Wednesday, April 30, 2014

The Role of the Interaction Frame in the Theoretical Description of Solid Effect Dynamic Nuclear Polarization


Kwiatkowski, G., A. Karabanov, and W. Köckenberger, The Role of the Interaction Frame in the Theoretical Description of Solid Effect Dynamic Nuclear Polarization. Israel Journal of Chemistry, 2014. 54(1-2): p. 184-195.


The enhancement of the nuclear spin polarization generated by dynamic nuclear polarization depends on two competing processes: the perturbation of the thermal equilibrium by the applied microwave field and the tendency of relaxation processes to re-establish the thermal state. Hence, it is important to correctly incorporate relaxation processes in the theoretical description of dynamic nuclear polarization to obtain meaningful simulations. A difficulty arises in the choice of the correct interaction frame when building an appropriate relaxation superoperator. In the Zeeman frame, the rate constants introduced to define longitudinal and transverse relaxation can become mixed if the non-secular part of the hyperfine interaction between an electron in a paramagnetic centre and the nuclear spins is strong. Deriving the relaxation superoperator in the interaction frame that is defined by the eigenbasis of the stationary Hamiltonian eliminates this issue. However, when using this strategy, not all the non-secular terms arising in a relaxation model based on local magnetic field fluctuations are taken properly into account if dipolar interactions between nuclear spins dominate over hyperfine interactions. An analytical treatment of this problem is presented that is corroborated by a set of numerical simulations focussing on the case of solid effect dynamic nuclear polarization. The advantage and possible errors arising when using either of the two strategies are briefly summarised and discussed.

Monday, April 28, 2014

High magnetic field science and its application in the United States: A magnetic resonance perspective


Frydman, L., High magnetic field science and its application in the United States: A magnetic resonance perspective. J Magn Reson, 2014(0).


High-field magnets have become an important research tool in many scientific disciplines. Originally developed for studying the characteristics of materials under extreme conditions, they have increasingly been used by other disciplines, including biology, chemistry, and geology, and have found applications beyond basic science, serving many applied fields from medicine to the petroleum industry. At the request of the United States National Science Foundation, the U.S. National Research Council (NRC) established a committee in the spring of 2012 called the ‘‘Committee to Assess the Current Status and Future Direction of High Magnetic Field Science in the United States’’. This group of Academy-level experts was asked to assess the needs of the U.S. research community in particular – and of the global research community in general – for high magnetic fields.

Friday, April 25, 2014

Dynamic nuclear polarization with photoexcited triplet electrons in a glassy matrix


Tateishi, K., et al., Dynamic nuclear polarization with photoexcited triplet electrons in a glassy matrix. Angew Chem Int Ed Engl, 2013. 52(50): p. 13307-10.


NMR spectroscopy and MRI are powerful methods for the non-destructive analysis of microscopic structures inside bulk materials and human bodies. As a method to enhance their sensitivities, dynamic nuclear polarization (DNP) has attracted great attention. The intensity of a signal from nuclear spins is proportional to the spin polarization. In magnetic fields conventionally used for NMR spectroscopy and MRI, thermal polarization of nuclear spins at room temperature is in the order of 10􏰵5 or less. DNP is a means of transferring spin polarization from electrons to nuclei.[1] The thermal polarization of electron spins is 660 times larger than that of 1H spins, and therefore, DNP can enhance the 1H spin polarization (hence the sensitivity) by a factor of at most 660.

Wednesday, April 23, 2014

Towards structure determination of self-assembled peptides using dynamic nuclear polarization enhanced solid-state NMR spectroscopy


Takahashi, H., et al., Towards structure determination of self-assembled peptides using dynamic nuclear polarization enhanced solid-state NMR spectroscopy. Angew Chem Int Ed Engl, 2013. 52(27): p. 6979-82.


Bio-inspired self-assemblies made of peptide building blocks have great potential for nanotechnology ranging from biological and pharmaceutical applications to (opto)electronics. With these goals, a variety of peptide nanoassemblies have been studied and designed over the last few decades. Inevitably, structural studies at an atomic scale are crucial to unravel the mechanisms that drive nanoassembly formation as well as to relate these structures to their physical and chemical properties. However, structure determination at an atomic level is challenging essentially because of the difficulty associated with using X-ray crystallography on such nanoassemblies.

