Monday, July 16, 2018

Stable Isotope-Resolved Analysis with Quantitative Dissolution Dynamic Nuclear Polarization

Lerche, M. H., D. Yigit, A. B. Frahm, J. H. Ardenkjaer-Larsen, R. M. Malinowski, and P. R. Jensen. “Stable Isotope-Resolved Analysis with Quantitative Dissolution Dynamic Nuclear Polarization.” Analytical Chemistry 90 (January 2, 2018): 674–78. 


Metabolite profiles and their isotopomer distributions can be studied noninvasively in complex mixtures with NMR. The advent of dissolution Dynamic Nuclear Polarization (dDNP) and isotope enrichment add sensitivity and resolution to such metabolic studies. Metabolic pathways and networks can be mapped and quantified if protocols that control and exploit the ex situ signal enhancement are created. We present a sample preparation method, including cell incubation, extraction and signal enhancement, to obtain reproducible and quantitative dDNP (qdDNP) NMR-based stable isotope-resolved analysis. We further illustrate how qdDNP was applied to gain metabolic insights into the phenotype of aggressive cancer cells.

Friday, July 13, 2018

Reversal of Paramagnetic Effects by Electron Spin Saturation #DNPNMR

Jain, Sheetal K., Ting A. Siaw, Asif Equbal, Christopher B. Wilson, Ilia Kaminker, and Songi Han. “Reversal of Paramagnetic Effects by Electron Spin Saturation.” The Journal of Physical Chemistry C 122, no. 10 (March 15, 2018): 5578–89.


We present a study in which both significant dynamic nuclear polarization (DNP) enhancement of 7Li NMR and reversal of the paramagnetic effects (PEs) are achieved by microwave (μw) irradiation-induced electron spin saturation of nitroxide radicals at liquid-helium temperatures. The reversal of the PE was manifested in significant narrowing of the 7Li NMR line and reversal of the paramagnetic chemical shift under DNP conditions. The extent of the PE was found to decrease with increased saturation of the electron paramagnetic resonance line, modulated as a function of microwave (μw) power, frequency, duration of irradiation, and gating time between μw irradiation and NMR detection. The defining observation was the shortening of the electron phase memory time, Tm, of the excited observer spins with increasing μw irradiation and concurrent electron spin saturation of the electron spin bath. This and a series of corroborating studies reveal the origin of the NMR line narrowing to be the reversal of paramagnetic relaxation enhancement (PRE), leading us to debut the term REversal of PRE by electron Spin SaturatION (REPRESSION). The shortening of electron Tm of any paramagnetic system as a function of electron spin saturation has not been reported to date, making REPRESSION a discovery of this study. The reversal of the paramagnetic dipolar shift is due to the decrease in electron spin order, also facilitated by electron spin saturation. This study offers new fundamental insights into PE under DNP conditions and a method to detect and identify NMR signal proximal to paramagnetic sites with reduced or minimal line broadening.

Wednesday, July 11, 2018

Hyperpolarized NMR: d-DNP, PHIP, and SABRE

Kovtunov, Kirill Viktorovich, Ekaterina Pokochueva, Oleg Salnikov, Samuel Cousin, Dennis Kurzbach, Basile Vuichoud, Sami Jannin, et al. “Hyperpolarized NMR: D-DNP, PHIP, and SABRE.” Chemistry – An Asian Journal 0, no. ja (2018).


NMR signals intensities can be enhanced by several orders of magnitude via utilization of techniques for hyperpolarization of different molecules, and it allows one to overcome the main sensitivity challenge of modern NMR/MRI techniques. Hyperpolarized fluids can be successfully used in different applications of material science and biomedicine. This focus review covers the fundamentals of the preparation of hyperpolarized liquids and gases via dissolution dynamic nuclear polarization (d-DNP) and parahydrogen-based techniques such as signal amplification by reversible exchange (SABRE) and parahydrogen-induced polarization (PHIP) in both heterogeneous and homogeneous processes. The different novel aspects of hyperpolarized fluids formation and utilization along with the possibility of NMR signal enhancement observation are described.

Monday, July 9, 2018

Applications of dissolution dynamic nuclear polarization in chemistry and biochemistry

Zhang, Guannan, and Christian Hilty. “Applications of Dissolution Dynamic Nuclear Polarization in Chemistry and Biochemistry.” Magnetic Resonance in Chemistry 0, no. 0 (2018). 


Sensitivity of detection is one of the most limiting aspects when applying NMR spectroscopy to current problems in the molecular sciences. A number of hyperpolarization methods exist for increasing the population difference between nuclear spin Zeeman states and enhance the signal-to-noise ratio by orders of magnitude. Among these methods, dissolution dynamic nuclear polarization (D-DNP) is unique in its capability of providing high spin polarization for many types of molecules in the liquid state. Originally proposed for biomedical applications including in vivo imaging, applications in high resolution NMR spectroscopy are now emerging. These applications are the focus of the present review. Using D-DNP, a small sample aliquot is first hyperpolarized as a frozen solid at low temperature, followed by dissolution into the liquid state. D-DNP extends the capabilities of liquid state NMR spectroscopy towards shorter timescales and enables the study of nonequilibrium processes, such as the kinetics and mechanisms of reactions. It allows the determination of intermolecular interactions, in particular based on spin relaxation parameters. At the same time, a challenge in the application of this hyperpolarization method is that spin polarization is nonrenewable. Substantial effort has been devoted to develop methods for enabling rapid correlation spectroscopy, the measurement of time-dependent signals, and the extension of the observable time window. With these methods, D-DNP has the potential to open new application areas in the chemical and biochemical sciences.

Friday, July 6, 2018

Many-body kinetics of dynamic nuclear polarization by the cross effect #DNPNMR

Karabanov, A., D. Wiśniewski, F. Raimondi, I. Lesanovsky, and W. Köckenberger. “Many-Body Kinetics of Dynamic Nuclear Polarization by the Cross Effect.” Physical Review A 97 (26 2018): 031404.


Dynamic nuclear polarization (DNP) is an out-of-equilibrium method for generating nonthermal spin polarization which provides large signal enhancements in modern diagnostic methods based on nuclear magnetic resonance. A particular instance is cross-effect DNP, which involves the interaction of two coupled electrons with the nuclear spin ensemble. Here we develop a theory for this important DNP mechanism and show that the nonequilibrium nuclear polarization buildup is effectively driven by three-body incoherent Markovian dissipative processes involving simultaneous state changes of two electrons and one nucleus.We identify different parameter regimes for effective polarization transfer and discuss under which conditions the polarization dynamics can be simulated by classical kinetic Monte Carlo methods. Our theoretical approach allows simulations of the polarization dynamics on an individual spin level for ensembles consisting of hundreds of nuclear spins. The insight obtained by these simulations can be used to find optimal experimental conditions for cross-effect DNP and to design tailored radical systems that provide optimal DNP efficiency.

Wednesday, July 4, 2018

Dynamic Nuclear Polarization-Enhanced Biomolecular NMR Spectroscopy at High Magnetic Field with Fast Magic-Angle Spinning #DNPNMR

Jaudzems, Kristaps, Andrea Bertarello, Sachin R. Chaudhari, Andrea Pica, Diane Cala-De Paepe, Emeline Barbet-Massin, Andrew J. Pell, et al. “Dynamic Nuclear Polarization-Enhanced Biomolecular NMR Spectroscopy at High Magnetic Field with Fast Magic-Angle Spinning.” Angewandte Chemie 0 (2018).


Dynamic nuclear polarization (DNP) is a powerful way to overcome the sensitivity limitation of magic?angle?spinning (MAS) NMR experiments. However, the resolution of the DNP?NMR spectra of proteins is compromised by severe line broadening associated with the necessity to perform experiments at cryogenic temperatures and in the presence of paramagnetic radicals. High?quality DNP?enhanced NMR spectra of the Acinetobacter phage 205 (AP205) nucleocapsid can be obtained by combining high magnetic field (800?MHz) and fast MAS (40?kHz). These conditions yield enhanced resolution and long coherence lifetimes allowing the acquisition of resolved 2D correlation spectra and of previously unfeasible scalar?based experiments. This enables the assignment of aromatic resonances of the AP205 coat protein and its packaged RNA, as well as the detection of long?range contacts, which are not observed at room temperature, opening new possibilities for structure determination.

