Science.gov

Sample records for 11b solid-state nmr

  1. An efficient 2D (11)B-(11)B solid-state NMR spectroscopy strategy for monitoring covalent self-assembly of boronic acid-derived compounds: the transformation and unique architecture of bortezomib molecules in the solid state.

    PubMed

    Brus, J; Czernek, J; Urbanova, M; Kobera, L; Jegorov, A

    2016-12-21

    The difficulty in the prediction of the complicated solid-state structure of boronic acid derivatives, resulting from the complex pathway of reversible covalent interactions, represents a significant obstacle to the development of a new generation of advanced supramolecular systems such as covalent organic frameworks of efficient anticancer drugs. In this contribution, various 2D (11)B-(11)B solid-state NMR correlation techniques supported by DFT calculations were explored to formulate a reliable tool for monitoring the covalent assembly of boronic acid residues in the solid state. This way, the self-condensation of bortezomib molecules was investigated, different local constitutions of boroxine motifs were unveiled, and the previously unreported boroxine structures of bortezomib polymorphs exhibiting secondary coordination were discovered and described in detail. The recorded (11)B NMR parameters responded sensitively to subtle changes in the local geometries, which were reliably interpreted and directly visualized by the DFT calculations. A uniform 2.6 Å distance in bortezomib (11)B-(11)B spin pairs was conclusively identified by the through-space (11)B-(11)B double-quantum (DQ) coherence build-up curves, whereas distinct 2D (11)B-(11)B DQ correlation patterns revealed unique boroxine structures existing in the crystalline as well as amorphous state. The boroxine rings were found to be internally stabilized through the transformation of the trigonal boron sites toward tetrahedral geometry, as the secondary five-membered rings were formed. This way, the nature of bortezomib polymorphism is disclosed, and an efficient strategy for exploring the assembly of boronic acid derivatives in the solid state, for which no crystallographic data are available, is thus demonstrated.

  2. (11)B Solid-State NMR Interaction Tensors of Linear Two-Coordinate Boron: The Dimesitylborinium Cation.

    PubMed

    Alain, Amanda E; Shoji, Yoshiaki; Fukushima, Takanori; Bryce, David L

    2015-12-21

    Borinium cations (R2B(+)) are of particular fundamental and applied interest in part due to their pronounced Lewis acidity which enables unique chemical transformations. Solid-state NMR spectroscopy of magic-angle spinning and stationary powdered samples of the dicoordinate boron cation in the recently reported dimesitylborinium tetrakis(pentafluorophenyl)borate compound (Shoji et al. Nature Chem. 2014, 6, 498) is applied to characterize the (11)B electric field gradient (EFG) and chemical shift (CS) tensors. The experimental data are consistent with linear C-B(+)-C geometry. The (11)B quadrupolar coupling constant, 5.44 ± 0.08 MHz, and the span of the CS tensor, 130 ± 1 ppm, are both particularly large relative to literature data for a variety of boron functional groups, and represent the first such data for the linear C-B(+)-C borinium moiety. The NMR data are similar to those for the neutral tricoordinate analogue, trimesitylborane, but contrast with those of the Cp*2B(+) cation. Quantum chemical calculations are applied to provide additional insights into the relationship between the NMR observables and the molecular and electronic structure of the dimesitylborinium cation.

  3. Solid-state NMR spectroscopy of proteins.

    PubMed

    Müller, Henrik; Etzkorn, Manuel; Heise, Henrike

    2013-01-01

    Solid-state NMR spectroscopy proved to be a versatile tool for characterization of structure and dynamics of complex biochemical systems. In particular, magic angle spinning (MAS) solid-state NMR came to maturity for application towards structural elucidation of biological macromolecules. Current challenges in applying solid-state NMR as well as progress achieved recently will be discussed in the following chapter focusing on conceptual aspects important for structural elucidation of proteins.

  4. Full differentiation and assignment of boron species in the electrolytes Li{sub 2}B{sub 6}O{sub 9}F{sub 2} and Li{sub 2}B{sub 3}O{sub 4}F{sub 3} by solid-state {sup 11}B NMR spectroscopy

    SciTech Connect

    Braeuniger, Thomas; Pilz, Thomas; Chandran, C. Vinod; Jansen, Martin

    2012-10-15

    The syntheses of two new fluorooxoborates, Li{sub 2}B{sub 3}O{sub 4}F{sub 3} and Li{sub 2}B{sub 6}O{sub 9}F{sub 2}, which possess considerable ion conductivity at higher temperatures, have been reported recently. Here, we describe the characterisation of these compounds by solid-state {sup 11}B NMR spectroscopy. The complex central-transition MAS spectra, resulting from overlap of sub-spectra contributed by the individual boron species in the crystal structures, could be clearly separated by acquisition and analysis of 3QMAS spectra. By numerical fit of these sub-spectra, the isotropic chemical shift {delta}{sub iso}, the quadrupolar coupling constant {chi}, and the asymmetry {eta} were determined. Using known relations between boron coordination and chemical shift as well as quadrupolar coupling, the individual {sup 11}B NMR resonances have been ascribed to boron species in tetrahedral or trigonal environment. To remove remaining assignment ambiguities, the response of the {sup 11}B resonances to {sup 19}F decoupling was qualitatively analysed. Thus, by using the combined information conveyed by chemical shift, quadrupolar and dipolar interaction, a complete assignment of the complex {sup 11}B line shapes exhibited by the fluorooxoborates has been achieved. - Graphical abstract: Structure and solid-state {sup 11}B NMR spectrum of Li{sub 2}B{sub 3}O{sub 4}F{sub 3}. Highlights: Black-Right-Pointing-Pointer Characterisation of title compounds by solid-state {sup 11}B NMR spectroscopy. Black-Right-Pointing-Pointer Sub-spectra of boron species separated by evaluation of 3QMAS spectra. Black-Right-Pointing-Pointer Isotropic chemical shift and quadrupolar interaction parameters determined. Black-Right-Pointing-Pointer Full boron assignment based on NMR parameters and response to {sup 19}F decoupling.

  5. Solid-state NMR and Membrane Proteins

    PubMed Central

    Opella, Stanley J.

    2015-01-01

    The native environment for a membrane protein is a phospholipid bilayer. Because the protein is immobilized on NMR timescales by the interactions within a bilayer membrane, solid-state NMR methods are essential to obtain high-resolution spectra. Approaches have been developed for both unoriented and oriented samples, however, they all rest on the foundation of the most fundamental aspects solid-state NMR, and the chemical shift and homo- and hetero-nuclear dipole-dipole interactions. Solid-state NMR has advanced sufficiently to enable the structures of membrane proteins to be determined under near-native conditions in phospholipid bilayers. PMID:25681966

  6. Solid-state NMR and membrane proteins

    NASA Astrophysics Data System (ADS)

    Opella, Stanley J.

    2015-04-01

    The native environment for a membrane protein is a phospholipid bilayer. Because the protein is immobilized on NMR timescales by the interactions within a bilayer membrane, solid-state NMR methods are essential to obtain high-resolution spectra. Approaches have been developed for both unoriented and oriented samples, however, they all rest on the foundation of the most fundamental aspects of solid-state NMR, and the chemical shift and homo- and hetero-nuclear dipole-dipole interactions. Solid-state NMR has advanced sufficiently to enable the structures of membrane proteins to be determined under near-native conditions in phospholipid bilayers.

  7. Scalar operators in solid-state NMR

    SciTech Connect

    Sun, Boqin

    1991-11-01

    Selectivity and resolution of solid-state NMR spectra are determined by dispersion of local magnetic fields originating from relaxation effects and orientation-dependent resonant frequencies of spin nuclei. Theoretically, the orientation-dependent resonant frequencies can be represented by a set of irreducible tensors. Among these tensors, only zero rank tensors (scalar operators) are capable of providing high resolution NMR spectra. This thesis presents a series of new developments in high resolution solid-state NMR concerning the reconstruction of various scalar operators motion in solid C{sub 60} is analyzed.

  8. Solid-state NMR for bacterial biofilms

    NASA Astrophysics Data System (ADS)

    Reichhardt, Courtney; Cegelski, Lynette

    2014-04-01

    Bacteria associate with surfaces and one another by elaborating an extracellular matrix to encapsulate cells, creating communities termed biofilms. Biofilms are beneficial in some ecological niches, but also contribute to the pathogenesis of serious and chronic infectious diseases. New approaches and quantitative measurements are needed to define the composition and architecture of bacterial biofilms to help drive the development of strategies to interfere with biofilm assembly. Solid-state nuclear magnetic resonance (NMR) is uniquely suited to the examination of insoluble and complex macromolecular and whole-cell systems. This article highlights three examples that implement solid-state NMR to deliver insights into bacterial biofilm composition and changes in cell-wall composition as cells transition to the biofilm lifestyle. Most recently, solid-state NMR measurements provided a total accounting of the protein and polysaccharide components in the extracellular matrix of an Escherichia coli biofilm and transformed our qualitative descriptions of matrix composition into chemical parameters that permit quantitative comparisons among samples. We present additional data for whole biofilm samples (cells plus the extracellular matrix) that complement matrix-only analyses. The study of bacterial biofilms by solid-state NMR is an exciting avenue ripe with many opportunities and we close the article by articulating some outstanding questions and future directions in this area.

  9. Solid-state NMR imaging system

    DOEpatents

    Gopalsami, Nachappa; Dieckman, Stephen L.; Ellingson, William A.

    1992-01-01

    An apparatus for use with a solid-state NMR spectrometer includes a special imaging probe with linear, high-field strength gradient fields and high-power broadband RF coils using a back projection method for data acquisition and image reconstruction, and a real-time pulse programmer adaptable for use by a conventional computer for complex high speed pulse sequences.

  10. Solid-state NMR of inorganic semiconductors.

    PubMed

    Yesinowski, James P

    2012-01-01

    Studies of inorganic semiconductors by solid-state NMR vary widely in terms of the nature of the samples investigated, the techniques employed to observe the NMR signal, and the types of information obtained. Compared with the NMR of diamagnetic non-semiconducting substances, important differences often result from the presence of electron or hole carriers that are the hallmark of semiconductors, and whose theoretical interpretation can be involved. This review aims to provide a broad perspective on the topic for the non-expert by providing: (1) a basic introduction to semiconductor physical concepts relevant to NMR, including common crystal structures and the various methods of making samples; (2) discussions of the NMR spin Hamiltonian, details of some of the NMR techniques and strategies used to make measurements and theoretically predict NMR parameters, and examples of how each of the terms in the Hamiltonian has provided useful information in bulk semiconductors; (3) a discussion of the additional considerations needed to interpret the NMR of nanoscale semiconductors, with selected examples. The area of semiconductor NMR is being revitalized by this interest in nanoscale semiconductors, the great improvements in NMR detection sensitivity and resolution that have occurred, and the current interest in optical pumping and spintronics-related studies. Promising directions for future research will be noted throughout.

  11. Lithium Polymer Electrolytes and Solid State NMR

    NASA Technical Reports Server (NTRS)

    Berkeley, Emily R.

    2004-01-01

    Research is being done at the Glenn Research Center (GRC) developing new kinds of batteries that do not depend on a solution. Currently, batteries use liquid electrolytes containing lithium. Problems with the liquid electrolyte are (1) solvents used can leak out of the battery, so larger, more restrictive, packages have to be made, inhibiting the diversity of application and decreasing the power density; (2) the liquid is incompatible with the lithium metal anode, so alternative, less efficient, anodes are required. The Materials Department at GRC has been working to synthesize polymer electrolytes that can replace the liquid electrolytes. The advantages are that polymer electrolytes do not have the potential to leak so they can be used for a variety of tasks, small or large, including in the space rover or in space suits. The polymers generated by Dr. Mary Ann Meador's group are in the form of rod -coil structures. The rod aspect gives the polymer structural integrity, while the coil makes it flexible. Lithium ions are used in these polymers because of their high mobility. The coils have repeating units of oxygen which stabilize the positive lithium by donating electron density. This aids in the movement of the lithium within the polymer, which contributes to higher conductivity. In addition to conductivity testing, these polymers are characterized using DSC, TGA, FTIR, and solid state NMR. Solid state NMR is used in classifying materials that are not soluble in solvents, such as polymers. The NMR spins the sample at a magic angle (54.7') allowing the significant peaks to emerge. Although solid state NMR is a helpful technique in determining bonding, the process of preparing the sample and tuning it properly are intricate jobs that require patience; especially since each run takes about six hours. The NMR allows for the advancement of polymer synthesis by showing if the expected results were achieved. Using the NMR, in addition to looking at polymers, allows for

  12. Lithium Polymer Electrolytes and Solid State NMR

    NASA Technical Reports Server (NTRS)

    Berkeley, Emily R.

    2004-01-01

    Research is being done at the Glenn Research Center (GRC) developing new kinds of batteries that do not depend on a solution. Currently, batteries use liquid electrolytes containing lithium. Problems with the liquid electrolyte are (1) solvents used can leak out of the battery, so larger, more restrictive, packages have to be made, inhibiting the diversity of application and decreasing the power density; (2) the liquid is incompatible with the lithium metal anode, so alternative, less efficient, anodes are required. The Materials Department at GRC has been working to synthesize polymer electrolytes that can replace the liquid electrolytes. The advantages are that polymer electrolytes do not have the potential to leak so they can be used for a variety of tasks, small or large, including in the space rover or in space suits. The polymers generated by Dr. Mary Ann Meador's group are in the form of rod -coil structures. The rod aspect gives the polymer structural integrity, while the coil makes it flexible. Lithium ions are used in these polymers because of their high mobility. The coils have repeating units of oxygen which stabilize the positive lithium by donating electron density. This aids in the movement of the lithium within the polymer, which contributes to higher conductivity. In addition to conductivity testing, these polymers are characterized using DSC, TGA, FTIR, and solid state NMR. Solid state NMR is used in classifying materials that are not soluble in solvents, such as polymers. The NMR spins the sample at a magic angle (54.7') allowing the significant peaks to emerge. Although solid state NMR is a helpful technique in determining bonding, the process of preparing the sample and tuning it properly are intricate jobs that require patience; especially since each run takes about six hours. The NMR allows for the advancement of polymer synthesis by showing if the expected results were achieved. Using the NMR, in addition to looking at polymers, allows for

  13. Advanced solid-state NMR spectroscopy of natural organic matter

    USDA-ARS?s Scientific Manuscript database

    Solid-state NMR is essential for the characterization of natural organic matter (NOM) and is gaining importance in geosciences and environmental sciences. This review is intended to highlight advanced solid-state NMR techniques, especially the systematic approach to NOM characterization, and their ...

  14. Solid-state NMR of proteins sedimented by ultracentrifugation

    PubMed Central

    Bertini, Ivano; Luchinat, Claudio; Parigi, Giacomo; Ravera, Enrico; Reif, Bernd; Turano, Paola

    2011-01-01

    Relatively large proteins in solution, spun in NMR rotors for solid samples at typical ultracentrifugation speeds, sediment at the rotor wall. The sedimented proteins provide high-quality solid-state-like NMR spectra suitable for structural investigation. The proteins fully revert to the native solution state when spinning is stopped, allowing one to study them in both conditions. Transiently sedimented proteins can be considered a novel phase as far as NMR is concerned. NMR of transiently sedimented molecules under fast magic angle spinning has the advantage of overcoming protein size limitations of solution NMR without the need of sample crystallization/precipitation required by solid-state NMR. PMID:21670262

  15. Solid-State NMR Studies of Amyloid Fibril Structure

    NASA Astrophysics Data System (ADS)

    Tycko, Robert

    2011-05-01

    Current interest in amyloid fibrils stems from their involvement in neurodegenerative and other diseases and from their role as an alternative structural state for many peptides and proteins. Solid-state nuclear magnetic resonance (NMR) methods have the unique capability of providing detailed structural constraints for amyloid fibrils, sufficient for the development of full molecular models. In this article, recent progress in the application of solid-state NMR to fibrils associated with Alzheimer's disease, prion fibrils, and related systems is reviewed, along with relevant developments in solid-state NMR techniques and technology.

  16. Solid state NMR characterization of conductive polyanilines

    NASA Astrophysics Data System (ADS)

    Goddard, Yanina Anatolievna

    Different forms of ring deuterated polyaniline with different conductivity have been characterized by solid state deuteron nuclear magnetic resonance. Quadrupole echo (QE) spectra of all forms of polyaniline consist of a superposition of lineshapes for nearly rigid aromatic rings and a small fraction of rings which undergo fast 180° flips. The intensity of the fast flipping component is temperature dependent and different for conductive emeraldine salt (ES) and non-conductive emeraldine base (EB). This is a manifestation of the different structure and morphology of these polymers. Simultaneous measurements of QE lineshapes and the relaxation time anisotropies allowed an accurate description of motion in polyanilines. Slow, small-angle libration in an asymmetric cone provided the best description for the "rigid" fractions of EB and ES. The broadening of deuteron QE lineshapes is consistent with the presence of a distribution of cone angles. Relaxation time measurements also reveal a relatively narrow distribution of librational rates for the EB sample. For ES, the magic angle spinning (MAS) spectra show the existence of two resolved signals with different relaxation rates, which are ascribed to microscopic domains with very different electrical properties. The unexpectedly short relaxation time found for nonconductive domains in ES can be explained by the presence of localized, unpaired electrons. Spin count experiments proved that in highly conductive ES samples, loss of NMR signal intensity occurs not only because of high RF reflectance but also because of irreversible dephasing before signal acquisition due to interactions of nuclear spins with localized unpaired electrons. Deuteron MAS spectra provided unique information about small frequency shifts. Compared to non-conductive EB, conductive emeraldine salts have an additional manifold of spinning sidebands, which is shifted ˜5.8 ppm towards higher frequencies. These shifted sidebands arise from quasi

  17. Solid-state NMR structures of integral membrane proteins.

    PubMed

    Patching, Simon G

    2015-01-01

    Solid-state NMR is unique for its ability to obtain three-dimensional structures and to measure atomic-resolution structural and dynamic information for membrane proteins in native lipid bilayers. An increasing number and complexity of integral membrane protein structures have been determined by solid-state NMR using two main methods. Oriented sample solid-state NMR uses macroscopically aligned lipid bilayers to obtain orientational restraints that define secondary structure and global fold of embedded peptides and proteins and their orientation and topology in lipid bilayers. Magic angle spinning (MAS) solid-state NMR uses unoriented rapidly spinning samples to obtain distance and torsion angle restraints that define tertiary structure and helix packing arrangements. Details of all current protein structures are described, highlighting developments in experimental strategy and other technological advancements. Some structures originate from combining solid- and solution-state NMR information and some have used solid-state NMR to refine X-ray crystal structures. Solid-state NMR has also validated the structures of proteins determined in different membrane mimetics by solution-state NMR and X-ray crystallography and is therefore complementary to other structural biology techniques. By continuing efforts in identifying membrane protein targets and developing expression, isotope labelling and sample preparation strategies, probe technology, NMR experiments, calculation and modelling methods and combination with other techniques, it should be feasible to determine the structures of many more membrane proteins of biological and biomedical importance using solid-state NMR. This will provide three-dimensional structures and atomic-resolution structural information for characterising ligand and drug interactions, dynamics and molecular mechanisms of membrane proteins under physiological lipid bilayer conditions.

