Practice question

Amino acid migration during electrophoresis depends on net charge dictated by relationship between buffer pH and isoelectric point. Glutamic acid possesses acidic side chain with pI approximately 3.22 due to two carboxyl groups. At pH 7, well above pI, both alpha and side-chain carboxyls are deprotonated, conferring net negative charge of minus one to minus two. Anions migrate toward positively charged anode under electric field. Basic pI would imply cationic state and cathodal migration, while molecular weight and solubility do not determine direction. Thus acidic pI explains anodal movement of glutamic acid at neutral pH.