A selective 2D intermolecular zero-quantum coherences pulse sequence, SEL-HOMOGENIZED sequence, was developed for high-resolution NMR spectra in inhomogeneous fields. The sequence designed to effectively suppress strong solvent signals and other trivial signals can greatly decrease the t1 noise artifacts. In the homogeneous-like 1D spectrum extracted from the 2D data, chemical shifts, coupling constants, multiplicity patterns, and relative peak areas are almost independent of the magnetic field inhomogeneity. Compared to the HOMOGENIZED sequence, the new sequence provides a total sensitivity enhancement of two times. It was also demonstrated that the theoretical predictions were in excellent agreement with the experimental results.

The behaviors of molecular self-diffusion were simulated in complex spin systems with both intra-molecular scalar couplings and inter-molecular dipolar couplings in liquid nuclear magnetic resonance (NMR). The simulation algorithm was based on a combination of the non-linear Bloch equations, product operator matrix, and finite difference method. The simulated results reveal different diffusion behaviors of inter-and intra-molecular multiple-quantum coherences, coincident with theoretical predictions and experimental measurements. Compared with the Monte Carlo method, the finite difference method is more precise and efficient for simulating diffusion behaviors of multiple-quantum coherences.

A novel MRI method based on the intermolecular double-quantum coherence (DQC) for soft tissues is described. DQC images of human brain were obtained for the first time on a whole-body 1.5 T scanner. The combination of quantum and classical formalisms was used to characterize multiple-quantum coherences, and to aid in the design of a DQC imaging sequence. The theoretical analysis suggests that signals from the intermolecular DQCs have higher sensitivity than those from the zeroquantum coherence (ZQC) for human brain, and the sensitivity increases with increased field strength. The DQC signal may provide a new form of contrast for MRI.

To simulate the types of coordination and solution structures of the active site of haloperoxidases, the interaction systems between diperoxovanadate complexes [OV(O2)2L]n-(n=1 or 3, L=oxalate or H2O) and a series of histidine-like ligands in solution have been studied by using 1D multinuclear (1H, 13C, and 51V) NMR, 2D diffusion ordered spectroscopy, and variable-temperature NMR in 0.15 mol/L NaCl ionic medium, representing the physiological conditions of human blood. Some direct NMR data are given for the first time. The reactivity among the histidinelike ligands is imidazole>2-methylimidazole>carnosine≈4-methylimidazole>histidine. Competitive coordinationinteractions result in a series of new peroxovanadate species [OV(O2)2L']- (L'=histidine-like ligands). When theligands are 4-methylimidazole, histidine, and carnosine, a pair of isomers have been observed, which are attributedto different types of coordination between vanadium atom and ligands. The results of density functional theorycalculations provided a reasonable explanation on the relative reactivity of the histidine-like ligands and the molarratios of isomers. Theoretical results signify the importance of the solvation effect for the reactivity and stability of the interaction systems.