Improved method for isolating and quantitating alpha-amino nitrogen as nonprotein, true protein, salt-soluble proteins, zeins, and true glutelins in maize endosperm
J. Landry et al., Improved method for isolating and quantitating alpha-amino nitrogen as nonprotein, true protein, salt-soluble proteins, zeins, and true glutelins in maize endosperm, CEREAL CHEM, 77(5), 2000, pp. 620-626
The conventional Landry-Moureaux method for selective extraction of maize p
roteins was modified by reducing the contact time of meal with extractants
and by removing 55% 2-propanol as extractant. The new procedure, coupled wi
th a method for quantitating protein at microgram level, was used for asses
sing 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 subsequen
tly with salt plus reductant were minor and poor in lysine (1 mol%). They w
ere associated with zeins. Comparison of present data with those available
in the literature showed a close similarity for a given genotype between th
e percentage of total a-amino nitrogen extracted by 2-propanol plus reducta
nt than by salt plus reductant under conditions of the modified procedure a
nd 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 quantitatin
g cc-amino nitrogen as nonprotein, true protein, salt-soluble proteins, zei
ns, and true glutelins in any sample of maize endosperm.