NMR System Research Articles

Bi-2223 Innermost Coil for 1.03 GHz NMR Magnet

Because of their high critical fields, high- <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> superconductors (HTS) are considered to be the only solution to dramatically increase the highest fields of NMR magnets. We have successfully demonstrated that a 500 MHz HTS/LTS NMR system with a Bi-2223 innermost coil could be used for solution NMR in a driven-mode operation. As the next step, the upgrade of the 920 MHz NMR system installed at the Tsukuba Magnet Laboratory is underway. The innermost Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn coil has been replaced by a Bi-2223 coil. The coil was fabricated as a layer-wound coil using five Bi-2223 conductors reinforced with bronze tapes. It was connected in series with the outer Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn and NbTi coils. The magnet is expected to generate a field of 24.2 T (1.03 GHz of <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> H resonance frequency) at an operating current of 244.4 A. The test using the Bi-2223 coil and the outer Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn coils in combination was successfully carried out. The coil has been installed in the 1.03 GHz NMR magnet. Its cooling and operation are scheduled to take place within Fiscal Year 2010.

An accurate optical technique for measuring the nuclear polarisation of 3He gas

In the metastability exchange optical pumping cells of our on-site production unit and of our other experimental set-ups, we use a light absorption technique to measure the 3He nuclear polarisation. It involves weak probe beams at 1083 nm, that are either perpendicular or parallel to the magnetic field and cell axis, with suitable light polarisations. When metastability exchange collisions control the populations of the sublevels in the 23S state, absolute values of the 3He ground state nuclear polarisation are directly inferred from the ratio of the absorption rates measured for these probe beams. Our report focuses on the transverse detection scheme for which this ratio, measured at low magnetic field for σ and π light polarisations, hardly depends on gas pressure or the presence of an intense pump beam. This technique has been systematically tested both in pure 3He and isotopic mixtures and it is routinely used for accurate control of the optical pumping efficiency as well as for calibration of the NMR system.

WE-G-220-07: Treatment Assessment for Pulsed Focused Ultrasound Therapy of Prostate Tumor Using a Clinical 1.5T MRI

Purpose: Recent in vivo experiments have showed non‐thermal effects of pulsed focused ultrasound (pFUS) on tumor growth delay. This study investigates the application of a clinical 1.5T MR scanner for treatment assessment of prostate tumors after pFUS treatment, which provides a non‐ invasive and accurate way to measure tumor volume for treatment efficacy evaluation, and also an alternative way for small animaltumor model study that generally requires high‐magnetic‐field MRI facility (e.g., the Bruker NMR system). Methods: A mouse tumor model was developed by implanting LNCaP tumor cells in nude mice prostates. When tumor volume reached ∼130 mm3 on MRI, mice were randomly assigned into two groups (n=8): (1) pFUS treatment; (2) control. MRI‐guided pFUS treatment was performed using InSightec ExAblate 2000 with a 1.5T GE MR scanner. Non‐thermal pFUS was delivered for 60 sec per sonication (1MHz; 25W acoustic power; 10% duty cycle, on/off=0.1/0.9 sec). The body temperature was kept 40% reduction in tumor volume was shown in mice treated with pFUS compared to that for the control mice Conclusion: Clinical 1.5T MRI is able to assess the tumor volume change after pFUS treatment for a small animal model (tumor size: 3–10mm). It may provide an alternative way for treatment assessment for small animal studies. This work is supported by Focused Ultrasound Surgery Foundation, Varian Medical Systems, DOD PC073127 and DOD BC102806.

Structure and function of a HECT domain ubiquitin‐binding site

The Rsp5 ubiquitin ligase contains a non-covalent binding site for ubiquitin within the amino-terminal lobe (N-lobe) of the HECT domain, and the X-ray crystal structure of the HECT-ubiquitin complex has been determined. Hydrophobic patch residues of ubiquitin (L8, I44, V70) were crucial for interaction with Rsp5, and amino-acid alterations at the Rsp5-binding interface resulted in defects in polyubiquitination. Our results support a model in which the N-lobe-binding site acts to localize and orient the distal end of the ubiquitin chain to promote conjugation of the next ubiquitin molecule.

