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Improved method for isolating and quantitating alpha-amino nitrogen as nonprotein, true protein, salt-soluble proteins, zeins, and true glutelins in maize endosperm
- Landry, J., Delhaye, S., Damerval, C.
- Cereal chemistry 2000 v.77 no.5 pp. 620-626
- corn, endosperm, genotype, glutelins, isopropyl alcohol, lysine, nitrogen, nonprotein nitrogen, reducing agents, true protein, zein
- The conventional Landry-Moureaux method for selective extraction of maize proteins was modified by reducing the contact time of meal with extractants and by removing 55% 2-propanol as extractant. The new procedure, coupled with a method for quantitating protein at microgram level, was used for assessing the nitrogen distribution of four soluble protein fractions present in 100-mg samples of endosperm originating from six maize inbreds and opaque-2 versions. Proteins extracted with 55% 2-propanol plus reductant were made up of alpha-, beta-, gamma-, and delta-zeins. Proteins extracted subsequently with salt plus reductant were minor and poor in lysine (1 mol%). They were associated with zeins. Comparison of present data with those available in the literature showed a close similarity for a given genotype between the percentage of total alpha-amino nitrogen extracted by 2-propanol plus reductant than by salt plus reductant under conditions of the modified procedure and that of total Kjeldhal nitrogen extracted by 2-propanol with and without reductant, and by salt plus reductant, using the conventional procedure. A simplified protocol was described and tested for isolating and quantitating alpha-amino nitrogen as nonprotein, true protein, salt-soluble proteins, zeins, and true glutelins in any sample of maize endosperm.