Mar 20, 2019

Experimental quantification of electron spectral-diffusion under static DNP conditions #DNPNMR

Kundu, Krishnendu, Marie Ramirez Cohen, Akiva Feintuch, Daniella Goldfarb, and Shimon Vega. “Experimental Quantification of Electron Spectral-Diffusion under Static DNP Conditions.” Physical Chemistry Chemical Physics 21, no. 1 (2019): 478–89.


Dynamic Nuclear Polarization (DNP) is an efficient technique for enhancing NMR signals by utilizing the large polarization of electron spins to polarize nuclei. The mechanistic details of the polarization transfer process involve the depolarization of the electrons resulting from microwave (MW) irradiation (saturation), as well as electron–electron cross-relaxation occurring during the DNP experiment. Recently, electron–electron double resonance (ELDOR) experiments have been performed under DNP conditions to map the depolarization profile along the EPR spectrum as a consequence of spectral diffusion. A phenomenological model referred to as the eSD model was developed earlier to describe the spectral diffusion process and thus reproduce the experimental results of electron depolarization. This model has recently been supported by quantum mechanical calculations on a small dipolar coupled electron spin system, experiencing dipolar interaction based cross-relaxation. In the present study, we performed a series of ELDOR measurements on a solid glassy solution of TEMPOL radicals in an effort to substantiate the eSD model and test its predictability in terms of electron depolarization profiles, in the steady-state and under non-equilibrium conditions. The crucial empirical parameter in this model is LeSD, which reflects the polarization exchange rate among the electron spins. Here, we explore further the physical basis of this parameter by analyzing the ELDOR spectra measured in the temperature range of 3–20 K and radical concentrations of 20–40 mM. Simulations using the eSD model were carried out to determine the dependence of LeSD on temperature and concentration. We found that for the samples studied, LeSD is temperature independent. It, however, increases with a power of B2.6 of the concentration of TEMPOL, which is proportional to the average electron–electron dipolar interaction strength in the sample.

PhDs & postdocs in MAS-DNP at CEA / Univ. Grenoble Alpes (France) Inbox x #DNPNMR

PhDs & postdocs in MAS-DNP at CEA / Univ. Grenoble Alpes (France)


Several positions (PhD / postdoc) will be available at CEA Grenoble / Univ. Grenoble Alpes in the field of solid-state NMR with Dynamic Nuclear Polarization, for a start within the next 6 months. Projects range from instrumentation and method developments to applications on biomolecules (cell walls, amyloid fibrils, protein-ligand interactions, etc.) and advanced materials (inorganic NCs, functional polymers, supercapacitors, etc.). Some of these projects involve collaborations with industrial partners.

In particular, we are currently welcoming applications for a PhD position aiming at developing the selective DNP (sel-DNP) approach, recently introduced in our group, which allows high-resolution studies of biomolecular binding sites. (see DOI 10.1039/C8SC05696J). Deadline for this application is April 15th.

More information about our group and a list of recent publications can be found here:http://www.dnpgrenoble.net/list-of-publications

Interested candidates are welcomed to send an email to: gael.depaepe@cea.fr.

Grenoble is one of the major cities in Europe for research with a large international scientific community. In addition, Grenoble has a large international student population, is a very pleasant city to live in, and is known as the “Capital of the Alps” with easy access to great skiing and hiking. It’s also only 2 hours’ drive to the Mediterranean Sea, Italy, or Switzerland. Grenoble, Lyon, and Geneva airports are nearby and permit straightforward international travel.

-- Dr Gaël De Paëpe -- DRF/INAC/MEM/RM INAC (CEA/Grenoble Alpes University) 17 Avenue des Martyrs Bâtiment 51C Office P.132a / Lab P.138 38054 Grenoble Cedex 9 - France email gael.depaepe@cea.fr voice (office) +33 4 38 78 65 70 voice (lab) +33 4 38 78 47 26 fax +33 4 38 78 50 90 

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Mar 19, 2019

DNP-enhanced NMR studies of cellular membrane disruption induced by Abeta40 peptides. #DNPNMR

DNP-enhanced NMR studies of cellular membrane disruption induced by Abeta40 peptides.

Supervisor: Dr Alexey Potapov

We are looking for a motivated PhD candidate interested in biophysical applications of magnetic resonance spectroscopy. This position is suitable for students with background in Physics, Chemistry or other related fields.

