Magnetic resonance (Gottingen, Germany)最新文献

{"title":"Extended Bloch-McConnell equations for mechanistic analysis of hyperpolarized ¹³C magnetic resonance experiments on enzyme systems.","authors":"Thomas R Eykyn, Stuart J Elliott, Philip W Kuchel","doi":"10.5194/mr-2-421-2021","DOIUrl":"10.5194/mr-2-421-2021","url":null,"abstract":"<p><p>We describe an approach to formulating the kinetic master equations of the time evolution of NMR signals in reacting (bio)chemical systems. Special focus is given to studies that employ signal enhancement (hyperpolarization) methods such as dissolution dynamic nuclear polarization (dDNP) and involving nuclear spin-bearing solutes that undergo reactions mediated by enzymes and membrane transport proteins. We extend the work given in a recent presentation on this topic (Kuchel and Shishmarev, 2020) to now include enzymes with two or more substrates and various enzyme reaction mechanisms as classified by Cleland, with particular reference to non-first-order processes. Using this approach, we can address some pressing questions in the field from a theoretical standpoint. For example, why does binding of a hyperpolarized substrate to an enzyme <i>not</i> cause an appreciable loss of the signal from the substrate or product? Why does the concentration of an unlabelled pool of substrate, for example <math><msup><mi></mi><mn>12</mn></msup></math>C lactate, cause an increase in the rate of exchange of the <math><msup><mi></mi><mn>13</mn></msup></math>C-labelled pool? To what extent is the equilibrium position of the reaction perturbed during administration of the substrate? The formalism gives a full mechanistic understanding of the time courses derived and is of relevance to ongoing clinical trials using these techniques.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":"2 1","pages":"421-446"},"PeriodicalIF":0.0,"publicationDate":"2021-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10539799/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71415874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"¹²⁹Xe ultra-fast Z spectroscopy enables micromolar detection of biosensors on a 1 T benchtop spectrometer.","authors":"Kévin Chighine,&nbsp;Estelle Léonce,&nbsp;Céline Boutin,&nbsp;Hervé Desvaux,&nbsp;Patrick Berthault","doi":"10.5194/mr-2-409-2021","DOIUrl":"10.5194/mr-2-409-2021","url":null,"abstract":"<p><p>The availability of a benchtop nuclear magnetic resonance (NMR) spectrometer, of low cost and easily transportable, can allow detection of low quantities of biosensors, provided that hyperpolarized species are used. Here we show that the micromolar threshold can easily be reached by employing laser-polarized xenon and cage molecules reversibly hosting it. Indirect detection of caged xenon is made via chemical exchange, using ultra-fast Z spectroscopy based on spatio-temporal encoding. On this non-dedicated low-field spectrometer, several ideas are proposed to improve the signal.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":"2 1","pages":"409-420"},"PeriodicalIF":0.0,"publicationDate":"2021-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10539730/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71415867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hyperpolarization and the physical boundary of Liouville space.","authors":"Malcolm H Levitt,&nbsp;Christian Bengs","doi":"10.5194/mr-2-395-2021","DOIUrl":"10.5194/mr-2-395-2021","url":null,"abstract":"<p><p>The quantum state of a spin ensemble is described by a density operator, which corresponds to a point in the Liouville space of orthogonal spin operators. Valid density operators are confined to a particular region of Liouville space, which we call the physical region and which is bounded by multidimensional figures called simplexes. Each vertex of a simplex corresponds to a pure-state density operator. We provide examples for spins <math><mrow><mi>I</mi><mo>=</mo><mn>1</mn><mo>/</mo><mn>2</mn></mrow></math>, <math><mrow><mi>I</mi><mo>=</mo><mn>1</mn></mrow></math>, <math><mrow><mi>I</mi><mo>=</mo><mn>3</mn><mo>/</mo><mn>2</mn></mrow></math> and for coupled pairs of spins-1/2. We use the von Neumann entropy as a criterion for hyperpolarization. It is shown that the inhomogeneous master equation for spin dynamics leads to non-physical results in some cases, a problem that may be avoided by using the Lindbladian master equation.