Solid state nuclear magnetic resonance最新文献

{"title":"Solid-state NMR compositional analysis of sputum from people with cystic fibrosis","authors":"Kathy Duong ,&nbsp;Evan Moss ,&nbsp;Courtney Reichhardt","doi":"10.1016/j.ssnmr.2024.101975","DOIUrl":"10.1016/j.ssnmr.2024.101975","url":null,"abstract":"<div><div>People with the genetic disease cystic fibrosis (CF) often have chronic airway infections and produce airway secretions called sputum. A better understanding of sputum composition is desired in order to track changes in response to CF therapeutics and to improve laboratory models for the study of CF airway infections. The glycosylated protein mucin is a primary component. Along with extracellular DNA, mucin gives rise to the high viscoelasticity of sputum, which inhibits airway clearance and is thought to promote chronic airway infections in people with CF. Past studies of sputum composition identified additional biomolecular components of sputum including other proteins, both glycosylated and not glycosylated, free amino acids, and lipids. Typically, studies of sputum, as well as other complex biological materials, have focused on soluble or isolated components. Solid-state NMR is not limited to the study of soluble components. Instead, it can provide molecular-level information about insoluble biological samples. Additionally, solid-state NMR can provide information about sample composition without requiring any processing of the sample, eliminating the possibility of misestimating certain components due to insolubility or potential sample loss in isolation steps. In this study, we used both ¹³C and ³¹P CPMAS to investigate the total composition of sputum samples obtained from six people with CF. We compared these spectra to those of commercially available mucin, DNA, and phospholipid samples. Lastly, we performed complementary biochemical analyses to identify specific proteins present in the sputum samples. Overall, our findings provide insight into the composition of unprocessed sputum samples from people with CF, which can be used as a benchmark for future investigations of CF and infections in the airways of people with CF. Further, this study provides opportunities to expand the solid-state NMR approach to include dynamic nuclear polarization (DNP) to obtain high-resolution information of sputum and similar biological samples that are not feasible to isotopically enrich.</div></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"134 ","pages":"Article 101975"},"PeriodicalIF":1.8,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142569403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Elucidating structure and metabolism of insect biomaterials by solid-state NMR","authors":"Christine Chrissian ,&nbsp;Michael L. Stawski ,&nbsp;Andrew P. Williams ,&nbsp;Ruth E. Stark","doi":"10.1016/j.ssnmr.2024.101974","DOIUrl":"10.1016/j.ssnmr.2024.101974","url":null,"abstract":"<div><div>Among the many natural biomaterials for which information on atomic-level structure and reorientational motion can offer essential clues to function, insoluble multi-component composites with limited degrees of order are among the most challenging to study. Despite its limited sensitivity, solid-state NMR (ssNMR) is often the technique of choice to ferret out these details in carbon- and nitrogen-rich materials: this spectroscopic approach can probe many biomaterials in their native or near-native states, either with or without the introduction of stable NMR-active isotopes, or with the assistance of dynamic nuclear polarization technology. During a span of close to four decades, such research targets and ssNMR approaches have been exemplified by insects, a diverse and evolutionarily agile group of organisms with global impacts that include ecology, agriculture, and human disease. In this short review, we present case studies on insect cuticles that range from protective exoskeletons and egg capsules to the wing structures that enable flight and showcase nature's awe-inspiring beauty, highlighting the use of ssNMR spectroscopy to profile chemical composition, elucidate macromolecular architecture, and monitor metabolic development in these fascinating biological assemblies.