Tuesday, July 3, 2018


Postdoctoral Position:

Development of Pulsed High-Field EPR Methods and Applications
Location: National High Magnetic Field Laboratory, Tallahassee, FL
Application Deadline: Until the position is filled

A postdoctoral position is available in the Electron Magnetic Resonance (EMR) group at the National High Magnetic Field Laboratory (NHMFL). The position will be focused on development of pulsed high-field EPR methods and applications at W-band (94 GHz) and potentially higher frequencies. The successful candidate will have at her or his disposal a state-of-the-art high-power (1 kW peak) W-band spectrometer developed at the University of St. Andrews.1 This instrument offers true nanosecond time resolution and wideband excitation (1 GHz instantaneous bandwidth), facilitating complex pulse programming and arbitrary waveform generation, thus enabling a suite of multi-dimensional electron- (and electron-nuclear) magnetic resonance methodologies. Applicants should be comfortable working on hardware development. However, the end-goal centers on the materials and biological applications.

The EMR facility additionally boasts a wide range of other unique pulsed and continuous wave high-field EPR instruments spanning the range from 9 GHz to 2.5 THz, and magnetic fields up to 45 T. The group comprises six faculty-level researchers, an engineer who assists with instrument development, as well as a cohort of graduate students and postdocs. The group also has strong interactions with EPR and NMR experts in chemistry and biology at both Florida State University and the University of Florida in Gainesville. Further information concerning the NHMFL EMR group, including links to recent publications, can be found at:

http://magnet.fsu.edu/usershub/scientificdivisions/emr/index.html

Minimum qualifications include a Ph.D. in Physics, Chemistry, or a related discipline. Experience in one or more of the following areas is preferred, but not essential: EPR spectroscopy, particularly pulsed and/or high-field EPR; instrument design/development (radio frequency, microwave, software/hardware interface…); biological or materials EPR applications. Questions regarding the position should be directed to the EMR Director, Stephen Hill (shill@magnet.fsu.edu). To apply, please send a CV, a cover letter describing your experience and research interests, and the contact information for three references, preferably by email to:

Morgan Fitch, Administrative Support Assistant

National High Magnetic Field Laboratory

1800 E. Paul Dirac Dr., Tallahassee, FL 32310, USA

Email: mfitch@magnet.fsu.edu (with cc. to shill@magnet.fsu.edu)

The NHMFL is operated for the US National Science Foundation by a collaboration of institutions comprising Florida State University, the University of Florida, and Los Alamos National Laboratory. https://nationalmaglab.org/

Florida State University is an Equal Opportunity/Access/Affirmative Action/Pro Disabled & Veteran Employer. http://www.hr.fsu.edu/PDF/Publications/diversity/EEO_Statement.pdf

1Cruikshank et al., Rev. Sci. Inst. 80, 103102 (2009); https://doi.org/10.1063/1.3239402

Monday, July 2, 2018

Biomolecular imaging of (13)C-butyrate with dissolution-DNP: Polarization enhancement and formulation for in vivo studies

Flori, A., G. Giovannetti, M. F. Santarelli, G. D. Aquaro, D. De Marchi, S. Burchielli, F. Frijia, V. Positano, L. Landini, and L. Menichetti. “Biomolecular Imaging of (13)C-Butyrate with Dissolution-DNP: Polarization Enhancement and Formulation for in Vivo Studies.” Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy 199 (June 15, 2018): 153–60.


Magnetic Resonance Spectroscopy of hyperpolarized isotopically enriched molecules facilitates the non-invasive real-time investigation of in vivo tissue metabolism in the time-frame of a few minutes; this opens up a new avenue in the development of biomolecular probes. Dissolution Dynamic Nuclear Polarization is a hyperpolarization technique yielding a more than four orders of magnitude increase in the (13)C polarization for in vivo Magnetic Resonance Spectroscopy studies. As reported in several studies, the dissolution Dynamic Nuclear Polarization polarization performance relies on the chemico-physical properties of the sample. In this study, we describe and quantify the effects of the different sample components on the dissolution Dynamic Nuclear Polarization performance of [1-(13)C]butyrate. In particular, we focus on the polarization enhancement provided by the incremental addition of the glassy agent dimethyl sulfoxide and gadolinium chelate to the formulation. Finally, preliminary results obtained after injection in healthy rats are also reported, showing the feasibility of an in vivo Magnetic Resonance Spectroscopy study with hyperpolarized [1-(13)C]butyrate using a 3T clinical set-up.

Friday, June 29, 2018

Paramagnetic metal ion dopants as polarization agents for DNP NMR spectroscopy in inorganic solids #DNPNMR

Chakrabrty Tanmoy, Goldin Nir, Feintuch Akiva, Houben Lothar, and Leskes Michal. “Paramagnetic Metal Ion Dopants as Polarization Agents for DNP NMR Spectroscopy in Inorganic Solids.” ChemPhysChem 0, no. ja (May 17, 2018).



Dynamic nuclear polarization (DNP), a technique in which the high electron spin polarization is transferred to surrounding nuclei via microwaves irradiation, equips solid state NMR spectroscopy with unprecedented sensitivity. The most commonly used polarization agents for DNP are nitroxide radicals. However, their applicability to inorganic materials is mostly limited to surface detection. Paramagnetic metal ions were recently introduced as alternatives for nitroxides. Doping inorganic solids with paramagnetic ions can be used to tune material properties and introduces endogenous DNP agents that can potentially provide sensitivity in the particles' bulk and surface. Here we demonstrate the approach by doping Li4Ti5O12 (LTO), an anode material for lithium ion batteries, with paramagnetic ions. By incorporating Gd(III) and Mn(II) in LTO we gain up to 14 fold increase in signal intensity in static 7Li DNP?NMR experiments. These results suggest that doping with paramagnetic ions provides an efficient route for sensitivity enhancement in the bulk of micron size particles.

[NMR] DNP NMR postdoc position at NHMFL, Tallahassee, FL #DNPNMR

Postdoctoral Position:

Development of High-Field Solution-State Overhauser DNP NMR Spectroscopy

Location: National High Magnetic Field Laboratory, Tallahassee, FL

Application Deadline: Until the position is filled 
A postdoctoral position is available, starting Fall 2018, at the U.S. National High Magnetic Field Laboratory (NHMFL) in Tallahassee Florida to carry out research on Overhauser Dynamic Nuclear Polarization (ODNP) NMR at high field (14.1 T). This position is fully funded for a period of 3 years by the National Science Foundation. For this research project, the NHMFL facility is equipped with a 600 MHz solution-state NMR spectrometer and a matching 395 GHz Gyrotron. We seek highly motivated applicants to work with the NHMFL DNP group to develop and implement new methods and experimental applications needed for enabling ODNP NMR spectroscopy of small to medium-sized molecules. The resulting solution-state ODNP NMR experiments will have applications in chemistry and biochemistry, particularly for characterizing limited quantities of molecules from natural product and pharmaceutical chemistry, from petroleum and polymer analytical chemistry, from food and environmental sciences, and from metabolomics.

The successful candidate will be involved in collaborative research with other experts at the NHMFL working in chemical and physical applications of ODNP NMR, as well as advanced microwave and RF instrumentation and technology. He/she will work within a team that consists of the faculty and engineers in the NMR and EPR divisions. Minimum qualifications include a Ph.D. in Chemistry, Physics or a related discipline related to advanced NMR. Experience in experimental NMR methods is essential and in DNP and/or EPR is expected. 

