Applied Magnetic Resonance最新文献

{"title":"Application of Spin-Dependent Microwave Photoconductivity for Detection of Magnetic Resonance of Recombination Centers on Silicon Surface and Si/SiO2 Interface","authors":"L. S. Vlasenko","doi":"10.1007/s00723-026-01877-1","DOIUrl":"10.1007/s00723-026-01877-1","url":null,"abstract":"<div><p>The results of observation of microwave photoconductivity response induced by spin-dependent recombination effects involving surface paramagnetic centers in silicon wafers are reported. Surface recombination centers were observed in commercially available wafers subjected to oxidization on air at room temperature. The variations of microwave photoconductivity were detected not only under magnetic resonance but also at the magnetic field values corresponding to crossing and anticrossing points of magnetic sublevels of surface recombination centers.</p></div>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"57 9","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148928117","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessing Feasibility for Diffusometry of Low-γ Nuclei in Concentrated Electrolytes: Direct-Observe 109Ag PFG NMR","authors":"Trent R. Graham","doi":"10.1007/s00723-026-01872-6","DOIUrl":"10.1007/s00723-026-01872-6","url":null,"abstract":"<div><p>Extending pulsed-field-gradient (PFG) NMR diffusometry to non-routine nuclei requires distinguishing apparent free-induction decay from the refocusable coherence available during echo-based diffusion experiments. Here, concentrated aqueous AgNO₃ is used to evaluate relaxation constraints governing direct-observe ¹⁰⁹Ag PFG NMR diffusometry. ¹⁰⁹Ag exhibits slow longitudinal relaxation (T₁ ≈ 600 s), making experimental throughput a practical limitation, and a short apparent transverse decay (T₂* = 0.1 s), which could suggest restricted diffusion-encoding feasibility. Hahn-echo measurements show that much of this apparent dephasing is refocusable, and Carr-Purcell-Meiboom-Gill measurements quantify the longer refocused transverse relaxation time (T₂, CPMG = 60 s). Using timing parameters selected within these measured relaxation constraints, convection-compensated PFG measurements yielded a ¹⁰⁹Ag self-diffusion coefficient of 8.2 × 10⁻¹⁰ m² s⁻¹ with a regression-derived relative uncertainty of approximately 2.4% at 2σ. This work establishes practical experimental constraints for direct-observe ¹⁰⁹Ag diffusometry and illustrates an approach for evaluating nuclei with unfavorable NMR properties by experimentally characterizing refocusable coherence before attempting diffusion measurements.</p></div>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"57 9","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148838322","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Features of Water Proton Relaxation in Saccharide Solutions: The Role of Chemical Exchange and Relaxation Dispersion","authors":"Tsukhlova Daria,&nbsp;Melnikova Daria,&nbsp;Shchitova Ekaterina,&nbsp;Tolstoy Peter,&nbsp;Sevryugin Vyacheslav,&nbsp;Skirda Vladimir","doi":"10.1007/s00723-026-01879-z","DOIUrl":"10.1007/s00723-026-01879-z","url":null,"abstract":"<div><p>Identifying individual relaxation mechanisms in carbohydrate solutions from single-frequency NMR relaxation-dispersion data often remains ambiguous. Here, we employ a cross-frequency approach combined with variable-temperature multipulse CPMG NMR experiments at 20 and 400 MHz (293–311 K) to deconvolve superimposed pathways of proton transverse relaxation, with the results interpreted using approximation-free kinetic Monte Carlo simulations. For pure water at 20 MHz, the observed dispersion profile is governed predominantly by heteronuclear ¹H–¹⁷O scalar relaxation of the second kind. In xylose solutions, the dispersion at both frequencies contains an additional dominant contribution from two-site chemical exchange between water protons and saccharide hydroxyl groups. Variable-temperature experiments reveal an inversion of the macroscopic temperature dependence of <i>R</i>₂ at the two frequencies: upon cooling, the amplitude of the relaxation-dispersion profile increases at 20 MHz, corresponding to fast-exchange conditions, but decreases at 400 MHz, corresponding to slow-exchange conditions, while the position of the dispersion inflection point remains unchanged at <i>τ</i>_eff approximately 0.31 ms, consistent with ∆<i>ω</i>⁻¹. Kinetic Monte Carlo simulations reproduce this inversion, show that cooling leads to an exponential increase in the microscopic exchange lifetime <i>τ</i>_ex from about 1.4–4.1 ms, corresponding to an activation energy of about 45 kJ/mol, and yield mutually consistent parameter values at both frequencies. The analysis further gives a chemical-shift difference of about 1.27 ppm between free water and xylose hydroxyl groups, which is independent of concentration.