Predicting 1H NMR relaxation in Gd3+-aqua using molecular dynamics simulations

Atomistic molecular dynamics simulations are used to predict H-1 NMR T-1 relaxation of water from paramagnetic Gd3+ ions in solution at 25 degrees C. Simulations of the T-1 relaxivity dispersion function r(1) computed from the Gd3+-H-1 dipole-dipole autocorrelation function agree within similar or equal to 8% of measurements in the range f(0) similar or equal to 5 <-> 500 MHz, without any adjustable parameters in the interpretation of the simulations, and without any relaxation models. The simulation results are discussed in the context of the Solomon-Bloembergen-Morgan inner-sphere relaxation model, and the Hwang-Freed outer-sphere relaxation model. Below f(0) less than or similar to 5 MHz, the simulation overestimates r(1) compared to measurements, which is used to estimate the zero-field electron-spin relaxation time. The simulations show potential for predicting r(1) at high frequencies in chelated Gd3+ contrast-agents used for clinical MRI.

Automated summary

Atomistic molecular dynamics simulations were used to predict the T-1 relaxation of water caused by paramagnetic Gd3+ ions in solution at 25 degrees C. The simulations agreed closely with measurements within a certain frequency range, showing potential for predicting r(1) in chelated Gd3+ contrast agents for clinical MRI.