</div></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"134 ","pages":"Article 101974"},"PeriodicalIF":1.8,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142508285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Glucose hydrochar consists of linked phenol, furan, arene, alkyl, and ketone structures revealed by advanced solid-state nuclear magnetic resonance","authors":"Shichen Yuan ,&nbsp;Avery Brown ,&nbsp;Zhaoxi Zheng ,&nbsp;Robert L. Johnson ,&nbsp;Karen Agro ,&nbsp;Andrea Kruse ,&nbsp;Michael T. Timko ,&nbsp;Klaus Schmidt-Rohr","doi":"10.1016/j.ssnmr.2024.101973","DOIUrl":"10.1016/j.ssnmr.2024.101973","url":null,"abstract":"<div><div>The molecular structure of hydrochars produced from ¹³C-enriched glucose under various conditions has been elucidated based on advanced one- and two-dimensional (2D) ¹H-¹³C and ¹³C–¹³C solid-state nuclear magnetic resonance (NMR) with spectral editing. Regardless of synthesis conditions, hydrochars consist mostly of oxygen-substituted arene rings (including diphenols) and furans connected by alkyl linkers rich in ketones. Cross-linking nonprotonated and methyne (C-H) alkyl carbons have been identified through spectrally edited 2D NMR. Alkenes and ‘quaternary’ C-O are observed only at low synthesis temperature, while some clusters of fused arene rings are generated at high temperature. Hydrochar composition is nearly independent of reaction time in the range from 1 to 5 h. Equilibration of ¹³C magnetization within 1 s shows that the materials are homogeneous on the 5-nm scale, refuting core–shell models of hydrochar microspheres. While furan C-O carbons bonded to alkyl groups or ketones show distinctive cross peaks in 2D NMR, phenolic C-OH is observed unambiguously by hydroxyl-proton selection. While methylene-linked furan rings are fairly common, the signal previously assigned to furan Cα-Cα linkages is shown to arise from abundant, stable catecholic <em>ortho</em>-diphenols, whose HO-C=C-OH structure is proved by 2D¹³C–¹³C NMR after hydroxyl-proton selection. Quantitative ¹³C NMR spectra of low- and high-temperature hydrochars have been matched by chemical-shift simulations for representative structural models. Mixed phenol and furan rings connected by ketones and alkyl linkers provide good fits of the experimental spectra, while literature models dominated by large clusters of fused rings and with few phenols or alkyl-linked ketones do not.</div></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"134 ","pages":"Article 101973"},"PeriodicalIF":1.8,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142432093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cryogenic probe technology enables multidimensional solid-state NMR of the stratum corneum without isotope labeling","authors":"Barbara Perrone ,&nbsp;Maria Gunnarsson ,&nbsp;Diana Bernin ,&nbsp;Emma Sparr ,&nbsp;Daniel Topgaard","doi":"10.1016/j.ssnmr.2024.101972","DOIUrl":"10.1016/j.ssnmr.2024.101972","url":null,"abstract":"<div><div>Solid-state NMR has great potential for investigating molecular structure, dynamics, and organization of the <em>stratum corneum</em>, the outer 10–20 μm of the skin, but is hampered by the unfeasibility of isotope labelling as generally required to reach sufficient signal-to-noise ratio for the more informative multidimensional NMR techniques. In this preliminary study of pig <em>stratum corneum</em> at 35 °C and water-free conditions, we demonstrate that cryogenic probe technology offers sufficient signal boost to observe previously undetectable minor resonances that can be uniquely assigned to fluid cholesterol, ceramides, and triacylglycerols, as well as enables ¹H–¹H spin diffusion monitored by 2D ¹H-¹³C HETCOR to estimate 1–100 nm distances between specific atomic sites on proteins and lipids. The new capabilities open up for future multidimensional solid-state NMR studies to answer long-standing questions about partitioning of additives, such as pharmaceutically active substances, between solid and liquid domains within the protein and lipid phases in the <em>stratum corneum</em> and the lipids of the sebum.