Friday, July 21, 2017

Dynamic nuclear polarization-magnetic resonance imaging at low ESR irradiation frequency for ascorbyl free radicals

Ito, S. and F. Hyodo, Dynamic nuclear polarization-magnetic resonance imaging at low ESR irradiation frequency for ascorbyl free radicals. Scientific Reports, 2016. 6: p. 21407.


Highly water-soluble ubiquinone-0 (CoQ0) reacts with ascorbate monoanion (Asc) to mediate the production of ascorbyl free radicals (AFR). Using aqueous reaction mixture of CoQ0 and Asc, we obtained positively enhanced dynamic nuclear polarization (DNP)-magnetic resonance (MR) images of the AFR at low frequency (ranging from 515 to 530 MHz) of electron spin resonance (ESR) irradiation. The shape of the determined DNP spectrum was similar to ESR absorption spectra with doublet spectral peaks. The relative locational relationship of spectral peaks in the DNP spectra between the AFR (520 and 525 MHz), 14N-labeled carbamoyl-PROXYL (14N-CmP) (526.5 MHz), and Oxo63 (522 MHz) was different from that in the X-band ESR spectra, but were similar to that in the 300-MHz ESR spectra. The ratio of DNP enhancement to radical concentration for the AFR was higher than those for 14N-CmP, Oxo63, and flavin semiquinone radicals. The spectroscopic DNP properties observed for the AFR were essentially the same as those for AFR mediated by pyrroloquinoline quinone. Moreover, we made a success of in vivo DNP-MR imaging of the CoQ0-mediated AFR which was administered by the subcutaneous and oral injections as an imaging probe.

Wednesday, July 19, 2017

Coherent evolution of parahydrogen induced polarisation using laser pump, NMR probe spectroscopy: Theoretical framework and experimental observation


Halse, M.E., et al., Coherent evolution of parahydrogen induced polarisation using laser pump, NMR probe spectroscopy: Theoretical framework and experimental observation. J Magn Reson, 2017. 278: p. 25-38.


We recently reported a pump-probe method that uses a single laser pulse to introduce parahydrogen (p-H2) into a metal dihydride complex and then follows the time-evolution of the p-H2-derived nuclear spin states by NMR. We present here a theoretical framework to describe the oscillatory behaviour of the resultant hyperpolarised NMR signals using a product operator formalism. We consider the cases where the p-H2-derived protons form part of an AX, AXY, AXYZ or AA'XX' spin system in the product molecule. We use this framework to predict the patterns for 2D pump-probe NMR spectra, where the indirect dimension represents the evolution during the pump-probe delay and the positions of the cross-peaks depend on the difference in chemical shift of the p-H2-derived protons and the difference in their couplings to other nuclei. The evolution of the NMR signals of the p-H2-derived protons, as well as the transfer of hyperpolarisation to other NMR-active nuclei in the product, is described. The theoretical framework is tested experimentally for a set of ruthenium dihydride complexes representing the different spin systems. Theoretical predictions and experimental results agree to within experimental error for all features of the hyperpolarised 1H and 31P pump-probe NMR spectra. Thus we establish the laser pump, NMR probe approach as a robust way to directly observe and quantitatively analyse the coherent evolution of p-H2-derived spin order over micro-to-millisecond timescales.

Tuesday, July 18, 2017

[NMR] Postdoc position on SSNMR at the University of Lille, France #DNPNMR


Please forward to potential candidates.

Project title: Development of high-field (DNP)-NMR methods to detect quadrupolar nuclei on catalytic surfaces

A two-year postdoc position in solid-state NMR spectroscopy of advanced materials is available at the University of Lille, Lille, France. It will start preferably in December 2017.

Project description: The development of improved heterogeneous catalysts can be undertaken in a rational way by a better
understanding of their structures. Solid-state NMR spectroscopy is very well suited to the study of heterogeneous catalysts because it can give information on the local structure. However, the lack of sensitivity and resolution poses limit for the characterization of surface sites, notably when they are occupied by quadrupolar nuclei (11B, 17O, 27Al, 67Zn, 95Mo...) exhibiting NMR signal broaden by large quadrupolar interaction. This project aims at developing and applying novel solid-state high-field (DNP)NMR methods to probe the local environment of quadrupolar nuclei. It will provide unique insights into the structure of the catalytic surfaces, which will be useful to improve their performances.

Host and research infrastructure: Lille is a vibrant and handsome city, imbued with a rich history, located in the center of northwestern Europe (only 30 min by high-speed trains from Brussels, 1h from Paris and 1h30 from London). Lille is one of France’s top student cities and the university of Lille is a leading center for magnetic resonance. Lille NMR facility includes 800 and 900 MHz NMR spectrometers and has been selected to host the first 1.2 GHz NMR spectrometer to be installed in France. Our research group is internationally known for the development of solid-state NMR methods, notably for quadrupolar nuclei, and the characterization of heterogeneous catalysts. We have an expertise in high-field solid-state NMR spectroscopy and were among the pioneers of high-field DNP-NMR of hybrid and inorganic materials. 

The person: We seek application from candidates with experience in the development of solid-state NMR methods and/or the NMR characterization of inorganic materials and catalysts. The successful applicant will be given the opportunity to work in an exciting environment with national and international collaborations.

Contact: Applications and informal queries about the lab and research projects should be directed by

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Monday, July 17, 2017

Dynamic Polarization and Relaxation of 75As Nuclei in Silicon at High Magnetic Field and Low Temperature #DNPNMR


Järvinen, J., et al., Dynamic Polarization and Relaxation of 75As Nuclei in Silicon at High Magnetic Field and Low Temperature. Appl. Magn. Reson., 2017. 48(5): p. 473-483.


We present the results of experiments on dynamic nuclear polarization and relaxation of 75As in silicon crystals. Experiments are performed in strong magnetic fields of 4.6 T and temperatures below 1 K. At these conditions donor electron spins are fully polarized, and the allowed and forbidden electron spin resonance transitions are well resolved. We demonstrate effective nuclear polarization of 75As nuclei via the Overhauser effect on the time scale of several hundred seconds. Excitation of the forbidden transitions leads to a polarization through the solid effect. The relaxation rate of donor nuclei has strong temperature dependence characteristic of Orbach process.

Friday, July 14, 2017

Bis-Gadolinium Complexes for Solid Effect and Cross Effect Dynamic Nuclear Polarization #DNPNMR


Kaushik, M., et al., Bis-Gadolinium Complexes for Solid Effect and Cross Effect Dynamic Nuclear Polarization. Angew Chem Int Ed Engl, 2017. 56(15): p. 4295-4299.


High-spin complexes act as polarizing agents (PAs) for dynamic nuclear polarization (DNP) in solid-state NMR spectroscopy and feature promising aspects towards biomolecular DNP. We present a study on bis(Gd-chelate)s which enable cross effect (CE) DNP owing to spatial confinement of two dipolar-coupled electron spins. Their well-defined GdGd distances in the range of 1.2-3.4 nm allowed us to elucidate the GdGd distance dependence of the DNP mechanism and NMR signal enhancement. We found that GdGd distances above 2.1 nm result in solid effect DNP while distances between 1.2 and 2.1 nm enable CE for 1 H, 13 C, and 15 N nuclear spins. We compare 263 GHz electron paramagnetic resonance (EPR) spectra with the obtained DNP field profiles and discuss possible CE matching conditions within the high-spin system and the influence of dipolar broadening of the EPR signal. Our findings foster the understanding of the CE mechanism and the design of high-spin PAs for specific applications of DNP.