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":" ","pages":"395-407"},"PeriodicalIF":0.0,"publicationDate":"2021-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10539761/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41620009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A novel sample handling system for dissolution dynamic nuclear polarization experiments.","authors":"Thomas Kress, Kateryna Che, Ludovica M Epasto, Fanny Kozak, Mattia Negroni, Gregory L Olsen, Albina Selimovic, Dennis Kurzbach","doi":"10.5194/mr-2-387-2021","DOIUrl":"10.5194/mr-2-387-2021","url":null,"abstract":"<p><p>We present a system for facilitated sample vitrification, melting, and transfer in dissolution dynamic nuclear polarization (DDNP) experiments. In DDNP, a sample is typically hyperpolarized at cryogenic temperatures before dissolution with hot solvent and transfer to a nuclear magnetic resonance (NMR) spectrometer for detection in the liquid state. The resulting signal enhancements can exceed 4 orders of magnitude. However, the sudden temperature jump from cryogenic temperatures close to 1 K to ambient conditions imposes a particular challenge. It is necessary to rapidly melt the sample to avoid a prohibitively fast decay of hyperpolarization. Here, we demonstrate a sample dissolution method that facilitates the temperature jump by eliminating the need to open the cryostat used to cool the sample. This is achieved by inserting the sample through an airlock in combination with a dedicated dissolution system that is inserted through the same airlock shortly before the melting event. The advantages are threefold: (1) the cryostat can be operated continuously at low temperatures. (2) The melting process is rapid as no pressurization steps of the cryostat are required. (3) Blockages of the dissolution system due to freezing of solvents during melting and transfer are minimized.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":"2 1","pages":"387-394"},"PeriodicalIF":0.0,"publicationDate":"2021-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10539747/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71415868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Small-molecule inhibitors of the PDZ domain of Dishevelled proteins interrupt Wnt signalling.","authors":"Nestor Kamdem,&nbsp;Yvette Roske,&nbsp;Dmytro Kovalskyy,&nbsp;Maxim O Platonov,&nbsp;Oleksii Balinskyi,&nbsp;Annika Kreuchwig,&nbsp;Jörn Saupe,&nbsp;Liang Fang,&nbsp;Anne Diehl,&nbsp;Peter Schmieder,&nbsp;Gerd Krause,&nbsp;Jörg Rademann,&nbsp;Udo Heinemann,&nbsp;Walter Birchmeier,&nbsp;Hartmut Oschkinat","doi":"10.5194/mr-2-355-2021","DOIUrl":"10.5194/mr-2-355-2021","url":null,"abstract":"<p><p>Dishevelled (Dvl) proteins are important regulators of the Wnt signalling pathway, interacting through their PDZ domains with the Wnt receptor Frizzled. Blocking the Dvl PDZ-Frizzled interaction represents a potential approach for cancer treatment, which stimulated the identification of small-molecule inhibitors, among them the anti-inflammatory drug Sulindac and Ky-02327. Aiming to develop tighter binding compounds without side effects, we investigated structure-activity relationships of sulfonamides. X-ray crystallography showed high complementarity of anthranilic acid derivatives in the GLGF loop cavity and space for ligand growth towards the PDZ surface. Our best binding compound inhibits Wnt signalling in a dose-dependent manner as demonstrated by TOP-GFP assays (IC<math><mrow><msub><mi></mi><mn>50</mn></msub><mo>∼</mo><mn>50</mn></mrow></math> <math><mrow><mi>µ</mi><mi>M</mi></mrow></math>) and Western blotting of <math><mi>β</mi></math>-catenin levels. Real-time PCR showed reduction in the expression of Wnt-specific genes. Our compound interacted with Dvl-1 PDZ (K<math><mrow><msub><mi></mi><mi>D</mi></msub><mo>=</mo><mn>2.4</mn></mrow></math> <math><mrow><mi>µ</mi><mi>M</mi></mrow></math>) stronger than Ky-02327 and may be developed into a lead compound interfering with the Wnt pathway.