</p></div>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"57 9","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148838321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaluation of NMR Relaxation via an Entropic Perspective","authors":"Leonid Grunin,&nbsp;Mariia Ivanova,&nbsp;Valeriia Baranauskaite,&nbsp;Tatiana Grunina","doi":"10.1007/s00723-026-01880-6","DOIUrl":"10.1007/s00723-026-01880-6","url":null,"abstract":"<div><p>The Bloembergen–Purcell–Pound (BPP) theory predicts an unlimited shortening of the transverse relaxation time <i>T</i>₂ as the correlation time <i>τ</i>_c grows, which contradicts the finite, dipolar-broadening-limited decay observed in rigid solids. Herein this slow-motion divergence is addressed by explicitly introducing the rigid-lattice (static) transverse relaxation time <i>T</i>_2st, derived from the Van Vleck second moment <i>M</i>₂, as the natural lower bound of <i>T</i>₂. The result is a single closed-form expression valid over the entire <i>τ</i>_c range, which reproduces the BPP curve in the fast-motion regime and converges to <i>T</i>_2st in the rigid limit. The factor <i>w</i> = <i>T</i>_2st/<i>τ</i>_c + 1 = <i>T</i>₂/<i>T</i>_2st has a transparent physical meaning: it counts the number of distinguishable microstates that the spin system visits within the observation window <i>T</i>_2st, which suggests a Boltzmann-type entropic parameter <i>S</i>_NMR = <i>R</i> ln(<i>T</i>₂/<i>T</i>_2st). Combined with the Eyring equation of transition-state theory, the corrected expression relates <i>T</i>₂ directly to the thermodynamic functions of local molecular fluctuations. The approach was validated on water, methanol, ethanol, toluene, N-methyl-2-pyrrolidone, glycerol, natural rubber and microcrystalline cellulose, a set spanning more than five orders of magnitude in <i>τ</i>_c. Calculated and experimentally measured <i>T</i>₂ values agree closely, and <i>S</i>_NMR correlates linearly with the effective entropic difference <i>S</i>_E with a slope close to unity. This supports an entropic reading of NMR relaxation and offers a complement to the conventional Arrhenius treatment of correlation times.</p></div>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"57 9","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148837609","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lanthanide Spin Labels for Biomolecular NMR: Chemical Design and Structural Applications","authors":"Alexander Yu. Rudenko,&nbsp;Sofia S. Mariasina,&nbsp;Ratislav M. Ozhiganov,&nbsp;Vladimir I. Polshakov","doi":"10.1007/s00723-026-01876-2","DOIUrl":"10.1007/s00723-026-01876-2","url":null,"abstract":"<div><p>Paramagnetic NMR spectroscopy provides long-range structural restraints that complement conventional NMR methods, enabling the characterization of biomolecules in solution beyond the distance limits of traditional nuclear Overhauser effects. Among available paramagnetic probes, lanthanide-based spin labels are particularly valuable, because they generate multiple complementary observables, including paramagnetic relaxation enhancements (PREs), pseudocontact shifts (PCSs), and residual dipolar couplings (RDCs), which report on molecular structure, dynamics, and intermolecular interactions. This review summarizes the principles and recent advances of lanthanide-assisted biomolecular NMR spectroscopy, with emphasis on the chemical design and application of lanthanide spin labels. We discuss the physical basis and structural information content of PRE, PCS, and RDC measurements, and review major classes of lanthanide-chelating tags (LCTs) and lanthanide-binding peptide tags (LBTs). Particular attention is given to coordination chemistry, site-specific labeling strategies, and approaches that improve tag rigidity, reduce conformational averaging, and enhance the accuracy of paramagnetic restraints. We also examine modern labeling methodologies, including cysteine-based, bioorthogonal, noncanonical amino acid, and two-point attachment approaches. Finally, recent developments integrating paramagnetic NMR with computational structure prediction, multimodal NMR/EPR methods, solvent PRE techniques, and studies of dynamic biomolecular systems are highlighted, underscoring the growing importance of lanthanide spin labels in structural biology.