Nuclear Spin Relaxation Parameters of MRI Contrast Agents – Insight from Quantum Mechanical Calculations

Abstract

Keywords: Relaxivity / Hyperfine interactions / Quantum chemistry / Gadolinium / MRI contrast agent Nuclear magnetic relaxation in the presence of paramagnetic centres has gained increasing interest in recent years partly due to its importance for contrast agents in magnetic resonance imaging. Rational design of new more efficient agents is possible as a result of a better understanding of the underlying relaxation mechanisms. Quantum chemical calculations together with molecular dynamics simulations allow obtaining fundamental parameters such as quadrupole coupling constants and hyperfine interaction tensors directly at a molecular level. Recent results are presented on gadolinium(III) ions in aqueous solution and on [Gd(DOTA)(H 2 O)] -, a commercial MRI contrast agent. Isotropic hyperfine coupling

Paramagnetic Relaxation Enhancements in Acetate and Its Fluorine Derivatives Interacting with Gd3+: Complex Formation, Structure, and Transmetallation

“…To sum up, in the case of the similar ligands CF i H 3Ài COO À forming complexes with Gd 3 + , the OS relaxivity has the simple form in Equation (18) and the IS relaxivities are given by Equations (19) and (22) or (23) connecting the PRE measurements with the formation constants of the complexes, their structures and dynamics through T 1M , T 1M2 , t M , t M2 , and the general speciation in the solution as exemplified in Supporting Information Appendices C and D. Therefore, r …”

“…This demonstrates that the complexes GdL (L = ac, mfa, and dfa) and Gdac 2 induce similar OS-PREs of the ac, mfa, dfa, tfa nuclei and supports the approximation of R OS 1p in Equation (18) . For that purpose, we compared the 19 F PREs of tfa in two D 2 O solutions containing markedly different concentrations c tfa = 10 and 100 mm of this ligand, but the same concentration c Gd = 5 mm of Gd 3 + . The effects of the long-range Coulomb attraction between the tfa anion and Gd 3 + were kept independent of the tfa concentration in the two solutions by the presence of a large 0.5 m concentration of supporting electrolyte KCl.…”

“…For that purpose, fluorine is a particularly relevant choice because of its high electronegativity. Moreover, 19 F is a 100 % naturally abundant nucleus with a high gyromagnetic ratio. It has a range of chemical shifts which is much broader than that of 1 H and increases the likelihood of well-resolved lines by overcoming the overlapping problems.…”

“…Its application to investigate paramagnetic centres in bioinorganic solution chemistry was reviewed recently. [6] In magnetic resonance imaging (MRI), it was proposed to image lanthanide Ln 3 + complexes carrying 19 F reporters of short longitudinal relaxation times. [7,8] Among paramagnetic centres, Ln 3 + ions have attracted much attention in past years owing to their nearly identical chemistry and versatile magnetic properties.…”

“…It is absent in standard organic chemistry. Thus, 19 F NMR spectroscopy is a sensitive technique providing selective information on the fluorine molecular environment. It has served in biological and biomedical studies to probe protein structures, [2][3][4] RNA folding, [5] and interactions [2] with proteins.…”