Friday, April 18, 2014

Heteronuclear Cross-Relaxation Effects in the NMR Spectroscopy of Hyperpolarized Targets


Donovan, K.J., A. Lupulescu, and L. Frydman, Heteronuclear Cross-Relaxation Effects in the NMR Spectroscopy of Hyperpolarized Targets. ChemPhysChem, 2014. 15(3): p. 436-443.


Dissolution dynamic nuclear polarization (DNP) enables high-sensitivity solution-phase NMR experiments on long-lived nuclear spin species such as (15)N and (13)C. This report explores certain features arising in solution-state (1)H NMR upon polarizing low-gamma nuclear species. Following solid-state hyperpolarization of both (13)C and (1)H, solution-phase (1)H NMR experiments on dissolved samples revealed transient effects, whereby peaks arising from protons bonded to the naturally occurring (13)C nuclei appeared larger than the typically dominant (12)C-bonded (1)H resonances. This enhancement of the satellite peaks was examined in detail with respect to a variety of mechanisms that could potentially explain this observation. Both two- and three-spin phenomena active in the solid state could lead to this kind of effect; still, experimental observations revealed that the enhancement originates from (13)C-->(1)H polarization-transfer processes active in the liquid state. Kinetic equations based on modified heteronuclear cross-relaxation models were examined, and found to well describe the distinct patterns of growth and decay shown by the (13)C-bound (1)H NMR satellite resonances. The dynamics of these novel cross-relaxation phenomena were determined, and their potential usefulness as tools for investigating hyperpolarized ensembles and for obtaining enhanced-sensitivity (1)H NMR traces was explored.

Wednesday, April 16, 2014

Level Anti-Crossings are a Key Factor for Understanding para-Hydrogen-Induced Hyperpolarization in SABRE Experiments


Pravdivtsev, A.N., et al., Level Anti-Crossings are a Key Factor for Understanding para-Hydrogen-Induced Hyperpolarization in SABRE Experiments. ChemPhysChem, 2013. 14(14): p. 3327-3331.


Various hyperpolarization methods are able to enhance the sensitivity of nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) by several orders of magnitude. Among these methods are para-hydrogen-induced polarization (PHIP) and signal amplification by reversible exchange (SABRE), which exploit the strong nuclear alignment of para-hydrogen. Several SABRE experiments have been reported but, so far, it has not been possible to account for the experimentally observed sign and magnetic-field dependence of substrate polarization. Herein, we present an analysis based on level anti-crossings (LACs), which provides a complete understanding of the SABRE effect. The field-dependence of both net and anti-phase polarization is measured for several ligands, which can be reproduced by the theory. The similar SABRE field-dependence for different ligands is also explained. In general, the LAC concept allows complex spin dynamics to be unraveled, and is crucial for optimizing the performance of novel hyperpolarization methods in NMR and MRI techniques.

Monday, April 14, 2014

Parahydrogen-induced polarization transfer to 19F in perfluorocarbons for 19F NMR spectroscopy and MRI


Plaumann, M., et al., Parahydrogen-induced polarization transfer to 19F in perfluorocarbons for 19F NMR spectroscopy and MRI. Chemistry, 2013. 19(20): p. 6334-9.


Fluorinated substances are important in chemistry, industry, and the life sciences. In a new approach, parahydrogen-induced polarization (PHIP) is applied to enhance (19)F MR signals of (perfluoro-n-hexyl)ethene and (perfluoro-n-hexyl)ethane. Unexpectedly, the end-standing CF3 group exhibits the highest amount of polarization despite the negligible coupling to the added protons. To clarify this non-intuitive distribution of polarization, signal enhancements in deuterated chloroform and acetone were compared and (19)F-(19)F NOESY spectra, as well as (19)F T1 values were measured by NMR spectroscopy. By using the well separated and enhanced signal of the CF3 group, first (19)F MR images of hyperpolarized linear semifluorinated alkenes were recorded.

