Wednesday, November 29, 2017

Dynamic nuclear polarization for sensitivity enhancement in modern solid-state NMR #DNPNMR


Lilly Thankamony, A.S., et al., Dynamic nuclear polarization for sensitivity enhancement in modern solid-state NMR. Prog Nucl Magn Reson Spectrosc, 2017. 102-103(Supplement C): p. 120-195.


The field of dynamic nuclear polarization has undergone tremendous developments and diversification since its inception more than 6 decades ago. In this review we provide an in-depth overview of the relevant topics involved in DNP-enhanced MAS NMR spectroscopy. This includes the theoretical description of DNP mechanisms as well as of the polarization transfer pathways that can lead to a uniform or selective spreading of polarization between nuclear spins. Furthermore, we cover historical and state-of-the art aspects of dedicated instrumentation, polarizing agents, and optimization techniques for efficient MAS DNP. Finally, we present an extensive overview on applications in the fields of structural biology and materials science, which underlines that MAS DNP has moved far beyond the proof-of-concept stage and has become an important tool for research in these fields.

[NMR] Assistant Professor in Experimental Magnetic Resonance at University of Florida / National High Magnetic…

From the Ampere Magnetic Resonance List

As part of a major faculty hiring initiative, the Department of Chemistry at the University of Florida (http://www.chem.ufl.edu ) seeks a full-time, nine-month, tenure-track appointment at the level of ASSISTANT PROFESSOR, in the general area of magnetic resonance, broadly defined, to begin August 16, 2018. The successful applicant will join over 40 Faculty in the Department, which is home to the Quantum Theory Project and the Butler Polymer Research Center. The Department has recently opened the Joseph Hernandez Hall, a state-of-the-art teaching and research facility. Numerous opportunities exist for collaboration across the UF campus and the National High Magnetic Field Laboratory (NHMFL; https://nationalmaglab.org/ ) and the Advanced Magnetic Resonance Imaging and Spectroscopy (AMRIS) Facility. The new faculty member will be expected to develop a successful research program that utilizes or develops magnetic resonance methodology, preferably with applications at high magnetic fields. UF and the Department of Chemistry are committed to increasing faculty diversity and candidates from under-represented groups are particularly encouraged to apply. The university and greater Gainesville community enjoy a diversity of cultural events, restaurants, year-round outdoor recreational activity, and social opportunities.

Applications must be submitted through Careers at UF at http://explore.jobs.ufl.edu/cw/en-us/listing/ (search job 505531) and include: a cover letter, curriculum vitae, description of future research plans and teaching philosophy (3 pages maximum combined), and contact information for at least three references. After initial review, letters of recommendation will be requested for short listed applicants. Inquiries can be addressed to the Chair of the search committee (Professor Gail Fanucci fanucci@chem.ufl.edu), Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL 32611-7200. Review of applications will begin December 1, 2017, and continue until the position is filled. The University of Florida is an equal opportunity institution. If an accommodation due to a disability is needed to apply for this position, please call (352) 392-2477 or the Florida Relay System at (800) 955-8771 (TDD). The selection process will be conducted under the provisions of Florida's "Government in the Sunshine" and Public Records laws.


Joanna R. Long, PhD
Associate Professor of Biochemistry & Molecular Biology
Director, Advanced Magnetic Resonance Imaging & Spectroscopy Facility
Assoc. Director, National High Magnetic Field Laboratory

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[NMR] Two PhD positions at Technical University of Munich in hyperpolarized and diffusion MRI

Two PhD positions (TV-L E13, 75 %) at Technical University of Munich in hyperpolarized and diffusion MRI 

Job Description

The Technical University of Munich (TUM) is seeking applications from highly motivated candidates for two PhD positions in magnetic resonance imaging. The PhD positions are embedded within the Emmy Noether Junior Research Group “Combined biochemical and biophysical imaging biomarkers for characterization of tumor metabolism and response to therapy” led by Dr. Franz Schilling and part of the DFG-funded Collaborative Research Center (SFB 824, www.sfb824.de) entitled “Imaging for Selection, Monitoring and Individualization of Cancer Therapies”.