  18. Advanced solid-state NMR spectroscopy of natural organic matter.

    PubMed

    Mao, Jingdong; Cao, Xiaoyan; Olk, Dan C; Chu, Wenying; Schmidt-Rohr, Klaus

    2017-05-01

    Solid-state NMR is essential for the characterization of natural organic matter (NOM) and is gaining importance in geosciences and environmental sciences. This review is intended to highlight advanced solid-state NMR techniques, especially a systematic approach to NOM characterization, and their applications to the study of NOM. We discuss some basics of how to acquire high-quality and quantitative solid-state (13)C NMR spectra, and address some common technical mistakes that lead to unreliable spectra of NOM. The identification of specific functional groups in NOM, primarily based on (13)C spectral-editing techniques, is described and the theoretical background of some recently-developed spectral-editing techniques is provided. Applications of solid-state NMR to investigating nitrogen (N) in NOM are described, focusing on limitations of the widely used (15)N CP/MAS experiment and the potential of improved advanced NMR techniques for characterizing N forms in NOM. Then techniques used for identifying proximities, heterogeneities and domains are reviewed, and some examples provided. In addition, NMR techniques for studying segmental dynamics in NOM are reviewed. We also briefly discuss applications of solid-state NMR to NOM from various sources, including soil organic matter, aquatic organic matter, organic matter in atmospheric particulate matter, carbonaceous meteoritic organic matter, and fossil fuels. Finally, examples of NMR-based structural models and an outlook are provided. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Functional groups identified by solid state 13C NMR spectroscopy

    USDA-ARS?s Scientific Manuscript database

    Animal manure is generally high in organic matter intensity so it is well suitable for 13C nuclear magnetic resonance (NMR) analysis. Solid-state 13C NMR techniques used in characterizing organic matter and its components include, but are not limited to, cross-polarization /magic angle spinning (CP...

  20. Solid State NMR and Protein-Protein Interactions in Membranes

    PubMed Central

    Miao, Yimin; Cross, Timothy A.

    2013-01-01

    Solid state NMR spectroscopy has evolved rapidly in recent years into an excellent tool for the characterization of membrane proteins and their complexes. In the past few years it has also become clear that the structure of membrane proteins, especially helical membrane proteins is determined, in part, by the membrane environment. Therefore, the modeling of this environment by a liquid crystalline lipid bilayer for solid state NMR has generated a unique tool for the characterization of native conformational states, local and global dynamics, and high resolution structure for these proteins. Protein-protein interactions can also benefit from this solid state NMR capability to characterize membrane proteins in a native-like environment. These complexes take the form of oligomeric structures and hetero-protein interactions both with water soluble proteins and other membrane proteins. PMID:24034903

  1. The development of solid-state NMR of membrane proteins.

    PubMed

    Opella, Stanley J

    Most biological functions are carried out in supramolecular assemblies. As a result of their slow reorientation in solution, these assemblies have been resistant to the widely employed solution NMR approaches. The development of solid-state NMR to first of all overcome the correlation time problem and then obtain informative high-resolution spectra of proteins in supramolecular assemblies, such as virus particles and membranes, is described here. High resolution solid-state NMR is deeply intertwined with the history of NMR, and the seminal paper was published in 1948. Although the general principles were understood by the end of the 1950s, it has taken more than fifty years for instrumentation and experimental methods to become equal to the technical problems presented by the biological assemblies of greatest interest. It is now possible to obtain atomic resolution structures of viral coat proteins in virus particles and membrane proteins in phospholipid bilayers by oriented sample solid-state NMR methods. The development of this aspect of the field of solid-state NMR is summarized in this review article.

  2. The development of solid-state NMR of membrane proteins

    PubMed Central

    Opella, Stanley J.

    2014-01-01

    Most biological functions are carried out in supramolecular assemblies. As a result of their slow reorientation in solution, these assemblies have been resistant to the widely employed solution NMR approaches. The development of solid-state NMR to first of all overcome the correlation time problem and then obtain informative high-resolution spectra of proteins in supramolecular assemblies, such as virus particles and membranes, is described here. High resolution solid-state NMR is deeply intertwined with the history of NMR, and the seminal paper was published in 1948. Although the general principles were understood by the end of the 1950s, it has taken more than fifty years for instrumentation and experimental methods to become equal to the technical problems presented by the biological assemblies of greatest interest. It is now possible to obtain atomic resolution structures of viral coat proteins in virus particles and membrane proteins in phospholipid bilayers by oriented sample solid-state NMR methods. The development of this aspect of the field of solid-state NMR is summarized in this review article. PMID:26069880

  3. Applications of solid-state NMR to membrane proteins.

    PubMed

    Ladizhansky, Vladimir

    2017-07-12

    Membrane proteins mediate flow of molecules, signals, and energy between cells and intracellular compartments. Understanding membrane protein function requires a detailed understanding of the structural and dynamic properties involved. Lipid bilayers provide a native-like environment for structure-function investigations of membrane proteins. In this review we give a general discourse on the recent progress in the field of solid-state NMR of membrane proteins. Solid-state NMR is a variation of NMR spectroscopy that is applicable to molecular systems with restricted mobility, such as high molecular weight proteins and protein complexes, supramolecular assemblies, or membrane proteins in a phospholipid environment. We highlight recent advances in applications of solid-state NMR to membrane proteins, specifically focusing on the recent developments in the field of Dynamic Nuclear Polarization, proton detection, and solid-state NMR applications in situ (in cell membranes). This article is part of a Special Issue entitled: Biophysics in Canada, edited by Lewis Kay, John Baenziger, Albert Berghuis and Peter Tieleman. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Diamond Deposition and Defect Chemistry Studied via Solid State NMR

    DTIC Science & Technology

    1994-06-30

    same integrated NMR signal, regardless of its chemical environment, provided complete spin-lattice relaxation occurs between averages 3 . Gem -quality...occurs between averages, and broadening from years, a large research effort has been devoted to the study paramagnetic centers is insignificant. Gem ...information on the distribution and motion mond’s durability very attractive. However, while gem - of hydrogen can be obtained from the solid-state NMR

  5. Solid-State NMR Spectroscopy for the Physical Chemistry Laboratory

    ERIC Educational Resources Information Center

    Kinnun, Jacob J.; Leftin, Avigdor; Brown, Michael F.

    2013-01-01

    Solid-state nuclear magnetic resonance (NMR) spectroscopy finds growing application to inorganic and organic materials, biological samples, polymers, proteins, and cellular membranes. However, this technique is often neither included in laboratory curricula nor typically covered in undergraduate courses. On the other hand, spectroscopy and…

  6. Solid-State NMR Spectroscopy for the Physical Chemistry Laboratory

    ERIC Educational Resources Information Center

    Kinnun, Jacob J.; Leftin, Avigdor; Brown, Michael F.

    2013-01-01

    Solid-state nuclear magnetic resonance (NMR) spectroscopy finds growing application to inorganic and organic materials, biological samples, polymers, proteins, and cellular membranes. However, this technique is often neither included in laboratory curricula nor typically covered in undergraduate courses. On the other hand, spectroscopy and…

  7. DFT calculations of quadrupolar solid-state NMR properties: Some examples in solid-state inorganic chemistry.

    PubMed

    Cuny, Jerome; Messaoudi, Sabri; Alonzo, Veronique; Furet, Eric; Halet, Jean-François; Le Fur, Eric; Ashbrook, Sharon E; Pickard, Chris J; Gautier, Regis; Le Polles, Laurent

    2008-10-01

    This article presents results of first-principles calculations of quadrupolar parameters measured by solid-state nuclear magnetic measurement (NMR) spectroscopy. Different computational methods based on density functional theory were used to calculate the quadrupolar parameters. Through a series of illustrations from different areas of solid state inorganic chemistry, it is shown how quadrupolar solid-state NMR properties can be tackled by a theoretical approach and can yield structural information.

  8. 15N chemical shift referencing in solid state NMR.

    PubMed

    Bertani, Philippe; Raya, Jésus; Bechinger, Burkhard

    2014-01-01

    Solid-state NMR spectroscopy has much advanced during the last decade and provides a multitude of data that can be used for high-resolution structure determination of biomolecules, polymers, inorganic compounds or macromolecules. In some cases the chemical shift referencing has become a limiting factor to the precision of the structure calculations and we have therefore evaluated a number of methods used in proton-decoupled (15)N solid-state NMR spectroscopy. For (13)C solid-state NMR spectroscopy adamantane is generally accepted as an external standard, but to calibrate the (15)N chemical shift scale several standards are in use. As a consequence the published chemical shift values exhibit considerable differences (up to 22 ppm). In this paper we report the (15)N chemical shift of several commonly used references compounds in order to allow for comparison and recalibration of published data and future work. We show that (15)NH4Cl in its powdered form (at 39.3 ppm with respect to liquid NH3) is a suitable external reference as it produces narrow lines when compared to other reference compounds and at the same time allows for the set-up of cross-polarization NMR experiments. The compound is suitable to calibrate magic angle spinning and static NMR experiments. Finally the temperature variation of (15)NH4Cl chemical shift is reported.

  9. Advances in solid-state NMR of cellulose.

    PubMed

    Foston, Marcus

    2014-06-01

    Nuclear magnetic resonance (NMR) spectroscopy is a well-established analytical and enabling technology in biofuel research. Over the past few decades, lignocellulosic biomass and its conversion to supplement or displace non-renewable feedstocks has attracted increasing interest. The application of solid-state NMR spectroscopy has long been seen as an important tool in the study of cellulose and lignocellulose structure, biosynthesis, and deconstruction, especially considering the limited number of effective solvent systems and the significance of plant cell wall three-dimensional microstructure and component interaction to conversion yield and rate profiles. This article reviews common and recent applications of solid-state NMR spectroscopy methods that provide insight into the structural and dynamic processes of cellulose that control bulk properties and biofuel conversion.

  10. Structural biology applications of solid state MAS DNP NMR

    NASA Astrophysics Data System (ADS)

    Akbey, Ümit; Oschkinat, Hartmut

    2016-08-01

    Dynamic Nuclear Polarization (DNP) has long been an aim for increasing sensitivity of nuclear magnetic resonance (NMR) spectroscopy, delivering spectra in shorter experiment times or of smaller sample amounts. In recent years, it has been applied in magic angle spinning (MAS) solid-state NMR to a large range of samples, including biological macromolecules and functional materials. New research directions in structural biology can be envisaged by DNP, facilitating investigations on very large complexes or very heterogeneous samples. Here we present a summary of state of the art DNP MAS NMR spectroscopy and its applications to structural biology, discussing the technical challenges and factors affecting DNP performance.

  11. Solid state NMR of porous materials : zeolites and related materials.

    PubMed

    Koller, Hubert; Weiss, Mark

    2012-01-01

    Solid state NMR spectroscopy applied to the science of crystalline micro- and mesoporous silica materials over the past 10 years is reviewed. A survey is provided of framework structure and connectivity analyses from chemical shift effects of various elements in zeolites including heteroatom substitutions, framework defects and pentacoordinated silicon for zeolites containing fluoride ions. New developments in the field of NMR crystallography are included. Spatial host-guest ordering and confinement effects of zeolite-sorbate complexes are outlined, with special emphasis on NMR applications utilizing the heteronuclear dipolar interaction. The characterization of zeolite acid sites and in situ NMR on catalytic conversions is also included. Finally, the motion of extra-framework cations is investigated in two tutorial cases of sodium hopping in sodalite and cancrinite.

  12. Investigating albendazole desmotropes by solid-state NMR spectroscopy.

    PubMed

    Chattah, Ana K; Zhang, Rongchun; Mroue, Kamal H; Pfund, Laura Y; Longhi, Marcela R; Ramamoorthy, Ayyalusamy; Garnero, Claudia

    2015-03-02

    Characterization of the molecular structure and physicochemical solid-state properties of the solid forms of pharmaceutical compounds is a key requirement for successful commercialization as potential active ingredients in drug products. These properties can ultimately have a critical effect on the solubility and bioavailability of the final drug product. Here, the desmotropy of Albendazole forms I and II was investigated at the atomic level. Ultrafast magic angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) spectroscopy, together with powder X-ray diffraction, thermal analysis, and Fourier transform infrared spectroscopy, were performed on polycrystalline samples of the two solids in order to fully characterize and distinguish the two forms. High-resolution one-dimensional (1)H, (13)C, and (15)N together with two-dimensional (1)H/(1)H single quantum-single quantum, (1)H/(1)H single quantum-double quantum, and (1)H/(13)C chemical shift correlation solid-state NMR experiments under MAS conditions were extensively used to decipher the intramolecular and intermolecular hydrogen bonding interactions present in both solid forms. These experiments enabled the unequivocal identification of the tautomers of each desmotrope. Our results also revealed that both solid forms may be described as dimeric structures, with different intermolecular hydrogen bonds connecting the tautomers in each dimer.

  13. Protein structure determination with paramagnetic solid-state NMR spectroscopy.

    PubMed

    Sengupta, Ishita; Nadaud, Philippe S; Jaroniec, Christopher P

    2013-09-17

    Many structures of the proteins and protein assemblies that play central roles in fundamental biological processes and disease pathogenesis are not readily accessible via the conventional techniques of single-crystal X-ray diffraction and solution-state nuclear magnetic resonance (NMR). On the other hand, many of these challenging biological systems are suitable targets for atomic-level structural and dynamic analysis by magic-angle spinning (MAS) solid-state NMR spectroscopy, a technique that has far less stringent limitations on the molecular size and crystalline state. Over the past decade, major advances in instrumentation and methodology have prompted rapid growth in the field of biological solid-state NMR. However, despite this progress, one challenge for the elucidation of three-dimensional (3D) protein structures via conventional MAS NMR methods is the relative lack of long-distance data. Specifically, extracting unambiguous interatomic distance restraints larger than ∼5 Å from through-space magnetic dipole-dipole couplings among the protein (1)H, (13)C, and (15)N nuclei has proven to be a considerable challenge for researchers. It is possible to circumvent this problem by extending the structural studies to include several analogs of the protein of interest, intentionally modified to contain covalently attached paramagnetic tags at selected sites. In these paramagnetic proteins, the hyperfine couplings between the nuclei and unpaired electrons can manifest themselves in NMR spectra in the form of relaxation enhancements of the nuclear spins that depend on the electron-nucleus distance. These effects can be significant for nuclei located up to ∼20 Å away from the paramagnetic center. In this Account, we discuss MAS NMR structural studies of nitroxide and EDTA-Cu(2+) labeled variants of a model 56 amino acid globular protein, B1 immunoglobulin-binding domain of protein G (GB1), in the microcrystalline solid phase. We used a set of six EDTA-Cu(2

  14. Structural biology applications of solid state MAS DNP NMR.

    PubMed

    Akbey, Ümit; Oschkinat, Hartmut

    2016-08-01

    Dynamic Nuclear Polarization (DNP) has long been an aim for increasing sensitivity of nuclear magnetic resonance (NMR) spectroscopy, delivering spectra in shorter experiment times or of smaller sample amounts. In recent years, it has been applied in magic angle spinning (MAS) solid-state NMR to a large range of samples, including biological macromolecules and functional materials. New research directions in structural biology can be envisaged by DNP, facilitating investigations on very large complexes or very heterogeneous samples. Here we present a summary of state of the art DNP MAS NMR spectroscopy and its applications to structural biology, discussing the technical challenges and factors affecting DNP performance. Copyright © 2016 Elsevier Inc. All rights reserved.

  15. Microcoils and microsamples in solid-state NMR.

    PubMed

    Takeda, Kazuyuki

    2012-01-01

    Recent reports on microcoils are reviewed. The first part of the review includes a discussion of how the geometries of the sample and coil affect the NMR signal intensity. In addition to derivation of the well-known result that the signal intensity increases as the coil size decreases, the prediction that dilution of a small sample with magnetically inert matter leads to better sensitivity if a tiny coil is not available is given. The second part of the review focuses on the issues specific to solid-state NMR. They include realization of magic-angle spinning (MAS) using a microcoil and harnessing of such strong pulses that are feasible only with a microcoil. Two strategies for microcoil MAS, the piggyback method and magic-angle coil spinning (MACS), are reviewed. In addition, MAS of flat, disk-shaped samples is discussed in the context of solid-state NMR of small-volume samples. Strong RF irradiation, which has been exploited in wide-line spectral excitation, multiple-quantum MAS (MQMAS), and dipolar decoupling experiments, has been accompanied by new challenges regarding the Bloch-Siegert effect, the minimum time resolution of the spectrometer, and the time scale of pulse transient effects. For a possible solution to the latter problem, recent reports on active compensation of pulse transients are described.

  16. Solvent suppression in DNP enhanced solid state NMR

    NASA Astrophysics Data System (ADS)

    Yarava, Jayasubba Reddy; Chaudhari, Sachin Rama; Rossini, Aaron J.; Lesage, Anne; Emsley, Lyndon

    2017-04-01

    We show how DNP enhanced solid-state NMR spectra can be dramatically simplified by suppression of solvent signals. This is achieved by (i) exploiting the paramagnetic relaxation enhancement of solvent signals relative to materials substrates, or (ii) by using short cross-polarization contact times to transfer hyperpolarization to only directly bonded carbon-13 nuclei in frozen solutions. The methods are evaluated for organic microcrystals, surfaces and frozen solutions. We show how this allows for the acquisition of high-resolution DNP enhanced proton-proton correlation experiments to measure inter-nuclear proximities in an organic solid.

  17. A Hall effect angle detector for solid-state NMR.

    PubMed

    Mamone, Salvatore; Dorsch, André; Johannessen, Ole G; Naik, Manoj V; Madhu, P K; Levitt, Malcolm H

    2008-01-01

    We describe a new method for independent monitoring of the angle between the spinning axis and the magnetic field in solid-state NMR. A Hall effect magnetic flux sensor is fixed to the spinning housing, so that a change in the stator orientation leads to a change in the angle between the Hall plane and the static magnetic field. This leads to a change in the Hall voltage generated by the sensor when an electric current is passed through it. The Hall voltage may be measured externally by a precision voltmeter, allowing the spinning angle to be measured non-mechanically and independent of the NMR experiment. If the Hall sensor is mounted so that the magnetic field is approximately parallel to the Hall plane, the Hall voltage becomes highly sensitive to the stator orientation. The current angular accuracy is around 10 millidegrees. The precautions needed to achieve higher angular accuracy are described.

  18. Solid-state NMR relaxation studies of Australian spider silks.

    PubMed

    Kishore, A I; Herberstein, M E; Craig, C L; Separovic, F

    Solid-state NMR techniques were used to study two different types of spider silk from two Australian orb-web spider species, Nephila edulis and Argiope keyserlingi. A comparison of (13)C-T(1) and (1)H-T(1rho) solid-state NMR relaxation data of the Ala Calpha, Ala Cbeta, Gly Calpha, and carbonyl resonances revealed subtle differences between dragline and cocoon silk. (13)C-T(1rho) and (1)H-T(1) relaxation experiments showed significant differences between silks of the two species with possible structural variations. Comparison of our data to previous (13)C-T(1) relaxation studies of silk from Nephila clavipes (A. Simmons et al., Macromolecules, 1994, Vol. 27, pp. 5235-5237) also supports the finding that differences in molecular mobility of dragline silk exist between species. Interspecies differences in silk structure may be due to different functional properties. Relaxation studies performed on wet (supercontracted) and dry silks showed that the degree of hydration affects relaxation properties, and hence changes in molecular mobility are correlated with functional properties of silk. Copyright 2002 Wiley Periodicals, Inc.

