Category Archives: Helium Spinning

Cryogenic Platforms and Optimized DNP Sensitivity #DNPNMR

Matsuki, Yoh, and Toshimichi Fujiwara. “Cryogenic Platforms and Optimized DNP Sensitivity,” 7:16, 2018.

Modern high-field DNP NMR spectrometers are typically based on a cryogenic magic-angle sample spinning (MAS) capability. Conventionally, sample temperatures of T ∼100 K have been widely used, enabling substantial NMR signal enhancement with DNP at high external field conditions such as B0 =9.4 T. Today, however, the need for performing MAS DNP at much lower temperatures (T ≪100 K) is receiving growing attention for its ability to recover the rapidly degrading efficiency of the cross-effect (CE)-based DNP at even higher magnetic fields, B0 >10 T. In this article, we describe three contemporary cryogenic DNP MAS NMR probe systems: one is N2 based for T ∼100 K, and the other two are helium based for T ≪100 K. Principal requirements important in designing the cryogenic MAS NMR systems include long-term stability, cost efficiency, and readiness of operation. All the described setups incorporated various modifications and novel features to meet these challenges. In particular, the novel closed-cycle helium MAS system realizes all the requirements to a high standard, establishing an efficient and practical platform for ultralow sample temperature (T ∼30 K) MAS DNP. The resulting dramatic increase in sensitivity gain suggests the regained promise for the CE-based DNP at very high-field conditions (B0 >10 T). The experimental DNP data and effective sensitivity gain obtained with the described systems operating at 14.1 and 16.4 T are also discussed.

Ultra-low temperature MAS-DNP #DNPNMR

Lee, D., et al., Ultra-low temperature MAS-DNP. J. Magn. Reson., 2016. 264: p. 116-124.

Since the infancy of NMR spectroscopy, sensitivity and resolution have been the limiting factors of the technique. Regular essential developments on this front have led to the widely applicable, versatile, and powerful spectroscopy that we know today. However, the Holy Grail of ultimate sensitivity and resolution is not yet reached, and technical improvements are still ongoing. Hence, high-field dynamic nuclear polarization (DNP) making use of high-frequency, high-power microwave irradiation of electron spins has become very promising in combination with magic angle sample spinning (MAS) solid-state NMR experiments. This is because it leads to a transfer of the much larger polarization of these electron spins under suitable irradiation to surrounding nuclei, greatly increasing NMR sensitivity. Currently, this boom in MAS-DNP is mainly performed at minimum sample temperatures of about 100 K, using cold nitrogen gas to pneumatically spin and cool the sample. This Perspective deals with the desire to improve further the sensitivity and resolution by providing “ultra”-low temperatures for MAS-DNP, using cryogenic helium gas. Different designs on how this technological challenge has been overcome are described. It is shown that stable and fast spinning can be attained for sample temperatures down to 30 K using a large cryostat developed in our laboratory. Using this cryostat to cool a closed-loop of helium gas brings the additional advantage of sample spinning frequencies that can greatly surpass those achievable with nitrogen gas, due to the differing fluidic properties of these two gases. It is shown that using ultra-low temperatures for MAS-DNP results in substantial experimental sensitivity enhancements and according time-savings. Access to this temperature range is demonstrated to be both viable and highly pertinent.

Closed-cycle cold helium magic-angle spinning for sensitivity-enhanced multi-dimensional solid-state NMR

Matsuki, Y., et al., Closed-cycle cold helium magic-angle spinning for sensitivity-enhanced multi-dimensional solid-state NMR. J Magn Reson, 2015. 259: p. 76-81.

Magic-angle spinning (MAS) NMR is a powerful tool for studying molecular structure and dynamics, but suffers from its low sensitivity. Here, we developed a novel helium-cooling MAS NMR probe system adopting a closed-loop gas recirculation mechanism. In addition to the sensitivity gain due to low temperature, the present system has enabled highly stable MAS (vR=4-12 kHz) at cryogenic temperatures (T=35-120 K) for over a week without consuming helium at a cost for electricity of 16 kW/h. High-resolution 1D and 2D data were recorded for a crystalline tri-peptide sample at T=40 K and B0=16.4 T, where an order of magnitude of sensitivity gain was demonstrated versus room temperature measurement. The low-cost and long-term stable MAS strongly promotes broader application of the brute-force sensitivity-enhanced multi-dimensional MAS NMR, as well as dynamic nuclear polarization (DNP)-enhanced NMR in a temperature range lower than 100 K.

Pushing NMR sensitivity limits using dynamic nuclear polarization with closed-loop cryogenic helium sample spinning

Bouleau, E., et al., Pushing NMR sensitivity limits using dynamic nuclear polarization with closed-loop cryogenic helium sample spinning. Chemical Science, 2015.

