Wednesday, September 20, 2017

Measuring Nano- to Microstructures from Relayed Dynamic Nuclear Polarization NMR #DNPNMR


Pinon, A.C., et al., Measuring Nano- to Microstructures from Relayed Dynamic Nuclear Polarization NMR. The Journal of Physical Chemistry C, 2017. 121(29): p. 15993-16005.


We show how dynamic nuclear polarization (DNP) NMR can be used in combination with models for polarization dynamics to determine the domain sizes in complex materials. By selectively doping a source component with radicals and leaving the target undoped, we can measure experimental polarization buildup curves which can be compared with simulations based on heterogeneous distributions of polarization within the sample. The variation of the integrated DNP enhancement as a function of the polarization time is found to be characteristic of the geometry. We demonstrate the method experimentally on four different systems where we successfully determine domain sizes between 200 and 20 000 nm, specifically in powdered histidine hydrochloride monohydrate, pore lengths of mesoporous silica materials, and two domain sizes in two-component polymer film coatings. Additionally, we find that even in the apparently homogeneous frozen solutions used as polarization sources in most DNP experiments, polarization is relayed from protons near the radicals to the bulk of the solution by spin diffusion, which explains the experimentally observed buildup times in these samples.

Monday, September 18, 2017

Unprecedented Carbon Signal Enhancement in Liquid-State NMR Spectroscopy #DNPNMR


Pinter, G. and H. Schwalbe, Unprecedented Carbon Signal Enhancement in Liquid-State NMR Spectroscopy. Angew Chem Int Ed Engl, 2017. 56(29): p. 8332-8334.


We shall overcome: As a result of efforts to overcome the sensitivity challenge of liquid-state NMR spectroscopy, a thousand-fold signal enhancement was achieved by dynamic nuclear polarization (DNP) for 13 C signals at high magnetic field (3.4 T) and room temperature, thereby exceeding the predicted limitations of high-field liquid-state in situ DNP.

Friday, September 15, 2017


Barskiy, D.A., et al., NMR Hyperpolarization Techniques of Gases. Chemistry, 2017. 23(4): p. 725-751.


Nuclear spin polarization can be significantly increased through the process of hyperpolarization, leading to an increase in the sensitivity of nuclear magnetic resonance (NMR) experiments by 4-8 orders of magnitude. Hyperpolarized gases, unlike liquids and solids, can often be readily separated and purified from the compounds used to mediate the hyperpolarization processes. These pure hyperpolarized gases enabled many novel MRI applications including the visualization of void spaces, imaging of lung function, and remote detection. Additionally, hyperpolarized gases can be dissolved in liquids and can be used as sensitive molecular probes and reporters. This Minireview covers the fundamentals of the preparation of hyperpolarized gases and focuses on selected applications of interest to biomedicine and materials science.

Thursday, September 14, 2017

[NMR] Nobel Prize winner Nico Bloembergen passed away at age 97


From the Ampere Magnetic Resonance List:

Dear colleagues,

Last week, Nobel laureate Professor Nicolaas Bloembergen, a pioneer in the field of NMR and laser spectroscopy passed away at age of 97. As an undergraduate Bloembergen studied Physics at Utrecht University from 1938 to 1943 and received his PhD in Physics from Leiden University with C.J. Gorter in 1948 on the topic of Nuclear Magnetic Relaxation. His thesis resulted in the famous BPP (Bloembergen, Purcell and Pound) paper which still serves as a point of departure for understanding many NMR relaxation experiments. In 1973 he returned to Leiden and occupied the Lorentz Chair in Physics. In 1981, he was awarded the Nobel Prize in Physics for his work in coherent optics. In 2001 in honour of his achievements, the NMR group at Utrecht University named their laboratory the Bloembergen Building.

For further information on a true scientific giant, please look out for an obituary written by C. Luchinat, R. Boelens, and R. Kaptein that will appear on the Ampere website and in the Ampere newsletter soon.

Also, please see, for example:

Best wishes,
Marc Baldus



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Wednesday, September 13, 2017

Single-scan 13C diffusion-ordered NMR spectroscopy of DNP-hyperpolarised substrates #DNPNMR


Guduff, L., et al., Single-scan 13C diffusion-ordered NMR spectroscopy of DNP-hyperpolarised substrates. Chemistry, 2017: p. n/a-n/a.


Diffusion-ordered NMR spectroscopy (DOSY) is a powerful approach for the analysis of molecular mixtures, yet its application range is limited by the relatively low sensitivity of NMR. We show here that spectrally resolved 13C DOSY data can be collected, in a single scan, for substrates hyperpolarised by dissolution dynamic nuclear polarisation (D-DNP), which provides signal enhancements of several orders of magnitude. For this we use a convection-compensation pulse scheme, which we also analyse by numerical simulation. The proposed method further allows the acquisition of several consecutive DOSY spectra in a single D-DNP experiment.

Monday, September 11, 2017

Overhauser-enhanced magnetic resonance elastography


Salameh, N., et al., Overhauser-enhanced magnetic resonance elastography. NMR in Biomedicine, 2016. 29(5): p. 607-613.