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":"2 1","pages":"355-374"},"PeriodicalIF":0.0,"publicationDate":"2021-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10539800/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71415887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Heteronuclear and homonuclear radio-frequency-driven recoupling.","authors":"Evgeny Nimerovsky,&nbsp;Kai Xue,&nbsp;Kumar Tekwani Movellan,&nbsp;Loren B Andreas","doi":"10.5194/mr-2-343-2021","DOIUrl":"10.5194/mr-2-343-2021","url":null,"abstract":"<p><p>The radio-frequency-driven recoupling (RFDR) pulse sequence is used in magic-angle spinning (MAS) NMR to recouple homonuclear dipolar interactions. Here we show simultaneous recoupling of both the heteronuclear and homonuclear dipolar interactions by applying RFDR pulses on two channels. We demonstrate the method, called HETeronuclear RFDR (HET-RFDR), on microcrystalline SH3 samples at 10 and 55.555 kHz MAS. Numerical simulations of both HET-RFDR and standard RFDR sequences allow for better understanding of the influence of offsets and paths of magnetization transfers for both HET-RFDR and RFDR experiments, as well as the crucial role of XY phase cycling.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":"2 1","pages":"343-353"},"PeriodicalIF":0.0,"publicationDate":"2021-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10539778/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71415876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Determination of hydrogen exchange and relaxation parameters in PHIP complexes at micromolar concentrations.","authors":"Lisanne Sellies, Ruud L E G Aspers, Marco Tessari","doi":"10.5194/mr-2-331-2021","DOIUrl":"10.5194/mr-2-331-2021","url":null,"abstract":"<p><p>Non-hydrogenative para-hydrogen-induced polarization (PHIP) is a fast, efficient and relatively inexpensive approach to enhance nuclear magnetic resonance (NMR) signals of small molecules in solution. The efficiency of this technique depends on the interplay of NMR relaxation and kinetic processes, which, at high concentrations, can be characterized by selective inversion experiments. However, in the case of dilute solutions this approach is clearly not viable. Here, we present alternative PHIP-based NMR experiments to determine hydrogen and hydride relaxation parameters as well as the rate constants for para-hydrogen association with and dissociation from asymmetric PHIP complexes at micromolar concentrations. Access to these parameters is necessary to understand and improve the PHIP enhancements of (dilute) substrates present in, for instance, biofluids and natural extracts.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":"2 1","pages":"331-340"},"PeriodicalIF":0.0,"publicationDate":"2021-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10539837/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71415871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Real-time nuclear magnetic resonance spectroscopy in the study of biomolecular kinetics and dynamics.","authors":"György Pintér,&nbsp;Katharina F Hohmann,&nbsp;J Tassilo Grün,&nbsp;Julia Wirmer-Bartoschek,&nbsp;Clemens Glaubitz,&nbsp;Boris Fürtig,&nbsp;Harald Schwalbe","doi":"10.5194/mr-2-291-2021","DOIUrl":"10.5194/mr-2-291-2021","url":null,"abstract":"<p><p>The review describes the application of nuclear magnetic resonance (NMR) spectroscopy to study kinetics of folding, refolding and aggregation of proteins, RNA and DNA. Time-resolved NMR experiments can be conducted in a reversible or an irreversible manner. In particular, irreversible folding experiments pose large requirements for (i) signal-to-noise due to the time limitations and (ii) synchronising of the refolding steps. Thus, this contribution discusses the application of methods for signal-to-noise increases, including dynamic nuclear polarisation, hyperpolarisation and photo-CIDNP for the study of time-resolved NMR studies. Further, methods are reviewed ranging from pressure and temperature jump, light induction to rapid mixing to induce rapidly non-equilibrium conditions required to initiate folding.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":"2 1","pages":"291-320"},"PeriodicalIF":0.0,"publicationDate":"2021-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10539803/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71415883","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Non-classical disproportionation revealed by photo-chemically induced dynamic nuclear polarization NMR.","authors":"Jakob Wörner, Jing Chen, Adelbert Bacher, Stefan Weber","doi":"10.5194/mr-2-281-2021","DOIUrl":"10.5194/mr-2-281-2021","url":null,"abstract":"<p><p>Photo-chemically induced dynamic nuclear polarization (photo-CIDNP) was used to observe the light-induced disproportionation reaction of 6,7,8-trimethyllumazine starting out from its triplet state to generate a pair of radicals comprising a one-electron