High-field NMR T2 relaxation mechanism in D2O solutions of albumin

400 MHz NMR T2 in D2O solutions of albumin and pure D2O were measured at different temperatures. A relation, based on the chemical exchange between bound HDO and non-exchangeable protein protons, was derived theoretically for the contributions of bound HDO [Pb(1/T2b)]. A second relation was also derived theoretically by considering spin-rotation interactions between bound HDO and surrounding protein protons. The Pb(1/T2b) values in albumin solutions were then determined by replacing experimental data into the fi rst relation. The values of the 1/T2 and Pb(1/T2b) in albumin solutions increase linearly with temperature(T), whereas the 1/T2 in D2O decreases with T. In addition, the spin rotation correlation times were calculated from the second relation. The dipolar correlation time of albumin was then reproduced from the spin-rotation correlation times for confi rmative purposes. In conclusion, the 1/T2 in albumin solutions with D2O is caused by spin-rotation interactions

Observation of triplet traces obtained with Inversion Recovery method in both residual water and H2O D2O albumin mixture by using 400 MHz Proton NMR

NMR studies involving H2O/D2O mixtures are mainly based on a single spectrum of water. However, some recent papers have revealed the presence of an HDO triplet in H2O/D2O, which is caused by the splittings of H2O signal by deuterium (D). Observation of inversion recovery (IR) traces of this triplet should be very useful for analyzing relaxation data in such mixtures. In this work, in order to obtain the traces, inversion recovery signal intensities of residual water and a mixture of 0.10 H2O and 0.90 D2O were acquired versus a set of short delay times in the presence or absense of 0.2 g albumin. T1 and T2 curves of the same samples were also obtained by using different sets of much longer times for checking the effect of radiation damping on the traces. Experiments were carried out with a 400 MHz proton NMR spectrometer equipped with a topspin programme for relaxation measurements. Inversion recovery data of the traces and T1 curves were obtained with the inversion recovery method, while T2 curves were obtained with the Carr-Purcell-Meiboom-Gill method. Data was processed through an analysis programme of the topspin. Data showed that radiation damping is effectively reduced upon addition of albumin. Furthermore, the data of the residual water- and the mixture with albumin demonstrated the traces of the triplet at the initial part of a single inversion recovery line. Our results suggest that the splitting of water proton signal by deuterium can be detectable by the inversion recovery method for D2O- and the mixture containing albumin

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

In this work the T1 and T2 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 T1 and the T2 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 µg 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