Monday, December 30, 2013

Solid-Phase Polarization Matrixes for Dynamic Nuclear Polarization from Homogeneously Distributed Radicals in Mesostructured Hybrid Silica Materials


Gajan, D., et al., Solid-Phase Polarization Matrixes for Dynamic Nuclear Polarization from Homogeneously Distributed Radicals in Mesostructured Hybrid Silica Materials. J. Am. Chem. Soc., 2013. 135(41): p. 15459-15466.


Mesoporous hybrid silica?organic materials containing homogeneously distributed stable mono- or dinitroxide radicals covalently bound to the silica surface were developed as polarization matrixes for solid-state dynamic nuclear polarization (DNP) NMR experiments. For TEMPO-containing materials impregnated with water or 1,1,2,2-tetrachloroethane, enhancement factors of up to 36 were obtained at ?100 K and 9.4 T without the need for a glass-forming additive. We show that the homogeneous radical distribution and the subtle balance between the concentration of radical in the material and the fraction of radicals at a sufficient inter-radical distance to promote the cross-effect are the main determinants for the DNP enhancements we obtain. The material, as well as an analogue containing the poorly soluble biradical bTUrea, is used as a polarizing matrix for DNP NMR experiments of solutions containing alanine and pyruvic acid. The analyte is separated from the polarization matrix by simple filtration.

Friday, December 27, 2013

Magic-Angle Spinning NMR of Cold Samples

Solid-state DNP experiments are often performed at cryogenic temperatures and this article is an excellent review about the current technologies to spin samples at (very) low temperatures.

ConcistrÈ, M., et al., Magic-Angle Spinning NMR of Cold Samples. Acc. Chem. Res., 2013.


Magic-angle-spinning solid-state NMR provides site-resolved structural and chemical information about molecules that complements many other physical techniques. Recent technical advances have made it possible to perform magic-angle-spinning NMR experiments at low temperatures, allowing researchers to trap reaction intermediates and to perform site-resolved studies of low-temperature physical phenomena such as quantum rotations, quantum tunneling, ortho-para conversion between spin isomers, and superconductivity. In examining biological molecules, the improved sensitivity provided by cryogenic NMR facilitates the study of protein assembly or membrane proteins. The combination of low-temperatures with dynamic nuclear polarization has the potential to boost sensitivity even further. Many research groups, including ours, have addressed the technical challenges and developed hardware for magic-angle-spinning of samples cooled down to a few tens of degrees Kelvin. In this Account, we briefly describe these hardware developments and review several recent activities of our group which involve low-temperature magic-angle-spinning NMR. Low-temperature operation allows us to trap intermediates that cannot be studied under ambient conditions by NMR because of their short lifetime. We have used low-temperature NMR to study the electronic structure of bathorhodopsin, the primary photoproduct of the light-sensitive membrane protein, rhodopsin. This project used a custom-built NMR probe that allows low-temperature NMR in the presence of illumination (the image shows the illuminated spinner module). We have also used this technique to study the behavior of molecules within a restricted environment. Small-molecule endofullerenes are interesting molecular systems in which molecular rotors are confined to a well-insulated, well-defined, and highly symmetric environment. We discuss how cryogenic solid state NMR can give information on the dynamics of ortho-water confined in a fullerene cage. Molecular motions are often connected with fundamental chemical properties; therefore, an understanding of molecular dynamics can be important in fields ranging from material science to biochemistry. We present the case of ibuprofen sodium salt which exhibits different degrees of conformational freedom in different parts of the same molecule, leading to a range of line broadening and line narrowing phenomena as a function of temperature.

Monday, December 23, 2013

SedNMR: On the Edge between Solution and Solid-State NMR


Sedimented samples (states) can be described as a "microcrystaline glass", which provide a new approach for the preparation of DNP samples. This was described in a post this year you can find here (http://blog.bridge12.com/2013/02/dynamic-nuclear-polarization-of.html).

The following article gives more details about the approach.



Bertini, I., et al., SedNMR: on the edge between solution and solid-state NMR. Acc Chem Res, 2013. 46(9): p. 2059-69.


