Rotational dynamics of copper(II) amino acid complexes by EPR and NMR relaxation methods

Rotational dynamics of the copper(II) bis-complexes with glycine and L-aspartic acid has been studied by EPR and NMR relaxation methods in aqueous solutions at several temperatures. Dynamical parameters obtained by EPR were compared with nuclear magnetic relaxation dispersion (NMRD) results and were found to be in a good agreement. From EPR data dominating trans isomer for Cu(Gly)2 and cis isomer for Cu(L-Asp)2 2- was found. On the basis of distance of closest approach of protons to central ion inferred from NMRD and crystal structure data the average slope angles of axial water molecule to equatorial plane were calculated and axial coordination of only one water molecule in the Cu(L-Asp)2 2- complex was established

Hydration of copper(II) amino acids complexes

© 2017 Wiley Periodicals, Inc. Hydration of the copper(II) bis-complexes with glycine, serine, lysine, and aspartic acid was studied by DFT and MD simulation methods. The distances between copper(II) and water molecules in the 1st and 2nd coordination shells, the average number of water molecules and their mean residence times in the hydration shells were calculated. Good agreement was observed between the values obtained and those found by DFT and NMR relaxation methods. Influence of the functional groups of the ligands and the cis-trans isomerism of the complexes on the structural and dynamical parameters of the hydration shells was displayed and explained. Analysis of the MD trajectories reveals the competition for a copper(II) axial position between water molecules or water molecules and the functional chain groups of the ligands and confirms the suggestion on the pentacoordination of copper(II) in such complexes. MD simulations show that only one axial position of Cu(II) is basically occupied at each time step while in average the coordination number more than 5 is observed

Complex formation, chemical exchange, species structure, and stereoselective effects in the copper(II)- L/DL-histidine systems

The formation of copper(ii) complexes with l- and dl-histidine (HisH) has been studied by means of pH-potentiometry and spectrophotometry over a wide range of pH (2-14), ligand-to-metal ratio (1:1-15:1), and temperature (15-55°C) in aqueous solutions with 1.0 mol dm -3 KNO 3 as background. Formation constants and spectral characteristics of 13 complex types were found. Fine stereoselective effects have been detected with preferential coordination of two ligands with identical configuration in Cu(His)(HisH) + and opposite configuration in Cu(His) 2. The stereoselective effect for Cu(His)(HisH) + is explained by hydrogen bond formation between the carboxyl and imidazolyl groups of neighboring ligands at cis-arrangement of amino groups (3N eq-form). The opposite sign of stereoselective effect for Cu(His) 2 is derived from favourable axial coordination of the imidazole group in meso-form with cis-structure (3N eqN ax-form). A significant tetrahedral distortion was revealed for the first time in the prevalent cis-isomer of the Cu(l-His) 2 4N eq-form. These findings were confirmed by EPR data and DFT computations at the B3LYP/TZVP level. The prevalence of cis-isomers for these complexes has been assigned to the rather strong trans effect of the amino groups. The structures of other detected complexes are briefly discussed on the basis of spectroscopic data. Chemical exchange reactions in the copper(ii)- l/dl-hishidine systems have been investigated by the NMR relaxation of water protons. A unique proton exchange reaction with short-term proton dissociation from the coordinated imidazolyl group catalyzed by hydroxide ion was characterised for the first time. The discovered enantioselective effects in the ligand exchange reactions between Cu(His) 2 and HisH or His - species were attributed to the associative substitution mechanism. © 2012 The Royal Society of Chemistry

Spatial structures of tripeptides glycylglycyl-l-histidine and glycylglycyl-l-tyrosine based on residual dipolar couplings and quantum-chemical computations

A novel approach to the determination of the spatial structure of oligopeptides on the basis of an analysis of the residual dipolar couplings 1H-13C assisted by quantum-chemical computations with considering solvent effects is proposed to characterize the conformations of the tripeptides GlyGlyHis and GlyGlyTyr with significant folding of the latter to left-handed helix. © 2011 Mendeleev Communications. All rights reserved

Structure and Dynamics of Solvation Shells of Copper(II) Complexes with N,O-Containing Ligands

