A biochemist treats an antibody with a reducing agent in order to separate its heavy and light chains for analysis. Which structural feature does the reagent attack?

Core Concept

Antibody chains are fastened to one another and stabilized internally by sulfur-sulfur covalent bonds formed when pairs of cysteine sulfhydryl groups oxidize. Reducing agents add electrons and hydrogens back, splitting each bridge into two free sulfhydryls, so the chains fall apart without any peptide bond being touched. Every separated chain keeps its complete primary sequence, which is precisely why this technique works for analyzing subunit composition.