How can an antibody selectively detect free amino acids but not those in proteins?
Anti-amino acid IgGs target the α-carboxyl groups of free amino acids. In proteins, α- carboxyl groups are occluded by peptide bonds. Cells containing 0.1-10 mM glutamate are readily detected by SII E100 IgG, but glutamate in proteins is invisible to E100, even though the molar equivalent of glutamate in protein ranges from 50-150 mM.
