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    “Parahydrogen Enhanced Magnetic Resonance - a tale of spin physics, materials and catalysis”

    Date:
    15
    Thursday
    June
    2023
    Lecture / Seminar
    Time: 00:00
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr. Stefan Glogger
    Organizer: Clore Institute for High-Field Magnetic Resonance Imaging and Spectroscopy
    Contact: ana.naamat@weizmann.ac.il
    Abstract: Catalysts are essential in increasing reaction rates of chemical reactions. Th ... Read more Catalysts are essential in increasing reaction rates of chemical reactions. They have not only shaped our modern world but are also used by nature in many biochemical reactions. Understanding catalytic mechanisms and developing new catalysts holds promise to e.g. solve energy challenges of our society. Before this background, I am developing new methodologies based on magnetic resonance to unravel processes in catalysis and work towards nano-materials in which nuclear spin states can be controlled during reactions. Thereby, I am making use of the technique of parahydrogen induced polarization, which is an enhancement technology in NMR, boosting signals by four orders of magnitude. This approach uses parahydrogen, a spin isomer of normal hydrogen gas that interacts with a catalyst and undergoes a chemical reaction. During this process, the spin order of parahydrogen is converted into largely enhanced magnetic resonance signals and acts as a spy molecule for the catalytic process. In recent years my group has pioneered the use of parahydrogen to study metalloenzymes and more in specific hydrogenases. Hydrogenases are considered nature's blueprint for efficient hydrogen activation catalysts. Although they represent an important class of enzymes, the catalytic mechanisms leading to hydrogen activation are not fully understood. My developed tools allowed for new insights that no other analytical technology could provide and thereby refined details of the catalytic mechanisms. Additionally, my group has been researching the development of nano-catalysts that can allow for maintaining the para-hydrogen spin order on surfaces. This promises on one side to develop new enhancement strategies in particular to boost the signal of mobile protons that can e.g. exchange with proteins or small molecules leading to their further enhancements in solution. On the other side, a precise control of nuclear spin states during chemical reactions in solution can allow for the future production of large quantities of spin-controlled chemicals such as para-water or formaldehyde in the para-state. These are chemicals found in e.g. interstellar clouds showing different ratios between ortho (triplet) and para (singlet) states as compared to earth and are thought to display different reactivities. Understanding the effect of nuclear spin states on reactions could lead to new application in chemical reactions and catalysis in the future.
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    Non-invasive Methods for Extracting Microstructural Information from Human Tissues: Implementation in a Clinical MRI Scanner

    Date:
    18
    Thursday
    May
    2023
    Lecture / Seminar
    Time: 09:30-10:30
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr Analía Zwick
    Organizer: Clore Institute for High-Field Magnetic Resonance Imaging and Spectroscopy
    Contact: ana.naamat@weizmann.ac.il
    Abstract: Extracting quantitative information about tissue microstructure using non-invasi ... Read more Extracting quantitative information about tissue microstructure using non-invasive methods is an exceptional challenge in understanding disease mechanisms and enabling early diagnosis of pathologies. Magnetic Resonance Imaging (MRI) is a promising and widely used technique to achieve this goal, but it still provides low resolution to reveal details of the microstructure. Recently, we have developed methods to produce images with quantitative information about the microstructure based on selective probing of spin dephasing induced by molecular diffusion restriction in cavities of the tissue microstructure [1-3]. The feasibility of the theoretical method has been demonstrated so far by first-principles experiments and simulations on typical size distributions of white matter in the mouse brain [3]. As a next step towards practical implementation, we have implemented this method in clinical scanners [4]. In this work, I present the challenges and preliminary results of this implementation in both phantoms and human volunteers. These results open up a new avenue for MRI to advance in extracting quantitative, and fast microstructural information from images. [1] A. Zwick, D. Sueter, G. Kurizki, G. A. Álvarez, Phys. Rev. Applied 14, 024088, (2020). [2] M. Capiglioni, A. Zwick, P. Jiménez, G. A. Álvarez. Proc. Intl. Soc. Mag. Reson. Med. 29, 2036 (2021) [3] M. Capiglioni, A. Zwick, P. Jiménez and G. A. Álvarez, Phys. Rev. Applied 15, 014045 (2021). [4] E. Saidman, A. Zwick, S. Tambalo, T. Feiweier, J. Jovicich, G. A. Álvarez. Proc. Intl. Soc. Mag. Reson. Med. (2023)
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    3D quantitative-amplified Magnetic Resonance Imaging (3D q-aMRI)