Wednesday, July 12, 2017

Solvent signal suppression for high-resolution MAS-DNP #DNPNMR


Lee, D., S.R. Chaudhari, and G. De Paepe, Solvent signal suppression for high-resolution MAS-DNP. J Magn Reson, 2017. 278: p. 60-66.


Dynamic nuclear polarization (DNP) has become a powerful tool to substantially increase the sensitivity of high-field magic angle spinning (MAS) solid-state NMR experiments. The addition of dissolved hyperpolarizing agents usually results in the presence of solvent signals that can overlap and obscure those of interest from the analyte. Here, two methods are proposed to suppress DNP solvent signals: a Forced Echo Dephasing experiment (FEDex) and TRAnsfer of Populations in DOuble Resonance Echo Dephasing (TRAPDORED) NMR. These methods reintroduce a heteronuclear dipolar interaction that is specific to the solvent, thereby forcing a dephasing of recoupled solvent spins and leaving acquired NMR spectra free of associated resonance overlap with the analyte. The potency of these methods is demonstrated on sample types common to MAS-DNP experiments, namely a frozen solution (of l-proline) and a powdered solid (progesterone), both containing deuterated glycerol as a DNP solvent. The proposed methods are efficient, simple to implement, compatible with other NMR experiments, and extendable past spectral editing for just DNP solvents. The sensitivity gains from MAS-DNP in conjunction with FEDex or TRAPDORED then permits rapid and uninterrupted sample analysis.

Monday, July 10, 2017

Dynamic Nuclear Polarization NMR as a new tool to investigate the nature of organic compounds occluded in plant silica particles #DNPNMR


Masion, A., et al., Dynamic Nuclear Polarization NMR as a new tool to investigate the nature of organic compounds occluded in plant silica particles. Sci Rep, 2017. 7(1): p. 3430.


The determination of the chemical nature of the organic matter associated with phytoliths remains a challenge. This difficulty mainly stems from amounts of organic carbon (C) that are often well below the detection limit of traditional spectroscopic tools. Conventional solid-state 13C Nuclear Magnetic Resonance (NMR) is widely used to examine the nature and structure of organic molecules, but its inherent low sensitivity prohibits the observation of diluted samples. The recent advent of commercial microwave source in the terahertz range triggered a renewed interest in the Dynamic Nuclear Polarization (DNP) technique to improve the signal to noise ratio of solid-state NMR experiments. With this technique, the 13C spectrum of a phytolith sample containing 0.1% w/w C was obtained overnight with sufficient quality to permit a semi-quantitative analysis of the organic matter, showing the presence of peptides and carbohydrates as predominant compounds. Considering the natural abundance of the 13C isotope, this experiment demonstrates that DNP NMR is sufficiently sensitive to observe spin systems present in amounts as low as a few tens of ppm.

Friday, July 7, 2017

Peptide and Protein Dynamics and Low-Temperature/DNP Magic Angle Spinning NMR #DNPNMR


Ni, Q.Z., et al., Peptide and Protein Dynamics and Low-Temperature/DNP Magic Angle Spinning NMR. J Phys Chem B, 2017. 121(19): p. 4997-5006.


In DNP MAS NMR experiments at approximately 80-110 K, the structurally important -13CH3 and -15NH3+ signals in MAS spectra of biological samples disappear due to the interference of the molecular motions with the 1H decoupling. Here we investigate the effect of these dynamic processes on the NMR line shapes and signal intensities in several typical systems: (1) microcrystalline APG, (2) membrane protein bR, (3) amyloid fibrils PI3-SH3, (4) monomeric alanine-CD3, and (5) the protonated and deuterated dipeptide N-Ac-VL over 78-300 K. In APG, the three-site hopping of the Ala-Cbeta peak disappears completely at 112 K, concomitant with the attenuation of CP signals from other 13C's and 15N's. Similarly, the 15N signal from Ala-NH3+ disappears at approximately 173 K, concurrent with the attenuation in CP experiments of other 15N's as well as 13C's. In bR and PI3-SH3, the methyl groups are attenuated at approximately 95 K, while all other 13C's remain unaffected. However, both systems exhibit substantial losses of intensity at approximately 243 K. Finally, with spectra of Ala and N-Ac-VL, we show that it is possible to extract site specific dynamic data from the temperature dependence of the intensity losses. Furthermore, 2H labeling can assist with recovering the spectral intensity. Thus, our study provides insight into the dynamic behavior of biological systems over a wide range of temperatures, and serves as a guide to optimizing the sensitivity and resolution of structural data in low temperature DNP MAS NMR spectra.

Wednesday, July 5, 2017

Surface Binding of TOTAPOL Assists Structural Investigations of Amyloid Fibrils by Dynamic Nuclear Polarization NMR Spectroscopy #DNPNMR


Nagaraj, M., et al., Surface Binding of TOTAPOL Assists Structural Investigations of Amyloid Fibrils by Dynamic Nuclear Polarization NMR Spectroscopy. Chembiochem, 2016. 17(14): p. 1308-11.


Dynamic nuclear polarization (DNP) NMR can enhance sensitivity but often comes at the price of a substantial loss of resolution. Two major factors affect spectral quality: low-temperature heterogeneous line broadening and paramagnetic relaxation enhancement (PRE) effects. Investigations by NMR spectroscopy, isothermal titration calorimetry (ITC), and EPR revealed a new substantial affinity of TOTAPOL to amyloid surfaces, very similar to that shown by the fluorescent dye thioflavin-T (ThT). As a consequence, DNP spectra with remarkably good resolution and still reasonable enhancement could be obtained at very low TOTAPOL concentrations, typically 400 times lower than commonly employed. These spectra yielded several long-range constraints that were difficult to obtain without DNP. Our findings open up new strategies for structural studies with DNP NMR spectroscopy on amyloids that can bind the biradical with affinity similar to that shown towards ThT.

[NMR] Solid-state NMR position in 
Karlsruhe, Germany

Voxalytic GmbH, the microcoil company, is expanding its young team, seeking applications from specialists in solid-state NMR. The successful applicant will qualify our NMR detector products for specific applications, formulate product needs, and maintain customer relations. Ideally, you will bring along a PhD in solid-state NMR, with knowledge of the state-of-the-art, and the willingness to travel. Applications should be sent via email (PDF please) to:



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Monday, July 3, 2017

Efficient assignment and NMR analysis of an intact virus using sequential side-chain correlations and DNP sensitization #DNPNMR


Sergeyev, I.V., et al., Efficient assignment and NMR analysis of an intact virus using sequential side-chain correlations and DNP sensitization. Proc Natl Acad Sci U S A, 2017. 114(20): p. 5171-5176.


An experimental strategy has been developed to increase the efficiency of dynamic nuclear polarization (DNP) in solid-state NMR studies. The method makes assignments simpler, faster, and more reliable via sequential correlations of both side-chain and Calpha resonances. The approach is particularly suited to complex biomolecules and systems with significant chemical-shift degeneracy. It was designed to overcome the spectral congestion and line broadening that occur due to sample freezing at the cryogenic temperatures required for DNP. Nonuniform sampling (NUS) is incorporated to achieve time-efficient collection of multidimensional data. Additionally, fast (25 kHz) magic-angle spinning (MAS) provides optimal sensitivity and resolution. Data collected in <1 wk produced a virtually complete de novo assignment of the coat protein of Pf1 virus. The peak positions and linewidths for samples near 100 K are perturbed relative to those near 273 K. These temperature-induced perturbations are strongly correlated with hydration surfaces.

Friday, June 30, 2017

Solvent suppression in DNP enhanced solid state NMR #DNPNMR


Yarava, J.R., et al., Solvent suppression in DNP enhanced solid state NMR. J Magn Reson, 2017. 277: p. 149-153.