reduced and a one-electron oxidized species. Our evidence is based on the measurement of two marker proton hyperfine couplings, <math><mrow><msub><mi>A</mi><mi>iso</mi></msub></mrow></math>(H(6<math><mi>α</mi></math>)) and <math><mrow><msub><mi>A</mi><mi>iso</mi></msub></mrow></math>(H(8<math><mi>α</mi></math>)), which we correlated to predictions from density functional theory. The ratio of these two hyperfine couplings is reversed in the oxidized and the reduced radical species. Observation of the dismutation reaction is facilitated by the exceptional C-H acidity of the methyl group at position 7 of 6,7,8-trimethyllumazine and the slow proton exchange associated with it, which leads to NMR-distinguishable anionic (TML<math><msup><mi></mi><mo>-</mo></msup></math>) and neutral (TMLH) protonation forms.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":"2 1","pages":"281-290"},"PeriodicalIF":0.0,"publicationDate":"2021-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10539781/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71415879","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An electrochemical cell for in operando ¹³C nuclear magnetic resonance investigations of carbon dioxide/carbonate processes in aqueous solution.","authors":"Sven Jovanovic,&nbsp;P Philipp M Schleker,&nbsp;Matthias Streun,&nbsp;Steffen Merz,&nbsp;Peter Jakes,&nbsp;Michael Schatz,&nbsp;Rüdiger-A Eichel,&nbsp;Josef Granwehr","doi":"10.5194/mr-2-265-2021","DOIUrl":"10.5194/mr-2-265-2021","url":null,"abstract":"<p><p>In operando nuclear magnetic resonance (NMR) spectroscopy is one method for the online investigation of electrochemical systems and reactions. It allows for real-time observations of the formation of products and intermediates, and it grants insights into the interactions of substrates and catalysts. An in operando NMR setup for the investigation of the electrolytic reduction of <math><mrow><msub><mi>CO</mi><mn>2</mn></msub></mrow></math> at silver electrodes has been developed. The electrolysis cell consists of a three-electrode setup using a working electrode of pristine silver, a chlorinated silver wire as the reference electrode, and a graphite counter electrode. The setup can be adjusted for the use of different electrode materials and fits inside a 5 mm NMR tube. Additionally, a shielding setup was employed to minimize noise caused by interference of external radio frequency (RF) waves with the conductive components of the setup. The electrochemical performance of the in operando electrolysis setup is compared with a standard <math><mrow><msub><mi>CO</mi><mn>2</mn></msub></mrow></math> electrolysis cell. The small cell geometry impedes the release of gaseous products, and thus it is primarily suited for current densities below 1 mA cm<math><msup><mi></mi><mrow><mo>-</mo><mn>2</mn></mrow></msup></math>. The effect of conductive components on <math><msup><mi></mi><mn>13</mn></msup></math>C NMR experiments was studied using a <math><mrow><msub><mi>CO</mi><mn>2</mn></msub></mrow></math>-saturated solution of aqueous bicarbonate electrolyte. Despite the <math><mrow><msub><mi>B</mi><mn>0</mn></msub></mrow></math> field distortions caused by the electrodes, a proper shimming could be attained, and line widths of ca. 1 Hz were achieved. This enables investigations in the sub-Hertz range by NMR spectroscopy. High-resolution <math><msup><mi></mi><mn>13</mn></msup></math>C NMR and relaxation time measurements proved to be sensitive to changes in the sample. It was found that the dynamics of the bicarbonate electrolyte varies not only due to interactions with the silver electrode, which leads to the formation of an electrical double layer and catalyzes the exchange reaction between <math><mrow><msub><mi>CO</mi><mn>2</mn></msub></mrow></math> and <math><mrow><msubsup><mi>HCO</mi><mn>3</mn><mo>-</mo></msubsup></mrow></math>, but also due to interactions with the electrochemical setup. This highlights the necessity of a step-by-step experiment design for a mechanistic understanding of processes occurring during electrochemical <math><mrow><msub><mi>CO</mi><mn>2</mn></msub></mrow></math> reduction.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":"2 1","pages":"265-280"},"PeriodicalIF":0.0,"publicationDate":"2021-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10539767/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71415869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}