Friday, October 20, 2017

Dynamic nuclear polarization studies of nitroxyl spin probes in agarose gel using Overhauser-enhanced magnetic resonance imaging


Meenakumari, V., et al., Dynamic nuclear polarization studies of nitroxyl spin probes in agarose gel using Overhauser-enhanced magnetic resonance imaging. Magn Reson Chem, 2017. 55(11): p. 1022-1028.


Agarose is a tissue-equivalent material and its imaging characteristics similar to those of real tissues. Hence, the dynamic nuclear polarization studies of 3-carboxy-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl (carboxy-PROXYL) in agarose gel were carried out. The dynamic nuclear polarization parameters such as spin lattice relaxation time, longitudinal relaxivity, leakage factor, saturation parameter and coupling parameter were estimated for 2 mM carboxy-PROXYL in phosphate-buffered saline solution and water/agarose mixture (99 : 1). From these results, the spin probe concentration was optimized as 2 mM, and the reduction in enhancement was observed for carboxy-PROXYL in water/agarose mixture (99 : 1) compared with phosphate-buffered saline solution. Phantom imaging was also performed with 2 mM concentration of carboxy-PROXYL in various concentrations of agarose gel at various radio frequency power levels. The results from the dynamic nuclear polarization measurements agree well with the phantom imaging results. These results pave the way for designing model system for human tissues suited to the biological applications of electron spin resonance/Overhauser-enhanced magnetic resonance imaging.

Thursday, October 19, 2017

[NMR] NMR Symposium at the 255th ACS meeting in New Orleans, March 18-22, 2018

Dear Colleagues,

Susannah Scott, Nancy Washton, and I are organizing a magnetic resonance symposium in the Division of Catalysis Science and Technology (CATL) at the 255th ACS meeting in New Orleans which will take place between March 18th and 22nd. The symposium is titled: "New Techniques and Applications of Magnetic Resonance Methods in Heterogeneous Catalysis" and will focus on the development and application of NMR/EPR methods for studying heterogeneous catalysts and catalytic processes. You can find the call for papers here:


and you can submit your abstracts here. Submission deadline is this Friday, October 20, 2017.


We encourage all interested researchers and students to submit an abstract and help make this inaugural symposium a success!

Best regards,

-- 

Frédéric Perras, PhD
Ames Laboratory
US Department of Energy
Ames, IA, 50011


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Wednesday, October 18, 2017

[NMR] Postodoctoral position available in solid-state NMR and DNP in Grenoble #DNPNMR

Postdoctoral Position available in solid-state NMR and DNP in Grenoble (France) ssNMR and DNP investigation of bacterial cell-wall

In this project innovative spectroscopic approaches including solid-state NMR and MAS-DNP will be developed and conducted to investigate the cell wall of mycobacteria and more specifically the role of key peptidoglycan cross-linking enzymes. 

This research will fit in a collaborative effort led by two internationally recognized NMR research groups in Grenoble, which covers a wide spectrum of competences going from high-field liquid-state NMR to advanced MAS-DNP. The team directed by Dr Jean-Pierre Simorre in the Biomolecular NMR Spectroscopy group at Institut de Biologie Structurale has a direct access to a state of the art NMR facility containing six high-field spectrometers (950 MHz, 850 MHz, 700 MHz, 3x600 MHz) equipped with latest solid-state NMR and cryogenic liquid-state probes. The DNP group of the Institute for Nanosciences and Cryogenics, directed by Gaël De Paëpe, hosts two 400-MHz MAS-DNP spectrometers (one equipped with a helium-recirculated cooling system) and is a pioneer in instrumentation and methods developments for MAS-DNP. 

Applicants are expected to have a doctoral experience in solid-state NMR spectroscopy with a strong interest in biomolecular systems. Knowledge in MAS-DNP will be considered as a plus. The successful candidate will be recruited for 24 months (12 months renewable once) funded by an ANR postdoctoral fellowship. Motivated candidates should send their application with a curriculum vitae, a letter of motivation, and the name of 2 referees by December 31st, 2017 via email to both Jean-Pierre Simorre (jean-pierre.simorre@ibs.fr) and Sabine Hediger (sabine.hediger@cea.fr).


