Magnetic resonance (Gottingen, Germany)最新文献

{"title":"Solid-State 1H Spin Polarimetry by 13CH3 Nuclear Magnetic Resonance","authors":"S. Elliott, Quentin Stern, S. Jannin","doi":"10.5194/MR-2-643-2021","DOIUrl":"https://doi.org/10.5194/MR-2-643-2021","url":null,"abstract":"Abstract. Dissolution-dynamic nuclear polarization is emerging as a promising means to prepare proton polarizations approaching unity. At present, 1H polarization quantification remains fastidious due to the requirement of measuring thermal equilibrium signals. Lineshape polarimetry of solid-state nuclear magnetic resonance spectra is used to determine a number of useful properties regarding the spin system under investigation. In the case of highly polarized nuclear spins, such as those prepared under the conditions of dissolution-dynamic nuclear polarization experiments, the absolute polarization of a particular isotopic species within the sample can be directly inferred from the characteristics of the corresponding resonance lineshape. In situations where direct measurements of polarization are complicated by deleterious phenomena, indirect estimates of polarization using coupled heteronuclear spins prove informative. We present a simple analysis of the 13C spectral lineshape asymmetry of [2-13C]sodium acetate based on relative peak intensities, which can be used to indirectly evaluate the proton polarization of the methyl group moiety, and very likely the entire sample in the case of rapid and homogeneous 1H-1H spin diffusion. 1H polarizations greater than ~10–25 % (depending on the sign of the microwave irradiation) were found to be linearly proportional to the 13C peak asymmetry, which responds differently to positive or negative microwave irradiation. These results suggest that, as a dopant, [2-13C]sodium acetate could be used to indirectly gauge 1H polarizations in standard sample formulations, which is potentially advantageous for: samples polarized in commercial dissolution-dynamic nuclear polarization devices that lack 1H radiofrequency hardware, measurements which are deleteriously influenced by radiation damping or complicated by the presence of large background signals, and situations where the acquisition of a thermal equilibrium spectrum is not feasible.\u0000","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45978324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-affinity tamoxifen analogues retain extensive positional disorder when bound to calmodulin.","authors":"Lilia Milanesi, Clare R Trevitt, Brian Whitehead, Andrea M Hounslow, Salvador Tomas, Laszlo L P Hosszu, Christopher A Hunter, Jonathan P Waltho","doi":"10.5194/mr-2-629-2021","DOIUrl":"10.5194/mr-2-629-2021","url":null,"abstract":"<p><p>Using a combination of NMR and fluorescence measurements, we have investigated the structure and dynamics of the complexes formed between calcium-loaded calmodulin (CaM) and the potent breast cancer inhibitor idoxifene, a derivative of tamoxifen. High-affinity binding (<math><mrow><msub><mi>K</mi><mi>d</mi></msub><mo>∼</mo><mn>300</mn></mrow></math> nM) saturates with a <math><mrow><mn>2</mn><mo>:</mo><mn>1</mn></mrow></math> <math><mrow><mi>idoxifene</mi><mo>:</mo><mi>CaM</mi></mrow></math> complex. The complex is an ensemble where each idoxifene molecule is predominantly in the vicinity of one of the two hydrophobic patches of CaM but, in contrast with the lower-affinity antagonists TFP, J-8, and W-7, does not substantially occupy the hydrophobic pocket. At least four idoxifene orientations per domain of CaM are necessary to satisfy the intermolecular nuclear Overhauser effect (NOE) restraints, and this requires that the idoxifene molecules switch rapidly between positions. The CaM molecule is predominantly in the form where the N and C-terminal domains are in close proximity, allowing for the idoxifene molecules to contact both domains simultaneously. Hence, the <math><mrow><mn>2</mn><mo>:</mo><mn>1</mn></mrow></math> <math><mrow><mi>idoxifene</mi><mo>:</mo><mi>CaM</mi></mrow></math> complex illustrates how high-affinity binding occurs without the loss of extensive positional dynamics.