New NMR Methods For Determination Of Self-Diffusion Coefficient And Relaxation Times

The aim of this dissertation is to develop new NMR pulse sequences for the determination of molecular self-diffusion coefficients and multiple-quantum relaxation time, and to study the multiple-component relaxation behaviors of rat brain tissue water. The results are summarized as followings.1. Determination of Molecular Self-Diffusion Coefficient Using Multiple Spin-Echo NMR Spectroscopy With Removal of Convection and Background Gradient ArtifactsPulsed-field-gradient NMR (PFG NMR) has been proved valuable for the study of both diffusive and coherent molecular motions. In order to improve the accurate of measurement, the artifacts, such as eddy current, thermal convection, background gradient must be considered both experimentally and methodologically. In the Chapter 2 of this dissertation, new pulse sequences were introduced, in which CPMG and bipolar gradient pulses have been implemented into pulsed-filed-gradients spin-echo NMR spectroscopy, and is used to measure the self-diffusion coefficient of metabolites in bio-fluids. The double gradient spin-echo is shown to be useful in reducing the thermal convection that can cause over-estimation of the diffusion coefficients, and insensitive to background gradient artifacts. In addition, the CPMG sequence enables longer diffusion periods (up to seconds) to be used without phase distortion. Therefore, the proposed method is suitable for determining the diffusion coefficients of small metabolites in bio-fluids, where the resonance of large molecules, such as proteins, are suppressed during the spin-echo period due to their fast relaxation.2. Multiple-Quantum J-Resolved NMR Spectroscopy (MQ-JRES): Measurement of...