A new approach to the calculation of secondary structures of globular proteins by optical rotatory dispersion and circular dichroism

Abstract

Summary The rotatory contributions can be written as X = ΣfiXi, where the subscripts i = H, β and R represent the fractions of the helix, β-form and unordered form. X can be the bo of the Moffitt equation, [m]233, [θ]222 or other parameters at any chosen wavelength. With fi's from the X-ray diffraction studies, the reference values, X′s, are solved by a least-square method. The helical content of a protein can be determined by: (1) bo = −580fH, (2) [m]233 = −12700fH −2520, and (3) [θ]222 = −30300fH − 2340. The estimation of the β-form is still uncertain.