We show how DNP enhanced solid-state NMR spectra can be dramatically simplified by suppression of solvent signals. This is achieved by (i) exploiting the paramagnetic relaxation enhancement of solvent signals relative to materials substrates, or (ii) by using short cross-polarization contact times to transfer hyperpolarization to only directly bonded carbon-13 nuclei in frozen solutions. The methods are evaluated for organic microcrystals, surfaces and frozen solutions. We show how this allows for the acquisition of high-resolution DNP enhanced proton-proton correlation experiments to measure inter-nuclear proximities in an organic solid.

[NMR] Postdoctoral Position in DNP-NMR at Dartmouth

Postdoctoral Position in DNP-NMR at Dartmouth 

A postdoctoral position is available in the group of Professor Chandrasekhar Ramanathan in the Department of Physics and Astronomy at Dartmouth College to investigate the spin physics of surfaces and low-dimensional spin systems using DNP-NMR. 

Our group works at the interface of quantum information processing and condensed matter and materials physics. We develop and use magnetic resonance methods (including NMR, DNP and EDMR) to control and characterize the spin dynamics of solid state spin systems. The lab currently houses a custom-built 94 GHz DNP system, a 7 T solid-state NMR system, a 9.4 T liquid state NMR system and zero- and low-field EDMR systems. Additional information, including recent publications, can be found at http://www.dartmouth.edu/~cramanathan

Application

The preferred applicant will have a PhD in Physics, Chemistry or a related field and strong experimental skills. Knowledge of RF, microwave and cryogenic techniques and magnetic resonance methods is strongly desired. Interested candidates are invited to submit an electronic application (CV, brief statement of research interests and list of references) to sekhar.ramanathan@dartmouth.edu

The anticipated start date is October 1, 2017 or soon after.

About Dartmouth

Founded in 1769, Dartmouth is a member of the Ivy League and has a deep commitment to combining outstanding undergraduate liberal arts and graduate education with distinguished research and scholarship. Dartmouth is located in the scenic Upper Valley region of New England, about a 2-hour drive from Boston and 3.5 hours from Montreal.

------------------------------
Chandrasekhar Ramanathan
Department of Physics and Astronomy
6127 Wilder Laboratory
Dartmouth College
Hanover, NH 03755

Tel: +1 (603) 646-9780



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Thursday, June 29, 2017

[NMR] [Help] Reply Reply All Forward Postdoc or PhD position at the MPI for Biophysical Chemistry in Göttingen, Germany



The “NMR Signal Enhancement Group” at the Max Planck Institute for
Biophysical Chemistry invites applications for a


Ph.D. or Postdoc Position
- Chemist for the synthesis of magnetic resonance contrast agents -
(Code Number 27-17)

We are looking for a highly motivated Ph.D. student or Postdoc who will work on the synthesis of contrast agents for magnetic resonance imaging experiments. The position is to be filled by January 2018.

He/she should have a strong background in synthetic chemistry, medicinal chemistry or related disciplines. Knowledge about magnetic resonance (MR) methods is advantageous.

We offer an international and highly productive and innovative working atmosphere and provide state-of-the-art MR equipment and collaboration possibilities.

For a Ph.D. student position, candidates should hold a Master’s (or equivalent) degree in life science. The Ph.D. position is limited to three years with a possible extension.

Postdoc candidates hold a Ph.D. degree in life science. The initial appointment for Postdocs is 2 years with possibilities for extension.

The payment and benefits are based on the TVöD guidelines.

The Max Planck Society is committed to increasing the number of individuals with disabilities in its workforce and therefore encourages applications from such qualified individuals. Furthermore, the Max Planck Society seeks to increase the number of women in those areas where they are underrepresented and therefore explicitly encourages women to apply.

Interested candidates should send their applications (application deadline: 30.09.2017) preferably via e-mail with reference to the code number 27-17, including a statement of research interests and two letters of recommendation send under separate cover, to



Max Planck Institute for Biophysical Chemistry
NMR Signal Enhancement Group
Dr. Stefan Glöggler
Am Fassberg 11, 37077 Göttingen
Germany

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Wednesday, June 28, 2017

Dynamic Nuclear Polarization of beta-Cyclodextrin Macromolecules #DNPNMR


Caracciolo, F., et al., Dynamic Nuclear Polarization of beta-Cyclodextrin Macromolecules. J Phys Chem B, 2017. 121(12): p. 2584-2593.


1H dynamic nuclear polarization and nuclear spin-lattice relaxation rates have been studied in amorphous complexes of beta-cyclodextrins doped with different concentrations of the TEMPO radical. Nuclear polarization increased up to 10% in the optimal case, with a behavior of the buildup rate (1/TPOL) and of the nuclear spin-lattice relaxation rate (1/T1n) consistent with a thermal mixing regime. The temperature dependence of 1/T1n and its increase with the radical concentration indicate a relaxation process arising from the modulation of the electron-nucleus coupling by the glassy dynamics. The high-temperature relaxation is driven by molecular motions, and 1/T1n was studied at room temperature in liquid solutions for dilution levels close to the ones typically used for in vivo studies.

Friday, June 23, 2017

A DNP-supported solid-state NMR study of carbon species in fluid catalytic cracking catalysts #DNPNMR


Mance, D., et al., A DNP-supported solid-state NMR study of carbon species in fluid catalytic cracking catalysts. Chem Commun (Camb), 2017. 53(28): p. 3933-3936.


A combination of solid-state NMR techniques supported by EPR and SEM-EDX experiments was used to localize different carbon species (coke) in commercial fluid catalytic cracking catalysts. Aliphatic coke species formed during the catalytic process and aromatic coke species deposited directly from the feedstock respond differently to dynamic nuclear polarization signal enhancement in integral and crushed FCC particles, indicating that aromatic species are mostly concentrated on the outside of the catalyst particles, whereas aliphatic species are also located on the inside of the FCC particles. The comparison of solid-state NMR data with and without the DNP radical at low and ambient temperature suggests the proximity between aromatic carbon deposits and metals (mostly iron) on the catalyst surface. These findings potentially indicate that coke and iron deposit together, or that iron has a role in the formation of aromatic coke.

Wednesday, June 21, 2017

Facet dependent pairwise addition of hydrogen over Pd nanocrystal catalysts revealed via NMR using para-hydrogen-induced polarization


Wang, W., et al., Facet dependent pairwise addition of hydrogen over Pd nanocrystal catalysts revealed via NMR using para-hydrogen-induced polarization. Phys. Chem. Chem. Phys., 2017. 19(14): p. 9349-9353.


We demonstrated the facet dependence of pairwise addition of hydrogen in heterogeneous catalysis over Pd nanocrystal catalysts via NMR using para-hydrogen-induced polarization.

Monday, June 19, 2017

NMR signal enhancement of >50 000 times in fast dissolution dynamic nuclear polarization


Pinto, L.F., et al., NMR signal enhancement of >50 000 times in fast dissolution dynamic nuclear polarization. Chem Commun (Camb), 2017. 53(26): p. 3757-3760.


Herein, we report the synthesis and the study of a novel mixed biradical with BDPA and TEMPO radical units that are covalently bound by an ester group (BDPAesterTEMPO) as a polarizing agent for fast dissolution DNP. The biradical exhibits an extremely high DNP NMR enhancement of >50 000 times, which constitutes one of the largest signal enhancements observed so far, to the best of our knowledge.

