Appropriateness of DSS and TSP as internal references for 1H NMR studies of molten globule proteins in aqueous media

A marked dependence of the 1H resonances of TSP and DSS (internal standards) on the concentration of proteins in the molten globule state has been found. This result indicates that TSP and DSS interact with these proteins. Therefore, when the chemical shift is used as an indicator of the residual structure of proteins in the molten globule state, great care must be taken in using TSP and DSS.