Journal of Magnetic Resonance Open最新文献

{"title":"A cryogenic tune and match circuit for magnetic resonance microscopy at 15.2T","authors":"Benjamin M Hardy ,&nbsp;Gary Drake ,&nbsp;Shuyang Chai ,&nbsp;Bibek Dhakal ,&nbsp;Jonathan B Martin ,&nbsp;Junzhong Xu ,&nbsp;Mark D Does ,&nbsp;Adam W Anderson ,&nbsp;Xinqiang Yan ,&nbsp;John C Gore","doi":"10.1016/j.jmro.2024.100147","DOIUrl":"https://doi.org/10.1016/j.jmro.2024.100147","url":null,"abstract":"<div><h3>Background and Significance</h3><p>Achievable signal to noise ratios (SNR) in magnetic resonance microscopy images are limited by acquisition times and the decreasing number of spins in smaller voxels. A common method of enhancing SNR is to cool the RF receiver coil. Significant SNR gains are realized only when the Johnson noise generated within the RF hardware is large compared to the electromagnetic noise produced by the sample. Cryogenic cooling of imaging probes is in common use in high field systems, but it is difficult to insulate a sample from the extreme temperatures involved and in practice imaging cryoprobes have been limited to surface or partial volume designs only. In order to use a solenoid in which the windings were not directly cooled and in close proximity to the sample, we designed a chamber to cool only the tune and match circuitry and show experimentally it is possible to achieve much of the theoretically available SNR gain.</p></div><div><h3>Methods</h3><p>A microcoil circuit consisting of two tuning capacitors, one fixed capacitor, and SMB coaxial cable was designed to resonate at 650 MHz for imaging on a Bruker 15.2 T scanner. Sample noise increases with the sample diameter, so surface loops and solenoids of varying diameters were tested on the bench to determine the largest diameter coil that demonstrated significant SNR gains from cooling. A liquid N₂ cryochamber was designed to cool the tune and match circuit, coaxial cable, and connectors, while leaving the RF coil in ambient air. As the cryochamber was filled with liquid N₂, quality factors were measured on the bench while monitoring the coil's surface temperature. Improvements of SNR on images of ionic solutions were demonstrated via cooling the tune and match circuit in the magnet bore.</p></div><div><h3>Results</h3><p>At 650 MHz, loops and solenoids &lt; 3 mm in diameter showed significant improvements in quality factor on the bench. The resistance of the variable capacitors and the coaxial cable were measured to be 45% and 32% of room temperature values near the Larmor frequency. Images obtained with a 2 turn, 3 mm diameter loop with the matching circuit at room temperature and then cooled with liquid nitrogen demonstrated SNR improvements of a factor of 2.</p></div><div><h3>Conclusions</h3><p>By cooling the tune and match circuit and leaving the surface loop in ambient air, SNR was improved by a factor of 2. The results are significant because it allows for more space to insulate the sample from the extreme temperatures used in imaging cryoprobes.</p></div>","PeriodicalId":365,"journal":{"name":"Journal of Magnetic Resonance Open","volume":"18 ","pages":"Article 100147"},"PeriodicalIF":2.624,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666441024000025/pdfft?md5=33a1923de6dd817b1d9a1302730c9e6f&pid=1-s2.0-S2666441024000025-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139737600","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":"Automated test apparatus for bench-testing the magnetic field homogeneity of NMR transceiver coils","authors":"Jose L. Uribe ,&nbsp;Matthew D. Jimenez ,&nbsp;Jessica I. Kelz ,&nbsp;Jeanie Liang ,&nbsp;Rachel W. Martin","doi":"10.1016/j.jmro.2023.100142","DOIUrl":"10.1016/j.jmro.2023.100142","url":null,"abstract":"<div><p>We describe an automated hands-off bench testing method for measuring the magnetic field profile of transceiver coils for nuclear magnetic resonance (NMR). The scattering parameter (S-parameter) data is measured using a portable network analyzer, and the results are automatically exported to a computer for plotting and viewing. This assay dramatically reduces the time needed to measure the magnetic field (B<span><math><msub><mrow></mrow><mrow><mn>1</mn></mrow></msub></math></span>) homogeneity profile of a transceiver coil while also improving accuracy relative to manual operation. Here, we demonstrate the method on a saddle coil of a solution-state NMR probe in comparison to profiles obtained using NMR spectroscopy measurements. We also measure the axial homogeneity of a variable-pitch solenoid.