Friday, June 16, 2017

Probing Surface Hydrogen Bonding and Dynamics by Natural Abundance, Multidimensional,17O DNP-NMR Spectroscopy #DNPNMR


Perras, F.A., et al., Probing Surface Hydrogen Bonding and Dynamics by Natural Abundance, Multidimensional,17O DNP-NMR Spectroscopy. The Journal of Physical Chemistry C, 2016. 120(21): p. 11535-11544.


Dynamic nuclear polarization (DNP)-enhanced solid-state nuclear magnetic resonance (SSNMR) spectroscopy is increasingly being used as a tool for the atomic-level characterization of surface sites. DNP surface-enhanced SSNMR spectroscopy of materials has, however, been limited to studying relatively receptive nuclei, and the particularly rare 17O nuclide, which is of great interest for materials science, has not been utilized. We demonstrate that advanced 17O SSNMR experiments can be performed on surface species at natural isotopic abundance using DNP. We use 17O DNP surface-enhanced 2D SSNMR to measure 17O{1H} HETCOR spectra as well as dipolar oscillations on a series of thermally treated mesoporous silica nanoparticle samples having different pore diameters. These experiments allow for a nonintrusive and unambiguous characterization of hydrogen bonding and dynamics at the surface of the material; no other single experiment can give such details about the interactions at the surface. Our data show that, upon drying, strongly hydrogen-bonded surface silanols, whose motions are greatly restricted by the interaction when compared to lone silanols, are selectively dehydroxylated.

Thursday, June 15, 2017

[NMR] Permanent Solid-State NMR Position in Reading, UK, with Johnson Matthey Plc

From the Ampere Magnetic Resonance List




Johnson Matthey PLC is a world leader in advanced materials and catalyst technology with over 13 000 employees worldwide. The Technology Centre, based at Sonning Common, undertakes research work for the group.

Key to the work of the research teams the Advanced Characterisation Group takes responsibility for development, operation and interpretation of analyses arising from bespoke methodologies across our suite of start of the art instrumentation. Due to the purchase of a new 600 MHz solid-state NMR system, we are expanding the spectroscopy team to someone with a specialism in Solid-State NMR.

Key responsibilities: 
Maintaining high EHS standards,
Defining and developing the instrument capabilities to maintain start-of-the-art analysis,
Continuously improving the workflow, sample preparation, and data analysis methods to improve service efficiency, repeatability and insight into materials,
Collaborating with other researchers inside and outside the company to leverage expertise,
Continued personal and professional development.

Are you the ideal candidate? You will have:
A PhD in Physics, materials science or Chemistry or equivalent experience,
Demonstrated expertise in Solid State NMR,
Experience performing DFT calculations,
Excellent analytical ability and attention to detail,
Software knowledge of Adobe Illustrator, LaTeX code, MS Office,
A strong fascination for technology and the application of materials in an industrial context,
The ability to develop new collaborations across academic and industrial sectors,
A demonstrable ability to innovate.

We offer a competitive package including, amongst other benefits, a company pension scheme, 25 days annual leave, medical benefits and after a qualifying period, a share incentive plan. All employees are encouraged to further their personal development through training and education by the Company.

Apply though Taleo at http://bit.ly/2tlitu7


If the reader of this email is not the intended recipient(s), please be advised that any dissemination, distribution or copying of this information is strictly prohibited. Johnson Matthey Plc has its main place of business at 5th Floor, 25 Farringdon Street, London (020 7269 8400).

Johnson Matthey Public Limited Company
Registered Office: 5th Floor, 25 Farringdon Street, London EC4A 4AB
Registered in England No 33774

Whilst Johnson Matthey aims to keep its network free from viruses you should note that we are unable to scan certain emails, particularly if any part is encrypted or password-protected, and accordingly you are strongly advised to check this email and any attachments for viruses. The company shall not accept any liability with regard to computer viruses transferred by way of email.

Please note that your communication may be monitored in accordance with Johnson Matthey internal policy documentation.


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Monday, June 12, 2017

Characterizing Substrate-Surface Interactions on Alumina-Supported Metal Catalysts by Dynamic Nuclear Polarization-Enhanced Double-Resonance NMR Spectroscopy #DNPNMR


Perras, F.A., et al., Characterizing Substrate-Surface Interactions on Alumina-Supported Metal Catalysts by Dynamic Nuclear Polarization-Enhanced Double-Resonance NMR Spectroscopy. J Am Chem Soc, 2017. 139(7): p. 2702-2709.


The characterization of nanometer-scale interactions between carbon-containing substrates and alumina surfaces is of paramount importance to industrial and academic catalysis applications, but it is also very challenging. Here, we demonstrate that dynamic nuclear polarization surface-enhanced NMR spectroscopy (DNP SENS) allows the unambiguous description of the coordination geometries and conformations of the substrates at the alumina surface through high-resolution measurements of 13C-27Al distances. We apply this new technique to elucidate the molecular-level geometry of 13C-enriched methionine and natural abundance poly(vinyl alcohol) adsorbed on gamma-Al2O3-supported Pd catalysts, and we support these results with element-specific X-ray absorption near-edge measurements. This work clearly demonstrates a surprising bimodal coordination of methionine at the Pd-Al2O3 interface.

SABRE Hyperpolarization of Bipyridine Stabilized Ir-Complex at High, Low and Ultralow Magnetic Fields


Pravdivtsev Andrey, N., SABRE Hyperpolarization of Bipyridine Stabilized Ir-Complex at High, Low and Ultralow Magnetic Fields, in Zeitschrift für Physikalische Chemie. 2017. p. 497.


A strong limitation of nuclear magnetic resonance is its low inherent sensitivity that can be overcome by using an appropriate hyperpolarization technique. Presently, dynamic nuclear polarization and spin-exchange optical pumping are the only hyperpolarization techniques that are used in applied medicine. However, both are relatively complex in use and expensive. Here we present a modification of the signal amplification by reversible exchange (SABRE) hyperpolarization method – SABRE on stabilized Ir-complexes. A stabilized Ir-complex (here we used bipyridine for stabilization) can be hyperpolarized in a wide range of magnetic fields from a few μT upto 10 T with 15N polarization of about 1–3%. Moreover, the investigated complex can be incorporated into biomolecules or other bulky molecules; in this situation exchange with para-hydrogen will allow one to continuously generate hyperpolarization.

Friday, June 9, 2017

Oxygen-17 dynamic nuclear polarisation enhanced solid-state NMR spectroscopy at 18.8 T #DNPNMR


Brownbill, N.J., et al., Oxygen-17 dynamic nuclear polarisation enhanced solid-state NMR spectroscopy at 18.8 T. Chem Commun (Camb), 2017. 53(17): p. 2563-2566.


We report 17O dynamic nuclear polarisation (DNP) enhanced solid-state NMR experiments at 18.8 T. Several formulations were investigated on the Mg(OH)2 compound. A signal enhancement factor of 17 could be obtained when the solid particles were incorporated into a glassy o-terphenyl matrix doped with BDPA using the Overhauser polarisation transfer scheme whilst the cross effect mechanism enabled by TEKPol yielded a slightly lower enhancement but more time efficient data acquisition.

Monday, June 5, 2017

Surface-selective direct 17O DNP NMR of CeO2 nanoparticles #DNPNMR


Hope, M.A., et al., Surface-selective direct 17O DNP NMR of CeO2 nanoparticles. Chem Commun (Camb), 2017. 53(13): p. 2142-2145.


Surface-selective direct 17O DNP has been demonstrated for the first time on CeO2 nanoparticles, for which the first three layers can be distinguished with high selectivity. Polarisation build-up curves show that the polarisation of the (sub-)surface sites builds up faster than the bulk, accounting for the remarkable surface selectivity.

