Circular dichroic study of conformational changes in ovalbumin

By simulation of the circular dichroic spectra (Greenfield and Fasman (1969)) and using reference spectra of Chen et al. (1974), native ovalbumin was estimated to contain 33% -helix, 5% -structure, and 62% random coil. Ovalbumin resisted conformational changes in solutions of urea and of SDS. However, guanidine induced transition, starting at about 2 M and completing at about 4.5 M. At concentrations exceeding 4.5 M guanidine, ovalbumin existed as 6–7% -helical, 12–13% -structure, and 80–81% random coil. Ovalbumin after denaturation in 6 M guanidine or in 8 M urea (incubated at 4°C for 24 hr) did not recover the native conformation but acquired a new conformation in each case, with a somewhat destabilized helical structure.Abbreviation used CD circular dichroism - SDS sodium dodecyl sulfate