Available lysine. II.—Determination of available lysine in feedingstuffs by dinitrophenylation

A method for determining non‐N‐terminal lysine by hydrolysis of dinitrophenylated proteins, has been examined critically. Sample concentrations and the presence of carbohydrate at hydrolysis were shown to effect the apparent amount of non‐N‐terminal lysine found. ϵ‐DNP‐lysine can be partly protected from destruction by fluorodinitrobenzene and by dinitrophenol. The method was applied to protein fractions and to feedingstuffs and was compared with that developed by Carpenter; reasons for discrepancies are discussed.