This position will remain available until filled. To apply, please send a CV, a cover letter describing your experience and research interests, and contact information for three references to:


Sungsool Wi

National High Magnetic Field laboratory
1800 E. Paul Dirac Drive, Tallahassee, FL 32310, USA
Tel: 850-645-2770

The NHMFL is operated for the National Science Foundation by a collaboration of institutions comprising Florida State University, the University of Florida, and Los Alamos National Laboratory. https://nationalmaglab.org/

Florida State University (FSU) is an Equal Opportunity/Access/Affirmative Action/Pro Disabled & Veteran Employer. http://www.hr.fsu.edu/PDF/Publications/diversity/EEO_Statement.pdf
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Thursday, June 28, 2018

[NMR] Postdoc Positions in DNP at ETH

Dear Colleagues,

there are two postdoctoral positions open at ETH Zurich in the field of DNP in the groups of Sebastian Kozerke and Matthias Ernst.

The first positions concerns Magnetic Resonance (MR) pulse sequence design, image reconstruction and data analysis approaches for Dynamic Nuclear Polarization (DNP) based hyperpolarized imaging of cardiac perfusion and metabolism on experimental MR equipment: https://apply.refline.ch/845721/6341/pub/1/index.html It will be based at the Institut for Biomedical Engineering (Sebastian Kozerke, http://www.cmr.ethz.ch).

The second position concerns the development of Dynamic Nuclear Polarization (DNP) based hyperpolarized methods for in-vitro and in-vivo imaging purposes. Project foci are on DNP hardware development and optimization as well as on novel materials for hyperpolarized imaging including nanoparticles for in-vivo imaging applications:
It will be based at the Laboratory for Physical Chemistry (Matthias Ernst,

Both positions are part of a long-standing collaboration between the two groups and close collaboration with students and postdocs in both groups is expected. In the past we have developed three DNP polarizers at 3.4 and 7 T field which can be used with NMR systems and a small animal imaging systems. The group of Sebastian Kozerke also has a SpinLab polarizer for clinical imaging systems available.

More information can be found online under the above mentioned links. For detailed questions about the two positions, please contact Sebastian Kozerke (kozerke@biomed.ee.ethz.ch) or Matthias Ernst (maer@ethz.ch). Applications for the two positions can be submitted online using the above mentioned links.

Best regards,
Matthias Ernst

-- 
+----------------------------------------+-----------------------------------+
| Matthias Ernst | Phone: +41-44-632-4366 |
| ETH Zürich, HCI D 227 | Fax: +41-44-632-1621 |
| Laboratorium für Physikalische Chemie | |
| Wolfgang-Pauli-Strasse 10 | Email: maer@ethz.ch |
| CH-8093 Zürich, Switzerland | maer@gmx.ch |
+----------------------------------------+-----------------------------------+

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[NMR] Post Doc Position in Biomolecular Solid-State NMR at USC, Los Angeles

Dear Colleagues,

The Siemer lab at USC is looking for a post-doctoral associate with a background in NMR spectroscopy and knowledge of protein biochemical techniques. The lab studies the structure and dynamics, of functional and toxic amyloid fibrils. To this goal, we apply solid-state NMR spectroscopy together with other biochemical and biophysical methods.

The Siemer lab is part of the Protein Structure Center at USC and works in close collaboration wit the EPR lab of Ralf Langen and liquid-state NMR lab of Tobias Ulmer as part of an effort to investigate nervous system function with biophysical methods in an interdisciplinary environment.

The position is available immediately. Interested candidates should send their CV's including the names of three references to Ansgar Siemer asiemer@usc.edu.
-- 
Ansgar B Siemer 
Assistant Professor,
Physiology & Neuroscience
Zilkha Neurogenetic Institute
Keck School of Medicine of USC
1501 San Pablo Street, ZNI 119F
Los Angeles, CA 90033
Tel: +1-323-442-2720


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[NMR] Associate Research Engineer position at BASF (Ludwigshafen/Germany)


Dear colleague,

BASF has an opening for an Associate Research Engineer at the interface of Solid-State NMR and Surface Spectroscopy.

The position will be associated with Dr. Sabine Hirth (Surface Analytics by XPS and ToF-SIMS) and Dr. Karsten Seidel (Solid-State NMR). We are two teams in the Structures & Surfaces group at BASF’s Department of Material Physics & Analytics. We are part of a central research platform which serves the entire BASF community. The new team member shall strengthen our efforts in the characterization of inorganic materials, in particular battery materials, as well as other complex materials, using multi-method approaches in both labs and beyond.

Please note: this position aims at a permanent lab-based employment, and is typically addressing scientists with a Master’s degree (or Bachelor’s degree + job experience). PhD graduates may want to apply for “Research Scientist” or “Laborleiter” positions on careers.basf.com.

Having a good command of the German language is not a prerequisite, and actually, scientific reporting at BASF is preferably done in English. However, it is generally very helpful to know or quickly learn German. In fact, the job posting is currently available only in German:


[in case the link does not work, please go to careers.basf.com and search jobs for “NMR”]

Job profile (translation of selected items):

Self-dependent experimental work in projects as well as routine analytical services
Adaptation and development of methods to characterize materials, such as battery materials
Methods development using complex analytical techniques with X-ray-Photoelectron-, Mass- and NMR-Spectrometers
Study of scientific literature, active learning from others
Presentation of work in project meetings, authoring of comprehensive lab reports

Your profile (translation of selected items):

Degree in chemistry, physics, or a related field of science (Master’s degree, or comparable qualification, such as Bachelor’s degree plus adequate job experience, or „Chemotechniker“ plus adequate job experience)
Advanced knowledge of inorganic chemistry
Experience with instrumental analytics, preferably XPS, ToF-SIMS, NMR
Interest to permanently work in the field of analytics and analytical methods development
You have been actively performing complex data analysis using advanced IT tools, including an understanding of the mathematical background
Very good communication skills, as well as an independent and target-oriented style of work

We are looking forward to receiving your application through careers.basf.com. (Further inquiries may be sent to karsten.seidel@basf.com, applications will be accepted through the job portal.)

We are located at BASF’s headquarters in Ludwigshafen/Germany. Ludwigshafen is a twin city with Mannheim, other cities close by are Heidelberg, Karlsruhe, Darmstadt, Worms, and Neustadt an der Weinstraße. Frankfurt is less than 1h from here. The region is known e.g. for its chemical, pharmaceutical, automotive and construction industry, as well as for its beautiful surrounding, such as the Palatinate forest and the Odenwald forest, with its modest climate and popular vineyards.

With best regards,

Sabine Hirth & Karsten Seidel

BASF SE, Registered Office: 67056 Ludwigshafen, Germany 
Registration Court: Amtsgericht Ludwigshafen, Registration No.: HRB 6000 
Chairman of the Supervisory Board: Juergen Hambrecht 
Board of Executive Directors:
Martin Brudermueller, Chairman; Hans-Ulrich Engel, Vice Chairman; 
Saori Dubourg, Sanjeev Gandhi, Michael Heinz, Markus Kamieth, Wayne T. Smith

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[NMR] PhD position in the Etzkon lab



A PhD position is open in the field of NMR characterization of membrane-protein structure and function. The positions will be part of the research group of Manuel Etzkorn at the Biomolecular NMR Center of Düsseldorf University and the Helmholtz Research Center (Forschungszentrum) Jülich. 

The project will focus on the characterization of pharmacologically important membrane proteins as well as the development of novel NMR and biochemical techniques tailored to enhance insights into these challenging systems. Depending on individual qualification and interest you will have the opportunity to work on various aspects of this highly interdisciplinary topic including (cell-free) protein expression, enhanced membrane mimetics, biophysical assays, as well as solution- and (DNP) solid-state NMR spectroscopy. 

Candidates should be highly motivated with a strong interest in structural biology. Previous experience in at least one of the following areas is mandatory: protein biochemistry, cell biology and biophysical characterization of membrane systems and/or NMR spectroscopy. Funding for the PhD project (estimated duration 3 - 3.5 years) is secured. Starting date will be August 2018 or later.

The Biomolecular NMR Center Düsseldorf/Jülich offers an exciting and stimulating research environment and is very well equipped with state-of-the-art biophysical instrumentation as well as high-field solution- and solid-state NMR spectrometers operating at 900 MHz, 3x 800 MHz, 750 MHz, 700 MHz, 4x 600 MHz (including DNP at 600 and 800 MHz). In addition, a 1200 MHz system should become available during the PhD project. 

