Protein sequencing involves determining the order of amino acids in a protein chain. [1] Edman degradation is commonly used for N-terminal sequencing and involves labeling the N-terminal amino acid, removing it, and identifying it through chromatography and mass spectrometry. [2] The protein must first be purified and digested before Edman degradation can begin. [3] Mass spectrometry is used to analyze the separated amino acid derivatives and identify the sequence.