Article
Chemistry, Physical
D. Shimon, I Kaminker
Summary: Dynamic nuclear polarization (DNP) at high magnetic fields is an important technique for signal enhancement in nuclear magnetic resonance (NMR). This paper extends the theory of the electron-electron spectral-diffusion-based indirect cross effect (iCE) to include broadband microwave irradiation, allowing for quantitative fitting of DNP spectra lineshapes using different datasets. The study reveals that the DNP mechanism changes with excitation bandwidth, with iCE dominating the DNP spectrum at high bandwidth.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Article
Materials Science, Multidisciplinary
Zhaomei Liu, Bei Zhao, Chunhong Jiao, Lihua Zhao, Xingxing Han
Summary: A broadband polarization conversion metasurface based on cross-shaped resonators in microwave regime is proposed in this paper. The simulated results demonstrate high conversion efficiency and polarization selectivity of the metasurface, making it potentially useful in polarization-controlled devices, stealth surfaces, antennas, and other applications.
APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING
(2021)
Article
Chemistry, Analytical
Cornelia Rasmussen, David W. Hoffman
Summary: This paper introduces a novel nuclear magnetic resonance (NMR) tool for determining position-specific carbon isotope ratios within complex organic molecules. The method allows for the measurement of isotope ratios in samples containing impurities that overlap with the signals of interest. The method was validated using reference materials and successfully applied to determine position-specific isotope ratios in real samples.
ANALYTICAL CHEMISTRY
(2022)
Article
Chemistry, Organic
Michael B. Elbaum, Mahmoud A. Elkhalifa, Gary A. Molander, David M. Chenoweth
Summary: Forging new C(sp(3))-C(sp(3)) bonds to central positions within a peptide backbone is achieved by using electron-donor-acceptor complexes between Hantzsch ester and on-resin peptide N-hydroxyphthalimide radical precursors. The feasibility of this method is demonstrated through two-carbon homologations and homologation cyclizations of Atosiban and RGDf.
Review
Biochemistry & Molecular Biology
Suzeeta Bhandari, Kirpal S. Bisht, David J. Merkler
Summary: Fatty acid amides are lipids composed of a fatty acid and a biogenic amine. This review focuses on a lesser-known sub-class of fatty acid amides called N-acyl aromatic amino acids (NA-ArAAs). The review highlights the identified NA-ArAAs from biological sources and presents information on their biosynthesis, degradation, enzymatic modification, and transport, as well as their cellular functions. The aim of this review is to stimulate future research on this underappreciated sub-class of the fatty acid amide family.
FRONTIERS IN MOLECULAR BIOSCIENCES
(2022)
Article
Chemistry, Multidisciplinary
Yun Ma, Ryan A. Woltornist, Russell F. Algera, David B. Collum
Summary: This study compared the catalytic effects of PMDTA and TMEDA, highlighting the importance of trifunctionality and kappa(2)-kappa(3) hemilability. PMDTA showed remarkable acceleration in reactions, with up to >30-fold accelerations using 10 mol % PMDTA. Additionally, solid-liquid phase-transfer catalysis was explored as a means to optimize the catalysis and explore the advantages of heterogeneous reaction conditions.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2021)
Article
Chemistry, Organic
Mahmoud Elkhalifa, Michael B. Elbaum, David M. Chenoweth, Gary A. Molander
Summary: This research demonstrates the compatibility of photochemistry with solid-phase peptide synthesis, using photochemical hydroalkylation to form C(sp(3))-C(sp(3)) bonds on resin. High yields were achieved using iridium-based photocatalysts and Hantszch ester, with full conversions within 30 minutes under ambient conditions. The chemistry is compatible with a broad range of peptide side chains, redox-active esters, and resin, representing the first example of photochemical peptide modifications on resin.
Article
Chemistry, Organic
Hao Tian, Shaoxiang Yang, Xiaochen Wang, Wentao Xu, Yuxiu Liu, Yongqiang Li, Qingmin Wang
Summary: This study presents a convenient and general protocol for the monofluoroalkenylation reactions of alkyl bromides using cooperative visible-light photoredox catalysis and halogen abstraction. Mechanistic experiments revealed that the product formation involves selective cross-coupling of aliphatic radicals with fluoroalkenyl radicals. The protocol, enabled by silyl radical-mediated halogen abstraction, can be applied to a broad range of alkyl and heteroaryl halides, as demonstrated by its successful application to cholesterol.
