Wednesday, December 24, 2014

Blogging Break

Hi everyone, I will take a break blogging over the the holiday season. The next blog post will be published January 5th.

Hope you all enjoy the Holiday Season.
Cheers, Thorsten


Friday, December 19, 2014

Drug Screening Boosted by Hyperpolarized Long-Lived States in NMR


Buratto, R., et al., Drug Screening Boosted by Hyperpolarized Long-Lived States in NMR. ChemMedChem, 2014. 9(11): p. 2509-2515.


Transverse and longitudinal relaxation times (T1ρ and T1) have been widely exploited in NMR to probe the binding of ligands and putative drugs to target proteins. We have shown recently that long-lived states (LLS) can be more sensitive to ligand binding. LLS can be excited if the ligand comprises at least two coupled spins. Herein we broaden the scope of ligand screening by LLS to arbitrary ligands by covalent attachment of a functional group, which comprises a pair of coupled protons that are isolated from neighboring magnetic nuclei. The resulting functionalized ligands have longitudinal relaxation times T1(1H) that are sufficiently long to allow the powerful combination of LLS with dissolution dynamic nuclear polarization (D-DNP). Hyperpolarized weak “spy ligands” can be displaced by high-affinity competitors. Hyperpolarized LLS allow one to decrease both protein and ligand concentrations to micromolar levels and to significantly increase sample throughput.

Wednesday, December 17, 2014

Long-Lived States of Magnetically Equivalent Spins Populated by Dissolution-DNP and Revealed by Enzymatic Reactions


Bornet, A., et al., Long-Lived States of Magnetically Equivalent Spins Populated by Dissolution-DNP and Revealed by Enzymatic Reactions. Chemistry, 2014. 20(51): p. 17113-8.


Hyperpolarization by dissolution dynamic nuclear polarization (D-DNP) offers a way of enhancing NMR signals by up to five orders of magnitude in metabolites and other small molecules. Nevertheless, the lifetime of hyperpolarization is inexorably limited, as it decays toward thermal equilibrium with the nuclear spin-lattice relaxation time. This lifetime can be extended by storing the hyperpolarization in the form of long-lived states (LLS) that are immune to most dominant relaxation mechanisms. Levitt and co-workers have shown how LLS can be prepared for a pair of inequivalent spins by D-DNP. Here, we demonstrate that this approach can also be applied to magnetically equivalent pairs of spins such as the two protons of fumarate, which can have very long LLS lifetimes. As in the case of para-hydrogen, these hyperpolarized equivalent LLS (HELLS) are not magnetically active. However, a chemical reaction such as the enzymatic conversion of fumarate into malate can break the magnetic equivalence and reveal intense NMR signals.

5th International DNP Symposium

I'm very excited to see that the 5th International DNP Symposium will be held from August 31st to September 4th, 2015 in Egmond aan Zee, The Netherlands.

The following speakers have confirmed to give a plenary lecture:

Jan Henrik Ardenkjaer-Larsen (Technical University of Denmark)
Geoffrey Bodenhausen (EPFL Lausanne & ENS Paris)
Kevin Brindle (University of Cambridge)
Robert G. Griffin (MIT)
Olivier Lafon (University of Lille)
Songi Han (UC Santa Barbara)
Malcolm Levitt (University of Southampton)
Robert Kaptein (Utrecht University)

Registration will be opening in early 2015. For more information please visit: http://www.nmr-nl.org/hyperpolarizedMR

Monday, December 15, 2014

In Situ and Ex Situ Low-Field NMR Spectroscopy and MRI Endowed by SABRE Hyperpolarization


Barskiy, D.A., et al., In Situ and Ex Situ Low-Field NMR Spectroscopy and MRI Endowed by SABRE Hyperpolarization. ChemPhysChem, 2014. 15(18): p. 4100-7.


By using 5.75 and 47.5 mT nuclear magnetic resonance (NMR) spectroscopy, up to 10(5) -fold sensitivity enhancement through signal amplification by reversible exchange (SABRE) was enabled, and subsecond temporal resolution was used to monitor an exchange reaction that resulted in the buildup and decay of hyperpolarized species after parahydrogen bubbling. We demonstrated the high-resolution low-field proton magnetic resonance imaging (MRI) of pyridine in a 47.5 mT magnetic field endowed by SABRE. Molecular imaging (i.e. imaging of dilute hyperpolarized substances rather than the bulk medium) was conducted in two regimes: in situ real-time MRI of the reaction mixture (in which pyridine was hyperpolarized), and ex situ MRI (in which hyperpolarization decays) of the liquid hyperpolarized product. Low-field (milli-Tesla range, e.g. 5.75 and 47.5 mT used in this study) parahydrogen-enhanced NMR and MRI, which are free from the limitations of high-field magnetic resonance (including susceptibility-induced gradients of the static magnetic field at phase interfaces), potentially enables new imaging applications as well as differentiation of hyperpolarized chemical species on demand by exploiting spin manipulations with static and alternating magnetic fields.

