On the analysis of circular dichroic spectra of proteins

A new method is presented for analyzing circular dichroism spectra. The method employs integrals over the data and calculates the alpha-helical, beta-sheet, and random coil content of the proteins from such integrals. It is shown that the analyzed alpha-helical content is usually reliable to within 5%, beta-sheet values are somewhat less reliable, and random coil values are least reliable. Curve fitting techniques are shown to be misleading. The method has a number of advantages over existing procedures.