Fractional Bloch equation with delay

In this paper we investigate a fractional generalization of the Bloch equation that includes both fractional derivatives and time delays. The appearance of the fractional derivative on the left side of the Bloch equation encodes a degree of system memory in the dynamic model for magnetization. The introduction of a time delay on the right side of the equation balances the equation by also adding a degree of system memory on the right side of the equation. The analysis of this system shows different stability behavior for the T 1 and the T 2 relaxation processes. The T 1 decay is stable for the range of delays tested (1–100 μs), while the T 2 relaxation in this model exhibited a critical delay (typically 6 μs) above which the system was unstable. Delays are expected to appear in NMR systems, in both the system model and in the signal excitation and detection processes. Therefore, by including both the fractional derivative and finite time delays in the Bloch equation, we believe that we have established a more complete and more realistic model for NMR resonance and relaxation.

Development of portable NMR polarimeter system for polarized HD target

A portable NMR polarimeter system has been developed to measure the polarization of a polarized Hydrogen-Deuteride (HD) target for hadron photoproduction experiments at SPring-8. The polarized HD target is produced at the Research Center for Nuclear Physics (RCNP), Osaka university and is transported to SPring-8. The HD polarization should be monitored at both places. We have constructed the portable NMR polarimeter system by replacing the devices in the conventional system with the software system with PCI eXtensions for Instrumentation (PXI). The weight of the NMR system is downsized from 80 to 7 kg, and the cost is reduced to 25%. We check the performance of the portable NMR polarimeter system. The signal-to-noise ( S/ N) ratio of the NMR signal for the portable system is about 50% of that for the conventional NMR system. This performance of the portable NMR system is proved to be compatible with the conventional NMR system for the polarization measurement.

Energy and superconductors – applications of high-temperature-superconductors

More than 20 years after the discovery of high-temperature-superconductors (HTS) first applications in the energy sector are now becoming commercially attractive. Whereas still high end applications of low-temperature-superconductors (LTS) like NMR or MRI systems are the major drivers for industrial production, HTS based systems promise broader use in energy technology over the next few years. Due to their superior performance HTS materials enable more compact and lighter electric devices as well as an unbeatable improvement in energy efficiency. Moreover new devices like fault current limiters (FCL) are under development and field tests exhibit so far unknown properties for future electric grid design. Prototypes and first commercial systems like cables, generators, motors, FCL were successfully commissioned in the last few years. Based on these test results HTS systems will contribute significantly to the future key challenges in energy technology by reducing CO 2 -emmission due to their outstanding efficiency and to the security of energy supply.

Diagonalization-free implementation of spin relaxation theory for large spin systems

The Liouville space spin relaxation theory equations are reformulated in such a way as to avoid the computationally expensive Hamiltonian diagonalization step, replacing it by numerical evaluation of the integrals in the generalized cumulant expansion. The resulting algorithm is particularly useful in the cases where the static part of the Hamiltonian is dominated by interactions other than Zeeman (e.g. in quadrupolar resonance, low-field EPR and Spin Chemistry). When used together with state space restriction tools, the algorithm reported is capable of computing full relaxation superoperators for NMR systems with more than 15 spins.

Development of a nuclear magnetic resonance system for in situ analysis of hydrogen storage materials under high pressures and temperatures

A NMR system for in situ analysis of hydrogen storage materials under high pressure and temperature conditions was developed. The system consists of a gas pressure and flow rate controlling unit, a temperature controller, a high temperature NMR probe tunable for both (1)H and other nuclei, and a sample tube holder. Sample temperature can be controlled up to 623 K by heated N(2) gas flow. Sample tube atmosphere can be substituted by either H(2) or Ar and can be pressurized up to 1 MPa under constant flow rate up to 100 ml/min. During the NMR measurement, the pressure can be adjusted easily by just handle a back pressure valve. On the blank NMR measurement, (1)H background noise was confirmed to be very low. (1)H and (11)B NMR spectrum of LiBH(4) were successfully observed at high temperature for the demonstration of the system. The intensity of the (1)H NMR spectra of H(2) gas was also confirmed to be proportional to the applied pressure.