Friday, December 12, 2014

Hyperpolarized cesium ions doped in a glass material


Ishikawa, K., Hyperpolarized cesium ions doped in a glass material. J Magn Reson, 2014. 249C(0): p. 94-99.


Hyperpolarized (HP) 133Cs nuclear magnetic resonance signals were measured from borosilicate glass cell walls during optical pumping of cesium vapor at high magnetic field (9.4T). Significant signal enhancements were observed when additional heating of the cell wall was provided by intense but non-resonant laser irradiation, with integrated HP 133Cs NMR signals and line widths varying as a function of heating laser power (and hence glass temperature). Given that virtually no Cs ions would originally be present in the glass, absorbed HP Cs atoms rarely met thermally-polarized Cs ions already at the surface; thus, spin-exchange via nuclear dipole interaction cannot be the primary mechanism for injecting spin polarization into the glass. Instead, it is concluded that the absorption and transport of HP atoms into the glass material itself is the dominant mechanism of nuclear spin injection at high temperatures-the first reported experimental demonstration of such a mechanism.

Wednesday, December 10, 2014

Dipolar induced Para-Hydrogen-Induced Polarization


Buntkowsky, G., et al., Dipolar induced Para-Hydrogen-Induced Polarization. Solid State Nucl Magn Reson, 2014. 63-64(0): p. 20-9.


Analytical expressions for the signal enhancement in solid-state PHIP NMR spectroscopy mediated by homonuclear dipolar interactions and single pulse or spin-echo excitation are developed and simulated numerically. It is shown that an efficient enhancement of the proton NMR signal in solid-state NMR studies of chemisorbed hydrogen on surfaces is possible. Employing typical reaction efficacy, enhancement-factors of ca. 30-40 can be expected both under ALTADENA and under PASADENA conditions. This result has important consequences for the practical application of the method, since it potentially allows the design of an in-situ flow setup, where the para-hydrogen is adsorbed and desorbed from catalyst surfaces inside the NMR magnet.

Monday, December 8, 2014

Postdoc position available in Solid-State NMR at Stockholm University

From the Ampere Magnetic Resonance List


Postdoctoral Researcher Position in Solid-State NMR at Stockholm University

at the Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, Sweden

The Department of Materials and Environmental Chemistry (MMK) at Stockholm University is internationally renowned for developing and characterizing properties and structures of modern materials, where solid-state NMR represents one of the characterization techniques. The solid-state NMR instrumentation at MMK includes two wide-bore magnets (9.4 T and 14.1 T) with triple-channel Bruker Avance-III spectrometers and a multitude of MAS probeheads. The solid-state NMR research at MMK is focused on developing and applying solid-state NMR spectroscopy techniques for structural investigations of structurally disordered inorganic materials, in particular glasses and porous materials.

Project Description
We are inviting a self-motivated and creative individual to apply for one postdoctoral opening that involves developing new MAS NMR methodology for determining internuclear distances among spins-1/2 as well as among half-integer spins within multi-spin networks. The techniques will be applied to structurally disordered materials, such as aluminosilicate glasses, bioactive silicate glasses, and bone. The successful candidate will be collaborating with researchers responsible for computer modeling (e.g., MD simulations) and other structural characterization techniques.
Examples of recent publications relevant to the project:
[1] Low-Power Broadband Homonuclear Dipolar Recoupling without Decoupling: Double-Quantum 13C NMR Correlations at Very Fast Magic-Angle Spinning, G. Teymoori, B. Pahari, B. Stevensson and M. Edén, Chem. Phys., Lett., 547, 103-109 (2012)

[2] Multiple-Quantum Spin Counting in Magic-Angle Spinning NMR via Low-Power Symmetry-Based Dipolar Recoupling, G. Teymoori, B. Pahari, E. Viswanathan and M. Edén, J. Magn. Reson, 236, 31-40 (2013)

[3] Central-Transition Double-Quantum Sideband NMR Spectroscopy of Half-Integer Quadrupolar Nuclei: Estimating Internuclear Distances and Probing Clusters within Multi-Spin Network, A. Brinkmann and M. Edén, Phys. Chem. Chem. Phys, 16, 7037-7050 (2014)

Eligibility & Selection Criteria
The applicant should have a PhD degree in Chemistry or Physics (or equivalent thereof) and significant experience in MAS NMR experimentation. The selection is based primarily on scientific excellence in the field of MAS NMR: previous experience with developing and utilizing advanced solid-state NMR techniques, and/or NMR theory development is required and should be documented in the application. Previous experience with Bruker Avance spectrometers and/or experience with NMR on quadrupolar nuclei are considered advantageous. Skills in computer programming will be beneficial, but not necessary. Please do not apply if you lack experience with solid-state NMR.