</p></div>","PeriodicalId":365,"journal":{"name":"Journal of Magnetic Resonance Open","volume":"18 ","pages":"Article 100142"},"PeriodicalIF":2.624,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S266644102300050X/pdfft?md5=f10df6d978721013022aa81eb59fba06&pid=1-s2.0-S266644102300050X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138825154","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":"Unilateral RF sensors based on parallel-plate architecture for improved surface-scan MRI analysis of commercial pouch cells","authors":"Konstantin Romanenko ,&nbsp;Nikolai Avdievich","doi":"10.1016/j.jmro.2023.100141","DOIUrl":"10.1016/j.jmro.2023.100141","url":null,"abstract":"<div><p>Rapid expansion of the Li-ion pouch cell market is driven by the looming problem of permanent depletion of natural gas reservoirs and by the growing demand for high-performance portable devices and electric vehicles. Safety and performance of Li-ion cells have been two main focal points of the extensive battery research. Surface-scan Magnetic Resonance Imaging (MRI) is an operando method designed for the accurate detection of substandard battery cells and for monitoring electrochemical processes with high spatial and temporal resolutions. Intercalation-dependent magnetism and charge transfer processes in the cell's electrodes give rise to characteristic magnetic field patterns outside the cell. For accurate mapping of such patterns, we proposed the concept of a unilateral radio-frequency (RF) sensor, a flat thin resonator encapsulating a proton-rich solid-state detection medium. When the pouch cell is placed in direct contact with the sensor, the magnetic field patterns propagate inside the detection medium, and the corresponding spatial distribution of Larmor precession frequencies can be detected with MRI. In this work, we developed and evaluated a series of RF sensor configurations based on parallel-plate architecture enhanced by arrays of distributed capacitors. The parallel-plate approach does not suffer from RF interference with pouch cells and provides excellent sensitivity and <em>B</em>₁-field homogeneity. The optimal configuration of the parallel-plate sensor depends on the dimensions of the pouch cell and the distribution of parallel capacitors. This article includes the results of experimental tests, RF-field simulations, and strategies to further improve the surface-scan MRI method.</p></div>","PeriodicalId":365,"journal":{"name":"Journal of Magnetic Resonance Open","volume":"18 ","pages":"Article 100141"},"PeriodicalIF":2.624,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666441023000493/pdfft?md5=f7329d64fedf9cf79efb3ba465098f1b&pid=1-s2.0-S2666441023000493-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138566345","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":"Intrinsically disordered proteins studied by NMR spectroscopy","authors":"Marco Schiavina,&nbsp;Lorenzo Bracaglia,&nbsp;Tessa Bolognesi,&nbsp;Maria Anna Rodella,&nbsp;Giuseppe Tagliaferro,&nbsp;Angela Sofia Tino,&nbsp;Roberta Pierattelli,&nbsp;Isabella C. Felli","doi":"10.1016/j.jmro.2023.100143","DOIUrl":"10.1016/j.jmro.2023.100143","url":null,"abstract":"<div><p>Intrinsically disordered proteins (IDPs) and intrinsically disordered regions (IDRs) of complex multi-domain proteins are now identified as a trend topic by the scientific community. NMR constitutes a unique investigation tool to access atom resolved information on their structural and dynamic properties, in isolation or upon interaction with potential partners (metal ions, small molecules, proteins, nucleic acids, membrane mimetics etc.). Their high flexibility and disorder, in contrast to more compact structures of globular protein domains, has a strong impact on NMR observables and NMR experiments should be tailored for their investigation. In this context, ¹³C direct detection NMR has become a very useful tool to contribute to IDPs/IDRs characterization at atomic resolution. 2D CON spectra can now be collected in parallel to 2D HN ones, and reveal information, which in some cases is not accessible through 2D HN spectra only, particularly when studying proteins in experimental conditions approaching physiological pH and temperature. The 2D HN/CON spectra are thus becoming a sort of identity card of an IDP/IDR in solution. Their simultaneous acquisition through multiple receiver NMR experiments is particularly useful to investigate the properties of highly flexible intrinsically disordered regions within complex multi-domain proteins, rather than in isolation as often performed to reduce the complexity of the system, an interesting perspective in the field.