2021
December 2021
Tobias Hett, University of Bonn, DE
Spatiotemporal Resolution of Conformational Changes in Biomolecules by Pulsed Electron-Electron Double Resonance Spectroscopy
Proteins undergo ligand-induced conformational changes.; therefore to explain the conversion between states one has to resolve the space and time dimension. Here we combined Microsecond Freeze-Hyperquenching (MHQ) and PELDOR/DEER spectroscopy to monitor ligand-triggered conformational changes on the angstrom and microsecond time scale and subsequently validated the technique on the cyclic nucleotide-binding domain. It allows for snapshots along the trajectory of the conformational change by rapid freeze quenching within times of 80-700 µs, and it is applicable at protein amounts down to 7.5 nmol (75 µM, 100 µL) per time point.
Jasleen Bindra, NIST, USA
Probing the Dielectric Transition and Molecular Dynamics in the Metal–Organic Framework [(CH3)2NH2]Mg(HCOO)3 using Resonance Spectroscopic Tools
Metal–organic frameworks are constituted of two main building units: the framework consisting of metal centers connected to each other by organic linker molecules. The order–disorder phase transition is a common property in these materials. At higher temperatures in the disordered phase, the (CH3)2NH+cation that is trapped within the cage is disordered. At lower temperature, the long-range order is established due to the cooperative ordering of the cations. Subsequently the nitrogen atoms freeze into a single position in the cavity, while the metal-formate framework becomes more distorted. Here we use resonance spectroscopic tools like SSNMR and EPR to probe structural phase transition in these materials.
Josh Biller, TDA Research, USA
EPR and Corrosion
Understanding, measuring and mitigating corrosion, especially for high strength aluminum aerospace alloys, draws considerable interest and research funding since estimates of the impact of corrosion around the globe are about $2.5 trillion annually. Corrosion is an electrochemical reaction involving the transfer of electrons between a metal surface and aqueous electrolyte solution. Many commonly used aerospace aluminums are alloyed with metals which become EPR active cations as the corrosion reaction proceeds. Despite (1) the wt% loading of these metals during the alloy process, and (2) the tremendous sensitivity of EPR, the study of EPR active transition metal cations related to corrosion on aerospace aluminum is not commonplace. This presentation will lay out preliminary work done at TDA Research regarding the use of EPR as a tool for studying and characterizing corrosion.
November 2021
Alexandra Born, University of Colorado Anschutz Medical Campus, USA
Using DEER Distance Distributions to Cross-Validate Multi-State NMR Ensembles
In multi-domain proteins, intradomain structures and dynamics can influence interdomain conformations and vice versa. We describe a novel method to model the coupling between intra- and interdomain dynamics at atomic resolution using multi-state ensembles. The method uses time-averaged nuclear magnetic resonance restraints and double electron-electron resonance data that resolves distance distributions. We applied our method to describe the correlated conformations and the overall ensemble of the two-domain protein Pin1 that populates compact and extended states.
David Nyenhuis, National Institute of Health, USA
In vivo Approaches to Obtain CW and Pulsed EPR Measurements in the Outer Membrane of Escherichia Coli
Here, we have developed approaches for the spin labeling of OM proteins in intact Escherichia coli cells, including the use of a disulfide chaperone knockout strain to facilitate double labeling, from which we were able to obtain distance measurements on the OM surface using DEER. Using these approaches, we investigated the E. coli cobalamin transporter, BtuB, and have recently demonstrated the ability to detect its supramolecular organization on the cell surface. Additionally, distance measurements on BtuB in the intact cell revealed that both the conformation of the extracellular loops, and the presence of a substrate-dependent allosteric shift in the protein core, were dependent on the native environment.
October 2021
Annemarie Kehl, Max Planck Institute for Biophysical Chemistry, DE
19F-ENDOR: Distance Measurements and Resolution of Chemical Shift Anisotropy
Here we introduce an approach to measure molecular distances in biomacromolecules using 19F nuclear spins and nitroxide radicals in combination with high-frequency (94 GHz/3.4 T) electron–nuclear double resonance (ENDOR). The small size and large gyromagnetic ratio of the 19F label enable to access distances up to about 1.5 nm with an accuracy of 0.1–1 c. Performance is illustrated on synthesized fluorinated model compounds as well as spin labelled RNA duplexes. The results demonstrate access to a distance range crucial to elucidate active sites of nucleic acids or proteins in the solution state.
Michal Kern, University of Stuttgard, DE
Hybrid Spintronic Materials from Conducting polymers with Molecular Quantum Bits
Organic field-effect transistor measurements demonstrate that the favorable electrical properties are preserved in the presence of the qubits. Chemical doping introduces charge carriers into the material, and variable-temperature charge transport measurements reveal the existence of mobile charge carriers at temperatures as low as 15 K. Importantly, quantum coherence of the qubit is shown to be preserved up to temperatures of at least 30 K, that is, in the presence of mobile charge carriers. These results pave the way for employing such hybrid materials in novel molecular quantum spintronic architectures.
September 2021
Nandita Abhyankar, National Institute of Standards and Technology, USA
Scalable Microresonators for Room Temperature Detection of Electron Spin Resonance from Dilute, Sub-nanoliter Volume Solids
The design principles for microwave microresonators, which typically probe samples with volumes smaller than a nanoliter. I will explore application spaces for magnetic resonance spectroscopies of volume-limited samples, including sub-nanoliter-sized sample solutions, single crystals, and thin films. I will focus on planar inverse anapole microresonators, (1) delineating their particular advantages and limitations, and future work branching out from this idea, including present and potential future applications of these devices.
August 2021
Matthias Bretschneider, Goethe University Frankfurt, DE
Multiquantum Counting of Trityl radicals
DQC-EPR pulse sequence allows to select signals from ‘n’ dipolar coupled electron spins by appropriate phase cycling. For proof of concept, the pulse sequence was applied to a series of multi-trityl model compounds of which the MQ-filtered EPR experiments determined the number of coupled electron spins. This opens a leeway to explore the transversal relaxation times of higher quantum coherences. In conclusion, one can envision to apply this concept to biological and chemical processes which require oligomerization.
Lotem Buchbinder, Technion, IL
The Potential of Pulsed Electron Spin Resonance for Tooth-based Retrospective Biodosimetry
Yaron Artzi, Technion, IL
High-Temperature Superconducting Surface Micro-Resonators for High Sensitivity EPR
July 2021
Shreya Ghosh, National Institute of Health, USA
Site-specific Cu2+-based Spin Labeling Schemes for Obtaining Distance Constraints in Proteins and DNA
Cu2+-based EPR reporters for proteins and DNA are small, rigid, therefore can provide information on the backbone fluctuations without additional modeling. We have demonstrated a nucleotide and structure-independent Cu2+-based label for DNA to report on the backbone conformations in solution. For proteins, Cu2+ binds to two strategically placed histidine residues; the rigidity of the Cu2+-label shows promise over traditional labels to elucidate protein backbone flexibility, conformations and orientations of subunits. Overall, Cu2+-label for DNA and proteins has a great promise for structural biology.
March 2021
Marina Bennati, Max Planck Institute for Biophysical Chemistry, DE
ENDOR Spectroscopy: Tutorial and Latest Progress at High EPR Frequencies
January 2021
Mantas Simenas, University College London, UK
A Sensitivity Leap for X-band EPR Using a Probe Head with a Cryogenic Preamplifier