The successful candidates will develop novel non-invasive magnetic resonance (MR) imaging biomarkers of unprecedented sensitivity for the characterization of tumor metabolism and response to therapy. They will focus on previously unexplored pH-sensitive hyperpolarized molecules and advanced diffusion MRI techniques that provide novel information currently not accessible with existing methods. Imaging biomarkers enable a comprehensive characterization of tissue providing functional, physiological, metabolic, cellular and molecular information beyond anatomical structures. For cancer patients, specific non-invasive imaging strategies for early-stage detection, tumor phenotyping and evaluation of response to therapy are not available at a satisfactory level, creating a pressing need for these advanced imaging technologies.

The preclinical imaging core located at the Department of Nuclear Medicine (www.nuk.mri.tum.de) and the Center for Translational Cancer Research (TranslaTUM, www.translatum.tum.de) provides state-of-the-art imaging instrumentation and consists of a group of scientists working on applications and specific improvements of multimodal imaging. 

Background

Recent research articles from our group on these topics are

  • Düwel et al. "Imaging of pH in vivo using hyperpolarized 13C-labeled zymonic acid." Nature Communications (2017), 8:15126. 

  • Schilling et al. "MRI measurements of reporter-mediated increases in transmembrane water exchange enable detection of a gene reporter." Nature Biotechnology (2017) 35(1): 75-80. 

Qualification

We invite applications from candidates having a M.Sc. or equivalent degree in physics, chemistry, bioengineering, or other related subjects. Previous experience in biomedical imaging is beneficial. Team spirit, capability of independent self-motivated work, as well as very good English and communication skills are required. Good computer skills and proficiency in at least one programming language (e.g. MATLAB) are required.

Our offer

The doctoral candidates will be employed by TUM (75 % TV-L E13) for a total duration of three years. Successful applicants will be enrolled within the TUM Graduate School receiving a structured doctoral training (https://www.gs.tum.de/en/doctorate-at-tum/).

Application details

Applications should include a curriculum vitae, certificates and transcripts of academic degrees, a letter of motivation detailing the applicant’s research interests, and contact information for at least 2 references. Please send your application within one PDF-document to bewerbung.nuklearmedizin@mri.tum.de but no later than January 31st 2018.


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Monday, November 27, 2017

Improved strategies for DNP-enhanced 2D 1H-X heteronuclear correlation spectroscopy of surfaces #DNPNMR


Kobayashi, T., et al., Improved strategies for DNP-enhanced 2D 1H-X heteronuclear correlation spectroscopy of surfaces. Solid State Nucl Magn Reson, 2017. 87(Supplement C): p. 38-44.


We demonstrate that dynamic nuclear polarization (DNP)-enhanced 1H-X heteronuclear correlation (HETCOR) measurements of hydrogen-rich surface species are better accomplished by using proton-free solvents. This approach notably prevents HETCOR spectra from being obfuscated by the solvent-derived signals otherwise present in DNP measurements. Additionally, in the hydrogen-rich materials studied here, which included functionalized mesoporous silica nanoparticles and metal organic frameworks, the use of proton-free solvents afforded higher sensitivity gains than the commonly used solvents containing protons. We also explored the possibility of using a solvent-free sample formulation and the feasibility of indirect detection in DNP-enhanced HETCOR experiments.

[NMR] Postdoc in Fast MAS Methods, ETH Zurich

Postdoctoral Position in NMR Methods developement in the solid-state NMR group of Prof. Beat Meier at ETH Zürich

Our research is centred around solid-state NMR structure determination of biomolecules (fibrils, membrane proteins, protein-DNA complexes). Increasing the presently accessible MAS frequencies (150 kHz) to 200-250 kHz will improve dramatically the spectral quality and will, when successful, lead to a greatly improved resolution in the solid-state NMR spectra of large biological systems, e.g. amyloid fibrils, membrane proteins, virus capsids and proteins assemblies. However, new pulse sequencies will be needed for faster MAS.
The project will focus on the development of novel pulse sequences for assignment and structure determination under fast MAS NMR spectroscopy. The theoretical and numerical spin-dynamics simulation work will be closely linked to experimental verification on model proteins. The experimental work can be started with the equipment presently available in the lab at 110-150 kHz MAS. Spectrometers at 500, 600, 850 (2x) and, in the future 1100 MHz are available. See also http://nmr.ethz.ch

Prerequisites: Ph.D. in Chemistry, Physics, Biology, Interdisciplinary Sciences, or related area, experience in solid-state NMR and NMR methodological development. Motivation to work in a multidisciplinary team.