Conditions of employment
The position involves a full time employment for 12 months, with the possibility of further extension up to 24 months. The financial support is through a stipend (free of tax) of 20 000 SEK/month. The position is to be filled the soonest possible, with an intended starting date from February 2015 (the precise date is negotiable). Reviewing of the applications will begin immediately and proceed until the position is filled.

Additional Information
Further information about the Department of Materials and Environmental Chemistry may be found at http://www.mmk.su.se/.

Further info about the PI: http://www.mmk.su.se/page.php?pid=155&id=220

For inquiries, please contact Professor Mattias Edén: mattias.eden@mmk.su.se

Application

The application should be written in English and must include
  • Letter of interest with a description of research interests and previous experience with solid-state NMR, relevant for the present position.
  • CV and publication list
  • copies of diploma of scientific degrees and transcripts of academic records
  • the contact information of at least two references
Please send your application by email as a single pdf file to: mattias.eden@mmk.su.se, with the reference “SU-POSTDOC NMR” in the subject line. Reviewing of the applications will begin immediately and proceed until the position is filled.

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Cavity- and waveguide-resonators in electron paramagnetic resonance, nuclear magnetic resonance, and magnetic resonance imaging


This is a very nice review of cavities that are used in EPR, NMR and MRI. So far resonators have not been widely employed in DNP spectroscopy - only in some static DNP experiments. However, it is an intriguing problem that could, if solved, allow using cost-effective solid-state sources for DNP even at high temperatures.
Even if this article is not specifically about resonators for DNP it gives a very nice overview of the concepts that drive resonator design for magnetic resonance applications.



Webb, A., Cavity- and waveguide-resonators in electron paramagnetic resonance, nuclear magnetic resonance, and magnetic resonance imaging. Prog Nucl Magn Reson Spectrosc, 2014. 83C: p. 1-20.


Cavity resonators are widely used in electron paramagnetic resonance, very high field magnetic resonance microimaging and also in high field human imaging. The basic principles and designs of different forms of cavity resonators including rectangular, cylindrical, re-entrant, cavity magnetrons, toroidal cavities and dielectric resonators are reviewed. Applications in EPR and MRI are summarized, and finally the topic of traveling wave MRI using the magnet bore as a waveguide is discussed.

Friday, December 5, 2014

Dynamic nuclear polarization and Hanle effect in (In,Ga)As/GaAs quantum dots. Role of nuclear spin fluctuations


Gerlovin, I.Y., et al., Dynamic nuclear polarization and Hanle effect in (In,Ga)As/GaAs quantum dots. Role of nuclear spin fluctuations. AIP Conference Proceedings, 2013. 1566(1): p. 319-320.


The degree of circular polarization of photoluminescence of (In,Ga)As quantum dots as a function of magnetic field applied perpendicular to the optical axis (Hanle effect) is experimentally studied. The measurements have been performed at various regimes of the optical excitation modulation. The analysis of experimental data has been performed in the framework of a vector model of regular nuclear spin polarization and its fluctuations. The analysis allowed us to evaluate the magnitude of nuclear polarization and its dynamics at the experimental conditions used.

Wednesday, December 3, 2014

L-band Overhauser dynamic nuclear polarization

I must have missed that article from 2010, describing L-Band ODNP experiments. This actually looks like a very nice setup that could be used for teaching purposes.


Garcia, S., et al., L-band Overhauser dynamic nuclear polarization. J Magn Reson, 2010. 203(1): p. 138-43.


We present the development of an Overhauser dynamic nuclear polarization (DNP) instrument at 0.04 T using 1.1 GHz (L-band) electron spin resonance frequencies (ESR) and 1.7 MHz (1)H nuclear magnetic resonance frequencies. Using this home-built DNP system, the electron-nucleus coupling factor of 4-oxo-TEMPO dissolved in water was determined as 0.39+/-0.06 at 0.04 T. The higher coupling factor obtained at this field compared to higher magnetic fields, such as 0.35 T, directly translates to higher enhancement of the NMR signal and opens up a wider time scale window for observing water dynamics interacting with macromolecular systems, including proteins, polymers or lipid vesicles. The higher enhancements obtained will facilitate the observation of water dynamics at correlation times up to 10 ns, that corresponds to more than one order of magnitude slower dynamics than accessible at 0.35 T using X-band ESR frequencies.