  19. Solid-state NMR characterization of Mowry Formation shales

    SciTech Connect

    Miknis, F.P.

    1992-04-01

    Solid-state {sup 13}C and {sup 29}Si NMR measurements were carried out on a series of petroleum source rocks from the Mowry Formation of the Powder River Basin in Wyoming. The objectives of this study wereto use CP/MAS {sup 13}C NMR measurements to monitor changes in the carbon structure of the kerogen that result from depth of burial, and to examine the feasibility of {sup 29}Si NMR for studying the thermal alteration of clay minerals during diagenesis. Carbon and silicon NMR measurements were made on a suite of samples covering a present-day depth interval of 3,000 to 11,500 ft.In general, the NMR results endorsed other geochemical analyses that were performed on the source rocks as part of another study to examine pressure compartmentalization in the Mowry Formation. The carbon aromaticity of the kerogen increased with depth of burial, and at depths greater that approximately 10,000 ft the kerogen showed little capacity to generate additional oil because of the small fraction of residual aliphatic carbon. By combining NMR and Rock-Eval measurements, an estimate of the hydrogen budget was obtained. The calculations indicated that approximately 20% of the kerogen was converted to hydrocarbons, and that sufficient hydrogen was liberated from aromatization and condensation reactions to stabilize the generated products. The {sup 29}Si NMR spectra were characterized by a relatively sharp quartz resonance and a broad resonance from the clay minerals. With increasing depth of burial, the clay resonance became broader and shifted slightly downfield. These changes qualitatively support X-ray analysis that shows progressive alteration of illite to smectite with depth of burial.

  20. Solid-state NMR characterization of Mowry Formation shales

    SciTech Connect

    Miknis, F.P.

    1992-04-01

    Solid-state [sup 13]C and [sup 29]Si NMR measurements were carried out on a series of petroleum source rocks from the Mowry Formation of the Powder River Basin in Wyoming. The objectives of this study wereto use CP/MAS [sup 13]C NMR measurements to monitor changes in the carbon structure of the kerogen that result from depth of burial, and to examine the feasibility of [sup 29]Si NMR for studying the thermal alteration of clay minerals during diagenesis. Carbon and silicon NMR measurements were made on a suite of samples covering a present-day depth interval of 3,000 to 11,500 ft.In general, the NMR results endorsed other geochemical analyses that were performed on the source rocks as part of another study to examine pressure compartmentalization in the Mowry Formation. The carbon aromaticity of the kerogen increased with depth of burial, and at depths greater that approximately 10,000 ft the kerogen showed little capacity to generate additional oil because of the small fraction of residual aliphatic carbon. By combining NMR and Rock-Eval measurements, an estimate of the hydrogen budget was obtained. The calculations indicated that approximately 20% of the kerogen was converted to hydrocarbons, and that sufficient hydrogen was liberated from aromatization and condensation reactions to stabilize the generated products. The [sup 29]Si NMR spectra were characterized by a relatively sharp quartz resonance and a broad resonance from the clay minerals. With increasing depth of burial, the clay resonance became broader and shifted slightly downfield. These changes qualitatively support X-ray analysis that shows progressive alteration of illite to smectite with depth of burial.

  1. Solid State NMR Studies of the Aluminum Hydride Phases

    NASA Technical Reports Server (NTRS)

    Hwang, Son-Jong; Bowman, R. C., Jr.; Graetz, Jason; Reilly, J. J.

    2006-01-01

    Several solid state NMR techniques including magic-angle-spinning (MAS) and multiple-quantum (MQ) MAS experiments have been used to characterize various AlH3 samples. MAS-NMR spectra for the 1H and 27Al nuclei have been obtained on a variety of AlH3 samples that include the (beta)- and (gamma)- phases as well as the most stable (alpha)-phase. While the dominant components in these NMR spectra correspond to the aluminum hydride phases, other species were found that include Al metal, molecular hydrogen (H2), as well as peaks that can be assigned to Al-O species in different configurations. The occurrence and concentration of these extraneous components are dependent upon the initial AlH3 phase composition and preparation procedures. Both the (beta)-AlH3 and (gamma)-AlH3 phases were found to generate substantial amounts of Al metal when the materials were stored at room temperature while the (alpha)-phase materials do not exhibit these changes.

  2. Solid State NMR Studies of the Aluminum Hydride Phases

    NASA Technical Reports Server (NTRS)

    Hwang, Son-Jong; Bowman, R. C., Jr.; Graetz, Jason; Reilly, J. J.

    2006-01-01

    Several solid state NMR techniques including magic-angle-spinning (MAS) and multiple-quantum (MQ) MAS experiments have been used to characterize various AlH3 samples. MAS-NMR spectra for the 1H and 27Al nuclei have been obtained on a variety of AlH3 samples that include the (beta)- and (gamma)- phases as well as the most stable (alpha)-phase. While the dominant components in these NMR spectra correspond to the aluminum hydride phases, other species were found that include Al metal, molecular hydrogen (H2), as well as peaks that can be assigned to Al-O species in different configurations. The occurrence and concentration of these extraneous components are dependent upon the initial AlH3 phase composition and preparation procedures. Both the (beta)-AlH3 and (gamma)-AlH3 phases were found to generate substantial amounts of Al metal when the materials were stored at room temperature while the (alpha)-phase materials do not exhibit these changes.

  3. Experimental aspects of multidimensional solid-state NMR correlation spectroscopy.

    PubMed

    Ramamoorthy, A; Wu, C H; Opella, S J

    1999-09-01

    The experimental parameters critical for the implementation of multidimensional solid-state NMR experiments that incorporate heteronuclear spin exchange at the magic angle are discussed. This family of experiments is exemplified by the three-dimensional experiment that correlates the (1)H chemical shift, (1)H-(15)N dipolar coupling, and (15)N chemical shift frequencies. The broadening effects of the homonuclear (1)H-(1)H dipolar couplings are suppressed using flip-flop (phase- and frequency-switched) Lee-Goldburg irradiations in both the (1)H chemical shift and the (1)H-(15)N dipolar coupling dimensions. The experiments are illustrated using the (1)H and (15)N chemical shift and dipolar couplings in a single crystal of (15)N-acetylleucine. Copyright 1999 Academic Press.

  4. Mechanism of Solid-State Thermolysis of Ammonia Boraine: 15N NMR Study Using Fast Magic-Angle Spinning and Dynamic Nuclear Polarization

    SciTech Connect

    Kobayashi, Takeshi; Gupta, Shalabh; Caporini, Marc A; Pecharsky, Vitalij K; Pruski, Marek

    2014-08-28

    The solid-state thermolysis of ammonia borane (NH3BH3, AB) was explored using state-of-the-art 15N solid-state NMR spectroscopy, including 2D indirectly detected 1H{15N} heteronuclear correlation and dynamic nuclear polarization (DNP)-enhanced 15N{1H} cross-polarization experiments as well as 11B NMR. The complementary use of 15N and 11B NMR experiments, supported by density functional theory calculations of the chemical shift tensors, provided insights into the dehydrogenation mechanism of AB—insights that have not been available by 11B NMR alone. Specifically, highly branched polyaminoborane derivatives were shown to form from AB via oligomerization in the “head-to-tail” manner, which then transform directly into hexagonal boron nitride analog through the dehydrocyclization reaction, bypassing the formation of polyiminoborane.

  5. A Solid-State NMR Investigation of MQ Silicone Copolymers.

    PubMed

    Vasil'ev, Sergey G; Volkov, Vitaly I; Tatarinova, Elena A; Muzafarov, Aziz M

    2013-01-01

    The structure of MQ copolymers of the general chemical formula [(CH3)3SiO0.5]m [SiO2]n was characterized by means of solid-state magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The MQ copolymers are highly branched polycyclic compounds (densely cross-linked nanosized networks). MQ copolymers were prepared by hydrolytic polycondensation in active medium. (29)Si NMR spectra were obtained by single pulse excitation (or direct polarization, DP) and cross-polarization (CP) (29)Si{(1)H} techniques in concert with MAS. It was shown that material consist of monofunctional M (≡SiO Si (CH3)3) and two types of tetrafunctional Q units: Q(4) ((≡SiO)4Si) and Q(3) ((≡SiO)3SiOH). Spin-lattice relaxation times T1 measurements of (29)Si nuclei and analysis of (29)Si{(1)H} variable contact time signal intensities allowed us to obtain quantitative data on the relative content of different sites in copolymers. These investigations indicate that MQ copolymers represent dense structure with core and shell.

  6. The determination of enantiomeric excess of valine by ODESSA solid-state NMR experiment.

    PubMed

    Tadeusiak, Elzbieta J; Ciesielski, Włodzimierz; Olejniczak, Sebastian

    2006-10-01

    The enantiomeric excess (ee) can be determined by many methods; one among them is nuclear magnetic resonance in solid-state (SS NMR). In this study we used the SS NMR ODESSA experiment for determination of the ee of valine.

  7. An extrapolation scheme for solid-state NMR chemical shift calculations

    NASA Astrophysics Data System (ADS)

    Nakajima, Takahito

    2017-06-01

    Conventional quantum chemical and solid-state physical approaches include several problems to accurately calculate solid-state nuclear magnetic resonance (NMR) properties. We propose a reliable computational scheme for solid-state NMR chemical shifts using an extrapolation scheme that retains the advantages of these approaches but reduces their disadvantages. Our scheme can satisfactorily yield solid-state NMR magnetic shielding constants. The estimated values have only a small dependence on the low-level density functional theory calculation with the extrapolation scheme. Thus, our approach is efficient because the rough calculation can be performed in the extrapolation scheme.

  8. (1)H NMR spectra dataset and solid-state NMR data of cowpea (Vigna unguiculata).

    PubMed

    Alves Filho, Elenilson G; Silva, Lorena M A; Teofilo, Elizita M; Larsen, Flemming H; de Brito, Edy S

    2017-04-01

    In this article the NMR data from chemical shifts, coupling constants, and structures of all the characterized compounds were provided, beyond a complementary PCA evaluation for the corresponding manuscript (E.G. Alves Filho, L.M.A. Silva, E.M. Teofilo, F.H. Larsen, E.S. de Brito, 2017) [3]. In addition, a complementary assessment from solid-state NMR data was provided. For further chemometric analysis, numerical matrices from the raw (1)H NMR data were made available in Microsoft Excel workbook format (.xls).

  9. integrating Solid State NMR and Computations in Membrane Protein Science

    NASA Astrophysics Data System (ADS)

    Cross, Timothy

    2015-03-01

    Helical membrane protein structures are influenced by their native environment. Therefore the characterization of their structure in an environment that models as closely as possible their native environment is critical for achieving not only structural but functional understanding of these proteins. Solid state NMR spectroscopy in liquid crystalline lipid bilayers provides an excellent tool for such characterizations. Two classes of restraints can be obtained - absolute restraints that constrain the structure to a laboratory frame of reference when using uniformly oriented samples (approximately 1° of mosaic spread) and relative restraints that restrain one part of the structure with respect to another part such as torsional and distance restraints. Here, I will discuss unique restraints derived from uniformly oriented samples and the characterization of initial structures utilizing both restraint types, followed by restrained molecular dynamics refinement in the same lipid bilayer environment as that used for the experimental restraint collection. Protein examples will be taken from Influenza virus and Mycobacterium tuberculosis. When available comparisons of structures to those obtained using different membrane mimetic environments will be shown and the causes for structural distortions explained based on an understanding of membrane biophysics and its sophisticated influence on membrane proteins.

  10. Multidimensional solid-state NMR spectroscopy of plant cell walls.

    PubMed

    Wang, Tuo; Phyo, Pyae; Hong, Mei

    2016-09-01

    Plant biomass has become an important source of bio-renewable energy in modern society. The molecular structure of plant cell walls is difficult to characterize by most atomic-resolution techniques due to the insoluble and disordered nature of the cell wall. Solid-state NMR (SSNMR) spectroscopy is uniquely suited for studying native hydrated plant cell walls at the molecular level with chemical resolution. Significant progress has been made in the last five years to elucidate the molecular structures and interactions of cellulose and matrix polysaccharides in plant cell walls. These studies have focused on primary cell walls of growing plants in both the dicotyledonous and grass families, as represented by the model plants Arabidopsis thaliana, Brachypodium distachyon, and Zea mays. To date, these SSNMR results have shown that 1) cellulose, hemicellulose, and pectins form a single network in the primary cell wall; 2) in dicot cell walls, the protein expansin targets the hemicellulose-enriched region of the cellulose microfibril for its wall-loosening function; and 3) primary wall cellulose has polymorphic structures that are distinct from the microbial cellulose structures. This article summarizes these key findings, and points out future directions of investigation to advance our fundamental understanding of plant cell wall structure and function.

  11. Coherent and stochastic averaging in solid-state NMR.

    PubMed

    Nevzorov, Alexander A

    2014-12-01

    A new approach for calculating solid-state NMR lineshapes of uniaxially rotating membrane proteins under the magic-angle spinning conditions is presented. The use of stochastic Liouville equation (SLE) allows one to account for both coherent sample rotation and stochastic motional averaging of the spherical dipolar powder patterns by uniaxial diffusion of the spin-bearing molecules. The method is illustrated via simulations of the dipolar powder patterns of rigid samples under the MAS conditions, as well as the recent method of rotational alignment in the presence of both MAS and rotational diffusion under the conditions of dipolar recoupling. It has been found that it is computationally more advantageous to employ direct integration over a spherical grid rather than to use a full angular basis set for the SLE solution. Accuracy estimates for the bond angles measured from the recoupled amide (1)H-(15)N dipolar powder patterns have been obtained at various rotational diffusion coefficients. It has been shown that the rotational alignment method is applicable to membrane proteins approximated as cylinders with radii of approximately 20Å, for which uniaxial rotational diffusion within the bilayer is sufficiently fast and exceeds the rate 2×10(5)s(-1). Copyright © 2014 Elsevier Inc. All rights reserved.

  12. Coherent and stochastic averaging in solid-state NMR

    NASA Astrophysics Data System (ADS)

    Nevzorov, Alexander A.

    2014-12-01

    A new approach for calculating solid-state NMR lineshapes of uniaxially rotating membrane proteins under the magic-angle spinning conditions is presented. The use of stochastic Liouville equation (SLE) allows one to account for both coherent sample rotation and stochastic motional averaging of the spherical dipolar powder patterns by uniaxial diffusion of the spin-bearing molecules. The method is illustrated via simulations of the dipolar powder patterns of rigid samples under the MAS conditions, as well as the recent method of rotational alignment in the presence of both MAS and rotational diffusion under the conditions of dipolar recoupling. It has been found that it is computationally more advantageous to employ direct integration over a spherical grid rather than to use a full angular basis set for the SLE solution. Accuracy estimates for the bond angles measured from the recoupled amide 1H-15N dipolar powder patterns have been obtained at various rotational diffusion coefficients. It has been shown that the rotational alignment method is applicable to membrane proteins approximated as cylinders with radii of approximately 20 Å, for which uniaxial rotational diffusion within the bilayer is sufficiently fast and exceeds the rate 2 × 105 s-1.

  13. Sensitivity Enhancement in Static Solid-State NMR Experiments VIA Single and Multiple Quantum Dipolar Coherences

    PubMed Central

    Gopinath, T.; Veglia, Gianluigi

    2012-01-01

    We present a new method to enhance the sensitivity in static solid-state NMR for a gain in signal-to-noise ratio up to 40%. This sensitivity enhancement is different from the corresponding solution NMR sensitivity enhancement schemes and is achieved by combining single and multiple quantum dipolar coherences. While this new approach is demonstrated for the PISEMA (polarization inversion spin exchange at magic angle) experiment, it can be generalized to the other separated local field experiments for solid-state NMR spectroscopy. This method will have a direct impact on solid-state NMR spectroscopy of liquid crystals as well as membrane proteins aligned in lipid membranes. PMID:19351170

  14. Arabidopsis thalianafrom Polarization Transfer Solid-State NMR

    SciTech Connect

    White, Paul B; Wang, Tuo; Park, Yong Bum; Cosgrove, Daniel J; Hong, Mei

    2014-07-23

    Polysaccharide-rich plant cell walls are hydrated under functional conditions, but the molecular interactions between water and polysaccharides in the wall have not been investigated. In this work, we employ polarization transfer solid-state NMR techniques to study the hydration of primary-wall polysaccharides of the model plant, Arabidopsis thaliana. By transferring water 1H polarization to polysaccharides through distance- and mobility-dependent 1H–1H dipolar couplings and detecting it through polysaccharide 13C signals, we obtain information about water proximity to cellulose, hemicellulose, and pectins as well as water mobility. Both intact and partially extracted cell wall samples are studied. Our results show that water–pectin polarization transfer is much faster than water–cellulose polarization transfer in all samples, but the extent of extraction has a profound impact on the water–polysaccharide spin diffusion. Removal of calcium ions and the consequent extraction of homogalacturonan (HG) significantly slowed down spin diffusion, while further extraction of matrix polysaccharides restored the spin diffusion rate. These trends are observed in cell walls with similar water content, thus they reflect inherent differences in the mobility and spatial distribution of water. Combined with quantitative analysis of the polysaccharide contents, our results indicate that calcium ions and HG gelation increase the amount of bound water, which facilitates spin diffusion, while calcium removal disrupts the gel and gives rise to highly dynamic water, which slows down spin diffusion. The recovery of spin diffusion rates after more extensive extraction is attributed to increased water-exposed surface areas of the polysaccharides. Water–pectin spin diffusion precedes water–cellulose spin diffusion, lending support to the single-network model of plant primary walls in which a substantial fraction of the cellulose surface is surrounded by pectins.

  15. Sampling Scheme and Compressed Sensing Applied to Solid-State NMR Spectroscopy

    PubMed Central

    Lin, Eugene C.; Opella, Stanley J.

    2013-01-01

    We describe the incorporation of non-uniform sampling (NUS) compressed sensing (CS) into Oriented Sample (OS) Solid-state NMR for stationary aligned samples and Magic Angle Spinning (MAS) Solid-state NMR for unoriented ‘powder’ samples Both simulated and experimental results indicate that 25% to 33% of a full linearly sampled data set is required to reconstruct two-and three-dimensional solid-state NMR spectra with high fidelity. A modest increase in signal-to-noise ratio is accompanies the reconstruction. PMID:24140622

  16. A software framework for analysing solid-state MAS NMR data.

    PubMed

    Stevens, Tim J; Fogh, Rasmus H; Boucher, Wayne; Higman, Victoria A; Eisenmenger, Frank; Bardiaux, Benjamin; van Rossum, Barth-Jan; Oschkinat, Hartmut; Laue, Ernest D

    2011-12-01

    Solid-state magic-angle-spinning (MAS) NMR of proteins has undergone many rapid methodological developments in recent years, enabling detailed studies of protein structure, function and dynamics. Software development, however, has not kept pace with these advances and data analysis is mostly performed using tools developed for solution NMR which do not directly address solid-state specific issues. Here we present additions to the CcpNmr Analysis software package which enable easier identification of spinning side bands, straightforward analysis of double quantum spectra, automatic consideration of non-uniform labelling schemes, as well as extension of other existing features to the needs of solid-state MAS data. To underpin this, we have updated and extended the CCPN data model and experiment descriptions to include transfer types and nomenclature appropriate for solid-state NMR experiments, as well as a set of experiment prototypes covering the experiments commonly employed by solid-sate MAS protein NMR spectroscopists. This work not only improves solid-state MAS NMR data analysis but provides a platform for anyone who uses the CCPN data model for programming, data transfer, or data archival involving solid-state MAS NMR data.