</div></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"134 ","pages":"Article 101972"},"PeriodicalIF":1.8,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142366563","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-resolution 2D solid-state NMR provides insights into nontuberculous mycobacteria","authors":"Chang-Hyeock Byeon ,&nbsp;Kasper Holst Hansen ,&nbsp;William DePas ,&nbsp;Ümit Akbey","doi":"10.1016/j.ssnmr.2024.101970","DOIUrl":"10.1016/j.ssnmr.2024.101970","url":null,"abstract":"<div><div>We present a high-resolution magic-angle spinning (MAS) solid-state NMR (ssNMR) study to characterize nontuberculous mycobacteria (NTM). We studied two different NTM strains, <em>Mycobacterium smegmatis</em>, a model, non-pathogenic strain, and <em>Mycobacterium abscessus</em>, an emerging and important human pathogen. Hydrated NTM samples were studied at natural abundance without isotope-labelling, as whole-cells versus cell envelope isolates, and native versus fixed sample preparations. We utilized 1D¹³C and 2D ¹H-¹³C ssNMR spectra and peak deconvolution to identify NTM cell-wall chemical sites. More than ∼100 distinct ¹³C signals were identified in the ssNMR spectra. We provide tentative assignments for ∼30 polysaccharides by using well resolved ¹H/¹³C chemical shifts from the 2D INEPT-based ¹H-¹³C ssNMR spectrum. The signals originating from both the flexible and rigid fractions of the whole-cell bacteria samples were selectively analyzed by utilizing either CP or INEPT based ¹³C ssNMR spectra. CP buildup curves provide insights into the dynamical similarity of the cell-wall components for NTM strains. Signals from peptidoglycan, arabinogalactan and mycolic acid were identified. The majority of the ¹³C signals were not affected by fixation of the whole cell samples. The isolated cell envelope NMR spectrum overlap with the whole-cell spectrum to a large extent, where the latter has more signals. As an orthogonal way of characterizing these bacteria, electron microscopy (EM) was used to provide spatial information. ssNMR and EM data suggest that the <em>M. abscessus</em> cell-wall is composed of a smaller peptidoglycan layer which is more flexible compared to <em>M. smegmatis</em>, which may be related to its higher pathogenicity. Here in this work, we used high-resolution 2D ssNMR first time to characterize NTM strains and identify chemical sites. These results will aid the development of structure-based approaches to combat NTM infections.</div></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"134 ","pages":"Article 101970"},"PeriodicalIF":1.8,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142308575","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-resolution indirect detection of spin-3/2 quadrupolar nuclei in solids using multiple-quantum-filtered through-space D-HMQC experiments","authors":"Julien Trébosc ,&nbsp;Olivier Lafon ,&nbsp;Jean-Paul Amoureux","doi":"10.1016/j.ssnmr.2024.101971","DOIUrl":"10.1016/j.ssnmr.2024.101971","url":null,"abstract":"<div><div>Through-space heteronuclear correlation experiments under magic-angle spinning (MAS) conditions can provide unique insights into inter-atomic proximities. In particular, it has been shown that experiments based on two consecutive coherence transfers, ¹H → <em>I</em> → ¹H, like <em>D</em>-HMQC (dipolar-mediated heteronuclear multiple-quantum correlation), are usually more sensitive for the indirect detection via protons of spin-3/2 quadrupolar nuclei with low gyromagnetic ratio. Nevertheless, the resolution is often decreased by the second-order quadrupolar broadening along the indirect dimension. To circumvent this issue, we incorporate an MQMAS (multiple-quantum MAS) quadrupolar filter into the <em>t</em>₁ evolution period of the <em>D</em>-HMQC sequence, which results in a novel pulse sequence called <em>D</em>-HMQC-MQ. The triple-quantum coherences evolving during this filter are excited and reconverted using cosine-modulated long-pulses synchronized with the sample rotation to avoid spinning sidebands in the indirect dimension. The desired coherence transfer pathways during this sequence are selected using two nested cogwheel phase cycles with 56 steps. This high-resolution heteronuclear correlation technique is demonstrated experimentally for the indirect detection via ¹H of spin-3/2 isotopes, such as ¹¹B, ²³Na and ³⁵Cl, in zinc borate hydrate, NaH₂PO₄ and <span>l</span>-histidine hydrochloride, respectively. We show that this experiment can be applied at high magnetic fields up to 28.2 T for protons subject to chemical shift anisotropies larger than 20 ppm, provided the MAS frequency is sufficiently stable since the <em>D</em>-HMQC-MQ experiment, like the parent <em>D</em>-HMQC, is sensitive to MAS fluctuations, which can produce <em>t</em>₁-noise.