Denaturation of the high molecular weight protein fraction of mustard (Brassica juncea) and rapeseed (Brassica campestris) by urea or guanidinium hydrochloride.

Urea and guanidinium hydrochloride dissociate the 12S protein of mustard and rapeseed to 1.8 S protein and the extent of dissociation depends on the concentration of the denaturant. Mustard (Brassica juncea) protein is more readily dissociated than the rapeseed (Brassica campestris) protein. The reagents denature the protein as evidenced by increase in viscosity, appearance of difference spectra and quenching of fluorescence. Rapeseed protein is denatured more readily than the mustard protein. Analysis of visctosity, spectral and fluoresence data suggests that the first event in the denaturation reaction is the perturbation of the aromatic amino acid residues followed by their exposure to the solvent medium and unfolding of the protein molecule.