Monday, March 30, 2015

[NMR] Marie Skłodowska-Curie Fellow – Dynamic Nuclear Polarisation NMR Spectroscopy

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Marie Skłodowska-Curie Fellow – Dynamic Nuclear Polarisation NMR Spectroscopy

Salary: £28798 to £32469 per annum in accordance with the EC Marie Skłodowska-Curie financial guidelines for this scheme

Dynamic Nuclear Polarisation (DNP) is a method that can be used to generate significant signal enhancements in NMR or MRI experiments. The optimisation of this technique and its adaptation to a wide range of novel NMR experiments is one of the objectives of a new European Initial Training Network EUROPOL, funded by the EU Horizon 2020 Marie Sklodowska-Curie Actions. EUROPOL brings together 11 groups working in the field of sensitivity enhancement for MRI and NMR. The EUROPOL ITN will provide training to Early Stage Researchers (ESRs) in all the topics underlying the advancement of magnetic resonance research.

The Sir Peter Mansfield Magnetic Resonance Centre, which is part of the School of Physics and Astronomy of the University of Nottingham, has a vacancy for an Early Stage Researcher (ESR), funded for a period of 36 months. The successful candidate will register for a PhD at The University of Nottingham (http://www.nottingham.ac.uk) and will carry out the majority of research in the Sir Peter Mansfield Magnetic Resonance Centre (http://www.nottingham.ac.uk/magres/index.aspx) working on the development of novel fast detection techniques for DNP enhanced NMR spectroscopy and micro-imaging with a particular focus on investigations of molecular dynamics. The project will be supervised by Dr Walter Köckenberger.

Requirements

The successful applicant will be required to satisfy the eligibility criteria for Marie Skłodowska-Curie Early Stage Researchers http://ec.europa.eu/research/participants/data/ref/h2020/wp/2014_2015/main/h2020-wp1415-msca_en.pdf , i.e. 
Must be within the first four years (full-time equivalent) of their research career 
Must not yet have been awarded a doctoral degree 
Must not have resided or carried out their main activity (work, studies, etc.) within the UK for more than 12 months in the three years immediately prior to recruitment (short stays such as holidays are not taken into account) 

The applicant will also be expected to have a first or upper second class honours (or equivalent) undergraduate degree in physics or a related discipline.

This full-time post will be offered on a fixed-term contract for a period of 36 months.

For further details please see


Contact

Informal enquiries may be addressed to Dr Walter Köckenberger. (walter.kockenberger@nottingham.ac.uk). Please note that applications sent directly to this email address will not be accepted.


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Recovery of bulk proton magnetization and sensitivity enhancement in ultrafast magic-angle spinning solid-state NMR


A large portion of the magnetization in a CP experiment remains unused after an experiment and different strategies exist to make better use of the proton magnetization. Here the authors show their results of testing 7 different cp schemes. Although not directly related to DNP these techniques are still very valuable to increase the sensitivity of an NMR experiment especially in combination with DNP.



Demers, J.P., V. Vijayan, and A. Lange, Recovery of bulk proton magnetization and sensitivity enhancement in ultrafast magic-angle spinning solid-state NMR. J Phys Chem B, 2015. 119(7): p. 2908-20.


The sensitivity of solid-state NMR experiments is limited by the proton magnetization recovery delay and by the duty cycle of the instrument. Ultrafast magic-angle spinning (MAS) can improve the duty cycle by employing experiments with low-power radio frequency (RF) irradiation which reduce RF heating. On the other hand, schemes to reduce the magnetization recovery delay have been proposed for low MAS rates, but the enhancements rely on selective transfers where the bulk of the (1)H magnetization pool does not contribute to the transfer. We demonstrate here that significant sensitivity enhancements for selective and broadband experiments are obtained at ultrafast MAS by preservation and recovery of bulk (1)H magnetization. We used [(13)C, (15)N]-labeled glutamine as a model compound, spinning in a 1.3 mm rotor at a MAS frequency of 65 kHz. Using low-power (1)H RF (13.4 kHz), we obtain efficient (1)H spin locking and (1)H-(13)C decoupling at ultrafast MAS. As a result, large amounts of (1)H magnetization, from 35% to 42% of the initial polarization, are preserved after cross-polarization and decoupling. Restoring this magnetization to the longitudinal axis using a flip-back pulse leads to an enhancement of the sensitivity, an increase ranging from 14% to 21% in the maximal achievable sensitivity regime and from 24% to 50% in the fast pulsing regime, and to a shortening of the optimal recycling delay to 68% of its original duration. The analysis of the recovery and sensitivity curves reveals that the sensitivity gains do not rely on a selective transfer where few protons contribute but rather on careful conservation of bulk (1)H magnetization. This makes our method compatible with broadband experiments and uniformly labeled materials, in contrast to the enhancement schemes proposed for low MAS. We tested seven different cross-polarization schemes and determined that recovery of bulk (1)H magnetization is a general method for sensitivity enhancement. The physical insight gained about the behavior of proton magnetization sharing under spin lock will be helpful to break further sensitivity boundaries, when even higher external magnetic fields and faster spinning rates are employed.

