Understanding protein folding requires the determination
of the configurational space accessible to the protein
at different stages in folding. Here, computer simulation
analysis of small angle neutron scattering results is used
to probe the change in the distribution of configurations
on strong denaturation of a globular protein, phosphoglycerate
kinase, in 4 M guanidine hydrochloride solution. To do
this atomic-detail ensembles of the unfolded protein chain
are modeled and their scattering profiles compared with
the experiment. The local conformational statistics are
found to strongly influence the experimental intensity
at scattering vectors between 0.05 and 0.3 Å−1.
Denaturation leads to a reduction in the protein atom-pair
distance distribution function over the ∼3–15
Å region that is associated with a quantifiable shift
in the backbone torsional angle (φ,ψ) distribution
toward the β region of the Ramachandran plot.