Monday, December 24, 2012

Solid state nuclear magnetic resonance with magic-angle spinning and dynamic nuclear polarization below 25K

Thurber, K.R., et al., Solid state nuclear magnetic resonance with magic-angle spinning and dynamic nuclear polarization below 25K. J. Magn. Reson., 2013. 226(0): p. 100-106.

We describe an apparatus for solid state nuclear magnetic resonance (NMR) with dynamic nuclear polarization (DNP) and magic-angle spinning (MAS) at 20-25K and 9.4Tesla. The MAS NMR probe uses helium to cool the sample space and nitrogen gas for MAS drive and bearings, as described earlier [1], but also includes a corrugated waveguide for transmission of microwaves from below the probe to the sample. With a 30mW circularly polarized microwave source at 264GHz, MAS at 6.8kHz, and 21K sample temperature, greater than 25-fold enhancements of cross-polarized (13)C NMR signals are observed in spectra of frozen glycerol/water solutions containing the triradical dopant DOTOPA-TEMPO when microwaves are applied. As demonstrations, we present DNP-enhanced one-dimensional and two-dimensional (13)C MAS NMR spectra of frozen solutions of uniformly (13)C-labeled l-alanine and melittin, a 26-residue helical peptide that we have synthesized with four uniformly (13)C-labeled amino acids.

Happy Holidays and a Happy New Year

Happy Holidays and a Happy New Year to all the DNP-NMR blog readers. I will be taking a short break but will be back in the second week of January with new updates and DNP literature.

Happy Holidays or Fröhliche Weihnachten as we say in Germany.

Friday, December 21, 2012

Frequency dependence of electron spin relaxation times in aqueous solution for a nitronyl nitroxide radical and perdeuterated-tempone between 250MHz and 34GHz

Biller, J.R., et al., Frequency dependence of electron spin relaxation times in aqueous solution for a nitronyl nitroxide radical and perdeuterated-tempone between 250MHz and 34GHz. J. Magn. Reson., 2012. 225(0): p. 52-57.


Electron spin relaxation times of perdeuterated tempone (PDT) 1 and of a nitronyl nitroxide (2-(4-carboxy-phenyl)-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl) 2 in aqueous solution at room temperature were measured by 2-pulse electron spin echo (T(2)) or 3-pulse inversion recovery (T(1)) in the frequency range of 250MHz to 34GHz. At 9GHz values of T(1) measured by long-pulse saturation recovery were in good agreement with values determined by inversion recovery. Below 9GHz for 1 and below 1.5GHz for 2,T(1) approximately T(2), as expected in the fast tumbling regime. At higher frequencies T(2) was shorter than T(1) due to incomplete motional averaging of g and A anisotropy. The frequency dependence of 1/T(1) is modeled as the sum of spin rotation, modulation of g and A-anisotropy, and a thermally-activated process that has maximum contribution at about 1.5GHz. The spin lattice relaxation times for the nitronyl nitroxide were longer than for PDT by a factor of about 2 at 34GHz, decreasing to about a factor of 1.5 at 250MHz. The rotational correlation times, tau(R) are calculated to be 9ps for 1 and about 25ps for 2. The longer spin lattice relaxation times for 2 than for 1 at 9 and 34GHz are due predominantly to smaller contributions from spin rotation that arise from slower tumbling. The smaller nitrogen hyperfine couplings for the nitronyl 2 than for 1 decrease the contribution to relaxation due to modulation of A anisotropy. However, at lower frequencies the slower tumbling of 2 results in a larger value of omegatau(R) (omega is the resonance frequency) and larger values of the spectral density function, which enhances the contribution from modulation of anisotropic interactions for 2 to a greater extent than for 1.



Wednesday, December 19, 2012

On the spin order transfer from parahydrogen to another nucleus

Bär, S., et al., On the spin order transfer from parahydrogen to another nucleus. J. Magn. Reson., 2012. 225(0): p. 25-35.


The hyperpolarization of nuclear spins holds great potential e.g. for biomedical research. Strong signal enhancements have been demonstrated e.g. by transforming the spin order of parahydrogen (pH(2)) to net polarization of a third nucleus (e.g. (13)C) by means of a spin-order-transfer (SOT) sequence. The polarization achieved is vitally dependent on the sequence intervals, which are a function of the J-coupling constants of the molecule to be polarized. How to derive the SOT sequence intervals, the actual values for molecules as well as the (theoretical) polarization yield and robustness, however, are not fully described. In this paper, (a) we provide the methods to obtain the SOT intervals for a given set of J-coupling constants (i.e. of a new hyperpolarization agent); (b) exemplify these methods on molecules from literature, providing the hitherto missing intervals and simulated polarization yield; and (c) assess the robustness of the sequences towards B(1) and J-coupling errors. Close to unity polarization is obtained for all molecules and sequences. Furthermore, the loss of polarization caused by erroneous B(1) and J-coupling constants is reduced by choosing the channel and phase of some pulses in the SOT sequences appropriately.



Monday, December 17, 2012

Indirect and Direct 29Si Dynamic Nuclear Polarization of Dispersed Nanoparticles

Lafon, O., et al., Indirect and Direct 29Si Dynamic Nuclear Polarization of Dispersed Nanoparticles. Chemical Communications, 2012.


We show how the 29Si NMR signals of dispersed inorganic nanoparticles of laponite[registered sign] can be enhanced by Dynamic Nuclear Polarization (DNP). The direct DNP enhances the signals of 29Si nuclei near to unpaired electrons, whereas the indirect DNP via 1H enhances the signals of more remote sites.



Friday, December 14, 2012

Theoretical aspects of dynamic nuclear polarization in the solid state - spin temperature and thermal mixing

Hovav, Y., A. Feintuch, and S. Vega, Theoretical aspects of dynamic nuclear polarization in the solid state - spin temperature and thermal mixing. Phys. Chem. Chem. Phys., 2013. 15(1): p. 188-203.

Dynamic nuclear polarization is a method which allows for a dramatic increase of the NMR signals due to polarization transfer between electrons and their neighboring nuclei, via microwave irradiation. These experiments have become popular in recent years due to the ability to create hyper-polarized chemically and biologically relevant molecules, in frozen glass forming mixtures containing free radicals. Three mechanisms have been proposed for the polarization transfer between electrons and their surrounding nuclei in such non-conducting samples: the solid effect and cross effect mechanisms, which are based on quantum mechanics and relaxation on small spin systems, and thermal mixing, which originates from the thermodynamic macroscopic notion of spin temperature. We have recently introduced a spin model, which is based on the density matrix formalism and includes relaxation, and applied it to study the solid effect and cross effect mechanisms on small spin systems. In this publication we use the same model to describe the thermal mixing mechanism, and the creation of spin temperature. This is obtained without relying on the spin temperature formalism. Simulations of small model systems are used on systems with homogeneously and inhomogeneously broadened EPR lines. For the case of a homogeneously broadened line we show that the nuclear enhancement results from the thermal mixing and solid effect mechanisms, and that spin temperatures are created in the system. In the inhomogeneous case the enhancements are attributed to the solid effect and cross effect mechanisms, but not thermal mixing.



Wednesday, December 12, 2012

Combustion resistance of the 129Xe hyperpolarized nuclear spin state

Stupic, K.F., et al., Combustion resistance of the 129Xe hyperpolarized nuclear spin state. Phys. Chem. Chem. Phys., 2013. 15(1): p. 94-97.

Using a methane-xenon mixture for spin exchange optical pumping, MRI of combustion was enabled. The 129Xe hyperpolarized nuclear spin state was found to sufficiently survive the complete passage through the harsh environment of the reaction zone. A velocity profile (Vz(z)) of a flame was recorded to demonstrate the feasibility of MRI velocimetry of transport processes in combustors.



Monday, December 10, 2012

Sensitivity enhancement and low-field spin relaxation in singlet NMR

This article does not describe any DNP experiments. However, singlet states can be useful for dissolution DNP experiments.



Bocan, J., G. Pileio, and M.H. Levitt, Sensitivity enhancement and low-field spin relaxation in singlet NMR. Phys. Chem. Chem. Phys., 2012. 14(46): p. 16032-16040.


