Biology · Protein Structure and Biophysical Techniques

A circular dichroism (CD) spectrum in the far-UV region informs on the kind and content of secondary structures in a protein. Near-UV CD and tryptophan emission spectra inform on the tertiary structure. Analysis of a protein 'X' shows: at pH 7.0, it exhibits a characteristic native folded spectra for both secondary and tertiary features; at pH 3.0, it retains its far-UV CD secondary structure profile but loses its near-UV CD and intrinsic fluorescence tertiary constraints; in the presence of 6.0 M guanidine hydrochloride, all structural features are lost. What structural state does the experiment report for protein 'X' at pH 3.0?