</div></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"134 ","pages":"Article 101971"},"PeriodicalIF":1.8,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142366564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Theoretical investigation of the effects of diverse hydrogen-bonding characteristics on the 17O chemical shielding and electric field gradient tensors within the active sites of MraYAA bound to nucleoside antibiotics capuramycin, carbacaprazamycin, 3′-Hydroxymureidomycin A, and muraymycin D2","authors":"Elahe K. Astani ,&nbsp;Hossein Iravani ,&nbsp;Soroush Sardari","doi":"10.1016/j.ssnmr.2024.101960","DOIUrl":"10.1016/j.ssnmr.2024.101960","url":null,"abstract":"<div><p>This study builds upon our prior researches and seeks to investigate and clarify the influences of various characteristics of hydrogen bonds (H-bonds) and charge transfer (CT) interactions, which were detected within the inhibitor binding pockets (labeled as the QM models I–IV) of MraY_AA–capuramycin, MraY_AA–carbacaprazamycin, MraY_AA–3′-hydroxymureidomycin A, and MraY_AA–muraymycin D2 complexes by QTAIM and NBO analyses from DFT QM/MM MD calculations, on the ¹⁷O chemical shielding (CS) and electric field gradient (EFG) tensors of carboxylate (Oδ), carbonyl (C═O), and hydroxyl (O–H) oxygens in these models. The ¹⁷O CS and EFG tensors of these three types of oxygens in QM models I–IV were calculated at the M06-2X/6-31G** level by including the solvent effects using the polarizable continuum model. From the computed ¹⁷O CS and EFG tensors in these models, it was found that the nuclear shielding, σ_iso, for carboxylate or carbonyl oxygen increases (shielding effect) as the H-bond length decreases and the percentage p-character of <em>n</em>_Oδ/<em>n</em>_C═O lone pair partner in the CT interaction enhances. In contrast, the σ_iso (¹⁷O–H) decreases (deshielding effect) with a reduction in the H-bond length as well as with an enhancement in percentage s-character of the <em>n</em>_OH lone pair/σ*_O–H antibond. By reducing the H-bond length or by increasing p-character of the <em>n</em>_Oδ/<em>n</em>_C═O lone pair, the ¹⁷Oδ/¹⁷O═C quadrupole coupling constant smoothly decreases, while the ¹⁷Oδ/¹⁷O═C asymmetry parameter smoothly increases. Moreover, these calculated parameters are in a good agreement with the experimental values. The information garnered here is valuable particularly for further understanding of empirical correlations between ¹⁷O NMR spectroscopic and H-bonding characteristics in the protein–ligand complexes.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"133 ","pages":"Article 101960"},"PeriodicalIF":1.8,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142087875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cooperative β-sheet coassembly controls intermolecular orientation of amphiphilic peptide-polydiacetylene conjugates","authors":"Tarunya Rao Sudarshan ,&nbsp;Sujeung Lim ,&nbsp;Jeffrey Li ,&nbsp;Alicia S. Robang ,&nbsp;Leel Mazal Liberty ,&nbsp;Herdeline Ann M. Ardoña ,&nbsp;Anant K. Paravastu","doi":"10.1016/j.ssnmr.2024.101959","DOIUrl":"10.1016/j.ssnmr.2024.101959","url":null,"abstract":"<div><p>In this work, we elucidated the structural organization of stimuli-responsive peptide-polydiacetylene (PDA) conjugates that can self-assemble as 1D nanostructures under neutral aqueous conditions. The amino acid sequences bear positively or negatively charged domains at the periphery of the peptide segments to promote solubility in water while also driving assembly of the individual and combined components into β-sheets. The photopolymerization of PDA, as well as the sensitivity of the resulting optical properties of the polymeric material to external stimuli, highly depends on the structural organization of the assembly of amphiphilic peptide-diacetylene units into 1D-nanostructures. Solid-state NMR measurements on ¹³C-labeled and ¹⁵N-labeled samples show that positively charged and negatively charged peptide amphiphiles are each capable of self-assembly, but self-assembly favors antiparallel β-sheet structure. When positively and negatively charged peptide amphiphiles interact in stoichiometric solutions, cooperative coassembly dominates over self-assembly, resulting in the desired parallel β-sheet structure with a concomitant increase in structural order. These results reveal that rational placement of oppositely charged residues can control β-strand organization in a peptide amphiphile coassembly, which would have implications on the adaptive properties of stimuli-responsive biomaterials such as the peptide-PDAs studied here.