CHE 4341 Lecture Notes - Lecture 6: Elastase, Chymotrypsin, Ionization
Document Summary
Chapter 5 lecture 1 : proteins, protein. [3 basic steps: separate into individual polypeptide chains by cleaving disulfide bonds on each chain, end terminus analysis, sequencing. Cleave disulfide bonds [ if more than 1 chain ] 1 w/performic acid it will change cysteine to cystic acid. 2a: react w/ xs thiol to cleave disulfide bonds. Carboxypeptidases are exopeptidases (exoproteases) that cleave aa"s at the c-terminus. Exopeptidases : cleave protein peptide bonds from end inwards. Disadvantage: have to use acid this hydrolyzes whole peptide to get dansyl derivatived aa. Note: lysine also reacts w/these reagents because of its nh2 side chain. Edman degradation w/pitc can be used for n-terminus detection. Step 3: protein sequencing: edman degradation using pitc to solve each aa & its" order. Tfa reaction is self cleaving, strong h+ hydrolysis is not req. Leaves the remaining polypeptide in aqueous solution for another round of rxn w/pitc. Today this method is automated into a protein sequencer .