Aggregates of amyloid-beta peptides have been proposed to play role in causing Alzheimer's disease, however, their mechanism of action is not clearly understood. In this project, carried out in collaboration with SUNY Binghamton (USA), we focus on the process of cell membrane disruption by amyloid-beta and study its details using advanced nuclear magnetic resonance (NMR) techniques. One of such techniques is the dynamic nuclear polarization (DNP) allowing the NMR signals to be increased by a large factor. University of Nottingham is hosting a modern DNP-enhanced solid-state NMR Facility (unique in the UK) funded by a grant of £2.5 M from EPSRC.

The PhD studentship is available immediately, and is fully funded for 3.5 years via a stipend covering PhD tuition fees (at the UK/EU rate) and a tax-free living allowance.

The Sir Peter Mansfield Imaging Centre, which is part of the School of Physics and Astronomy of the University of Nottingham, is well equipped and conducts a very active research program in many aspects of modern magnetic resonance (http://www.nottingham.ac.uk/magres/index.aspx). For more details please contact Dr Alexey Potapov (alexey.potapov@nottingham.ac.uk)

Dr Alexey Potapov
Assistant Professor in Magnetic Resonance
Sir Peter Mansfield Imaging Center
School of Physics and Astronomy
University of Nottingham
Nottingham NG7 2RD United Kingdom
p: (44) 115 951 4739

This message and any attachment are intended solely for the addressee and may contain confidential information. If you have received this message in error, please contact the sender and delete the email and attachment. Any views or opinions expressed by the author of this email do not necessarily reflect the views of the University of Nottingham. Email communications with the University of Nottingham may be monitored where permitted by law. 

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PhD position in biomolecular solid-state NMR - Groningen, Netherlands


PhD position in Structural biology of Huntington’s disease using solid-state NMR

University of Groningen, Zernike Institute for Advanced Materials (Netherlands)
Van der Wel Solid-state NMR Group

We are looking to fill a PhD position for an exciting new project in our lab at the University of Groningen. This project is funded by a grant from the Netherlands’ Campagneteam Huntington – a community-driven effort to fund Huntington’s disease (HD) research in the Netherlands.

The researcher will use solid-state NMR and electron microscopy for molecular studies of the central protein misfolding event behind the neurodegenerative disease HD. Tailor-made solid-state NMR experiments will be used to provide an atomic view of the protein aggregates. For an integrated structure/toxic-function analysis, the project will include toxicity assays in human neuronal cells and aggregation modulation studies. The PhD researcher will perform the cellular assays with the group of Prof. Amalia Dolga, our close collaborator in the Groningen Research Institute of Pharmacy. The interdisciplinary studies are designed to yield a new understanding of this devastating disease, with likely implications for other neurodegenerative disorders associated with protein aggregation.

Recent HD research papers from the lab:
• Hoop et al. (2016) Huntingtin exon 1 fibrils feature an interdigitated β-hairpin–based polyglutamine core. PNAS 113(6):1546–51.

• Lin et al. (2017) Fibril polymorphism affects immobilized non-amyloid flanking domains of huntingtin exon1 rather than its polyglutamine core. Nat Commun. 8:15462.

• Smith et al. (2018) Structural fingerprinting of protein aggregates by dynamic nuclear polarization-enhanced solid-state NMR at natural isotopic abundance. J Am Chem Soc 140(44): 14576-14580.

The candidate is expected to have a Master’s degree (or potentially a BSc degree with demonstrable research experience*) in bio- or physical chemistry, (bio)physics or another field of science relevant for the position. Experience with NMR, and especially solid-state NMR, is an important consideration, but may not be essential (depending on the background of the candidate). Applicants with a background and interest in protein biophysics or protein aggregation are encouraged to apply.

For information or questions about the project, application procedure, and requirements, potential applicants should contact Dr Van der Wel at p.c.a.van.der.wel@rug.nl

Additional background information about the lab is also available on our website https://www.vanderwellab.org/


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Mar 18, 2019

Maximizing nuclear hyperpolarization in pulse cooling under MAS #DNPNMR

Björgvinsdóttir, Snædís, Brennan J. Walder, Nicolas Matthey, and Lyndon Emsley. “Maximizing Nuclear Hyperpolarization in Pulse Cooling under MAS.” Journal of Magnetic Resonance 300 (March 1, 2019): 142–48.


It has recently been shown how dynamic nuclear polarization can be used to hyperpolarize the bulk of proton-free solids. This is achieved by generating the polarization in a wetting phase, transferring it to nuclei near the surface and relaying it towards the bulk through homonuclear spin diffusion between weakly magnetic nuclei. Pulse cooling is a strategy to achieve this that uses a multiple contact cross-polarization sequence for bulk hyperpolarization. Here, we show how to maximize sensitivity using the pulse cooling method by experimentally optimizing pulse parameters and delays on a sample of powdered SnO2. To maximize sensitivity we introduce an approach where the magic angle spinning rate is modulated during the experiment: the CP contacts are carried out at a slow spin rate to benefit from faster spin diffusion, and the spin rate is then accelerated before detection to improve line narrowing. This method can improve the sensitivity of pulse cooling for 119Sn spectra of SnO2 by an additional factor of 3.5.

