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Oxygen-containing carbons are promising supports and metal-free catalysts for many reactions. However, distinguishing the role of various oxygen functional groups and quantifying and tuning each functionality is still difficult. Here we investigate the role of Brønsted acidic oxygen-containing functional groups by synthesizing a diverse library of materials. By combining acid-catalyzed elimination probe chemistry, comprehensive surface characterizations, 15N isotopically labeled acetonitrile adsorption coupled with magic-angle spinning nuclear magnetic resonance, machine learning, and density-functional theory calculations, we demonstrate that phenolic is the main acid site in gas-phase chemistries and unexpectedly carboxylic groups are much less acidic than phenolic groups in the graphitized mesoporous carbon due to electron density delocalization induced by the aromatic rings of graphitic carbon. The methodology can identify acidic sites in oxygenated carbon materials in solid acid catalyst-driven chemistry.

HIV-1 maturation inhibitors (MIs) interfere with the final step in the viral lifecycle by disrupting the ordered proteolytic processing of the viral Gag polyprotein into its individual domains. Bevirimat (BVM) and its analogs interfere with the final catalytic cleavage of spacer peptide 1 (SP1) from the capsid protein (CA) C-terminal domain (CACTD), by binding to and stabilizing the CACTD-SP1 region. MIs are under development as alternative drugs to augment current antiretroviral therapies. Although promising, their mechanism of action and associated virus resistance pathways remain poorly understood at the molecular, biochemical, and structural levels. Here, we report atomic-resolution magic angle spinning (MAS) NMR structures of microcrystalline assemblies of CACTD-SP1 complexed with BVM and/or the assembly cofactor inositol hexakisphosphate (IP6). BVM and IP6 can bind simultaneously to SP1, with BVM positioned in the center of its 6-helix bundle in a unique conformation. Importantly, the NMR-observed structural effects of BVM on IP6 binding suggest that the inhibitor stabilizes the 6-helix bundle in multiple ways. In addition, BVM-resistant SP1-A1V and SP1-V7A variants exhibit distinct conformational and binding characteristics. Taken together, our results reveal a novel allosteric mechanism by which BVM disrupts maturation and provide a structural explanation for BVM resistance as well as important guidance for the design of new MIs.

(19)F magic angle spinning (MAS) NMR spectroscopy is a powerful tool for characterization of fluorinated solids. The recent development of (19)F MAS NMR probes, operating at spinning frequencies of 60–111 kHz, enabled analysis of systems spanning from organic molecules to pharmaceutical formulations to biological assemblies, with unprecedented resolution. Herein, we systematically evaluate the benefits of high MAS frequencies (60–111 kHz) for 1D and 2D (19)F-detected experiments in two pharmaceuticals, the antimalarial drug mefloquine and a formulation of the cholesterol-lowering drug atorvastatin calcium. We demonstrate that (1)H decoupling is essential and that scalar-based, heteronuclear single quantum coherence (HSQC) and heteronuclear multiple quantum coherence (HMQC) correlation experiments become feasible and efficient at the MAS frequency of 100 kHz. This study opens doors for the applications of high frequency (19)F MAS NMR to a wide range of problems in chemistry and biology.

Ruthenium (Ru) is the one of the most promising catalysts for polyolefin hydrogenolysis. Its performance varies widely with the support, but the reasons remain unknown. Here, we introduce a simple synthetic strategy (using ammonia as a modulator) to tune metal-support interactions and apply it to Ru deposited on titania (TiO2). We demonstrate that combining deuterium nuclear magnetic resonance spectroscopy with temperature variation and density functional theory can reveal the complex nature, binding strength, and H amount. H2 activation occurs heterolytically, leading to a hydride on Ru, an H+ on the nearest oxygen, and a partially positively charged Ru. This leads to partial reduction of TiO2 and high coverages of H for spillover, showcasing a threefold increase in hydrogenolysis rates. This result points to the key role of the surface hydrogen coverage in improving hydrogenolysis catalyst performance.

The nucleocapsid (N) protein is one of the four structural proteins of the SARS-CoV-2 virus and plays a crucial role in viral genome organization and, hence, replication and pathogenicity. The N-terminal domain (N

Heteronuclear dipolar coupling is indispensable in revealing vital information related to the molecular structure and dynamics, as well as intermolecular interactions in various solid materials. Although numerous approaches have been developed to selectively reintroduce heteronuclear dipolar coupling under MAS, most of them lack universality and can only be applied to limited spin systems. Herein, we introduce a new and robust technique dubbed phase modulated rotary resonance (PMRR) for reintroducing heteronuclear dipolar couplings while suppressing all other interactions under a broad range of MAS conditions. The standard PMRR requires the radiofrequency (RF) field strength of only twice the MAS frequency, can efficiently recouple the dipolar couplings with a large scaling factor of 0.50, and is robust to experimental imperfections. Moreover, the adjustable window modification of PMRR, dubbed wPMRR, can improve its performance remarkably, making it well suited for the accurate determination of dipolar couplings in various spin systems. The robust performance of such pulse sequences has been verified theoretically and experimentally via model compounds, at different MAS frequencies. The application of the PMRR technique was demonstrated on the H-ZSM-5 zeolite, where the interaction between the Bronsted acidic hydroxyl groups of H-ZSM-5 and the absorbed trimethylphosphine oxide (TMPO) were probed, revealing the detailed configuration of super acid sites.

