Wednesday, April 29, 2015

Self-assembled trityl radical capsules--implications for dynamic nuclear polarization


Marin-Montesinos, I., et al., Self-assembled trityl radical capsules--implications for dynamic nuclear polarization. Phys Chem Chem Phys, 2015. 17(8): p. 5785-94.


A new class of guest-induced, bi-radical self-assembled organic capsules is reported. They are formed by the inclusion of a tetramethylammonium (TMA) cation between two monomers of the stable trityl radical OX63. OX63 is extensively used in dissolution dynamic nuclear polarization (DNP) where it leads to NMR sensitivity enhancements of several orders of magnitude. The supramolecular properties of OX63 have a strong impact on its DNP properties. An especially relevant case is the polarization of choline-containing metabolites, where complex formation between choline and OX63 results in faster relaxation.

Monday, April 27, 2015

Strategies for the hyperpolarization of acetonitrile and related ligands by SABRE


Mewis, R.E., et al., Strategies for the hyperpolarization of acetonitrile and related ligands by SABRE. J Phys Chem B, 2015. 119(4): p. 1416-24.


We report on a strategy for using SABRE (signal amplification by reversible exchange) for polarizing (1)H and (13)C nuclei of weakly interacting ligands which possess biologically relevant and nonaromatic motifs. We first demonstrate this via the polarization of acetonitrile, using Ir(IMes)(COD)Cl as the catalyst precursor, and confirm that the route to hyperpolarization transfer is via the J-coupling network. We extend this work to the polarization of propionitrile, benzylnitrile, benzonitrile, and trans-3-hexenedinitrile in order to assess its generality. In the (1)H NMR spectrum, the signal for acetonitrile is enhanced 8-fold over its thermal counterpart when [Ir(H)2(IMes)(MeCN)3](+) is the catalyst. Upon addition of pyridine or pyridine-d5, the active catalyst changes to [Ir(H)2(IMes)(py)2(MeCN)](+) and the resulting acetonitrile (1)H signal enhancement increases to 20- and 60-fold, respectively. In (13)C NMR studies, polarization transfers optimally to the quaternary (13)C nucleus of MeCN while the methyl (13)C is hardly polarized. Transfer to (13)C is shown to occur first via the (1)H-(1)H coupling between the hydrides and the methyl protons and then via either the (2)J or (1)J couplings to the respective (13)Cs, of which the (2)J route is more efficient. These experimental results are rationalized through a theoretical treatment which shows excellent agreement with experiment. In the case of MeCN, longitudinal two-spin orders between pairs of (1)H nuclei in the three-spin methyl group are created. Two-spin order states, between the (1)H and (13)C nuclei, are also created, and their existence is confirmed for Me(13)CN in both the (1)H and (13)C NMR spectra using the Only Parahydrogen Spectroscopy protocol.

Friday, April 24, 2015

Reminder: registration Hyperpolarized Magnetic Resonance meeting 2015

From the Ampere Magnetic Resonance List


Dear addressee,

With this e-mail we would like to remind you that the deadline for early bird registration for the
Hyperpolarized Magnetic Resonance meeting is approaching soon (April 30)!

This symposium combines the COST action EUROHyperPOL final meeting with the 5th international DNP symposium.

Where: Egmond aan Zee (the Netherlands)
When: Augustus 31 - September 4, 2015

Deadlines
Early bird registration 30/04/2015
Abstract submission
(to be considered for short talk) 30/04/2015
Abstract submission
(poster-presentations only) 30/06/2015



With kind regards,
The organizing committee

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Summer School on Nuclear Spin Hyperpolarisation Techniques - Final Call

From the Ampere Magnetic Resonance List



Dear Colleagues,

This is the final announcement for the next Summer School on Nuclear Spin Hyperpolarisation Techniques, organised within the EU-COST Framework (Action TD-1103), which is still open for registration until April 30th.

We do have a very limited number of spaces left for young researchers in the early stages of their carreer (PhDs, Postdocs) working in the fields of NMR, EPR, or MRI and seeking to embark deeper into the field of magnetic resonance and hyperpolarization in detail.

If interested, please register through the website: https://www.ocs.soton.ac.uk/index.php/cost/cost2015UK/index

The school will be held in an hotel within the beautiful Marwell Zoo and Wildlife Park nearby Southampton, UK. Social events include a Zoo Safari and a BBQ at the Zoo.