</p></div>","PeriodicalId":365,"journal":{"name":"Journal of Magnetic Resonance Open","volume":"18 ","pages":"Article 100143"},"PeriodicalIF":2.624,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666441023000511/pdfft?md5=30fae3a2e15e799bcb467f4fb0ac3c1f&pid=1-s2.0-S2666441023000511-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139028989","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":"Towards optical MAS magnetic resonance using optical traps","authors":"Lea Marti ,&nbsp;Nergiz Şahin Solmaz ,&nbsp;Michal Kern ,&nbsp;Anh Chu ,&nbsp;Reza Farsi ,&nbsp;Philipp Hengel ,&nbsp;Jialiang Gao ,&nbsp;Nicholas Alaniva ,&nbsp;Michael A. Urban ,&nbsp;Ronny Gunzenhauser ,&nbsp;Alexander Däpp ,&nbsp;Daniel Klose ,&nbsp;Jens Anders ,&nbsp;Giovanni Boero ,&nbsp;Lukas Novotny ,&nbsp;Martin Frimmer ,&nbsp;Alexander B. Barnes","doi":"10.1016/j.jmro.2023.100145","DOIUrl":"10.1016/j.jmro.2023.100145","url":null,"abstract":"<div><p>Higher magic angle spinning (MAS) frequencies than currently available are desirable to improve spectral resolution in NMR and EPR systems. While conventional strategies employ pneumatic spinning limited by fluid dynamics, this paper demonstrates the development of an optical spinning technique in which vacuum quality dictates the maximum achievable spinning frequency. Using optical traps, we levitated a range of micron-sized samples. Under vacuum we achieved optical rotation of a single ∼10 μm diameter particle of vaterite at several mbar up to hundreds of Hz and of 20 μm diameter SiO₂ particles at ≤10⁻² mbar at several kHz. At ambient conditions, we optically levitated γ-irradiated alanine particles of 20–50 μm diameter. Additionally, using a single chip EPR detector operating at 11 GHz, we measured the EPR spectrum for a 30 μm γ-irradiated alanine particle in contact with the chip surface (i.e., without optical levitation) in a single scan lasting 92 s. These observations suggest that a γ-irradiated alanine particle having a diameter in the order of 30 μm is a promising candidate for our aim of demonstrating the first magnetic resonance experiment on optically levitated samples. Furthermore, we discuss strategies, limitations, and the potential of implementing MAS with optical traps for NMR and EPR.</p></div>","PeriodicalId":365,"journal":{"name":"Journal of Magnetic Resonance Open","volume":"18 ","pages":"Article 100145"},"PeriodicalIF":2.624,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666441023000535/pdfft?md5=4e84d82c05ec47dbe1b80aae0b39bbee&pid=1-s2.0-S2666441023000535-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139036735","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":"CPMAS NMR platform for direct compositional analysis of mycobacterial cell-wall complexes and whole cells","authors":"Xinyu Liu ,&nbsp;Jasna Brčić ,&nbsp;Gail H. Cassell ,&nbsp;Lynette Cegelski","doi":"10.1016/j.jmro.2023.100127","DOIUrl":"10.1016/j.jmro.2023.100127","url":null,"abstract":"<div><p>Tuberculosis and non-tuberculosis mycobacterial infections are rising each year and often result in chronic incurable disease. Important antibiotics target cell-wall biosynthesis, yet some mycobacteria are alarmingly resistant or tolerant to currently available antibiotics. This resistance is often attributed to assumed differences in composition of the complex cell wall of different mycobacterial strains and species. However, due to the highly crosslinked and insoluble nature of mycobacterial cell walls, direct comparative determinations of cell-wall composition pose a challenge to analysis through conventional biochemical analyses. We introduce an approach to directly observe the chemical composition of mycobacterial cell walls using solid-state NMR spectroscopy. ¹³C CPMAS spectra are provided of individual components (peptidoglycan, arabinogalactan, and mycolic acids) and of <em>in situ</em> cell-wall complexes. We assigned the spectroscopic contributions of each component in the cell-wall spectrum. We uncovered a higher arabinogalactan-to-peptidoglycan ratio in the cell wall of <em>M. abscessus</em>, an organism noted for its antibiotic resistance, relative to <em>M. smegmatis</em>. Furthermore, differentiating influences of different types of cell-wall targeting antibiotics were observed in spectra of antibiotic-treated whole cells. This platform will be of value in evaluating cell-wall composition and antibiotic activity among different mycobacteria and in considering the most effective combination treatment regimens.