Selected related publications from our groups:

1. Schanda P, Triboulet S, Laguri C, Bougault CM, Ayala I, Callon M, Arthur M, Simorre JP. (2014) J. Am. Chem. Soc. 136(51):17852-17860.

2. Takahashi H1, Ayala I, Bardet M, De Paëpe G, Simorre JP, Hediger S. (2013) J Am Chem Soc. 135(13):5105-5110.

3. Kern T, Giffard M, Hediger S, Amoroso A, Giustini C, Bui NK, Joris B, Bougault C, Vollmer W, Simorre JP. (2010) J Am Chem Soc. 132(31):10911-10909.

4. Kern T, Hediger S, Müller P, Giustini C, Joris B, Bougault C, Vollmer W, Simorre JP. (2008) J Am Chem Soc. 130(17):5618-5619.



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Understanding Surface and Interfacial Chemistry in Functional Nanomaterials via Solid-State NMR


In recent years DNP-NMR became a very important tool for ssNMR in the area of material science. This is a very nice review illustrating the application of ssNMR to the area of material science and how DNP-NMR can help to overcome sensitivity issues.


Marchetti, A., et al., Understanding Surface and Interfacial Chemistry in Functional Nanomaterials via Solid-State NMR. Adv Mater, 2017. 29(14): p. 1605895-n/a.


Surface and interfacial chemistry is of fundamental importance in functional nanomaterials applied in catalysis, energy storage and conversion, medicine, and other nanotechnologies. It has been a perpetual challenge for the scientific community to get an accurate and comprehensive picture of the structures, dynamics, and interactions at interfaces. Here, some recent examples in the major disciplines of nanomaterials are selected (e.g., nanoporous materials, battery materials, nanocrystals and quantum dots, supramolecular assemblies, drug-delivery systems, ionomers, and graphite oxides) and it is shown how interfacial chemistry can be addressed through the perspective of solid-state NMR characterization techniques.

Monday, October 16, 2017

T1 nuclear magnetic relaxation dispersion of hyperpolarized sodium and cesium hydrogencarbonate-13 C


Martinez-Santiesteban, F.M., et al., T1 nuclear magnetic relaxation dispersion of hyperpolarized sodium and cesium hydrogencarbonate-13 C. NMR Biomed, 2017. 30(9): p. e3749-n/a.


In vivo pH mapping in tissue using hyperpolarized hydrogencarbonate-13 C has been proposed as a method to study tumor growth and treatment and other pathological conditions related to pH changes. The finite spin-lattice relaxation times (T1 ) of hyperpolarized media are a significant limiting factor for in vivo imaging. Relaxation times can be measured at standard magnetic fields (1.5 T, 3.0 T etc.), but no such data are available at low fields, where T1 values can be significantly shorter. This information is required to determine the potential loss of polarization as the agent is dispensed and transported from the polarizer to the MRI scanner. The purpose of this study is to measure T1 dispersion from low to clinical magnetic fields (0.4 mT to 3.0 T) of different hyperpolarized hydrogencarbonate formulations previously proposed in the literature for in vivo pH measurements. 13 C-enriched cesium and sodium hydrogencarbonate preparations were hyperpolarized using dynamic nuclear polarization, and the T1 values of different samples were measured at different magnetic field strengths using a fast field-cycling relaxometer and a 3.0 T clinical MRI system. The effects of deuterium oxide as a dissolution medium for sodium hydrogencarbonate were also analyzed. This study finds that the cesium formulation has slightly shorter T1 values compared with the sodium preparation. However, the higher solubility of cesium hydrogencarbonate-13 C means it can be polarized at greater concentration, using less trityl radical than sodium hydrogencarbonate-13 C. This study also establishes that the preparation and handling of sodium hydrogencarbonate formulations in relation to cesium hydrogencarbonate is more difficult, due to the higher viscosity and lower achievable concentrations, and that deuterium oxide significantly increases the T1 of sodium hydrogencarbonate solutions. Finally, this work also investigates the influence of pH on the spin-lattice relaxation of cesium hydrogencarbonate-13 C measured over a pH range of 7 to 9 at 0.47 T.