</p></div>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"57 9","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148752218","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The spin–lattice relaxation rates and conformational characteristics of lysine dendrigrafts: a molecular dynamics study","authors":"Oleg V. Shavykin,&nbsp;Emil I. Fatullaev,&nbsp;Igor M. Neelov,&nbsp;Denis A. Markelov","doi":"10.1007/s00723-026-01871-7","DOIUrl":"10.1007/s00723-026-01871-7","url":null,"abstract":"<div><p>In this study, we performed molecular dynamics simulations of first- and second-generation lysine-based dendrigrafts in aqueous solution over the temperature range from 280 to 340 K. The second-order orientational autocorrelation function and spin–lattice NMR relaxation time are used to describe the orientational mobility of the CH<span>(_2)</span> groups in both dendrigrafts. The mobility of the terminal and side CH₂-N groups in both macromolecules is in qualitative agreement with the NMR results obtained previously for the lysine dendrimer. The inner groups of the second-generation dendrigraft behave differently from the inner groups in the dendrimer (NMR data) and the <span>(epsilon)</span>-lysine-based chain. The average backbone end-to-end distance is the same for both dendrigrafts. However, the second-generation dendrigraft exhibits reduced fluctuations in this characteristic. We also showed that the dendrigrafts have a spherical shape. The size, shape, and density distribution of the dendrigrafts are independent of temperature over the studied temperature range. Dendrigrafts are more compact than the lysine-based dendrimer and have a higher density. This leads to some displacement of water and counterions. Consequently, the relative charge of the macromolecule increases, and there are more hydrogen bonds per amino acid residue.</p></div>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"57 8","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148751166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structure of Si- and B-Promoted AlPO-11 According to Solid-State NMR and DFT Calculations","authors":"Ilya V. Yakovlev,&nbsp;Aleksandr V. Toktarev,&nbsp;Evgeniy S. Papulovskiy,&nbsp;Aleksandr A. Shubin,&nbsp;Olga B. Lapina","doi":"10.1007/s00723-026-01873-5","DOIUrl":"10.1007/s00723-026-01873-5","url":null,"abstract":"<div><p>This paper investigates the structural effects of silicon (Si) and boron (B) substitution in AlPO-11 with AEL framework, comparing pure AlPO-11, SAPO-11 (Si-only), and BSAPO-11 (Si + B). Using multinuclear solid-state nuclear magnetic resonance (NMR) spectroscopy (¹H, ²⁷Al, ²⁹Si, ³¹P) combined with density functional theory (DFT) calculations (Gauge Including Projector Augmented Waves (GIPAW) method), we demonstrate that Si substitution alone disrupts the ordered AlPO-11 structure, creating five-coordinated Al sites and resulting in heterogeneous Si distribution comprising both isolated sites and larger silica rafts (evidenced by a broad ²⁹Si signal at ~ -110 ppm). In contrast, simultaneous introduction of boron promotes more uniform Si distribution, eliminating silica rafts and reducing silanol groups while increasing medium-strength Brønsted acid sites (¹H signal at 3.7 ppm).</p></div>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"57 8","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148751167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Detection of Partial Structuring of Amorphous Carbon Using Solid-State 13C, 1H Nuclear Magnetic Resonance Spectroscopy","authors":"Galina Kupriyanova,&nbsp;Ivan Mershiev,&nbsp;Mark Smirnov,&nbsp;Aleksei Grunin,&nbsp;Gennady Kopitsa,&nbsp;Valery Savin","doi":"10.1007/s00723-026-01867-3","DOIUrl":"10.1007/s00723-026-01867-3","url":null,"abstract":"<div><p>Amorphous carbon samples intended for use as effective battery anode materials were studied using solid-state ¹³C and ¹H NMR spectroscopy. The study revealed a number of changes in the amorphous state that occurred during additional processing of the synthesized sample. It was found that sample milling resulted in the appearance of an additional signal in the ¹³C NMR spectrum with a chemical shift of <i>δ</i> = 110 ppm, attributed to oxides, and an intense proton NMR signal. In the annealed sample, a ratio of sp²- to sp³-hybridized carbon atoms of 21:6 was detected. ¹H and ¹³C NMR studies of the processed samples and modeling showed that thermal annealing at temperatures above 600°C leads to a transition from amorphous carbon to partially ordered graphene-like domains. This structuring is confirmed by the appearance of resonances in the high-field region of the spectrum [δ (¹H) = −7.5–7.0 ppm, δ (¹³C) = −22 ppm], which arise due to increased bulk susceptibility and strong diamagnetic ring currents in limited interlayer spaces (~8–10 Å). The calculated values of the ring currents correspond to currents induced in π-conjugated fragments consisting of 37–61 hexagonal rings, which provides the first spectroscopic fingerprint of nanoconfined protons in regions of the order of 8–10 Å in the obtained carbon materials.