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"133 ","pages":"Article 101959"},"PeriodicalIF":1.8,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142096517","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Predicting 35-Cl electric field gradient tensors in crystalline solids using cluster and fragment-corrected planewave density functional theory","authors":"Daniel Capistran ,&nbsp;James K. Harper ,&nbsp;Joshua D. Hartman","doi":"10.1016/j.ssnmr.2024.101949","DOIUrl":"10.1016/j.ssnmr.2024.101949","url":null,"abstract":"<div><p>Planewave-corrected methods have proven effective for accurately modeling nuclear magnetic resonance (NMR) parameters in crystalline systems. Recent work extended the application of planewave-corrected calculations beyond the second row, predicting EFG tensor parameters for ³⁵Cl using a simple molecular correction to projector augmented-wave (PAW) density functional theory (DFT). Here we extend this work using fragment and cluster-based calculations coupled with polarizable continuum (PCM) methods to improve further the accuracy of planewave-corrected ³⁵Cl EFG tensor calculations. Benchmark data from a test set comprised of 105 individual ³⁵Cl EFG tensor principal components for chlorine-containing molecular crystals and crystalline chloride salts shows fragment-corrected planewave calculations using the PBE0 hybrid density functional improve the accuracy of predicted EFG tensor components by 30 % relative to traditional planewave calculations. We compare the influence of different geometry optimization methods and density functionals on the accuracy of predicted ³⁵Cl EFG tensor parameters. Four cases of spectral assignment are presented to demonstrate the utility of improving the accuracy of predicted ³⁵Cl EFG tensor parameters.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"133 ","pages":"Article 101949"},"PeriodicalIF":1.8,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142049260","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Phenolic syringyl end groups in 13C-enriched hardwoods detected and quantified by solid-state NMR","authors":"Zhaoxi Zheng,&nbsp;Klaus Schmidt-Rohr","doi":"10.1016/j.ssnmr.2024.101947","DOIUrl":"10.1016/j.ssnmr.2024.101947","url":null,"abstract":"<div><p>While syringyl units are the most abundant monolignols in hardwood lignin, their phenolic (i.e. hydroxyl) end group concentration has not been measured. In two uniformly ¹³C-enriched young hardwoods, from beech and oak, the syringyl units were quantitatively investigated by advanced solid-state ¹³C NMR. Small signals of OH-terminated syringyl units were resolved in spectrally edited two-dimensional ¹³C–¹³C NMR spectra of the two hardwoods. Their distinct peak positions predicted based on literature data were validated via the abundant OH-terminated syringyl units in hydrolyzed ¹³C-beechwood. In a two-dimensional ¹³C–¹³C exchange spectrum with diagonal-ridge suppression, a well-resolved peak of phenolic syringyl units was observed at the characteristic C–H peak position of syringyl rings, without significant overlap from guaiacyl peaks. Accurate ¹³C chemical shifts of regular and end-group syringyl units were obtained. Through spectrally edited 2D NMR after ¹H inversion recovery, phenols of condensed tannin complexed with arginine were carefully analyzed and shown to overlap minimally with signals from phenolic syringyl units. The local structure and resulting spin dynamics of ether (chain) and hydroxyl (end-group) syringyl units are nearly the same, enabling quantification by peak integration or deconvolution, which shows that phenolic syringyl end groups account for 2 ± 1 % of syringyl units in beechwood and 5 ± 2 % in oakwood. The observed low end-group concentration needs to be taken into account in realistic molecular models of hardwood lignin structure.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"133 ","pages":"Article 101947"},"PeriodicalIF":1.8,"publicationDate":"2024-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141789075","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}