Nuclear magnetic resonance study of poly(γ-glutamic acid)–cu(II) and mn(II) complexes

Abstract

The interactions of poly(γ-glutamic acid) with Cu(II) and Mn(II) ions in aqueous solution were studied by 1H and 13C nuclear magnetic resonances. The addition of Cu(II) ions to poly(γ-glutamic acid) solutionselectively broadens the α-proton signal, the side-chain carboxyl carbon signal, and the α-carbon signal. The addition of Mn(II) selectively broadens the α-proton signal, the side-chain carboxyl carbon signal, and the main chain carbonyl carbon signal. It is concluded that the oxygen atom of the side-chain carboxyl group of poly(γ-glutamic acid) binds to Cu(II) and Mn(II) ions in aqueous solution at neutral pH and at room temperature. It is also probable that the nitrogenatom of the amide group binds to Cu(II) and that the oxygen atom of the carbonyl group binds to Mn(II). These groups bound to Cu(II) and Mn(II) ions undergo rapid exchange between the bound and free states, and the life time of the bound state is short, less than 10-4 s for Mn(II) complex. © 1990, The Society of Polymer Science, Japan. All rights reserved.