QUANTIFICATION OF GLUTENIN SUBUNITS BY SEQUENTIAL ACETONE PRECIPITATION AND BY SODIUM DODECYL-SULFATE POLYACRYLAMIDE-GEL ELECTROPHORESIS (SDS-PAGE) COUPLED WITH DENSITOMETRY USING A KNOWN QUANTITY OF GLUTENINSAS A STANDARD

Glutenin subunit groups (high molecular weight glutenin subunits, [HMW -GS]; low molecular weight glutenin subunits [LMW-GS]) were quantified by a sequential acetone precipitation method and by sodium dodecyl su lfate polyacrylamide,eel electrophoresis (SDS-PAGE) coupled with densi tometry using a known quantity of extractable glutenin proteins as a q uantitative standard. The average quantity of extractable HMW-GS analy zed in 17 soft wheat patent flours was 8.46 and 7.26% of flour protein by the sequential acetone precipitation and densitometric methods, re spectively, whereas the average quantity of extractable LMW-GS was 15. 29% of flour protein by the sequential acetone precipitation method an d 17.07% of flour protein by the densitometric method. The mean total quantities of extractable glutenin subunits in the 17 flour samples de termined by these two methods were 23.75 and 24.33%, respectively. The re were no significant differences between the two methods (P > 0.05) in the quantities of the total glutenins determined. However, the quan tities of HMW-GS, LMW-GS, and total glutenin subunits determined by ea ch of the procedures were highly correlated. The densitometric quantif ication of glutenin subunit groups with the aid of a known quantity of glutenin proteins as a quantitative standard was shown to be an effec tive method because of its speed, small sample size, reliability, and simultaneous quantification and characterization of glutenin subunits.