Beta-II conformation of all-beta proteins can be distinguished from unordered form by circular dichroism

The CD spectrum of certain all-beta globular proteins resembles that of unfolded proteins with a characteristic negative band around 200 nm. The conformation of this class is tentatively termed beta-II, which had two features that were absent for unfolded proteins. First, beta-II proteins usually had CD bands due to aromatic side groups in the near-ultraviolet region. Second, the CD intensities both in the far- and in the near-uv region of these compact and rigid proteins usually showed a sharp transition upon thermal denaturation, whereas those of an unordered form changed linearly with rising temperature.