Friday, March 27, 2015

The role of the glassy dynamics and thermal mixing in the dynamic nuclear polarization and relaxation mechanisms of pyruvic acid


Filibian, M., et al., The role of the glassy dynamics and thermal mixing in the dynamic nuclear polarization and relaxation mechanisms of pyruvic acid. Phys Chem Chem Phys, 2014. 16(48): p. 27025-36.


The temperature dependence of (1)H and (13)C nuclear spin-lattice relaxation rate 1/T1 has been studied in the 1.6-4.2 K temperature range in pure pyruvic acid and in pyruvic acid containing trityl radicals at a concentration of 15 mM. The temperature dependence of 1/T1 is found to follow a quadratic power law for both nuclei in the two samples. Remarkably the same temperature dependence is displayed also by the electron spin-lattice relaxation rate 1/T1e in the sample containing radicals. These results are explained by considering the effect of the structural dynamics on the relaxation rates in pyruvic acid. Dynamic nuclear polarization experiments show that below 4 K the (13)C build up rate scales with 1/T1e, in analogy to (13)C 1/T1 and consistently with a thermal mixing scenario where all the electrons are collectively involved in the dynamic nuclear polarization process and the nuclear spin reservoir is in good thermal contact with the electron spin system.

Wednesday, March 25, 2015

Insights into the catalytic activity of nitridated fibrous silica (KCC-1) nanocatalysts from (15) N and (29) Si NMR spectroscopy enhanced by dynamic nuclear polarization


Lilly Thankamony, A.S., et al., Insights into the catalytic activity of nitridated fibrous silica (KCC-1) nanocatalysts from (15) N and (29) Si NMR spectroscopy enhanced by dynamic nuclear polarization. Angew Chem Int Ed Engl, 2015. 54(7): p. 2190-3.


Fibrous nanosilica (KCC-1) oxynitrides are promising solid-base catalysts. Paradoxically, when their nitrogen content increases, their catalytic activity decreases. This counterintuitive observation is explained here for the first time using (15) N-solid-state NMR spectroscopy enhanced by dynamic nuclear polarization.

Monday, March 23, 2015

Effects of the electron polarization on dynamic nuclear polarization in solids


Hovav, Y., et al., Effects of the electron polarization on dynamic nuclear polarization in solids. Phys Chem Chem Phys, 2015. 17(8): p. 6053-65.


Dynamic Nuclear Polarization (DNP) experiments on solid dielectrics can be described in terms of the Solid Effect (SE) and Cross Effect (CE) mechanisms. These mechanisms are best understood by following the spin dynamics in electron-nuclear and electron-electron-nuclear model systems, respectively. Recently it was shown that the frequency swept DNP enhancement profiles can be reconstructed by combining basic SE and CE DNP spectra. However, this analysis did not take into account the role of the electron spectral diffusion (eSD), which can result in a dramatic loss of electron polarization along the EPR line. In this paper we extend the analysis of DNP spectra by including the influence of the eSD process on the enhancement profiles. We show for an electron-electron-nuclear model system that the change in nuclear polarization can be caused by direct MW irradiation on the CE electron transitions, resulting in a direct CE (dCE) enhancement, or by the influence of the eSD process on the spin system, resulting in nuclear enhancements via a process we term the indirect CE (iCE). We next derive the dependence of the basic SE, dCE, and iCE DNP spectra on the electron polarization distribution along the EPR line and on the MW irradiation frequency. The electron polarization can be obtained from ELDOR experiments, using a recent model which describes its temporal evolution in real samples. Finally, DNP and ELDOR spectra, recorded for a 40 mM TEMPOL sample at 10-40 K, are analyzed. It is shown that the iCE is the major mechanism responsible for the bulk nuclear enhancement at all temperatures.