Applications with motivation letter, CV, publication list, and contact information for 2 references should be sent directly to Prof. Beat Meier (beme@ethz.ch). Applications will be accepted until Dec 20.


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Friday, November 24, 2017

Dissolution DNP using trityl radicals at 7 T field #DNPNMR


Jahnig, F., et al., Dissolution DNP using trityl radicals at 7 T field. Phys. Chem. Chem. Phys., 2017. 19(29): p. 19196-19204.


Dissolution DNP has become an important method to generate highly polarized substrates such as pyruvic acid for in vivo imaging and localized spectroscopy. In a quest to further increase the polarization levels, which is important for in vivo MRI employing 13C detection, we describe the design and implementation of a new DNP polarizer that is suitable for dissolution operation at 7 T static magnetic field and a temperature of 1.4 K. We describe all important sample preparation steps and experimental details necessary to optimize trityl based samples for use in our polarizer at this higher field. In [1-13C]-pyruvic acid polarization levels of about 56% are achieved, compared to typical polarization levels of about 35-45% at a standard field of 3.4 T. At the same time, the polarization build-up time increases significantly from about 670 s at 3.4 T to around 1300-1900 s at 7 T, depending on the trityl derivate used. We also investigate the effect of adding trace amounts of Gd3+ to the samples. While one trityl compound does not exhibit any benefit, the other profits significantly, boosting achievable polarization by 6%.

Wednesday, November 22, 2017

Quantifying reaction kinetics of the non-enzymatic decarboxylation of pyruvate and production of peroxymonocarbonate with hyperpolarized 13C-NMR


Drachman, N., et al., Quantifying reaction kinetics of the non-enzymatic decarboxylation of pyruvate and production of peroxymonocarbonate with hyperpolarized 13C-NMR. Phys. Chem. Chem. Phys., 2017. 19(29): p. 19316-19325.


The transient nature of intermediate states in chemical reactions has made their detailed investigation difficult. In this study, we demonstrate the utility of hyperpolarized 13C-NMR to directly observe and quantify the kinetics of the intermediate compound in the non-enzymatic decarboxylation of pyruvate via H2O2 with time resolutions of <1 s. Reactants were sequentially added to a reaction vessel within a 9.4 T NMR magnet while continuously acquiring spectra with a low flip angle, producing the first direct observation at room temperature of the previously proposed reaction intermediate, 2-hydroperoxy-2-hydroxypropanoate. We also performed a series of NMR experiments to determine the identity of a previously unidentified peak, which was found to be peroxymonocarbonate, the product of the side reaction between HCO3-/CO2 and H2O2/OOH-. Using the information obtained from these experiments, we developed a kinetic model which fully describes the mechanism of reaction and can be fit to experimental data to simultaneously determine multiple kinetic rate constants over several orders of magnitude. We also discuss the application of this reaction to the production of hyperpolarized bicarbonate for pH imaging experiments. This study presents a template for the use of hyperpolarized 13C-NMR to study the kinetics and reaction mechanisms of innumerable organic reactions which involve polarizable substrates.

Monday, November 20, 2017

Transferred Overhauser DNP: A Fast, Efficient Approach for Room Temperature 13C ODNP at Moderately Low Fields and Natural Abundance #DNPNMR


Dey, A., A. Banerjee, and N. Chandrakumar, Transferred Overhauser DNP: A Fast, Efficient Approach for Room Temperature 13C ODNP at Moderately Low Fields and Natural Abundance. The Journal of Physical Chemistry B, 2017. 121(29): p. 7156-7162.


