Friday, July 21, 2017

Dynamic nuclear polarization-magnetic resonance imaging at low ESR irradiation frequency for ascorbyl free radicals

Ito, S. and F. Hyodo, Dynamic nuclear polarization-magnetic resonance imaging at low ESR irradiation frequency for ascorbyl free radicals. Scientific Reports, 2016. 6: p. 21407.


Highly water-soluble ubiquinone-0 (CoQ0) reacts with ascorbate monoanion (Asc) to mediate the production of ascorbyl free radicals (AFR). Using aqueous reaction mixture of CoQ0 and Asc, we obtained positively enhanced dynamic nuclear polarization (DNP)-magnetic resonance (MR) images of the AFR at low frequency (ranging from 515 to 530 MHz) of electron spin resonance (ESR) irradiation. The shape of the determined DNP spectrum was similar to ESR absorption spectra with doublet spectral peaks. The relative locational relationship of spectral peaks in the DNP spectra between the AFR (520 and 525 MHz), 14N-labeled carbamoyl-PROXYL (14N-CmP) (526.5 MHz), and Oxo63 (522 MHz) was different from that in the X-band ESR spectra, but were similar to that in the 300-MHz ESR spectra. The ratio of DNP enhancement to radical concentration for the AFR was higher than those for 14N-CmP, Oxo63, and flavin semiquinone radicals. The spectroscopic DNP properties observed for the AFR were essentially the same as those for AFR mediated by pyrroloquinoline quinone. Moreover, we made a success of in vivo DNP-MR imaging of the CoQ0-mediated AFR which was administered by the subcutaneous and oral injections as an imaging probe.

Wednesday, July 19, 2017

Coherent evolution of parahydrogen induced polarisation using laser pump, NMR probe spectroscopy: Theoretical framework and experimental observation


Halse, M.E., et al., Coherent evolution of parahydrogen induced polarisation using laser pump, NMR probe spectroscopy: Theoretical framework and experimental observation. J Magn Reson, 2017. 278: p. 25-38.


We recently reported a pump-probe method that uses a single laser pulse to introduce parahydrogen (p-H2) into a metal dihydride complex and then follows the time-evolution of the p-H2-derived nuclear spin states by NMR. We present here a theoretical framework to describe the oscillatory behaviour of the resultant hyperpolarised NMR signals using a product operator formalism. We consider the cases where the p-H2-derived protons form part of an AX, AXY, AXYZ or AA'XX' spin system in the product molecule. We use this framework to predict the patterns for 2D pump-probe NMR spectra, where the indirect dimension represents the evolution during the pump-probe delay and the positions of the cross-peaks depend on the difference in chemical shift of the p-H2-derived protons and the difference in their couplings to other nuclei. The evolution of the NMR signals of the p-H2-derived protons, as well as the transfer of hyperpolarisation to other NMR-active nuclei in the product, is described. The theoretical framework is tested experimentally for a set of ruthenium dihydride complexes representing the different spin systems. Theoretical predictions and experimental results agree to within experimental error for all features of the hyperpolarised 1H and 31P pump-probe NMR spectra. Thus we establish the laser pump, NMR probe approach as a robust way to directly observe and quantitatively analyse the coherent evolution of p-H2-derived spin order over micro-to-millisecond timescales.

Tuesday, July 18, 2017

[NMR] Postdoc position on SSNMR at the University of Lille, France #DNPNMR


Please forward to potential candidates.

Project title: Development of high-field (DNP)-NMR methods to detect quadrupolar nuclei on catalytic surfaces

A two-year postdoc position in solid-state NMR spectroscopy of advanced materials is available at the University of Lille, Lille, France. It will start preferably in December 2017.

Project description: The development of improved heterogeneous catalysts can be undertaken in a rational way by a better
understanding of their structures. Solid-state NMR spectroscopy is very well suited to the study of heterogeneous catalysts because it can give information on the local structure. However, the lack of sensitivity and resolution poses limit for the characterization of surface sites, notably when they are occupied by quadrupolar nuclei (11B, 17O, 27Al, 67Zn, 95Mo...) exhibiting NMR signal broaden by large quadrupolar interaction. This project aims at developing and applying novel solid-state high-field (DNP)NMR methods to probe the local environment of quadrupolar nuclei. It will provide unique insights into the structure of the catalytic surfaces, which will be useful to improve their performances.

Host and research infrastructure: Lille is a vibrant and handsome city, imbued with a rich history, located in the center of northwestern Europe (only 30 min by high-speed trains from Brussels, 1h from Paris and 1h30 from London). Lille is one of France’s top student cities and the university of Lille is a leading center for magnetic resonance. Lille NMR facility includes 800 and 900 MHz NMR spectrometers and has been selected to host the first 1.2 GHz NMR spectrometer to be installed in France. Our research group is internationally known for the development of solid-state NMR methods, notably for quadrupolar nuclei, and the characterization of heterogeneous catalysts. We have an expertise in high-field solid-state NMR spectroscopy and were among the pioneers of high-field DNP-NMR of hybrid and inorganic materials. 