Magnetic resonance elastography (MRE) is a powerful technique to assess the mechanical properties of living tissue. However, it suffers from reduced sensitivity in regions with short T2 and T2* such as in tissue with high concentrations of paramagnetic iron, or in regions surrounding implanted devices. In this work, we exploit the longer T2* attainable at ultra-low magnetic fields in combination with Overhauser dynamic nuclear polarization (DNP) to enable rapid MRE at 0.0065 T. A 3D balanced steady-state free precession based MRE sequence with undersampling and fractional encoding was implemented on a 0.0065 T MRI scanner. A custom-built RF coil for DNP and a programmable vibration system for elastography were developed. Displacement fields and stiffness maps were reconstructed from data recorded in a polyvinyl alcohol gel phantom loaded with stable nitroxide radicals. A DNP enhancement of 25 was achieved during the MRE sequence, allowing the acquisition of 3D Overhauser-enhanced MRE (OMRE) images with (1.5 × 2.7 × 9) mm3 resolution over eight temporal steps and 11 slices in 6 minutes. In conclusion, OMRE at ultra-low magnetic field can be used to detect mechanical waves over short acquisition times. This new modality shows promise to broaden the scope of conventional MRE applications, and may extend the utility of low-cost, portable MRI systems to detect elasticity changes in patients with implanted devices or iron overload. Copyright © 2016 John Wiley & Sons, Ltd.

[NMR] Faculty position at New York University

From the Ampere Magnetic Resonance List



Dear Colleagues,

The Department of Chemistry at New York University is soliciting applications for faculty positions in Chemistry. One of the emphasis areas is biophysical chemistry, which may include NMR or EPR. The deadline for the application is Sep 29, 2017. The full search advertisement is copied and pasted below, and can also be found via the link: http://as.nyu.edu/chemistry/recruitment.html


best wishes,
Nate


----

ASSISTANT PROFESSOR

Department of Chemistry
Arts and Science
New York University

The Department of Chemistry at New York University (NYU) invites applications for several tenure-track faculty positions in all areas of Chemistry and Biochemistry, subject to final administrative approval. Successful candidates must have a Ph.D in chemistry or related field and demonstrate the potential to do pioneering research and to teach effectively at the undergraduate and graduate levels. The positions are anticipated to be at the junior level, although exceptional senior level candidates will be considered. The Department of Chemistry is continuing a significant growth plan, including the creation of the Biomedical Chemistry Institute, the Molecular Design Institute, and the addition of numerous senior and junior faculty members. Interested faculty are able to participate in significant interdisciplinary programs within the Washington Square campus, as well as with NYU’s engineering and medical schools, and scholarly activities at its campuses in Shanghai and Abu Dhabi.

Candidates should submit a curriculum vitae, a detailed description of research plans and interests, and a statement of teaching experience and interests. The application should include three letters of recommendation. Review of complete applications will begin September 29, 2017. The anticipated start date is September 1, 2018. Please submit applications through our web portal using the following link: apply.interfolio.com/43972

The Faculty of Arts and Science at NYU is at the heart of a leading research university that spans the globe. We seek scholars of the highest caliber, who embody the diversity of the United States as well as the global society in which we live. We strongly encourage applications from women, racial and ethnic minorities, and other individuals who are under-represented in the profession, across color, creed, race, ethnic and national origin, physical ability, gender and sexual identity, or any other legally protected basis. NYU affirms the value of differing perspectives on the world as we strive to build the strongest possible university with the widest reach. To learn more about the FAS commitment to diversity, equality and inclusion, please read here.

EOE/Affirmative Action/Minorities/Females/Vet/Disabled/Sexual Orientation/Gender Identity

--

Nate Traaseth | Associate Professor of Chemistry, NYU | traaseth@nyu.edu | 212-992-9784

lab website | full contact info


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Friday, September 8, 2017

Near-unity nuclear polarization with an open-source 129Xe hyperpolarizer for NMR and MRI


Already a bit older this article, but still a good read.


Nikolaou, P., et al., Near-unity nuclear polarization with an open-source 129Xe hyperpolarizer for NMR and MRI. Proc. Nat. Aca. Sci. USA, 2013. 110(35): p. 14150-14155.


The exquisite NMR spectral sensitivity and negligible reactivity of hyperpolarized xenon-129 (HP129Xe) make it attractive for a number of magnetic resonance applications; moreover, HP129Xe embodies an alternative to rare and nonrenewable 3He. However, the ability to reliably and inexpensively produce large quantities of HP129Xe with sufficiently high 129Xe nuclear spin polarization (PXe) remains a significant challenge—particularly at high Xe densities. We present results from our “open-source” large-scale (∼1 L/h) 129Xe polarizer for clinical, preclinical, and materials NMR and MRI research. Automated and composed mostly of off-the-shelf components, this “hyperpolarizer” is designed to be readily implementable in other laboratories. The device runs with high resonant photon flux (up to 200 W at the Rb D1 line) in the xenon-rich regime (up to 1,800 torr Xe in 500 cc) in either single-batch or stopped-flow mode, negating in part the usual requirement of Xe cryocollection. Excellent agreement is observed among four independent methods used to measure spin polarization. In-cell PXe values of ∼90%, ∼57%, ∼50%, and ∼30% have been measured for Xe loadings of ∼300, ∼500, ∼760, and ∼1,570 torr, respectively. PXe values of ∼41% and ∼28% (with ∼760 and ∼1,545 torr Xe loadings) have been measured after transfer to Tedlar bags and transport to a clinical 3 T scanner for MR imaging, including demonstration of lung MRI with a healthy human subject. Long “in-bag” 129Xe polarization decay times have been measured (T1 ∼38 min and ∼5.9 h at ∼1.5 mT and 3 T, respectively)—more than sufficient for a variety of applications.