Overhauser dynamic nuclear polarization (ODNP) is investigated at a moderately low field (1.2 T) for natural abundance 13C NMR of small molecules in solution state at room temperature. It is shown that ODNP transferred from 1H to 13C by NMR coherence transfer is in general significantly more efficient than direct ODNP of 13C. Compared to direct 13C ODNP, we demonstrate over 4-fold higher 13C sensitivity (signal-to-noise ratio, SNR), achieved in one-eighth of the measurement time by transferred ODNP (t-ODNP). Compared to the 13C signal arising from Boltzmann equilibrium in a fixed measurement time, this is equivalent to about 1500-fold enhancement of 13C signal by t-ODNP, as against a direct 13C ODNP signal enhancement of about 45-fold, both at a moderate ESR saturation factor of about 0.25. This owes in part to the short polarization times characteristic of 1H. Typically, t-ODNP reflects the essentially uniform ODNP enhancements of all protons in a molecule. Although the purpose of this work is to establish the superiority of t-ODNP vis-a-vis direct 13C ODNP, a comparison is also made of the SNR in t-ODNP experiments with standard high resolution NMR as well. Finally, the potential of t-ODNP experiments for 2D heteronuclear correlation spectroscopy of small molecules is demonstrated in 2D 1H-13C HETCOR experiments at natural abundance, with decoupling in both dimensions.

Friday, November 17, 2017

High-resolution hyperpolarized in vivo metabolic 13C spectroscopy at low magnetic field (48.7mT) following murine tail-vein injection


Coffey, A.M., et al., High-resolution hyperpolarized in vivo metabolic 13C spectroscopy at low magnetic field (48.7mT) following murine tail-vein injection. J. Magn. Reson., 2017. 281(Supplement C): p. 246-252.


High-resolution 13C NMR spectroscopy of hyperpolarized succinate-1-13C-2,3-d2 is reported in vitro and in vivo using a clinical-scale, biplanar (80cm-gap) 48.7mT permanent magnet with a high homogeneity magnetic field. Non-localized 13C NMR spectra were recorded at 0.52MHz resonance frequency over the torso of a tumor-bearing mouse every 2s. Hyperpolarized 13C NMR signals with linewidths of ∼3Hz (corresponding to ∼6ppm) were recorded in vitro (2mL in a syringe) and in vivo (over a mouse torso). Comparison of the full width at half maximum (FWHM) for 13C NMR spectra acquired at 48.7mT and at 4.7T in a small-animal MRI scanner demonstrates a factor of ∼12 improvement for the 13C resonance linewidth attainable at 48.7mT compared to that at 4.7T in vitro. 13C hyperpolarized succinate-1-13C resonance linewidths in vivo are at least one order of magnitude narrower at 48.7mT compared to those observed in high-field (≥3T) studies employing HP contrast agents. The demonstrated high-resolution 13C in vivo spectroscopy could be useful for high-sensitivity spectroscopic studies involving monitoring HP agent uptake or detecting metabolism using HP contrast agents with sufficiently large 13C chemical shift differences.

Wednesday, November 15, 2017

Ramped-amplitude NOVEL #DNPNMR


Can, T.V., et al., Ramped-amplitude NOVEL. J. Chem. Phys., 2017. 146(15): p. 154204.


We present a pulsed dynamic nuclear polarization (DNP) study using a ramped-amplitude nuclear orientation via electron spin locking (RA-NOVEL) sequence that utilizes a fast arbitrary waveform generator (AWG) to modulate the microwave pulses together with samples doped with narrow-line radicals such as 1,3-bisdiphenylene-2-phenylallyl (BDPA), sulfonated-BDPA (SA-BDPA), and trityl- OX063. Similar to ramped-amplitude cross polarization in solid-state nuclear magnetic resonance, RA-NOVEL improves the DNP efficiency by a factor of up to 1.6 compared to constant-amplitude NOVEL (CA-NOVEL) but requires a longer mixing time. For example, at mix = 8 s, the DNP efficiency reaches a plateau at a ramp amplitude of 20 MHz for both SA-BDPA and trityl-OX063, regardless of the ramp profile (linear vs. tangent). At shorter mixing times (mix = 0.8 s), we found that the tangent ramp is superior to its linear counterpart and in both cases there exists an optimum ramp size and therefore ramp rate. Our results suggest that RA-NOVEL should be used instead of CA-NOVEL as long as the electronic spin lattice relaxation T1e is sufficiently long and/or the duty cycle of the microwave amplifier is not exceeded. To the best of our knowledge, this is the first example of a time domain DNP experiment that utilizes modulated microwave pulses. Our results also suggest that a precise modulation of the microwave pulses can play an important role in optimizing the efficiency of pulsed DNP experiments and an AWG is an elegant instrumental solution for this purpose.