Düsseldorf is a very pleasant city with a vivid historic center located directly at the scenic Rhein river and offers a large variety of cultural and recreational activities frequently placing Düsseldorf into the (top ten) lists of cities with the highest quality of life worldwide. 

Applications should include a cover letter with a brief description of previous research experience and motivation to join the group, a CV, and contact information for at least two reference persons (typically including the supervisor(s) of the master thesis). Applications and informal inquiries about the lab and research project should be directed via email to Manuel Etzkorn (manuel.etzkorn@hhu.de).

More infos can be found on the group's homepage: www.etzkornlab.de


Please feel free to forward this message to potential candidates.


____________________________

Dr. Manuel Etzkorn


Institute of Physical Biology
Heinrich-Heine-University
Universitätsstr. 1
Bldg. 26.11.U1 Room 24
D-40225 Düsseldorf


Phone: +49 211 8112023







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Wednesday, June 27, 2018

Eigenstate versus Zeeman-based approaches to the solid effect #DNPNMR

Rodríguez‐Arias, Inés, Alberto Rosso, and Andrea De Luca. “Eigenstate versus Zeeman-Based Approaches to the Solid Effect.” Magnetic Resonance in Chemistry 0, no. 0 (2017).


The solid effect is one of the simplest and most effective mechanisms for dynamic nuclear polarization. It involves the exchange of polarization between one electron and one nuclear spin coupled via the hyperfine interaction. Even for such a small spin system, the theoretical understanding is complicated by the contact with the lattice and the microwave irradiation. Both being weak, they can be treated within perturbation theory. In this work, we analyze the two most popular perturbation schemes: the Zeeman and the eigenstate-based approaches, which differ in the way the hyperfine interaction is treated. For both schemes, we derive from first principles an effective Liouville equation that describes the density matrix of the spin system; we then study numerically the behavior of the nuclear polarization for several values of the hyperfine coupling. In general, we obtain that the Zeeman-based approach underestimates the value of the nuclear polarization. By performing a projection onto the diagonal part of the spin-system density matrix, we are able to understand the origin of the discrepancy, which is due to the presence of parasite leakage transitions appearing whenever the Zeeman basis is employed.

Monday, June 25, 2018

Assembly and performance of a 6.4 T cryogen-free dynamic nuclear polarization system #DNPNMR

Kiswandhi, Andhika, Peter Niedbalski, Christopher Parish, Qing Wang, and Lloyd Lumata. “Assembly and Performance of a 6.4 T Cryogen-Free Dynamic Nuclear Polarization System.” Magnetic Resonance in Chemistry 55, no. 9 (2017): 846–52.


We report on the assembly and performance evaluation of a 180-GHz/6.4 T dynamic nuclear polarization (DNP) system based on a cryogen-free superconducting magnet. The DNP system utilizes a variable-field superconducting magnet that can be ramped up to 9 T and equipped with cryocoolers that can cool the sample space with the DNP assembly down to 1.8 K via the Joule–Thomson effect. A homebuilt DNP probe insert with top-tuned nuclear magnetic resonance coil and microwave port was incorporated into the sample space in which the effective sample temperature is approximately 1.9 K when a 180-GHz microwave source is on during DNP operation. 13C DNP of [1-13C] acetate samples doped with trityl OX063 and 4-oxo-TEMPO in this system have resulted in solid-state 13C polarization levels of 58 ± 3% and 18 ± 2%, respectively. The relatively high 13C polarization levels achieved in this work have demonstrated that the use of a cryogen-free superconducting magnet for 13C DNP is feasible and in fact, relatively efficient—a major leap to offset the high cost of liquid helium consumption in DNP experiments.

Friday, June 22, 2018

Electron spin resonance studies on deuterated nitroxyl spin probes used in Overhauser-enhanced magnetic resonance imaging #DNPNMR #ODNP

Jebaraj, D. David, Hideo Utsumi, and A. Milton Franklin Benial. “Electron Spin Resonance Studies on Deuterated Nitroxyl Spin Probes Used in Overhauser-Enhanced Magnetic Resonance Imaging.” Magnetic Resonance in Chemistry 55, no. 8 (2017): 700–705. 


The electron spin resonance studies were carried out for 2 mm concentration of 14N-labeled and 15N-labeled 3-carbamoyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl, 3-carboxy-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl, 3-methoxycarbonyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl and their deuterated nitroxyl radicals using X-band electron spin resonance spectrometer. The electron spin resonance line shape analysis was carried out. The electron spin resonance parameters such as linewidth, Lorentzian component, signal intensity ratio, rotational correlation time, hyperfine coupling constant and g-factor were estimated. The deuterated nitroxyl radicals have narrow linewidth and an increase in Lorentzian component, compared with undeuterated nitroxyl radicals. The dynamic nuclear polarization factor was observed for all nitroxyl radicals. Upon 2H labeling, about 70% and 40% increase in dynamic nuclear polarization factor were observed for 14N-labeled and 15N-labeled nitroxyl radicals, respectively. The signal intensity ratio and g-value indicate the isotropic nature of the nitroxyl radicals in pure water. Therefore, the deuterated nitroxyl radicals are suitable spin probes for in vivo/in vitro electron spin resonance and Overhauser-enhanced magnetic resonance imaging modalities. Copyright © 2017 John Wiley & Sons, Ltd.

Wednesday, June 20, 2018

A table-top PXI based low-field spectrometer for solution dynamic nuclear polarization #DNPNMR #ODNP

Biller, Joshua R., Karl F. Stupic, and J. Moreland. “A Table-Top PXI Based Low-Field Spectrometer for Solution Dynamic Nuclear Polarization.” Magnetic Resonance in Chemistry 56, no. 3 (2017): 153–63.


We present the development of a portable dynamic nuclear polarization (DNP) instrument based on the PCI eXtensions for Instrumentation platform. The main purpose of the instrument is for study of 1H polarization enhancements in solution through the Overhauser mechanism at low magnetic fields. A DNP probe set was constructed for use at 6.7 mT, using a modified Alderman–Grant resonator at 241 MHz for saturation of the electron transition. The solenoid for detection of the enhanced 1H signal at 288 kHz was constructed with Litz wire. The largest observed 1H enhancements (ε) at 6.7 mT for 14N-CTPO radical in air saturated aqueous solution was ε 65. A concentration dependence of the enhancement is observed, with maximum ε at 5.5 mM. A low resonator efficiency for saturation of the electron paramagnetic resonance transition results in a decrease in ε for the 10.3 mM sample. At high incident powers (42 W) and long pump times, capacitor heating effects can also decrease the enhancement. The core unit and program described here could be easily adopted for multi-frequency DNP work, depending on available main magnets and selection of the “plug and play” arbitrary waveform generator, digitizer, and radiofrequency synthesizer PCI eXtensions for Instrumentatione cards.

Monday, June 18, 2018

DNP sensitivity of 19F-NMR signals in hexafluorobenzene depending on polarizing agent type #DNPNMR #ODNP

Peksoz, Ahmet. “DNP Sensitivity of 19F-NMR Signals in Hexafluorobenzene Depending on Polarizing Agent Type.” Magnetic Resonance in Chemistry 54, no. 9 (2016): 748–52. 


Low field dynamic nuclear polarization or low field magnetic double resonance technique enables enhanced nuclear magnetic resonance signals to be detected without increasing the strength of the polarizing field. The study reports that the dynamic nuclear polarization of 19F nuclei in hexafluorobenzene solutions doped with nitroxide, BDPA, MC800 asphaltene and MC30 asphaltene free radicals at 15 G. The 19F nuclei in all solutions gave positive DNP enhancements changing between 3.42 and 189.54, corresponding to predominantly scalar interactions with the unpaired electrons in the radicals. DNP sensitivity of 19F nuclei in hexafluorobenzene was observed to be changed significantly depending on the radical type. Nitroxide was found to have the best DNP performance among the polarizing agents. Copyright © 2016 John Wiley & Sons, Ltd.