The singlet states of nuclear spin-1/2 pairs often display extended lifetimes that can be an order of magnitude longer than conventional relaxation times. We show that, in favourable circumstances, acquisition of the NMR signal during an extended multiple spin-echo train, followed by suitable data processing, enhances the signal-to-noise ratio of singlet NMR by up to an order of magnitude. The achievable enhancement depends on the transverse relaxation time constant, the magnetic field inhomogeneity, and the acceptable degradation in digital spectral resolution. We use the combination of singlet NMR and multiple spin-echo data acquisition to study the low-field nuclear relaxation processes of 15N-labelled nitrous oxide (15N2O) in solution. A general relaxation theory for coupled 2-spin-1/2 systems in low magnetic field is developed. Experimental trajectories of the nuclear spin observables are compared with theoretical expressions, including dipole-dipole and spin-rotation relaxation mechanisms. The estimated values of the spin-rotation tensors are compared with previous estimations from NMR and molecular beam electric resonance.



Friday, December 7, 2012

Development of DNP-Enhanced High-Resolution Solid-State NMR System for the Characterization of the Surface Structure of Polymer Materials

Horii, F., et al., Development of DNP-Enhanced High-Resolution Solid-State NMR System for the Characterization of the Surface Structure of Polymer Materials. J. Infrared Millim. Te., 2012. 33(7): p. 756-765.


A dynamic nuclear polarization (DNP)-enhanced cross-polarization/magic-angle spinning (DNP/CP/MAS) NMR system has been developed by combining a 200 MHz Chemagnetics CMX-200 spectrometer operating at 4.7 T with a high-power 131.5 GHz Gyrotron FU CW IV. The 30 W sub-THz wave generated in a long pulse TE $ _{{41}}^{{(1)}} $ mode with a frequency of 5 Hz was successfully transmitted to the modified Doty Scientific low-temperature CP/MAS probe through copper smooth-wall circular waveguides. Since serious RF noises on NMR signals by arcing in the electric circuit of the probe and undesired sample heating were induced by the continuous sub-THz wave pulse irradiation with higher powers, the on-off sub-THz wave pulse irradiation synchronized with the NMR detection was developed and the appropriate setting of the irradiation time and the cooling time corresponding to the non-irradiation time was found to be very effective for the suppression of the arcing and the sample heating. The attainable maximum DNP enhancement was more than 30 folds for C1 13 C-enriched D -glucose dissolved in the frozen medium containing mono-radical 4-amino-TEMPO. The first DNP/CP/MAS 13 C NMR spectra of poly(methyl methacrylate) (PMMA) sub-micron particles were obtained at the dispersed state in the same frozen medium, indicating that DNP-enhanced 1 H spins effectively diffuse from the medium to the PMMA particles through their surface and are detected as high-resolution 13 C spectra in the surficial region to which the 1 H spins reach. On the basis of these results, the possibility of the DNP/CP/MAS NMR characterization of the surface structure of nanomaterials including polymer materials was discussed.



Thursday, December 6, 2012

Postdoctoral researcher in Gyrotron DNP NMR

I think I posted that earlier, but this position is still available:


Postdoctoral researcher in Gyrotron DNP NMR

€Competitive | Switzerland | 03 Dec 2012
Dynamic Nuclear Polarization for NMR is a very strong and exciting area of research at EPFL, thanks to a campus-wide collaboration among scientists and with two companies.
Proficiency in experimental physics is required, preferably with knowledge in magnetic resonance or millimeter wave technology.
Funding of this position comes from EPFL, leaving full freedom in the choice of projects. Contract renewable up to 4 years.
Location: Lausanne, Switzerland
Salary min: CHF 75,000
Contact: jean-philippe.ansermet@epfl.ch
See: http://lpmn.epfl.ch

DNP-NMR is becoming more popular

So I don't know if you are paying attention to the pageview count that is displayed on the front page to the right. Well, I do, and not too boost my ego, but because I'm generally interested how the blog is doing and what topics are interesting for the readers.

If you follow that page counter you probably noticed that the page view count almost doubled from October to November. Now this number is a cumulative sum over the last 30 days but you can see the same behavior in the monthly counts (shown in the figure below).



I'm super excited about that trend. It shows that the interest in DNP-NMR increases. Why the sudden increase? Well, over the last few months I was able to get more inbound links to the blog that makes the blog more visible and that increased the page view count significantly.

Friday, November 30, 2012

HyperSPASM NMR: A new approach to single-shot 2D correlations on DNP-enhanced samples

Donovan, K.J. and L. Frydman, HyperSPASM NMR: A new approach to single-shot 2D correlations on DNP-enhanced samples. J. Magn. Reson., 2012. 225(0): p. 115-119.


Dissolution DNP experiments are limited to a single or at most a few scans, before the non-Boltzmann magnetization has been consumed. This makes it impractical to record 2D NMR data by conventional, t1-incremented schemes. Here a new approach termed HyperSPASM to establish 2D heteronuclear correlations in a single scan is reported, aimed at dealing with this kind of challenge. The HyperSPASM experiment relies on imposing an amplitude-modulation of the data by a single Δt1 indirect-domain evolution time, and subsequently monitoring the imparted encoding on separate echo and anti-echo pathway signals within a single continuous acquisition. This is implemented via the use of alternating, switching, coherence selection gradients. As a result of these manipulations the phase imparted by a heteronucleus over its indirect domain evolution can be accurately extracted, and 2D data unambiguously reconstructed with a single-shot excitation. The nature of this sequence makes the resulting experiment particularly well suited for collecting indirectly-detected HSQC data on hyperpolarized samples. The potential of the ensuing HyperSPASM method is exemplified with natural-abundance hyperpolarized correlations on model systems.

Wednesday, November 28, 2012

Low-temperature cross polarization in view of enhancing dissolution Dynamic Nuclear Polarization in NMR

Jannin, S., et al., Low-temperature cross polarization in view of enhancing dissolution Dynamic Nuclear Polarization in NMR. Chem. Phys. Lett., 2011. 517(4–6): p. 234-236.


Dynamic Nuclear Polarization (DNP) induced by saturation of ESR transitions of TEMPO at 1.2 K and 3.35 T is characterized by build-up rates that are typically 5 times faster for protons than for the carboxylic carbon-13 in acetate. We show that cross polarization from protons to carbon-13 allows one to achieve a polarization P(13C) >20% in less than 10 min, twice as much as has been previously reported, in one-fifth of the time. This should open the way to an unprecedented improvement in the efficiency of dissolution DNP.

Monday, November 26, 2012

High field dynamic nuclear polarization at 6.7T: Carbon-13 polarization above 70% within 20 min

Jannin, S., et al., High field dynamic nuclear polarization at 6.7&T: Carbon-13 polarization above 70% within 20 min. Chem. Phys. Lett., 2012. 549(0): p. 99-102.


In most applications of dissolution-DNP, the polarization of nuclei with low gyromagnetic ratios such as 13C is enhanced directly by irradiating the ESR transitions of radicals with narrow ESR lines such as Trityl at low temperatures T = 1.2 K in polarizing fields B0 ⩽ 5 T. In a field B0 = 6.7 T at T = 1.2 K, DNP with TEMPO leads to a rapid build-up of proton polarization P(1H) = 91% with τDNP(1H) = 150 s. CP at low temperatures yields a polarization P(1H → 13C) in excess of 70% within 20 min. After rapid dissolution to room temperature, this is 122 000 times larger than the Boltzmann polarization at 300 K and 6.7 T.



Friday, November 23, 2012

Dissolution dynamic nuclear polarization efficiency enhanced by Hartmann–Hahn cross polarization

Batel, M., et al., Dissolution dynamic nuclear polarization efficiency enhanced by Hartmann–Hahn cross polarization. Chem. Phys. Lett., 2012. 554(0): p. 72-76.


Dynamic nuclear polarization (DNP) can be used to increase the polarization of nuclei by utilizing the higher electron polarization. Typically, in dissolution DNP heteronuclei are directly polarized due to their longer relaxation times. We present the combination of DNP to protons with subsequent cross polarization to 13C followed by dissolution to solution state. The experiment was implemented using a modified dissolution DNP probe. For a [13C]urea sample doped with TEMPO the carbon polarization and its build-up rate could be increased by a factor of two using CP. With small losses, this gain could be transferred to the solution by dissolution.