Friday, April 11, 2014

Dynamic Nuclear Polarization NMR Spectroscopy: Revealing Multiple Conformations in Lipid-Anchored Peptide Vaccines


Koers, E.J., et al., Dynamic Nuclear Polarization NMR Spectroscopy: Revealing Multiple Conformations in Lipid-Anchored Peptide Vaccines. Angew Chem Int Ed Engl, 2013. 52(41): p. 10905-10908.


Sensitivity is the key: Dynamic nuclear polarization NMR spectroscopy provides structural information on liposomal vaccines targeting Alzheimer's disease. DMPC/DMPG/Cholesterol mainly stabilizes extended structures of the lipid-anchored peptide, while in DMTAP/Cholesterol liposomes the peptide adopts a multitude of conformations including random-coil and extended structures.

Wednesday, April 9, 2014

Staff scientist position at King Abdullah University of Science and Technology, Saudi Arabia

From the Ampere Magnetic Resonance List

DNP/EPR Staff Scientist for Bruker AVANCE 400 DNP NMR system and EMX plus EPR system
at King Abdullah University of Science and Technology, Saudi Arabia


Job Title
Staff Scientist for NMR lab 

Outline
King Abdullah University of Science and Technology  (KAUST) is a globally renowned graduate research university that makes significant contributions to scientific and technological advancement.  NMR core lab is a part of Nanofabrication, Imaging & Characterization Lab  (ANIC) with ten NMR and MRI up to 950 MHz.  It is dedicated to providing the instrumentation, technical expertise, and team-teaching environment to stimulate collaborative research. 

Major Responsibilities
User (students, researchers and faculties) training/support and instruments management of DNP (Dynamic Nuclear Polarization) NMR and EPR (Electron Paramagnetic Resonance)

Technical Skills
Candidate should be expert on Bruker NMR system software and hardware.  The experience of DNP NMR is recommended and the experience of solid state NMR and EPR will be positive.

Required Education
Ph.D degree or master degree in solid state NMR or EPR with material sciences major.


Organization, Division
NMR Core Lab Facilities (http://anic.kaust.edu.sa/Pages/Nuclear-Magnetic-Resonance.aspx) at King Abdullah University of Science and Technology (http://www.kaust.edu.sa) Thuwal, Kingdom of Saudi Arabia

Contact Person
Dr. Kazuo Yamauchi (kazuo.yamauchi@kaust.edu.sa),  group leader of NMR lab
Dr. Kun Li (kun.li@kaust.edu.sa),  manager of core lab



====================================
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NMR web database:

Annual Meeting COST EUROHYPERPOL Zurich, June 27-29

From the Amper Magnetic Resonance List:


Dear colleagues,

the annual meeting of the COST action TD1103 "European Network for Hyperpola-
rization Physics and Methodology in NMR and MRI" (http://www.eurohyperpol.eu)
will take place before the EUROMAR 2014 in Zurich from June 27-29. The COST
action tries to bring together researcher working on various aspects of
hyperpolarization techniques (DNP, PHIP, SEOP, CIDNP) from fundamental
research to applications.

The annual meeting will start with a tutorial session covering the various
methods of hyperpolarization and a few plenary talks. The main focus of the
meeting will be on the working groups that are organized by the working group
be a poster session on Friday evening. A prelimnary program can be found on
the EUROMAR 2014 webpage (http://euromar2014.org/index.php?cost) which will
be updated as more details become available.

The COST action can provide funding for early-stage researchers (PhD students
and postdocs) that give an oral presentation in one of the working-group
sessions or present a poster. Only one researcher per research group can be
supported. Requests for funding require submission of a poster abstract or
an abstract for an oral presentation that has been approved by the WG leader.
Abstracts (in MS Word format) as well as contact information should be sent by
email to cost2014@nmr.phys.chem.ethz.ch. Registration and abstracts have to
be received before April 30 to be considered for funding.

Registration is now open through the EUROMAR webpage (http://euromar2014.org).
The registration fee is Euro 50.- which covers mostly coffee, lunches, and
other organizational expenses.