Solid-state NMR (SS-NMR) of proteins requires that those molecules be immobilized, usually by crystallization, freezing, or lyophilization. However, self-crowding can also slow molecular rotation sufficiently to prevent the nuclear interactions from averaging. To achieve self-crowding, researchers can use a centrifugal field to create a concentration gradient or use regular ultracentrifugation to produce highly concentrated, gel-like solutions. Thus sedimented solute NMR (SedNMR) provides a simple method to prepare biological samples for SS-NMR experiments with minimal perturbation. This method may also give researchers a way to investigate species that are not otherwise accessible by NMR. We induce the sedimentation in one of two ways: (1) by the extreme centrifugal force exerted during magic angle spinning (MAS-induced sedimentation or in situ) or (2) by an ultracentrifuge (UC-induced sedimentation or ex situ). Sedimentation is particularly useful in situations where it is difficult to obtain protein crystals. Furthermore, because the proteins remain in a largely hydrated state, the sedimented samples may provide SS-NMR spectra that have better resolution than the spectra from frozen solutions or lyophilized powders. If sedimentation is induced in situ, the same protein sample can be used for both solution and SS-NMR studies. Finally, we show that in situ SedNMR can be used to detect the NMR signals of large molecular adducts that have binding constants that are too weak to allow for the selective isolation and crystallization of the complexed species. We can selectively induce sedimentation for the heaviest molecular species. Because the complexed molecules are subtracted from the bulk solution, the reaction proceeds further toward the formation of complexes.

Friday, December 20, 2013

Dynamic nuclear polarization of (17)o: direct polarization


Michaelis, V.K., et al., Dynamic nuclear polarization of (17)o: direct polarization. J Phys Chem B, 2013. 117(48): p. 14894-906.


Dynamic nuclear polarization of (17)O was studied using four different polarizing agents: the biradical TOTAPOL and the monoradicals trityl and SA-BDPA, as well as a mixture of the latter two. Field profiles, DNP mechanisms, and enhancements were measured to better understand and optimize directly polarizing this low-gamma quadrupolar nucleus using both mono- and biradical polarizing agents. Enhancements were recorded at <88 K and were >100 using the trityl (OX063) radical and <10 with the other polarizing agents. The >10 000-fold savings in acquisition time enabled a series of biologically relevant small molecules to be studied with small sample sizes and the measurement of various quadrupolar parameters. The results are discussed with comparison to room temperature studies and GIPAW quantum chemical calculations. These experimental results illustrate the strength of high field DNP and the importance of radical selection for studying low-gamma nuclei.

Postdoc @ INAC (CEA / Grenoble university)

From the Ampere list:



Position: Researcher/Engineer at CEA INAC (Institute for Nanoscience and
Cryogenics)
Location: Grenoble/France
Field of research: Ultra Low Temperature Magic Angle Spinning Dynamic Nuclear
Polarization
Duration: 12 months, with possible extension upon results and funding.

We have an opening for a research/engineer position in ultra-low temperature MAS-DNP NMR at the Institute for Nanosciences and Cryogenics (CEA - Commissariat à l'Energie Atomique et aux Energies Alternatives / University of Grenoble). 

Starting date: Beginning of 2014

The lab is equipped with a state of the art Bruker MAS-DNP system (400 MHz / 263 GHz) and is currently running a program to access MAS temperatures below 100 K using Helium spinning. Researchers/Engineers with a strong background or interest in Dynamic Nuclear Polarization / NMR methodology are welcomed to apply. PhD in solid-state NMR/ EPR or MRI is required. Experience with magnetic resonance hardware is heavily desired. A large part of the work will be conducted in close collaboration with Bruker Biospin.

Recent DNP papers from the group :
H. Takahashi et al., Angew. Chem. Intl. Ed. 51 (2012) 11766-11769. 
D. Lee et al., J. Am. Chem. Soc. 134 (2012) 18491-18494.
H. Takahashi et al., J. Am. Chem. Soc. 135 (2013) 5105-5110. 
H. Takahashi et al., Angew. Chem. Intl. Ed. 52 (2013) 6979-6982.

This fellowship is funded by the French National Research Agency. The initial
contract is for 12 months with the possibility of extension.

For further information regarding details of the work and of the appointment,
interested candidates should contact me directly at gael.depaepe@cea.fr.

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Wednesday, December 18, 2013

Optimization of SABRE for polarization of the tuberculosis drugs pyrazinamide and isoniazid


Zeng, H., et al., Optimization of SABRE for polarization of the tuberculosis drugs pyrazinamide and isoniazid. J Magn Reson, 2013. 237(0): p. 73-8.


Hyperpolarization produces nuclear spin polarization that is several orders of magnitude larger than that achieved at thermal equilibrium thus providing extraordinary contrast and sensitivity. As a parahydrogen induced polarization (PHIP) technique that does not require chemical modification of the substrate to polarize, Signal Amplification by Reversible Exchange (SABRE) has attracted a lot of attention. Using a prototype parahydrogen polarizer, we polarize two drugs used in the treatment of tuberculosis, namely pyrazinamide and isoniazid. We examine this approach in four solvents, methanol-d4, methanol, ethanol and DMSO and optimize the polarization transfer magnetic field strength, the temperature as well as intensity and duration of hydrogen bubbling to achieve the best overall signal enhancement and hence hyperpolarization level.