NMR Separation of Intra- and Extracellular Compounds Based on Intermolecular Coherences

NMR spectroscopy is a powerful tool for detection and characterization of chemical compounds in biological systems. Its application in pharmaceutical studies in cell cultures, however, has been hampered by the enormous technical challenges in separating intra- from extracellular amounts of one substance. We introduce a novel approach to separate intra- from extracellular NMR signal based on the detection of intermolecular zero-quantum coherences in presence of a chemical shift agent. In a sample of large cells in culture, the investigation of cellular uptake of pharmacological substances becomes feasible. The addition of 10 mM Tm-DOTP to a suspension of 100 Xenopus laevis oocytes resulted in sufficient separation of resonance frequencies between intra- and extracellular water. Upon selective excitation of either intra- or extracellular water signal, only intra- or extracellular components were observed, respectively. The presented localization technique provides intrinsic averaging over a large number of cells, resulting in a significant signal gain. The method works on standard NMR spectrometers, which are available at most scientific research institutions today. On a high-resolution NMR system with a cryoprobe, a 20-fold sensitivity gain was observed as compared to conventionally localized NMR spectroscopy of a single X. laevis oocyte on dedicated NMR microscopes.

Design, Validation, and Implementation of a Rapid-Injection NMR System

A Rapid Injection NMR (RINMR) apparatus has been designed and constructed to allow the observation of fast chemical reactions in real time by NMR spectroscopy. The instrument was designed to allow the rapid (<2 s) injection and mixing of a metered volume of a reagent into a spinning NMR tube followed by rapid acquisition of the data resulting from the evolution of the chemical process. The various design criteria for this universal system included the ability to deliver any chemical reagent at any temperature and allow for the observation of any nucleus. The various challenges associated with the construction and implementation of this instrument are documented along with the validation of the accuracy of the apparatus with respect to volume and temperature. Finally, the ultimate validation and reproducibility of the technique is presented in the form of three case studies that used the instrument to elucidate various aspects of organic reaction mechanisms. The authors urge interested parties to not embark on the construction of their own instrument and invite those whose research problems might be amenable to this kind of analysis to contact the corresponding author for access to the apparatus described herein.

HTS-NMR: Present Status and Future Plan

Using high-T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> superconductors (HTS) is considered to be the only solution to dramatically increase the highest fields of NMR magnets because of their high critical fields. However, it is not easy to apply HTS to an NMR spectrometer (HTS-NMR) because a persistent-mode operation with HTS cannot satisfy the field stability of 0.01 ppm/h at present. To overcome this problem, we are now developing an HTS-NMR spectrometer in a driven-mode operation. As the first step, a layer-wound coil was fabricated with bronze-reinforced Bi-2223 conductors. Instead of the Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn coil, the Bi-2223 coil was installed as the innermost part of an existing NMR magnet. The magnet operated at a field of 11.7 T with a highly stabilized power supply. NMR measurements were carried out, and it was demonstrated that the quality of the multi-dimensional NMR spectra on the protein was equivalent to that obtained with a persistent-mode system. The next step will be to demonstrate its usefulness as a high-field NMR system. The upgrade of the 920 MHz NMR system installed at the Tsukuba Magnet Laboratory is underway. Its innermost coil is scheduled to be replaced by a Bi-2223 layer-wound coil for 2010. Its target field is 24.2 T (1.03 GHz).

The application of frequency swept pulses for the acquisition of nuclear quadrupole resonance spectra

The acquisition of nuclear quadrupole resonance (NQR) spectra with wideband uniform rate and smooth truncation (WURST) pulses is investigated. 75As and 35Cl NQR spectra acquired with the WURST echo sequence are compared to those acquired with standard Hahn-echo sequences and echo sequences which employ composite refocusing pulses. The utility of WURST pulses for locating NQR resonances of unknown frequency is investigated by monitoring the integrated intensity and signal to noise of 35Cl and 75As NQR spectra acquired with transmitter offsets of several hundreds kilohertz from the resonance frequencies. The WURST echo sequence is demonstrated to possess superior excitation bandwidths in comparison to the pulse sequences which employ conventional monochromatic rectangular pulses. The superior excitation bandwidths of the WURST pulses allows for differences in the characteristic impedance of the receiving and excitation circuits of the spectrometer to be detected. Impedance mismatches have previously been reported by Marion and Desvaux [D.J.Y. Marion, H. Desvaux, J. Magn. Reson. (2008) 193(1) 153–157] and Muller et al. [M. Nausner, J. Schlagnitweit, V. Smrecki, X. Yang, A. Jerschow, N. Muller, J. Magn. Reson. (2009) 198(1) 73–79]. In this regard, WURST pulse sequences may afford an efficient new method for experimentally detecting impedance mismatches between receiving and excitation circuits, allowing for the optimization of solids and solution NMR and NQR spectrometer systems. The use of the Carr–Purcell Meiboom–Gill (CPMG) pulse sequence for signal enhancement of NQR spectra acquired with WURST pulses and conventional pulses is also investigated. Finally, the utility of WURST pulses for the acquisition of wideline NQR spectra is demonstrated by acquiring part of the 63/65Cu NQR spectrum of CuCN.

