THE DETERMINATION OF EPSILON-AMINO GROUPS IN SOLUBLE AND POORLY SOLUBLE PROTEINACEOUS MATERIALS BY A SPECTROPHOTOMETRIC METHOD USING TRINITROBENZENESULFONIC ACID

A procedure using 2,4,6-trinitrobenzenesulfonic acid (TNBS) for the determination of ε{lunate}-amino groups in soluble and poorly soluble proteinaceous materials is presented. The major modification from previous procedures is an extended TNBS reaction time to allow a stoichiometric reaction with amino groups. In addition, autoclave hydrolysis is used to assure sample dissolution for spectrophotometric measurements. The assay accuracy was evaluated by determining ε{lunate}-amino groups of insulin and bovine albumin. The determinations differed from literature values by ≤3.3%. The ε{lunate}-amino group content of Type B gelatin was found to be 33.0 mol/gelatin molecule of 1000 residues and is in agreement with similar source gelatins and collagen. The coefficient of variation for determinations on all three materials was ≤5.3%. The assay should be applicable to a broad range of proteinaceous materials. © 1992.