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Updated: Jun 7, 2026

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
Published on: December 16, 2013
pH dependence of the conformation of small peptides investigated with two-dimensional vibrational spectroscopy
Adriana Huerta-Viga1, Daniel J Shaw, Sander Woutersen
1Van't Hoff Institute for Molecular Sciences (HIMS), University of Amsterdam, Science Park 904, 1098XH, Amsterdam, The Netherlands.
Abstract:
We investigate how the conformation of small peptides is influenced by the presence or absence of charge on the C-terminus and on the side groups. To this purpose, the conformations of two tripeptides, with acidic and basic side groups, is determined at several pD values using two-dimensional infrared (2DIR) spectroscopy. The investigated pD values are chosen relative to the C-terminal and side-chain pK(a) values in such a way that the C-terminus and side groups are in well-defined protonation states. The measurements are analyzed quantitatively using an excitonic model for the Amide I' mode. From the vibrational coupling and the angle between the Amide I' transition dipoles obtained in this way, the dihedral angles (φ,ψ) of the central C(α) atom are determined. Interestingly, our measurements show that the backbone structure of the peptides is remarkably stable against changing the charges of both the side groups and the C-terminal carboxylate groups. This is probably a consequence of effective screening of the Coulomb interactions between the charged groups by the water molecules between them. We also find that the (φ,ψ) confidence regions obtained from 2DIR measurements can have highly irregular shapes as a consequence of the nonlinear relation between the dihedral angles and the experimentally determined Amide I' coupling and transition-dipole angle.
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