Polymerized Urushiol of the Commercially Available Rhus Product in Korea

Systemic contact dermatitis commonly occurs with the intake of rhus (boiled chicken with rhus) as a health food and a folk medicine to cure gastrointestinal diseases in Korea. Rhus companies insist they have the technology for rhus detoxification. However, the numbers of systemic allergic contact dermatitis patients, caused by rhus, have not decreased. The principle of present techniques for rhus detoxification is the induction of the polymerization of urushiol, but polymerized urushiol may still have antigenicity, although to a diminished degree. The Korean Food and Drug Administration (KFDA) has a regulation to control urushiol use as a food. However, the laboratory method that KFDA uses for detection of rhus can only detect the urushiol monomer. We conducted experiments to detect polymerized urushiol in rhus products, which were considered not to include urushiol by the KFDA. Rhus product approved by the KFDA was separated with chloroform. The chloroform fractionation was accomplished on a recycle HPLC system. Four peaks were achieved and evaporated to give an amorphous powder. Each powder was analyzed on a NMR system and mass spectrometer. The material considered to be urushiol dimer, with a 638 molecular weight (MW), was detected in one of the four powders as per the HPLC peaks. We concluded that commercially available rhus product is comprised of material considered to be urushiol dimer. Therefore, even if the antigenicity of the rhus products is low, this product may cause adverse effects and is not completely detoxified.

Shimmed matching pulses: Simultaneous control of rf and static gradients for inhomogeneity correction

Portable NMR systems generally suffer from poor field homogeneity and are therefore used more commonly for imaging and relaxation measurements rather than for spectroscopy. In recent years, various approaches have been proposed to increase the sample volume that is usable for spectroscopy. These include approaches based on manual shimming and those based on clever combinations of modulated radio frequency and gradient fields. However, this volume remains small and, therefore, of limited utility. We present improved pulses designed to correct for inhomogeneous dispersion across wide ranges of frequency offsets without eliminating chemical shift or spatial encoding. This method, based on the adiabatic double passage, combines the relatively larger corrections available from spatially matched rf gradients [C. Meriles et al., J. Magn. Reson. 164, 177 (2003)]. with the adjustable corrections available from time-modulated static field gradients [D. Topgaard et al., Proc. Natl. Acad. Sci. U.S.A. 101, 17576 (2004)]. We explain the origins of these corrections with a theoretical model that simplifies and expedites the design of the pulse waveforms. We also present a generalized method for evaluating and comparing pulses designed for inhomogeneity correction. Experiments validate this method and support simulations that offer new possibilities for significantly enhanced performance in portable environments.

Warren L. DeLano 21 June 1972–3 November 2009

Warren L. DeLano 21 June 1972–3 November 2009

Gadolinium-containing phosphatidylserine liposomes for molecular imaging of atherosclerosis