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                |

+----------------------------------------+-----------------------------------+

Real-time DNP NMR observations of acetic acid uptake, intracellular acidification, and of consequences for glycolysis and alcoholic fermentation in yeast


Jensen, P.R., et al., Real-time DNP NMR observations of acetic acid uptake, intracellular acidification, and of consequences for glycolysis and alcoholic fermentation in yeast. Chemistry, 2013. 19(40): p. 13288-93.


Uptake and upshot in vivo: Straightforward methods that permit the real-time observation of organic acid influx, intracellular acidification, and concomitant effects on cellular-reaction networks are crucial for improved bioprocess monitoring and control. Herein, dynamic nuclear polarization (DNP) NMR is used to observe acetate influx, ensuing intracellular acidification and the metabolic consequences on alcoholic fermentation and glycolysis in living cells.

Monday, April 7, 2014

Protein folding studied by dissolution dynamic nuclear polarization


Chen, H.Y., M. Ragavan, and C. Hilty, Protein folding studied by dissolution dynamic nuclear polarization. Angew Chem Int Ed Engl, 2013. 52(35): p. 9192-5.


Protein folding occurs on a timescale that is not directly observable with most traditional nuclear magnetic resonance (NMR) spectroscopy methods.[1, 2] The insights into this complex process that can potentially be gained from the high site resolution of NMR has led to developments such as stopped-flow NMR,[3] incorporation of specific isotope labels,[4] and pulse sequences tailored for rapid data acquisition.[5] Hyperpolarization, the generation of a non-equilibrium spin state, shows significant promise to enhance the sensitivity and, by removing the need for signal averaging, dramatically decrease signal acquisition time.[6, 7] For the study of protein folding, chemically induced dynamic nuclear polarization (CIDNP) has been used to hyperpolarize tryptophan residues that undergo a cyclic reaction with a photosensitizer.[8] A different technique, dynamic nuclear polarization (DNP),[9] hyperpolarizes nuclei throughout a molecule via an admixed stable free radical. Combined with solid state NMR, DNP provides unique information on protein structure.[10] Using dissolution DNP,[11] NMR in the liquid state would be sensitive to structural changes across the entire macromolecule during the folding process. Liquid-state NMR signals of a DNP hyperpolarized, denatured protein, the ribosomal protein L23,[12, 13] have recently been observed.[14]

Friday, April 4, 2014

Topical Developments in High-Field Dynamic Nuclear Polarization


Michaelis, V.K., et al., Topical Developments in High-Field Dynamic Nuclear Polarization. Israel Journal of Chemistry, 2014. 54(1-2): p. 207-221.


We report our recent efforts directed at improving high-field dynamic nuclear polarization (DNP) experiments. We investigated a series of thiourea nitroxide radicals and the associated DNP enhancements ranging from ε=25 to 82, which demonstrate the impact of molecular structure on performance. We directly polarized low-gamma nuclei, including 13C, 2H, and 17O, by the cross effect mechanism using trityl radicals as a polarization agent. We discuss a variety of sample preparation techniques for DNP with emphasis on the benefits of methods that do not use a glass-forming cryoprotecting matrix. Lastly, we describe a corrugated waveguide for use in a 700 MHz/460 GHz DNP system that improves microwave delivery and increases enhancements up to 50 %.

Wednesday, April 2, 2014

Hyperpolarization of deuterated metabolites via remote cross-polarization and dissolution dynamic nuclear polarization


Vuichoud, B., et al., Hyperpolarization of deuterated metabolites via remote cross-polarization and dissolution dynamic nuclear polarization. J Phys Chem B, 2014. 118(5): p. 1411-5.


In deuterated molecules such as [1-(13)C]pyruvate-d3, the nuclear spin polarization of (13)C nuclei can be enhanced by combining Hartmann-Hahn cross-polarization (CP) at low temperatures (1.2 K) with dissolution dynamic nuclear polarization (D-DNP). The polarization is transferred from remote solvent protons to the (13)C spins of interest. This allows one not only to slightly reduce build-up times but also to increase polarization levels and extend the lifetimes T1((13)C) of the enhanced (13)C polarization during and after transfer from the polarizer to the NMR or MRI system. This extends time scales over which metabolic processes and chemical reactions can be monitored.