Monday, December 16, 2013

2nd TeraHertz: New opportunities for industry





2nd TeraHertz: New opportunities for industry – Formation courte

How the TeraHertz revolution impacts your business

12 – 14 February 2014


Target audience

R&D managers, engineers and scientists seeking a comprehensive update on TeraHertz technologies and applications, a disruptively evolving field.
A general background in science & technology is sufficient.

Overview

TeraHertz (THz), the frequencies between electronics and optics, was until recently the last unexploited part of the electromagnetic spectrum. The harnessing of THz-based technologies has the potential of impacting globally a vast number of industries, like both electronics in the 70’s and optics in the 80’s did.
THz applications span over a wide array of fields, including:
  • Quality Control and Non-destructive testing
  • Surface analysis
  • Security
  • Chemical and Bio-Medical analysis
  • Telecommunications

Filling the Terahertz “gap” has led to unprecedented creativity in the development and commercialization of TeraHertz sources, transmission components and detectors.
This course is a unique opportunity to network with specialists, converge know-how, and scout for innovative applications.

Objectives

  • Learn about the latest TeraHertz technologies and their market potential
  • Discover examples of TeraHertz applications and the corresponding industrial opportunities
  • Network with specialists in this emerging field

Topics and Hands-on

  • THz test & measurements instrumentations: Network Analyzers
  • THz solid state sources
  • THz on-chip measurements
  • High speed Electronics
  • THz analysis of volatile mixtures

Certification

A certificate of participation will be delivered at the end of the course.

Organization

  • Nanostructured Materials Physics Laboratory (LPMN)
  • Institute of Condensed Matter Physics (ICMP)
  • School of Basic Sciences (FSB)
  • Ecole Polytechnique Fédérale de Lausanne (EPFL)

In collaboration with

  • SWISSto12 SA, a company issued from the EPFL Science Park

Steering committee

  • Prof. Jean-Philippe Ansermet, School of Basic Sciences, ICMP, EPFL
  • Dr. Alessandro MacorSWISSto12 SA
  • Emile de Rijk, SWISSto12 SA

Confirmed Speakers from

  • Agilent
  • BrightSpec
  • Becker-Photonik
  • Cascade Microtech
  • Nuvotronics
  • Radiometer Physics
  • Teledyne Scientific
  • Virginia Diodes

Training

  • Keynote speakers from industry will give an overview of applications and challenges.
  • Hands-on experience with demonstrators

Dates and schedule

  • Wednesday, 12 February 2014, 1.30 pm to 6 pm
  • Thursday, 13 February 2014, 9 am to 6 pm
  • Friday, 14 February 2014, 9 am to 1 pm

Course venue

EPFL Innovation Park, Lausanne, Switzerland

Registration

Course fee : Early registration (before 29th November 2013)
600.- Swiss Francs (includes course material and refreshments)
Late registration
800.- Swiss Francs
Limited places available.
Registration deadline: 13th December 2013
- See more at: http://www.formation-continue-unil-epfl.ch/thz#sthash.tzgRxl5O.dpuf

Shortening spin–lattice relaxation using a copper-chelated lipid at low-temperatures – A magic angle spinning solid-state NMR study on a membrane-bound protein


Yamamoto, K., et al., Shortening spin–lattice relaxation using a copper-chelated lipid at low-temperatures – A magic angle spinning solid-state NMR study on a membrane-bound protein. J. Magn. Reson., 2013. 237(0): p. 175-181.


Inherent low sensitivity of NMR spectroscopy has been a major disadvantage, especially to study biomolecules like membrane proteins. Recent studies have successfully demonstrated the advantages of performing solid-state NMR experiments at very low and ultralow temperatures to enhance the sensitivity. However, the long spin-lattice relaxation time, T1, at very low temperatures is a major limitation. To overcome this difficulty, we demonstrate the use of a copper-chelated lipid for magic angle spinning solid-state NMR measurements on cytochrome-b5 reconstituted in multilamellar vesicles. Our results on multilamellar vesicles containing as small as 0.5mol% of a copper-chelated lipid can significantly shorten T1 of protons, which can be used to considerably reduce the data collection time or to enhance the signal-to-noise ratio. We also monitored the effect of slow cooling on the resolution and sensitivity of (13)C and (15)N signals from the protein and (13)C signals from lipids.

