Small Molecule–Macromolecule Interactions as Studied by Optical Rotatory Dispersion–Circular Dichroism

Circular dichroism studies on the interactions of haptens with MOPC-315 and MOPC-460 mouse myeloma proteins and specific antibodies

“…The occurrence of large negative induced CD bands centered in the protein aromatic amino acid absorption region near 300 ±15 nm where bound 2.4-dinitrophenyl and 2,4,6-trinitrophenyl ligands display absorption minima, and the association of extrinsic Cotton effects with strong absorption bands of the haptenic chromophores, in conjunction with red shifts and hypochromic changes in the absorption spectra of bound haptens and the quenching of antibody tryptophan fluorescence by bound ligands, suggest that the optical activity may originate in part by intermolecular dynamic coupling between electronic transitions of the haptenic chromophores and transitions of vicinal tryptophanyl residues of the antibody combining site. gate stereospecific interactions in heme proteins, and between enzymes and coenzymes, substrates, inhibitors, and metal ligands (Ulmer and Vallee, 1965;Urry and Pettegrew, 1967;Nakazawa et al, 1969; Perrin and Hart, 1970;Kági et al, 1971;Fretto and Strickland, 1971a,b). Extrinsic optical activity also may arise from the noncovalent association of symmetric haptenic chromophores and specific antibodies (Rockey et al, 1971a,b;Conway-Jacobs et al, 1970;Reid et al, 1971).…”