  17. 14N solid-state NMR: a sensitive probe of the local order in zeolites.

    PubMed

    Dib, Eddy; Mineva, Tzonka; Gaveau, Philippe; Alonso, Bruno

    2013-11-14

    Local order in as-synthesised zeolites templated by tetraalkylammonium cations is proven from solid-state (14)N NMR and related quadrupolar parameters, opening new perspectives in the study of porous materials.

  18. Phase identification and quantification in a devitrified glass using homo- and heteronuclear solid-state NMR.

    PubMed

    Tricot, Grégory; Delevoye, Laurent; Palavit, Gérard; Montagne, Lionel

    2005-11-14

    A complex mixture resulting from the devitrification of an aluminophosphate glass has been studied for the first time using a combination of homo- and heteronuclear solid-state NMR sequences that offers the advantage of subsequent quantification.

  19. Isotope Labeling for Solution and Solid-State NMR Spectroscopy of Membrane Proteins

    PubMed Central

    Verardi, Raffaello; Traaseth, Nathaniel J.; Masterson, Larry R.; Vostrikov, Vitaly V.; Veglia, Gianluigi

    2013-01-01

    In this chapter, we summarize the isotopic labeling strategies used to obtain high-quality solution and solid-state NMR spectra of biological samples, with emphasis on integral membrane proteins (IMPs). While solution NMR is used to study IMPs under fast tumbling conditions, such as in the presence of detergent micelles or isotropic bicelles, solid-state NMR is used to study the structure and orientation of IMPs in lipid vesicles and bilayers. In spite of the tremendous progress in biomolecular NMR spectroscopy, the homogeneity and overall quality of the sample is still a substantial obstacle to overcome. Isotopic labeling is a major avenue to simplify overlapped spectra by either diluting the NMR active nuclei or allowing the resonances to be separated in multiple dimensions. In the following we will discuss isotopic labeling approaches that have been successfully used in the study of IMPs by solution and solid-state NMR spectroscopy. PMID:23076578

  20. SedNMR: on the edge between solution and solid-state NMR.

    PubMed

    Bertini, Ivano; Luchinat, Claudio; Parigi, Giacomo; Ravera, Enrico

    2013-09-17

    Solid-state NMR (SS-NMR) of proteins requires that those molecules be immobilized, usually by crystallization, freezing, or lyophilization. However, self-crowding can also slow molecular rotation sufficiently to prevent the nuclear interactions from averaging. To achieve self-crowding, researchers can use a centrifugal field to create a concentration gradient or use regular ultracentrifugation to produce highly concentrated, gel-like solutions. Thus sedimented solute NMR (SedNMR) provides a simple method to prepare biological samples for SS-NMR experiments with minimal perturbation. This method may also give researchers a way to investigate species that are not otherwise accessible by NMR. We induce the sedimentation in one of two ways: (1) by the extreme centrifugal force exerted during magic angle spinning (MAS-induced sedimentation or in situ) or (2) by an ultracentrifuge (UC-induced sedimentation or ex situ). Sedimentation is particularly useful in situations where it is difficult to obtain protein crystals. Furthermore, because the proteins remain in a largely hydrated state, the sedimented samples may provide SS-NMR spectra that have better resolution than the spectra from frozen solutions or lyophilized powders. If sedimentation is induced in situ, the same protein sample can be used for both solution and SS-NMR studies. Finally, we show that in situ SedNMR can be used to detect the NMR signals of large molecular adducts that have binding constants that are too weak to allow for the selective isolation and crystallization of the complexed species. We can selectively induce sedimentation for the heaviest molecular species. Because the complexed molecules are subtracted from the bulk solution, the reaction proceeds further toward the formation of complexes.

  1. (31)P solid-state NMR based monitoring of permeation of cell penetrating peptides into skin.

    PubMed

    Desai, Pinaki R; Cormier, Ashley R; Shah, Punit P; Patlolla, Ram R; Paravastu, Anant K; Singh, Mandip

    2014-02-01

    The main objective of the current study was to investigate penetration of cell penetrating peptides (CPPs: TAT, R8, R11, and YKA) through skin intercellular lipids using (31)P magic angle spinning (MAS) solid-state NMR. In vitro skin permeation studies were performed on rat skin, and sections (0-60, 61-120, and 121-180μm) were collected and analyzed for (31)P NMR signal. The concentration-dependent shift of 0, 25, 50, 100, and 200mg/ml of TAT on skin layers, diffusion of TAT, R8, R11, and YKA in the skin and time dependent permeation of R11 was measured on various skin sections using (31)P solid-state NMR. Further, CPPs and CPP-tagged fluorescent dye encapsulate liposomes (FLip) in skin layers were tagged using confocal microscopy. The change in (31)P NMR chemical shift was found to depend monotonically on the amount of CPP applied on skin, with saturation behavior above 100mg/ml CPP concentration. R11 and TAT caused more shift in solid-state NMR peaks compared to other peptides. Furthermore, NMR spectra showed R11 penetration up to 180μm within 30min. The results of the solid-state NMR study were in agreement with confocal microscopy studies. Thus, (31)P solid-state NMR can be used to track CPP penetration into different skin layers. Copyright © 2013 Elsevier B.V. All rights reserved.

  2. 31P Solid-state NMR based monitoring of permeation of cell penetrating peptides into skin

    PubMed Central

    Desai, Pinaki R.; Cormier, Ashley R.; Shah, Punit P.; Patlolla, Ram R.; Paravastu, Anant K.; Singh, Mandip

    2013-01-01

    The main objective of the current study was to investigate penetration of cell penetrating peptides (CPPs: TAT, R8, R11 and YKA) through skin intercellular lipids using 31P magic angle spinning (MAS) solid-state NMR. In vitro skin permeation studies were performed on rat skin, sections (0–60, 61–120 and 121–180 µm) were collected and analyzed for 31P NMR signal. The concentration dependent shift of 0, 25, 50, 100 and 200 mg/ml of TAT on skin layers, diffusion of TAT, R8, R11 and YKA in the skin and time dependent permeation of R11 was measured on various skin sections using 31P solid-state NMR. Further, CPPs and CPP-tagged fluorescent dye encapsulate liposomes (FLip) in skin layers were tagged using confocal microscopy. The change in 31P NMR chemical shift was found to depend monotonically on the amount of CPP applied on skin, with saturation behavior above 100 mg/ml CPP concentration. R11 and TAT caused more shift in solid-state NMR peaks compared to other peptides. Furthermore, NMR spectra showed R11 penetration up to 180 µm within 30 min. The results of the solid-state NMR study were in agreement with confocal microscopy studies. Thus, 31P solid-state NMR can be used to track CPP penetration into different skin layers. PMID:23702274

  3. Lithium substitution in strontium chlorapatite studied by solid state NMR spectroscopy

    SciTech Connect

    Subramanian, S.; Sairam, T. N. Amarendra, G.; Maji, B. K.; Jena, H.

    2016-05-23

    Strontium Chlorapatites with various amounts of Li substitution (Sr{sub 10-x}Li{sub x}(PO{sub 4}){sub 6}Cl{sub 2-δ}) were prepared by solid state reaction method and characterized by powder XRD and solid state NMR spectroscopy. XRD reveals shortening of lattice parameters upon Li incorporation. The linewidth of {sup 31}P solid state Magic Angle Spinning NMR spectra decreases with increase in Li content within the apatite phase. This study confirms Li uptake within the apatite phase.

  4. Optimized multiple quantum MAS lineshape simulations in solid state NMR

    NASA Astrophysics Data System (ADS)

    Brouwer, William J.; Davis, Michael C.; Mueller, Karl T.

    2009-10-01

    The majority of nuclei available for study in solid state Nuclear Magnetic Resonance have half-integer spin I>1/2, with corresponding electric quadrupole moment. As such, they may couple with a surrounding electric field gradient. This effect introduces anisotropic line broadening to spectra, arising from distinct chemical species within polycrystalline solids. In Multiple Quantum Magic Angle Spinning (MQMAS) experiments, a second frequency dimension is created, devoid of quadrupolar anisotropy. As a result, the center of gravity of peaks in the high resolution dimension is a function of isotropic second order quadrupole and chemical shift alone. However, for complex materials, these parameters take on a stochastic nature due in turn to structural and chemical disorder. Lineshapes may still overlap in the isotropic dimension, complicating the task of assignment and interpretation. A distributed computational approach is presented here which permits simulation of the two-dimensional MQMAS spectrum, generated by random variates from model distributions of isotropic chemical and quadrupole shifts. Owing to the non-convex nature of the residual sum of squares (RSS) function between experimental and simulated spectra, simulated annealing is used to optimize the simulation parameters. In this manner, local chemical environments for disordered materials may be characterized, and via a re-sampling approach, error estimates for parameters produced. Program summaryProgram title: mqmasOPT Catalogue identifier: AEEC_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEEC_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 3650 No. of bytes in distributed program, including test data, etc.: 73 853 Distribution format: tar.gz Programming language: C, OCTAVE Computer: UNIX

  5. Solid state NMR: The essential technology for helical membrane protein structural characterization

    NASA Astrophysics Data System (ADS)

    Cross, Timothy A.; Ekanayake, Vindana; Paulino, Joana; Wright, Anna

    2014-02-01

    NMR spectroscopy of helical membrane proteins has been very challenging on multiple fronts. The expression and purification of these proteins while maintaining functionality has consumed countless graduate student hours. Sample preparations have depended on whether solution or solid-state NMR spectroscopy was to be performed - neither have been easy. In recent years it has become increasingly apparent that membrane mimic environments influence the structural result. Indeed, in these recent years we have rediscovered that Nobel laureate, Christian Anfinsen, did not say that protein structure was exclusively dictated by the amino acid sequence, but rather by the sequence in a given environment (Anfinsen, 1973) [106]. The environment matters, molecular interactions with the membrane environment are significant and many examples of distorted, non-native membrane protein structures have recently been documented in the literature. However, solid-state NMR structures of helical membrane proteins in proteoliposomes and bilayers are proving to be native structures that permit a high resolution characterization of their functional states. Indeed, solid-state NMR is uniquely able to characterize helical membrane protein structures in lipid environments without detergents. Recent progress in expression, purification, reconstitution, sample preparation and in the solid-state NMR spectroscopy of both oriented samples and magic angle spinning samples has demonstrated that helical membrane protein structures can be achieved in a timely fashion. Indeed, this is a spectacular opportunity for the NMR community to have a major impact on biomedical research through the solid-state NMR spectroscopy of these proteins.

  6. In situ solid-state NMR spectroscopy of electrochemical cells: batteries, supercapacitors, and fuel cells.

    PubMed

    Blanc, Frédéric; Leskes, Michal; Grey, Clare P

    2013-09-17

    Electrochemical cells, in the form of batteries (or supercapacitors) and fuel cells, are efficient devices for energy storage and conversion. These devices show considerable promise for use in portable and static devices to power electronics and various modes of transport and to produce and store electricity both locally and on the grid. For example, high power and energy density lithium-ion batteries are being developed for use in hybrid electric vehicles where they improve the efficiency of fuel use and help to reduce greenhouse gas emissions. To gain insight into the chemical reactions involving the multiple components (electrodes, electrolytes, interfaces) in the electrochemical cells and to determine how cells operate and how they fail, researchers ideally should employ techniques that allow real-time characterization of the behavior of the cells under operating conditions. This Account reviews the recent use of in situ solid-state NMR spectroscopy, a technique that probes local structure and dynamics, to study these devices. In situ NMR studies of lithium-ion batteries are performed on the entire battery, by using a coin cell design, a flat sealed plastic bag, or a cylindrical cell. The battery is placed inside the NMR coil, leads are connected to a potentiostat, and the NMR spectra are recorded as a function of state of charge. (7)Li is used for many of these experiments because of its high sensitivity, straightforward spectral interpretation, and relevance to these devices. For example, (7)Li spectroscopy was used to detect intermediates formed during electrochemical cycling such as LixC and LiySiz species in batteries with carbon and silicon anodes, respectively. It was also used to observe and quantify the formation and growth of metallic lithium microstructures, which can cause short circuits and battery failure. This approach can be utilized to identify conditions that promote dendrite formation and whether different electrolytes and additives can help

  7. (11)B MAS NMR and First-Principles Study of the [OBO3] Pyramids in Borates.

    PubMed

    Zhou, Bing; Sun, Wei; Zhao, Biao-Chun; Mi, Jin-Xiao; Laskowski, Robert; Terskikh, Victor; Zhang, Xi; Yang, Lingyun; Botis, Sanda M; Sherriff, Barbara L; Pan, Yuanming

    2016-03-07

    Borates are built from the [Bϕ3] planar triangles and the [Bϕ4] tetrahedral groups, where ϕ denotes O or OH. However, the [Bϕ4] groups in some borates are highly distorted to include three normal B-O bonds and one anomalously long B-O bond and, therefore, are best described as the [OBO3] pyramids. Four synthetic borates of the boracite-type structures (Mg3B7O13Br, Cu3B7O13Br, Zn3B7O13Cl, and Mg3B7O13Cl) containing a range of [OBO3] pyramids were investigated by multifield (7.05, 14.1, and 21.1 T) (11)B magic-angle spinning nuclear magnetic resonance (MAS NMR), triple quantum (3Q) MAS NMR experiments, as well as density functional theory calculations. The high-resolution (11)B MAS NMR spectra supported by theoretical predictions show that the [OBO3] pyramids are characterized by isotropic chemical shifts δiso((11)B) from 1.4(1) to 4.9(1) ppm and nuclear quadrupole parameters CQ((11)B) up to 1.3(1) MHz, both significantly different from those of the [BO4] and [BO3] groups in borates. These δiso((11)B) and CQ((11)B) values indicate that the [OBO3] pyramids represent an intermediate state between the [BO4] tetrahedra and [BO3] triangles and demonstrate that the (11)B NMR parameters of four-coordinate boron oxyanions are sensitive to local structural environments. The orientation of the calculated unique electronic field gradient tensor element Vzz of the [OBO3] pyramids is aligned approximately along the direction of the anomalously long B-O bond, corresponding to B-2pz with the lowest electron density.

  8. Natural-abundance solid-state 2H NMR spectroscopy at high magnetic field.

    PubMed

    Aliev, Abil E; Mann, Sam E; Iuga, Dinu; Hughes, Colan E; Harris, Kenneth D M

    2011-06-09

    High-resolution solid-state (2)H NMR spectroscopy provides a method for measuring (1)H NMR chemical shifts in solids and is advantageous over the direct measurement of high-resolution solid-state (1)H NMR spectra, as it requires only the application of routine magic angle sample spinning (MAS) and routine (1)H decoupling methods, in contrast to the requirement for complex pulse sequences for homonuclear (1)H decoupling and ultrafast MAS in the case of high-resolution solid-state (1)H NMR. However, a significant obstacle to the routine application of high-resolution solid-state (2)H NMR is the very low natural abundance of (2)H, with the consequent problem of inherently low sensitivity. Here, we explore the feasibility of measuring (2)H MAS NMR spectra of various solids with natural isotopic abundances at high magnetic field (850 MHz), focusing on samples of amino acids, peptides, collagen, and various organic solids. The results show that high-resolution solid-state (2)H NMR can be used successfully to measure isotropic (1)H chemical shifts in favorable cases, particularly for mobile functional groups, such as methyl and -N(+)H(3) groups, and in some cases phenyl groups. Furthermore, we demonstrate that routine (2)H MAS NMR measurements can be exploited for assessing the relative dynamics of different functional groups in a molecule and for assessing whole-molecule motions in the solid state. The magnitude and field-dependence of second-order shifts due to the (2)H quadrupole interaction are also investigated, on the basis of analysis of simulated and experimental (1)H and (2)H MAS NMR spectra of fully deuterated and selectively deuterated samples of the α polymorph of glycine at two different magnetic field strengths.

  9. Solid-State NMR-Restrained Ensemble Dynamics of a Membrane Protein in Explicit Membranes.

    PubMed

    Cheng, Xi; Jo, Sunhwan; Qi, Yifei; Marassi, Francesca M; Im, Wonpil

    2015-04-21

    Solid-state NMR has been used to determine the structures of membrane proteins in native-like lipid bilayer environments. Most structure calculations based on solid-state NMR observables are performed using simulated annealing with restrained molecular dynamics and an energy function, where all nonbonded interactions are represented by a single, purely repulsive term with no contributions from van der Waals attractive, electrostatic, or solvation energy. To our knowledge, this is the first application of an ensemble dynamics technique performed in explicit membranes that uses experimental solid-state NMR observables to obtain the refined structure of a membrane protein together with information about its dynamics and its interactions with lipids. Using the membrane-bound form of the fd coat protein as a model membrane protein and its experimental solid-state NMR data, we performed restrained ensemble dynamics simulations with different ensemble sizes in explicit membranes. For comparison, a molecular dynamics simulation of fd coat protein was also performed without any restraints. The average orientation of each protein helix is similar to a structure determined by traditional single-conformer approaches. However, their variations are limited in the resulting ensemble of structures with one or two replicas, as they are under the strong influence of solid-state NMR restraints. Although highly consistent with all solid-state NMR observables, the ensembles of more than two replicas show larger orientational variations similar to those observed in the molecular dynamics simulation without restraints. In particular, in these explicit membrane simulations, Lys(40), residing at the C-terminal side of the transmembrane helix, is observed to cause local membrane curvature. Therefore, compared to traditional single-conformer approaches in implicit environments, solid-state NMR restrained ensemble simulations in explicit membranes readily characterize not only protein

  10. A Solid-State NMR Experiment: Analysis of Local Structural Environments in Phosphate Glasses

    ERIC Educational Resources Information Center

    Anderson, Stanley E.; Saiki, David; Eckert, Hellmut; Meise-Gresch, Karin

    2004-01-01

    An experiment that can be used to directly study the local chemical environments of phosphorus in solid amorphous materials is demonstrated. The experiment aims at familiarizing the students of chemistry with the principles of solid-state NMR, by having them synthesize a simple phosphate glass, and making them observe the (super 31)P NMR spectrum,…

  11. A Solid-State NMR Experiment: Analysis of Local Structural Environments in Phosphate Glasses

    ERIC Educational Resources Information Center

    Anderson, Stanley E.; Saiki, David; Eckert, Hellmut; Meise-Gresch, Karin

    2004-01-01

    An experiment that can be used to directly study the local chemical environments of phosphorus in solid amorphous materials is demonstrated. The experiment aims at familiarizing the students of chemistry with the principles of solid-state NMR, by having them synthesize a simple phosphate glass, and making them observe the (super 31)P NMR spectrum,…

  12. Instrumentation for solid-state dynamic nuclear polarization with magic angle spinning NMR

    NASA Astrophysics Data System (ADS)

    Rosay, Melanie; Blank, Monica; Engelke, Frank

    2016-03-01

    Advances in dynamic nuclear polarization (DNP) instrumentation and methodology have been key factors in the recent growth of solid-state DNP NMR applications. We review the current state of the art of solid-state DNP NMR instrumentation primarily based on available commercial platforms. We start with a general system overview, including options for microwave sources and DNP NMR probes, and then focus on specific developments for DNP at 100 K with magic angle spinning (MAS). Gyrotron microwave sources, passive components to transmit microwaves, the DNP MAS probe, a cooling device for low-temperature MAS, and sample preparation procedures including radicals for DNP are considered.