</p></div>","PeriodicalId":365,"journal":{"name":"Journal of Magnetic Resonance Open","volume":"16 ","pages":"Article 100127"},"PeriodicalIF":2.624,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666441023000353/pdfft?md5=b8e77d4be33bc168b0286ba8cff3b61a&pid=1-s2.0-S2666441023000353-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85315161","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":"MR based magnetic susceptibility measurements of 3D printing materials at 3 Tesla","authors":"Maitreyi Sangal ,&nbsp;Maria Anikeeva ,&nbsp;Simon C. Priese ,&nbsp;Hendrik Mattern ,&nbsp;Jan-Bernd Hövener ,&nbsp;Oliver Speck","doi":"10.1016/j.jmro.2023.100138","DOIUrl":"10.1016/j.jmro.2023.100138","url":null,"abstract":"<div><p>Commercial availability, ease of printing and cost effectiveness have rendered 3D printing an essential part of magnetic resonance (MR) experimental design. However, the magnetic properties of several materials contemporarily used for 3D printing are lacking in literature to some extent. A database of the magnetic susceptibilities of several commonly used 3D printing materials is provided, which may aid MR experiment design. Here, we exploit the capability of magnetic resonance imaging (MRI) to map the local magnetic field variations caused by these materials when placed in the scanner's <strong>B₀</strong> field. Exact analytical solutions of the magnetic flux density distribution for a cylindrical geometry are utilized to fit experimentally obtained data with theory in order to quantify the magnetic susceptibilities. A detailed explanation of the data processing and fitting procedure is presented and validated by measuring the susceptibility of air along with high resolution MR measurements. Furthermore, an initiative is taken to address the need for a comprehensive database comprising of not only the magnetic susceptibilities of 3D printing materials, but also information on the 3D printing parameters, the printers used, and other information available for the materials that may also influence the measured magnetic properties. An open platform with the magnetic susceptibilities of materials reported in this work besides existing literature values is provided here, with the aim to invite researchers to enable further extension and development towards an open database to characterize commonly used 3D printing materials based on their magnetic properties.</p></div>","PeriodicalId":365,"journal":{"name":"Journal of Magnetic Resonance Open","volume":"16 ","pages":"Article 100138"},"PeriodicalIF":2.624,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666441023000468/pdfft?md5=7059452703c1c655bfc9078a4bbb9143&pid=1-s2.0-S2666441023000468-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135763368","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":"Affordable amino acid α/β-deuteration and specific labeling for NMR signal enhancement: Evaluation on the kinase p38α","authors":"Rania Ghouil ,&nbsp;Chafiaa Bouguechtouli ,&nbsp;Hélène Chérot ,&nbsp;Agathe Marcelot ,&nbsp;Maxime Roche ,&nbsp;Francois-Xavier Theillet","doi":"10.1016/j.jmro.2023.100126","DOIUrl":"https://doi.org/10.1016/j.jmro.2023.100126","url":null,"abstract":"<div><p>Although very effective in decreasing NMR relaxation of large proteins, homogeneous deuteration can be costly, and anyway unsuitable for recombinant production in metazoan systems. We sought to explore other deuteration schemes, which would be adapted to protein expression in mammalian cells. Here, we evaluate the benefits of the deuteration on alpha- and beta-positions of amino acids for a typical middle size protein domain, namely the model 40 kDa-large kinase p38α. We report the position-specific deuteration of free amino acids by using enzyme-assisted H/D exchange, executed by the cystathionine gamma-synthase and a newly designed high-performance mutant E325A. Then, we used cell-free expression in bacterial extracts to avoid any scrambling and back-protonation of the tested isotopically labelled amino acids (Ala, Leu, Lys, Ser, Asp, Glu, Gly). Our results show signal enhancements up to three in ¹H-¹⁵N spectra when these α/β-deuterated amino acids are integrated. Because our approach relies on single ²H_α/β-¹⁵N-amino acid labeling, an additional three-fold increase in sensitivity is obtained by the possible use of moderate resolution SOFAST-HMQC instead of the classical HSQC or TROSY experiments. This allows recording residue-resolved solution ¹H-¹⁵N NMR spectra of 100 μg of p38α in one hour with S/N∼10.