The main purpose of the school is to train the young generation of scientists (PhD's and PostDocs) working in the field of magnetic resonance in novel methodologies for nuclear spin hyperpolarisation. For this purpose the schoolwill discuss several hyperpolarisation techniques:

* Solid-State DNP
* dissolution-DNP
* Overhauser-DNP
* PHIP/SABRE (ParaHydrogen Induced Polarisation)
* CIDNP (Chemically induced DNP)
* QRIP (Quantum Rotor Induced Polarisation)

at 4 different levels: Theory, Simulations, Instrumentation and Applications.

The school is coordinated by Giuseppe Pileio (University of Southampton, UK) and Björn Corzilius (Goethe University Frankfurt, DE);

It boasts a rich list of top class teachers and scientists whose researches have contributed to estabilish the field of nuclear spin hyperpolarisation:

* Shimon Vega (Weizmann Institite, IL)
* Bob Griffin (MIT, Cambridge, US)
* Kevin Brindle (University of Cambridge, UK)
* Walter Kockenberger (University of Nottingham, UK)
* Ilya Kuprov (University of Southampton, UK)
* Jan-Henrik Arderkjaeren-Larsen (DTU Copenhagen, DK)
* Sami Jannin (EPFL, CH)
* Marina Bennati (MPI, Göttingen, DE)
* Marco Tessari (IMM, Nijmegen, NL)

N.B.: The school is open to PhD's, PostDocs and early career scientists but we can allow only a total number of 30 participants. Places will be assigned on a first come first served base so please do not wait the last minute to register! People from countries enrolled in the COST Action are entitled to a fixed reimbursement of 500€.

Students grants are provided by EU-COST Action TD-1103. The Zoo Safari and the BBQ have been generously offered by Bruker. Oxford Instruments and Cortecnet have generously offered drinks for all dinners.

Looking forward to seeing you at the School,
Giuseppe Pileio and Björn Corzilius

-- 
Dr. Björn Corzilius
Emmy Noether Research Group Leader
Institute for Physical and Theoretical Chemistry,
Institute for Biophysical Chemistry
and Center for Biomolecular Magnetic Resonance (BMRZ)
Goethe University Frankfurt
Campus Riedberg
Building N140, Room 14
Max-von-Laue-Str. 7
60438 Frankfurt am Main
phone: +49-(0)69-798-29467
fax: +49-(0)69-798-29404

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Tuesday, April 21, 2015

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 (http://www.cea.fr/english-portal) and delivered by the Grenoble-Alpes University (http://www.univ-grenoble-alpes.fr/en/). 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 gael.depaepe@cea.fr. 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
Laboratoire de Résonances Magnétiques
Service de Chimie Inorganique et Biologique
UMR_E 3 CEA-UJF
CEA Grenoble/INAC/SCIB/LRM
Commissariat à l'énergie Atomique
17, rue des Martyrs
Bâtiment 51C
Office P.132a / Lab P.138
38054 Grenoble

Cedex 9 - France
voice (office) +33 4 38 78 65 70
voice (lab) +33 4 38 78 47 26
fax +33 4 38 78 50 90

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Friday, April 17, 2015

Magic Angle Spinning NMR of Proteins: High-Frequency Dynamic Nuclear Polarization and H Detection


Su, Y., L. Andreas, and R.G. Griffin, Magic Angle Spinning NMR of Proteins: High-Frequency Dynamic Nuclear Polarization and H Detection. Annu Rev Biochem, 2015.


Magic angle spinning (MAS) NMR studies of amyloid and membrane proteins and large macromolecular complexes are an important new approach to structural biology. However, the applicability of these experiments, which are based on 13C- and 15N-detected spectra, would be enhanced if the sensitivity were improved. Here we discuss two advances that address this problem: high-frequency dynamic nuclear polarization (DNP) and 1H-detected MAS techniques. DNP is a sensitivity enhancement technique that transfers the high polarization of exogenous unpaired electrons to nuclear spins via microwave irradiation of electron-nuclear transitions. DNP boosts NMR signal intensities by factors of 102 to 103, thereby overcoming NMR's inherent low sensitivity. Alternatively, it permits structural investigations at the nanomolar scale. In addition, 1H detection is feasible primarily because of the development of MAS rotors that spin at frequencies of 40 to 60 kHz or higher and the preparation of extensively 2H-labeled proteins. Expected final online publication date for the Annual Review of Biochemistry Volume 84 is June 02, 2015. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.

Wednesday, April 15, 2015

Irreversible Catalyst Activation Enables Hyperpolarization and Water Solubility for NMR Signal Amplification by Reversible Exchange


Truong, M.L., et al., Irreversible Catalyst Activation Enables Hyperpolarization and Water Solubility for NMR Signal Amplification by Reversible Exchange. The Journal of Physical Chemistry B, 2014. 118(48): p. 13882-13889.