  13. Solid-state NMR spectroscopic trends for supramolecular assemblies and protein aggregates.

    PubMed

    Linser, Rasmus

    2017-08-24

    Solid-state NMR is able to generate structural data on sample preparations that are explicitly non-crystalline. In particular, for amyloid fibril samples, which can comprise significant degrees of sample disorder, solid-state NMR has been used very successfully. But also solid-state NMR studies of other supramolecular assemblies that have resisted assessment by more standard methods are being performed with increasing ease and biological impact, many of which are briefly reviewed here. New technical trends with respect to structure calculation, protein dynamics and smaller sample amounts have reshaped the field of solid-state NMR recently. In particular, proton-detected approaches based on fast Magic-Angle Spinning (MAS) were demonstrated for crystalline systems initially. Currently, such approaches are being expanded to the above-mentioned non-crystalline targets, the characterization of which can now be pursued with sample amounts on the order of a milligram. In this Trends article, I am giving a brief overview about achievements of the last years as well as the directions that the field has been heading into and delineate some satisfactory perspectives for solid-state NMR's future striving. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. Solid state NMR methods for coal science. Progress report, January 1-March 31, 1984

    SciTech Connect

    Zilm, K.W.

    1984-04-01

    This report covers the progress made on the title project. The solid state NMR spectrometer has been completed and test results are presented. A number of alternative probe circuits have been evaluated for our solid state work. One has been found to be particularly efficient in use of decoupling power. Some progress has also been made in construction of a magic angle spinner for our probes as well. 2 figures, 1 table.

  15. New NMR tools for protein structure and function: Spin tags for dynamic nuclear polarization solid state NMR.

    PubMed

    Rogawski, Rivkah; McDermott, Ann E

    2017-08-15

    Magic angle spinning solid state NMR studies of biological macromolecules [1-3] have enabled exciting studies of membrane proteins [4,5], amyloid fibrils [6], viruses, and large macromolecular assemblies [7]. Dynamic nuclear polarization (DNP) provides a means to enhance detection sensitivity for NMR, particularly for solid state NMR, with many recent biological applications and considerable contemporary efforts towards elaboration and optimization of the DNP experiment. This review explores precedents and innovations in biological DNP experiments, especially highlighting novel chemical biology approaches to introduce the radicals that serve as a source of polarization in DNP experiments. Copyright © 2017. Published by Elsevier Inc.

  16. Solid-state NMR studies of form I of atorvastatin calcium.

    PubMed

    Wang, Wei David; Gao, Xudong; Strohmeier, Mark; Wang, Wei; Bai, Shi; Dybowski, Cecil

    2012-03-22

    Solid-state (13)C, (19)F, and (15)N magic angle spinning NMR studies of Form I of atorvastatin calcium are reported, including chemical shift tensors of all resolvable carbon sites and fluorine sites. The complete (13)C and (19)F chemical shift assignments are given based on an extensive analysis of (13)C-(1)H HETCOR and (13)C-(19)F HETCOR results. The solid-state NMR data indicate that the asymmetric unit of this material contains two atorvastatin molecules. A possible structure of Form I of atorvastatin calcium (ATC-I), derived from solid-state NMR data and density functional theory calculations of various structures, is proposed for this important active pharmaceutical ingredient (API).

  17. Solid State NMR Studies of Energy Conversion and Storage Materials

    NASA Astrophysics Data System (ADS)

    Jankuru Hennadige, Sohan Roshel De Silva

    NMR (Nuclear magnetic resonance) spectroscopy is utilized to study energy conversion and storage materials. Different types of NMR techniques including Magic Angle Spinning, Cross-polarization and relaxation measurement experiments were employed. Four different projects are discussed in this dissertation. First, three types of CFx battery materials were investigated. Electrochemical studies have demonstrated different electrochemical performances by one type, delivering superior performance over the other two. 13C and 19F MAS NMR techniques are employed to identify the atomic/molecular structural factors that might account for differences in electrochemical performance among different types. Next as the second project, layered polymer dielectrics were investigated by NMR. Previous studies have shown that thin film capacitors are improved by using alternate layers of two polymers with complementary properties: one with a high breakdown strength and one with high dielectric constant as opposed to monolithic layers. 13C to 1H cross-polarization techniques were used to investigate any inter-layer properties that may cause the increase in the dielectric strength. The third project was to study two types of thermoelectric materials. These samples were made of heavily doped phosphorous and boron in silicon by two different methods: ball-milled and annealed. These samples were investigated by NMR to determine the degree of disorder and obtain insight into the doping efficiency. The last ongoing project is on a lithium-ion battery system. The nature of passivating layers or the solid electrolyte interphase (SEI) formed on the electrodes surface is important because of the direct correlation between the SEI and the battery life time/durability. Multinuclear (7Li, 19F, 31P) techniques are employed to identify the composition of the SEI formation of both positive and negative electrodes.

  18. Perspectives in enzymology of membrane proteins by solid-state NMR.

    PubMed

    Ullrich, Sandra J; Glaubitz, Clemens

    2013-09-17

    Membrane proteins catalyze reactions at the cell membrane and facilitate thetransport of molecules or signals across the membrane. Recently researchers have made great progress in understanding the structural biology of membrane proteins, mainly based on X-ray crystallography. In addition, the application of complementary spectroscopic techniques has allowed researchers to develop a functional understanding of these proteins. Solid-state NMR has become an indispensable tool for the structure-function analysis of insoluble proteins and protein complexes. It offers the possibility of investigating membrane proteins directly in their environment, which provides essential information about the intrinsic coupling of protein structure and functional dynamics within the lipid bilayer. However, to date, researchers have hardly explored the enzymology of mem-brane proteins. In this Account, we review the perspectives for investigating membrane-bound enzymes by solid-state NMR. Understanding enzyme mechanisms requires access to kinetic parameters, structural analysis of the catalytic center, knowledge of the 3D structure and methods to follow the structural dynamics of the enzyme during the catalytic cycle. In principle, solid-state NMR can address all of these issues. Researchers can characterize the enzyme kinetics by observing substrate turnover within the membrane or at the membrane interphase in a time-resolved fashion as shown for diacylglycerol kinase. Solid-state NMR has also provided a mechanistic understanding of soluble enzymes including triosephosphate isomerase (TIM) and different metal-binding proteins, which demonstrates a promising perspective also for membrane proteins. The increasing availability of high magnetic fields and the development of new experimental schemes and computational protocols have made it easier to determine 3D structure using solid-state NMR. Dynamic nuclear polarization, a key technique to boost sensitivity of solid-state NMR at low

  19. In-Cell Solid-State NMR: An Emerging Technique for the Study of Biological Membranes

    PubMed Central

    Warnet, Xavier L.; Arnold, Alexandre A.; Marcotte, Isabelle; Warschawski, Dror E.

    2015-01-01

    Biological molecular processes are often studied in model systems, which simplifies their inherent complexity but may cause investigators to lose sight of the effects of the molecular environment. Information obtained in this way must therefore be validated by experiments in the cell. NMR has been used to study biological cells since the early days of its development. The first NMR structural studies of a protein inside a cell (by solution-state NMR) and of a membrane protein (by solid-state NMR) were published in 2001 and 2011, respectively. More recently, dynamic nuclear polarization, which has been used to enhance the signal in solid-state NMR, has also been applied to the study of frozen cells. Much progress has been made in the past 5 years, and in this review we take stock of this new technique, which is particularly appropriate for the study of biological membranes. PMID:26682804

  20. Solid state NMR studies of gels derived from low molecular mass gelators

    PubMed Central

    Kolehmainen, E.

    2016-01-01

    Since its invention more than six decades ago, nuclear magnetic resonance (NMR) spectroscopy has evolved as an inevitable part of chemical as well as structural analysis of small molecules, polymers, biomaterials and hybrid materials. In the solution state, due to the increased viscosity of complex viscoelastic fluids such as gels, liquid crystals and other soft materials, the rate of molecular tumbling is reduced, which in turn affects the chemical shift anisotropy, dipolar and quadrupolar interactions. As a consequence the solution state NMR spectra show broad lines, and therefore, extracting detailed structural information is a challenging task. In this context, solid state (SS) NMR has the ability to distinguish between a minute amount of polymorphic forms, conformational changes, and the number of non-equivalent molecules in an asymmetric unit of a crystal lattice, and to provide both qualitative as well as quantitative analytical data with a short-range order. Therefore, SS NMR has continued to evolve as an indispensable tool for structural analysis and gave birth to a new field called NMR crystallography. Solid state cross polarization (CP) and high resolution (HR) magic angle spinning (MAS) NMR spectroscopy has been used to study weak interactions in polymer gels. However, the application of SS NMR spectroscopy to study gels derived from low molecular weight gelators has been limited until recently. In this review, we will focus on the importance of solid state NMR spectroscopy in understanding and elucidating the structure of supramolecular gels derived from low molecular weight gelators with selected examples. PMID:27374054

  1. Solid state NMR studies of gels derived from low molecular mass gelators.

    PubMed

    Nonappa; Kolehmainen, E

    2016-07-13

    Since its invention more than six decades ago, nuclear magnetic resonance (NMR) spectroscopy has evolved as an inevitable part of chemical as well as structural analysis of small molecules, polymers, biomaterials and hybrid materials. In the solution state, due to the increased viscosity of complex viscoelastic fluids such as gels, liquid crystals and other soft materials, the rate of molecular tumbling is reduced, which in turn affects the chemical shift anisotropy, dipolar and quadrupolar interactions. As a consequence the solution state NMR spectra show broad lines, and therefore, extracting detailed structural information is a challenging task. In this context, solid state (SS) NMR has the ability to distinguish between a minute amount of polymorphic forms, conformational changes, and the number of non-equivalent molecules in an asymmetric unit of a crystal lattice, and to provide both qualitative as well as quantitative analytical data with a short-range order. Therefore, SS NMR has continued to evolve as an indispensable tool for structural analysis and gave birth to a new field called NMR crystallography. Solid state cross polarization (CP) and high resolution (HR) magic angle spinning (MAS) NMR spectroscopy has been used to study weak interactions in polymer gels. However, the application of SS NMR spectroscopy to study gels derived from low molecular weight gelators has been limited until recently. In this review, we will focus on the importance of solid state NMR spectroscopy in understanding and elucidating the structure of supramolecular gels derived from low molecular weight gelators with selected examples.

  2. A solid state and solution NMR study of the tautomerism in hydroxyquinoline carboxylic acids.

    PubMed

    Gudat, Dietrich; Nycz, Jacek E; Polanski, Jaroslaw

    2008-01-01

    Some hydroxyquinoline carboxylic acids and their conjugate acids and bases were characterized by 13C and 15N NMR spectroscopy in solution and in the solid state. Differences in 13C and, in particular, 15N chemical shift patterns allow to distinguish between individual tautomers and confirm the presence of zwitterionic species in the solid state. Solution NMR spectra in dimethyl sulfoxide (DMSO) show effects resulting as a consequence of dynamic exchange and suggest the presence of an equilibrium mixture of hydroxyquinoline carboxylic acid and zwitterionic hydroxyquinolinium carboxylate tautomers.

  3. Solid state NMR studies of materials for energy technology

    NASA Astrophysics Data System (ADS)

    Nambukara Kodiweera Arachchilage, Chandana K.

    Presented in this dissertation are NMR investigations of the dynamical and structural properties of materials for energy conversion and storage devices. 1H and 2H NMR was used to study water and methanol transportation in sulfonated poly(arylene ether ketone) based membranes for direct methanol fuel cells (DMFC). These results are presented in chapter 3. The amount of liquid in the membrane and ion exchange capacity (IEC) are two main factors that govern the dynamics in these membranes. Water and methanol diffusion coefficients also are comparable. Chapters 4 and 5 are concerned with 31P and 1H NMR in phosphoric acid doped PBI membranes (para-PBI and 2OH-PBI) as well as PBI membranes containing ionic liquids (H3PO4/PMIH2PO4/PBI). These membranes are designed for higher-temperature fuel cell operation. In general, stronger short and long range interactions were observed in the 2OH-PBI matrix, yielding reduced proton transport compared to that of para-PBI. In the case of H3PO4/PMIH2PO 4/PBI, both conductivity and diffusion are higher for the sample with molar ratio 2/4/1. Finally, chapter 6 is devoted to the 31P NMR MAS study of phosphorus-containing structural groups on the surfaces of micro/mesoporous activated carbons. Two spectral features were observed and the narrow feature identifies surface phosphates while the broad component identifies heterogeneous subsurface phosphorus environments including phosphate and more complex structure multiple P-C, P-N and P=N bonds.

  4. Solid state NMR: The essential technology for helical membrane protein structural characterization.

    PubMed

    Cross, Timothy A; Ekanayake, Vindana; Paulino, Joana; Wright, Anna

    2014-02-01

    NMR spectroscopy of helical membrane proteins has been very challenging on multiple fronts. The expression and purification of these proteins while maintaining functionality has consumed countless graduate student hours. Sample preparations have depended on whether solution or solid-state NMR spectroscopy was to be performed - neither have been easy. In recent years it has become increasingly apparent that membrane mimic environments influence the structural result. Indeed, in these recent years we have rediscovered that Nobel laureate, Christian Anfinsen, did not say that protein structure was exclusively dictated by the amino acid sequence, but rather by the sequence in a given environment (Anfinsen, 1973) [106]. The environment matters, molecular interactions with the membrane environment are significant and many examples of distorted, non-native membrane protein structures have recently been documented in the literature. However, solid-state NMR structures of helical membrane proteins in proteoliposomes and bilayers are proving to be native structures that permit a high resolution characterization of their functional states. Indeed, solid-state NMR is uniquely able to characterize helical membrane protein structures in lipid environments without detergents. Recent progress in expression, purification, reconstitution, sample preparation and in the solid-state NMR spectroscopy of both oriented samples and magic angle spinning samples has demonstrated that helical membrane protein structures can be achieved in a timely fashion. Indeed, this is a spectacular opportunity for the NMR community to have a major impact on biomedical research through the solid-state NMR spectroscopy of these proteins. Copyright © 2013 Elsevier Inc. All rights reserved.

  5. A "special perspectives" issue: Recent achievements and new directions in biomolecular solid state NMR

    NASA Astrophysics Data System (ADS)

    Tycko, Robert

    2015-04-01

    Twenty years ago, applications of solid state nuclear magnetic resonance (NMR) methods to real problems involving biological systems or biological materials were few and far between. Starting in the 1980s, a small number of research groups had begun to explore the possibility of obtaining structural and dynamical information about peptides, proteins, and other biopolymers from solid state NMR spectra. Progress was initially slow due to the relatively primitive state of solid state NMR probes, spectrometers, sample preparation methods, and pulse sequence techniques, coupled with the small number of people contributing to this research area. By the early 1990s, with the advent of new ideas about pulse sequence techniques such as dipolar recoupling, improvements in techniques for orienting membrane proteins and in technology for magic-angle spinning (MAS), improvements in the capabilities of commercial NMR spectrometers, and general developments in multidimensional spectroscopy, it began to appear that biomolecular solid state NMR might have a viable future. It was not until 1993 that the annual number of publications in this area crept above twenty.

  6. What Can Solid State NMR Contribute To Our Understanding of Protein Folding?

    PubMed Central

    Hu, Kan-Nian; Tycko, Robert

    2010-01-01

    Complete understanding of the folding process that connects a structurally disordered state of a protein to an ordered, biochemically functional state requires detailed characterization of intermediate structural states with high resolution and site specificity. While the intrinsically inhomogeneous and dynamic nature of unfolded and partially folded states limits the efficacy of traditional x-ray diffraction and solution NMR in structural studies, solid state NMR methods applied to frozen solutions can circumvent the complications due to molecular motions and conformational exchange encountered in unfolded and partially folded states. Moreover, solid state NMR methods can provide both qualitative and quantitative structural information at the site-specific level, even in the presence of structural inhomogeneity. This article reviews relevant solid state NMR methods and their initial applications to protein folding studies. Using either chemical denaturation to prepare unfolded states at equilibrium or a rapid freezing apparatus to trap non-equilibrium, transient structural states on a sub-millisecond time scale, recent results demonstrate that solid state NMR can contribute essential information about folding processes that is not available from more familiar biophysical methods. PMID:20542371

  7. In situ solid-state NMR for heterogeneous catalysis: a joint experimental and theoretical approach.

    PubMed

    Zhang, Weiping; Xu, Shutao; Han, Xiuwen; Bao, Xinhe

    2012-01-07

    In situ solid-state NMR is a well-established tool for investigations of the structures of the adsorbed reactants, intermediates and products on the surface of solid catalysts. The techniques allow identifications of both the active sites such as acidic sites and reaction processes after introduction of adsorbates and reactants inside an NMR rotor under magic angle spinning (MAS). The in situ solid-state NMR studies of the reactions can be achieved in two ways, i.e. under batch-like or continuous-flow conditions. The former technique is low cost and accessible to the commercial instrument while the latter one is close to the real catalytic reactions on the solids. This critical review describes the research progress on the in situ solid-state NMR techniques and the applications in heterogeneous catalysis under batch-like and continuous-flow conditions in recent years. Some typical probe molecules are summarized here to detect the Brønsted and Lewis acidic sites by MAS NMR. The catalytic reactions discussed in this review include methane aromatization, olefin selective oxidation and olefin metathesis on the metal oxide-containing zeolites. With combining the in situ MAS NMR spectroscopy and the density functional theoretical (DFT) calculations, the intermediates on the catalyst can be identified, and the reaction mechanism is revealed. Reaction kinetic analysis in the nanospace instead of in the bulk state can also be performed by employing laser-enhanced MAS NMR techniques in the in situ flow mode (163 references).

  8. Weak and Transient Protein Interactions Determined by Solid-State NMR.

    PubMed

    Dannatt, Hugh R W; Felletti, Michele; Jehle, Stefan; Wang, Yao; Emsley, Lyndon; Dixon, Nicholas E; Lesage, Anne; Pintacuda, Guido

    2016-06-01

    Despite their roles in controlling many cellular processes, weak and transient interactions between large structured macromolecules and disordered protein segments cannot currently be characterized at atomic resolution by X-ray crystallography or solution NMR. Solid-state NMR does not suffer from the molecular size limitations affecting solution NMR, and it can be applied to molecules in different aggregation states, including non-crystalline precipitates and sediments. A solid-state NMR approach based on high magnetic fields, fast magic-angle sample spinning, and deuteration provides chemical-shift and relaxation mapping that enabled the characterization of the structure and dynamics of the transient association between two regions in an 80 kDa protein assembly. This led to direct verification of a mechanism of regulation of E. coli DNA metabolism. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Dynamic Nuclear Polarization (DNP) solid-state NMR spectroscopy, a new approach to study humic material?