Friday, June 15, 2018

13C dynamic nuclear polarization using isotopically enriched 4-oxo-TEMPO free radicals #DNPNMR

Niedbalski, Peter, Christopher Parish, Andhika Kiswandhi, and Lloyd Lumata. “13C Dynamic Nuclear Polarization Using Isotopically Enriched 4-Oxo-TEMPO Free Radicals.” Magnetic Resonance in Chemistry 54, no. 12 (2016): 962–67.


The nitroxide-based free radical 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) is a widely used polarizing agent in NMR signal amplification via dissolution dynamic nuclear polarization (DNP). In this study, we have thoroughly investigated the effects of 15N and/or 2H isotopic labeling of 4-oxo-TEMPO free radical on 13C DNP of 3 M [1-13C] sodium acetate samples in 1 : 1 v/v glycerol : water at 3.35 T and 1.2 K. Four variants of this free radical were used for 13C DNP: 4-oxo-TEMPO, 4-oxo-TEMPO-15N, 4-oxo-TEMPO-d16 and 4-oxo-TEMPO-15N,d16. Our results indicate that, despite the striking differences seen in the electron spin resonance (ESR) spectral features, the 13C DNP efficiency of these 15N and/or 2H-enriched 4-oxo-TEMPO free radicals are relatively the same compared with 13C DNP performance of the regular 4-oxo-TEMPO. Furthermore, when fully deuterated glassing solvents were used, the 13C DNP signals of these samples all doubled in the same manner, and the 13C polarization buildup was faster by a factor of 2 for all samples. The data here suggest that the hyperfine coupling contributions of these isotopically enriched 4-oxo-TEMPO free radicals have negligible effects on the 13C DNP efficiency at 3.35 T and 1.2 K. These results are discussed in light of the spin temperature model of DNP. Copyright © 2016 John Wiley & Sons, Ltd.

Wednesday, June 13, 2018

ESR line width and line shape dependence of Overhauser-enhanced magnetic resonance imaging #DNPNMR

Meenakumari, V., Hideo Utsumi, A. Jawahar, and A. Milton Franklin Benial. “ESR Line Width and Line Shape Dependence of Overhauser-Enhanced Magnetic Resonance Imaging.” Magnetic Resonance in Chemistry 54, no. 11 (2016): 874–79.


Electron spin resonance and Overhauser-enhanced magnetic resonance imaging studies were carried out for various concentrations of 14N-labeled 3-carbamoyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl in pure water. Overhauser-enhancement factor attains maxima in the range of 2.5–3 mm concentration. The leakage factor showed an asymptotic increase with increasing agent concentration. The coupling parameter showed the interaction between the electron and nuclear spins to be mainly dipolar in origin. The electron spin resonance parameters, such as the line width, line shape and g-factor, were determined. The line width analysis confirms that the line broadening is proportional to the agent concentration, and also the agent concentration is optimized in the range of 2.5–3 mm. The line shape analysis shows that the observed electron spin resonance line shape is a Voigt line shape, in which the Lorentzian component is dominant. The contribution of Lorentzian component was estimated using the winsim package. The Lorentzian component of the resonance line attains maxima in the range of 2.5–3 mm concentration. Therefore, this study reveals that the agent concentration, line width and Lorentzian component are the important factors in determining the Overhauser-enhancement factor. Hence, the agent concentration was optimized as 2.5–3 mm for in vivo/in vitro electron spin resonance imaging and Overhauser-enhanced magnetic resonance imaging phantom studies. Copyright © 2016 John Wiley & Sons, Ltd.

Monday, June 11, 2018

Co-acquisition of hyperpolarised 13C and 15N NMR spectra #DNPNMR

Already I bit older bit still worth to read.


Day, Iain J., John C. Mitchell, Martin J. Snowden, and Adrian L. Davis. “Co-Acquisition of Hyperpolarised 13C and 15N NMR Spectra.” Magnetic Resonance in Chemistry 45, no. 12 (2007): 1018–21.


Recent developments in dynamic nuclear polarisation now allow significant enhancements to be generated in the cryo solid state and transferred to the liquid state for detection at high resolution. We demonstrate that the Ardenkjaer–Larsen method can be extended by taking advantage of the properties of the trityl radicals used. It is possible to hyperpolarise 13C and 15N simultaneously in the solid state, and to maintain these hyperpolarisations through rapid dissolution into the liquid state. We demonstrate the almost simultaneous measurement of hyperpolarised 13C and hyperpolarised 15N NMR spectra. The prospects for further improvement of the method using contemporary technology are also discussed. Copyright © 2007 John Wiley & Sons, Ltd.

Friday, June 8, 2018

Perspectives on hyperpolarised solution-state magnetic resonance in chemistry #DNPNMR

Dumez, Jean-Nicolas. “Perspectives on Hyperpolarised Solution-State Magnetic Resonance in Chemistry.” Magnetic Resonance in Chemistry 55, no. 1 (2016): 38–46. 




This perspective article reviews some of the recent developments in the field of hyperpolarisation, with a focus on solution-state NMR spectroscopy of small molecules. Two techniques are considered in more detail, dissolution dynamic nuclear polarisation (D-DNP) and signal amplification by reversible exchange (SABRE). Some of the opportunities and challenges for applications of hyperpolarised solution-state magnetic resonance in chemistry are discussed. 

Wednesday, June 6, 2018

Nanodiamond as a New Hyperpolarizing Agent and Its 13C MRS #DNPNMR

Dutta, Prasanta, Gary V. Martinez, and Robert J. Gillies. “Nanodiamond as a New Hyperpolarizing Agent and Its 13C MRS.” The Journal of Physical Chemistry Letters 5, no. 3 (February 6, 2014): 597–600.




In this work, we have hyperpolarized carbonaceous nanoparticles (D ≈ 10 nm), that is, “nanodiamonds”, with 1.1% 13C (natural abundance) using dynamic nuclear polarization (DNP). The polarization buildup curve showed a signal enhancement with relative intensity up to 4700 at 1.4 K and 100 mW microwave power. 13C magnetic resonance spectra (MRS) were obtained from the sample at 7 T, and the signal decayed with a T1 of 55 ± 3s. Notably, polarization was possible in the absence of added radical, consistent with previous results showing endogenous unpaired electrons in natural nanodiamonds. These likely contribute to the shorter T1’s compared to those of highly pure diamond. Despite the relatively short T1, these observations suggest that natural nanodiamonds may be useful for in vivo applications.

[NMR] Registration Open for Solid-State NMR School, Palma de Mallorca October 21-26, 2018

Dear Colleagues,

there are only a few places left at the biological solid-state NMR school this year in Palma. Please apply soon if you would like to attend the school.

Best regards,
Matthias Ernst

-------------------------------------------------------------------------------
Dear Colleagues,

Every second year, the subdivision for biological solid-state NMR of the Groupement AMPERE (https://www.ampere-society.org) organizes an advanced school on biological solid-state NMR. The 7th edition of the school will take place at the Universitat de les Illes Balears, Palma de Mallorca, Spain from October 21-26, 2018. Palma de Mallorca is well connected to most airports in Europe with cheap flights and budget accommodation outside the main tourist season.

The School is aimed at advanced students who have a good knowledge of the basics of solid-state NMR. The School has the purpose of teaching the students a broad range of topics required to understand the modern solid-state NMR experiments which are used in biological applications: Hamiltonians in NMR, isotropic and anisotropic interactions, tensor description of NMR, spherical tensors and tensor rotations, time-dependent Hamiltonians, average Hamiltonian and Floquet theory, principles of recoupling and decoupling under MAS, spin-dynamic simulations using SIMPSON, basic principles and applications of MAS DNP, EPR and paramagnetic NMR, characterization of dynamic processes, protocols for the assignment of protein spectra and protein structure determination, the basics of solid-state NMR instrumentation as well as sample preparation and isotope-labelling techniques.

Registration for the advanced school on biological solid-state NMR is now open at https://biosolidnmr-school.org/school-2018/registration/ Please register as soon as possible if you are interested in attending the school. Places are limited.