Wednesday, November 21, 2012

Rapid Natural-Abundance 2D (13) C-(13) C Correlation Spectroscopy Using Dynamic Nuclear Polarization Enhanced Solid-State NMR and Matrix-Free Sample Preparation

Takahashi, H., et al., Rapid Natural-Abundance 2D (13) C-(13) C Correlation Spectroscopy Using Dynamic Nuclear Polarization Enhanced Solid-State NMR and Matrix-Free Sample Preparation. Angew Chem Int Ed Engl, 2012. 51(47): p. n/a-n/a.4


Ultra-fast: Substantial solid-state NMR sensitivity can be achieved using dynamic nuclear polarization and matrix-free sample preparation (that is, absence of solvent and cryoprotectant). This method avoids line-broadening, maximizes sample filling factor, and allows natural-abundance 2D (13) C-(13) C dipolar correlation experiments to be carried out in tens of minutes. MW=microwaves.

Monday, November 19, 2012

The efficiency of DPPH as a polarising agent for DNP-NMR spectroscopy

Lumata, L.L., et al., The efficiency of DPPH as a polarising agent for DNP-NMR spectroscopy. RSC Advances, 2012.


The free radical 2,2-diphenyl-1-pycrylhydrazyl (DPPH) was tested as a polarising agent for fast dissolution dynamic nuclear polarisation (DNP) NMR spectroscopy. DPPH was found to be reasonably soluble in sulfolane and the optimum concentration for DNP is 20-40 mM depending upon whether short polarisation times or the maximum signal intensity is needed. W-band ESR measurements revealed that the ESR linewidth D of DPPH is intermediate between that of BDPA and 4-oxo-TEMPO. Several thousand-fold NMR signal enhancements in the liquid-state were achieved for 13C, 15N, 89Y, and 109Ag compounds, demonstrating that DPPH can be added to the list of polarising agents for DNP-NMR spectroscopy. Furthermore, the hydrophobic DPPH free radical can be easily filtered out from the dissolution liquid when water is used as the dissolution solvent.



Friday, November 16, 2012

Enhanced Solid-State NMR Correlation Spectroscopy of Quadrupolar Nuclei Using Dynamic Nuclear Polarization

Lee, D., et al., Enhanced Solid-State NMR Correlation Spectroscopy of Quadrupolar Nuclei Using Dynamic Nuclear Polarization. J Am Chem Soc, 2012. 134(45): p. 18491-18494.


By means of a true sensitivity enhancement for a solid-state NMR spectroscopy (SSNMR) experiment performed under dynamic nuclear polarization (DNP) conditions, corresponding to 4-5 orders of magnitude of time savings compared with a conventional SSNMR experiment, it is shown that it is possible to record interface-selective (27)Al-(27)Al two-dimensional dipolar correlation spectra on mesoporous alumina, an advanced material with potential industrial applications. The low efficiency of cross-polarization and dipolar recoupling for quadrupolar nuclei is completely negated using this technique. The important presence of pentacoordinated Al has not only been observed, but its role in bridging interfacial tetra- and hexacoordinated Al has been determined. Such structural information, collected at low temperature ( approximately 103 K) and 9.4 T with the use of DNP, would have been impossible to obtain under standard conditions, even using a higher magnetic field. However, here it is demonstrated that this information can be obtained in only 4 h. This work clearly opens a new avenue for the application of SSNMR to quadrupolar nuclei and notably the atomic-scale structure determination of catalysis materials such as mesoporous alumina.

Wednesday, November 14, 2012

Postdoc position in biomolecular solid state NMR at NIH


I expect to have an opening for a new postdoctoral fellow in my research group on the NIH campus in Bethesda, Maryland, starting in mid-2013. Research will focus on structural studies of supramolecular assemblies related to HIV-1 maturation, using solid state NMR, electron microscopy, DNP, etc. Extensive prior experience with protein expression, purification, and labeling is a requirement for this position (because this project depends heavily on non-standard sample preparation). Previous experience with solid state NMR methods is desirable, but not necessary. To apply, please send your CV, a description of your recent research activities, and the names of three references to robertty@mail.nih.gov


Dr. Robert Tycko 
Laboratory of Chemical Physics, NIDDK 
Building 5, Room 112 
National Institutes of Health 
Bethesda, MD 20892-0520 
301-402-8272 (office); 301-402-4687 (lab) 

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Monday, November 12, 2012

Do you miss an article?

Every now and then I have received emails from blog readers bringing articles about DNP-NMR spectroscopy to my attention that I have simply missed. Please keep doing that!

I'm scanning the tables of content of all major publications, but sometimes I just miss an article. Also, sometimes a reference gets lost when I import the bibliographic information in my article library and forget to post it on the blog. Normally I wait until an article is published with all bibliographic information (volume number, page numbers etc.), so if an article is 'in press' or 'just accepted' it sometimes takes a few days/weeks until I post it on here.

However, if you think I missed an article (or any other DNP-NMR related information that you would like to see on here), please, do not hesitate to contact me and let me know what you are missing.

Cheers,
Thorsten

Friday, November 9, 2012

Helium-cooling and -spinning dynamic nuclear polarization for sensitivity-enhanced solid-state NMR at 14T and 30K

Matsuki, Y., et al., Helium-cooling and -spinning dynamic nuclear polarization for sensitivity-enhanced solid-state NMR at 14T and 30K. J. Magn. Reson., 2012. 225(0): p. 1-9.


We describe a 1H polarization enhancement via dynamic nuclear polarization (DNP) at very low sample temperature T ≈ 30 K under magic-angle spinning (MAS) conditions for sensitivity-enhanced solid-state NMR measurement. Experiments were conducted at a high external field strength of 14.1 T. For MAS DNP experiments at T ≪ 90 K, a new probe system using cold helium gas for both sample-cooling and -spinning was developed. The novel system can sustain a low sample temperature between 30 and 90 K for a period of time >10 h under MAS at νR ≈ 3 kHz with liquid He consumption of ≈6 L/h. As a microwave source, we employed a high-power, continuously frequency-tunable gyrotron. At T ≈ 34 K, 1H DNP enhancement factors of 47 and 23 were observed with and without MAS, respectively. On the basis of these observations, a discussion on the total NMR sensitivity that takes into account the effect of sample temperature and external field strength used in DNP experiments is presented. It was determined that the use of low sample temperature and high external field is generally rewarding for the total sensitivity, in spite of the slower polarization buildup at lower temperature and lower DNP efficiency at higher field. These findings highlight the potential of the current continuous-wave DNP technique also at very high field conditions suitable to analyze large and complex systems, such as biological macromolecules.

Wednesday, November 7, 2012

First Announcement: EUROMAR 2013



Dear Colleagues, 

On behalf of the Organizing Committee, it is my pleasure to invite you to EUROMAR 2013, the 9th European Magnetic Resonance Conference that will be organized on the island of Crete/Greece, by the National Center for Scientific Research “Demokritos”. 

The conference will take place between 30th June to 5th July at the Creta Maris Convention Center, a modern facility situated 25 km from the Heraklion International Airport and adjacent to the town of Hersonissos. 

EUROMAR 2013 will bring together distinguished scientists of the magnetic Resonance field in the unique location of Crete that combines Mediterranean landscape with world-renowned historical sites and a rich cultural heritage. The conference will cover all aspects of Magnetic Resonance theory, methodology and applications. The 5-day scientific program will run in three parallel sessions and will be structured around lectures of distinguished invited speakers and oral presentations of selected high-quality abstracts. 

Representative topics include: 

Biosolids, Theory and Computation, Liquid State NMR Methods, Materials and Processes, Transport and Diffusion, Proteins and Nucleic Acids, Metabolomics, Imaging, in Cell and in Vivo studies, Paramagnetic Systems, EPR Methods and Applications, Solid State NMR Methods, Relaxation and Dynamics, Sensitivity Enhancement, Small Molecules and Pharmaceuticals, New Methodologies and Instrumentation Advances, Solid State Physics, Industrial and Cultural Applications. 