    NASA Astrophysics Data System (ADS)

    Knicker, Heike; Lange, Sascha; van Rossum, Barth; Oschkinat, Hartmut

    2016-04-01

    Compared to solution NMR spectroscopy, solid-state NMR spectra suffer from broad resonance lines and low resolution. This could be overcome by the use of 2-dimenstional solid-state NMR pulse sequences. Until recently, this approach has been unfeasible as a routine tool in soil chemistry, mainly because of the low NMR sensitivity of the respective samples. A possibility to circumvent those sensitivity problems represents high-field Dynamic Nuclear Polarization (DNP) solid-state NMR spectroscopy (Barnes et al., 2008), allowing considerable signal enhancements (Akbey et al., 2010). This is achieved by a microwave-driven transfer of polarization from a paramagnetic center to nuclear spins. Application of DNP to MAS spectra of biological systems (frozen solutions) showed enhancements of the factor 40 to 50 (Hall et al., 1997). Enhancements of this magnitude, thus may enable the use of at least some of the 2D solid-state NMR techniques that are presently already applied for pure proteins but are difficult to apply to soil peptides in their complex matrix. After adjusting the required acquisition parameters to the system "soil organic matter", lower but still promising enhancement factors were achieved. Additional optimization was performed and allowed the acquisition of 2D 13C and 15N solid-state NMR spectra of humified 13C and 15N enriched plant residues. Within the present contribution, the first solid-state DNP NMR spectra of humic material are presented. Those data demonstrate the great potential of this approach which certainly opens new doors for a better understanding of biochemical processes in soils, sediments and water. Akbey, Ü., Franks, W.T., Linden, A., Lange, S., Griffin, R.G., van Rossum, B.-J., Oschkinat, H., 2010. Dynamic nuclear polarization of deuterated proteins. Angewandte Chemie International Edition 49, 7803-7806. Barnes, A.B., De Paëpe, G., van der Wel, P.C.A., Hu, K.N., Joo, C.G., Bajaj, V.S., Mak-Jurkauskas, M.L., Sirigiri, J.R., Herzfeld, J

  10. Genetic algorithms and solid state NMR pulse sequences

    NASA Astrophysics Data System (ADS)

    Bechmann, Matthias; Clark, John; Sebald, Angelika

    2013-03-01

    The use of genetic algorithms for the optimisation of magic angle spinning NMR pulse sequences is discussed. The discussion uses as an example the optimisation of the C721 dipolar recoupling pulse sequence, aiming to achieve improved efficiency for spin systems characterised by large chemical shielding anisotropies and/or small dipolar coupling interactions. The optimised pulse sequence is found to be robust over a wide range of parameters, requires only minimal a priori knowledge of the spin system for experimental implementations with buildup rates being solely determined by the magnitude of the dipolar coupling interaction, but is found to be less broadbanded than the original C721 pulse sequence. The optimised pulse sequence breaks the synchronicity between r.f. pulses and sample spinning.

  11. Concepts and Methods of Solid-State NMR Spectroscopy Applied to Biomembranes.

    PubMed

    Molugu, Trivikram R; Lee, Soohyun; Brown, Michael F

    2017-09-14

    Concepts of solid-state NMR spectroscopy and applications to fluid membranes are reviewed in this paper. Membrane lipids with (2)H-labeled acyl chains or polar head groups are studied using (2)H NMR to yield knowledge of their atomistic structures in relation to equilibrium properties. This review demonstrates the principles and applications of solid-state NMR by unifying dipolar and quadrupolar interactions and highlights the unique features offered by solid-state (2)H NMR with experimental illustrations. For randomly oriented multilamellar lipids or aligned membranes, solid-state (2)H NMR enables direct measurement of residual quadrupolar couplings (RQCs) due to individual C-(2)H-labeled segments. The distribution of RQC values gives nearly complete profiles of the segmental order parameters SCD((i)) as a function of acyl segment position (i). Alternatively, one can measure residual dipolar couplings (RDCs) for natural abundance lipid samples to obtain segmental SCH order parameters. A theoretical mean-torque model provides acyl-packing profiles representing the cumulative chain extension along the normal to the aqueous interface. Equilibrium structural properties of fluid bilayers and various thermodynamic quantities can then be calculated, which describe the interactions with cholesterol, detergents, peptides, and integral membrane proteins and formation of lipid rafts. One can also obtain direct information for membrane-bound peptides or proteins by measuring RDCs using magic-angle spinning (MAS) in combination with dipolar recoupling methods. Solid-state NMR methods have been extensively applied to characterize model membranes and membrane-bound peptides and proteins, giving unique information on their conformations, orientations, and interactions in the natural liquid-crystalline state.

  12. Solid-state NMR and ESR studies of activated carbons produced from pecan shells

    USDA-ARS?s Scientific Manuscript database

    Activated carbon from pecan shells has shown promise as an adsorbent in water treatment and sugar refining. However, the chemistry of the material is complex and not fully understood. We report here the application of solid state NMR and ESR to study the chemical structure, mobility, and pore volu...

  13. Solid-state 87Rb NMR signatures for rubidium cations bound to a G-quadruplex.

    PubMed

    Ida, Ramsey; Wu, Gang

    2005-09-14

    We report the first solid-state 87Rb NMR characterization for rubidium cations bound to G-quartet structures formed by self-association of guanosine 5'-monophosphate and 5'-tert-butyl-dimethylsilyl-2', 3'-O-isopropylidene guanosine.

  14. High-Resolution Solid-State NMR Spectroscopy: Characterization of Polymorphism in Cimetidine, a Pharmaceutical Compound

    ERIC Educational Resources Information Center

    Pacilio, Julia E.; Tokarski, John T.; Quiñones, Rosalynn; Iuliucci, Robbie J.

    2014-01-01

    High-resolution solid-state NMR (SSNMR) spectroscopy has many advantages as a tool to characterize solid-phase material that finds applications in polymer chemistry, nanotechnology, materials science, biomolecular structure determination, and others, including the pharmaceutical industry. The technology associated with achieving high resolution…

  15. Investigation of Moisture Interaction with Cellulose Using Solid-State NMR

    USDA-ARS?s Scientific Manuscript database

    The interaction of water with cellulose and its influence on the nuclear spin dynamics in Gossypium barbadense (Pima) cotton were investigated by 1H and 13C solid-state NMR techniques. 1H spin diffusion results indicate that water is present in multiple layers within the cotton fiber, each layer bei...

  16. High-Resolution Solid-State NMR Spectroscopy: Characterization of Polymorphism in Cimetidine, a Pharmaceutical Compound

    ERIC Educational Resources Information Center

    Pacilio, Julia E.; Tokarski, John T.; Quiñones, Rosalynn; Iuliucci, Robbie J.

    2014-01-01

    High-resolution solid-state NMR (SSNMR) spectroscopy has many advantages as a tool to characterize solid-phase material that finds applications in polymer chemistry, nanotechnology, materials science, biomolecular structure determination, and others, including the pharmaceutical industry. The technology associated with achieving high resolution…

  17. Solid-state NMR investigations of membrane-associated antimicrobial peptides.

    PubMed

    Aisenbrey, Christopher; Bertani, Philippe; Bechinger, Burkhard

    2010-01-01

    Solid-state NMR and other biophysical investigations have revealed many mechanistic details about the interactions of antimicrobial peptides with membranes. These studies have shaped our view on how these peptides cause the killing of bacteria, fungi, or tumour cells and how they permeabilize model membranes. As a result, we better understand the biological activities of these peptides and we are now able to design new and better sequences. Here we present some of the tools that have allowed these solid-state NMR investigations, including detailed protocols on how to reconstitute the peptides into oriented or non-oriented membranes as well as simple set-up procedures for (2)H as well as proton-decoupled (31)P or (15)N solid-state NMR measurements. Static and magic angle spinning experiments are described. Where adequate, the special requirements for or limitations of some of the measurements are discussed. Solid-state NMR spectra of both lipids and peptides have been recorded, and through the ensemble of measurements a detailed picture of these complex peptide-lipid supramolecular systems has finally emerged.

  18. Chemical structure of soil organic matter in slickspots as investigated by advanced solid-state NMR

    USDA-ARS?s Scientific Manuscript database

    Slickspot soils are saline, and knowledge of their humic chemistry would contribute to our limited understanding how salinity affects soil C and N stocks. We characterized humic acids (HAs) from slickspot soils with solid-state 13C nuclear magnetic resonance (NMR). Expanding on previous use of cross...

  19. Investigation of Rhodopsin Dynamics in its Signaling State by Solid-State Deuterium NMR Spectroscopy

    PubMed Central

    Struts, Andrey V.; Chawla, Udeep; Perera, Suchithranga M.D.C.; Brown, Michael F.

    2017-01-01

    Site-directed deuterium NMR spectroscopy is a valuable tool to study the structural dynamics of biomolecules in cases where solution NMR is inapplicable. Solid-state 2H NMR spectral studies of aligned membrane samples of rhodopsin with selectively labeled retinal provide information on structural changes of the chromophore in different protein states. In addition, solid-state 2H NMR relaxation time measurements allow one to study the dynamics of the ligand during the transition from the inactive to the active state. Here we describe the methodological aspects of solid-state 2H NMR spectroscopy for functional studies of rhodopsin, with an emphasis on the dynamics of the retinal cofactor. We provide complete protocols for the preparation of NMR samples of rhodopsin with 11-cis-retinal selectively deuterated at the methyl groups in aligned membranes. In addition, we review optimized conditions for trapping the rhodopsin photointermediates; and lastly we address the challenging problem of trapping the signaling state of rhodopsin in aligned membrane films. PMID:25697522

  20. Studies of Molecular Dynamics by Solid State Deuterium NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhao, Baiyi

    The rotational dynamics of molecules in a number of solid systems were followed by variable temperature deuterium (^2H), nuclear magnetic resonance (NMR) spectroscopy via changes in the spectral lineshapes and spin-lattice relaxation times (T _1). First the pure solid trimethylamine-borane adduct, (CH_3)_3NBH_3, was studied. For a methyl deuterated sample, T _1 measurements yielded two T_1 minima, 6.9 ms and 4.3 ms corresponding to the slowing of methyl and trimethyl rotation, respectively, with decreasing temperature. Activation energies for methyl and trimethyl rotation, obtained from fitting the T _1 curve as a function of temperature, were 32.8 and 15.0 kJ/mol, respectively; simulations of the spectral lineshapes gave 26.6 and 18.9 kT/mol, respectively. Fitting of the ^2H T_1 curve for the borane deuterated sample gave a BH _3 rotation activation energy of 14.1 kT/mol and a ^2H quadrupolar coupling constant, chi, of 101 kHz. The activation energy for BH_3 rotation obtained from the spectral lineshape simulations gave 12.6 kT/mol. A series of deuterated organic chalcogen cations: (CH_3)_3S^+, (CH_3)_3Se^+ and (CH_3)_3Te^+, were ion exchanged into the cavities of sodium Mordenite LZ-M5 and the dynamics of these guests within the hydrated zeolite were followed by ^2H NMR. All three undergo isotropic motion above about -80 to -90^circC. Below this temperature two superimposed ^2H powder spectra appear; the broad lineshape is consistent with only methyl rotation in a hindered, coordinated site, and the other narrow lineshape is due to both methyl and trimethyl rotation in a less hindered, uncoordinated site. As the temperature is lowered the population of the lower energy coordinated site increases. Relative peak areas yield adsorption enthalpies of 6.7, 7.8 and 10.0 kJ/mol for (CH_3)_3S^+, (CH_3)_3Se^+ and (CH_3)_3Te^+, respectively. The series of methyl deuterated ammonium and phosphonium cations: (CH_3)NH_3^+ , (CH_3)_2NH^+ , (CH_3)_3NH^+ and (CH_3)_4P^+ , were

  1. Interaction of electrolyte molecules with carbon materials of well-defined porosity: characterization by solid-state NMR spectroscopy.

    PubMed

    Borchardt, Lars; Oschatz, Martin; Paasch, Silvia; Kaskel, Stefan; Brunner, Eike

    2013-09-28

    Electrochemical double-layer capacitors (EDLCs or supercapacitors) are of special potential interest with respect to energy storage. Nearly all EDLCs make use of porous carbons as electrode materials. Further tuning of their performance in EDLC applications requires a better understanding of their properties. In particular, the understanding of the interactions between carbon-based materials and electrolyte solutions is of fundamental interest with respect to future applications. Since the capacitance of carbon-based electrode materials is known to depend on the pore size, we have studied different porous carbon materials of well-defined, variable pore size loaded with 1 M TEABF4 in acetonitrile or with pure acetonitrile using solid-state magic angle spinning (MAS) (1)H, (11)B, and (13)C NMR spectroscopy.

  2. Magic-angle spinning solid-state multinuclear NMR on low-field instrumentation.

    PubMed

    Sørensen, Morten K; Bakharev, Oleg; Jensen, Ole; Jakobsen, Hans J; Skibsted, Jørgen; Nielsen, Niels Chr

    2014-01-01

    Mobile and cost-effective NMR spectroscopy exploiting low-field permanent magnets is a field of tremendous development with obvious applications for arrayed large scale analysis, field work, and industrial screening. So far such demonstrations have concentrated on relaxation measurements and lately high-resolution liquid-state NMR applications. With high-resolution solid-state NMR spectroscopy being increasingly important in a broad variety of applications, we here introduce low-field magic-angle spinning (MAS) solid-state multinuclear NMR based on a commercial ACT 0.45 T 62 mm bore Halbach magnet along with a homebuilt FPGA digital NMR console, amplifiers, and a modified standard 45 mm wide MAS probe for 7 mm rotors. To illustrate the performance of the instrument and address cases where the low magnetic field may offer complementarity to high-field NMR experiments, we demonstrate applications for (23)Na MAS NMR with enhanced second-order quadrupolar coupling effects and (31)P MAS NMR where reduced influence from chemical shift anisotropy at low field may facilitate determination of heteronuclear dipole-dipole couplings. Copyright © 2013 Elsevier Inc. All rights reserved.

  3. Magic-angle spinning solid-state multinuclear NMR on low-field instrumentation

    NASA Astrophysics Data System (ADS)

    Sørensen, Morten K.; Bakharev, Oleg; Jensen, Ole; Jakobsen, Hans J.; Skibsted, Jørgen; Nielsen, Niels Chr.

    2014-01-01

    Mobile and cost-effective NMR spectroscopy exploiting low-field permanent magnets is a field of tremendous development with obvious applications for arrayed large scale analysis, field work, and industrial screening. So far such demonstrations have concentrated on relaxation measurements and lately high-resolution liquid-state NMR applications. With high-resolution solid-state NMR spectroscopy being increasingly important in a broad variety of applications, we here introduce low-field magic-angle spinning (MAS) solid-state multinuclear NMR based on a commercial ACT 0.45 T 62 mm bore Halbach magnet along with a homebuilt FPGA digital NMR console, amplifiers, and a modified standard 45 mm wide MAS probe for 7 mm rotors. To illustrate the performance of the instrument and address cases where the low magnetic field may offer complementarity to high-field NMR experiments, we demonstrate applications for 23Na MAS NMR with enhanced second-order quadrupolar coupling effects and 31P MAS NMR where reduced influence from chemical shift anisotropy at low field may facilitate determination of heteronuclear dipole-dipole couplings.

  4. Solid-state (17)O NMR study of 2-acylbenzoic acids and warfarin.

    PubMed

    Kong, Xianqi; Dai, Yizhe; Wu, Gang

    We report synthesis and solid-state (17)O NMR characterization of four site-specifically (17)O-labeled 2-acylbenzoic acids (2-RC(O)C6H4COOH) where R=H and CH3): 2-[3-(17)O]formylbenzoic acid, 2-[1,2-(17)O2]formylbenzoic acid, 2-[3-(17)O]acetylbenzoic acid, and 2-[1,2,3-(17)O3]acetylbenzoic acid. In the solid state, both 2-formyl- and 2-acetyl-benzoic acids exist as the cyclic phthalide form each containing a five-membered lactone ring and a cyclic hemiacetal/hemiketal group. Static and magic-angle-spinning (17)O NMR spectra were recorded at 14.1 and 21.1T for these compounds, from which the (17)O chemical shift and nuclear quadrupolar coupling tensors were determined for each oxygen site. These results represent the first time that (17)O NMR tensors are fully characterized for lactone, cyclic hemiacetal, and cyclic hemiketal functional groups. We also report solid-state (17)O NMR data for the cyclic hemiketal group an anticoagulant drug, warfarin. Experimental (17)O NMR tensors in these compounds were compared with computational results obtained with a periodic DFT code BAND. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. Instrumentation for solid-state dynamic nuclear polarization with magic angle spinning NMR.

    PubMed

    Rosay, Melanie; Blank, Monica; Engelke, Frank

    2016-03-01

    Advances in dynamic nuclear polarization (DNP) instrumentation and methodology have been key factors in the recent growth of solid-state DNP NMR applications. We review the current state of the art of solid-state DNP NMR instrumentation primarily based on available commercial platforms. We start with a general system overview, including options for microwave sources and DNP NMR probes, and then focus on specific developments for DNP at 100K with magic angle spinning (MAS). Gyrotron microwave sources, passive components to transmit microwaves, the DNP MAS probe, a cooling device for low-temperature MAS, and sample preparation procedures including radicals for DNP are considered. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. Characterization of covalent protein conjugates using solid-state sup 13 C NMR spectroscopy

    SciTech Connect

    Garbow, J.R.; Fujiwara, Hideji; Sharp, C.R.; Logusch, E.W. )

    1991-07-23

    Cross-polarization magic-angle spinning (CPMAS) {sup 13}C NMR spectroscopy has been used to characterize covalent conjugates of alachlor, an {alpha}-chloroacetamide hapten, with glutathione (GSH) and bovine serum albumin (BSA). The solid-state NMR method demonstrates definitively the covalent nature of these conjugates and can also be used to characterize the sites of hapten attachment to proteins. Three different sites of alachlor binding are observed in the BSA system. Accurate quantitation of the amount of hapten covalently bound to GSH and BSA is reported. The solid-state {sup 13}C NMR technique can easily be generalized to study other small molecule/protein conjugates and can be used to assist the development and refinement of synthetic methods needed for the successful formation of such protein alkylation products.

  7. Protein Folding and Amyloid Formation: Good Questions for Solid State NMR

    NASA Astrophysics Data System (ADS)

    Tycko, Robert

    2005-03-01

    Recent results from two ongoing projects will be described. These projects illustrate the expanding capability of solid state NMR spectroscopy to provide unique information about the molecular structure of complex biochemical systems that are of current interest in the biophysical and biomedical research communities. Methodological advances that facilitate progress on these projects will be discussed briefly. In the area of protein folding, we are using solid state NMR spectroscopy to characterize the distributions of molecular structures in unfolded and partially folded states of relatively simple model proteins. The measurements are carried out on frozen glassy solutions at low temperatures. Initial results for the chemical denaturation of the 35-residue helical protein HP35 show that unfolding does not occur by a simple two-state process and that local conformational distributions in the unfolded state are remarkably non-uniform. In the area of amyloid fibrils, we are using solid state NMR to develop experimentally-based models for the molecular structure of peptide fibrils associated with Alzheimer's disease and other amyloid diseases, and to develop an understanding of the interactions that stabilize amyloid fibril structures in general. The NMR data also reveal molecular-level polymorphism in amyloid fibrils, with implications for biomedical issues such as the etiological role of fibrils in amyloid diseases and the structural basis for strains in prion diseases.