    Date:
    02
    Sunday
    April
    2023
    Lecture / Seminar
    Time: 16:30-17:30
    Location: Perlman Chemical Sciences Building
    Lecturer: Itamar Terem
    Organizer: Clore Institute for High-Field Magnetic Resonance Imaging and Spectroscopy
    Contact: ana.naamat@weizmann.ac.il
    Abstract: Changes in blood vessel pulsation and cerebrospinal fluid dynamics cause cyclic ... Read more Changes in blood vessel pulsation and cerebrospinal fluid dynamics cause cyclic deformation of the brain, which can be altered by neurological pathologies. Various MRI techniques are available to visualize and quantify pulsatile brain motion, but they have limitations. Amplified MRI (aMRI) is a promising new technique that can visualize pulsatile brain tissue motion by amplifying sub-voxel motion in cine MRI data, but it lacks the ability to quantify the sub-voxel motion field in physical units. Here a novel 3D quantitative aMRI (3D q-aMRI) post-processing algorithm is introduced that can visualize and quantify pulsatile brain motion. To validate the algorithm, we tested it on a 3D digital phantom and on healthy volunteers. We also acquired preliminary data on participants with Alzheimer's disease and healthy aging controls. The results show that 3D q-aMRI can accurately quantify sub-voxel motion (of 0.005 pixel size) and has potential diagnostic value in identifying disease-induced biomechanical differences.
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    Biological Magnetic Resonance - From molecules to patients

    Date:
    26
    Sunday
    March
    2023
    -
    27
    Monday
    March
    2023
    Conference
    Time: 08:00
    Location: The David Lopatie Conference Centre
    Organizer: Clore Institute for High-Field Magnetic Resonance Imaging and Spectroscopy
    Contact: lucio.frydman@weizmann.ac.il
    Biological Magnetic Resonance - From molecules to patients Conference website

    Spatiotemporal Resolution of Conformational Changes in Biomolecules by Pulsed Electron-Electron Double Resonance Spectroscopy

    Date:
    09
    Thursday
    March
    2023
    Lecture / Seminar
    Time: 09:30-10:30
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr. Tobias Hett
    Organizer: Clore Institute for High-Field Magnetic Resonance Imaging and Spectroscopy
    Contact: ana.naamat@weizmann.ac.il
    Abstract: Proteins are highly dynamic biomolecules that can undergo ligand-induced confor ... Read more Proteins are highly dynamic biomolecules that can undergo ligand-induced conformational changes, thus often playing a crucial role in biomolecular processes. For an in-depth understanding of protein function, the conversion of one conformational state into another has to be resolved over space and time. Pulsed electron-electron double resonance spectroscopy (PELDOR/DEER) in combination with site-directed spin labelling (SDSL) is a powerful tool for obtaining distributions of interspin distances in proteins [1, 2]. It allows for measurements with Angstrom precision, but it cannot directly determine the time scale and the mechanism of the conformational change. However, coupling PELDOR with rapid freeze-quench techniques adds the time axis to the distance distribution and thus permits studying conformational changes with temporal resolution. Here, we show that the combination of Microsecond Freeze-Hyperquenching (MHQ) [3] and PELDOR resolves ligand-triggered conformational changes in proteins on the Angstrom length and microsecond time scale. It allows taking snapshots along the trajectory of the conformational change by rapid quenching within aging times of 82-668 μs, and it is applicable at protein amounts down to 7.5 nmol (75 μM, 100 μL) per time point. We applied MHQ/PELDOR to the cyclic nucleotide-binding domain (CNBD) of the MloK1 channel from Mesorhizobium loti, which undergoes a conformational change upon binding of cyclic adenosine monophosphate (cAMP). We observed a gradual population shift from the apo to the holo state on the microsecond time scale, but no distinct conformational intermediates (Fig. 1a, b). [4] Figure 1: a) Interspin distance distributions obtained at different aging times and b) the corresponding fractions of apo and holo state. c) Free-energy profile of the ligand-induced conformational change. Corroborated by measurements of ligand-binding kinetics and molecular dynamics (MD) simulations, we interpret the data in terms of a dwell time distribution. The transitions across the free-energy barriers (Fig. 1c) i.e., ligand binding and the conformational change, are on the nanosecond time scale and thus below the time resolution of the MHQ device. However, the dwell time of the apo state in complex with the cAMP ligand is in the microsecond range and can be monitored by MHQ/PELDOR. [4] Literature: [1] A.D. Milov et al., Fiz. Tverd. Tela 1981, 23, 975-982. [2] G. Jeschke, Annu. Rev. Phys. Chem. 2012, 63, 419-446. [3] A.V. Cherepanov et al., Biochim. Biophys. Acta 2004, 1656, 1-31. [4] T. Hett et al., J. Am. Chem. Soc. 2021, 143, 6981-6989.
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    Reverse-engineering deep neural networks