Confirmed plenary speakers include: 

Anja Boeckmann (Institute of Biology and Chemistry of Proteins, France) 
Dmitri Budker (University of California Berkeley, U.S.A.) 
Isabella Felli (University of Florence, Italy) 
Daniella Goldfarb (Weizmann Institute of Science, Israel) 
Stephen Hill (NHMFL/ Florida State University, U.S.A.) 
Arno Kentgens (Radbour University, The Netherlands) 
Dominique Massiot (CEMHTI-CNRS, France) 
Alex Pines (University of California Berkeley, U.S.A.) 
Graham Smith (University of St Andrews, United Kingdom) 
Yi-Qiao Song (Schlumberger-Doll Research, U.S.A) 
Shimon Vega (Weizmann Institute of Science, Israel) 
Peter van Zijl (Kennedy Krieger Institute, U.S.A.) 
Charalampos (Babis) Calodimos (Rutgers University, U.S.A.) 

Key dates: 

Conference Registration Opens 01/12/2012 
Early Registration Closes 01/04/2013 
Deadline for Oral Submission 01/05/2013 
Deadline for Poster Submission 31/05/2013 

Website: 

The website of the conference is http://www.euromar2013.org/index.html and is being constantly enriched with the necessary information on the conference, the venues and traveling to Crete. 

I believe that the attractive setting of Crete together with EUROMAR’s high scientific level will provide an excellent forum for rewarding discussions and exchanges between magnetic resonance researchers from around the world. 

Looking forward to welcoming you in Crete, 

Georgios Papavassiliou 
Chairman 
EUROMAR 2013 Conference 

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Monday, November 5, 2012

The 3rd U.S.-Canada Winter School on Biomolecular Solid-State NMR Stowe, Vermont, January 6-11, 2013

The 3rd U.S.-Canada Winter School on Biomolecular Solid-State NMR 
Stowe, Vermont, January 6-11, 2013 

Organizers: Mei Hong (Iowa State), Chad Rienstra (UIUC), and Bob Griffin (MIT) 

Dear colleagues, 

We invite you to encourage your students, postdocs, and associates to attend the 3rd Winter School on Biomolecular Solid-State NMR, to be held on Jan 6-11, 2013, in Stowe, Vermont. Similar to the two previous, very successful, Winter Schools, this pedagogical meeting, unique in North America, is aimed at students and postdocs in the field of biological solid-state NMR, as well as more senior scientists in related fields who are interested in entering this vibrant field. Our goals are to foster the scientific development of the next generation of North American biological solid-state NMR spectroscopists and to encourage information sharing and collaborations among research groups. Topics in the 3rd Winter School include: 

· Basics of solid-state NMR: orientation dependence, density operators, average Hamiltonian theory, dipolar and CSA recoupling 
· Multidimensional correlation techniques: resonance assignment and structure determination 
· Theory of polarization transfer and dipolar decoupling 
· Pushing the sensitivity envelope: dynamic nuclear polarization 
· Solid-state NMR techniques for measuring distances, torsion angles, dynamics and orientations of diamagnetic and paramagnetic systems, for both spin-1/2 and quadrupolar nuclei 
· Beating the 800-pound gorilla: NMR of membrane-bound proteins 
· Devil in the details: methods for protein expression, isotopic labeling, and preparation of MAS and oriented-membrane samples 
· Numerical simulations and structure calculation methods 
· NMR probe design. 

Lectures and problem-solving sessions will be held in the mornings, late afternoons, and evenings, with time for recreation in the early afternoon. 

Speakers: The following people have agreed to give lectures: 

Tim Cross (Florida State) 
Matthias Ernst (ETH) 
Phil Grandinetti (Ohio State) 
Bob Griffin (MIT) 
Mei Hong (Iowa State) 
Yoshitaka Ishii (U Illinois Chicago) 
Chris Jaroniec (Ohio State) 
Ann McDermott (Columbia) 
Stanley Opella (UCSD) 
Chad Rienstra (UIUC) 
Klaus Schmidt-Rohr (Iowa State) 
Robert Tycko (NIH) 
Kurt Zilm (Yale) 

Venue and transportation: The meeting will be held at the Inn at the Mountain in Stowe, http://www.stowe.com/plan/groups/stowe-mountain-resort-the-inn-at-the-mountain/. Stowe is easily accessible from airports in Burlington, VT, Manchester, NH, and Boston, MA. 

Cost: Room and board will be free for attendees. The registration fee is $325 for academic attendees and $600 for industrial attendees. We anticipate space for about 75-80 people. 

Application: Interested students and postdocs should send the following application material as PDF attachments to mhong@iastate.edu <mhong@iastate.edu

1. CV and publication list (for the purpose of room assignment, please indicate your gender in the CV) 
2. A one-page description of the current research 
3. A one-page letter of recommendation from the current research advisor. 

(In the case of a senior scientist, a brief explanation of your motivations can substitute for a letter of recommendation.)

Postdoctoral Position in DNP Development

Postdoctoral Position for developing new spectroscopic methods in DNP NMR 


A postdoctoral position is available immediately at the U.S. National High Magnetic Field Lab (NHMFL) in Tallahassee, FL, for developing new DNP techniques to enable liquid state NMR spectroscopy with a focus on high resolution NMR studies at high fields. This project builds on recent developments in Gyrotron sources and shuttling DNP systems to produce highly polarized small molecules for NMR characterizations. 

Interested candidates should have a strong background in one or more of the following areas: NMR sample shuttling and solution NMR spectroscopy, development and application of new NMR hardware and methods, NMR in super-critical fluids, dynamic nuclear polarization, millimeter-wave and high-frequency EPR hardware development. 

This project is an NSF MRI-funded partnership between the NMR and EMR groups at the NHMFL to develop a new platform for DNP-enhanced NMR spectroscopy to enable solution NMR characterization of sensitivity-limited samples. This endeavor leverages collaborative efforts between the groups of Steve Hill and Bill Brey at Florida State University, Joanna R. Long at the University of Florida and Lucio Frydman at the Weizmann Institute and Florida State University and is part of a NHMFL initiative to develop a user program in DNP, which includes projects to offer dissolution DNP at the University of Florida and MAS DNP and Overhauser DNP at Florida State University. The position is available immediately, and interested candidates should send their CV's, including letters from three references, to Prof. Steve Hill (shill@magnet.fsu.edu). 


Florida State University is an Affirmative Action/Equal Opportunity employer 
and solicits applications from women and under-represented minorities. 

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Friday, November 2, 2012

The theory and practice of hyperpolarization in magnetic resonance using parahydrogen


Green, R.A., et al., The theory and practice of hyperpolarization in magnetic resonance using parahydrogen. Prog Nucl Magn Reson Spectrosc, 2012. 67(0): p. 1-48.


Unfortunately there is currently no abstract available.

Thursday, November 1, 2012

Postdoctoral Positions in DNP


As part of a new initiative at the U.S. National High Magnetic Field Laboratory, several postdoctoral positions are available. Our goals are two-fold: 1) to develop a user facility where external users can collect DNP data and 2) to develop DNP technologies in concert with others in the field, with a particular focus on high magnetic fields/frequencies. 

I would appreciate it if you could pass on this email to anyone potentially interested in these positions. Details can be found in the attached position descriptions. I apologize if you have received more than one email regarding these positions. 



Sincerely, 
Joanna 



Joanna R. Long 
Assoc. Professor of Biochemistry & Molecular Biology 
Director, Advanced Magnetic Resonance Imaging and Spectroscopy Facility 
National High Magnetic Field Laboratory 
McKnight Brain Institute, LG-187 
University of Florida 
Box 100245 
Gainesville, FL 32610-0245 
(352)846-1506 – Telephone 
(352)392-3422 – Fax

Wednesday, October 31, 2012

Nuclear Magnetic Resonance of Hyperpolarized Fluorine for Characterization of Protein–Ligand Interactions

Lee, Y., et al., Nuclear Magnetic Resonance of Hyperpolarized Fluorine for Characterization of Protein–Ligand Interactions. J. Am. Chem. Soc., 2012. 134(42): p. 17448-17451.