Friday, December 13, 2013

Cryogenics free production of hyperpolarized (129)Xe and (83)Kr for biomedical MRI applications


Hughes-Riley, T., et al., Cryogenics free production of hyperpolarized (129)Xe and (83)Kr for biomedical MRI applications. J Magn Reson, 2013. 237(0): p. 23-33.


As an alternative to cryogenic gas handling, hyperpolarized (hp) gas mixtures were extracted directly from the spin exchange optical pumping (SEOP) process through expansion followed by compression to ambient pressure for biomedical MRI applications. The omission of cryogenic gas separation generally requires the usage of high xenon or krypton concentrations at low SEOP gas pressures to generate hp (129)Xe or hp (83)Kr with sufficient MR signal intensity for imaging applications. Two different extraction schemes for the hp gasses were explored with focus on the preservation of the nuclear spin polarization. It was found that an extraction scheme based on an inflatable, pressure controlled balloon is sufficient for hp (129)Xe handling, while (83)Kr can efficiently be extracted through a single cycle piston pump. The extraction methods were tested for ex vivo MRI applications with excised rat lungs. Precise mixing of the hp gases with oxygen, which may be of interest for potential in vivo applications, was accomplished during the extraction process using a piston pump. The (83)Kr bulk gas phase T1 relaxation in the mixtures containing more than approximately 1% O2 was found to be slower than that of (129)Xe in corresponding mixtures. The experimental setup also facilitated (129)Xe T1 relaxation measurements as a function of O2 concentration within excised lungs.

Wednesday, December 11, 2013

Dynamic Nuclear Polarization NMR Spectroscopy Allows High-Throughput Characterization of Microporous Organic Polymers


Blanc, F., et al., Dynamic nuclear polarization NMR spectroscopy allows high-throughput characterization of microporous organic polymers. J Am Chem Soc, 2013. 135(41): p. 15290-3.


Dynamic nuclear polarization (DNP) solid-state NMR was used to obtain natural abundance (13)C and (15)N CP MAS NMR spectra of microporous organic polymers with excellent signal-to-noise ratio, allowing for unprecedented details in the molecular structure to be determined for these complex polymer networks. Sensitivity enhancements larger than 10 were obtained with bis-nitroxide radical at 14.1 T and low temperature ( approximately 105 K). This DNP MAS NMR approach allows efficient, high-throughput characterization of libraries of porous polymers prepared by combinatorial chemistry methods.

Monday, December 9, 2013

[NMR] Postdoctoral position at BMRZ / Goethe University Frankfurt

From the Ampere Magnetic Resonance List

Dear colleagues,


Applications are invited for a postdoctoral research position in Solid-state DNP Spectroscopy in the Emmy Noether research group led by Dr. Björn Corzilius at the Goethe University Frankfurt/Main, Germany (E13 TV-G-U, 100 %). The postdoctoral researcher will be placed at the seam between the BMRZ and the Institute of Physical and Theoretical Chemistry. The research group focuses on method development and basic research of DNP towards biomolecular applications.

To qualify, the applicant must hold a doctoral degree in chemistry, physics, biochemistry, or biophysics. The applicant must be ambitious and demonstrate a strong motivation and an appropriate background to help develop the proposed research area. Several years of research experience in magnetic resonance methods, especially in DNP, NMR, or EPR are required and should be supported by publications in high-ranking scientific journals and conference contributions. Good language skills in English are a crucial requirement.

The applicant will lead small research groups and work in a cutting-edge field situated at the seam between EPR and NMR and will therefore be able to build or extend an integral knowledge and expertise in the field of magnetic resonance. Experiments will be performed using state-of-the-art instrumentation at the BMRZ or external collaboration sites.

The successful candidate must have very good collaborative skills, have integrity and be flexible and capable of working in a structured and efficient way. The successful candidates should also be able to contribute to the innovative climate within the group.

Please send your relevant and comprehensive application material to Dr. Björn Corzilius: corzilius@em.uni-frankfurt.de.

The contract is fixed term, based on the regulations of the "Wissenschaftszeitvertragsgesetz" and the "Hessische Hochschulgesetz". Initial appointment is for 1 year, with possible extension upon mutual agreement. The University is an equal opportunity employer and strongly encourages women to apply. In case of equal qualification, preference will be given to applicants with disabilities.