Friday, October 13, 2017

Construction and 13 C hyperpolarization efficiency of a 180 GHz dissolution dynamic nuclear polarization system #DNPNMR


Kiswandhi, A., et al., Construction and 13 C hyperpolarization efficiency of a 180 GHz dissolution dynamic nuclear polarization system. Magn Reson Chem, 2017. 55(9): p. 828-836.


Dynamic nuclear polarization (DNP) via the dissolution method has become one of the rapidly emerging techniques to alleviate the low signal sensitivity in nuclear magnetic resonance (NMR) spectroscopy and imaging. In this paper, we report on the development and 13 C hyperpolarization efficiency of a homebuilt DNP system operating at 6.423 T and 1.4 K. The DNP hyperpolarizer system was assembled on a wide-bore superconducting magnet, equipped with a standard continuous-flow cryostat, and a 180 GHz microwave source with 120 mW power output and wide 4 GHz frequency tuning range. At 6.423 T and 1.4 K, solid-state 13 C polarization P levels of 64% and 31% were achieved for 3 M [1-13 C] sodium acetate samples in 1 : 1 v/v glycerol:water glassing matrix doped with 15 mM trityl OX063 and 40 mM 4-oxo-TEMPO, respectively. Upon dissolution, which takes about 15 s to complete, liquid-state 13 C NMR signal enhancements as high as 240 000-fold (P=21%) were recorded in a nearby high resolution 13 C NMR spectrometer at 1 T and 297 K. Considering the relatively lower cost of our homebuilt DNP system and the relative simplicity of its design, the dissolution DNP setup reported here could be feasibly adapted for in vitro or in vivo hyperpolarized 13 C NMR or magnetic resonance imaging at least in the pre-clinical setting. Copyright (c) 2017 John Wiley & Sons, Ltd.

Wednesday, October 11, 2017

Transportable hyperpolarized metabolites #DNPNMR


This article describes an elegant way to increase the throughput of a hyperpolarizer by storing the hyperpolarized materials separated from the polarizing agents.



Ji, X., et al., Transportable hyperpolarized metabolites. Nat Commun, 2017. 8: p. 13975.


Nuclear spin hyperpolarization of 13C-labelled metabolites by dissolution dynamic nuclear polarization can enhance the NMR signals of metabolites by several orders of magnitude, which has enabled in vivo metabolic imaging by MRI. However, because of the short lifetime of the hyperpolarized magnetization (typically <1 min), the polarization process must be carried out close to the point of use. Here we introduce a concept that markedly extends hyperpolarization lifetimes and enables the transportation of hyperpolarized metabolites. The hyperpolarized sample can thus be removed from the polarizer and stored or transported for use at remote MRI or NMR sites. We show that hyperpolarization in alanine and glycine survives 16 h storage and transport, maintaining overall polarization enhancements of up to three orders of magnitude.

[NMR] PhD/Postdoc positions available on DNP/MAS NMR and multi-frequency EPR in Konstanz, Germany #DNPNMR




PhD/Postdoc positions available on DNP/MAS NMR and multi-frequency EPR

About the group:
We are a newly established research group in the Chemistry Department of the University of Konstanz (Baden-Württemberg, Germany). Our research encompasses the development of magnetic resonance spectroscopy, particularly dynamic nuclear 
polarization (DNP) / magic-angle spinning (MAS) NMR and multi-frequency electron-paramagnetic resonance (EPR), and its application in structural biology, enzymology, and catalysis.