Fluorine NMR spectroscopy is widely used for detection of protein?ligand interactions in drug discovery because of the simplicity of fluorine spectra combined with a relatively high likelihood for a drug molecule to include at least one fluorine atom. In general, an important limitation of NMR spectroscopy in drug discovery is its sensitivity, which results in the need for unphysiologically high protein concentrations and large ligand:protein ratios. An enhancement in the 19F signal of several thousand fold by dynamic nuclear polarization allows for the detection of submicromolar concentrations of fluorinated small molecules. Techniques for exploiting this gain in signal to detect ligands in the strong-, intermediate-, and weak-binding regimes are presented. Similar to conventional NMR analysis, dissociation constants are determined. However, the ability to use a low ligand concentration permits the detection of ligands in slow exchange that are not easily amenable to drug screening by traditional NMR methods. The relative speed and additional information gained may make the hyperpolarization-based approach an interesting alternative for use in drug discovery.



Friday, October 26, 2012

Fast passage dynamic nuclear polarization on rotating solids

Mentink-Vigier, F., et al., Fast passage dynamic nuclear polarization on rotating solids. J. Magn. Reson., 2012. 224(0): p. 13-21.


Magic Angle Spinning (MAS) Dynamic Nuclear Polarization (DNP) has proven to be a very powerful way to improve the signal to noise ratio of NMR experiments on solids. The experiments have in general been interpreted considering the Solid-Effect (SE) and Cross-Effect (CE) DNP mechanisms while ignoring the influence of sample spinning. In this paper, we show experimental data of MAS-DNP enhancements of 1H and 13C in proline and SH3 protein in glass forming water/glycerol solvent containing TOTAPOL. We also introduce a theoretical model that aims at explaining how the nuclear polarization is built in MAS-DNP experiments. By using Liouville space based simulations to include relaxation on two simple spin models, {electron–nucleus} and {electron–electron–nucleus}, we explain how the basic MAS-SE-DNP and MAS-CE-DNP processes work. The importance of fast energy passages and short level anti-crossing is emphasized and the differences between static DNP and MAS-DNP is explained. During a single rotor cycle the enhancement in the {electron–electron–nucleus} system arises from MAS-CE-DNP involving at least three kinds of two-level fast passages: an electron–electron dipolar anti-crossing, a single quantum electron MW encounter and an anti-crossing at the CE condition inducing nuclear polarization in- or decrements. Numerical, powder-averaged, simulations were performed in order to check the influence of the experimental parameters on the enhancement efficiencies. In particular we show that the spinning frequency dependence of the theoretical MAS-CE-DNP enhancement compares favorably with the experimental 1H and 13C MAS-DNP enhancements of proline and SH3.

Thursday, October 25, 2012

4th International DNP Symposium in Copenhagen

Dear Friends and Colleagues 

We are happy to announce the "4th International DNP Symposium", Aug 28-31, 2013, in Copenhagen, Denmark: www.DNPsymposium.org. Please mark your calenders. 

The meeting follows the highly successful previous meetings in Nottingham (2007), Koenigstein (2009) and Lausanne (2011). 

Over the three days of the meeting there will be series of talks from esteemed researchers in the field assessing the present state of the art. The symposium will cover the basic science across physics, chemistry and biology as well as the engineering challenges and applications. DNP and hyperpolarization has lead to some very significant new applications in NMR and MRI, and we are only at the beginning of exploring the opportunities. 

The symposium will accept abstracts for oral and poster presentation selection. 

Registration will open January 2013, and we will send you a reminder email as soon as the website is open for registration. 

The organizing committee, 

Jan H. Ardenkjaer-Larsen 

Lars G. Hanson 
Charlotte H Gotfredsen 
Susanne L. Mossin 
Sebastian Meier 
Lise V. Søgaard 
Niels Chr Nielsen 

Monday, October 22, 2012

Transfer of the Haupt-hyperpolarization to neighbor spins

Icker, M., P. Fricke, and S. Berger, Transfer of the Haupt-hyperpolarization to neighbor spins. J. Magn. Reson., 2012. 223(0): p. 148-150.


The NMR hyperpolarization observed for freely rotating methyl groups by exerting a temperature jump from 4.2 K to 298 K can be transferred to spins which have a spin, spin coupling with the carbon of the methyl group. First, a spin echo sequence readjusts the primary up/down signals to an in-phase multiplet. This in-phase magnetization is then decoupled and transferred by a simple COSY step using one scan. The polarization factors at the neighbor spins are about 50 by comparing their signal-to-noise ratio with the signal strength after full relaxation.

Friday, October 19, 2012

Optimisation of dynamic nuclear polarisation of [1-13C] pyruvate by addition of gadolinium-based contrast agents


Friesen-Waldner, L., et al., Optimisation of dynamic nuclear polarisation of [1-13C] pyruvate by addition of gadolinium-based contrast agents. J. Magn. Reson., 2012. 223(0): p. 85-89.


Dynamic nuclear polarisation (DNP) of carbon-13 (13C) enriched endogenous compounds provides a novel means for magnetic resonance imaging and spectroscopy of biological processes. Adding small amounts of gadolinium-based contrast agents (GBCAs) to the 13C-enriched substrate matrix increases the amount of hyperpolarisation that can be achieved, but also may decrease the longitudinal relaxation time (T1) of the 13C nucleus in solution. This study examined the effects of five different GBCA at concentrations of 0.5, 1, 2, and 3 mM on [1-13C]-enriched pyruvic acid. It was found that contrast agents with an open chain structure (Gadobenate dimeglumine, Gadopentetate dimeglumine, Gadodiamide) caused the largest enhancement (up to 82%) in solid state polarisation relative to solutions without GBCA. In the liquid state, T1 of pyruvate decreased by as much as 62% and polarisation was much lower (70%) relative to solutions without GBCA added. Conversely, for GBCA with macrocyclic structures (Gadoterate meglumine, Gadoteridol), the solid state polarisation enhancement was only slightly less than the open chain GBCA, but enhanced polarisation was retained much better in the liquid state with minimal decrease in T1 (25% at the highest GBCA concentrations). Near maximum polarisation in the solid state was obtained at a GBCA concentration of 2 mM, with a higher concentration of 3 mM producing minimal improvement. These results indicate that the macrocyclic contrast agents provide the best combination of high solid state and liquid state polarisations with minimal loss of T1 in experiments with hyperpolarised 13C-enriched pyruvate. This suggests that macrocyclic contrast agents should be the GBCA of choice for maximising signal in experiments with hyperpolarised 13C-enriched pyruvate, particularly for in vivo measurements where shortened substrate T1 is especially problematic.

Tuesday, October 16, 2012

Simple and Highly Sensitive Measurement Method for Detection of Glass Transition Temperatures of Polymers: Application of ESR Power Saturation Phenomenon with Conventional Spin-Probe Technique

This is not an article about DNP spectroscopy. However, it shows how EPR spectroscopy and nitroxide spin labels can be used to characterize mobility of soft matter through shape analysis of the EPR spectrum. Since mobility and relaxation is directly connected I thought this article could also be of interest to the DNP community.


Miwa, Y. and K. Yamamoto, Simple and Highly Sensitive Measurement Method for Detection of Glass Transition Temperatures of Polymers: Application of ESR Power Saturation Phenomenon with Conventional Spin-Probe Technique. The Journal of Physical Chemistry B, 2012. 116(30): p. 9277-9284.

