  The measurement of the proton structure function at HERA is often seen as a
hint for the observation of saturation in high-energy QCD e.g. through the
observation of geometric scaling. Accordingly, the dipole picture provides a
powerful framework in which the QCD-based saturation models can be confronted
to the data. In this paper, we give a parametrisation of proton structure
function which is directly constrained by the dynamics of QCD in its
high-energy limit and fully includes the heavy quark effects. We obtain a good
agreement with the available data. Furthermore, to the contrary of various
models in the literature, we do not observe a significant decrease of the
saturation momentum due to the heavy quark inclusion.