Thursday, September 7, 2017

PhD/Postdoc positions, available on DNP/MAS NMR and multi-frequency EPR

The original posting can be found here:



The University of Konstanz with its "Institutional Strategy to promote Top-Level Research" has been receiving continuous funding since 2007 within the framework of the Excellence Initiative by the German Federal and State Governments.

PhD/Postdoc positions available on DNP/MAS NMR and multi-frequency EPR (67 % EG 13 TV-L)

The positions are to be filled as soon as possible and initially limited for two years. 

We are a newly established research group in the Chemistry Department. Our research encompasses the development of magnetic resonance spectroscopy, particularly dynamic nuclear polarization (DNP) / magic-angle spinning (MAS) NMR and multi-frequency electron-paramagnetic resonance (EPR) and their application in structural biology, enzymology, and catalysis. 

Possible research projects are:

To investigate if and how the high polarization generated in the photo-excited triplet states of certain chro-mophores can be used for DNP/MAS NMR. 

The development of "DNP pulse sequences". This project has an experimental component, as well as a theoretical component. 

The application and development of multi-frequency EPR spectroscopy to study enzymatic reaction mechanisms.

The exact topic of the candidates research can be agreed on in consultation and will depend on the candidates background and interests. 

You have a strong interest in basic science, particularly in physical chemistry and spectroscopy. You are highly motivated and willing to work on solving complex, long-term problems. In your research, you are able to make the combination between theory and experiment. You have a MSc degree in Physics, Chemistry or a related field. For postdocs a PhD in MAS NMR is a plus. 

The University of Konstanz encourages disabled persons to apply. They will be given preference if appropriately qualified (contact + 49 (0) 7531 / 88 - 4016). 

The University of Konstanz is committed to further the compatibility of work and family life. 

The University of Konstanz is an equal opportunity employer that tries to increase the number of women in research and teaching. 

The University of Konstanz offers a ,,Dual Career Couples Program". Information can be obtained from: www.uni-konstanz.de/dcc

Applicants should send a cover letter, CV, and contact information of two references before Oct 15, 2017 to Dr. Guinevere Mathies. E-mail: guinevere.mathies [at] uni-konstanz[.]de. 
Visit also our website: http://chemie.uni.kn/mathies . 

Bewerbungsende: 15.10.2017

Wednesday, September 6, 2017

Frozen Acrylamide Gels as Dynamic Nuclear Polarization Matrices #DNPNMR


Viger-Gravel, J., et al., Frozen Acrylamide Gels as Dynamic Nuclear Polarization Matrices. Angewandte Chemie, 2017. 129(30): p. 8852-8856.


Aqueous acrylamide gels can be used to provide dynamic nuclear polarization (DNP) NMR signal enhancements of around 200 at 9.4 T and 100 K. The enhancements are shown to increase with crosslinker concentration and low concentrations of the AMUPol biradical. This DNP matrix can be used in situations where conventional incipient wetness methods fail, such as to obtain DNP surface enhanced NMR spectra from inorganic nanoparticles. In particular, we obtain 113Cd spectra from CdTe-COOH NPs in minutes. The spectra clearly indicate a highly disordered cadmium-rich surface.

Tuesday, September 5, 2017

[NMR] Postdoctoral position in chromatin structural biology at UC, San Diego

The Debelouchina lab at the University of California, San Diego is looking for a motivated postdoctoral researcher to join our growing team. Our work combines NMR spectroscopy tools with chemical and cell biology techniques to study chromatin and gene regulation. This position will provide the candidate with the opportunity to apply and/or learn solid-state and solution NMR methods, protein and peptide synthesis, protein biochemistry, as well as cell biology techniques. Candidates must hold a Ph.D. in chemistry, biochemistry, biophysics or a related discipline. Extensive background in biomolecular NMR or NMR method development is not required but will be particularly helpful.

The University of California, San Diego has outstanding resources for high-field NMR spectroscopy, including 900 MHz, 750 MHz, 700 MHz and 500 MHz solid-state NMR spectrometers equipped with MAS and static probes, as well as solution spectrometers operating at 800 MHz, 600 MHz and 500 MHz dedicated to biomolecular NMR applications. The large UCSD scientific community and several research institutes nearby (The Salk Institute for Biological Studies, the Scripps Research Institute and the Sanford Burnham Prebys Medical Discovery Institute) provide a vast network and potential for collaborations and scientific exchange. In addition to a vibrant scientific environment, San Diego also offers beautiful weather all year round and many opportunities for nature and ocean exploration.

For more information, interested candidates should contact Dr. Debelouchina directly at gdebelouchina@ucsd.edu.

Representative publications:

Debelouchina GT, Gerecht K, Muir TW (2017). Ubiquitin utilizes an acidic surface patch to alter chromatin structure. Nat. Chem. Biol. 13, 105-110.

Debelouchina GT and Muir TW (2017). A Molecular Engineering Toolbox for the Structural Biologist. Q. Rev. Biophys. 50, e7.

Debelouchina GT, Bayro MJ, Fitzpatrick AWP, Ladizhansky V, Colvin MT, Caporini MA, Jaroniec CP, Bajaj VS, Rosay M, MacPhee C, Vendruscolo M, Maas WE, Dobson CM, Griffin RG (2013). Higher Order Amyloid Fibril Structure by MAS NMR and DNP Spectroscopy. J. Am. Chem. Soc. 135, 19237-47. 