Monday, November 13, 2017

Anisotropic longitudinal electronic relaxation affects DNP at cryogenic temperatures #DNPNMR

Anisotropic relaxation effects are well know and understood in EPR spectroscopy and have long served as measures to understand the motion (libration) of paramagnetic co-factors (quinones, nitroxide radicals etc.) in biological system. In this study the authors investigate the effect of anisotropic relaxation effects in DNP experiments.

To find more about anisotropic relaxation effects studied by EPR take a look at the work by Sergei Dzuba or the Eatons:


Weber, E.M.M., et al., Anisotropic longitudinal electronic relaxation affects DNP at cryogenic temperatures. Phys. Chem. Chem. Phys., 2017. 19(24): p. 16087-16094.


We report the observation of anisotropic longitudinal electronic relaxation in nitroxide radicals under typical dynamic nuclear polarization conditions. This anisotropy affects the efficiency of dynamic nuclear polarization at cryogenic temperatures of 4 K and high magnetic fields of 6.7 T. Under our experimental conditions, the electron paramagnetic resonance spectrum of nitroxides such as TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl) is only partly averaged by electronic spectral diffusion, so that the relaxation times T1e([small omega]) vary across the spectrum. We demonstrate how the anisotropy of T1e([small omega]) can be taken into account in simple DNP models.

Friday, November 10, 2017

Natural Abundance 17 O DNP NMR Provides Precise O-H Distances and Insights into the Bronsted Acidity of Heterogeneous Catalysts #DNPNMR


Perras, F.A., et al., Natural Abundance 17 O DNP NMR Provides Precise O-H Distances and Insights into the Bronsted Acidity of Heterogeneous Catalysts. Angew Chem Int Ed Engl, 2017. 56(31): p. 9165-9169.

https://www.ncbi.nlm.nih.gov/pubmed/28499071

Heterogeneous Bronsted acid catalysts are tremendously important in industry, particularly in catalytic cracking processes. Here we show that these Bronsted acid sites can be directly observed at natural abundance by 17 O DNP surface-enhanced NMR spectroscopy (SENS). We additionally show that the O-H bond length in these catalysts can be measured with sub-picometer precision, to enable a direct structural gauge of the lability of protons in a given material, which is correlated with the pH of the zero point of charge of the material. Experiments performed on materials impregnated with pyridine also allow for the direct detection of intermolecular hydrogen bonding interactions through the lengthening of O-H bonds.

Research Faculty I, 12 Month Salaried (NHMFL) #DNPNMR

Research Faculty I, 12 Month Salaried (NHMFL)

For more information follow this link: Faculty Position

Research Faculty I, 12 Month Salaried (NHMFL)

Job ID
42607

Location
Tallahassee, FL

Full/Part Time
Full-Time

Regular/Temporary
Regular

Apply On Or Before
12/13/2017

Department
National High Magnetic Field Laboratory (NHMFL)

Responsibilities
This position will be part of a major initiative involving Dynamic Nuclear Polarization (DNP) including magic-angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) spectroscopy. Position will be focused primarily on, but not limited to the operation of the MAS-DNP NMR spectrometer. The research faculty is expected to develop independent and collaborative research in chemical, biological, and material applications of DNP as well as DNP instrumentation and technology. They will work within a team of faculty and engineers through the NMR, EMR and AMRIS programs and in collaboration with users of the NHMFL facilities. A Bruker 600MHz DNP system equipping a 600MHz field-sweepable wide-bore magnet had been installed and is fully operational.

Qualifications
Ph.D. in Chemistry, Physics, Biology, or a related discipline. Experience in DNP and NMR (or EPR).

