Cereal Chem 66:135-138   |  VIEW ARTICLE

A Note: High-Lysine Barley Screening with Fluorometry and Endoproteolytic Assays.

H. Ahokas and L. Naskali. Copyright 1989 by the American Association of Cereal Chemists, Inc. 

2-(N-Morpholino)ethanesulfonic acid-buffered sodium dodecyl sulfate extracts of barley meal were assayed with two fluorometric methods, using either fluorescamine or o-phthaladehyde as the fluorochrome. Both methods, especially fluorescamine, showed a good agreement with the lysine content but a less strong correlation with protein content. In a third assay, digestion of meal samples with endoproteinase Lys-C, hydrolyzing polypeptides at the carboxyl end of lysyl residues, resulted in an increase of amino terminals. This increase was detected with ninhydrin. Ninhydrin absorbances showed a linear correlation with lysine content. The protein content of the digested or undigested extracts could be reliably estimated from the absorbances at 215 and 225 nm.