Practice question

Detecting oligomeric nature requires comparison of different electrophoretic conditions. Native PAGE preserves non-covalent interactions and quaternary structure, so oligomers migrate as intact complexes with higher apparent molecular weight. Non-reducing SDS-PAGE disrupts non-covalent interactions but retains disulfide bonds, distinguishing disulfide-linked oligomers from non-covalently associated ones. Reducing SDS-PAGE with beta-mercaptoethanol or DTT breaks both interactions, yielding monomeric subunits. Analyzing mobility shifts across all three systems reveals whether protein exists as monomer, disulfide-linked oligomer, or non-covalently associated oligomer, making combined use most informative.