Friday, March 20, 2015

A benzyl alcohol derivative of the BDPA radical for fast dissolution dynamic nuclear polarization NMR spectroscopy


Munoz-Gomez, J.L., et al., A benzyl alcohol derivative of the BDPA radical for fast dissolution dynamic nuclear polarization NMR spectroscopy. Org Biomol Chem, 2015. 13(9): p. 2689-93.


The synthesis, structural characterization and the successful application of a carbon centered radical derived from 1,3-bisdiphenylene-2-phenylallyl (BDPA), its benzyl alcohol derivative (BA-BDPA), as a polarizing agent for Dynamic Nuclear Polarization (DNP) are described. The reported BA-BDPA radical meets all the requirements to become a promising candidate for its use in in vivo DNP-NMR experiments: it is soluble in neat [1-(13)C]pyruvic acid, insoluble in the dissolution transfer solvent and is effective as a polarizing agent in fast dissolution DNP-NMR applications, without the need for using glassing agents. Moreover, it enables a simple but effective in-line radical filtration to obtain hyperpolarized solutions of [1-(13)C]pyruvic acid free of radicals that offers a better polarization performance.

Monday, March 16, 2015

The Development of 460 GHz gyrotrons for 700 MHz DNP-NMR spectroscopy


Idehara, T., et al., The Development of 460 GHz gyrotrons for 700 MHz DNP-NMR spectroscopy. J Infrared Milli Terahz Waves, 2015: p. 1-15.


Two demountable gyrotrons with internal mode converters were developded as sub-THz radiation sources for 700 MHz DNP (Dynamic Nuclear Polarization) enhanced NMR spectroscopy. Experimental study on the DNP-NMR spectroscopy will be carried out in Osaka University, Institute for Protein Research, as a collaboration with FIR UF. Both gyrotrons operate near 460 GHz and the output CW power measured at the end of transmission system made by circular waveguides is typically 20 to 30 watts. One of them named Gyrotron FU CW GVI (we are using “Gyrotron FU CW GO-1” as an official name in Osaka University) is designed to have a special function of high speed frequency modulation δf within 100 MHz band. This will expand excitable band width of ESR and increase the number of electron spins contributing to DNP. The other gyrotron, Gyrotron FU CW GVIA (“Gyrotron FU CW GO-II”) has a function of frequency tunability Δf in the range of wider than 1.5 GHz, which is achieved in steady state by changing magnetic field intensity. This function should be used for adjusting the output frequency at the optimal value to achieve the highest enhancement factor of DNP.

Friday, March 13, 2015

NMR Signatures of the Active Sites in Sn-β Zeolite


Wolf, P., et al., NMR Signatures of the Active Sites in Sn-β Zeolite. Angewandte Chemie, 2014. 126(38): p. 10343-1031. Wolf, P., et al., NMR Signatures of the Active Sites in Sn-β Zeolite. Angewandte Chemie, 2014. 126(38): p. 10343-10347.47. 


Dynamic nuclear polarization surface enhanced NMR (DNP-SENS), Mössbauer spectroscopy, and computational chemistry were combined to obtain structural information on the active-site speciation in Sn-β zeolite. This approach unambiguously shows the presence of framework SnIV-active sites in an octahedral environment, which probably correspond to so-called open and closed sites, respectively (namely, tin bound to three or four siloxy groups of the zeolite framework).

[NMR] Announcement - 9th Alpine Conference on Solid-State NMR

From the Ampere Magnetic Resonance List




Dear colleagues,

Registration and abstract submission for the 9th Alpine Conference are now open. 

This european conference on new concepts and applications in the field of solid-state NMR will be held in Chamonix Mont-Blanc, France, from the 13th to the 17th September 2015.

The scientific committee will be made up of Sharon Ashbrook (St Andrews, UK), Adam Lange (Göttingen, D) and Robert Tycko (Bethesda, MD - chairman).

Young scientists are particularly encouraged to submit abstracts for posters or oral presentations as soon as possible via our conference website. 