About the positions:
Possible research projects are: 
- To investigate if and how the high polarization generated in the photo-excited triplet states of certain chromophores can be used for DNP/MAS NMR. 
- The development of "DNP pulse sequences". This project has an experimental component as well as a considerable theoretical component. 
- The application and development of multi-frequency EPR spectroscopy to study reaction mechanisms.
The exact topic of the candidate's research can be agreed on in consultation and will depend on the candidate's background and interests.

About the candidate:
You have a strong interest in basic science, particularly in physical chemistry and spectroscopy. You are highly motivated and willing to work on solving complex, long-term problems. In your research, you are able to make the combination between theory and experiment. You have a MSc degree in Physics, Chemistry or a related field. For postdocs a PhD in MAS NMR is a plus.

About Konstanz and the university:
The University of Konstanz is a young university (founded 1966) and has since 2006 been a part of the German Exzellenzinitiative. The city of Konstanz is nicely situated on Lake Constance (Bodensee) near the Swiss border.

Applicants should send a cover letter and CV to Dr. Guinevere Mathies. E-mail: guinevere.mathies@uni-konstanz.de. Informal inquiries are also appreciated. Applications will be accepted until the positions are filled.

Visit also our website: chemie.uni.kn/mathies.


-- Dr. Guinevere Mathies Emmy Noether Group Leader Department of Chemistry University of Konstanz E-mail: guinevere.mathies@uni-konstanz.de Phone: +49 7531 88 3962 (office) Address: University of Konstanz Room L 828 / Mail box 706 Universitätsstrasse 10 78464 Konstanz Germany

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Monday, October 9, 2017

Deuteration of Hyperpolarized 13 C-Labeled Zymonic Acid Enables Sensitivity-Enhanced Dynamic MRI of pH


Hundshammer, C., et al., Deuteration of Hyperpolarized 13 C-Labeled Zymonic Acid Enables Sensitivity-Enhanced Dynamic MRI of pH. ChemPhysChem, 2017. 18(18): p. 2422-2425.


Aberrant pH is characteristic of many pathologies such as ischemia, inflammation or cancer. Therefore, a non-invasive and spatially resolved pH determination is valuable for disease diagnosis, characterization of response to treatment and the design of pH-sensitive drug-delivery systems. We recently introduced hyperpolarized [1,5-13 C2 ]zymonic acid (ZA) as a novel MRI probe of extracellular pH utilizing dissolution dynamic polarization (DNP) for a more than 10000-fold signal enhancement of the MRI signal. Here we present a strategy to enhance the sensitivity of this approach by deuteration of ZA yielding [1,5-13 C2 , 3,6,6,6-D4 ]zymonic acid (ZAd ), which prolongs the liquid state spin lattice relaxation time (T1 ) by up to 39 % in vitro. Measurements with ZA and ZAd on subcutaneous MAT B III adenocarcinoma in rats show that deuteration increases the signal-to-noise ratio (SNR) by up to 46 % in vivo. Furthermore, we demonstrate a proof of concept for real-time imaging of dynamic pH changes in vitro using ZAd , potentially allowing for the characterization of rapid acidification/basification processes in vivo.

Friday, October 6, 2017

Dynamic Nuclear Polarization Fast Field Cycling Method for the Selective Study of Molecular Dynamics in Block Copolymers #DNPNMR


Gizatullin, B., et al., Dynamic Nuclear Polarization Fast Field Cycling Method for the Selective Study of Molecular Dynamics in Block Copolymers. ChemPhysChem, 2017. 18(17): p. 2347-2356.


