Advillin folding takes place on a hypersurface of small dimensionality.

All-atom explicit-solvent molecular dynamics simulations have been used to investigate the topological structure of the space explored during folding by the c-terminal fragment of the Advillin headpiece, a 36 amino-acid protein. A fractal dimension analysis shows that the hypersurface explored during the folding process has an approximate dimensionality of only three. It is shown that this low dimensionality persists well above the unfolding temperature and is not present in simple coarse-grained models.