We would also like to draw your attention to the fact that a limited number of student stipends are available. 

Visit our web page for details about on-line registration and abstract submission : http://www.alpine-conference.org

The number of places at the conference is limited: register early !

We look forward to seeing you in Chamonix,

Best regards, 
The organizing committee

L. Emsley (Lyon / Lausanne)
S. Caldarelli (Marseille / Gif Sur Yvette)
A. Lesage (Lyon)
M. Bardet (Grenoble)
S. Hediger (Grenoble)
N. Giraud (Orsay)

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[NMR] Postdoctoral Position at New York University (Traaseth lab)

From the Ampere Magnetic Resonance List


Dear Colleagues,

A postdoctoral position is available in the group of Professor Nate Traaseth in the Department of Chemistry at New York University. The laboratory is located in the heart of Manhattan (Greenwich Village) within New York City. Research projects include biomolecular solution and solid-state NMR spectroscopy of integral membrane proteins involved in drug resistance and membrane receptors involved in developmental and neurodegenerative diseases. Additional active areas of research include solid-state NMR pulse sequence development and methods for measuring protein dynamics in lipid bilayers using solid-state NMR. Members of the group have access to the New York Structural Biology Center to carry out solution and solid-state NMR experiments including dynamic nuclear polarization (DNP) as well as a dedicated and state-of-the-art 600 MHz solid-state NMR spectrometer at New York University. Additional information can be found at www.nyu.edu/fas/dept/chemistry/traasethgroup.

Candidates should have a Ph.D. and experience in NMR spectroscopy (solution or solid-state NMR). A CV and 2-3 letters of recommendation should be sent directly to Professor Traaseth (traaseth@nyu.edu).

-- 
Nate Traaseth
Assistant Professor
Chemistry Department
New York University
100 Washington Sq E
New York, NY 10003
212.992.9784
Office: 660 Brown


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Wednesday, March 11, 2015

Sub-second proton imaging of 13C hyperpolarized contrast agents in water


Truong, M.L., et al., Sub-second proton imaging of 13C hyperpolarized contrast agents in water. Contrast Media Mol Imaging, 2014. 9(5): p. 333-41.


Indirect proton detection of (13)C hyperpolarized contrast agents potentially enables greater sensitivity. Presented here is a study of sub-second projection imaging of hyperpolarized (13)C contrast agent addressing the obstacle posed by water suppression for indirect detection in vivo. Sodium acetate phantoms were used to develop and test water suppression and sub-second imaging with frequency-selective RF pulses using spectroscopic and imaging indirect proton detection. A 9.8 mm aqueous solution of (13)C PHIP hyperpolarized 2-hydroxyethyl-(13)C-propionate-d2,3,3 (HEP), <P> ~25% was used for demonstration of indirect proton sub-second imaging detection. Balanced 2D FSSFP (fast steady-state free precession) allowed the recording of proton images with a field of view of 64 x 64 mm(2) and spatial resolution 2 x 2 mm(2) with total acquisition time of less than 0.2 s. In thermally polarized sodium 1-(13)C-acetate, (13) C to (1)H polarization transfer efficiency of 45.1% of the theoretically predicted values was observed in imaging detection corresponding to an 11-fold overall sensitivity improvement compared with direct (13)C FSSFP imaging. (13)C to (1)H polarization transfer efficiency of 27% was observed in imaging detection, corresponding to a 3.25-fold sensitivity improvement compared with direct (13)C FSSFP imaging with hyperpolarized HEP. The range of potential applications and limitations of this sub-second and ultra-sensitive imaging approach are discussed.

Monday, March 9, 2015

A method for dynamic nuclear polarization enhancement of membrane proteins


Smith, A.N., et al., A method for dynamic nuclear polarization enhancement of membrane proteins. Angew Chem Int Ed Engl, 2015. 54(5): p. 1542-6.


Dynamic nuclear polarization (DNP) magic-angle spinning (MAS) solid-state NMR (ssNMR) spectroscopy has the potential to enhance NMR signals by orders of magnitude and to enable NMR characterization of proteins which are inherently dilute, such as membrane proteins. In this work spin-labeled lipid molecules (SL-lipids), when used as polarizing agents, lead to large and relatively homogeneous DNP enhancements throughout the lipid bilayer and to an embedded lung surfactant mimetic peptide, KL4 . Specifically, DNP MAS ssNMR experiments at 600 MHz/395 GHz on KL4 reconstituted in liposomes containing SL-lipids reveal DNP enhancement values over two times larger for KL4 compared to liposome suspensions containing the biradical TOTAPOL. These findings suggest an alternative sample preparation strategy for DNP MAS ssNMR studies of lipid membranes and integral membrane proteins.