  8. Solid-state NMR spectra of lipid-anchored proteins under magic angle spinning.

    PubMed

    Nomura, Kaoru; Harada, Erisa; Sugase, Kenji; Shimamoto, Keiko

    2014-03-06

    Solid-state NMR is a promising tool for elucidating membrane-related biological phenomena. We achieved the measurement of high-resolution solid-state NMR spectra for a lipid-anchored protein embedded in lipid bilayers under magic angle spinning (MAS). To date, solid-state NMR measurements of lipid-anchored proteins have not been accomplished due to the difficulty in supplying sufficient amount of stable isotope labeled samples in the overexpression of lipid-anchored proteins requiring complex posttranslational modification. We designed a pseudo lipid-anchored protein in which the protein component was expressed in E. coli and attached to a chemically synthesized lipid-anchor mimic. Using two types of membranes, liposomes and bicelles, we demonstrated different types of insertion procedures for lipid-anchored protein into membranes. In the liposome sample, we were able to observe the cross-polarization and the (13)C-(13)C chemical shift correlation spectra under MAS, indicating that the liposome sample can be used to analyze molecular interactions using dipolar-based NMR experiments. In contrast, the bicelle sample showed sufficient quality of spectra through scalar-based experiments. The relaxation times and protein-membrane interaction were capable of being analyzed in the bicelle sample. These results demonstrated the applicability of two types of sample system to elucidate the roles of lipid-anchors in regulating diverse biological phenomena.

  9. Solid-state NMR in the analysis of drugs and naturally occurring materials.

    PubMed

    Paradowska, Katarzyna; Wawer, Iwona

    2014-05-01

    This article presents some of the solid-state NMR (SSNMR) techniques used in the pharmaceutical and biomedical research. Solid-state magic angle spinning (MAS) NMR provides structural information on powder amorphous solids for which single-crystal diffraction structures cannot be obtained. NMR is non-destructive; the powder sample may be used for further studies. Quantitative results can be obtained, although solid-state NMR spectra are not normally quantitative. As compared with other techniques, MAS NMR is insensitive and requires a significant amount of the powder sample (2-100mg) to fill the 1.3-7 mm ZrO2 rotor. This is its main drawback, since natural compounds isolated from plants, microorganisms or cell cultures are difficult to obtain in quantities higher than a few milligrams. Multinuclear MAS NMR routinely uses (1)H and (13)C nuclei, less frequently (15)N, (19)F, (31)P, (77)Se, (29)Si, (43)Ca or (23)Na. The article focuses on the pharmaceutical applications of SSNMR, the studies were aimed to control over manufacturing processes (e.g. crystallization and milling) investigation of chemical and physical stability of solid forms both as pure drug and in a formulated product. SSNMR is used in combination with some other analytical methods (DSC, XRD, FT-IR) and theoretical calculations of NMR parameters. Biologically active compounds, such as amino acids and small peptides, steroids and flavonoids were studied by SSNMR methods (part 4) providing valuable structural information. The SSNMR experiments performed on biopolymers and large natural products like proteins, cellulose and lipid layers are commented upon briefly in part 5. Copyright © 2013 Elsevier B.V. All rights reserved.

  10. Probing the nanostructure, interfacial interaction, and dynamics of chitosan-based nanoparticles by multiscale solid-state NMR.

    PubMed

    Wang, Fenfen; Zhang, Rongchun; Wu, Qiang; Chen, Tiehong; Sun, Pingchuan; Shi, An-Chang

    2014-12-10

    Chitosan-based nanoparticles (NPs) are widely used in drug and gene delivery, therapy, and medical imaging, but a molecular-level understanding of the internal morphology and nanostructure size, interface, and dynamics, which is critical for building fundamental knowledge for the precise design and efficient biological application of the NPs, remains a great challenge. Therefore, the availability of a multiscale (0.1-100 nm) and nondestructive analytical technique for examining such NPs is of great importance for nanotechnology. Herein, we present a new multiscale solid-state NMR approach to achieve this goal for the investigation of chitosan-poly(N-3-acrylamidophenylboronic acid) NPs. First, a recently developed (13)C multiple cross-polarization magic-angle spinning (MAS) method enabled fast quantitative determination of the NPs' composition and detection of conformational changes in chitosan. Then, using an improved (1)H spin-diffusion method with (13)C detection and theoretical simulations, the internal morphology and nanostructure size were quantitatively determined. The interfacial coordinated interaction between chitosan and phenylboronic acid was revealed by one-dimensional MAS and two-dimensional (2D) triple-quantum MAS (11)B NMR. Finally, dynamic-editing (13)C MAS and 2D (13)C-(1)H wide-line separation experiments provided details regarding the componential dynamics of the NPs in the solid and swollen states. On the basis of these NMR results, a model of the unique nanostructure, interfacial interaction, and componential dynamics of the NPs was proposed.

  11. High resolution 11B NMR of magnesium diboride using cryogenic magic angle spinning

    NASA Astrophysics Data System (ADS)

    Beckett, Peter; Denning, Mark S.; Heinmaa, Ivo; Dimri, Mukesh C.; Young, Edward A.; Stern, Raivo; Carravetta, Marina

    2012-09-01

    Static and magic-angle spinning 11B nuclear magnetic resonance (NMR) data at 4.7 T and 8.5 T have been obtained under cryogenic conditions on a diluted sample of magnesium diboride powder in the normal and superconducting state. The data provide accurate information on the magnetic shift and longitudinal relaxation time down to a temperature of 8 K, with a resolution improvement over the entire temperature range. The onset of superconductivity is unaffected by the sample rotation, as revealed by a steep variation of the magnetic shift just below the critical temperature.

  12. (13)C and (15)N solid-state NMR studies on albendazole and cyclodextrin albendazole complexes.

    PubMed

    Ferreira, M João G; García, A; Leonardi, D; Salomon, Claudio J; Lamas, M Celina; Nunes, Teresa G

    2015-06-05

    (13)C and (15)N solid-state nuclear magnetic resonance (NMR) spectra were recorded from albendazole (ABZ) and from ABZ:β-cyclodextrin, ABZ:methyl-β-cyclodextrin, ABZ:hydroxypropyl-β-cyclodextrin and ABZ:citrate-β-cyclodextrin, which were prepared by the spray-drying technique. ABZ signals were typical of a crystalline solid for the pure drug and of an amorphous compound obtained from ABZ:cyclodextrin samples. Relevant spectral differences were correlated with chemical interaction between ABZ and cyclodextrins. The number and type of complexes revealed a strong dependence on the cyclodextrin group substituent. Solid-state NMR data were consistent with the presence of stable inclusion complexes. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. High resolution 11B NMR of MgB2 using cryogenic magic-angle spinning

    NASA Astrophysics Data System (ADS)

    Stern, Raivo; Beckett, Peter; Denning, Mark S.; Heinmaa, Ivo; Dimri, Mukesh C.; Young, Edward A.; Carravetta, Marina

    2013-03-01

    Static and magic-angle spinning (MAS) 11B NMR data at 4.7 T and 8.5 T have been obtained under cryogenic conditions on a diluted sample of magnesium diboride powder in the normal and superconducting state. We demonstrate that MAS NMR is possible on type-II superconductors despite the sample rotation. The data provide accurate information on the magnetic shift variation and longitudinal relaxation data down to a temperature of 8 K, with a resolution improvement over the entire temperature range. The onset of superconductivity is unaffected by the sample rotation, as revealed by a steep variation of the magnetic shift just below the critical temperature. Appeared in JCP 137, 114201, http://dx.doi.org/10.1063/1.4751476

  14. Oxygen-17 dynamic nuclear polarisation enhanced solid-state NMR spectroscopy at 18.8 T.

    PubMed

    Brownbill, Nick J; Gajan, David; Lesage, Anne; Emsley, Lyndon; Blanc, Frédéric

    2017-02-23

    We report (17)O dynamic nuclear polarisation (DNP) enhanced solid-state NMR experiments at 18.8 T. Several formulations were investigated on the Mg(OH)2 compound. A signal enhancement factor of 17 could be obtained when the solid particles were incorporated into a glassy o-terphenyl matrix doped with BDPA using the Overhauser polarisation transfer scheme whilst the cross effect mechanism enabled by TEKPol yielded a slightly lower enhancement but more time efficient data acquisition.

  15. LARGE SCALE PRODUCTION, PURIFICATION, AND 65CU SOLID STATE NMR OF AZURIN

    SciTech Connect

    Gao, A.; Heck, R.W.

    2008-01-01

    This paper details a way to produce azurin with an effi ciency over 10 times greater than previously described and demonstrates the fi rst solid state nuclear magnetic resonance spectrum of 65Cu(I) in a metalloprotein. A synthetic gene for azurin based upon the DNA sequence from Pseudomonas aeruginosa including the periplasmic targeting sequence was subcloned into a T7 overexpression vector to create the plasmid pGS-azurin, which was transformed into BL21 (DE3) competent cells. The leader sequence on the expressed protein causes it to be exported to the periplasmic space of Escherichia coli. Bacteria grown in a fermentation unit were induced to overexpress the azurin, which was subsequently purifi ed through an endosmotic shock procedure followed by high performance liquid chromatography (HPLC). 1,500 mg of azurin were purifi ed per liter of culture. 65Cu(II) was added to apo-azurin and then reduced. The 65Cu metal cofactor in azurin was observed with solid state nuclear magnetic resonance (NMR) to determine any structural variations that accompanied copper reduction. This is the fi rst solid state NMR spectra of a copper(I) metalloprotein. Analysis of the NMR spectra is being used to complement hypotheses set forth by x-ray diffraction and computational calculations of electron transfer mechanisms in azurin.

  16. Solid-State NMR Studies Reveal Native-like β-Sheet Structures in Transthyretin Amyloid

    SciTech Connect

    Lim, Kwang Hun; Dasari, Anvesh K. R.; Hung, Ivan; Gan, Zhehong; Kelly, Jeffery W.; Wright, Peter E.; Wemmer, David E.

    2016-09-20

    © 2016 American Chemical Society. Structural characterization of amyloid rich in cross-β structures is crucial for unraveling the molecular basis of protein misfolding and amyloid formation associated with a wide range of human disorders. Elucidation of the β-sheet structure in noncrystalline amyloid has, however, remained an enormous challenge. Here we report structural analyses of the β-sheet structure in a full-length transthyretin amyloid using solid-state NMR spectroscopy. Magic-angle-spinning (MAS) solid-state NMR was employed to investigate native-like β-sheet structures in the amyloid state using selective labeling schemes for more efficient solid-state NMR studies. Analyses of extensive long-range 13 C- 13 C correlation MAS spectra obtained with selectively 13 CO- and 13 Cα-labeled TTR reveal that the two main β-structures in the native state, the CBEF and DAGH β-sheets, remain intact after amyloid formation. The tertiary structural information would be of great use for examining the quaternary structure of TTR amyloid.

  17. Solid-State NMR Studies Reveal Native-like β-Sheet Structures in Transthyretin Amyloid

    DOE PAGES

    Lim, Kwang Hun; Dasari, Anvesh K. R.; Hung, Ivan; ...

    2016-09-20

    © 2016 American Chemical Society. Structural characterization of amyloid rich in cross-β structures is crucial for unraveling the molecular basis of protein misfolding and amyloid formation associated with a wide range of human disorders. Elucidation of the β-sheet structure in noncrystalline amyloid has, however, remained an enormous challenge. Here we report structural analyses of the β-sheet structure in a full-length transthyretin amyloid using solid-state NMR spectroscopy. Magic-angle-spinning (MAS) solid-state NMR was employed to investigate native-like β-sheet structures in the amyloid state using selective labeling schemes for more efficient solid-state NMR studies. Analyses of extensive long-range 13 C- 13 C correlationmore » MAS spectra obtained with selectively 13 CO- and 13 Cα-labeled TTR reveal that the two main β-structures in the native state, the CBEF and DAGH β-sheets, remain intact after amyloid formation. The tertiary structural information would be of great use for examining the quaternary structure of TTR amyloid.« less

  18. Detergent Optimized Membrane Protein Reconstitution in Liposomes for Solid State NMR

    PubMed Central

    2015-01-01

    For small helical membrane proteins, their structures are highly sensitive to their environment, and solid state NMR is a structural technique that can characterize these membrane proteins in native-like lipid bilayers and proteoliposomes. To date, a systematic method by which to evaluate the effect of the solubilizing detergent on proteoliposome preparations for solid state NMR of membrane proteins has not been presented in the literature. A set of experiments are presented aimed at determining the conditions most amenable to dialysis mediated reconstitution sample preparation. A membrane protein from M. tuberculosis is used to illustrate the method. The results show that a detergent that stabilizes the most protein is not always ideal and sometimes cannot be removed by dialysis. By focusing on the lipid and protein binding properties of the detergent, proteoliposome preparations can be readily produced, which provide double the signal-to-noise ratios for both the oriented sample and magic angle spinning solid state NMR. The method will allow more membrane protein drug targets to be structurally characterized in lipid bilayer environments. PMID:24665863

  19. Solid state 19F NMR parameters of fluorine-labeled amino acids. Part I: Aromatic substituents

    NASA Astrophysics Data System (ADS)

    Dürr, Ulrich H. N.; Grage, Stephan L.; Witter, Raiker; Ulrich, Anne S.

    2008-03-01

    Structural parameters of peptides and proteins in biomembranes can be directly measured by solid state NMR of selectively labeled amino acids. The 19F nucleus is a promising label to overcome the low sensitivity of 2H, 13C or 15N, and to serve as a background-free reporter group in biological compounds. To make the advantages of solid state 19F NMR fully available for structural studies of polypeptides, we have systematically measured the chemical shift anisotropies and relaxation properties of the most relevant aromatic and aliphatic 19F-labeled amino acids. In this first part of two consecutive contributions, six different 19F-substituents on representative aromatic side chains were characterized as polycrystalline powders by static and MAS experiments. The data are also compared with results on the same amino acids incorporated in synthetic peptides. The spectra show a wide variety of lineshapes, from which the principal values of the CSA tensors were extracted. In addition, temperature-dependent T1 and T2 relaxation times were determined by 19F NMR in the solid state, and isotropic chemical shifts and scalar couplings were obtained in solution.

  20. Mechanism of dilute-spin-exchange in solid-state NMR

    SciTech Connect

    Lu, George J.; Opella, Stanley J.

    2014-03-28

    In the stationary, aligned samples used in oriented sample (OS) solid-state NMR, {sup 1}H-{sup 1}H homonuclear dipolar couplings are not attenuated as they are in magic angle spinning solid-state NMR; consequently, they are available for participation in dipolar coupling-based spin-exchange processes. Here we describe analytically the pathways of {sup 15}N-{sup 15}N spin-exchange mediated by {sup 1}H-{sup 1}H homonuclear dipolar couplings. The mixed-order proton-relay mechanism can be differentiated from the third spin assisted recoupling mechanism by setting the {sup 1}H to an off-resonance frequency so that it is at the “magic angle” during the spin-exchange interval in the experiment, since the “magic angle” irradiation nearly quenches the former but only slightly attenuates the latter. Experimental spectra from a single crystal of N-acetyl leucine confirm that this proton-relay mechanism plays the dominant role in {sup 15}N-{sup 15}N dilute-spin-exchange in OS solid-state NMR in crystalline samples. Remarkably, the “forbidden” spin-exchange condition under “magic angle” irradiation results in {sup 15}N-{sup 15}N cross-peaks intensities that are comparable to those observed with on-resonance irradiation in applications to proteins. The mechanism of the proton relay in dilute-spin-exchange is crucial for the design of polarization transfer experiments.

  1. Boric Acid Adsorption onto Humic Acids: Structures, Stabilities, 11B NMR and 11B,10B Isotopic Fractionations of Surface Complexes

    NASA Astrophysics Data System (ADS)

    Tossell, J. A.

    2006-05-01

    Boric acid, B(OH)3, forms complexes in aqueous solution with a number of bidentate O-containing ligands, L- 2, such as C2O4-2 (oxalate), C3H2O4-2 (malonate), C2H4O2-2 (glycolate), C6H4O2-2 (catecholate) and C10H6O2-2 (dioxynaphthalene). McElligot and Byrne (1998) have also found it to form a complex with CO3-2. Recently Lemarchand, et al. (2005) have studied the formation of surface complexes of B(OH)3 on humic acid, determining formation constants, 11B NMR shifts and 11B,10B isotope fractionations for a number of such complexes. This helps to clarify both the interaction of boric acid with the humic acid and the nature of the coordinating sites on the humic acid. The determination of isotope fractionations may be seen as a form of vibrational spectroscopy, using the fractionating element as a local probe of the vibrational spectrum which determines the fractionation. We have calculated quantum mechanically the structures, stabilities, vibrational spectra, 11B NMR spectra and 11B,110B isotope fractionations of a number of complexes B(OH)2L- formed by reactions of the type: B(OH)3 + HL- ? B(OH)2L- + H2O (1) using the 6-311G(d,p) B3LYP method for structures and isotopic fractionations, the highly accurate Complete Basis Set-QB3 method for energetics and the GIAO HF method with a 6-311+G(2d,p) basis for the NMR shieldings. Oxalic acid, malonic acid and catechol all form stable complexes (?G<0 for reaction 1),which are deshielded (less negative ?) vs. B(OH)4- by 2.7, 0.6 and 5.6 ppm, respectively, and which are isotopically lighter than B(OH)4- (more negative ? 11B) by 3, 2 and 5 ‰, respectively. The calculated 11B NMR shifts match well with the results of Lemarchand, et al. (2005) while the calculated isotopic fractionations are qualitatively consistent with their results, but show much smaller deviations from B(OH)4-. This is probably a consequence of the use by these authors of a value of 1.0194 (Kakihana, et al., 1977) for the 11B,10B isotopic exchange

  2. Solid-State NMR Spectroscopy of Metal–Organic Framework Compounds (MOFs)

    PubMed Central

    Hoffmann, Herbert C.; Debowski, Marta; Müller, Philipp; Paasch, Silvia; Senkovska, Irena; Kaskel, Stefan; Brunner, Eike

    2012-01-01

    Nuclear Magnetic Resonance (NMR) spectroscopy is a well-established method for the investigation of various types of porous materials. During the past decade, metal–organic frameworks have attracted increasing research interest. Solid-state NMR spectroscopy has rapidly evolved into an important tool for the study of the structure, dynamics and flexibility of these materials, as well as for the characterization of host–guest interactions with adsorbed species such as xenon, carbon dioxide, water, and many others. The present review introduces and highlights recent developments in this rapidly growing field.

  3. Monitoring the Electrochemical Processes in the Lithium–Air Battery by Solid State NMR Spectroscopy

    PubMed Central

    2013-01-01

    A multi-nuclear solid-state NMR approach is employed to investigate the lithium–air battery, to monitor the evolution of the electrochemical products formed during cycling, and to gain insight into processes affecting capacity fading. While lithium peroxide is identified by 17O solid state NMR (ssNMR) as the predominant product in the first discharge in 1,2-dimethoxyethane (DME) based electrolytes, it reacts with the carbon cathode surface to form carbonate during the charging process. 13C ssNMR provides evidence for carbonate formation on the surface of the carbon cathode, the carbonate being removed at high charging voltages in the first cycle, but accumulating in later cycles. Small amounts of lithium hydroxide and formate are also detected in discharged cathodes and while the hydroxide formation is reversible, the formate persists and accumulates in the cathode upon further cycling. The results indicate that the rechargeability of the battery is limited by both the electrolyte and the carbon cathode stability. The utility of ssNMR spectroscopy in directly detecting product formation and decomposition within the battery is demonstrated, a necessary step in the assessment of new electrolytes, catalysts, and cathode materials for the development of a viable lithium–oxygen battery. PMID:24489976

  4. Recent progress in solid-state NMR studies of drugs confined within drug delivery systems.

    PubMed

    Skorupska, Ewa; Jeziorna, Agata; Kazmierski, Slawomir; Potrzebowski, Marek J

    2014-01-01

    Recent progress in the application of solid-state NMR (SS NMR) spectroscopy in structural studies of active pharmaceutical ingredients (APIs) embedded in different drug carriers is detailed. This article is divided into sections. The first part reports short characterization of the nanoparticles and microparticles that can be used as drug delivery systems (DDSs). The second part shows the applicability of SS NMR to study non-steroidal anti-inflammatory drugs (NSAIDs). In this section, problems related to API-DDS interactions, morphology, local molecular dynamics, nature of inter- or intramolecular connections, and pore filling are reviewed for different drug carriers (e.g. mesoporous silica nanoparticles (MSNs), cyclodextrins, polymeric matrices and others). The third and fourth sections detail the recent applications of SS NMR for searching for antibiotics and anticancer drugs confined in zeolites, MSNs, amorphous calcium phosphate and other carriers.