The person: We seek application from candidates with experience in the development of solid-state NMR methods and/or the NMR characterization of inorganic materials and catalysts. The successful applicant will be given the opportunity to work in an exciting environment with national and international collaborations.

Contact: Applications and informal queries about the lab and research projects should be directed by

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Monday, July 17, 2017

Dynamic Polarization and Relaxation of 75As Nuclei in Silicon at High Magnetic Field and Low Temperature #DNPNMR


Järvinen, J., et al., Dynamic Polarization and Relaxation of 75As Nuclei in Silicon at High Magnetic Field and Low Temperature. Appl. Magn. Reson., 2017. 48(5): p. 473-483.


We present the results of experiments on dynamic nuclear polarization and relaxation of 75As in silicon crystals. Experiments are performed in strong magnetic fields of 4.6 T and temperatures below 1 K. At these conditions donor electron spins are fully polarized, and the allowed and forbidden electron spin resonance transitions are well resolved. We demonstrate effective nuclear polarization of 75As nuclei via the Overhauser effect on the time scale of several hundred seconds. Excitation of the forbidden transitions leads to a polarization through the solid effect. The relaxation rate of donor nuclei has strong temperature dependence characteristic of Orbach process.

Friday, July 14, 2017

Bis-Gadolinium Complexes for Solid Effect and Cross Effect Dynamic Nuclear Polarization #DNPNMR


Kaushik, M., et al., Bis-Gadolinium Complexes for Solid Effect and Cross Effect Dynamic Nuclear Polarization. Angew Chem Int Ed Engl, 2017. 56(15): p. 4295-4299.


High-spin complexes act as polarizing agents (PAs) for dynamic nuclear polarization (DNP) in solid-state NMR spectroscopy and feature promising aspects towards biomolecular DNP. We present a study on bis(Gd-chelate)s which enable cross effect (CE) DNP owing to spatial confinement of two dipolar-coupled electron spins. Their well-defined GdGd distances in the range of 1.2-3.4 nm allowed us to elucidate the GdGd distance dependence of the DNP mechanism and NMR signal enhancement. We found that GdGd distances above 2.1 nm result in solid effect DNP while distances between 1.2 and 2.1 nm enable CE for 1 H, 13 C, and 15 N nuclear spins. We compare 263 GHz electron paramagnetic resonance (EPR) spectra with the obtained DNP field profiles and discuss possible CE matching conditions within the high-spin system and the influence of dipolar broadening of the EPR signal. Our findings foster the understanding of the CE mechanism and the design of high-spin PAs for specific applications of DNP.

Wednesday, July 12, 2017

Solvent signal suppression for high-resolution MAS-DNP #DNPNMR


Lee, D., S.R. Chaudhari, and G. De Paepe, Solvent signal suppression for high-resolution MAS-DNP. J Magn Reson, 2017. 278: p. 60-66.


Dynamic nuclear polarization (DNP) has become a powerful tool to substantially increase the sensitivity of high-field magic angle spinning (MAS) solid-state NMR experiments. The addition of dissolved hyperpolarizing agents usually results in the presence of solvent signals that can overlap and obscure those of interest from the analyte. Here, two methods are proposed to suppress DNP solvent signals: a Forced Echo Dephasing experiment (FEDex) and TRAnsfer of Populations in DOuble Resonance Echo Dephasing (TRAPDORED) NMR. These methods reintroduce a heteronuclear dipolar interaction that is specific to the solvent, thereby forcing a dephasing of recoupled solvent spins and leaving acquired NMR spectra free of associated resonance overlap with the analyte. The potency of these methods is demonstrated on sample types common to MAS-DNP experiments, namely a frozen solution (of l-proline) and a powdered solid (progesterone), both containing deuterated glycerol as a DNP solvent. The proposed methods are efficient, simple to implement, compatible with other NMR experiments, and extendable past spectral editing for just DNP solvents. The sensitivity gains from MAS-DNP in conjunction with FEDex or TRAPDORED then permits rapid and uninterrupted sample analysis.

Monday, July 10, 2017

Dynamic Nuclear Polarization NMR as a new tool to investigate the nature of organic compounds occluded in plant silica particles #DNPNMR


Masion, A., et al., Dynamic Nuclear Polarization NMR as a new tool to investigate the nature of organic compounds occluded in plant silica particles. Sci Rep, 2017. 7(1): p. 3430.


The determination of the chemical nature of the organic matter associated with phytoliths remains a challenge. This difficulty mainly stems from amounts of organic carbon (C) that are often well below the detection limit of traditional spectroscopic tools. Conventional solid-state 13C Nuclear Magnetic Resonance (NMR) is widely used to examine the nature and structure of organic molecules, but its inherent low sensitivity prohibits the observation of diluted samples. The recent advent of commercial microwave source in the terahertz range triggered a renewed interest in the Dynamic Nuclear Polarization (DNP) technique to improve the signal to noise ratio of solid-state NMR experiments. With this technique, the 13C spectrum of a phytolith sample containing 0.1% w/w C was obtained overnight with sufficient quality to permit a semi-quantitative analysis of the organic matter, showing the presence of peptides and carbohydrates as predominant compounds. Considering the natural abundance of the 13C isotope, this experiment demonstrates that DNP NMR is sufficiently sensitive to observe spin systems present in amounts as low as a few tens of ppm.