A tailored multi-frequency EPR approach to accurately determine the magnetic resonance parameters of dynamic nuclear polarization agents: application to AMUPol #DNPNMR


This is a very nice article illustrating the importance of understanding the EPR parameters of a polarizing agent used in DNP-NMR spectroscopy. Here the 9, 95 and 275 GHz EPR spectroscopy is used to characterize AMUPol and predict its performance in high-field DNP.



Gast, P., et al., A tailored multi-frequency EPR approach to accurately determine the magnetic resonance parameters of dynamic nuclear polarization agents: application to AMUPol. Phys. Chem. Chem. Phys., 2017. 19(5): p. 3777-3781.


To understand the dynamic nuclear polarization (DNP) enhancements of biradical polarizing agents, the magnetic resonance parameters need to be known. We describe a tailored EPR approach to accurately determine electron spin-spin coupling parameters using a combination of standard (9 GHz), high (95 GHz) and ultra-high (275 GHz) frequency EPR. Comparing liquid- and frozen-solution continuous-wave EPR spectra provides accurate anisotropic dipolar interaction D and isotropic exchange interaction J parameters of the DNP biradical AMUPol. We found that D was larger by as much as 30% compared to earlier estimates, and that J is 43 MHz, whereas before it was considered to be negligible. With the refined data, quantum mechanical calculations confirm that an increase in dipolar electron-electron couplings leads to higher cross-effect DNP efficiencies. Moreover, the DNP calculations qualitatively reproduce the difference of TOTAPOL and AMUPol DNP efficiencies found experimentally and suggest that AMUPol is particularly effective in improving the DNP efficiency at magnetic fields higher than 500 MHz. The multi-frequency EPR approach will aid in predicting the optimal structures for future DNP agents.

[NMR] PhD position in solid-state NMR of paramagnetic materials

A PhD position is available in the group of Andrew Pell at the Department of Materials Environmental and Environmental Chemistry (MMK), Stockholm University (Sweden), in solid-state NMR of paramagnetic materials.
Closing date: August 7, 2017.

Project description
The aim of our research is to develop solid-state nuclear magnetic resonance (NMR) methods in order to allow a more accurate characterization, at the atomic scale, of the structure and dynamics of increasingly complex materials that are relevant in modern material science and chemistry. Specifically we focus on systems that contain paramagnetic metal ions, and how these ions dictate the properties of technologically important materials such as batteries, catalysts, and solid-state lighting phosphors.

Solid-state NMR is the method of choice for studying local structure and dynamics. However many interesting paramagnetic materials are, for technical reasons, beyond the ability of the current state of the art in solid-state NMR to study. This PhD project is therefore focussed on developing and specifically tailoring the techniques and capabilities of solid-state NMR for the analysis of samples containing these metal ions; for characterizing their presence, activity, role, and function in a range of different materials. Specifically the PhD student will develop new pulse schemes for exciting and detecting the NMR signals from quadrupolar nuclei (such as 2H, 14N, 23Na, 25Al, …) in paramagnetic materials, and incorporate these new schemes into more sophisticated experiments in order to separate the information from different spin interactions, which can then be interpreted in terms of both the structure and dynamics of the system. These new methods will then be applied to a range of paramagnetic materials, such as battery electrodes, ion conductors, or inorganic phosphors, with the specific choice depending on the interests of the student.

The student will acquire expertise in both the theoretical and experimental aspects of solid-state NMR on 400 and 600 MHz Bruker spectrometers. There will also be opportunities to travel to high-field NMR centres both within Sweden and Europe. Following the development of the new NMR methods the student will have the opportunity to apply them on a range of different materials that have been developed both at MMK and in collaboration with other laboratories around the world.

The project is interdisciplinary and contains elements from chemistry and physics. Therefore, strongly motivated students with a background in these areas, and particularly those with an interest in quantum mechanics, are encouraged to apply.

The Department of Materials and Environmental Chemistry, Stockholm University
The Department of Materials- and Environmental Chemistry (MMK) is one of the largest departments at the Faculty of Natural sciences with about 140 employees. The research activities of MMK are in the areas of Materials and Solid-state Chemistry focusing on different classes of materials; e.g. ceramics and glasses, self-assembled and porous materials, and soft matter. The work often encompasses synthesis, characterisation by X-ray diffraction and electron microscopy, NMR studies, modelling with computer simulations of materials with a potential for various applications. Environmental aspects are an important part of the research activities.

Application
For informal enquiries, email Andrew Pell at andrew.pell@mmk.su.se.
To obtain more information about the position, how to apply, and to submit your application visit http://www.su.se/english/about/vacancies/vacancies-new-list?rmpage=job&rmjob=3062&rmlang=UK

---------------------------------------------------
Andrew J. Pell
Assistant Professor

Department of Materials and Environmental Chemistry,
Arrhenius Laboratory,
Stockholm University,
Svante Arrhenius väg 16C,
SE-106 91 Stockholm,
Sweden


Tel: +46 (0)8-16 23 76

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Friday, June 2, 2017

Effect of electron spectral diffusion on static dynamic nuclear polarization at 7 Tesla #DNPNMR


Leavesley, A., et al., Effect of electron spectral diffusion on static dynamic nuclear polarization at 7 Tesla. Phys. Chem. Chem. Phys., 2017. 19(5): p. 3596-3605.


Here, we present an integrated experimental and theoretical study of 1H dynamic nuclear polarization (DNP) of a frozen aqueous glass containing free radicals at 7 T, under static conditions and at temperatures ranging between 4 and 20 K. The DNP studies were performed with a home-built 200 GHz quasi-optics microwave bridge, powered by a tunable solid-state diode source. DNP using monochromatic and continuous wave (cw) irradiation applied to the electron paramagnetic resonance (EPR) spectrum of the radicals induces the transfer of polarization from the electron spins to the surrounding nuclei of the solvent and solutes in the frozen aqueous glass. In our systematic experimental study, the DNP enhanced 1H signals are monitored as a function of microwave frequency, microwave power, radical concentration, and temperature, and are interpreted with the help of electron spin-lattice relaxation times, experimental MW irradiation parameters, and the electron spectral diffusion (eSD) model introduced previously. This comprehensive experimental DNP study with mono-nitroxide radical spin probes was accompanied with theoretical calculations. Our results consistently demonstrate that eSD effects can be significant at 7 T under static DNP conditions, and can be systematically modulated by experimental conditions.

Wednesday, May 31, 2017

Fast and accurate MAS-DNP simulations of large spin ensembles #DNPNMR


Mentink-Vigier, F., S. Vega, and G. De Paepe, Fast and accurate MAS-DNP simulations of large spin ensembles. Phys. Chem. Chem. Phys., 2017. 19(5): p. 3506-3522.


A deeper understanding of parameters affecting Magic Angle Spinning Dynamic Nuclear Polarization (MAS-DNP), an emerging nuclear magnetic resonance hyperpolarization method, is crucial for the development of new polarizing agents and the successful implementation of the technique at higher magnetic fields (>10 T). Such progress is currently impeded by computational limitation which prevents the simulation of large spin ensembles (electron as well as nuclear spins) and to accurately describe the interplay between all the multiple key parameters at play. In this work, we present an alternative approach to existing cross-effect and solid-effect MAS-DNP codes that yields fast and accurate simulations. More specifically we describe the model, the associated Liouville-based formalism (Bloch-type derivation and/or Landau-Zener approximations) and the linear time algorithm that allows computing MAS-DNP mechanisms with unprecedented time savings. As a result, one can easily scan through multiple parameters and disentangle their mutual influences. In addition, the simulation code is able to handle multiple electrons and protons, which allows probing the effect of (hyper)polarizing agents concentration, as well as fully revealing the interplay between the polarizing agent structure and the hyperfine couplings, nuclear dipolar couplings, nuclear relaxation times, both in terms of depolarization effect, but also of polarization gain and buildup times.