There are also student stipends available to help with travel and accommodation due to generous contributions by EBSA and Groupement AMPERE and our sponsors. Details for the application process can be found on the registration web page.

Best regards,
Anja Böckmann, Beat Meier, Hartmut Oschkinat, and Matthias Ernst

-- 
+----------------------------------------+-----------------------------------+
| Matthias Ernst | Phone: +41-44-632-4366 |
| ETH Zürich, HCI D 227 | Fax: +41-44-632-1621 |
| Laboratorium für Physikalische Chemie | |
| Wolfgang-Pauli-Strasse 10 | Email: maer@ethz.ch |
| CH-8093 Zürich, Switzerland | maer@gmx.ch |
+----------------------------------------+-----------------------------------+

[NMR] Postdoctoral position in Lewandowski group at University of Warwick, UK - solid-state & solution NMR of natural products megasynthesases

A 2-year ERC-funded postdoc position is available in the Lewandowski group (http://go.warwick.ac.uk/lewandowskigroup) in the Department of Chemistry at the University of Warwick, United Kingdom.

Duration: 2 years | Start: Aug-Sept 2018 | Application deadline: 22 June 2018


The applicant will work on a major ERC-funded project employing combination of chemical biology, solid-state and solution-state NMR to study the structures, dynamics and interactions of domains from within polyketide synthases in order to facilitate their rational engineering for synthetic biology applications. Polyketide synthases are multicomponent enzymatic assembly lines for a range of useful natural products, for example, antibiotics that are effective against certain multidrug resistant infections. 

Experience in applying solution and/or solid-state NMR spectroscopy to elucidating the structures and/or dynamics of proteins is advantageous and a good knowledge of techniques for the overproduction and purification of recombinant proteins is essential.

The applicant will join a highly interdisciplinary collaborative team (exposure to a wide range of expertise and high potential for picking up new skills) under the supervision of Józef Lewandowski (http://go.warwick.ac.uk/lewandowskigroup) and in collaboration with Greg Challis (https://warwick.ac.uk/fac/sci/chemistry/research/challis/challisgroup).

Facilities:
The Warwick Laboratory for Magnetic Resonance
is a world-class biological and material science magnetic resonance set up hosting 7 academic staff from Physics and Chemistry and housing a suite of 9 solid-state NMR spectrometers (from 100 to 850 MHz; the main spectrometers for the biomolecular applications are 500, 600 and 700 MHz + access to 850 MHz and soon 1 GHz through a national facility at Warwick; a ¾ of 700 MHz solid-state NMR spectrometer time is dedicated to the project), 2 dynamic nuclear polarization (DNP) spectrometers (94 and 200/400 GHz) and advanced EPR instrumentation. A wide range of magic angle spinning probes is available in the laboratory including several 1.3 mm Bruker probes (< 67 kHz spinning), 1 mm JEOL probe, 0.81 mm Samoson probe (100 kHz spinning) and 3x 0.7 mm Bruker probes (111 kHz spinning). Solution NMR facilities include 500, 600 and 700 MHz equipped with cryoprobe (https://warwick.ac.uk/fac/sci/chemistry/research/facilities/nmr/). We have access to the state of the art mass spec facilities 
The Chemical Biology Research Facility at University of Warwick
 (https://warwick.ac.uk/fac/sci/chemistry/research/facilities/chembiolfacility/) provides cutting edge infrastructure for organic synthesis, molecular biology, protein chemistry, microbiology, radiochemistry, biophysical and biochemical analysis.

Informal inquiries should be directed to Józef Lewandowski (j.r.lewandowski@warwick.ac.uk) and formal applications submitted (deadline Jun 22 2018) at

Another postdoctoral position on a related BBSRC-funded project will become available in July 2018.

==========================================================================

Józef R. Lewandowski
Associate Professor | Department of Chemistry | University of Warwick
j.r.lewandowski@warwick.ac.uk | External: +44 (0) 24 76151355 | Internal: 51355 

Chemistry: C519 | Millburn House: F07 | Coventry CV4 7AL | Find us on the interactive map


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[NMR] Postdoctoral position; solid state NMR of membrane proteins #NMR

Postdoctoral Research Associate in Membrane Protein Structural Biology
Department of Biochemistry, South Parks Road, Oxford


We are seeking to appoint a Postdoctoral Research Associate in Membrane Protein Structural Biology. The project aims to understand transport in the POT family of proton coupled peptide transporters using a multidisciplinary approach involving lipidic cubic phase crystallography, thermodynamic and kinetic analysis, using biophysical and liposome based systems, as well as state of the art spectroscopy techniques.

Applicants should hold a PhD/DPhil, or be near completion of a PhD/DPhil, in biochemistry or a related subject area and should have experience with solid state NMR and/or ESR DEER, and other biophysical techniques with membrane systems as well as specialized sample production for spectroscopic investigations. You should also be willing to tackle challenging projects and have the ability to independently analyse data, and design biochemical assays to address important mechanistic questions. Previous experience of working with challenging systems for magnetic resonance would be an advantage.

This full-time fixed-term post is funded by BBSRC for up to 2 years in the first instance and is based at the Department of Biochemistry, South Parks Road, Oxford, and is supervised jointly between Professor Anthony Watts and Professor Simon Newstead.

This position is graded on the University’s Grade 7 scale. The actual starting salary offered will be based on qualifications and relevant skills acquired and will also be determined by the funding available.

Further particulars, including details of how to apply, can be obtained from the document below.

For further general information phone 01865 613204, quoting reference number 135283.

The closing date for applications is 12.00 noon on Friday 6 July 2018, with interviews for shortlisted candidates to be held as soon as possible thereafter.
Contact Person : HR Officer Vacancy ID : 135283
Contact Phone : 01865 613204 Closing Date : 06-Jul-2018
Contact Email : jobs@bioch.ox.ac.uk

Regards

Tony

-----------------------------------------------------
Anthony Watts 
President, European Biophysical Societies Association (EBSA)
Editor, European Biophysical Journal,
Biochemistry Dept., 
South Parks Road,
Oxford, OX1 3QU, UK

Tel. no +44 - (0)1865- 613219 FAX no. +44 - (0)1865- 613201

--------------------------- http://www.bioch.ox.ac.uk/~awatts/ ----------------

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[NMR] Engineer position in DNP-NMR in Paris

Dear Colleagues,

We have an open position in Paris for a staff scientist (research engineer IR2 CNRS) to work on dynamic nuclear polarization.

The successful candidate will manage the DNP infrastructure jointly developed by the groups of Geoffrey Bodenhausen and Nicolas Giraud in the frame of the Equipex program « Paris en résonance ». In addition to in-house research, this platform also provides access to DNP enhanced NMR equipment for users from both academic and industrial laboratories. The DNP facility aims at improving the sensitivity of NMR through the development of equipment that couples solution NMR with dynamic nuclear polarization techniques. Two devices for dissolution-DNP have been installed at the Ecole Normale Supérieure (UMR CNRS 7203) and one at the Université Paris Descartes (UMR CNRS 8601). The NMR group at the Ecole Normale Supérieure is recognized for numerous contributions to magnetic resonance, with a particular focus on the structure and dynamics of biomolecules, and more recently on the development of DNP, both in solids and in solution. The group of Nicolas Giraud at Université Paris Descartes has developed a strong expertise in the development of methods for the analysis of biological substances by NMR, ranging from interaction studies involving biomolecules to metabolomics. 

The research engineer will spend 50 % of his/her time in each laboratory, with the responsibility of maintaining and developing apparatus used to perform dynamic nuclear polarization and to analyze samples by NMR after dissolution. He/she will also be involved in research projects that are carried out in the two groups, targeting the development of hyperpolarization methods, both from fundamental and technical perspectives, and their applications to challenging systems. He/she will supervise and assist external users, as well as colleagues and students from both groups, in the implementation of new experiments and hardware, as well as data processing and analysis.

