  It is shown that a small subset of modes which are likely to be involved in
protein functional motions of large amplitude can be determined by retaining
the most robust normal modes obtained using different protein models. This
result should prove helpful in the context of several applications proposed
recently, like for solving difficult molecular replacement problems or for
fitting atomic structures into low-resolution electron density maps. Moreover,
it may also pave the way for the development of methods allowing to predict
such motions accurately.
