Quantitation of LMW-GS to HMW-GS Ratio in Wheat Flours

A comparison was made of methods for measuring the LMW/HMW glutenin subunit (GS) ratio for glutenin. A set of near-isogenic wheat lines With the number of HMW-GS varying from 0 to 5 was utilized to provide a wide range of LMW/HMW-GS. Glutenin preparations were obtained from,round whole meal after solubilization of monomeric proteins by dimethyl sulfoxide (DMSO) or 50% propanol or by fraction collection front a preparative SE-HPLC column. Analyses were made oil the reduced glutenin from each of the three preparations by RP-HPLC, SE-HPLC, and SDS-PAGE. Both solvents, DMSO and 50% propanol. extracted appreciable amounts of polymeric protein, thus casting some doubts on the accuracy of the determinations. This problem was largely avoided when the polymeric fraction was collected front the eluate of a total glutenin extract run oil a preparative SE-HPLC column. Less glutenin was removed by the two solvents for lines with a greater number of HMW-GS or with strength-associated HMW-GS 5+10 coded by the ID chromosome. Collection of the polymeric protein in SE-HPLC, followed by separation of the glutenin subunits in RP-HPLC, was the best method for quantitating the LMW/HMW-GS ratio. SE-HPLC gave a separation of the two groups of subunits as well as HMW albumins. RP-HPLC has the potential advantage of being able to quantitate individual subunits.