Friday, March 6, 2015

Dynamic nuclear polarization of high-density atomic hydrogen in solid mixtures of molecular hydrogen isotopes

If you are interested in this article, you should also have a look at this article by Can et al., describing the Overhauser Effect in insulating solids:


http://blog.bridge12.com/2014/09/overhauser-effects-in-insulating-solids.html




Sheludiakov, S., et al., Dynamic nuclear polarization of high-density atomic hydrogen in solid mixtures of molecular hydrogen isotopes. Phys Rev Lett, 2014. 113(26): p. 265303.


We report on magnetic resonance studies of high-density atomic hydrogen and deuterium in solid hydrogen matrices at temperatures below 1 K. Average concentrations of H atoms approximately 3x10^{19} cm^{-3} are obtained in chemical tunneling reactions of isotope exchange with D atoms. The products of these reactions are closely located pairs of H atoms near D_{2} molecules with strong exchange interactions. We discovered a dynamic nuclear polarization effect on H atoms created by pumping the center of the H electron spin resonance spectrum, similar to the Overhauser effect in metals. Our results indicate that H atoms may be arranged inside molecular matrices at separations equivalent to local concentrations of 2.6x10^{21} cm^{-3}. This opens up a way to build a metallic state of atomic hydrogen at zero pressure.

Wednesday, March 4, 2015

Effective PHIP labeling of bioactive peptides boosts the intensity of the NMR signal


Sauer, G., et al., Effective PHIP labeling of bioactive peptides boosts the intensity of the NMR signal. Angew Chem Int Ed Engl, 2014. 53(47): p. 12941-5.


A series of novel bioactive derivatives of the sunflower trypsin inhibitor-1 (SFTI-1) suitable for hyperpolarization by parahydrogen-induced polarization (PHIP) was developed. The PHIP activity was achieved by labeling with L-propargylglycine, O-propargyl-L-tyrosine, or 4-pentynoic acid. (1) H NMR signal enhancements (SE) of up to a factor of 70 were achieved in aqueous solution. We found that an isolated spatial location of the triple bond within the respective label and its accessibility for the hydrogenation catalyst are essential factors for the degree of signal enhancement.

Monday, March 2, 2015

Radial spectroscopic MRI of hyperpolarized [1-(13) C] pyruvate at 7 tesla


Ramirez, M.S., et al., Radial spectroscopic MRI of hyperpolarized [1-(13) C] pyruvate at 7 tesla. Magn Reson Med, 2014. 72(4): p. 986-95.


PURPOSE: The transient and nonrenewable signal from hyperpolarized metabolites necessitates extensive sequence optimization for encoding spatial, spectral, and dynamic information. In this work, we evaluate the utility of radial single-timepoint and cumulative spectroscopic MRI of hyperpolarized [1-(13) C] pyruvate and its metabolic products at 7 Tesla (T). METHODS: Simulations of radial echo planar spectroscopic imaging (EPSI) and multiband frequency encoding (MBFE) acquisitions were performed to confirm feasibility and evaluate performance for HP (13) C imaging. Corresponding sequences were implemented on a 7T small-animal MRI system, tested in phantom, and demonstrated in a murine model of anaplastic thyroid cancer. RESULTS: MBFE provides excellent spectral separation but is susceptible to blurring and T2 * signal loss inherent to using low readout gradients. The higher readout gradients and more flexible spectral encoding for EPSI result in good spatial resolution and spectral separation. Radial acquisition throughout HP signal evolution offers the flexibility for reconstructing spatial maps of mean metabolite distribution and global dynamic time courses of multiple metabolites. CONCLUSION: Radial EPSI and MBFE acquisitions are well-suited for hyperpolarized (13) C MRI over short and long durations. Advantages to this approach include robustness to nonstationary magnetization, insensitivity to precise acquisition timing, and versatility for reconstructing dynamically acquired spectroscopic data.