  By performing an analysis in moment space using high statistics DIS world
data, we extract the values of both the QCD parameter
$\Lambda^{(4)}_{\bar{MS}}$ up to NLO and of the power corrections to the proton
structure function, $F_2$. At variance with previous analyses, the use of
moments allows us to extend the kinematical range to larger values of $x$,
where we find that power corrections are quantitatively more important. Our
results are consistent with the $n$ dependence predicted by IR renormalon
calculations. We discuss preliminary results on nuclear targets with the intent
of illustrating a possible strategy to disentangle power corrections ascribed
to IR renormalons from the ones generated dynamically e.g. from rescattering in
the final state. The latter appear to be modified in nuclear targets.