JOURNAL OF ORGANIC CHEMISTRY
(2021)
Article
Computer Science, Information Systems
Bianmei Zhang, Chenghui Zhu, Ran Zhang, Xiaofan Yang, Ye Wang, Xiaoming Liu
Summary: An ultra-broadband angular-stable reflective linear to cross polarization converter based on metasurface has been developed, showing high efficiency, strong polarization conversion capability, wide bandwidth, and angular stability.
Article
Chemistry, Multidisciplinary
Yu-Feng Zhang, Jia-Huan Wang, Ning-Yuan Yang, Zheng Chen, Li-Lei Wang, Qiang-Shuai Gu, Zhong-Liang Li, Xin-Yuan Liu
Summary: A copper-catalyzed enantioconvergent radical C-N cross-coupling of alkyl halides with sulfoximines (as ammonia surrogates) under mild conditions has been developed using a chiral anionic N,N,N-ligand with a long spreading side arm. This method efficiently and selectively synthesizes a range of α,α-disubstituted amino acid derivatives. The synthetic utility of the strategy has been demonstrated through the elaboration of the coupling products into different chiral α-fully substituted amine building blocks.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Multidisciplinary Sciences
Max Fleckenstein, Kevin Herr, Franziska Theiss, Stephan Knecht, Laura Wienands, Martin Brodrecht, Michael Reggelin, Gerd Buntkowsky
Summary: A specific labeling strategy for bioactive molecules, using eptifibatide as an example, was presented and validated in this study. The results demonstrate that this labeling strategy can successfully insert into the disulfide bridge of biomolecules, with minimal impact on their tertiary structure, and significantly enhance the nuclear spin hyperpolarization. This labeling strategy shows high potential for applications.
SCIENTIFIC REPORTS
(2022)
Article
Chemistry, Physical
Gerd Kothe, Michail Lukaschek, Tomoaki Yago, Gerhard Link, Konstantin L. Ivanov, Tien-Sung Lin
Summary: Quantum entanglement has been achieved in various physical systems, including quantum dots, trapped atomic ions, and superconductors. In this study, specific molecular solids are proposed as promising alternative platforms for quantum entanglement. A model system involving triplet pentacene in a host single crystal at level anticrossing (LAC) conditions is presented, with experiments demonstrating the generation of 14-qubit entangled nuclear spin states. These results lay the foundation for large-scale quantum information processing with multiqubit entanglement states.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Chemistry, Multidisciplinary
Marie Juramy, Romain Chevre, Paolo Cerreia Vioglio, Fabio Ziarelli, Eric Besson, Stephane Gastaldi, Stephane Viel, Pierre Thureau, Kenneth D. M. Harris, Giulia Mollica
Summary: This study demonstrates the use of dynamic nuclear polarization (DNP) enhanced NMR spectroscopy to investigate crystallization under nanoscopic confinement, successfully observing the early stages of crystallization and intermediate phases. The experimental strategy allows for the direct observation of the transition from the solution phase to the first crystalline phase.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2021)
Article
Chemistry, Multidisciplinary
Lisanne Sellies, Ruud L. E. G. Aspers, Martin C. Feiters, Floris P. J. T. Rutjes, Marco Tessari
Summary: In recent years, the scope of non-hydrogenative parahydrogen hyperpolarization (nhPHIP) techniques has been expanding, allowing for the detection and quantification of unmodified alpha-amino acids in complex mixtures. This method has shown great potential as demonstrated in human urine samples.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Review
Biochemistry & Molecular Biology
Jing Liu, Xia-lian Wu, Yu-teng Zeng, Zhi-heng Hu, Jun-xia Lu
Summary: Amyloids have unique structural properties and play a role in various biological functions. They are associated with a group of incurable neurodegenerative diseases. Solid-state NMR has been widely used to study amyloid structures and dynamics, leading to significant progress in understanding amyloids and related diseases.