___________________________
Galia Debelouchina, Ph.D.
Assistant Professor
Department of Chemistry and Biochemistry
University of California, San Diego
9500 Gilman Drive
La Jolla, CA 92093

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Monday, September 4, 2017

Hyperpolarization of nitrogen-15 nuclei by cross polarization and dissolution dynamic nuclear polarization


Milani, J., et al., Hyperpolarization of nitrogen-15 nuclei by cross polarization and dissolution dynamic nuclear polarization. Review of Scientific Instruments, 2017. 88(1): p. 015109.


Dynamic Nuclear Polarization (DNP) is often achieved by the direct transfer of polarization from electrons to nuclei such as 13C, induced by microwavesaturation of the wings of narrow EPR lines of radicals like trityl. In the indirectapproach on the other hand, DNP is used to transfer the polarization from the electrons of radicals such as nitroxides that have broad EPR lines to nuclear spins I = 1H, followed by cross-polarization (CP) from I = 1H to S = 13C or other nuclei with low gyromagnetic ratios. This approach is particularly attractive for S = 15N, since direct DNP yields modest polarizations P(15N) < 4% with build-up times that can be as long as τDNP(15N) > 2 h. In this paper, we show that CP from 1H to 15N at 1.2 K can yield P(15N) = 25% with τCP-DNP(15N) = 10–15 min. After rapid dissolution and transfer to a solution-state NMR spectrometer, a polarizationP(15N) = 20% was observed at 300 K. The longitudinal relaxation times in solution can be as long as T1(15N) > 800 s in favorable cases.





Friday, September 1, 2017

Arbitrary waveform modulated pulse EPR at 200GHz


Kaminker, I., R. Barnes, and S. Han, Arbitrary waveform modulated pulse EPR at 200GHz. J Magn Reson, 2017. 279: p. 81-90.


We report here on the implementation of arbitrary waveform generation (AWG) capabilities at approximately 200GHz into an Electron Paramagnetic Resonance (EPR) and Dynamic Nuclear Polarization (DNP) instrument platform operating at 7T. This is achieved with the integration of a 1GHz, 2 channel, digital to analog converter (DAC) board that enables the generation of coherent arbitrary waveforms at Ku-band frequencies with 1ns resolution into an existing architecture of a solid state amplifier multiplier chain (AMC). This allows for the generation of arbitrary phase- and amplitude-modulated waveforms at 200GHz with >150mW power. We find that the non-linearity of the AMC poses significant difficulties in generating amplitude-modulated pulses at 200GHz. We demonstrate that in the power-limited regime of omega1<1MHz phase-modulated pulses were sufficient to achieve significant improvements in broadband (>10MHz) spin manipulation in incoherent (inversion), as well as coherent (echo formation) experiments. Highlights include the improvement by one order of magnitude in inversion bandwidth compared to that of conventional rectangular pulses, as well as a factor of two in improvement in the refocused echo intensity at 200GHz.

Wednesday, August 30, 2017

Communication: Dissolution DNP reveals a long-lived deuterium spin state imbalance in methyl groups #DNPNMR


Jhajharia, A., et al., Communication: Dissolution DNP reveals a long-lived deuterium spin state imbalance in methyl groups. J Chem Phys, 2017. 146(4): p. 041101.


We report the generation and observation of long-lived spin states in deuterated methyl groups by dissolution DNP. These states are based on population imbalances between manifolds of spin states corresponding to irreducible representations of the C3v point group and feature strongly dampened quadrupolar relaxation. Their lifetime depends on the activation energies of methyl group rotation. With dissolution DNP, we can reduce the deuterium relaxation rate by a factor up to 20, thereby extending the experimentally available time window. The intrinsic limitation of NMR spectroscopy of quadrupolar spins by short relaxation times can thus be alleviated.

Monday, August 28, 2017

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


Ni, Q.Z., et al., Peptide and Protein Dynamics and Low-Temperature/DNP Magic Angle Spinning NMR. The Journal of Physical Chemistry B, 2017. 121(19): p. 4997-5006.


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

Friday, August 25, 2017

Frequency-Swept Integrated Solid Effect #DNPNMR


Can, T.V., et al., Frequency-Swept Integrated Solid Effect. Angew Chem Int Ed Engl, 2017. 56(24): p. 6744-6748.


The efficiency of continuous wave dynamic nuclear polarization (DNP) experiments decreases at the high magnetic fields used in contemporary high-resolution NMR applications. To recover the expected signal enhancements from DNP, we explored time domain experiments such as NOVEL which matches the electron Rabi frequency to the nuclear Larmor frequency to mediate polarization transfer. However, satisfying this matching condition at high frequencies is technically demanding. As an alternative we report here frequency-swept integrated solid effect (FS-ISE) experiments that allow low power sweeps of the exciting microwave frequencies to constructively integrate the negative and positive polarizations of the solid effect, thereby producing a polarization efficiency comparable to (+/-10 % difference) NOVEL. Finally, the microwave frequency modulation results in field profiles that exhibit new features that we coin the "stretched" solid effect.