Friday, May 26, 2017

Nuclear-Electron Overhauser Effect in MC800 Liquid Asphalt Solutions


Yet another application (although not new) for Overhauser DNP at 9 GHz. 





Firat, Y.E., H. Yildirim, and A. Peksoz, Nuclear-Electron Overhauser Effect in MC800 Liquid Asphalt Solutions. Journal of Dispersion Science and Technology, 2015. 37(9): p. 1349-1359.


Experimental results on the extrapolated ultimate enhancement factors of o-, m-, and p-xylene protons at 1.53 mT are obtained for MC800 asphalt solutions. The ultimate enhancement factors are found such as ?26.9, ?25.7, and ?11.7 for o-, m-, and p-xylene, respectively. These results show that the solvent proton Overhauser effect cannot reach the extrapolated enhancement of ?330 in the extreme narrowing case because of occurrence of small scalar interactions in addition to the dipole?dipole interactions between solvent protons and asphalt electrons. The ortho, meta, and para positions of the ?CH3 group change the nature of the interactions. The nuclear magnetic resonance (NMR) signal enhancements exhibit a sensitive behavior depending on the chemical environment differing from isomer to isomer. The solvation or association of asphalt in xylene isomers at room temperature is revealed. Quantum chemical calculations for the xylene isomers with the electronic and optical properties; absorption wavelengths, excitation energy, atomic charges, dipole moment and frontier molecular orbital energies, molecular electrostatic potential; are carried out using the density functional theory (DFT) method (B3LYP) with the 6-311G(d,p) basis set by the standard Gaussian 09 software package program. The relative importance of scalar and translational dipolar interaction parameters determined in dynamic nuclear polarization experiments is explained by the electronic structure of HOMO?LUMO of the xylene isomers.

Wednesday, May 24, 2017

High field hyperpolarization-EXSY experiment for fast determination of dissociation rates in SABRE complexes


Hermkens, N.K.J., et al., High field hyperpolarization-EXSY experiment for fast determination of dissociation rates in SABRE complexes. J. Magn. Reson., 2017. 276: p. 122-127.


SABRE (Signal Amplification By Reversible Exchange) is a nuclear spin hyperpolarization technique based on the reversible concurrent binding of small molecules and para-hydrogen (p-H2) to an iridium metal complex in solution. At low magnetic field, spontaneous conversion of p-H2 spin order to enhanced longitudinal magnetization of the nuclear spins of the other ligands occurs. Subsequent complex dissociation results in hyperpolarized substrate molecules in solution. The lifetime of this complex plays a crucial role in attained SABRE NMR signal enhancements. Depending on the ligands, vastly different dissociation rates have been previously measured using EXSY or selective inversion experiments. However, both these approaches are generally time-consuming due to the long recycle delays (up to 2 min) necessary to reach thermal equilibrium for the nuclear spins of interest. In the cases of dilute solutions, signal averaging aggravates the problem, further extending the experimental time. Here, a new approach is proposed based on coherent hyperpolarization transfer to substrate protons in asymmetric complexes at high magnetic field. We have previously shown that such asymmetric complexes are important for application of SABRE to dilute substrates. Our results demonstrate that a series of high sensitivity EXSY spectra can be collected in a short experimental time thanks to the NMR signal enhancement and much shorter recycle delay.

Monday, May 22, 2017

Molecular dynamics-based selectivity for Fast-Field-Cycling relaxometry by Overhauser and solid effect dynamic nuclear polarization #DNPNMR


Neudert, O., C. Mattea, and S. Stapf, Molecular dynamics-based selectivity for Fast-Field-Cycling relaxometry by Overhauser and solid effect dynamic nuclear polarization. J. Magn. Reson., 2017. 276: p. 113-121.


In the last decade nuclear spin hyperpolarization methods, especially Dynamic Nuclear Polarization (DNP), have provided unprecedented possibilities for various NMR techniques by increasing the sensitivity by several orders of magnitude. Recently, in-situ DNP-enhanced Fast Field Cycling (FFC) relaxometry was shown to provide appreciable NMR signal enhancements in liquids and viscous systems. In this work, a measurement protocol for DNP-enhanced NMR studies is introduced which enables the selective detection of nuclear spin hyperpolarized by either Overhauser effect or solid effect DNP. Based on field-cycled DNP and relaxation studies it is shown that these methods allow for the independent measurement of polymer and solvent nuclear spins in a concentrated solution of high molecular weight polybutadiene in benzene doped with α,γ-bisdiphenylene-β-phenylallyl radical. Appreciable NMR signal enhancements of about 10-fold were obtained for both constituents. Moreover, qualitative information about the dynamics of the radical and solvent was obtained. Selective DNP-enhanced FFC relaxometry is applied for the measurement of the 1H nuclear magnetic relaxation dispersion of both constituents with improved precision. The introduced method is expected to greatly facilitate NMR studies of complex systems with multiple overlapping signal contributions that cannot be distinguished by standard methods.

Friday, May 19, 2017

T1 - Dynamic Nuclear Polarization Signal Enhancement with High-Affinity Biradical Tags #DNPNMR

Rivkah Rogawski, Ivan V. Sergeyev, Yongjun Li, M. Francesca Ottaviani, Virginia Cornish, and Ann E. McDermott The Journal of Physical Chemistry B 2017 121 (6), 1169-1175


Dynamic nuclear polarization is an emerging technique for sensitizing solid-state NMR experiments by transferring polarization from electrons to nuclei. Stable biradicals, the polarization source for the cross effect mechanism, are typically codissolved at millimolar concentrations with proteins of interest. Here we describe the high-affinity biradical tag TMP-T, created by covalently linking trimethoprim, a nanomolar affinity ligand of dihydrofolate reductase (DHFR), to the biradical polarizing agent TOTAPOL. With TMP-T bound to DHFR, large enhancements of the protein spectrum are observed, comparable to when TOTAPOL is codissolved with the protein. In contrast to TOTAPOL, the tight binding TMP-T can be added stoichiometrically at radical concentrations orders of magnitude lower than in previously described preparations. Benefits of the reduced radical concentration include reduced spectral bleaching, reduced chemical perturbation of the sample, and the ability to selectively enhance signals for the protein of interest.

Thursday, May 18, 2017

[NMR] Postdoc in biomolecular SSNMR - protein aggregation & protein-lipid interactions


Postdoctoral position in biological MAS ssNMR

The Van der Wel lab is looking for a postdoc candidate with a background in NMR, preferably solid-state NMR, to join our research effort focused on protein aggregation and protein-lipid interactions. More information on our research and recent publications can be found below and on our website at http://www.vanderwellab.org

Potentially interested parties are encouraged to email any questions and/or (informal) inquiries to vanderwel@pitt.edu

Patrick van der Wel
-----------------------------------

Research topics: 

The researcher is expected to join the Van der Wel lab to contribute to our NIH-funded research. One focus in the lab is the use of MAS NMR to study amyloid structure and protein aggregation with a particular focus on polyglutamine-expanded proteins implicated in Huntington’s Disease. Another key focus is on the study by ssNMR of membrane structure and dynamics, as well as protein-lipid interactions, in particular in context of mitochondrial apoptosis, which has important implications for neurodegenerative disease and cancer research. 