We report a strategy to push the limits of solid-state NMR sensitivity far beyond its current state-of-the-art. The approach relies on the use of dynamic nuclear polarization and demonstrates unprecedented DNP enhancement factors for experiments performed at sample temperatures much lower than 100 K, and can translate into 6 orders of magnitude of experimental time-savings. This leap-forward was made possible thanks to the employment of cryogenic helium as the gas to power magic angle sample spinning (MAS) for dynamic nuclear polarization (DNP) enhanced NMR experiments. These experimental conditions far exceed what is currently possible and allows currently reaching sample temperatures down to 30 K while conducting experiments with improved resolution (thanks to faster spinning frequencies, up to 25 kHz) and highly polarized nuclear spins. The impressive associated gains were used to hyperpolarize the surface of an industrial catalyst as well as to hyperpolarize organic nano-assemblies (self-assembling peptides in our case), for whom structures cannot be solved using diffraction techniques. Sustainable cryogenic helium sample spinning significantly enlarges the realm and possibilities of the MAS-DNP technique and is the route to transform NMR into a versatile but also sensitive atomic-level characterization tool.

PhD in helium spinning MAS-DNP at CEA Grenoble (France)

From the Ampere Magnetic Resonance List

PhD in helium spinning MAS-DNP at CEA Grenoble (France)

Ideal start date: Sept. to Nov. 2015 – Duration: Three years

Applications for a PhD fellowship in physical chemistry are now welcomed at the INAC Institute (CEA / Univ. Grenoble Alpes) Grenoble, France. The PhD will focus on the development of an emerging technique called MAS-DNP (Magic Angle spinning Dynamic Nuclear Polarization). This hyperpolarization technique allows recording solid-state NMR (Nuclear Magnetic Resonance) data that can be used to extract complex atomic-level structural information, such as surface functionalization and inter-nuclear distances.

This technique has recently proven particularly useful when applied to systems that cannot be probed effectively using X-ray crystallography or solution-state NMR. Thanks to huge sensitivity gains (several orders of magnitude!) one can now start studying very challenging problems (for systems such as porous materials, nano-self-assemblies, and functionalized nanoparticles), which were so far lacking efficient atomic-scale characterization techniques. Recent publications from the group can be found below.

Although the combination of DNP and solid-state NMR is showing much promise, there are a lot of improvements that can still be made. To this end, our lab has engaged to go beyond state-of-the-art and is currently developing a system that permits sustainable MAS at temperatures well below 100 K. A working prototype (that uses cryogenic helium spinning) is currently under testing in our laboratory. Notably, world-unique results of MAS rates of up to 25 kHz and sample temperatures down to 20 K have recently been achieved.

This PhD work is part of a larger project involving a strong partnership between two academic laboratories (INAC/CEA for MAS-DNP and LNCMI/CNRS for high-field EPR) and an industrial partner (Bruker Biospin). The work will be located in a dynamical environment at the MINATEC campus (CEA Grenoble) within the SCIB laboratory (INAC) where the DNP group is located. The group is currently working with the first high-field MAS-DNP system installed in France (since September 2011) as well as with conventional solid-state MAS NMR.

Grenoble is one of the major cities in Europe for research with a large international scientific community. The PhD will take place within the CEA campus ( and delivered by the Grenoble-Alpes University ( In addition, Grenoble is a very pleasant city to live, with direct connections to the nearby French Alps.

Motivated candidates must have a good command (written / spoken) of English and should send a detailed CV and a letter of motivation to Recommendation letters can also be joined and will be highly appreciated.

1 – Enhanced Solid-State NMR Correlation Spectroscopy of Quadrupolar Nuclei Using Dynamic Nuclear Polarization, Lee D., Takahashi H., Thankamony A. S. L., Dacquin J.-P., Bardet M., Lafon O., De Paëpe G., Journal of the American Chemical Society, 134, 45, 18491-18494, 2012

2 – Rapid Natural-Abundance 2D C13-C13 Correlation Spectroscopy Using Dynamic Nuclear Polarization Enhanced Solid-State NMR and Matrix-Free Sample Preparation, Takahashi H., Lee D., Dubois L., Bardet M., Hediger S. De Paëpe G., Angewandte Chemie Internatinal Edition, 51, 47, 11766-11769, 2012

3 – Towards Structure Determination of Self-Assembled Peptides by Dynamic Nuclear Polarization Enhanced Solid-State NMR, Takahashi H., Viverge B., Lee D., Rannou P., De Paëpe G., Angewandte Chemie Internatinal Edition, 52, 27, 6979-6982, 2013 (VIP Article)

4– Solid-State NMR on Bacterial Cells: Selective Cell-Wall-Signal Enhancement and Resolution Improvement using Dynamic Nuclear Polarization, Takahashi H., Ayala I., Bardet M., De Paëpe G., Simorre J.P., Hediger S., Journal of the American Chemical Society, 135 (13), 5105-5110, 2013 (Cover Article)

5 — Untangling the Condensation Network of Organosiloxanes on Nanoparticles using 2D 29Si- 29Si Solid-State NMR enhanced by Dynamic Nuclear Polarization, D Lee, G Monin, NT Duong, IZ Lopez, M Bardet, V Mareau, L Gonon, G. De Paëpe, Journal of the American Chemical Society, 136 (39), 13781-13788, 2014 (Cover article)


Dr Gaël De Paëpe

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