Wednesday, August 23, 2017

Depolarization of nuclear spin polarized 129Xe gas by dark rubidium during spin-exchange optical pumping


Antonacci, M.A., et al., Depolarization of nuclear spin polarized 129Xe gas by dark rubidium during spin-exchange optical pumping. J Magn Reson, 2017. 279: p. 60-67.


Continuous-flow spin-exchange optical pumping (SEOP) continues to serve as the most widespread method of polarizing 129Xe for magnetic resonance experiments. Unfortunately, continuous-flow SEOP still suffers from as-yet unidentified inefficiencies that prevent the production of large volumes of xenon with a nuclear spin polarization close to theoretically calculated values. In this work we use a combination of ultra-low field nuclear magnetic resonance spectroscopy and atomic absorption spectroscopy (AAS) measurements to study the effects of dark Rb vapor on hyperpolarized 129Xe in situ during continuous-flow SEOP. We find that dark Rb vapor in the optical cell outlet has negligible impact on the final 129Xe polarization at typical experimental conditions, but can become significant at higher oven temperatures and lower flow rates. Additionally, in the AAS spectra we also look for a signature of paramagnetic Rb clusters, previously identified as a source of xenon depolarization and a cause for SEOP inefficiency, for which we are able to set an upper limit of 8.3x1015 Rb dimers per cm3.

Monday, August 21, 2017

Dynamic nuclear polarisation by thermal mixing: quantum theory and macroscopic simulations #DNPNMR


Karabanov, A., et al., Dynamic nuclear polarisation by thermal mixing: quantum theory and macroscopic simulations. Phys. Chem. Chem. Phys., 2016. 18(43): p. 30093-30104.


A theory of dynamic nuclear polarisation (DNP) by thermal mixing is suggested based on purely quantum considerations. A minimal 6-level microscopic model is developed to test the theory and link it to the well-known thermodynamic model. Optimal conditions for the nuclear polarization enhancement and effects of inhomogeneous broadening of the electron resonance are discussed. Macroscopic simulations of nuclear polarization spectra displaying good agreement with experiments, involving BDPA and trityl free radicals, are presented.

Friday, August 18, 2017

Free Radical Imaging Using In Vivo Dynamic Nuclear Polarization-MRI #DNPNMR #ODNP


Utsumi, H. and F. Hyodo, Free Radical Imaging Using In Vivo Dynamic Nuclear Polarization-MRI. Methods Enzymol, 2015. 564: p. 553-71.


Redox reactions that generate free radical intermediates are essential to metabolic processes, and their intermediates can produce reactive oxygen species, which may promote diseases related to oxidative stress. The development of an in vivo electron spin resonance (ESR) spectrometer and its imaging enables us noninvasive and direct measurement of in vivo free radical reactions in living organisms. The dynamic nuclear polarization magnetic resonance imaging (DNP-MRI), also called PEDRI or OMRI, is also a new imaging method for observing free radical species in vivo. The spatiotemporal resolution of free radical imaging with DNP-MRI is comparable with that in MRI, and each of the radical species can be distinguished in the spectroscopic images by changing the frequency or magnetic field of ESR irradiation. Several kinds of stable nitroxyl radicals were used as spin probes to detect in vivo redox reactions. The signal decay of nitroxyl probes, which is determined with in vivo DNP-MRI, reflects the redox status under oxidative stress, and the signal decay is suppressed by prior administration of antioxidants. In addition, DNP-MRI can also visualize various intermediate free radicals from the intrinsic redox molecules. This noninvasive method, in vivo DNP-MRI, could become a useful tool for investigating the mechanism of oxidative injuries in animal disease models and the in vivo effects of antioxidant drugs.

Wednesday, August 16, 2017

Simultaneous and spectroscopic redox molecular imaging of multiple free radical intermediates using dynamic nuclear polarization-magnetic resonance imaging #DNPNMR


Hyodo, F., et al., Simultaneous and spectroscopic redox molecular imaging of multiple free radical intermediates using dynamic nuclear polarization-magnetic resonance imaging. Anal Chem, 2014. 86(15): p. 7234-8.


Redox reactions that generate free radical intermediates are essential to metabolic processes. However, their intermediates can produce reactive oxygen species, which may promote diseases related to oxidative stress. We report here the use of dynamic nuclear polarization-magnetic resonance imaging (DNP-MRI) to conduct redox molecular imaging. Using DNP-MRI, we obtained simultaneous images of free radical intermediates generated from the coenzyme Q10 (CoQ10), flavin mononucleotide (FMN), and flavin adenine dinucleotide (FAD) involved in the mitochondrial electron transport chain as well as the radicals derived from vitamins E and K1. Each of these free radicals was imaged in real time in a phantom comprising a mixture of free radicals localized in either lipophilic or aqueous environments. Changing the frequency of electron spin resonance (ESR) irradiation also allowed each of the radical species to be distinguished in the spectroscopic images. This study is the first to report the spectroscopic DNP-MRI imaging of free radical intermediates that are derived from endogenous species involved in metabolic processes.

Monday, August 14, 2017

EPR Spectroscopy of Nitroxide Spin Probes #EPR #DNPNMR


Nitroxide spin labels are extensively used in EPR for distance measurements and many polarizing agents are based on nitroxides. More recently they are also used in Overhauser DNP measurements (ODNP) to study surface hydration dynamics of larger (membrane) proteins. Although the article is already a bit older, it is a nice review of spin labels and their use in EPR spectroscopy.


