Denaturant-induced conformations of globulins

The effects of denaturation of amaranth globulins (A-G) by urea, guanidine hydrochloride (GuHCl), and sodium dodecyl sulfate (SDS) were studied. Progressive unfolding of globulins was measured as a function of fluorescent light intensity, peak response, and shift in the maximum emission wavelength. Decreases in fluorescence intensity and shift in maximum-emission wavelength (from 341.5 to 355.0 nm) were shown using the fluorescence of tryptophan at 295 nm. Kinetic measurements showed that the decrease of fluorescence intensity was faster with SDS than with GuHCl and exhibited a double exponential decay pattern. Differences in secondary and tertiary structures during denaturation were observed, and changes in alpha-helical content and position of aromatic groups were calculated. The A-G were compared with quinoa globulins (Q-G). Comparison of relative structural stability of native globulins by intrinsic fluorescence and circular dichroism measurements showed that A-G are relatively stable in comparison with Q-G and bovine gamma-globulins.