Expert knowledge in both experimental and theoretical fields in NMR spectroscopy and DNP.
Knowledge of Linux-based computer systems and networks, as it is the operating system of the spectrometer and requires collaborative research with users in various areas locally and remotely.
Computer simulation skills, which are indispensable in interpreting the spectra at the DNP and NMR domains.

Preferred
Electron paramagentic resonance (EPR) spectroscopy.

Contact Info
For additional information, please contact Bettina Roberson at roberson@magnet.fsu.edu.

Pay Plan
This is a Faculty position.

Criminal Background Check
This position requires successful completion of a criminal history background check.

How To Apply
If qualified and interested in a specific job opening as advertised, apply to Florida State University at https://jobs.fsu.edu. If you are a current FSU employee, apply via myFSU > Self Service.

Applicants are required to complete the online application with all applicable information. Applications must include all work history up to ten years, and education details even if attaching a resume.

Equal Employment Opportunity
An Equal Opportunity/Access/Affirmative Action/Pro Disabled & Veteran Employer.

FSU's Equal Opportunity Statement can be viewed at: http://www.hr.fsu.edu/PDF/Publications/diversity/EEO_Statement.pdf

Wednesday, November 8, 2017

In Silico Design of DNP Polarizing Agents: Can Current Dinitroxides Be Improved? #DNPNMR


Perras, F.A., A. Sadow, and M. Pruski, In Silico Design of DNP Polarizing Agents: Can Current Dinitroxides Be Improved? ChemPhysChem, 2017. 18(16): p. 2279-2287.


Numerical calculations of enhancement factors offered by dynamic nuclear polarization in solids under magic angle spinning (DNP-MAS) were performed to determine the optimal EPR parameters for a dinitroxide polarizing agent. We found that the DNP performance of a biradical is more tolerant to the relative orientation of the two nitroxide moieties than previously thought. Generally, any condition in which the gyy tensor components of both radicals are perpendicular to one another is expected to have near-optimal DNP performance. Our results highlight the important role of the exchange coupling, which can lessen the sensitivity of DNP performance to the inter-radical distance, but also lead to lower enhancements when the number of atoms in the linker becomes less than three. Lastly, the calculations showed that the electron T1e value should be near 500 mus to yield optimal performance. Importantly, the newest polarizing agents already feature all of the qualities of the optimal polarizing agent, leaving little room for further improvement. Further research into DNP polarizing agents should then target non-nitroxide radicals, as well as improvements in sample formulations to advance high-temperature DNP and limit quenching and reactivity.

Tuesday, November 7, 2017

[NMR] postdoctoral position in solid-state NMR of proteins

Colleagues,

We have an opening for a postdoc to join our group at University of Massachusetts Amherst, to use solid-state NMR and other biophysical methods to study the structure and dynamics of bacterial chemotaxis receptor protein complexes. This NIH-funded project combines biochemical methods to assemble and characterize native-like functional complexes of these proteins in defined signaling states, with a variety of biophysical methods including solid-state NMR and hydrogen exchange mass spectrometry to determine what changes are involved in signal propagation. See for example our recent publications:


We are especially interested in individuals with 
- enthusiastic interest in mechanistic studies of membrane proteins and protein complexes
- experience with protein expression and purification
- experience with solid-state NMR of proteins

Our lab is part of an interactive community of research groups working with a suite of instruments recently purchased by the new UMass Institute for Applied Life Sciences in the NMR Facility, Biophysical Characterization Facility, and other Core Facilities. UMass Amherst is located along with 4 other colleges in the Pioneer Valley of western Massachusetts, a great place to live and work, and centrally located about 3 hours from New York and 2 hours from Boston.

To apply, candidates should send the following to thompson@chem.umass.edu
- A cover letter that describes your relevant experience, research interests, and career goals.
- CV including the names and contact information of 2-3 references

Lynmarie K Thompson, PhD
Professor
Department of Chemistry, 122 LGRT
University of Massachusetts Amherst
710 North Pleasant St.
Amherst, MA 01003-9336


Office LGRT 864: 413-545-0827
Lab LGRT 820: 413-545-4983


Director, Chemistry Biology Interface Training Program


Molecular and Cellular Biology: http://www.bio.umass.edu/mcb/
Institute for Applied Life Sciences: https://www.umass.edu/ials/

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Monday, November 6, 2017

13C Dynamic Nuclear Polarization Using Derivatives of TEMPO Free Radical #DNPNMR


Niedbalski, P., et al., 13C Dynamic Nuclear Polarization Using Derivatives of TEMPO Free Radical. Appl. Magn. Reson., 2017. 48(9): p. 933-942.