Activation of a catalyst [IrCl(COD)(IMes)] (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene; COD = cyclooctadiene)] for signal amplification by reversible exchange (SABRE) was monitored by in situ hyperpolarized proton NMR at 9.4 T. During the catalyst-activation process, the COD moiety undergoes hydrogenation that leads to its complete removal from the Ir complex. A transient hydride intermediate of the catalyst is observed via its hyperpolarized signatures, which could not be detected using conventional nonhyperpolarized solution NMR. SABRE enhancement of the pyridine substrate can be fully rendered only after removal of the COD moiety; failure to properly activate the catalyst in the presence of sufficient substrate can lead to irreversible deactivation consistent with oligomerization of the catalyst molecules. Following catalyst activation, results from selective RF-saturation studies support the hypothesis that substrate polarization at high field arises from nuclear cross-relaxation with hyperpolarized 1H spins of the hydride/orthohydrogen spin bath. Importantly, the chemical changes that accompanied the catalyst?s full activation were also found to endow the catalyst with water solubility, here used to demonstrate SABRE hyperpolarization of nicotinamide in water without the need for any organic cosolvent?paving the way to various biomedical applications of SABRE hyperpolarization methods.

Monday, April 13, 2015

Parahydrogen discriminated PHIP at low magnetic fields


Prina, I., L. Buljubasich, and R.H. Acosta, Parahydrogen discriminated PHIP at low magnetic fields. J. Magn. Reson., 2015. 251(0): p. 1-7.


Parahydrogen induced polarization (PHIP) is a powerful hyperpolarization technique. However, as the signal created has an anti-phase characteristic, it is subject to signal cancellation when the experiment is carried out in inhomogeneous magnetic fields or in low fields that lack the necessary spectral resolution. The use of benchtop spectrometers and time domain (TD) analyzers has continuously grown in the last years and many applications are found in the food industry, for non-invasive compound detection or as a test bench for new contrast agents among others. In this type of NMR devices the combination of low and inhomogeneous magnetic fields renders the application of PHIP quite challenging. We have recently shown that the acquisition of J-spectra in high magnetic fields not only removes the anti-phase peak cancellation but also produces a separation of thermal from hyperpolarized signals, providing Parahydrogen Discriminated (PhD-PHIP) spectra. In this work we extend the use of PhD-PHIP to low and inhomogeneous fields. In this case the strong coupling found for the protons of the sample renders spin-echo spectra that have a great complexity, however, a central region in the spectrum with only hyperpolarized signal is clearly identified. This experimental approach is ideal for monitoring real time chemical reaction of pure PHIP signals.

Friday, April 10, 2015

The electron depolarization during dynamic nuclear polarization: measurements and simulations


Hovav, Y., et al., The electron depolarization during dynamic nuclear polarization: measurements and simulations. Phys Chem Chem Phys, 2015. 17(1): p. 226-44.


Dynamic nuclear polarization is typically explained either using microscopic systems, such as in the solid effect and cross effect mechanisms, or using the macroscopic formalism of spin temperature which assumes that the state of the electrons can be described using temperature coefficients, giving rise to the thermal mixing mechanism. The distinction between these mechanisms is typically made by measuring the DNP spectrum - i.e. the nuclear enhancement profile as a function of irradiation frequency. In particular, we have previously used the solid effect and cross effect mechanisms to explain temperature dependent DNP spectra. Our past analysis has however neglected the effect of depolarization of the electrons resulting from the microwave (MW) irradiation. In this work we concentrate on this electron depolarization process and perform electron-electron double resonance (ELDOR) experiments on TEMPOL and trityl frozen solutions, using a 3.34 Tesla magnet and at 2.7-30 K, in order to measure the state of the electron polarization during DNP. The experiments indicate that a significant part of the EPR line is affected by the irradiation due to spectral diffusion. Using a theoretical framework based on rate equations for the polarizations of the different electron spin packets and for those of the nuclei we simulated the various ELDOR line-shapes and reproduced the MW frequency and irradiation time dependence. The obtained electron polarization distribution cannot be described using temperature coefficients as required by the classical thermal mixing mechanism, and therefore the DNP mechanism cannot be described by thermal mixing. Instead, the theoretical framework presented here for the analysis of the ELDOR data forms a basis for future interpretation of DNP spectra in combination with EPR measurements.

Wednesday, April 8, 2015

Dynamic nuclear polarization of a glassy matrix prepared by solid state mechanochemical amorphization of crystalline substances


Elisei, E., et al., Dynamic nuclear polarization of a glassy matrix prepared by solid state mechanochemical amorphization of crystalline substances. Chem Commun (Camb), 2015. 51(11): p. 2080-3.