The position requires a doctoral degree in chemistry, physics, biochemistry or biology, preferably with post-doctoral training. Hands-on experience in developing NMR methods, maintaining and implementing hardware, in particular cryogenically cooled equipment, and/or in the analysis of data would be an advantage. Good social and communication skills will be expected. The ability to collaborate with both groups and contribute to create a good working atmosphere will be of prime importance to ensure lively scientific interactions. This position requires good knowledge of English in speech and writing.

The main deadlines for this recruitment are :
- June 4th to 28th, 2018: Applications by the candidates (check out the « concours externe du CNRS » website: https://www.dgdr.cnrs.fr/drhita/concoursita/)
- August 29th to September 09th, 2018: Invitations to interviews will be sent out ("Admissibilité des candidats")
- October 3rd to November 2nd, 2018: Interviews with the recruiting committee
- December 1st, 2018: Expected starting date

Interested candidates should contact Nicolas Giraud <nicolas.giraud@parisdescartes.fr> and/or Geoffrey Bodenhausen <Geoffrey.Bodenhausen@ens.fr>

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Friday, June 1, 2018

Multi-Frequency Pulsed Overhauser DNP at 1.2 Tesla #DNPNMR #ODNP

Schöps, Spindler Philipp, and Prisner Thomas, “Multi-Frequency Pulsed Overhauser DNP at 1.2 Tesla.”


Dynamic nuclear polarization (DNP) is a methodology to increase the sensitivity of nuclear magnetic resonance (NMR) spectroscopy. It relies on the transfer of the electron spin polarization from a radical to coupled nuclear spins, driven by microwave excitation resonant with the electron spin transitions. In this work we explore the potential of pulsed multi-frequency microwave excitation in liquids. Here, the relevant DNP mechanism is the Overhauser effect. The experiments were performed with TEMPOL radicals in aqueous solution at room temperature using a Q-band frequency (1.2 T) electron paramagnetic resonance (EPR) spectrometer combined with a Minispec NMR spectrometer. A fast arbitrary waveform generator (AWG) enabled the generation of multi-frequency pulses used to either sequentially or simultaneously excite all three 14N-hyperfine lines of the nitroxide radical. The multi-frequency excitation resulted in a doubling of the observed DNP enhancements compared to single-frequency microwave excitation. Q-band free induction decay (FID) signals of TEMPOL were measured as a function of the excitation pulse length allowing the efficiency of the electron spin manipulation by the microwave pulses to be extracted. Based on this knowledge we could quantitatively model our pulsed DNP enhancements at 1.2 T by numerical solution of the Bloch equations, including electron spin relaxation and experimental parameters. Our results are in good agreement with theoretical predictions. Whereas for a narrow and homogeneous single EPR line continuous wave excitation leads to more efficient DNP enhancements compared to pulsed excitation for the same amount of averaged microwave power. The situation is different for radicals with several hyperfine lines or in the presence of inhomogeneous line broadening. In such cases pulsed single/multi-frequency excitation can lead to larger DNP enhancements.

Wednesday, May 30, 2018

Unusual Local Molecular Motions in the Solid State Detected by Dynamic Nuclear Polarization Enhanced NMR Spectroscopy #DNPNMR

Hoffmann et al., “Unusual Local Molecular Motions in the Solid State Detected by Dynamic Nuclear Polarization Enhanced NMR Spectroscopy.”


Polyethylene glycol (PEG) and three related surfactants were studied by dynamic nuclear polarization (DNP) enhanced solid state NMR spectroscopy and differential scanning calorimetry (DSC). DNP enhanced solid state NMR surprisingly reveals the presence of local molecular motions that are normally understood to be inactive at temperatures ∼100 K. This surprising phenomenon could be explained by the experimentally necessary rapid freezing of the studied samples. Specifically, DSC shows that PEG 200 forms a glass upon freezing and that the three PEG-related surfactants are at least partially in a glass state or some other thermodynamic nonequilibrium state when rapidly frozen to the temperatures of the DNP enhanced solid state NMR experiments. This effect of preserving local molar motions by rapid freezing also holds true for solutions of organic solutes in the PEG 200 solvent matrix.

Monday, May 28, 2018

Dynamic Nuclear Polarization Signal Amplification as a Sensitive Probe for Specific Functionalization of Complex Paper Substrates #DNPNMR

Gutmann et al., “Dynamic Nuclear Polarization Signal Amplification as a Sensitive Probe for Specific Functionalization of Complex Paper Substrates.”


In this work, it is shown how solid-state NMR combined with dynamic nuclear polarization (DNP) can be employed as a powerful tool to selectively enhance the spectral intensity of functional groups on the surface of cellulose fibers in paper materials. As a model system, a poly(benzyl methacrylate) (PBEMA)-functionalized paper material is chosen that contains hydrophobic and hydrophilic domains. Detailed analysis of the DNP NMR data and of T1ρ data suggests that inhomogeneous 1H–1H spin diffusion is responsible for the observed differences in signal enhancement. These findings are fundamental for structural understanding of complex paper substrates for fluid transport or sensor materials.

Friday, May 25, 2018

Multi-Frequency Pulsed Overhauser DNP at 1.2 Tesla

Schöps, P., E. Spindler Philipp, and F. Prisner Thomas, Multi-Frequency Pulsed Overhauser DNP at 1.2 Tesla, in Z. Phys. Chem. 2017. p. 561.


Dynamic nuclear polarization (DNP) is a methodology to increase the sensitivity of nuclear magnetic resonance (NMR) spectroscopy. It relies on the transfer of the electron spin polarization from a radical to coupled nuclear spins, driven by microwave excitation resonant with the electron spin transitions. In this work we explore the potential of pulsed multi-frequency microwave excitation in liquids. Here, the relevant DNP mechanism is the Overhauser effect. The experiments were performed with TEMPOL radicals in aqueous solution at room temperature using a Q-band frequency (1.2 T) electron paramagnetic resonance (EPR) spectrometer combined with a Minispec NMR spectrometer. A fast arbitrary waveform generator (AWG) enabled the generation of multi-frequency pulses used to either sequentially or simultaneously excite all three 14N-hyperfine lines of the nitroxide radical. The multi-frequency excitation resulted in a doubling of the observed DNP enhancements compared to single-frequency microwave excitation. Q-band free induction decay (FID) signals of TEMPOL were measured as a function of the excitation pulse length allowing the efficiency of the electron spin manipulation by the microwave pulses to be extracted. Based on this knowledge we could quantitatively model our pulsed DNP enhancements at 1.2 T by numerical solution of the Bloch equations, including electron spin relaxation and experimental parameters. Our results are in good agreement with theoretical predictions. Whereas for a narrow and homogeneous single EPR line continuous wave excitation leads to more efficient DNP enhancements compared to pulsed excitation for the same amount of averaged microwave power. The situation is different for radicals with several hyperfine lines or in the presence of inhomogeneous line broadening. In such cases pulsed single/multi-frequency excitation can lead to larger DNP enhancements.

Wednesday, May 23, 2018

(13)C Dynamic Nuclear Polarization Using a Trimeric Gd(3+) Complex as an Additive #DNPNMR

Niedbalski, P., et al., (13)C Dynamic Nuclear Polarization Using a Trimeric Gd(3+) Complex as an Additive. J. Phys. Chem. A, 2017. 121(27): p. 5127-5135.