Microtubules (MTs) and their associated proteins play essential roles in maintaining cell structure, organelle transport, cell motility, and cell division. Two motors, kinesin and cytoplasmic dynein link the MT network to transported cargos using ATP for force generation. Here, we report an all-atom NMR structure of nucleotide-free kinesin-1 motor domain (apo-KIF5B) in complex with paclitaxel-stabilized microtubules using magic-angle-spinning (MAS) NMR spectroscopy. The structure reveals the position and orientation of the functionally important neck linker and how ADP induces structural and dynamic changes that ensue in the neck linker. These results demonstrate that the neck linker is in the undocked conformation and oriented in the direction opposite to the KIF5B movement. Chemical shift perturbations and intensity changes indicate that a significant portion of ADP-KIF5B is in the neck linker docked state. This study also highlights the unique capability of MAS NMR to provide atomic-level information on dynamic regions of biological assemblies.

We report remarkably high, up to 100-fold, signal enhancements in (19)F dynamic nuclear polarization (DNP) magic angle spinning (MAS) spectra at 14.1 T on HIV-1 CA capsid protein assemblies. These enhancements correspond to absolute sensitivity ratios of 12–29 and are of similar magnitude as seen for (1)H signals in the same samples. At MAS frequencies above 20 kHz, it was possible to record 2D (19)F-(13)C HETCOR spectra, which contain long-range intra- and intermolecular correlations. Such correlations provide unique distance restraints, inaccessible in conventional experiments without DNP for protein structure determination. Furthermore, systematic quantification of the DNP enhancements as a function of biradical concentration, MAS frequency, temperature, and microwave power is reported. Our work establishes the power of DNP-enhanced (19)F MAS NMR spectroscopy for structural characterization of HIV-1 CA assemblies and this approach is anticipated to be applicable to a wide range of large biomolecular systems.

19 F NMR spectroscopy is an attractive and growing area of research with broad applications in biochemistry, chemical biology, medicinal chemistry, and materials science. We have explored fast magic angle spinning (MAS) 19 F solid-state NMR spectroscopy in assemblies of HIV-1 capsid protein. Tryptophan residues with fluorine substitution at the 5-position of the indole ring were used as the reporters. The 19 F chemical shifts for the five tryptophan residues are distinct, reflecting differences in their local environment. Spin-diffusion and radio-frequency-driven-recoupling experiments were performed at MAS frequencies of 35 kHz and 40-60 kHz, respectively. Fast MAS frequencies of 40-60 kHz are essential for consistently establishing 19 F-19 F correlations, yielding interatomic distances of the order of 20 A. Our results demonstrate the potential of fast MAS 19 F NMR spectroscopy for structural analysis in large biological assemblies.

We report 43 Ca and 13 C solid-state nuclear magnetic resonance (NMR) spectroscopic studies of the ethylene glycol solvate of atorvastatin calcium. The 13 C and 43 Ca chemical shift and 43 Ca quadrupolar coupling tensor parameters are reported. The results are interpreted in terms of the reported X-ray diffraction crystal structure of the solvate and are compared with the NMR parameters of atorvastatin calcium trihydrate, the active pharmaceutical ingredient in Lipitor®. Hartree-Fock and density functional theory calculations of the NMR parameters based on a cluster model derived from the optimized X-ray diffraction crystal structure of the ethylene glycol solvate of atorvastatin calcium are in reasonable agreement with the experimental 43 Ca and 13 C NMR measurables.

Maturation of HIV-1 particles encompasses a complex morphological transformation of Gag via an orchestrated series of proteolytic cleavage events. A longstanding question concerns the structure of the C-terminal region of CA and the peptide SP1 (CA–SP1), which represents an intermediate during maturation of the HIV-1 virus. By integrating NMR, cryo-EM, and molecular dynamics simulations, we show that in CA–SP1 tubes assembled in vitro, which represent the features of an intermediate assembly state during maturation, the SP1 peptide exists in a dynamic helix–coil equilibrium, and that the addition of the maturation inhibitors Bevirimat and DFH-055 causes stabilization of a helical form of SP1. Moreover, the maturation-arresting SP1 mutation T8I also induces helical structure in SP1 and further global dynamical and conformational changes in CA. Overall, our results show that dynamics of CA and SP1 are critical for orderly HIV-1 maturation and that small molecules can inhibit maturation by perturbing molecular motions., The process of HIV particle maturation involves complex molecular transitions. Here the authors combine NMR spectroscopy, cryo-EM, and molecular dynamics simulations to provide insight into the conformational equilibria in CA-SP1 assemblies relevant to HIV-1 maturation intermediates formation.

International audience; The recent breakthroughs in NMR probe technologies resulted in the development of MAS NMR probes with rotation frequencies exceeding 100 kHz. Herein, we explore dramatic increases in sensitivity and resolution observed at MAS frequencies of 110-111 kHz in a novel 0.7 mm HCND probe that enable structural analysis of fully protonated biological systems. Proton- detected 2D and 3D correlation spectroscopy under such conditions requires only 0.1-0.5 mg of sample and a fraction of time compared to conventional 13C-detected experiments. We discuss the performance of several proton- and heteronuclear- (13C-,15N-) based correlation experiments in terms of sensitivity and resolution, using a model microcrystalline fMLF tripeptide. We demonstrate the applications of ultrafast MAS to a large, fully protonated protein assembly of the 231-residue HIV-1 CA capsid protein. Resonance assignments of protons and heteronuclei, as well as 1H-15N dipolar and 1HN CSA tensors are readily obtained from the high sensitivity and resolution proton-detected 3D experiments. The approach demonstrated here is expected to enable the determination of atomic-resolution structures of large protein assemblies, inaccessible by current methodologies.