Bordignon, E., EPR Spectroscopy of Nitroxide Spin Probes, in eMagRes. 2017, John Wiley & Sons, Ltd. p. 235-254.


In this article, we will introduce the main chemical and spectroscopic properties of nitroxides. These paramagnetic non-endogenous probes have been widely used in EPR spectroscopy in the last decade due to their high stability and simple spectral fingerprint, which provides a wealth of qualitative and quantitative information about their microscopic environment under almost unrestricted experimental conditions. Nitroxides can be covalently or noncovalently introduced into a variety of different materials to monitor viscosity, local dynamics, pH, polarity, H-bond networks, transition temperatures, and distances toward other nitroxide probes. In general, these small probes minimally perturb the system under investigation, and being the unique paramagnetic centers in an otherwise diamagnetic sample, they provide unequivocal information. Here we will focus on their exquisite sensitivity to report molecular motions within defined ‘EPR timescales’ and spin-spin interactions via changes in their spectral lineshape. Additionally, we will discuss some methods to monitor polarity and formation of H-bonds in their microenvironment.

Friday, August 11, 2017

Electron Decoupling with Dynamic Nuclear Polarization in Rotating Solids #DNPNMR


Saliba, E.P., et al., Electron Decoupling with Dynamic Nuclear Polarization in Rotating Solids. J Am Chem Soc, 2017. 139(18): p. 6310-6313.


Dynamic nuclear polarization (DNP) can enhance NMR sensitivity by orders of magnitude by transferring spin polarization from electron paramagnetic resonance (EPR) to NMR. However, paramagnetic DNP polarizing agents can have deleterious effects on NMR signals. Electron spin decoupling can mitigate these paramagnetic relaxation effects. We demonstrate electron decoupling experiments in conjunction with DNP and magic-angle-spinning NMR spectroscopy. Following a DNP and spin diffusion period, the microwave irradiation frequency is quickly tuned on-resonance with electrons on the DNP polarizing agent. The electron decoupling performance shows a strong dependence on the microwave frequency and DNP polarization time. Microwave frequency sweeps through the EPR line shape are shown as a time domain strategy to significantly improve electron decoupling. For 13C spins on biomolecules frozen in a glassy matrix, electron decoupling reduces the line widths by 11% (47 Hz) and increases the intensity by 14%.

Thursday, August 10, 2017

[NMR] Training School on Principles and Applications of Dissolution DNP, Nov 13-17, 2017, Copenhagen


Dear all,
The registration deadline for the training school, Principles and Applications of Dissolution DNP, has been extended to Sep 1.

The training school takes place at the Center for Hyperpolarization in Magnetic Resonance, at the Technical University of Denmark, Kgs Lyngby, Denmark from Nov 13-17, 2017.

We have three fantastic external lecturers signed up for the teaching, Tom Wenckebach, Matthew Merritt and Arnaud Comment, together with the faculty of the group. The school covers DNP theory, relaxation, kinetic modelling, sample preparation, polarizer instrumentation and operation, acquisition strategies as well as in vitro and in vivo applications. There will be plenty of hands-on exercises and in-depth discussion in small groups.

More details of the workshop is available from the website: http://www.hypermag.dtu.dk/Research/Dissolution-DNP-Course.

Please forward this email on to anyone who may be interested.

Thanks, and best regards, Jan

Jan Henrik Ardenkjaer-Larsen
Professor, Center Leader
Center for Magnetic Resonance
Technical University of Denmark
Department of Electrical Engineering
Ørsted Plads, bldg. 349, room 126
DK-2800 Kgs Lyngby
Phone +45 45253918

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Wednesday, August 9, 2017

Role of chiral quantum Hall edge states in nuclear spin polarization


Yang, K., et al., Role of chiral quantum Hall edge states in nuclear spin polarization. Nat Commun, 2017. 8: p. 15084.


Resistively detected NMR (RDNMR) based on dynamic nuclear polarization (DNP) in a quantum Hall ferromagnet (QHF) is a highly sensitive method for the discovery of fascinating quantum Hall phases; however, the mechanism of this DNP and, in particular, the role of quantum Hall edge states in it are unclear. Here we demonstrate the important but previously unrecognized effect of chiral edge modes on the nuclear spin polarization. A side-by-side comparison of the RDNMR signals from Hall bar and Corbino disk configurations allows us to distinguish the contributions of bulk and edge states to DNP in QHF. The unidirectional current flow along chiral edge states makes the polarization robust to thermal fluctuations at high temperatures and makes it possible to observe a reciprocity principle of the RDNMR response. These findings help us better understand complex NMR responses in QHF, which has important implications for the development of RDNMR techniques.

Monday, August 7, 2017

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


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


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

Wednesday, August 2, 2017

Transmembrane Interactions of Full-length Mammalian Bitopic Cytochrome-P450-Cytochrome-b5 Complex in Lipid Bilayers Revealed by Sensitivity-Enhanced Dynamic Nuclear Polarization Solid-state NMR Spectroscopy #DNPNMR


Yamamoto, K., et al., Transmembrane Interactions of Full-length Mammalian Bitopic Cytochrome-P450-Cytochrome-b5 Complex in Lipid Bilayers Revealed by Sensitivity-Enhanced Dynamic Nuclear Polarization Solid-state NMR Spectroscopy. Sci Rep, 2017. 7(1): p. 4116.