Friday, July 7, 2017

Peptide and Protein Dynamics and Low-Temperature/DNP Magic Angle Spinning NMR #DNPNMR


Ni, Q.Z., et al., Peptide and Protein Dynamics and Low-Temperature/DNP Magic Angle Spinning NMR. J Phys Chem B, 2017. 121(19): p. 4997-5006.


In DNP MAS NMR experiments at approximately 80-110 K, the structurally important -13CH3 and -15NH3+ signals in MAS spectra of biological samples disappear due to the interference of the molecular motions with the 1H decoupling. Here we investigate the effect of these dynamic processes on the NMR line shapes and signal intensities in several typical systems: (1) microcrystalline APG, (2) membrane protein bR, (3) amyloid fibrils PI3-SH3, (4) monomeric alanine-CD3, and (5) the protonated and deuterated dipeptide N-Ac-VL over 78-300 K. In APG, the three-site hopping of the Ala-Cbeta peak disappears completely at 112 K, concomitant with the attenuation of CP signals from other 13C's and 15N's. Similarly, the 15N signal from Ala-NH3+ disappears at approximately 173 K, concurrent with the attenuation in CP experiments of other 15N's as well as 13C's. In bR and PI3-SH3, the methyl groups are attenuated at approximately 95 K, while all other 13C's remain unaffected. However, both systems exhibit substantial losses of intensity at approximately 243 K. Finally, with spectra of Ala and N-Ac-VL, we show that it is possible to extract site specific dynamic data from the temperature dependence of the intensity losses. Furthermore, 2H labeling can assist with recovering the spectral intensity. Thus, our study provides insight into the dynamic behavior of biological systems over a wide range of temperatures, and serves as a guide to optimizing the sensitivity and resolution of structural data in low temperature DNP MAS NMR spectra.

Wednesday, July 5, 2017

Surface Binding of TOTAPOL Assists Structural Investigations of Amyloid Fibrils by Dynamic Nuclear Polarization NMR Spectroscopy #DNPNMR


Nagaraj, M., et al., Surface Binding of TOTAPOL Assists Structural Investigations of Amyloid Fibrils by Dynamic Nuclear Polarization NMR Spectroscopy. Chembiochem, 2016. 17(14): p. 1308-11.


Dynamic nuclear polarization (DNP) NMR can enhance sensitivity but often comes at the price of a substantial loss of resolution. Two major factors affect spectral quality: low-temperature heterogeneous line broadening and paramagnetic relaxation enhancement (PRE) effects. Investigations by NMR spectroscopy, isothermal titration calorimetry (ITC), and EPR revealed a new substantial affinity of TOTAPOL to amyloid surfaces, very similar to that shown by the fluorescent dye thioflavin-T (ThT). As a consequence, DNP spectra with remarkably good resolution and still reasonable enhancement could be obtained at very low TOTAPOL concentrations, typically 400 times lower than commonly employed. These spectra yielded several long-range constraints that were difficult to obtain without DNP. Our findings open up new strategies for structural studies with DNP NMR spectroscopy on amyloids that can bind the biradical with affinity similar to that shown towards ThT.

[NMR] Solid-state NMR position in 
Karlsruhe, Germany

Voxalytic GmbH, the microcoil company, is expanding its young team, seeking applications from specialists in solid-state NMR. The successful applicant will qualify our NMR detector products for specific applications, formulate product needs, and maintain customer relations. Ideally, you will bring along a PhD in solid-state NMR, with knowledge of the state-of-the-art, and the willingness to travel. Applications should be sent via email (PDF please) to:



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Monday, July 3, 2017

Efficient assignment and NMR analysis of an intact virus using sequential side-chain correlations and DNP sensitization #DNPNMR


Sergeyev, I.V., et al., Efficient assignment and NMR analysis of an intact virus using sequential side-chain correlations and DNP sensitization. Proc Natl Acad Sci U S A, 2017. 114(20): p. 5171-5176.


An experimental strategy has been developed to increase the efficiency of dynamic nuclear polarization (DNP) in solid-state NMR studies. The method makes assignments simpler, faster, and more reliable via sequential correlations of both side-chain and Calpha resonances. The approach is particularly suited to complex biomolecules and systems with significant chemical-shift degeneracy. It was designed to overcome the spectral congestion and line broadening that occur due to sample freezing at the cryogenic temperatures required for DNP. Nonuniform sampling (NUS) is incorporated to achieve time-efficient collection of multidimensional data. Additionally, fast (25 kHz) magic-angle spinning (MAS) provides optimal sensitivity and resolution. Data collected in <1 wk produced a virtually complete de novo assignment of the coat protein of Pf1 virus. The peak positions and linewidths for samples near 100 K are perturbed relative to those near 273 K. These temperature-induced perturbations are strongly correlated with hydration surfaces.