Interaction of Cyclosporin C with Dy3+ Ions in Acetonitrile and in Complex with Dodecylphosphocholine Micelles Determined by NMR Spectroscopy

The spectral characteristics of cyclosporin C (CsC) with the addition of Dy³⁺ ions in acetonitrile (CD₃CN) and CsC with Dy³⁺ incorporated into dodecylphosphocholine (DPC) micelle in deuterated water were investigated by high-resolution NMR spectroscopy. The study was focused on the interaction between Dy³⁺ ions and CsC molecules in different environments. Using a combination of one-dimensional and two-dimensional NMR techniques, we obtained information on the spatial features of the peptide molecule and the interaction between CsC and the metal ion. The non-uniform effect of the metal ion on different NMR signals of CsC was observed. The paramagnetic attenuation parameter was calculated for the amide, alpha, and beta protons of CsC upon the addition of Dy³⁺. The metal ion was found to interact with the polar part of the DPC micelle, and the ion also has a significant effect on the NMR signals of amino acid residues from Sar₃ to d-Ala₈. This pattern is reproduced in both environments studied here and also agrees with earlier investigations of the CsA-Dy³⁺ complex.