Mar 15, 2019

Time-optimized pulsed dynamic nuclear polarization #DNPNMR

Pulsed DNP experiments have been discussed in the literature for quite a while already. While several experiments have been proposed and conducted at low magnetic fields, where instrumentation is less demanding, this is the first example of pulsed DNP experiments performed at high magnetic fields.

Tan, Kong Ooi, Chen Yang, Ralph T Weber, Guinevere Mathies, and Robert G Griffin. “Time-Optimized Pulsed Dynamic Nuclear Polarization.” SCIENCE ADVANCES 5 (2019): 8. https://doi.org/10.1126/sciadv.aav6909

Pulsed dynamic nuclear polarization (DNP) techniques can accomplish electron-nuclear polarization transfer efficiently with an enhancement factor that is independent of the Zeeman field. However, they often require large Rabi frequencies and, therefore, high-power microwave irradiation. Here, we propose a new low-power DNP sequence for static samples that is composed of a train of microwave pulses of length τp spaced with delays d. A particularly robust DNP condition using a period τm = τp + d set to ~1.25 times the Larmor period τLarmor is investigated which is a time-optimized pulsed DNP sequence (TOP-DNP). At 0.35 T, we obtained an enhancement of ~200 using TOP-DNP compared to ~172 with nuclear spin orientation via electron spin locking (NOVEL), a commonly used pulsed DNP sequence, while using only ~7% microwave power required for NOVEL. Experimental data and simulations at higher fields suggest a field-independent enhancement factor, as predicted by the effective Hamiltonian.

Mar 14, 2019

Postdoc position in biomolecular solid-state NMR at Florida State University, Fl, USA


Postdoctoral Position

Structural Biology of Ribonucleoproteins using solid-state NMR

Silvers Laboratory, Florida State University, Tallahassee, Florida, USA

The Silvers lab at Florida State University has an opening for a postdoctoral position with experience in using solid-state NMR on peptides and proteins that is available immediately. The successful candidate will participate in projects combining a variety of biophysical methods including solid-state and solution NMR spectroscopy, cryoEM, and X-ray crystallography to investigate protein:RNA and protein:DNA interactions.

About the candidate:

This position requires a PhD in (bio)chemistry, (bio)physics, or a closely related field. Candidates should have a strong background in biomolecular solid-state NMR spectroscopy. Experience in other methods such as solution NMR spectroscopy, general biochemical and biophysical methods, recombinant production of proteins, as well as in vitro biosynthesis of DNA and RNA are of advantage. Furthermore, candidates should be interested in working in a highly interdisciplinary and collaborative environment.

About the location:

The position is located at the Department of Chemistry and Biochemistry at FSU with strong ties to the Institute of Molecular Biophysics and the National High Magnetic Field Laboratory. The Institute of Molecular Biophysics (IMB) is highly collaborative institute focused on structural biology research. The faculty at the IMB belongs to various departments and utilizes a plethora of structural biology tools including solid-state and solution NMR, X-ray crystallography, and cryo-EM, among others. The National High Magnetic Field Laboratory (NHMFL) is the largest and highest-powered magnet laboratory in the world. Every year, more than a thousand scientists from dozens of countries come to use our unique magnets with the support of highly experienced staff scientists and technicians. Several high-field magnets (600-900 MHz) equipped with solution state probes and solid-state probes spinning up to 110kHz are available.

About the position:

The position is initially for 1 year but can be extended to 2 years. Domestic and international candidates are encouraged to apply. Florida State University is an equal opportunity employer and educational provider committed to a policy of non-discrimination for any member of the University's community.

How to apply:

Apply online at https://jobs.fsu.edu. Go to “Browse Job Openings” and search for Job ID 44949 to apply. Please include a brief cover letter, a CV, and the contact information for three references. Applications will be considered until the position is filled. Any questions about the position should be directed at rsilvers@fsu.edu.

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Dr. Robert Silvers
Assistant Professor of Chemistry and Biochemistry
Institute of Molecular Biophysics
Department of Chemistry and Biochemistry
Florida State University

91 Chieftan Way
Tallahassee, FL 32306-4380

office phone: 850-645-9649

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