Applied Magnetic Resonance最新文献

1-Aminoacyloxygermatran containing a hexacoordinated germanium atom and an amino acid substituent in its structure—L-valine—was synthesized and studied by high resolution ¹H and ¹³C NMR spectroscopy for the first time. Complete signal assignment in two different parts of ¹H spectra containing 8 and 12 overlapped multiplets from –O-CH₂- and –N-CH₂- protons was made by using homonuclear J-COSY, COSY and NOESY methods and on base data of heteronuclear HMQC and HMBC experiments. The spatial structure of the studied 1-aminoacyloxygermatran was proved on the basis of data on interproton through-space interactions obtained from the NOESY spectra at different mixing times from 0.3 to 1.2 s. Simultaneously, along with cross peaks from positive NOEs, exchange cross peaks between germinal protons of different -O-CH₂- groups were found in the same spectra, thus indicating the existence of a slow (in the NMR time scale) dynamic process in this compound associated with rearrangements within the atranium cycle.

The 1,10-phenanthrocyanines of d-elements were investigated by ESR spectroscopy both in the solid (glassy) state and in solutions. These are coordination compounds of a new structural class of apocyanines: chromophore binuclear cation complexes [M²⁺L_n(µ-PC)]₂X_m (M²⁺ = Zn²⁺, Cd²⁺, Co²⁺, Pd²⁺and Pt²⁺; L = 1,10-phenanthroline, 2,9-Me₂-1,10-phenanthroline, pyridine; X = AcO⁻, Cl⁻) with electron-rich bridged 1,10-phenanthrocyanine ligands µ-PC. They are presented as soft colloidal glasses capable of acting as inhibitors of tumor cell proliferation, fungicides and DNA complexones. The study of them by ESR spectroscopy showed that one of the possible mechanisms for the formation of spin centers is thermally directed singlet–triplet S₀ → T_low.-transitions.

Monitoring of skin scar thickness and structural properties is desirable when assessing the efficacy of the healing process. In this work, we report the use of single-sided, low-field nuclear magnetic resonance (NMR) for the analysis of the thickness and collagen structure of healthy and scarred skin. Acquisition of T₂ relaxation profiles was proven to provide quantification of porcine skin thickness as accurate as standard histological techniques. Subsequent analysis of human participants highlighted the utility of this technique for identifying different types of scar and in identifying differences between the thickness of moderate hypertrophic scars and healthy skin. Using bead packings as a model system, determination of the surface-to-volume (S/V) ratio and tortuosity (k) was successfully measured on the single-sided apparatus based on time-resolved diffusion analysis. Application of this method to human skin was able to detect regional differences in collagen structures, consistent with qualitative expectations. It was also able to differentiate between healthy and scarred skin tissue. Preliminary results indicated that scarred tissue exhibited decreased S/V ratios and tortuosities, which is coherent with the formation of less-aligned collagen within scar tissue and indicated the potential for this technique to differentiate scar types. This novel application of single-sided low-field NMR has the potential to be deployed in clinical settings for the differentiation of scar types and for the assessment and monitoring of skin scarring and healing.

This paper reviews compact MRI systems developed at the University of Tsukuba between 1986 and 2018. The key technologies for the compact MRI systems are suitable portable MRI consoles and permanent magnets. For the portable consoles the central problem that had to be solved was the introduction of a pulse programmer using a digital signal processor board, and a digital synthesizer board both running under the Windows operating system. The electronics and software developed at the University of Tsukuba and the permanent magnets manufactured by Sumitomo Special Metals Company (SSMC, later NEOMAX engineering) enabled us to develop a variety of compact MRI systems for both clinical and non-clinical applications.

Hyperpolarization in nuclear magnetic resonance boosts the signals by several orders of magnitude. Using the singlet spin order of parahydrogen to create large non-equilibrium spin polarization is a fast approach to obtain hyperpolarized metabolites in seconds. In recent years, it has attracted particular interest in the field of biomedicine because signal-enhanced and ¹³C-enriched metabolites allow for real-time metabolic investigations in combination with imaging in vivo. With this, metabolism can be traced and characterized with spatial selectivity in the body. Here, we introduce a method to use signal-enhanced metabolites to study multiple organs in separate injections to obtain real-time kinetics in vivo of these organs. Using hyperpolarized 1-¹³C-pyruvate, we measured the kinetics of the conversion from pyruvate to lactate in the brain and the liver of mice. This we did by injecting the hyperpolarized pyruvate two times within half an hour and using each injection to measure the spectra of one region of interest. Organ cross-talk and especially how different organs affect each other in diseases is of major interest and poorly understood, because of the high complexity of biological systems. With the proof-of-principle study provided here, we are introducing a new tool to study organ-related interaction in vivo. It allows the characterization of different organs of the same animal within half an hour, which is enabled by the fast signal enhancement achieved with parahydrogen.

Magnetic resonance imaging (MRI) is a unique tool for operando studies owing to its non-invasive manner of signal detection. MRI can provide information about structure of the reactor, distribution of the reagents and products in the reactor, and heat and mass transport processes. However, the heterogeneous solid phase of a catalyst in a reactor largely distorts the static magnetic field of an MRI instrument, which leads to a major loss in spectroscopic resolution and measurement sensitivity. On top of that, many chemical reactions involve gases, so that the reduced spin density compared to liquids is yet another complication in such studies. To overcome these challenges, a proper choice of model catalytic reactors for NMR-based experiments is required. In this study, the configuration of model catalytic reactors was varied to explore its effect on the spatially resolved ¹H NMR spectra acquired during heterogeneous hydrogenation of propene to propane with parahydrogen over several supported metal catalysts. The results demonstrate that a judicial choice of a reactor geometry in combination with signal enhancement provided by parahydrogen makes such studies feasible and informative.

The dynamics of H₂O molecules confined in mesopores of about 3.4 nm in size, formed by amorphous SiO₂ pillars separating 2D mordenite nanolayers, was probed by ¹H nuclear magnetic relaxation. ¹H nuclear magnetic resonance (NMR) spectra evidence the presence of water with different local surroundings and mobility. The temperature dependence of ¹H spin–lattice relaxation T₁ and relaxation in rotating frame T_1ρ indicate the complex behavior of nanoconfined water that can be characterized by different activation energies: freezing (29 kJ/mol), fast rotation (12 kJ/mol), and translational motion (23.6 kJ/mol).

Domain sizes in complex polymer materials on the 2- to 400-nm scale can be probed by ¹H spin diffusion NMR with ¹³C detection, which may be competitive with microscopy. In glassy systems, two-dimensional ¹H–¹³C heteronuclear correlation (HetCor) NMR with ¹H spin diffusion is the method of choice. Limits to its applicability have been overcome here by improved data analysis. Single-spectrum referencing eliminates the need for asymptotic equilibration and expands the range of accessible domain sizes to long periods of ~ 400 nm and makes time-consuming measurements with series of mixing times unnecessary. Systematic ¹H peak overlap correction in two-domain systems after local equilibration within 3 ms greatly expands the applicability of quantitative long-period determination from HetCor NMR with ¹H spin diffusion. It usually works even if the ¹H spectra of the two components are fully overlapped, as long as their fractional intensity contributions to at least one ¹H peak are distinctly different. This is documented for microphase-separated diblock copolymers of polystyrene and PMMA (alkyl slices) and of polystyrene and poly(4-vinyl pyridine), a polystyrene analogue. Based on extensive spin diffusion simulations utilizing coarse graining to reduce simulation times, convenient graphs are presented that enable conversion of a measured equilibration percentage to a tight range of minimum and maximum long period, as a robust, model-independent result.