Dissolution dynamic nuclear polarization (DNP) is one of the most successful techniques that resolves the insensitivity problem in liquid-state nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) by amplifying the signal by several thousand-fold. One way to further improve the DNP signal is the inclusion of trace amounts of lanthanides in DNP samples doped with trityl OX063 free radical as the polarizing agent. In practice, stable monomeric gadolinium complexes such as Gd-DOTA or Gd-HP-DO3A are used as beneficial additives in DNP samples, further boosting the DNP-enhanced solid-state (13)C polarization by a factor of 2 or 3. Herein, we report on the use of a trimeric gadolinium complex as a dopant in (13)C DNP samples to improve the (13)C DNP signals in the solid-state at 3.35 T and 1.2 K and consequently, in the liquid-state at 9.4 T and 298 K after dissolution. Our results have shown that doping the (13)C DNP sample with a complex which holds three Gd(3+) ions led to an improvement of DNP-enhanced (13)C polarization by a factor of 3.4 in the solid-state, on par with those achieved using monomeric Gd(3+) complexes but only requires about one-fifth of the concentration. Upon dissolution, liquid-state (13)C NMR signal enhancements close to 20000-fold, approximately 3-fold the enhancement of the control samples, were recorded in the nearby 9.4 T high resolution NMR magnet at room temperature. Comparable reduction of (13)C spin-lattice T1 relaxation time was observed in the liquid-state after dissolution for both the monomeric and trimeric Gd(3+) complexes. Moreover, W-band electron paramagnetic resonance (EPR) data have revealed that 3-Gd doping significantly reduces the electron T1 of the trityl OX063 free radical, but produces negligible changes in the EPR spectrum, reminiscent of the results with monomeric Gd(3+)-complex doping. Our data suggest that the trimeric Gd(3+) complex is a highly beneficial additive in (13)C DNP samples and that its effect on DNP efficiency can be described in the context of the thermal mixing mechanism.

Monday, May 21, 2018

Improving Sensitivity of Solid-state NMR Spectroscopy by Rational Design of Polarizing Agents for Dynamic Nuclear Polarization #DNPNMR

Kubicki, D.J. and L. Emsley, Improving Sensitivity of Solid-state NMR Spectroscopy by Rational Design of Polarizing Agents for Dynamic Nuclear Polarization. Chimia (Aarau), 2017. 71(4): p. 190-194.


We review our recent efforts to optimize the efficiency of polarizing agents for Dynamic Nuclear Polarization (DNP) in solid-state MAS NMR spectroscopy. We elucidate the links between DNP performance, molecular structure and electronic relaxation properties of dinitroxide biradicals. We show that deuteration and increased bulkiness lead to slower electronic relaxation and in turn to higher DNP enhancements. We also show that the incorporation of solid dielectric particles into the sample is a general method of amplifying DNP enhancements by about a factor of two.

Friday, May 18, 2018

A radiofrequency system for in vivo hyperpolarized (13) C MRS experiments in mice with a 3T MRI clinical scanner

Giovannetti, G., et al., A radiofrequency system for in vivo hyperpolarized (13) C MRS experiments in mice with a 3T MRI clinical scanner. Scanning, 2016. 38(6): p. 710-719.


Hyperpolarized carbon-13 magnetic resonance spectroscopy (MRS) is a powerful tool to explore tissue metabolic state, by permitting the study of intermediary metabolism of biomolecules in vivo. However, a number of technological problems still limit this technology and need innovative solutions. In particular, the low molar concentration of derivate metabolites give rise to low signal-to-noise ratio (SNR), which makes the design and development of dedicated radiofrequency (RF) coils a fundamental task. In this article, the authors describe the simulation and the design of a RF coils configuration for MR experiments in mice, constituted by a (1) H whole body volume RF coil for imaging and a (13) C single circular loop surface RF coil for performing (13) C acquisitions. After the building, the RF system was employed in an in vivo experiment in a mouse injected with hyperpolarized [1-(13) C]pyruvate by using a 3 T clinical MR scanner. SCANNING 38:710-719, 2016. (c) 2016 Wiley Periodicals, Inc.

Wednesday, May 16, 2018

DNP-enhanced ultrawideline (207)Pb solid-state NMR spectroscopy: an application to cultural heritage science

Kobayashi, T., et al., DNP-enhanced ultrawideline (207)Pb solid-state NMR spectroscopy: an application to cultural heritage science. Dalton Trans, 2017. 46(11): p. 3535-3540. 


Dynamic nuclear polarization (DNP) is used to enhance the (ultra)wideline (207)Pb solid-state NMR spectra of lead compounds of relevance in the preservation of cultural heritage objects. The DNP SSNMR experiments enabled, for the first time, the detection of the basic lead carbonate phase of the lead white pigment by (207)Pb SSNMR spectroscopy. Variable-temperature experiments revealed that the short T'2 relaxation time of the basic lead carbonate phase hinders the acquisition of the NMR signal at room temperature. We additionally observe that the DNP enhancement is twice as large for lead palmitate (a lead soap, which is a degradation product implicated in the visible deterioration of lead-based oil paintings), than it is for the basic lead carbonate. This enhancement has allowed us to detect the formation of a lead soap in an aged paint film by (207)Pb SSNMR spectroscopy; which may aid in the detection of deterioration products in smaller samples removed from works of art.

Tuesday, May 15, 2018

[NMR] Postdoc in hyperpolarized NMR and MRI in the Theis lab at NC State University and close collaboration with Duke University



Dear colleagues,

A postdoctoral position is opening in the Theis lab at the North Carolina State University. The focus of the position will be on development and applications of hyperpolarization technology. In a highly interdisciplinary and collaborative environment we will be advancing parahydrogen induced polarization techniques towards applications in biomolecular structure elucidation, miniaturized NMR, and molecular imaging. Novel hyperpolarized markers and detection schemes will be developed, tested and applied. The position also involves a close collaboration with the Warren lab at Duke University.

We offer access to parahydrogen hyperpolarizers (Duke and NCSU) and dissolution-DNP instrumentation (hypersense at Duke). The hyperpolarizers are installed next to imagers (7T and 1T) and NMR spectrometers (400 MHz). Schemes for optical detection of hyperpolarized signals with sensitive magnetometers will be designed and installed at NCSU. 

At NCSU METRIC (The Molecular Education, Technology and Research Innovation Center) gives access to the following NMR devices in addition to state-of-the-art mass spectrometry and X-Ray Crystallography instrumentation: 

  • Bruker Avance NEO 400 MHz NMR, RT BBO iProbe, VT, and SampleXpress Automatic Sample Changer
  • Bruker Avance NEO 500 MHz NMR, BBO PRODIGY LN2 -Cryoprobe, VT, and SampleCASE automatic Sample Changer
  • Bruker Avance NEO 600 MHz NMR, RT BBO Smart Probe and TXI 1H-13C/15N- 2H Probe, VT, and SampleXpress Automatic Sample Changer
  • Bruker Avance NEO 700 MHz NMR, TCI 1H/19F-13C/15N- 2H LHe Cryoprobe, TXI 1H-13C/15N- 2H Probe, VT, and SampleXPress Automatic Sample Changer
  • Bruker Avance III 700 MHz NMR, TCI 1H-13C/15N- 2H LHe CryoProbe, TXI 1H-13C/15N- 2HProbe, VT, and SampleXpress Automatic Sample Changer
  • Varian Mercury 400 MHz NMR, VT, 5mm ASW 4-nuclei 1H/19F/13C/31P Probe
  • Varian Inova 400 MHz NMR, VT, 5 mm PFG gradient 4-nuclei Probe (1H/19F/13C/31P)
  • Varian Mercury 300 MHz NMR, 5 mm ID Probe (1H/13C)
  • Varian Mercury Plus 300 MHz NMR, 5mm PFG 4-nuclei Probe
  • E500-10/12 EPR System with Digital High-Resolution Hall Field Controller and Dual Channel Signal Processing UnitFurthermore, we offer many collaborations across the Triangle (UNC, Duke, NC State), the US and Europe, and extended opportunities to travel for collaborations and attending conferences. 
The preferred candidate is a highly motivated and collaborative individual with expertise in magnetic resonance technologies and experimental design. Experience with hyperpolarization technologies, imaging and programming are a plus.

Candidates with a strong background in chemical synthesis that wish to broaden their skill-set by combining their strength in chemical design with innovative molecular imaging and spectroscopy approaches are also encouraged to apply. 


For more details please email ttheis@ncsu.edu or see:
The Theis lab is located on the modern centennial campus at NCSU. See: https://centennial.ncsu.edu/
To apply, please send CV/resume with contact information for 2 references to: ttheis@ncsu.edu

_________________________________
Thomas Theis, Ph.D.

Assistant Professor of Chemistry
North Carolina State University 

Adjunct at Duke University, Department of Chemistry 




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