Using molecular dynamics simulations, we explore the mechanism that may underlie the type of folding transitions observed experimentally in anhydrous proteins. Recent relaxation studies of a partly unfolded alpha-helical bundle suggest an approach to simulating cycles of folding/re-unfolding transitions. Here, we provide evidence that such processes may be general, by uncovering a similar relaxation pattern in lysozyme, a more flexible alpha/beta protein. We find that, while refolding is initiated by partial polymer collapse, the reversible re-unfolding of compact normative structures proceeds as a correlated transition not unlike the direct unfolding of lysozyme from its native state. (C) 2003 Elsevier Science B.V. All rights reserved.