The nitroxide-based 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) free radical is widely used in 13C dynamic nuclear polarization (DNP) due to its relatively low cost, commercial availability, and effectiveness as polarizing agent. While a large number of TEMPO derivatives are available commercially, so far, only few have been tested for use in 13C DNP. In this study, we have tested and evaluated the 13C hyperpolarization efficiency of eight derivatives of TEMPO free radical with different side arms in the 4-position. In general, these TEMPO derivatives were found to have slight variations in efficiency as polarizing agents for DNP of 3 M [1-13C] acetate in 1:1 v/v ethanol:water at 3.35 T and 1.2 K. X-band electron paramagnetic resonance (EPR) spectroscopy revealed no significant differences in the spectral features among these TEMPO derivatives. 2H enrichment of the ethanol:water glassing matrix resulted in further improvement of the solid-state 13C DNP signals by factor of 2 to 2.5-fold with respect to the 13C DNP signal of non-deuterated DNP samples. These results suggest an interaction between the nuclear Zeeman reservoirs and the electron dipolar system via the thermal mixing mechanism.

Friday, November 3, 2017

[NMR] Application deadline reminder: 2018 Winter School on Biomolecular Solid-State NMR: Jan 7-12 in Stowe,…


This is just a friendly reminder that the application deadline for the SSNMR winter school is approaching at the end of this week (please see the original announcement below for details of the winter school and how to apply).

Announcement

The 5th U.S.-Canada Winter School on Biomolecular Solid-State NMR
Stowe, Vermont, USA
January 7-12, 2018

Organizers: Tatyana Polenova (U. Delaware), Christopher Jaroniec (Ohio State U.), Mei Hong (MIT) and Bob Griffin (MIT)

Dear Colleagues,

We invite you to encourage your students, postdocs, and senior associates to attend the 5th Winter School on Biomolecular Solid-State NMR, which will be held on January 7-12, 2018, in Stowe, Vermont. Similar to the previous four highly successful Winter Schools, this pedagogical meeting is aimed at students and postdocs in solid-state NMR as well as more senior scientists in related fields who are interested in entering this vibrant field. Our goals are to provide a focused week of teaching of the core concepts and practices in the increasingly multifaceted and complex field of biological solid-state NMR spectroscopy, and to encourage information sharing among different laboratories. Topics to be covered in the 5th Winter School include:

  • Basics of solid-state NMR: orientation-dependent NMR frequencies, MAS, tensors and rotations, density operator and its time evolution, decoupling and recoupling techniques, and average Hamiltonian theory
  • Multidimensional correlation spectroscopy, non-uniform sampling, techniques for resonance assignment and measurement of structural restraints in biomolecules 
  • Paramagnetic solid-state NMR techniques
  • Techniques for enhancing sensitivity of solid-state NMR: dynamic nuclear polarization and 1H detection
  • Solid-state NMR techniques for measuring molecular motion
  • Solid-state NMR techniques for structural studies of oriented membrane proteins
  • Protein structure calculations in XPLOR-NIH
  • Beyond spin 1/2: NMR of quadrupolar nuclei 
  • Basics of NMR probe design 
In addition to lectures, problem sets and their discussion sessions will be given at the meeting.

Speakers: The following have agreed to serve as lecturers:

Tim Cross (Florida State)
Philip Grandinetti (Ohio State)
Bob Griffin (MIT)
Mei Hong (MIT)
Christopher Jaroniec (Ohio State)
Francesca Marassi (Burnham)
Ann McDermott (Columbia)
Stanley Opella (UC San Diego)
Guido Pintacuda (ENS Lyon)
Tatyana Polenova (Delaware)
Bernd Reif (Tech Univ Munich)
Charles Schwieters (NIH)
Robert Tycko (NIH)
Kurt Zilm (Yale)

Venue and transportation: The meeting will be held at the beautiful and historical Trapp Family Lodge http://www.trappfamily.com/ in Stowe, Vermont. Stowe is accessible from airports in Burlington, VT, Manchester, NH, and Boston, MA. A block of rooms has been reserved at the lodge. We anticipate space for ~70 attendees.

