Evidence for the validity of three-component fitting of protein circular dichroism spectra.

The validity of three-component fitting of protein circular dichroism (CD) spectra in the peptide absorption region with basis spectra for helical, /?-sheet and unordered structure is examined by matrix rank analysis of protein CD spectra. It is shown that a three-component basis can be justified for several proteins within the limits of experimental error of the spectra. It is suggested that the fitting of protein CD spectra with basis spectra derived from reference proteins should be preceded by matrix rank analysis to show that the CD spectra of the reference and unknown proteins have the same basis.