A mechanochemical "solvent-free" route is presented for the preparation of solid samples ready to be employed in the Dynamic Nuclear Polarization (DNP). (1)H-DNP build-up curves at 3.46 T as a function of temperature and radical concentration show steady state nuclear polarization of 10% (0.5% TEMPO concentration at 1.75 K).

Monday, April 6, 2015

Fast-field-cycling relaxometry enhanced by Dynamic Nuclear Polarization


Neudert, O., et al., Fast-field-cycling relaxometry enhanced by Dynamic Nuclear Polarization. Microporous and Mesoporous Materials, 2015. 205(0): p. 70-74.


Fast-field-cycling (FFC) NMR relaxometry experiments enhanced by in-situ Dynamic Nuclear Polarization (DNP) were performed for 1H and 13C nuclear spins with a setup based on a commercial electronically switching FFC relaxometer and a recently-built Alderman–Grant type microwave resonator for 2 GHz. DNP-enhanced 1H relaxation dispersion profiles were compared to reference measurements and literature data in order to prove the reliability of DNP-enhanced relaxometry data. The method was then used to investigate the paramagnetic nuclear spin relaxation of 13C in a benzene-13C6,D6 solution of nitroxide radicals. Dispersion profiles of good quality were obtained within 2 h of measurement time from a comparatively small sample of 60 μl. As a prospect for future applications, DNP experiments with a high-molecular weight Poly(butadiene-1,4) melt and BDPA radical were carried out at 2 GHz and 9.7 GHz microwave frequency, showing solid effect DNP enhancements. In-situ hyperpolarization by DNP may provide extended possibilities for FFC relaxometry, e.g. by allowing enhanced detection of dilute or insensitive nuclear spins, additional selectivity or faster measurements of small samples.

Friday, April 3, 2015

Mechanisms of dynamic nuclear polarization in insulating solids


Can, T.V., Q.Z. Ni, and R.G. Griffin, Mechanisms of dynamic nuclear polarization in insulating solids. J Magn Reson, 2015. 253(0): p. 23-35.


Dynamic nuclear polarization (DNP) is a technique used to enhance signal intensities in NMR experiments by transferring the high polarization of electrons to their surrounding nuclei. The past decade has witnessed a renaissance in the development of DNP, especially at high magnetic fields, and its application in several areas including biophysics, chemistry, structural biology and materials science. Recent technical and theoretical advances have expanded our understanding of established experiments: for example, the cross effect DNP in samples spinning at the magic angle. Furthermore, new experiments suggest that our understanding of the Overhauser effect and its applicability to insulating solids needs to be re-examined. In this article, we summarize important results of the past few years and provide quantum mechanical explanations underlying these results. We also discuss future directions of DNP and current limitations, including the problem of resolution in protein spectra recorded at 80-100K.

Wednesday, April 1, 2015

Quantum mechanical aspects of dynamical neutron polarization


I came across this article about DNP, apparently the acronym is not just used as in DNP-NMR but also for Dynamic Neutron Polarization, Dinitrophenol, Doctor of Nursing Practice etc. ...



Betz, T., G. Badurek, and E. Jericha, Quantum mechanical aspects of dynamical neutron polarization. Physica B: Condensed Matter, 2007. 397(1-2): p. 195-197.


Dynamic Neutron Polarization (DNP) is a concept which allows to achieve complete polarization of slow neutrons, virtually without any loss of intensity. There the neutrons pass through a combination of a static and a rotating magnetic field in resonance, like in a standard NMR apparatus. Depending on their initial spin state, they end up with different kinetic energies and therefore different velocity. In a succeeding magnetic precession field this distinction causes a different total precession angle. Tuning the field strength can lead to a final state where two original anti-parallel spin states are aligned parallel and hence to polarization. The goal of this work is to describe the quantum mechanical aspects of DNP and to work out the differences to the semi-classical treatment. We show by quantum mechanical means, that the concept works and DNP is feasible, indeed. Therefore, we have to take a closer look to the behavior of neutron wave functions in magnetic fields. In the first Section we consider a monochromatic continuous beam. The more realistic case of a pulsed, polychromatic beam requires a time-dependent field configuration and will be treated in the second Section. In particular the spatial separation of the spin up- and down-states is considered, because it causes an effect of polarization damping so that one cannot achieve a fully polarized final state. This effect is not predicted by the semi-classical treatment of DNP. However, this reduction of polarization is very small and can be neglected in realistic DNP-setups.