Dynamic nuclear polarization (DNP) is one of the most useful methods to increase sensitivity in NMR spectroscopy. It is based on the transfer of magnetization from an electron to the nuclear spin system. Based on previous work that demonstrated the feasibility of integrating DNP with fast field cycling (FFC) relaxometry and the possibility to distinguish between different mechanisms, such as the Overhauser effect (OE) and the solid effect (SE), the first FFC study of the differential relaxation properties of a copolymer is presented. For this purpose, concentrated solutions of the polystyrene-block-polybutadiene-block-polystyrene (SBS) triblock copolymer and the corresponding homopolymers were investigated. T1 -T2 relaxation data are discussed in terms of molecular mobility and the presence of radicals. The DNP selective data indicate a dominant SE contribution to the enhancement of the NMR signal for both blocks of the triblock copolymer and for the homopolymer solutions. The enhancement factors are different for both polymer types and in the copolymer, which is explained by the individual 1 H T1 relaxation times and different electron-nucleus coupling strength. The T1 relaxation dispersion measurements of the SE enhanced signal were performed, which led to improved signal-to-noise ratios that allowed the site-specific separation of relaxation times and their dependence on the Larmor frequency with a higher accuracy.

Wednesday, October 4, 2017

Persistent Radicals of Self-assembled Benzophenone bis-Urea Macrocycles: Characterization and Application as a Polarizing Agent for Solid-state DNP MAS Spectroscopy #DNPNMR


DeHaven, B.A., et al., Persistent Radicals of Self-assembled Benzophenone bis-Urea Macrocycles: Characterization and Application as a Polarizing Agent for Solid-state DNP MAS Spectroscopy. Chemistry, 2017. 23(34): p. 8315-8319.


UV-irradiation of a self-assembled benzophenone bis-urea macrocycle generates mum amounts of radicals that persist for weeks under ambient conditions. High-field EPR and variable-temperature X-band EPR studies suggest a resonance stabilized radical pair through H-abstraction. These endogenous radicals were applied as a polarizing agent for magic angle spinning (MAS) dynamic nuclear polarization (DNP) NMR enhancement. The field-stepped DNP enhancement profile exhibits a sharp peak with a maximum enhancement of on/off =4 superimposed on a nearly constant DNP enhancement of on/off =2 over a broad field range. This maximum coincides with the high field EPR absorption spectrum, consistent with an Overhauser effect mechanism. DNP enhancement was observed for both the host and guests, suggesting that even low levels of endogenous radicals can facilitate the study of host-guest relationships in the solid-state.

Monday, October 2, 2017

Dynamic nuclear polarization studies on deuterated nitroxyl spin probes #DNPNMR


David Jebaraj, D., H. Utsumi, and A. Milton Franklin Benial, Dynamic nuclear polarization studies on deuterated nitroxyl spin probes. Magn Reson Chem, 2017. 55(10): p. 909-916.


Detailed dynamic nuclear polarization and electron spin resonance studies were carried out for 3-carbamoyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl, 3-carboxy-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl,3-methoxycarbonyl-2,2,5,5-tetram ethy pyrolidine-1-oxyl nitroxyl radicals and their corresponding deuterated nitroxyl radicals, used in Overhauser-enhanced magnetic resonance imaging for the first time. The dynamic nuclear polarization parameters such as dynamic nuclear polarization (DNP) factor, longitudinal relaxivity, saturation parameter, leakage factor and coupling factor were estimated for deuterated nitroxyl radicals. DNP enhancement increases with agent concentration up to 3 mm and decreases above 3 mm. The proton spin-lattice relaxation time and the longitudinal relaxivity parameters were estimated. The leakage factor increases with increasing agent concentration up to 3 mm and reaches plateau in the region 3-5 mm. The coupling parameter shows the interaction between the electron and nuclear spins to be mainly dipolar in origin. DNP spectrum exhibits that the full width at half maximum values are higher for undeuterated nitroxyl radicals compared with deuterated nitroxyl radicals, which leads to the increase in DNP enhancement. The ESR parameters such as, the line width, line shape, signal intensity ratio, rotational correlation time, hyperfine coupling constant and g-factor were calculated. The narrow line width was observed for deuterated nitroxyl radicals compared with undeuterated nitroxyl radicals, which leads to the higher saturation parameter value and DNP enhancement. The novelty of the work permits clear understanding of the DNP parameters determining the higher DNP enhancement compared with the undeuterated nitroxyl radicals. Copyright (c) 2017 John Wiley & Sons, Ltd.