Fully Reduced Ribonuclease A Does not Expand at High Denaturant Concentration or Temperature

The dimensions of a denatured protein, fully reduced ribonuclease A (r-RNase A), have been measured using synchrotron-based small angle X-ray scattering. The radius of gyration, 34–35 Å, is unchanged from 0–6 M guanidinium chloride and from 20–90 °C at pH 2.5, and agrees with the known scaling behavior for a multitude of chemically denatured states. The polypeptide is behaving as a statistical coil in the non-interacting, high-temperature limit.