A combination of the microwave power saturation (MPS) method of electron spin resonance (ESR) and spin probing is proposed as a simple and practical technique for detecting the glass transition temperatures, Tg, of polymers with high sensitivity. Effects of the spin-probe size and concentration on the Tg value of polystyrene (PS) determined by MPS, Tg,ESR, were first evaluated. Spin-probed PS with four types of nitroxides, namely, di-tert-butyl nitroxide (DBN), 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl (BZONO), and 4?,4?-dimethyl-spiro(5α-cholestane-3,2?-oxazolidin)-3?-yloxy free radical (CHOL), having molecular weights of 144, 156, 276, and 473, respectively, and spin-labeled PS with TEMPO were prepared. The Tg,ESR values for the spin-probed PS with DBN, TEMPO, BZONO, and CHOL and spin-labeled PS were determined to 360, 363, 374, 374, and 375 K, respectively, within experimental uncertainties of 2 K, whereas the glass transition temperature determined by DSC, Tg,DSC, was 375 K for all samples. A significant decrease in Tg,ESR for small spin probes was shown to be due to decoupling between the mobilities of small spin probes and PS segments. Concerning the concentration, a decrease in the saturation factor, S, induced by shortening of the spin?spin relaxation time was observed for the spin-probed PS with CHOL when the concentration of CHOL was more than 1.0 wt %. Furthermore, Tg,ESR decreased slightly with increasing weight fraction of CHOL because of the ?plasticizer effect? of CHOL. However, the Tg,ESR and Tg,DSC values corresponded for each concentration. Thus, large spin probes, such as CHOL and BZONO, are appropriate for the determination of Tg,ESR values; the concentration of the spin probes does not affect the Tg,ESR value unless the overall Tg value is reduced by blending of excess spin probes. Finally, measurements of Tg,ESR in PS/silica composites containing more than 95 wt % silica are shown as an application example of the present method. Tg,ESR was clearly determined even for the PS/silica composites with 98 wt % silica; a decrease in Tg,ESR with increasing silica content was observed.



Monday, October 15, 2012

Distance measurements across randomly distributed nitroxide probes from the temperature dependence of the electron spin phase memory time at 240GHz

Edwards, D.T., et al., Distance measurements across randomly distributed nitroxide probes from the temperature dependence of the electron spin phase memory time at 240GHz. J. Magn. Reson., 2012. 223(0): p. 198-206.


At 8.5 T, the polarization of an ensemble of electron spins is essentially 100% at 2 K, and decreases to 30% at 20 K. The strong temperature dependence of the electron spin polarization between 2 and 20 K leads to the phenomenon of spin bath quenching: temporal fluctuations of the dipolar magnetic fields associated with the energy-conserving spin “flip-flop” process are quenched as the temperature of the spin bath is lowered to the point of nearly complete spin polarization. This work uses pulsed electron paramagnetic resonance (EPR) at 240 GHz to investigate the effects of spin bath quenching on the phase memory times (TM) of randomly-distributed ensembles of nitroxide molecules below 20 K at 8.5 T. For a given electron spin concentration, a characteristic, dipolar flip-flop rate (W) is extracted by fitting the temperature dependence of TM to a simple model of decoherence driven by the spin flip-flop process. In frozen solutions of 4-Amino-TEMPO, a stable nitroxide radical in a deuterated water–glass, a calibration is used to quantify average spin–spin distances as large as <r> = 6.6 nm from the dipolar flip-flop rate. For longer distances, nuclear spin fluctuations, which are not frozen out, begin to dominate over the electron spin flip-flop processes, placing an effective ceiling on this method for nitroxide molecules. For a bulk solution with a three-dimensional distribution of nitroxide molecules at concentration n, we find W ∝ n ∝ 1 / r ¯ 3 , which is consistent with magnetic dipolar spin interactions. Alternatively, we observe W ∝ n 3 2 for nitroxides tethered to a quasi two-dimensional surface of large (Ø ∼ 200 nm), unilamellar, lipid vesicles, demonstrating that the quantification of spin bath quenching can also be used to discern the geometry of molecular assembly or organization.

Friday, October 12, 2012

A 140 GHz pulsed EPR/212 MHz NMR spectrometer for DNP studies

Smith, A.A., et al., A 140 GHz pulsed EPR/212 MHz NMR spectrometer for DNP studies. J. Magn. Reson., 2012. 223(0): p. 170-179.


We described a versatile spectrometer designed for the study of dynamic nuclear polarization (DNP) at low temperatures and high fields. The instrument functions both as an NMR spectrometer operating at 212 MHz (1H frequency) with DNP capabilities, and as a pulsed-EPR operating at 140 GHz. A coiled TE011 resonator acts as both an NMR coil and microwave resonator, and a double balanced (1H, 13C) radio frequency circuit greatly stabilizes the NMR performance. A new 140 GHz microwave bridge has also been developed, which utilizes a four-phase network and ELDOR channel at 8.75 GHz, that is then multiplied and mixed to obtain 140 GHz microwave pulses with an output power of 120 mW. Nutation frequencies obtained are as follows: 6 MHz on S = 1/2 electron spins, 100 kHz on 1H, and 50 kHz on 13C. We demonstrate basic EPR, ELDOR, ENDOR, and DNP experiments here. Our solid effect DNP results demonstrate an enhancement of 144 and sensitivity gain of 310 using OX063 trityl at 80 K and an enhancement of 157 and maximum sensitivity gain of 234 using Gd-DOTA at 20 K, which is significantly better performance than previously reported at high fields (⩾3 T).

Wednesday, October 10, 2012

First determination of the spin relaxation properties of a nitronyl nitroxide in solution by electron spin echoes at X-band: A comparison with Tempone

This article describes no DNP results. However, it can be still of interest for the solution-state DNP community since it discusses relaxation times of nitroxide spin-labels.


Collauto, A., A. Barbon, and M. Brustolon, First determination of the spin relaxation properties of a nitronyl nitroxide in solution by electron spin echoes at X-band: A comparison with Tempone. J. Magn. Reson., 2012. 223(0): p. 180-186.


We studied by electron spin echo pulse methods the spin relaxation properties of a phenyl nitronyl nitroxide radical (2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide, PTIO) at X-band in fluid toluene solution in a wide temperature range, and in a water/glycerol 1:1 mixture near room temperature. The relaxation properties of PTIO have been compared with that of Tempone, as a widely used nitroxide. By a new procedure, based on experimental results on the temperature dependences of the relaxation times T1 and T2, and on the approximation of an isotropic Brownian rotational diffusion, we separated non-secular, spin rotational and residual terms from the transverse relaxation rate to isolate secular and pseudosecular contributions. By comparing the results for the two radicals we found the differences in the magnetic properties that give rise to slower transverse (T2) and longitudinal (T1) electron spin relaxation for PTIO in the whole temperature range explored in this work.



Monday, October 8, 2012

Field dependence of the relaxation of 79Br in KBr and its use as a temperature calibrant

Beckett, P., et al., Field dependence of the relaxation of 79Br in KBr and its use as a temperature calibrant. J. Magn. Reson., 2012. 223(0): p. 61-63.


The longitudinal relaxation time of 79Br nuclei in KBr is field independent, between 4.7 T and 14.1 T. The results suggest that inconsistencies in the literature are due to differences in the experimental set-ups. The limitations of KBr as temperature calibrant are discussed.

Friday, October 5, 2012

Dynamic Nuclear Polarization NMR Spectroscopy of Microcrystalline Solids

This is a very interesting article, since it demonstrates how DNP can be tremendously helpful for the characterization of small molecules (e.g. quality control of pharmaceutical formulas). Here, DNP-enhanced 13C-13C correlation spectra are presented that are recorded using unlabeled material and the glass-forming solvents were carefully chosen so the analyte remains unaltered.

Rossini, A.J., et al., Dynamic Nuclear Polarization NMR Spectroscopy of Microcrystalline Solids. J. Am. Chem. Soc., 2012.


Dynamic nuclear polarization (DNP) solid-state NMR has been applied to powdered microcrystalline solids to obtain sensitivity enhancements on the order of 100. Glucose, sulfathiazole, and paracetamol were impregnated with bis-nitroxide biradical (bis-cyclohexyl-TEMPO-bisketal, bCTbK) solutions of organic solvents. The organic solvents were carefully chosen to be nonsolvents for the compounds, so that DNP-enhanced solid-state NMR spectra of the unaltered solids could be acquired. A theoretical model is presented that illustrates that for externally doped organic solids characterized by long spin?lattice relaxation times (T1(1H) > 200 s), 1H?1H spin diffusion can relay enhanced polarization over micrometer length scales yielding substantial DNP enhancements (ε). ε on the order of 60 are obtained for microcrystalline glucose and sulfathiazole at 9.4 T and with temperatures of ca. 105 K. The large gain in sensitivity enables the rapid acquisition of 13C-13C correlation spectra at natural isotopic abundance. It is anticipated that this will be a general method for enhancing the sensitivity of solid-state NMR experiments of organic solids.



