Effect of sodium dodecyl sulphate on the 12S fraction of mustard proteins (B. juncea).

The effect of SDS* on the 12S protein fraction ofmustard seed (B. juncea) has
been followed by the techniques of ultracentrifugation, gel filtration, gel
electrophoresis, viscosity, ultraviolet difference spectra and fluorescence spectra.
At low concentrations of SDS, up to 0.1%, both aggregation and dissociation of
the protein occurs. Only dissocUttion occurs at higher SDS concentrations and is
complete at 0.5% SDS. Viscosity increases sharply up to 0.15% SDS, remains
constant between 0.15 and 0.30% and then increases markedly again. SDS
induces also difference spectra with minima at 280, 288 and 295 nm. Fluorescence
emission intensity increases at SDS concentrations <0.05% and
quenching occurs at higher SDS concentrations. The results suggest that SDS
causes association, dissociation and denaturation of the protein molecule.