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":" ","pages":"629-642"},"PeriodicalIF":0.0,"publicationDate":"2021-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10539762/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46300637","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":"NUScon: A community-driven platform for quantitative evaluation of nonuniform sampling in NMR","authors":"Y. Pustovalova, F. Delaglio, D. L. Craft, H. Arthanari, A. Bax, M. Billeter, M. Bostock, Hesam T. Dashti, D. Hansen, S. Hyberts, Bruce A. Johnson, K. Kazimierczuk, Hengfa Lu, M. Maciejewski, Tomas Miljenović, M. Mobli, D. Nietlispach, V. Orekhov, R. Powers, X. Qu, S. Robson, D. Rovnyak, G. Wagner, Jinfa Ying, Matthew A. Zambrello, J. Hoch, D. Donoho, A. Schuyler","doi":"10.5194/mr-2021-59","DOIUrl":"https://doi.org/10.5194/mr-2021-59","url":null,"abstract":"Abstract. Although the concepts of non-uniform sampling (NUS) and non-Fourier spectral reconstruction in multidimensional NMR began to emerge four decades ago (Bodenhausen and Ernst, 1981; Barna and Laue, 1987), it is only relatively recently that NUS has become more commonplace. Advantages of NUS include the ability to tailor experiments to reduce data collection time and to improve spectral quality, whether through detection of closely spaced peaks (i.e., “resolution”) or peaks of weak intensity (i.e., “sensitivity”). Wider adoption of these methods is the result of improvements in computational performance, a growing abundance and flexibility of software, support from NMR spectrometer vendors, and the increased data sampling demands imposed by higher magnetic fields. However, the identification of best practices still remains a significant and unmet challenge. Unlike the discrete Fourier transform, non-Fourier methods used to reconstruct spectra from NUS data are nonlinear, depend on the complexity and nature of the signals, and lack quantitative or formal theory describing their performance. Seemingly subtle algorithmic differences may lead to significant variabilities in spectral qualities and artifacts. A community-based critical assessment of NUS challenge problems has been initiated, called the “Nonuniform Sampling Contest” (NUScon), with the objective to determine best practices for processing and analyzing NUS experiments. We address this objective by constructing challenges from NMR experiments that we inject with synthetic signals and we process these challenges using workflows submitted by the community. In the initial rounds of NUScon our aim is to establish objective criteria for evaluating the quality of spectral reconstructions. We present here a software package for performing the quantitative analyses and we present the results from the first two rounds of NUScon. We discuss the challenges that remain and present a road-map for continued community-driven development with the ultimate aim to provide best practices in this rapidly evolving field. The NUScon software package and all data from evaluating the challenge problems are hosted on the NMRbox platform.\u0000","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49473898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetostatic reciprocity for MR magnet design.","authors":"Pedro Freire Silva,&nbsp;Mazin Jouda,&nbsp;Jan G Korvink","doi":"10.5194/mr-2-607-2021","DOIUrl":"10.5194/mr-2-607-2021","url":null,"abstract":"<p><p>Electromagnetic reciprocity has long been a staple in magnetic resonance (MR) radio-frequency development, offering geometrical insights and a figure of merit for various resonator designs. In a similar manner, we use magnetostatic reciprocity to compute manufacturable solutions of complex magnet geometries, by establishing a quantitative metric for the placement and subsequent orientation of discrete pieces of permanent magnetic material. Based on magnetostatic theory and non-linear finite element modelling (FEM) simulations, it is shown how assembled permanent magnet setups perform in the embodiment of a variety of designs and how magnetostatic reciprocity is leveraged in the presence of difficulties associated with self-interactions, to fulfil various design objectives, including self-assembled micro-magnets, adjustable magnetic arrays, and an unbounded magnetic field intensity in a small volume, despite realistic saturation field strengths.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":" ","pages":"607-617"},"PeriodicalIF":0.0,"publicationDate":"2021-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10539805/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47274775","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":"Efficient polynomial analysis of magic-angle spinning sidebands and application to order parameter determination in anisotropic samples.","authors":"Günter Hempel,&nbsp;Paul Sotta,&nbsp;Didier R Long,&nbsp;Kay Saalwächter","doi":"10.5194/mr-2-589-2021","DOIUrl":"10.5194/mr-2-589-2021","url":null,"abstract":"<p><p>Chemical shift tensors in <math><msup><mi></mi><mn>13</mn></msup></math>C solid-state NMR provide valuable localized information on the chemical bonding environment in organic matter, and deviations from isotropic static-limit powder line shapes sensitively encode dynamic-averaging or orientation effects. Studies in <math><msup><mi></mi><mn>13</mn></msup></math>C natural abundance require magic-angle spinning (MAS), where the analysis must thus focus on spinning sidebands. We propose an alternative fitting procedure for spinning sidebands based upon a polynomial expansion that is more efficient than the common numerical solution of the powder average. The approach plays out its advantages in the determination of CST (chemical-shift tensor) principal values from spinning-sideband intensities and order parameters in non-isotropic samples, which is here illustrated with the example of stretched glassy polycarbonate.