</p></div>","PeriodicalId":365,"journal":{"name":"Journal of Magnetic Resonance Open","volume":"16 ","pages":"Article 100126"},"PeriodicalIF":2.624,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"1826370","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":"Segmented solenoid RF coils for MRI of ex vivo brain samples at ultra-high field preclinical and clinical scanners","authors":"Daniel Papoti ,&nbsp;Diego Szczupak ,&nbsp;Luiz G.C. Santos ,&nbsp;Khallil T. Chaim ,&nbsp;Maria C.G. Otaduy ,&nbsp;David J. Schaeffer ,&nbsp;Edson L.G. Vidoto ,&nbsp;Alberto Tannús ,&nbsp;Afonso C. Silva","doi":"10.1016/j.jmro.2023.100103","DOIUrl":"https://doi.org/10.1016/j.jmro.2023.100103","url":null,"abstract":"<div><p>Magnetic resonance imaging (MRI) is a well-known and widespread imaging modality for neuroscience studies and the clinical diagnoses of neurological disorders, mainly due to its capability to visualize brain microstructures and quantify various metabolites. Additionally, its noninvasive nature makes possible the correlation of high-resolution MRI from ex vivo brain samples with histology, supporting the study of neurodegenerative disorders such as Alzheimer's or Parkinson's disease. However, the quality and resolution of ex vivo MRI highly depend on the availability of specialized radiofrequency coils with maximized filling factors for the different sizes and shapes of the samples to be studied. For instance, small, dedicated radiofrequency (RF) coils are not always commercially available in ultrahigh field whole-body MRI scanners. Even for ultrahigh field preclinical scanners, specific RF coils for <em>ex vivo</em> MRI are expensive and not always available. Here, we describe the design and construction of two RF coils based on the solenoid geometry for <em>ex vivo</em> MRI of human brain tissues in a 7T whole-body scanner and for <em>ex vivo</em> MRI of marmoset brain samples in a 9.4T preclinical scanner. We designed the 7T solenoid RF coil to maximize the filling factor of human brain samples conditioned on cassettes for histology, while the 9.4T solenoid was constructed to accommodate marmoset brain samples conditioned in 50 ml centrifuge tubes. Both solenoid designs operate in transceiver mode. The measured B₁⁺ maps show a high level of homogeneity in the imaging volume of interest, with a high signal-to-noise ratio over the imaging volume. High-resolution (80 µm in plane, 500 µm slice thickness) images of human brain samples were acquired with the 7T solenoid, while marmoset brain samples were acquired with an isotropic resolution of 60 µm using the 9.4T solenoid coil.</p></div>","PeriodicalId":365,"journal":{"name":"Journal of Magnetic Resonance Open","volume":"16 ","pages":"Article 100103"},"PeriodicalIF":2.624,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3451233","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":"Plant defensins as a model to study the thermostability of surface hydrophobic clusters: The Pisum sativum defensin 2 (Psd2)","authors":"Ramon Pinheiro-Aguiar ,&nbsp;Caroline Corrêa-Almeida ,&nbsp;Eleonora Kurtenbach ,&nbsp;Fabio C.L. Almeida","doi":"10.1016/j.jmro.2023.100106","DOIUrl":"https://doi.org/10.1016/j.jmro.2023.100106","url":null,"abstract":"<div><p>Plant defensins (PDs) display a CSαβ-fold that lacks a canonical hydrophobic core. They display almost all hydrophobic residues on the protein surface. The exposed hydrophobic residues form surface clusters stabilized by the vicinity of hydrophilic residues and the hydration shell. Here, we used Psd2 as a model to study the formation and stabilization of these local foldons named surface hydrophobic clusters (SHC). We characterized the temperature dependence of ¹⁵N CPMG relaxation dispersion profiles to describe the complex dynamics of Psd2 and indirectly study the thermodynamics of SHCs in PDs. We show a correlation between residues undergoing conformational exchange and the SHCs. Chemical shift changes between the native ground state and the first thermally accessible excited state enabled us to map the major conformational changes in Psd2 conformational equilibrium. The observation of a cold-driven excited state revealed that SHCs are stabilized by hydrophobic contacts, which are exposed at low temperatures, leading to a favorable decrease in enthalpy compensated by an unfavorable entropy reduction. At higher temperatures, we detected another excited conformer that may play a role in membrane-specific interaction, as previously described for other defensins.</p></div>","PeriodicalId":365,"journal":{"name":"Journal of Magnetic Resonance Open","volume":"16 ","pages":"Article 100106"},"PeriodicalIF":2.624,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"1826461","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}