MALDI-TOF approach to measure cysteine number of wheat glutenin subunits

In the current study, we established a fast method to accurately measure the number of cysteine residues in high molecular weight glutenin subunits. An alkylation regent, 4-vinylpyridine (4-vp), was used to treat the proteins during extraction. For every cysteine residue in a protein, such treatment increases its molecular mass value by 105.14 Da, which can be accurately determined by MALDI-TOF equipment. Based on the changes of the molecular mass value after 4-vp treatment, the number of cysteine residue can be reliably determined. We found that this method is also useful in studying non-glutenin proteins such as lupin seed storage proteins. This method is particularly valuable when the number of cysteine residue is of importance