2) Protein Sequencing using Sanger's reagent and dansyl chloride

Here, the N terminal amino acid of the protein is labeled by dyes like Sanger's reagent (fluoro-dinitrobenzene) or dansyl chloride. The labeled protein is then hydrolyzed by 6M HCl at 110 ºC by the above mentioned method and loaded in Dowex 50 column and the elution profile is matched with the standard profile obtained from FNB or DNSCl derivative of all the amino acids, to obtain the N terminal amino acid. The reagents produce coloured derivatives which can be easily detected by absorbance (Fig. 6).

Figure source: Wikipedia

Figure 6: Protein Sequencing using Sanger's reagent and dansyl chloride