Several techniques are available for carrying out amino acid analysis. The amide bonds of proteins and peptides can be hydrolyzed in acidic or basic aqueous solutions, then separated by chromatography and analyzed. Which statement is true?

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Amino acid analysis gives the relative amounts of each amino acid residue. Hydrolyzed amino acids react with ninhydrin or OPA (ortho-phthalaldehyde) and the resulting products can be analyzed by various chromatographic techniques such as ion-exchange or reverse-phase HPLC. The order of amino acid residues can be determined by techniques such as Edman degradation or mass spectrometry. AQC-NHS (6-aminoquinolyl-N-hydroxysuccinimidyl carbamate) is a reagent used for amino acid derivatization prior to HPLC analysis, but it does not react with hydrolyzed amino acids. In C18-HPLC, the amino acids with nonpolar side chains (such as alanine, isoleucine, and valine) are absorbed more strongly on the stationary phase.

Several Techniques Are Available for Carrying Out Amino Acid Analysis