Elimination of Radiation Damping Effects from the NMR Relaxation Curves of H2O/D2O Mixtures Containing Protein and Ions

In this work the T-1 and T-2 curves of H2O/D2O mixtures were obtained for several fractions of H2O and also for different amounts of albumin and manganese. The experiments were carried out with a 400 MHz proton NMR spectrometer. The T-1 and the T-2 curves were determined by the inversion recovery (IR) and Carr-Purcell-Meiboom-Gill (CPMG) sequences, respectively. The relaxation times in residual water and in a mixture with 0.05 ml H2O were found to be reliable either in the presence or in the absence of albumin. The mixtures containing 0.1 ml or higher H2O suffer from radiation damping (RD). RD was removed gradually by addition of albumin or manganese. RD in the protein solution with 0.1 ml H2O was removed by adding 1 mu g of manganese to one ml of solution. The data suggest that the relaxation times in H2O/D2O mixtures are measurable by conventional methods upon the addition of appropriate amounts of manganese and albumin.