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":" ","pages":"589-606"},"PeriodicalIF":0.0,"publicationDate":"2021-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10539843/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45855535","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":"Selective excitation enables encoding and measurement of multiple diffusion parameters in a single experiment","authors":"Neil MacKinnon, Mehrdad Alinaghian, Pedro Silva, Thomas Gloge, B. Luy, M. Jouda, J. Korvink","doi":"10.5194/MR-2021-56","DOIUrl":"https://doi.org/10.5194/MR-2021-56","url":null,"abstract":"Abstract. Band selectivity to address specific resonances in a spectrum enables one to encode individual settings for diffusion experiments. In a single experiment, this could include different gradient strengths (enabling coverage of a larger range of diffusion constants), different diffusion delays, or different gradient directions (enabling anisotropic diffusion measurement). In this report a selective variant of the bipolar pulsed gradient, eddy-current delay (BPP-LED) experiment enabling selective encoding of three resonances was implemented. As proof-of-principle, the diffusion encoding gradient amplitude was assigned a range dependent on the selected signal, thereby allowing the extraction of the diffusion coefficient for water and a tripeptide (Met-Ala-Ser) with optimal settings in a single experiment.\u0000","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48220831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fluorine NMR study of proline-rich sequences using fluoroprolines","authors":"Davy Sinnaeve, Abir Ben Bouzayene, Emile Ottoy, Gert-Jan Hofman, É. Erdmann, B. Linclau, I. Kuprov, J. Martins, V. Torbeev, B. Kieffer","doi":"10.5194/mr-2021-54","DOIUrl":"https://doi.org/10.5194/mr-2021-54","url":null,"abstract":"Abstract. Proline homopolymer motifs are found in many proteins; their peculiar conformational and dynamic properties are often directly involved in those proteins' functions. However, the dynamics of proline homopolymers is hard to study by NMR due to lack of amide protons and small chemical shift dispersion. Exploiting the spectroscopic properties of fluorinated prolines opens interesting perspectives to address these issues. Fluorinated prolines are already widely used in protein structure engineering – they introduce conformational and dynamical biases – but their use as 19F NMR reporters of proline conformation has not yet been explored. In this work, we look at model peptides where Cγ-fluorinated prolines with opposite configurations of the chiral Cγ centre have been introduced at two postions in distinct polyproline segments. By looking at the effects of swapping these (4R)- and (4S)-4-fluoroprolines witin the polyproline segments, we were able to separate the intrinsic conformational properties of the polyproline sequence from the conformational alterations instilled by fluorination. We assess the fluoroproline 19F relaxation properties, and exploit the latter in elucidating binding kinetics to the SH3 domain.\u0000","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43548356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rapid measurement of heteronuclear transverse relaxation rates using non-uniformly sampled <i>R</i>_1<i>ρ</i> accordion experiments.","authors":"Sven Wernersson, Göran Carlström, Andreas Jakobsson, Mikael Akke","doi":"10.5194/mr-2-571-2021","DOIUrl":"10.5194/mr-2-571-2021","url":null,"abstract":"<p><p>Multidimensional, heteronuclear NMR relaxation methods are used extensively to characterize the dynamics of biological macromolecules. Acquisition of relaxation datasets on proteins typically requires significant measurement time, often several days. Accordion spectroscopy offers a powerful means to shorten relaxation rate measurements by encoding the \"relaxation dimension\" into the indirect evolution period in multidimensional experiments. Time savings can also be achieved by non-uniform sampling (NUS) of multidimensional NMR data, which is used increasingly to improve spectral resolution or increase sensitivity per unit time. However, NUS is not commonly implemented in relaxation experiments, because most reconstruction algorithms are inherently nonlinear, leading to problems when estimating signal intensities, relaxation rate constants and their error bounds. We have previously shown how to avoid these shortcomings by combining accordion spectroscopy with NUS, followed by data reconstruction using sparse exponential mode analysis, thereby achieving a dramatic decrease in the total length of longitudinal relaxation experiments. Here, we present the corresponding transverse relaxation experiment, taking into account the special considerations required for its successful implementation in the framework of the accordion-NUS approach. We attain the highest possible precision in the relaxation rate constants by optimizing the NUS scheme with respect to the Cramér-Rao lower bound of the variance of the estimated parameter, given the total number of sampling points and the spectrum-specific signal characteristics. The resulting accordion-NUS <math><mrow><msub><mi>R</mi><mrow><mn>1</mn><mi>ρ</mi></mrow></msub></mrow></math> relaxation experiment achieves comparable precision in the parameter estimates compared to conventional CPMG (Carr-Purcell-Meiboom-Gill) <math><mrow><msub><mi>R</mi><mn>2</mn></msub></mrow></math> or spin-lock <math><mrow><msub><mi>R</mi><mrow><mn>1</mn><mi>ρ</mi></mrow></msub></mrow></math> experiments while saving an order of magnitude in experiment time.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":" ","pages":"571-587"},"PeriodicalIF":0.0,"publicationDate":"2021-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10539792/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46684665","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":"Spin-Noise Gradient Echoes","authors":"V. Rodin, Stephan J. Ginthör, M. Bechmann, H. Desvaux, N. Müller","doi":"10.5194/mr-2021-55","DOIUrl":"https://doi.org/10.5194/mr-2021-55","url":null,"abstract":"Abstract. Nuclear spin-noise spectroscopy in absence of radio frequency pulses was studied under the influence of pulsed field gradients (PFGs) on pure and mixed liquids. Under conditions, where the radiation-damping induced line broadening is smaller than the gradient dependent inhomogeneous broadening, echo responses can be observed in difference spectra between experiments employing pulsed field gradient pairs of same and opposite signs. These observed “spin-noise gradient echoes” (SNGEs) were analyzed through a simple model to describe the effects of transient phenomena. Experiments performed on high resolution NMR probes demonstrate how “refocused spin noise” behaves and how it can be exploited to determine sample properties. In bulk liquids and their mixtures transverse relaxation times as well as translational diffusion constants can be determined from SNGE spectra recorded following tailored sequences of magnetic field gradient pulses.\u0000","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47470907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A cryogen-free, semi-automated apparatus for bullet-dynamic nuclear polarization with improved resolution","authors":"K. Kouřil, M. Gramberg, Michael Jurkutat, Hana Kouřilová, B. Meier","doi":"10.5194/mr-2021-57","DOIUrl":"https://doi.org/10.5194/mr-2021-57","url":null,"abstract":"Abstract. In dissolution-dynamic nuclear polarization, a hyperpolarized solid is dissolved with a jet of hot solvent. The solution is then transferred to a secondary magnet, where spectra can be recorded with improved sensitivity. In bullet-dynamic nuclear polarization this order is reversed. Pressurized gas is used to rapidly transfer the hyperpolarized solid to the secondary magnet, and the hyperpolarized solid is dissolved only upon arrival. A potential advantage of this approach is that it may avoid excessive dilution and the associated signal loss, in particular for small sample quantities. Previously, we have shown that liquid-state NMR spectra with polarization levels of up to 30 % may be recorded within less than 1 second after the departure of the hyperpolarized solid from the polarizing magnet. The resolution of the recorded spectra however was limited. The system consumed substantial amounts of liquid helium and substantial manual work was required in between experiments to prepare for the next shot. Here, we present a new bullet-DNP system that addresses these limitations.\u0000","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48276590","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}