The dynamic protein-protein and protein-ligand interactions of integral bitopic membrane proteins with a single membrane-spanning helix play a plethora of vital roles in the cellular processes associated with human health and diseases, including signaling and enzymatic catalysis. While an increasing number of high-resolution structural studies of membrane proteins have successfully manifested an in-depth understanding of their biological functions, intact membrane-bound bitopic protein-protein complexes pose tremendous challenges for structural studies by crystallography or solution NMR spectroscopy. Therefore, there is a growing interest in developing approaches to investigate the functional interactions of bitopic membrane proteins embedded in lipid bilayers at atomic-level. Here we demonstrate the feasibility of dynamic nuclear polarization (DNP) magic-angle-spinning NMR techniques, along with a judiciously designed stable isotope labeling scheme, to measure atomistic-resolution transmembrane-transmembrane interactions of full-length mammalian ~72-kDa cytochrome P450-cytochrome b5 complex in lipid bilayers. Additionally, the DNP sensitivity-enhanced two-dimensional 13C/13C chemical shift correlations via proton driven spin diffusion provided distance constraints to characterize protein-lipid interactions and revealed the transmembrane topology of cytochrome b5. The results reported in this study would pave ways for high-resolution structural and topological investigations of membrane-bound full-length bitopic protein complexes under physiological conditions.

Monday, July 31, 2017

Continuous-flow DNP polarizer for MRI applications at 1.5 T


Denysenkov, V., et al., Continuous-flow DNP polarizer for MRI applications at 1.5 T. 2017. 7: p. 44010.


Here we describe a new hyperpolarization approach for magnetic resonance imaging applications at 1.5 T. Proton signal enhancements of more than 20 were achieved with a newly designed multimode microwave resonator situated inside the bore of the imager and used for Overhauser dynamic nuclear polarization of the water proton signal. Different from other approaches in our setup the hyperpolarization is achieved continuously by liquid water flowing through the polarizer under continuous microwave excitation. With an available flow rate of up to 1.5 ml/min, which should be high enough for DNP MR angiography applications in small animals like mice and rats. The hyperpolarized liquid cooled to physiological temperature can be routed by a mechanical switch to a quartz capillary for injection into the blood vessels of the target object. This new approach allows hyperpolarization of protons without the need of an additional magnet and avoids the losses arising from the transfer of the hyperpolarized solution between magnets. The signal-to-noise improvement of this method is demonstrated on two- and three-dimensional phantoms of blood vessels.

Friday, July 28, 2017

Thermal annihilation of photo-induced radicals following dynamic nuclear polarization to produce transportable frozen hyperpolarized 13C-substrates


Capozzi, A., et al., Thermal annihilation of photo-induced radicals following dynamic nuclear polarization to produce transportable frozen hyperpolarized 13C-substrates. 2017. 8: p. 15757.


Hyperpolarization via dynamic nuclear polarization (DNP) is pivotal for boosting magnetic resonance imaging (MRI) sensitivity and dissolution DNP can be used to perform in vivo real-time 13C MRI. The type of applications is however limited by the relatively fast decay time of the hyperpolarized spin state together with the constraint of having to polarize the 13C spins in a dedicated apparatus nearby but separated from the MRI magnet. We herein demonstrate that by polarizing 13C with photo-induced radicals, which can be subsequently annihilated using a thermalization process that maintains the sample temperature below its melting point, hyperpolarized 13C-substrates can be extracted from the DNP apparatus in the solid form, while maintaining the enhanced 13C polarization. The melting procedure necessary to transform the frozen solid into an injectable solution containing the hyperpolarized 13C-substrates can therefore be performed ex situ, up to several hours after extraction and storage of the polarized solid.

Wednesday, July 26, 2017

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



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


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

[NMR] PhD position at the University of Warwick (September 2017 start)



Exploiting Very-Fast Magic-Angle Spinning NMR: Enabling New Applications to Pharmaceutical Chemistry and Life Sciences


A PhD position in The Molecular Analytical Science Centre for Doctoral Training at the University of Warwick is open for start in September 2017. After successfully completing 6 months of MSc modules, you will carry out a research project (further 3.5 years funding) in the Magnetic Resonance Laboratory under the supervision of Steven P. Brown (Physics) and Józef R. Lewandowski (Chemistry). Working together with Bruker, you will use state-of-the-art very-fast magic-angle spinning technologies in projects that develop and apply advanced solid-state NMR pulse sequences to pharmaceuticals and proteins. You should be from the UK or another European Union country. You need to have a first degree in a relevant scientific discipline (e.g., Physics, Chemistry) and be enthusiastic to work on a project that combines experiment with computer simulation and show a keenness to understand the underlying quantum phenomena that enables NMR to be applied to these important application areas.

For further details, please contact Steven Brown (S.P.Brown@warwick.ac.uk) or Jozef Lewandowski (J.R.Lewandowski@warwick.ac.uk)


Steven Brown
Department of Physics
University of Warwick
Coventry CV4 7AL

United Kingdom, EUROPE
Tel: 00 44 24 76574359
Fax: 00 44 24 76150897



Warwick group webpage: http://go.warwick.ac.uk/nmr/
The UK 850 MHz solid-state NMR facility: http://go.warwick.ac.uk/850mhz/

Getting to Millburn House: http://go.warwick.ac.uk/nmr/getting_here

Molecular Analytical Sciences Centre for Doctoral Training: http://www2.warwick.ac.uk/fac/sci/mas

Researcher ID: http://www.researcherid.com/rid/F-8765-2014 ORCID ID: 0000-0003-2069-8496


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Monday, July 24, 2017

Meet Bridge12 at ISMAR 2017 #ISMAR2017 #DNPNMR

Meet Bridge12 at this year's ISMAR conference in Quebec. We are sharing the booth with PhoenixNMR and will showcase our instruments for Overhauser DNP spectroscopy at 9 GHz.

