleosomes assembled on short DNA fragments (<400bp). Influence of
additional experimental parameters like gel concentration, ionic strength,
effective charges is also discussed in the framework of the model, and is found
to be qualitatively consistent with experiments when available. Based on the
present model, we propose a simple semi-empirical formula describing
positioning of nucleosomes as seen through electrophoresis.