© 2015 American Chemical Society. EPR, NMR relaxation methods, and DFT calculations were jointly used to investigate the structural and dynamical characteristics of solvation shells of copper(II) complexes with iminodiacetic acid, glycylglycine, and glycyglycylglycine in comparison with the copper(II) bis-glycinate studied previously. A strong trans influence of deprotonated peptide nitrogen was revealed in EPR spectra parameters of copper(II) complexes with oligopeptides. With models of the experimental NMRD data and literature X-ray structural information, it was suggested that only one water molecule coordinates in axial position of copper(II) complexes with glycine and di- and triglycine (Cu(Gly)2, Cu(GGH-1), and Cu(GGGH-2)-), and the copper ion in these complexes is pentacoordinated, while in the iminodiacetate complex, Cu(IDA), both apical positions can be occupied by solute molecules. The obtained structural results were confirmed by DFT calculations of structures of studied compounds using different functionals and basis sets. It was shown that the donor ability of equatorial ligands and trans influence have an effect on the characteristics of the axial water bond. With increasing donor strength of equatorial ligands, pentacoordination of copper(II) complexes in water solutions becomes more preferable

Rotational dynamics of copper(II) amino acid complexes by EPR and NMR relaxation methods

Rotational dynamics of the copper(II) bis-complexes with glycine and L-aspartic acid has been studied by EPR and NMR relaxation methods in aqueous solutions at several temperatures. Dynamical parameters obtained by EPR were compared with nuclear magnetic relaxation dispersion (NMRD) results and were found to be in a good agreement. From EPR data dominating trans isomer for Cu(Gly)2 and cis isomer for Cu(L-Asp)2 2- was found. On the basis of distance of closest approach of protons to central ion inferred from NMRD and crystal structure data the average slope angles of axial water molecule to equatorial plane were calculated and axial coordination of only one water molecule in the Cu(L-Asp)2 2- complex was established

Rotational dynamics of copper(II) amino acid complexes by EPR and NMR relaxation methods

Rotational dynamics of the copper(II) bis-complexes with glycine and L-aspartic acid has been studied by EPR and NMR relaxation methods in aqueous solutions at several temperatures. Dynamical parameters obtained by EPR were compared with nuclear magnetic relaxation dispersion (NMRD) results and were found to be in a good agreement. From EPR data dominating trans isomer for Cu(Gly)2 and cis isomer for Cu(L-Asp)2 2- was found. On the basis of distance of closest approach of protons to central ion inferred from NMRD and crystal structure data the average slope angles of axial water molecule to equatorial plane were calculated and axial coordination of only one water molecule in the Cu(L-Asp)2 2- complex was established

Rotational dynamics of copper(II) amino acid complexes by EPR and NMR relaxation methods

Rotational dynamics of the copper(II) bis-complexes with glycine and L-aspartic acid has been studied by EPR and NMR relaxation methods in aqueous solutions at several temperatures. Dynamical parameters obtained by EPR were compared with nuclear magnetic relaxation dispersion (NMRD) results and were found to be in a good agreement. From EPR data dominating trans isomer for Cu(Gly)2 and cis isomer for Cu(L-Asp)2 2- was found. On the basis of distance of closest approach of protons to central ion inferred from NMRD and crystal structure data the average slope angles of axial water molecule to equatorial plane were calculated and axial coordination of only one water molecule in the Cu(L-Asp)2 2- complex was established

Hydration of copper(II) amino acids complexes

© 2017 Wiley Periodicals, Inc. Hydration of the copper(II) bis-complexes with glycine, serine, lysine, and aspartic acid was studied by DFT and MD simulation methods. The distances between copper(II) and water molecules in the 1st and 2nd coordination shells, the average number of water molecules and their mean residence times in the hydration shells were calculated. Good agreement was observed between the values obtained and those found by DFT and NMR relaxation methods. Influence of the functional groups of the ligands and the cis-trans isomerism of the complexes on the structural and dynamical parameters of the hydration shells was displayed and explained. Analysis of the MD trajectories reveals the competition for a copper(II) axial position between water molecules or water molecules and the functional chain groups of the ligands and confirms the suggestion on the pentacoordination of copper(II) in such complexes. MD simulations show that only one axial position of Cu(II) is basically occupied at each time step while in average the coordination number more than 5 is observed

Hydration of copper(II) amino acids complexes

© 2017 Wiley Periodicals, Inc. Hydration of the copper(II) bis-complexes with glycine, serine, lysine, and aspartic acid was studied by DFT and MD simulation methods. The distances between copper(II) and water molecules in the 1st and 2nd coordination shells, the average number of water molecules and their mean residence times in the hydration shells were calculated. Good agreement was observed between the values obtained and those found by DFT and NMR relaxation methods. Influence of the functional groups of the ligands and the cis-trans isomerism of the complexes on the structural and dynamical parameters of the hydration shells was displayed and explained. Analysis of the MD trajectories reveals the competition for a copper(II) axial position between water molecules or water molecules and the functional chain groups of the ligands and confirms the suggestion on the pentacoordination of copper(II) in such complexes. MD simulations show that only one axial position of Cu(II) is basically occupied at each time step while in average the coordination number more than 5 is observed