Stop by and learn more about our solutions for high and low-field microwave instrumentation for EPR and DNP spectroscopy.

Friday, July 21, 2017

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

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


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

Wednesday, July 19, 2017

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


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


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

Tuesday, July 18, 2017

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


Please forward to potential candidates.

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

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

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

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

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

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

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Monday, July 17, 2017

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


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


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

Friday, July 14, 2017

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


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


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

Wednesday, July 12, 2017

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


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


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

Monday, July 10, 2017

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


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


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

Friday, July 7, 2017

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


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


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

Wednesday, July 5, 2017

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


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


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

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

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



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Monday, July 3, 2017

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


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


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

Friday, June 30, 2017

Solvent suppression in DNP enhanced solid state NMR #DNPNMR


Yarava, J.R., et al., Solvent suppression in DNP enhanced solid state NMR. J Magn Reson, 2017. 277: p. 149-153.


We show how DNP enhanced solid-state NMR spectra can be dramatically simplified by suppression of solvent signals. This is achieved by (i) exploiting the paramagnetic relaxation enhancement of solvent signals relative to materials substrates, or (ii) by using short cross-polarization contact times to transfer hyperpolarization to only directly bonded carbon-13 nuclei in frozen solutions. The methods are evaluated for organic microcrystals, surfaces and frozen solutions. We show how this allows for the acquisition of high-resolution DNP enhanced proton-proton correlation experiments to measure inter-nuclear proximities in an organic solid.

[NMR] Postdoctoral Position in DNP-NMR at Dartmouth

Postdoctoral Position in DNP-NMR at Dartmouth 

A postdoctoral position is available in the group of Professor Chandrasekhar Ramanathan in the Department of Physics and Astronomy at Dartmouth College to investigate the spin physics of surfaces and low-dimensional spin systems using DNP-NMR. 

Our group works at the interface of quantum information processing and condensed matter and materials physics. We develop and use magnetic resonance methods (including NMR, DNP and EDMR) to control and characterize the spin dynamics of solid state spin systems. The lab currently houses a custom-built 94 GHz DNP system, a 7 T solid-state NMR system, a 9.4 T liquid state NMR system and zero- and low-field EDMR systems. Additional information, including recent publications, can be found at http://www.dartmouth.edu/~cramanathan

Application

The preferred applicant will have a PhD in Physics, Chemistry or a related field and strong experimental skills. Knowledge of RF, microwave and cryogenic techniques and magnetic resonance methods is strongly desired. Interested candidates are invited to submit an electronic application (CV, brief statement of research interests and list of references) to sekhar.ramanathan@dartmouth.edu

The anticipated start date is October 1, 2017 or soon after.

About Dartmouth

Founded in 1769, Dartmouth is a member of the Ivy League and has a deep commitment to combining outstanding undergraduate liberal arts and graduate education with distinguished research and scholarship. Dartmouth is located in the scenic Upper Valley region of New England, about a 2-hour drive from Boston and 3.5 hours from Montreal.

------------------------------
Chandrasekhar Ramanathan
Department of Physics and Astronomy
6127 Wilder Laboratory
Dartmouth College
Hanover, NH 03755

Tel: +1 (603) 646-9780



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Thursday, June 29, 2017

[NMR] [Help] Reply Reply All Forward Postdoc or PhD position at the MPI for Biophysical Chemistry in Göttingen, Germany



The “NMR Signal Enhancement Group” at the Max Planck Institute for
Biophysical Chemistry invites applications for a


Ph.D. or Postdoc Position
- Chemist for the synthesis of magnetic resonance contrast agents -
(Code Number 27-17)

We are looking for a highly motivated Ph.D. student or Postdoc who will work on the synthesis of contrast agents for magnetic resonance imaging experiments. The position is to be filled by January 2018.

He/she should have a strong background in synthetic chemistry, medicinal chemistry or related disciplines. Knowledge about magnetic resonance (MR) methods is advantageous.

We offer an international and highly productive and innovative working atmosphere and provide state-of-the-art MR equipment and collaboration possibilities.

For a Ph.D. student position, candidates should hold a Master’s (or equivalent) degree in life science. The Ph.D. position is limited to three years with a possible extension.

Postdoc candidates hold a Ph.D. degree in life science. The initial appointment for Postdocs is 2 years with possibilities for extension.

The payment and benefits are based on the TVöD guidelines.

The Max Planck Society is committed to increasing the number of individuals with disabilities in its workforce and therefore encourages applications from such qualified individuals. Furthermore, the Max Planck Society seeks to increase the number of women in those areas where they are underrepresented and therefore explicitly encourages women to apply.

Interested candidates should send their applications (application deadline: 30.09.2017) preferably via e-mail with reference to the code number 27-17, including a statement of research interests and two letters of recommendation send under separate cover, to



Max Planck Institute for Biophysical Chemistry
NMR Signal Enhancement Group
Dr. Stefan Glöggler
Am Fassberg 11, 37077 Göttingen
Germany

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