</p></div>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"57 8","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148751375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Density Functional Studies of Sensitivity of Amide 15N Chemical Shielding Tensors to Protein Backbone Dihedral Angles: Correlation Between Dihedral-Angle-Based 15N Shielding Predictions and Direct 15N Shielding Calculations in β-Sheet Structures of Proteins","authors":"Shaniya Sunny,&nbsp;Sivakumar Paramasivam","doi":"10.1007/s00723-026-01846-8","DOIUrl":"10.1007/s00723-026-01846-8","url":null,"abstract":"<p>Nuclear magnetic shielding interaction of backbone nuclei is the most direct probe of secondary structure of proteins due to its wide variation in shielding parameters in response to changes in electronic environments. In this report, we demonstrate the exclusive sensitivity of backbone amide ¹⁵N chemical shielding tensor (CST) components to the two adjacent dihedral angles <span>({psi}_{i-1})</span> and <span>({phi}_{i})</span> of the amide group using density functional studies of the central alanine residue of a model tripeptide <i>N</i>-formyl–glycyl–alanyl–leucine–amide. Especially, we show that <span>({psi}_{i-1})</span> has a dominant effect on the ¹⁵N principal components <span>({sigma}_{11})</span> and <span>({sigma}_{22})</span>, whereas <span>({phi}_{i})</span> affects <span>({sigma}_{22})</span> and <span>({sigma}_{33})</span> the most. Through the construction of theoretical ¹⁵N shielding surfaces of the model tripeptide as functions of <span>({psi}_{i-1})</span> and <span>({phi}_{i})</span>, the predicted ¹⁵N CSTs are compared with direct ¹⁵N shielding calculations for 20 alanine-containing tripeptide segments selected randomly from regular α-helical and β-sheet regions of 13 protein structures available in the literature. In contrast to the poor correlation observed for α-helical segments, β-sheet segments exhibit a significant correlation between shielding-surface-predicted and directly calculated ¹⁵N shielding components with <span>({sigma}_{22})</span> and <span>({sigma}_{text{i}text{s}text{o}})</span> having the largest correlation, in agreement with experimental ¹⁵N chemical shift studies in the literature. Using alanine as a model for other amino acid types, a similar comparison between the alanine-based ¹⁵N shielding and the direct ¹⁵N CST calculations for 38 tripeptide segments with non-alanine central residues from sheet regions of four proteins reaffirms the unique sensitivity of <span>({sigma}_{22})</span> and <span>({sigma}_{text{i}text{s}text{o}})</span> to backbone dihedral angles irrespective of the identity of side chains.</p>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"57 8","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148628499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Catechol Moiety Determines the Anti-peroxyl Radical Capacity of Dopamine and Norepinephrine: A Kinetic EPR Study","authors":"Gaspar H. Kocharyan,&nbsp;Adrine D. Sahakyan,&nbsp;Zaruhi H. Manukyan,&nbsp;Samvel Kh. Stepanyan,&nbsp;Makich V. Musaelyan","doi":"10.1007/s00723-026-01865-5","DOIUrl":"10.1007/s00723-026-01865-5","url":null,"abstract":"<div><p>Catecholamines are biologically important neurotransmitters and hormones that may also contribute to endogenous antioxidant defense. In this work, the anti-peroxyl radical capacity of dopamine and norepinephrine, together with the model catechol compounds catechol and caffeic acid, was studied toward <i>tert</i>-butylperoxyl radicals <span>(left(tert-{text{butylOO}}^{bullet }right))</span>. The proper anti-peroxyl radical capacity was directly determined using a kinetic-EPR method with pulsed reagent injection, which enables real-time monitoring of peroxyl radical consumption during reaction with antioxidants. The capacity values of all investigated compounds were found to be close to 2, indicating similar stoichiometry of their interaction with peroxyl radicals. These results show that the catechol moiety, containing two ortho phenolic hydroxyl groups, is the key structural fragment responsible for the antiradical capacity of catecholamines. Side-chain differences did not significantly affect the measured capacity, consistent with the literature BDE data showing lower O-H-bond dissociation energies in the catechol moiety.</p></div>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"57 8","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148614780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}