Wednesday, October 3, 2012

Techniques in DNP-NMR Spectroscopy

Check out my second blog post that I wrote for the SpinSights blog. It gives a short overview about the different techniques of DNP-NMR spectroscopy.



Here is a quick summary:

  • DNP can be separated into four different areas based on whether DNP is performed at high or low magnetic field strengths (1,2 vs. 3,4) or in the solid or solution state (1,3 vs. 2,4). In principle it is always possible to directly polarize a sample, but some (direct) polarizing methods are more challenging than others. E.g. at low magnetic fields (cases 3 and 4) a solid-state source can be used, but the output power of such solid-sate microwave/THz sources drops off drastically at higher frequencies. In these cases a gyrotron can be used (cases 1 and 2).
  • For solution-state NMR the situation is more challenging due to the high ohmic losses of the liquid NMR sample and severe heating that occurs (think microwave oven). To prevent this, a resonance structure (resonator) is required to separate the electric field components of the THz radiation from the magnetic field components. This becomes very challenging since at high frequencies (e.g. 400 MHz 1H, 268 GHz e-) the wavelength of the THz radiation is 1.12 mm and therefore fundamental mode devices are very small and can accommodate only very small amounts of liquid sample. This has led to the development of several other techniques:
    • Temperature-Jump DNP (A): In a TJ-DNP experiment the sample (10 – 20 microliters) is polarized in-situ at 90 K using a gyrotron as the THz source. Once the sample is polarized, the sample is rapidly melted using a laser flash, and the NMR experiment can be performed. After the laser is turned off, the sample freezes and can be polarized again.
    • Dissolution-DNP (B): In a dissolution experiment the sample is polarized ex-situ in the solid-state at liquid Helium temperatures at 3.3T using a low-power solid-state 95 GHz microwave source. The sample is then melted using a hot solvent and rapidly transferred into the high-field NMR spectrometer for detection.
    • Shuttle DNP9-10 (arrow C): In a shuttle-DNP experiment, the sample is polarized at a low magnetic field and then physically shuttled into the high-field NMR magnet to acquire the NMR spectrum.

Monday, October 1, 2012

Physical methods and techniques NMR spectroscopy

This article came a bit as a surprise. I didn't expect DNP to show up in a review article published in a journal for organic chemistry. However, I'm very delighted to see that since it shows that researchers from many different areas become aware of the method.


Edgar, M., Physical methods and techniques NMR spectroscopy. Annual Reports Section "B" (Organic Chemistry), 2012. 108(0): p. 292-315.


NMR spectroscopy continues to evolve, with publications in 2011 providing an eclectic collection of applications, advances and incremental improvements. Publications highlights include: DNP in liquids and solids, decoupling effects at high spinning speed in solid-state, results from the 80 kHz spinning-speed 1 mm MAS rotor, enhanced diffusion methods, results from the new 1.0 GHz magnet, an intent to create a 1.3 GHz magnet, results from the 2.6 GHz pulsed-magnet, a cryogen-free MRI, and the use of multiple receivers to acquire multiple experiments within the same pulse sequence. I am indebted to the great and the good whose work has been reported here, all credit is theirs; errors, omissions and blame are all mine.





Friday, September 28, 2012

Cluster formation restricts dynamic nuclear polarization of xenon in solid mixtures

Kuzma, N.N., et al., Cluster formation restricts dynamic nuclear polarization of xenon in solid mixtures. J. Chem. Phys., 2012. 137(10): p. 104508-6.


During dynamic nuclear polarization (DNP) at 1.5 K and 5 T, 129Xe nuclear magnetic resonance (NMR) spectra of a homogeneous xenon/1-propanol/trityl-radical solid mixture exhibit a single peak, broadened by 1H neighbors. A second peak appears upon annealing for several hours at 125 K. Its characteristic width and chemical shift indicate the presence of spontaneously formed pure Xe clusters. Microwave irradiation at the appropriate frequencies can bring both peaks to either positive or negative polarization. The peculiar time evolution of 129Xe polarization in pure Xe clusters during DNP can be modelled as an interplay of spin diffusion and T1 relaxation. Our simple spherical-cluster model offers a sensitive tool to evaluate major DNP parameters in situ, revealing a severe spin-diffusion bottleneck at the cluster boundaries and a significant sample overheating due to microwave irradiation. Subsequent DNP system modifications designed to reduce the overheating resulted in four-fold increase of 129Xe polarization, from 5.3% to 21%.

Wednesday, September 26, 2012

Development and Applications of High—Frequency Gyrotrons in FIR FU Covering the sub-THz to THz Range

Idehara, T. and S. Sabchevski, Development and Applications of High—Frequency Gyrotrons in FIR FU Covering the sub-THz to THz Range. J. Infrared Millim. Te., 2012. 33(7): p. 667-694.


Powerful sources of coherent radiation in the sub-terahertz and in the terahertz frequency range of the electromagnetic spectrum are necessary for a great and continuously expanding number of applications in the physical research and in various advanced technological processes as well as in radars, communication systems, for remote sensing and inspection etc .. In recent years, a spectacular progress in the development of various gyro-devices and in particular of the powerful high frequency (sub-terahertz and terahertz) gyrotron oscillators has demonstrated a remarkable potential for bridging the so-called terahertz power gap and stimulated many novel and prospective applications. In this review paper we outline two series of such devices, namely the Gyrotron FU Series which includes pulsed gyrotrons and Gyrotron FU CW Series which consist of tubes operated in a CW (continuous wave) or long pulse mode, both developed at the FIR FU Center. We present the most remarkable achievements of these devices and illustrate their applications by some characteristic examples. An outlook for the further extension of the Gyrotron FU CW Series is also provided.


Monday, September 24, 2012

Development of a Compact sub-THz Gyrotron FU CW CI for Application to High Power THz Technologies

Idehara, T., et al., Development of a Compact sub-THz Gyrotron FU CW CI for Application to High Power THz Technologies. J. Infrared Millim. Te., 2012. 33(7): p. 724-744.


For application of high frequency gyrotron to high power THz technology, Gyrotron FU CW series is being developed in FIR FU. Gyrotron FU CW CI is developed as one of sub-THz gyrotrons included in the series. The advantage of the gyrotron is compactness using a compact superconducting magnet and compact power supply system, which makes the accesses of the gyrotron to applied large-scale devices easier and extends the applications of gyrotron to wider fields. The designed frequency and cavity mode are 394.5 GHz and TE 26 mode for application to the 600 MHz DNP-NMR spectroscopy. As the operation results, the frequency and the output power were 394.03 GHz and around 30 W, respectively, which are available for the application to the 600 MHz DNP-NMR measurement. In addition, this gyrotron can operate at many other frequencies and cavity modes for application to high power THz technologies in wide fields. In this paper, the design and the operation results including long pulse or CW mode are presented.


Thursday, September 20, 2012

1H relaxation dispersion in solutions of nitroxide radicals: Effects of hyperfine interactions with 14N and 15N nuclei

Kruk, D., et al., 1H relaxation dispersion in solutions of nitroxide radicals: Effects of hyperfine interactions with 14N and 15N nuclei. J. Chem. Phys., 2012. 137(4): p. 044512-12.

1H relaxation dispersion of decalin and glycerol solutions of nitroxide radicals, 4-oxo-TEMPO-d16-15N and 4-oxo-TEMPO-d16-14N was measured in the frequency range of 10 kHz–20 MHz (for 1H) using STELAR Field Cycling spectrometer. The purpose of the studies is to reveal how the spin dynamics of the free electron of the nitroxide radical affects the proton spin relaxation of the solvent molecules, depending on dynamical properties of the solvent. Combining the results for both solvents, the range of translational diffusion coefficients, 10−9–10−11 m2/s, was covered (these values refer to the relative diffusion of the solvent and solute molecules). The data were analyzed in terms of relaxation formulas including the isotropic part of the electron spin – nitrogen spin hyperfine coupling (for the case of 14N and 15N) and therefore valid for an arbitrary magnetic field. The influence of the hyperfine coupling on 1H relaxation of solvent molecules depending on frequency and time-scale of the translational dynamics was discussed in detail. Special attention was given to the effect of isotope substitution (14N/15N). In parallel, the influence of rotational dynamics on the inter-molecular (radical – solvent) electron spin – proton spin dipole-dipole coupling (which is the relaxation mechanism of solvent protons) was investigated. The rotational dynamics is of importance as the interacting spins are not placed in the molecular centers. It was demonstrated that the role of the isotropic hyperfine coupling increases for slower dynamics, but it is of importance already in the fast motion range (10−9m2/s). The isotope effects is small, however clearly visible; the 1H relaxation rate for the case of 15N is larger (in the range of lower frequencies) than for 14N. It was shown that when the diffusion coefficient decreases below 5 × 10−11 m2/s electron spin relaxation becomes of importance and its role becomes progressively more significant when the dynamics slows done. As far as the influence of the rotational dynamics is concerned, it was show that this process is of importance not only in the range of higher frequencies (like for diamagnetic solutions) but also at low and intermediate frequencies.