-- 

Dr. Björn Corzilius
Emmy Noether Research Group Leader

Institute for Physical and Theoretical Chemistry,
Institute for Biophysical Chemistry
and Center for Biomolecular Magnetic Resonance (BMRZ)

Goethe University Frankfurt
Campus Riedberg
Building N140, Room 1

Max-von-Laue-Str. 7
60438 Frankfurt am Main

phone: +49-(0)69-798-29467
fax: +49-(0)69-798-29404

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NMR web database:

Probing the mobility of ibuprofen confined in MCM-41 materials using MAS-PFG NMR and hyperpolarised-(129)Xe NMR spectroscopy


Guenneau, F., et al., Probing the mobility of ibuprofen confined in MCM-41 materials using MAS-PFG NMR and hyperpolarised-(129)Xe NMR spectroscopy. Phys Chem Chem Phys, 2013. 15(43): p. 18805-8.


The continuous-flow hyperpolarised (HP)-(129)Xe NMR and magic angle spinning-pulsed field gradient (MAS-PFG) NMR techniques have been used for the first time to study the distribution and the dynamics of ibuprofen encapsulated in MCM-41 with two different pore diameters.

Friday, December 6, 2013

Dynamic nuclear polarization of spherical nanoparticles


Akbey, U., et al., Dynamic nuclear polarization of spherical nanoparticles. Phys Chem Chem Phys, 2013. 15(47): p. 20706-16.


Spherical silica nanoparticles of various particle sizes ( approximately 10 to 100 nm), produced by a modified Stoeber method employing amino acids as catalysts, are investigated using Dynamic Nuclear Polarization (DNP) enhanced Nuclear Magnetic Resonance (NMR) spectroscopy. This study includes ultra-sensitive detection of surface-bound amino acids and their supramolecular organization in trace amounts, exploiting the increase in NMR sensitivity of up to three orders of magnitude via DNP. Moreover, the nature of the silicon nuclei on the surface and the bulk silicon nuclei in the core (sub-surface) is characterized at atomic resolution. Thereby, we obtain unique insights into the surface chemistry of these nanoparticles, which might result in improving their rational design as required for promising applications, e.g. as catalysts or imaging contrast agents. The non-covalent binding of amino acids to surfaces was determined which shows that the amino acids not just function as catalysts but become incorporated into the nanoparticles during the formation process. As a result only three distinct Q-types of silica signals were observed from surface and core regions. We observed dramatic changes of DNP enhancements as a function of particle size, and very small particles (which suit in vivo applications better) were hyperpolarized with the best efficiency. Nearly one order of magnitude larger DNP enhancement was observed for nanoparticles with 13 nm size compared to particles with 100 nm size. We determined an approximate DNP penetration-depth ( approximately 4.2 or approximately 5.7 nm) for the polarization transfer from electrons to the nuclei of the spherical nanoparticles. Faster DNP polarization buildup was observed for larger nanoparticles. Efficient hyperpolarization of such nanoparticles, as achieved in this work, can be utilized in applications such as magnetic resonance imaging (MRI).

Wednesday, December 4, 2013

THz Gyrotron and BWO Designed for Operation in DNP-NMR Spectrometer Magnet


Bratman, V.L., et al., THz Gyrotron and BWO Designed for Operation in DNP-NMR Spectrometer Magnet. J Infrared Milli Terahz Waves, 2013. 34(12): p. 837-846.


Dynamic nuclear polarization (DNP) in high-field nuclearmagnetic resonance (NMR) spectroscopy requires medium-power terahertz radiation, which nowadays can be provided basically by gyrotrons with superconducting magnets. As the electron cyclotron frequency is very close to the frequency of electron paramagnetic resonance for the samemagnetic field, under certain conditions the gyrotron can be installed inside the same solenoid used for NMR spectrometer. This eliminates the need for an additional superconducting magnet, results in a shorter terahertz transmission line, and can make DNP systems practical. In addition to an extremely low-voltage gyrotron (“gyrotrino”), we analyze also advantages of strong magnetic field for a slow-wave electron device as an alternative terahertz source.

Monday, December 2, 2013

Formulation and utilization of choline based samples for dissolution dynamic nuclear polarization


Bowen, S. and J.H. Ardenkjaer-Larsen, Formulation and utilization of choline based samples for dissolution dynamic nuclear polarization. J Magn Reson, 2013. 236(0): p. 26-30.


Hyperpolarization by the dissolution dynamic nuclear polarization (DNP) technique permits the generation of high spin polarization of solution state. However, sample formulation for dissolution-DNP is often difficult, as concentration and viscosity must be optimized to yield a dissolved sample with sufficient concentration, while maintaining polarization during the dissolution process. The unique chemical properties of choline permit the generation of highly soluble salts as well as deep eutectic mixtures with carboxylic acids and urea. We describe the formulation of these samples and compare their performance to more traditional sample formulations. Choline yields stable samples with exceptional polarization performance while simultaneously offering the capability to easily remove the choline after dissolution, perform experiments with the hyperpolarized choline, or anything in between.