Cost: Room and board will be free for attendees. The registration fee is $500 for academic attendees and $750 for industrial attendees. 

Application: Interested students and postdocs should send the following application materials as a single PDF file to: ASC-WinterSchool2018@osu.edu. The application materials include: (1) a CV, (2) publication list, and (3) a 1-page description of your current research and your statement of interest in attending the Winter School. Please indicate your gender in the CV for the purpose of hotel room assignment. Please name this application file as AdvisorLastName_YourLastName_WS2018app.pdf. For example “McDermott_ Smith_WS2018app.pdf”.

Application deadline: Friday, November 3, 2017. Given the limited number of available spaces, it may not be possible to accommodate applications received after this date. 

Please distribute this announcement to members of your research group as well as to colleagues who may be interested in attending or sending their group members.

With kind regards,
Tatyana, Chris, Mei & Bob

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The Atomic-Level Structure of Cementitious Calcium Silicate Hydrate


Kumar, A., et al., The Atomic-Level Structure of Cementitious Calcium Silicate Hydrate. The Journal of Physical Chemistry C, 2017. 121(32): p. 17188-17196.


Efforts to tune the bulk physical properties of concrete are hindered by a lack of knowledge related to the atomic-level structure and growth of calcium silicate hydrate phases, which form about 50–60% by volume of cement paste. Here we describe the first synthesis of compositionally uniform calcium silicate hydrate phases with Ca:Si ratios tunable between 1.0 and 2.0. The calcium silicate hydrate synthesized here does not contain a secondary Ca(OH)2 phase, even in samples with Ca:Si ratios above 1.6, which is unprecedented for synthetic calcium silicate hydrate systems. We then solve the atomic-level three-dimensional structure of these materials using dynamic nuclear polarization enhanced 1H and 29Si nuclear magnetic resonance experiments in combination with atomistic simulations and density functional theory chemical shift calculations. We discover that bridging interlayer calcium ions are the defining structural characteristic of single-phase cementitious calcium silicate hydrate, inducing the strong hydrogen bonding that is responsible for stabilizing the structure at high Ca:Si ratios.

Wednesday, November 1, 2017

Modeling of Polarization Transfer Kinetics in Protein Hydration Using Hyperpolarized Water


Kim, J., M. Liu, and C. Hilty, Modeling of Polarization Transfer Kinetics in Protein Hydration Using Hyperpolarized Water. The Journal of Physical Chemistry B, 2017. 121(27): p. 6492-6498.


Water–protein interactions play a central role in protein structure, dynamics, and function. These interactions, traditionally, have been studied using nuclear magnetic resonance (NMR) by measuring chemical exchange and nuclear Overhauser effect (NOE). Polarization transferred from hyperpolarized water can result in substantial transient signal enhancements of protein resonances due to these processes. Here, we use dissolution dynamic nuclear polarization and flow-NMR for measuring the pH dependence of transferred signals to the protein trypsin. A maximum enhancement of 20 is visible in the amide proton region of the spectrum at pH 6.0, and of 47 at pH 7.5. The aliphatic region is enhanced up to 2.3 times at pH 6.0 and up to 2.5 times at pH 7.5. The time dependence of these observed signals can be modeled quantitatively using rate equations incorporating chemical exchange to amide sites and, optionally, intramolecular NOE to aliphatic protons. On the basis of these two- and three-site models, average exchange (kex) and cross-relaxation rates (σ) obtained were kex = 12 s–1, σ = −0.33 s–1 for pH 7.5 and kex = 1.8 s–1, σ = −0.72 s–1 for pH 6.0 at a temperature of 304 K. These values were validated using conventional EXSY and NOESY measurements. In general, a rapid measurement of exchange and cross-relaxation rates may be of interest for the study of structural changes of the protein occurring on the same time scale. Besides protein–water interactions, interactions with cosolvent or solutes can further be investigated using the same methods.