Friday, September 14, 2012

Theory for cross effect dynamic nuclear polarization under magic-angle spinning in solid state nuclear magnetic resonance: The importance of level crossings

Thurber, K.R. and R. Tycko, Theory for cross effect dynamic nuclear polarization under magic-angle spinning in solid state nuclear magnetic resonance: The importance of level crossings. J. Chem. Phys., 2012. 137(8): p. 084508-14.


We present theoretical calculations of dynamic nuclear polarization (DNP) due to the cross effect in nuclear magnetic resonance under magic-angle spinning (MAS). Using a three-spin model (two electrons and one nucleus), cross effect DNP with MAS for electron spins with a large g-anisotropy can be seen as a series of spin transitions at avoided crossings of the energy levels, with varying degrees of adiabaticity. If the electron spin-lattice relaxation time T(1e) is large relative to the MAS rotation period, the cross effect can happen as two separate events: (i) partial saturation of one electron spin by the applied microwaves as one electron spin resonance (ESR) frequency crosses the microwave frequency and (ii) flip of all three spins, when the difference of the two ESR frequencies crosses the nuclear frequency, which transfers polarization to the nuclear spin if the two electron spins have different polarizations. In addition, adiabatic level crossings at which the two ESR frequencies become equal serve to maintain non-uniform saturation across the ESR line. We present analytical results based on the Landau-Zener theory of adiabatic transitions, as well as numerical quantum mechanical calculations for the evolution of the time-dependent three-spin system. These calculations provide insight into the dependence of cross effect DNP on various experimental parameters, including MAS frequency, microwave field strength, spin relaxation rates, hyperfine and electron-electron dipole coupling strengths, and the nature of the biradical dopants.



Wednesday, September 12, 2012

Gyrotron DNP NMR, post-doc position

A 4 year postdoc position is available at the EPF in Lausanne. More information can be found here:


If the link doesn't work, go to http://www.telejob.ethz.ch/ and search for DNP


Inserat Nr. 21707
Vom Mittwoch, 12. September 2012
Arbeitsort Lausanne
Arbeitsbeginn sofort
Vertragsdauer 4 Jahre
Anstellung 100%


EPFL enjoys a strong position in Dynamic Nuclear Polarization for NMR, because it has developed original designs using several approaches. A campus-wide collaboration in particular with the CRPP (fusion research center, specialized in gyrotrons) has allowed us to design and build a gyrotron for solid state NMR. The physical properties of the gyrotron were first investigated at CRPP. The gyrotron will move to our NMR lab in October. Together with another post-doc already in place, the successful applicant will run all the necessary tests prior to engaging in NMR research activities per say. Funding is of EPFL, implying that the research is not tied to existing proposal. We benefit greatly from a close ties with Swiss-to-12, a company dedicated to the manufacturing of THz components. 

Contact : jean-philippe.ansermet@epfl.ch See : http://www.lpmn.ch

Thursday, September 6, 2012

Liquid state DNP for water accessibility measurements on spin-labeled membrane proteins at physiological temperatures

Doll, A., et al., Liquid state DNP for water accessibility measurements on spin-labeled membrane proteins at physiological temperatures. J. Magn. Reson., 2012. 222(0): p. 34-43.


We demonstrate the application of continuous wave dynamic nuclear polarization (DNP) at 0.35T for site-specific water accessibility studies on spin-labeled membrane proteins at concentrations in the 10-100muM range. The DNP effects at such low concentrations are weak and the experimentally achievable dynamic nuclear polarizations can be below the equilibrium polarization. This sensitivity problem is solved with an optimized home-built DNP probe head consisting of a dielectric microwave resonator and a saddle coil as close as possible to the sample. The performance of the probe head is demonstrated with both a modified pulsed EPR spectrometer and a dedicated CW EPR spectrometer equipped with a commercial NMR console. In comparison to a commercial pulsed ENDOR resonator, the home-built resonator has an FID detection sensitivity improvement of 2.15 and an electron spin excitation field improvement of 1.2. The reproducibility of the DNP results is tested on the water soluble maltose binding protein MalE of the ABC maltose importer, where we determine a net standard deviation of 9% in the primary DNP data in the concentration range between 10 and 100muM. DNP parameters are measured in a spin-labeled membrane protein, namely the vitamin B(12) importer BtuCD in both detergent-solubilized and reconstituted states. The data obtained in different nucleotide states in the presence and absence of binding protein BtuF reveal the applicability of this technique to qualitatively extract water accessibility changes between different conformations by the ratio of primary DNP parameters . The -ratio unveils the physiologically relevant transmembrane communication in the transporter in terms of changes in water accessibility at the cytoplasmic gate of the protein induced by both BtuF binding at the periplasmic region of the transporter and ATP binding at the cytoplasmic nucleotide binding domains.

Tuesday, September 4, 2012

Course on "Dissolution Dynamic Nuclear Polarization for NMR spectroscopy" November 14-16, 2012 at EPFL, Switzerland

Repost from: AMPERE MAGNETIC RESONANCE mailing list: 


We would like to announce a three-day course for PhD students and Post-Docs on 

"Dissolution Dynamic Nuclear Polarization" 

The course will start at 1pm on Wednesday November the 14th and will end at 5pm on Friday 16th, and will be held at the Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland, at the Laboratory of Biomolecular Magnetic Resonance (LRMB). 
The course is supported by the COST network 'EuroHyperPol'. Travel stipends will be awarded on a competitive base by an international committee. Students and Post-Docs are invited to describe their interest by email, and forward a letter of support from their supervisors. 

* Registration 
please register at the following adress: 
subscription fees: 100 CHF 

* Information 
geoffrey.bodenhausen (at) epfl.ch
sami.jannin (at) epfl.ch

* Objectives 
Dissolution Dynamic Nuclear Polarization (DNP) provides a way to enhance NMR signals in liquids by more than 4 orders of magnitude. We present the current state-of-the-art and recent advances of this technique. 

* Content 
Lectures and seminars: 11 Hours 
Experimental demonstrations with hands-on participation: 7 Hours 

Day 1: Lectures, 1 pm - 5 pm: Theoretical aspects of DNP 

- Introduction to DNP-enhanced NMR 
- Principles of Dissolution-DNP 
- Low temperature DNP Mechanisms 
- Applications to imaging and chemistry 

Day 2: Lectures, 9 am - 12 am: Experimental aspects of DNP 

- Hardware for DNP 
- Hardware for Dissolution 

Demonstrations, 1 pm - 5 pm 

- Sample Preparation 
- Preparation of a dissolution DNP experiment 

Day 3: Demonstrations, 9 am - 12 am: Practical DNP at the Laboratory of Biomolecular Magnetic Resonance (LRMB) 

- Dissolution DNP experiments 

Seminars, 1 pm - 5 pm 

- All students are expected to give a short presentation on applications of DNP that they wish to implement to enhance their own research subjects 

*Required prior knowledge 
Basic understanding of NMR 

Sami Jannin 
Laboratory of Biomolecular Magnetic Resonance (LRMB) 

Paper mail: 

EPFL 
LRMB - ISIC - SB 
BCH 1534 (Bâtiment de chimie UNIL) 
CH-1015 Lausanne 
Switzerland 

Phone +41 21 693 97 24 
Fax +41 21 693 94 35