Article
Chemistry, Physical
Alexander J. Stirk, Benjamin H. Wilson, Christopher A. O'Keefe, Hazem Amarne, Kelong Zhu, Robert W. Schurko, Stephen J. Loeb
Summary: The study explores the concept of robust dynamics by incorporating mechanically interlocked molecules into metal-organic framework materials, allowing large amplitude motions. New T-shaped linkers were designed and synthesized to create various MOFs with specific structures, demonstrating the potential for creating MOFs with diverse functions and dynamics.
Article
Chemistry, Physical
Adam R. Altenhof, Michael J. Jaroszewicz, Kristopher J. Harris, Robert W. Schurko
Summary: The study explores the use of wideband uniform-rate smooth-truncation pulses for measuring T-1 constants and introduces two new experiments for solid-state NMR spectra with broad powder patterns. Results show that in some favorable cases, one experiment allows for faster T-1 measurement compared to the other, while also highlighting the importance of interpreting T-1 values cautiously.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Chemistry, Multidisciplinary
Ivan Hung, Adam R. Altenhof, Robert W. Schurko, David L. Bryce, Oc Hee Han, Zhehong Gan
Summary: This study demonstrates how field-stepped NMR spectroscopy using the series-connected hybrid magnet at the U.S. National High Magnetic Field Laboratory can be used to acquire ultra-wideline powder spectra of nuclei with very large quadrupolar interactions. It also highlights the significant differences in spectra acquired using different methods, such as WURST/CPMG compared to the frequency-stepped method commonly used with superconducting magnets, due to magnetic field-dependent NMR interactions. This finding underscores the importance of taking into account the inequivalence when accurately determining quadrupolar coupling and chemical shift parameters.
MAGNETIC RESONANCE IN CHEMISTRY
(2021)
Article
Chemistry, Multidisciplinary
Benjamin H. Wilson, Cameron S. Vojvodin, Ghazale Gholami, Louae M. Abdulla, Christopher A. O'Keefe, Robert W. Schurko, Stephen J. Loeb
Summary: A study demonstrated that by inserting an H-shaped rotaxane with specific structure into different MOFs, rotaxane-containing MOFs with precise spatial arrangements of components can be formed. Through the use of VT solid-state nuclear magnetic resonance (SSNMR), it was found that the dynamics of the rotor are influenced by the presence of the macrocycle, while the translational position of the macrocyclic wheel along the rotaxane axle is dictated by the bulk and rotational orientation of the central rotor.
Article
Chemistry, Multidisciplinary
Adam R. Altenhof, Sungsool Wi, Robert W. Schurko
Summary: Solid-state NMR spectroscopy of integer-spin quadrupolar nuclei is crucial for material and biological solid characterization, with the BRAIN-CP pulse sequence showing promise for acquiring high-quality spectra. However, there are challenges in understanding the spin dynamics behind BRAIN-CP and in generalizing its application to wide and ultra-wide line NMR.
MAGNETIC RESONANCE IN CHEMISTRY
(2021)
Article
Chemistry, Multidisciplinary
Cameron S. Vojvodin, Sean T. Holmes, Lara K. Watanabe, Jeremy M. Rawson, Robert W. Schurko
Summary: Mechanochemical synthesis provides new pathways for the design of multi-component crystals. This study reports the mechanochemical syntheses of urea-containing crystals and demonstrates the utility of solid-state NMR and density functional theory calculations for structural characterization. These techniques show promise for future crystal structure prediction using NMR.
Article
Medicine, Research & Experimental
Sean T. Holmes, James M. Hook, Robert W. Schurko
Summary: This study employs solid-state NMR spectroscopy and density functional theory calculations to characterize the structure of chloride salts in nutraceuticals. The NMR parameters and computational analysis provide a rapid assessment of structural features and help detect impurities and counterfeit solid phases.
MOLECULAR PHARMACEUTICS
(2022)
Article
Biochemical Research Methods
Adam R. Altenhof, Zhehong Gan, Robert W. Schurko
Summary: The CPMG pulse sequence is crucial for enhancing signal of solid-state NMR spectra influenced by various factors, and the effects of dipolar couplings, short refocusing pulses, and experimental conditions on T-2 lifetimes have been well documented.