Selected recent publications: (online access here )

  • Mandal et al. (2015) Structural Changes and Proapoptotic Peroxidase Activity of Cardiolipin-Bound Mitochondrial Cytochrome c. Biophys. J., 109(9), 1873–84.
  • Hoop et al. (2016) Huntingtin exon 1 fibrils feature an interdigitated β-hairpin-based polyglutamine core. PNAS, 113(6), 1546–51. 
  • Merg et al. (2016) Peptide-Directed Assembly of Single-Helical Gold Nanoparticle Superstructures Exhibiting Intense Chiroptical Activity. JACS, 138(41), 13655–63. 
  • Boatz et al. (2017) Cataract-associated P23T γD-crystallin retains a native-like fold in amorphous-looking aggregates formed at physiological pH. Nat Commun, 8, 15137. 

Location/Resources:

Our facility houses wide-bore 600MHz and 750MHz Bruker ssNMR spectrometers outfitted with 4-, 3.2-, 1.9-, and 1.3-mm CP/MAS as well as static ssNMR probes. Additional facilities include state-of-the-art EM, X-ray and solution NMR instrumentation, with the latter including 700, 800, and 900 MHz spectrometers. Excellent resources are available for protein production, biophysical and computational studies. The lab is housed in the interdisciplinary Dept of Structural Biology, one of the basic science departments of the University of Pittsburgh School of Medicine in Pittsburgh, Pennsylvania (USA). 

Application/More Information.

For more detailed information on these projects, links to related publications, and other information please visit the lab website at http://www.vanderwellab.org. To apply, or to obtain more information, please contact Patrick van der Wel by email at vanderwel@pitt.edu. Applications are expected to include a cover letter (or “cover email”) explaining specific research interests, a CV, and the names and contact information for three reference writers.

-----------------------------------

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[NMR] Postdoctoral position in structural biology of membrane remodeling



POSTDOCTORAL POSITION AVAILABLE
STRUCTURAL BIOLOGY OF MEMBRANE REMODELING

A NIH-funded postdoctoral position is available immediately in the Ramachandran Lab at Case Western Reserve University (CWRU) to study the structural aspects of protein-mediated membrane remodeling during endocytic and mitochondrial membrane fission. This position involves extensive collaboration with the lab of Patrick van der Wel at the University of Pittsburgh. The position requires a Ph.D. in biochemistry or biophysics with a focus on structural biology or membrane biophysics (NMR or ssNMR, preferably). This position will provide an excellent opportunity to learn and apply a wide array of structural and biophysical techniques to explore protein function on a model membrane surface. The Ramachandran laboratory also employs a host of cutting-edge spectroscopic approaches including FRET, fluorescence correlation spectroscopy (FCS) and fluorescence lifetime imaging (FLIM) to explore protein-protein and protein-membrane interactions in membrane remodeling and fission, both in vitro and in vivo. The Ramachandran and Van der Wel labs and the facilities at CWRU and University of Pittsburgh are equipped with state-of-the-art instrumentation for both biophysical techniques and structural biology, as well as for protein purification, characterization and membrane reconstitution.

Requirements: Applicants must be highly motivated and must have demonstrated experience (i.e. relevant publications) in protein biochemistry and structural biology. The candidate should have a strong conceptual and experimental background in biochemistry and biophysics, as well as in the mechanistic dissection of structure-function relationships in proteins; he/she should be independent, proactive, hardworking and productive; only candidates that have first-author publications (or articles in press) will be considered. Candidates must have completed their PhD at the time of appointment. Salary will commensurate with experience and will adhere to current NIH guidelines. Interested candidates should submit their CV, reprints of selected publications, three reference letters (directly from referees), and a cover letter summarizing their experience, long-term goals, and estimated start date directly to Rajesh Ramachandran at rxr275@case.edu.

Relevant Publications, please visit our webpage:

Van der Wel lab: http://www.vanderwellab.org

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[NMR] Position as Research Engineer / Lab Manager for the magnetic resonance lab @ IPF Dresden


Position as Research Engineer / Lab Manager for the magnetic resonance lab @ IPF Dresden

At the Institute of Physical Chemistry and Polymer Physics, Department Polyelectrolytes and Dispersions, at the 

Leibniz-Institut für Polymerforschung is an opening for a Research Engineer / Lab Manager for the magnetic resonance laboratory. 

We are looking for a motivated, skillful person, who is willing to learn about novel technolgies and is closely collaborating with the PI's. The research engineer will be responsible for ensuring the operation of the laboratory and the various spectrometers (high-field NMR, low-field NMR and X-band EPR), perform routine experiments and sample preparation and support in simulations. Ensuring the smooth operation of the lab includes trouble shooting and modification of experimental setups. Skills in electronics and computing are desirable.

Qualification: MSc/Diploma in Physical Technology or equivalent
Duration: initially for two years

The Leibniz-Institut für Polymerforschung Dresden e.V. (IPF) is one of the largest polymer research facilities in Germany. As an institute of the Leibniz Association, the IPF is committed to carrying out application-oriented basic research. The focus of activities at the IPF is directed toward the advancement of basic scientific knowledge for the development of functional polymer materials and polymer materials with new or improved characteristics. Leading scientists of the IPF are at the same time appointed professors at the Technische Universität Dresden (TUD). Since 2011 the TUD has been one of the excellence universities in Germany. The IPF offers a stimulating working atmosphere for outstanding interdisciplinary research in one of the most beautiful cities of Germany. 

Dresden, the capital of Saxony, possesses an extraordinarily high density of research facilities which have made Dresden a leading research site, particularly in the fields of material research, microelectronics, and biotechnology. 

Applications including motivation letter, CV, should be submitted by e-mail as a single PDF document to the Department of Human Resources (with the No. 063-2017):

Leibniz-Institut für Polymerforschung Dresden e.V.
Frau Susanne Otto
Leiterin Personal und Soziales
Hohe Straße 6
01069 Dresden

Queries about the lab and the research project should be directed by e-mail to:
Ulrich Scheler Scheler@ipfdd.de .

Job offer (in German)

Best regards,
Ulrich Scheler

-------------------------------------------------------------
Dr. Ulrich Scheler
Leibniz-Institut für Polymerforschung Dresden e.V.
Hohe Strasse 6
D-01069 Dresden, Germany
phone +49 351 4658 275
fax +49 351 4658 231
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Wednesday, May 17, 2017

Surface-selective direct 17O DNP NMR of CeO2 nanoparticles #DNPNMR

Michael A. Hope et. al, Chem. Commun., 2017,53, 2142-2145 


Surface-selective direct 17O DNP has been demonstrated for the first time on CeO2nanoparticles, for which the first three layers can be distinguished with high selectivity. Polarisation build-up curves show that the polarisation of the (sub-)surface sites builds up faster than the bulk, accounting for the remarkable surface selectivity.

Monday, May 15, 2017

Site specific polarization transfer from a hyperpolarized ligand of dihydrofolate reductase


Wang, Y., M. Ragavan, and C. Hilty, Site specific polarization transfer from a hyperpolarized ligand of dihydrofolate reductase. J. Biomol. NMR, 2016. 65(1): p. 41-48.


