Cereal Chem 49:572 - 579.  |  VIEW ARTICLE
A Colorimetric Method of Screening Maize Seeds for Lysine Content.

C.-Y. Tsai, L. W. Hansel, and O. E. Nelson. Copyright 1972 by the American Association of Cereal Chemists, Inc. 

A colorimetric method for screening lysine content in seeds of cereal grains is presented. The method utilizes 2-chloro-3,5-dinitropyridine as a reagent for the epsilon-amino group of lysine after enzymatic hydrolysis of the proteins and blocking the alpha-amino groups of the free amino acids with copper. After acidification, the excess 2-chloro-3,5-dinitropyridine is extracted with ethyl acetate. The absorbance at 400 nm. of the epsilon-dinitropyridyl-lysine formed is then measured. The method gives lysine determinations for opaque-2 maize that agree well with lysine determinations for the same samples on the Beckman amino acid analyzer, but are somewhat higher.