JOURNAL OF MAGNETIC RESONANCE
(2022)
Article
Chemistry, Physical
Eva Meirovitch, Zhichun Liang, Robert W. Schurko, Stephen J. Loeb, Jack H. Freed
Summary: The application of the microscopic-order-macroscopic-disorder (MOMD) approach for analyzing dynamic H-2 NMR lineshapes in metal-organic frameworks (MOFs) is described in this study. By comparing the experimental results of UiO-68-d(4) and UWDM-9-d(4), it is found that MOFs with different structures exhibit different dynamic characteristics, and the phenyl-d(4) dynamics is more isotropic in a more crowded environment.
JOURNAL OF PHYSICAL CHEMISTRY B
(2022)
Article
Chemistry, Physical
Sean T. Holmes, Cameron S. Vojvodin, Natan Veinberg, Emilia M. Iacobelli, David A. Hirsh, Robert W. Schurko
Summary: This study focuses on characterizing the molecular-level structures and dynamics of hydrates of active pharmaceutical ingredients (APIs) using NMR spectroscopy and DFT calculations. The results show that the relationship between Cl-35 EFG tensors and hydrogen bonding geometries is complex, but can be understood through DFT calculations. The study also demonstrates the potential of using variable-temperature NMR experiments to monitor temperature-dependent influences on the spectra of APIs.
SOLID STATE NUCLEAR MAGNETIC RESONANCE
(2022)
Article
Chemistry, Multidisciplinary
Austin A. Peach, Sean T. Holmes, Leonard R. MacGillivray, Robert W. Schurko
Summary: Competitive milling and stability milling mechanochemical reactions were used to assess the thermodynamic stabilities and cocrystallization affinities of pharmaceutical cocrystals of fluoxetine HCl with different coformers. The results showed that benzoic acid had the highest cocrystallization affinity, and the cocrystalline form of fluoxetine HCl with benzoic acid was the most stable.
Article
Biochemical Research Methods
Adam R. Altenhof, Harris E. Mason, Robert W. Schurko
Summary: NMR spectroscopy is insensitive to the amount of observable signal. Signal-to-noise ratio (SNR) can be improved by averaging or post-processing with apodization, but these methods result in long experimental times or loss of spectral resolution. Denoising techniques based on singular-value decomposition (SVD) can enhance SNR without compromising resolution, but are computationally expensive for large datasets. This study introduces a new wavelet transform (WT) method for fast and robust denoising of 1D and 2D NMR spectra, which offers similar or improved denoising compared to SVD and operates faster in some cases. All denoising and processing routines used in this work are included in a free and open-source Python library called DESPERATE.
JOURNAL OF MAGNETIC RESONANCE
(2023)
Article
Chemistry, Multidisciplinary
Louae M. Abdulla, Austin A. Peach, Sean T. Holmes, Zachary T. Dowdell, Lara K. Watanabe, Emilia M. Iacobelli, David A. Hirsh, Jeremy M. Rawson, Robert W. Schurko
Summary: This study investigates the various solid forms of Xylazine HCl (X) and explores the reliable preparation and interconversion methods for these forms. It also discovers a novel polymorph and synthesizes three cocrystals. Thermal analysis, X-ray diffraction, and solid-state NMR spectroscopy are used to characterize the materials. 35Cl SSNMR proves to be versatile in fingerprinting polymorphs and detecting features that PXRD cannot show, offering a pathway for optimizing synthetic protocols and providing molecular-level structural information.
CRYSTAL GROWTH & DESIGN
(2023)
Article
Chemistry, Physical
Adam R. Altenhof, Michael J. Jaroszewicz, Lucio Frydman, Robert W. Schurko
Summary: Currently, there are no reliable methods for separating and resolving overlapping powder patterns in ultra-wideline (UW) solid-state NMR spectra under static conditions. However, relaxation assisted separation (RAS) techniques, which exploit relaxation differences, have been successful in MRI and solution-state NMR for separating such signals. In this study, we implement principal component analysis (PCA) denoising and regularization techniques to improve the resolution of overlapped patterns in the RAS method, and extend these methods to 3D frequency-R-1-R-2 correlation spectra. The results show improved pattern resolution, indicating great potential for separating overlapping powder patterns under both static and magic-angle spinning (MAS) conditions.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Meeting Abstract
Chemistry, Multidisciplinary
Austin A. Peach, Kirill Levin, Carl Fleischer, Sean T. Holmes, Robert W. Schurko
ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES
(2021)