Protein–ligand interaction is often characterized using polarization transfer by the intermolecular nuclear Overhauser effect (NOE). For such NOE experiments, hyperpolarization of nuclear spins presents the opportunity to increase the spin magnetization, which is transferred, by several orders of magnitude. Here, folic acid, a ligand of dihydrofolate reductase (DHFR), was hyperpolarized on 1H spins using dissolution dynamic nuclear polarization (D-DNP). Mixing hyperpolarized ligand with protein resulted in observable increases in protein 1H signal predominantly in the methyl group region of the spectra. Using 13C single quantum selection in a series of one-dimensional spectra, the carbon chemical shift ranges of the corresponding methyl groups can be elucidated. Signals observed in these hyperpolarized spectra could be confirmed using 3D isotope filtered NOESY spectra, although the hyperpolarized spectra were obtained in single scans. By further correlating the signal intensities observed in the D-DNP experiments with the occurrence of short distances in the crystal structure of the protein–ligand complex, the observed methyl proton signals could be matched to the chemical shifts of six amino acids in the active site of DHFR-folic acid binary complex. These data demonstrate that 13C chemical shift selection of protein resonances, combined with the intrinsic selectivity towards magnetization originating from the initially hyperpolarized spins, can be used for site specific characterization of protein–ligand interactions.

Friday, May 12, 2017

Hyperpolarized 13C pyruvate mouse brain metabolism with absorptive-mode EPSI at 1T


Miloushev, V.Z., et al., Hyperpolarized 13C pyruvate mouse brain metabolism with absorptive-mode EPSI at 1T. J Magn Reson, 2017. 275: p. 120-126.


The expected signal in echo-planar spectroscopic imaging experiments was explicitly modeled jointly in spatial and spectral dimensions. Using this as a basis, absorptive-mode type detection can be achieved by appropriate choice of spectral delays and post-processing techniques. We discuss the effects of gradient imperfections and demonstrate the implementation of this sequence at low field (1.05T), with application to hyperpolarized [1-13C] pyruvate imaging of the mouse brain. The sequence achieves sufficient signal-to-noise to monitor the conversion of hyperpolarized [1-13C] pyruvate to lactate in the mouse brain. Hyperpolarized pyruvate imaging of mouse brain metabolism using an absorptive-mode EPSI sequence can be applied to more sophisticated murine disease and treatment models. The simple modifications presented in this work, which permit absorptive-mode detection, are directly translatable to human clinical imaging and generate improved absorptive-mode spectra without the need for refocusing pulses.

Wednesday, May 10, 2017

Peptide and Protein Dynamics and Low-Temperature/DNP Magic Angle Spinning NMR #DNPNMR


Ni, Q.Z., et al., Peptide and Protein Dynamics and Low-Temperature/DNP Magic Angle Spinning NMR. J Phys Chem B, 2017.


In DNP MAS NMR experiments at ~80-110 K, the structurally important -13CH3 and -15NH3+ signals in MAS spectra of biological samples disappear due to the interference of the molecular motions with the 1H decoupling. Here we investigate the effect of these dynamic processes on the NMR lineshapes and signal intensities in several typical systems: (1) microcrystalline APG, (2) membrane protein bR, (3) amyloid fibrils PI3-SH3, (4) monomeric alanine-CD3 and (5) the pro-tonated and deuterated dipeptide N-Ac-VL over 78-300 K. In APG, the 3-site hopping of the Ala-Cbeta peak disappears com-pletely at 112 K, concomitant with the attenuation of CP signals from other 13C's and 15N's. Similarly, the 15N signal from Ala-NH3+ disappears ~173 K, concurrent with the attenuation in CP experiments of other 15N's as well as 13C's. In bR and PI3-SH3, the methyl groups are attenuated at ~95 K while all other 13C's remain unaffected. However, both systems exhibit substantial losses of intensity at ~243 K. Finally, with spectra of Ala and N-Ac-VL we show that it is possible to extract site specific dynamic data from the temperature dependence of the intensity losses. Furthermore, 2H labeling can assist with re-covering the spectral intensity. Thus, our study provides insight into the dynamic behavior of biological systems over a wide range of temperatures, and serves as a guide to optimizing the sensitivity and resolution of structural data in low temperature DNP MAS NMR spectra.

Monday, May 8, 2017

[NMR] PhD position in EPR & NMR at IPF Dresden

PhD position on EPR and NMR at the Leibniz Institute of Polymer Research Dresden, Germany

The Institute of Physical Chemistry and Polymer Physics, department Polyelectrolytes and Dispersions, at the Leibniz Institute of Polymer Research Dresden offers a position for a research assistant / PhD student (Chemist/Physicist). 

Project: Investigations on the dynamics of polyelectrolyte multilayers by spin-labeling and EPR spectroscopy (funded by Deutsche Forschungsgemeinschaft)

Salary 2/3 position TV-L EG 13 (26 hours/week). 

Start: asap
Duration: 31.03.2020
Qualification: MSc degree/diploma in Chemistry or Physics

Project description: Subject of the project are polyelectrolyte multilayers that can be prepared by alternating adsorption of polyanions and polycations using the Layer-by-layer technique on various substrates. It is a general and broadly applicable technique that enables manufacturing numerous different tailored structures. Polyelectrolyte multilayers find increasing attention in the targeted modification of surfaces and membranes. 

Various aspects, such as the growth mechanism, the internal structure of the layers as well as the dynamics are of fundamental interest for practical applications. While many details of the structures are known, there is much less knowledge for no less important dynamics of polymers in the multilayers. 

The aim of the project is to gain new insights into the mobility of chain segments of polyelectrolytes in multilayers and to show correlations between the internal structure and dynamics in these multilayers and resulting properties. 

In order to achieve this goal polyelectrolyte molecules are equipped with spin labels and incorporated in a defined manner in the PEM. The EPR spectroscopy offer the potential to study the rotational diffusion of the spin label linked to the macromolecule and to gain quantitative information about the mobility of polymer segments, which are complemented by NMR data,which are sensitive to longer time scales. 

The experimental investigations aim at the relationships between the chemical structure of the polyelectrolytes used, the conditions at the preparation of the PEM and the parameters of the surrounding medium (ionic strength, pH) and the mobility of polymer segments in different zones of the multilayer. 

The internal dynamics of the polyelectrolytes in the multilayers has an influence on the transport in the multilayer and through the multilayer when it is used as a membrane. The correlation of the temperature dependence of the polymer dynamics and the diffusion of small guest molecules results in insights in the mechanism of transport.

The Leibniz Institute of Polymer Research Dresden (IPF) is one of the largest polymer research facilities in Germany. As an institute of the Leibniz Association, the IPF is committed to carrying out application-oriented basic research. The focus of activities at the IPF is directed toward the advancement of basic scientific knowledge for the development of functional polymer materials and polymer materials with new or improved characteristics. Leading scientists of the IPF are at the same time appointed professors at the Technische Universität Dresden (TUD). Since 2011 the TUD has been one of the excellence universities in Germany. The IPF offers a stimulating working atmosphere for outstanding interdisciplinary research in one of the most beautiful cities of Germany. 

Dresden, the capital of Saxony, possesses an extraordinarily high density of research facilities which have made Dresden a leading research site, particularly in the fields of material research, microelectronics, and biotechnology. 

Applications including motivation letter, CV, should be submitted by e-mail as a single PDF document to the Department of Human Resources (with the No. 083-2017):

Leibniz-Institut für Polymerforschung Dresden e.V.
Frau Susanne Otto
Leiterin Personal und Soziales
Hohe Straße 6
01069 Dresden

Queries about the lab and the research project should be directed by e-mail to:
Ulrich Scheler Scheler@ipfdd.de or Uwe Lappan Lappan@ipfdd.de .

Job offer (in German)

Best regards,
Ulrich Scheler

-------------------------------------------------------------
Dr. Ulrich Scheler
Leibniz-Institut für Polymerforschung Dresden e.V.
Hohe Strasse 6
D-01069 Dresden, Germany
phone +49 351 4658 275
fax +49 351 4658 231
--------------------------------------------------------------


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