Exteriorized phosphatidylserine (PS) residues in apoptotic cells trigger rapid phagocytosis by macrophage scavenger receptor pathways. Mimicking apoptosis with liposomes containing PS may represent an attractive approach for molecular imaging of atherosclerosis. We investigated the utility of paramagnetic gadolinium liposomes enriched with PS (Gd-PS) in imaging atherosclerotic plaque. Gd-PS-containing Gd-conjugated lipids, fluorescent rhodamine, and PS were prepared and characterized. Cellular uptake in RAW macrophages (fluorescent uptake of rhodamine) was studied on a fluorescence plate reader, while Gd-PS-induced alteration in T1 relaxivity was evaluated using a 1.5 T MRI scanner. RAW cells demonstrate PS-dependent uptake of across a range of concentrations (2, 6, 12, and 20%) in comparison to control liposomes with no PS (0%). In vivo performance of Gd-PS was evaluated in the ApoE(-/-) mouse model by collection of serial T1 weighted gradient echo MR images using an 11.7 T MRI system and revealed rapid and significant enhancement of the aortic wall that was seen for at least 4 h after injection. Gd-PS-enriched liposomes enhance atherosclerotic plaque and colocalize with macrophages in experimental atherosclerosis.

Unilateral NMR applied to the conservation of works of art

In conventional NMR, samples from works of art in sizes above those considered acceptable in the field of art conservation would have to be removed to place them into the bore of large superconducting magnets. The portable permanent-magnet-based systems, by contrast, can be used in situ to study works of art, in a noninvasive manner. One of these portable NMR systems, NMR-MOUSE(R), measures the information contained in one pixel in an NMR image from a region of about 1 cm(2), which can be as thin as 2-3 microm. With such a high depth resolution, profiles through the structures of art objects can be measured to characterize the materials, the artists' techniques, and the deterioration processes. A novel application of the technique to study a deterioration process and to follow up a conservation treatment is presented in which micrometer-thick oil stains on paper are differentiated and characterized. In this example, the spin-spin relaxation T (2) of the stain is correlated to the iodine number and to the degree of cross-linking of the oil, parameters that are crucial in choosing an appropriate conservation treatment to remove them. It is also shown that the variation of T (2) over the course of treatments with organic solvents can be used to monitor the progress of the conservation interventions. It is expected that unilateral NMR in combination with multivariate data analysis will fill a gap within the set of high-spatial-resolution techniques currently available for the noninvasive analysis of materials in works of art, where procedures to study the inorganic components are currently far more developed than those suitable for the study of the organic components.

Quantum data bus in dipolar coupled nuclear spin qubits

We implement an iterative quantum state transfer exploiting the natural dipolar couplings in a spin chain of a liquid-crystal NMR system. During each iteration, a finite part of the amplitude of the state is transferred and, by applying an external operation on only the last two spins, the transferred state is made to accumulate on the spin at the end point. The transfer fidelity reaches one asymptotically through increasing the number of iterations. We also implement the inverted version of the scheme which can transfer an arbitrary state from the end point to any other position of the chain and entangle any pair of spins in the chain, acting as a full quantum data bus.

Solution Structure of Factor I-like Modules from Complement C7 Reveals a Pair of Follistatin Domains in Compact Pseudosymmetric Arrangement

Factor I-like modules (FIMs) of complement proteins C6, C7, and factor I participate in protein-protein interactions critical to the progress of a complement-mediated immune response to infections and other trauma. For instance, the carboxyl-terminal FIM pair of C7 (C7-FIMs) binds to the C345C domain of C5 and its activated product, C5b, during self-assembly of the cytolytic membrane-attack complex. FIMs share sequence similarity with follistatin domains (FDs) of known three-dimensional structure, suggesting that FIM structures could be reliably modeled. However, conflicting disulfide maps, inconsistent orientations of subdomains within FDs, and the presence of binding partners in all FD structures led us to determine the three-dimensional structure of C7-FIMs by NMR spectroscopy. The solution structure reveals that each FIM within C7 contains a small amino-terminal FOLN subdomain connected to a larger carboxyl-terminal KAZAL domain. The open arrangement of the subdomains within FIMs resembles that of first FDs within structures of tandem FDs but differs from the more compact subdomain arrangement of second or third FDs. Unexpectedly, the two C7-FIMs pack closely together with an approximate 2-fold rotational symmetry that is rarely seen in module pairs and has not been observed in FD-containing proteins. Interfaces between subdomains and between modules include numerous hydrophobic and electrostatic contributions, suggesting that this is a physiologically relevant conformation that persists in the context of the parent protein. Similar interfaces were predicted in a homology-based model of the C6-FIM pair. The C7-FIM structures also facilitated construction of a model of the single FIM of factor I.