    Date:
    19
    Thursday
    January
    2023
    Lecture / Seminar
    Time: 09:30-10:30
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof. Ilya Kuprov
    Organizer: Clore Institute for High-Field Magnetic Resonance Imaging and Spectroscopy
    Contact: ananaamat@gmail.com
    Abstract: The lack of interpretability is a much-criticised feature of deep neural network ... Read more The lack of interpretability is a much-criticised feature of deep neural networks. Often, a neural network is effectively a black box. However, we have recently found a group-theoretical procedure that brings inner layer signalling into a human-readable form. We applied it to a signal processing network used in magnetic resonance spectroscopy, and found that the network spontaneously invents a bandpass filter, a notch filter, a frequency axis rescaling transformation, frequency division multiplexing, group embedding, spectral filtering regularisation, and a map from harmonic functions into Chebyshev polynomials – in ten minutes of unattended training.
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    “Functional MRI Advances at the Nexus of Acquisition, Processing, and Neuroscience”

    Date:
    12
    Thursday
    January
    2023
    Lecture / Seminar
    Time: 09:30-10:30
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Peter Bandettini
    Organizer: Clore Institute for High-Field Magnetic Resonance Imaging and Spectroscopy
    Contact: ana.naamat@weizmann.ac.il
    Abstract: MRI is truly unique in that contrast and acquisition can be manipulated to highl ... Read more MRI is truly unique in that contrast and acquisition can be manipulated to highlight a many tissues and physiologic processes at a wide range of speeds and resolutions. In the early 90’s, echo-planar imaging (EPI), a rapid imaging method that required specialized hardware, enabled time series acquisition of images - each collected in tens of milliseconds. Susceptibility contrast weighting sensitized the images to subtle shifts in blood oxygenation, allowing localized brain activation changes in oxygenation to be observed in near real time, thus introducing fMRI to the world. Since this breakthrough, fMRI has continued to advance in sophistication and impact. Higher fields, higher performance gradients, and novel pulse sequences and contrasts have allowed ever more subtle effects to be observed at higher fidelity, speed, and resolution. The signal became more informative as brain activation paradigms and processing methods advanced in conjunction with our deeper understanding of artifact and signal. Importantly, our insight into brain structure and function motivated and informed the experiments and, likewise, was enriched by the results. In this talk, I’ll trace the progress in fMRI, showing how the creative tension between advances in technology, processing, and our understanding of brain activation dynamics and physiology generated many of the innovations. My talk will include retinotopy, event-related fMRI, multi-echo EPI, resting state fMRI, connectivity, representational similarity analysis, decoding, naturalistic stimuli, inter-subject correlation, high field, and layer fMRI. Lastly, I’ll describe some of the technical and practical challenges facing the field today.
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