  5. Proton detection of MAS solid-state NMR spectra of half-integer quadrupolar nuclei.

    PubMed

    Venkatesh, Amrit; Hanrahan, Michael P; Rossini, Aaron J

    Fast magic angle spinning (MAS) and proton detection has found widespread application to enhance the sensitivity of solid-state NMR experiments with spin-1/2 nuclei such as (13)C, (15)N and (29)Si, however, this approach is not yet routinely applied to half-integer quadrupolar nuclei. Here we have investigated the feasibility of using fast MAS and proton detection to enhance the sensitivity of solid-state NMR experiments with half-integer quadrupolar nuclei. The previously described dipolar hetero-nuclear multiple quantum correlation (D-HMQC) and dipolar refocused insensitive nuclei enhanced by polarization transfer (D-RINEPT) pulse sequences were used for proton detection of half-integer quadrupolar nuclei. Quantitative comparisons of signal-to-noise ratios and the sensitivity of proton detected D-HMQC and D-RINEPT and direct detection spin echo and quadrupolar Carr-Purcell Meiboom-Gill (QCPMG) solid-state NMR spectra, demonstrate that one dimensional proton detected experiments can provide sensitivity similar to or exceeding that obtainable with direct detection QCPMG experiments. 2D D-HMQC and D-RINEPT experiments provide less sensitivity than QCPMG experiments but proton detected 2D hetero-nuclear correlation solid-state NMR spectra of half-integer nuclei can still be acquired in about the same time as a 1D spin echo spectrum. Notably, the rarely used D-RINEPT pulse sequence is found to provide similar, or better sensitivity than D-HMQC in some cases. Proton detected D-RINEPT benefits from the short longitudinal relaxation times (T1) normally associated with half-integer quadrupolar nuclei, it can be combined with existing signal enhancement methods for quadrupolar nuclei, and t1-noise in the indirect dimension can easily be removed by pre-saturation of the (1)H nuclei. The rapid acquisition of proton detected 2D HETCOR solid-state NMR spectra of a range of half-integer quadrupolar nuclei such as (17)O, (27)Al, (35)Cl and (71)Ga is demonstrated. Copyright

  6. Solid-state 17O NMR of pharmaceutical compounds: salicylic acid and aspirin.

    PubMed

    Kong, Xianqi; Shan, Melissa; Terskikh, Victor; Hung, Ivan; Gan, Zhehong; Wu, Gang

    2013-08-22

    We report solid-state NMR characterization of the (17)O quadrupole coupling (QC) and chemical shift (CS) tensors in five site-specifically (17)O-labeled samples of salicylic acid and o-acetylsalicylic acid (Aspirin). High-quality (17)O NMR spectra were obtained for these important pharmaceutical compounds under both static and magic angle spinning (MAS) conditions at two magnetic fields, 14.0 and 21.1 T. A total of 14 (17)O QC and CS tensors were experimentally determined for the seven oxygen sites in salicylic acid and Aspirin. Although both salicylic acid and Aspirin form hydrogen bonded cyclic dimers in the solid state, we found that the potential curves for the concerted double proton transfer in these two compounds are significantly different. In particular, while the double-well potential curve in Aspirin is nearly symmetrical, it is highly asymmetrical in salicylic acid. This difference results in quite different temperature dependencies in (17)O MAS spectra of the two compounds. A careful analysis of variable-temperature (17)O MAS NMR spectra of Aspirin allowed us to obtain the energy asymmetry (ΔE) of the double-well potential, ΔE = 3.0 ± 0.5 kJ/mol. We were also able to determine a lower limit of ΔE for salicylic acid, ΔE > 10 kJ/mol. These asymmetrical features in potential energy curves were confirmed by plane-wave DFT computations, which yielded ΔE = 3.7 and 17.8 kJ/mol for Aspirin and salicylic acid, respectively. To complement the solid-state (17)O NMR data, we also obtained solid-state (1)H and (13)C NMR spectra for salicylic acid and Aspirin. Using experimental NMR parameters obtained for all magnetic nuclei present in salicylic acid and Aspirin, we found that plane-wave DFT computations can produce highly accurate NMR parameters in well-defined crystalline organic compounds.

  7. Structure and dynamics of retinal in rhodopsin elucidated by deuterium solid state NMR

    NASA Astrophysics Data System (ADS)

    Salgado, Gilmar Fernandes De Jesus

    Rhodopsin is a seven transmembrane helix GPCR found which mediates dim light vision, in which the binding pocket is occupied by the ligand 11- cis-retinal. A site-directed 2H-labeling approach utilizing solid-state 2H NMR spectroscopy was used to investigate the structure and dynamics of retinal within its binding pocket in the dark state of rhodopsin, and as well the MetaI and MetaII. 11-cis-[5-C 2H3]-, 11-cis-[9-C 2H3]-, and 11-cis-[13-C2H 3]-retinal were used to regenerate bleached rhodopsin. Recombinant membranes comprising purified rhodopsin and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) were prepared (1:50 molar ratio). Solid-state 2H NMR spectra were obtained for the aligned rhodopsin/POPC recombinant membranes at temperatures below the order-disorder phase transition temperature of POPC. The solid-state NMR studies of aligned samples, give the orientations of the 2H nuclear coupling tensor relative to the membrane frame, which involve both the conformation and orientation of the bound retinal chromophore. Theoretical simulations of the experimental 2H NMR spectra employed a new lineshape treatment for a semi-random distribution due to static uniaxial disorder. The analysis gives the orientation of the 2H-labeled C-C2H3 methyl bond axes relative to the membrane plane as well as the extent of three-dimensional alignment disorder (mosaic spread). These results clearly demonstrate the applicability of site-directed 2H NMR methods for investigating conformational changes and dynamics of ligands bound to rhodopsin and other GPCRs in relation to their characteristic mechanisms of action.

  8. Prospects for (207)Pb solid-state NMR studies of lead tetrel bonds.

    PubMed

    Southern, Scott A; Errulat, Dylan; Frost, Jamie M; Gabidullin, Bulat; Bryce, David L

    2017-07-20

    The feasibility and value of (207)Pb solid-state NMR experiments on compounds featuring lead tetrel bonds is explored. Although the definition remains to be formalized, lead tetrel bonds may be qualitatively described as existing when there is evidence of a net attractive interaction between an electrophilic region associated with lead in a molecular entity and a nucleophilic region in another, or the same, molecular entity. Unambiguous identification of lead tetrel bonds can be challenging due to the hypervalent tendency of lead. We report here a series of (207)Pb solid-state NMR experiments on five metal-organic frameworks featuring lead coordinated to hydrazone-based ligands. Such frameworks may be held together in part by lead tetrel bonds. The acquisition of (207)Pb solid-state NMR spectra for such materials is feasible and is readily accomplished using a combination of magic-angle spinning and Carr-Purcell-Meiboom-Gill methods in moderate to low applied magnetic fields. The lead centres are characterized by (207)Pb isotropic chemical shifts ranging from -426 to -2591 ppm and chemical shift tensor spans ranging from 910 to 2681 ppm. Careful inspection of the structures of the compounds and the literature (207)Pb NMR data may suggest that a tetrel bond to lead results in chemical shift parameters which are intermediate between those which are characteristic of holodirected and hemidirected lead coordination geometries. Challenges associated with DFT computations of the (207)Pb NMR parameters are discussed. In summary, the (207)Pb data for the compounds studied herein show a marked response to the presence of non-coordinating electron-rich moieties in close contact with the electrophilic surface of formally hemidirectionally coordinated lead compounds.

  9. Rapid acquisition of wideline MAS solid-state NMR spectra with fast MAS, proton detection, and dipolar HMQC pulse sequences.

    PubMed

    Rossini, Aaron J; Hanrahan, Michael P; Thuo, Martin

    2016-09-14

    The solid-state NMR spectra of many NMR active elements are often extremely broad due to the presence of chemical shift anisotropy (CSA) and/or the quadrupolar interaction (for nuclei with spin I > 1/2). These NMR interactions often give rise to wideline solid-state NMR spectra which can span hundreds of kHz or several MHz. Here we demonstrate that by using fast MAS, proton detection and dipolar hetero-nuclear multiple-quantum (D-HMQC) pulse sequences, it is possible to rapidly acquire 2D spectra which correlate (1)H chemical shifts to the indirectly detected wideline MAS powder patterns of dipolar coupled hetero-nuclei. The D-HMQC pulse sequence enables broadband excitation of the wideline hetero-nuclear NMR spectrum and provides higher sensitivity by detecting the narrower and more sensitive (1)H NMR signal. This approach is demonstrated for the rapid acquisition of 2D (1)H detected (195)Pt solid-state NMR spectra of cisplatin and transplatin and the (71)Ga solid-state NMR spectrum of a self-assembled Ga coordination polymer of unconfirmed structure. This approach should be broadly applicable for the rapid acquisition of wideline MAS solid-state NMR spectra of moderately abundant NMR nuclei.

  10. 1H to 13C Energy Transfer in Solid State NMR Spectroscopy of Natural Organic Systems

    NASA Astrophysics Data System (ADS)

    Berns, Anne E.; Conte, Pellegrino

    2010-05-01

    Cross polarization (CP) magic angle spinning (MAS) 13C-NMR spectroscopy is a solid state NMR technique widely used to study chemical composition of organic materials with low or no solubility in the common deuterated solvents used to run liquid state NMR experiments. Based on the magnetization transfer from abundant nuclei (with spin of 1 -2) having a high gyromagnetic ratio (γ), such as protons, to the less abundant 13C nuclei with low γ values, 13C-CPMAS NMR spectroscopy is often applied in environmental chemistry to obtain quantitative information on the chemical composition of natural organic matter (NOM) (Conte et al., 2004), although its quantitative assessment is still matter of heavy debates. Many authors (Baldock et al., 1997; Conte et al., 1997, 2002; Dria et al., 2002; Kiem et al., 2000; Kögel-Knabner, 2000; Preston, 2001), reported that the application of appropriate instrument setup as well as the use of special pulse sequences and correct spectra elaboration may provide signal intensities that are directly proportional to the amount of nuclei creating a NMR signal. However, many other papers dealt with the quantitative unsuitability of 13C-CPMAS NMR spectroscopy. Among those, Mao et al. (2000), Smernik and Oades (2000 a,b), and Preston (2001) reported that cross-polarized NMR techniques may fail in a complete excitation of the 13C nuclei. In fact, the amount of observable carbons via 13C-CPMAS NMR spectroscopy appeared, in many cases, lower than that measured by a direct observation of the 13C nuclei. As a consequence, cross-polarized NMR techniques may provide spectra where signal distribution may not be representative of the quantitative distribution of the different natural organic matter components. Cross-polarization is obtained after application of an initial 90° x pulse on protons and a further spin lock pulse (along the y axis) having a fixed length (contact time) for both nuclei (1H and 13C) once the Hartmann-Hahn condition is matched

  11. Immobilization of soluble protein complexes in MAS solid-state NMR: Sedimentation versus viscosity.

    PubMed

    Sarkar, Riddhiman; Mainz, Andi; Busi, Baptiste; Barbet-Massin, Emeline; Kranz, Maximilian; Hofmann, Thomas; Reif, Bernd

    2016-01-01

    In recent years, MAS solid-state NMR has emerged as a technique for the investigation of soluble protein complexes. It was found that high molecular weight complexes do not need to be crystallized in order to obtain an immobilized sample for solid-state NMR investigations. Sedimentation induced by sample rotation impairs rotational diffusion of proteins and enables efficient dipolar coupling based cross polarization transfers. In addition, viscosity contributes to the immobilization of the molecules in the sample. Natural Deep Eutectic Solvents (NADES) have very high viscosities, and can replace water in living organisms. We observe a considerable amount of cross polarization transfers for NADES solvents, even though their molecular weight is too low to yield significant sedimentation. We discuss how viscosity and sedimentation both affect the quality of the obtained experimental spectra. The FROSTY/sedNMR approach holds the potential to study large protein complexes, which are otherwise not amenable for a structural characterization using NMR. We show that using this method, backbone assignments of the symmetric proteasome activator complex (1.1MDa), and high quality correlation spectra of non-symmetric protein complexes such as the prokaryotic ribosome 50S large subunit binding to trigger factor (1.4MDa) are obtained.

  12. Solid-state NMR characterization of 69Ga and 71Ga in crystalline solids.

    PubMed

    Ash, Jason T; Grandinetti, Philip J

    2006-09-01

    Gallium model systems containing four- and six-coordinate gallium sites have been investigated using solid-state NMR. Measurement of the isotropic chemical shift and electric field gradient (EFG) have been performed at 9.4 T on alpha-Ga2O3, beta-Ga2O3, LiGaO2, NaGaO2, KGaO2, Ga2(SO4)3, and LaGaO3 using a variety of techniques on both NMR active nuclei (69Ga and 71Ga) including static, high speed magic-angle spinning (MAS), satellite transition (ST) spectroscopy, and rotor-assisted population transfer (RAPT). The chemical shift is found to correlate well with the coordination number, with four-coordinate gallium having values of approximately 50 ppm and six-coordinate gallium having values near 225 ppm (referenced to 1 M gallium nitrate solution). The magnitude of the EFG is found to be correlated to the distortion of the gallium polyhedra, with the strained systems having EFGs of 3 x 10(21) Vm(-2) or more, while the less strained systems have values of 1.5 x 10(21) Vm(-2) or less. A plot of chemical shift versus EFG suggests that solid-state NMR of gallium oxyanions can be more discriminating than liquid state NMR chemical shifts alone.

  13. Stacking structure of confined 1-butanol in SBA-15 investigated by solid-state NMR spectroscopy.

    PubMed

    Lin, Yun-Chih; Chou, Hung-Lung; Sarma, Loka Subramanyam; Hwang, Bing-Joe

    2009-10-12

    Understanding the complex thermodynamic behavior of confined amphiphilic molecules in biological or mesoporous hosts requires detailed knowledge of the stacking structures. Here, we present detailed solid-state NMR spectroscopic investigations on 1-butanol molecules confined in the hydrophilic mesoporous SBA-15 host. A range of NMR spectroscopic measurements comprising of (1)H spin-lattice (T(1)), spin-spin (T(2)) relaxation, (13)C cross-polarization (CP), and (1)H,(1)H two-dimensional nuclear Overhauser enhancement spectroscopy ((1)H,(1)H 2D NOESY) with the magic angle spinning (MAS) technique as well as static wide-line (2)H NMR spectra have been used to investigate the dynamics and to observe the stacking structure of confined 1-butanol in SBA-15. The results suggest that not only the molecular reorientation but also the exchange motions of confined molecules of 1-butanol are extremely restricted in the confined space of the SBA-15 pores. The dynamics of the confined molecules of 1-butanol imply that the (1)H,(1)H 2D NOESY should be an appropriate technique to observe the stacking structure of confined amphiphilc molecules. This study is the first to observe that a significant part of confined 1-butanol molecules are orientated as tilted bilayered structures on the surface of the host SBA-15 pores in a time-average state by solid-state NMR spectroscopy with the (1)H,(1)H 2D NOESY technique.

  14. Quantitative identification of metastable magnesium carbonate minerals by solid-state 13C NMR spectroscopy.

    PubMed

    Moore, Jeremy K; Surface, J Andrew; Brenner, Allison; Wang, Louis S; Skemer, Philip; Conradi, Mark S; Hayes, Sophia E

    2015-01-06

    In the conversion of CO2 to mineral carbonates for the permanent geosequestration of CO2, there are multiple magnesium carbonate phases that are potential reaction products. Solid-state (13)C NMR is demonstrated as an effective tool for distinguishing magnesium carbonate phases and quantitatively characterizing magnesium carbonate mixtures. Several of these mineral phases include magnesite, hydromagnesite, dypingite, and nesquehonite, which differ in composition by the number of waters of hydration or the number of crystallographic hydroxyl groups. These carbonates often form in mixtures with nearly overlapping (13)C NMR resonances which makes their identification and analysis difficult. In this study, these phases have been investigated with solid-state (13)C NMR spectroscopy, including both static and magic-angle spinning (MAS) experiments. Static spectra yield chemical shift anisotropy (CSA) lineshapes that are indicative of the site-symmetry variations of the carbon environments. MAS spectra yield isotropic chemical shifts for each crystallographically inequivalent carbon and spin-lattice relaxation times, T1, yield characteristic information that assist in species discrimination. These detailed parameters, and the combination of static and MAS analyses, can aid investigations of mixed carbonates by (13)C NMR.

  15. Ceramide – Lipid Interactions studied by MD Simulations and Solid-State NMR

    PubMed Central

    Dutagaci, Bercem; Becker-Baldus, Johanna; Faraldo-Gómez, José D.; Glaubitz, Clemens

    2014-01-01

    Ceramides play a key modulatory role in many cellular processes, which results from their effect on the structure and dynamics of biological membranes. In this study, we investigate the influence of C16-ceramide (C16) on the biophysical properties of DMPC lipid bilayers using solid-state NMR and atomistic molecular dynamics (MD) simulations. MD simulations and NMR measurements were carried out for a pure DMPC bilayer and for a 20% DMPC-C16 mixture. Calculated key structural properties, namely area per lipid, chain order parameters, and mass density profiles, indicate that C16 has an ordering effect on the DMPC bilayer. Furthermore, the simulations predict that specific hydrogen-bonds form between DMPC and C16 molecules. Multi-nuclear solid-state NMR was used to verify these theoretical predictions. Chain order parameters extracted from 13C-1H dipole couplings were measured for both lipid and ceramide and follow the trend suggested by the MD simulations. Furthermore, 1H-MAS NMR experiments showed a direct contact between ceramide and lipids. PMID:24882733

  16. Application and Reliability of Solid-State NMR in Environmental Sciences

    NASA Astrophysics Data System (ADS)

    Knicker, Heike

    2010-05-01

    For the characterization of soil organic matter, a suite of analytical approaches are available. Chemical degradative methods involve an extraction scheme with which the soluble part of the mixture is isolated and analyzed by colorimetrical or chromatographic means. Macromolecular structures can be subjected to thermolytic or combined thermochemolytic degradation. Because secondary reactions (rearrangement, cracking, hydrogenation and polymerization) in a heterogeneous mixture cannot be excluded, it is obvious that conclusions regarding the original structure in the macromolecular phase have to be drawn with caution. A powerful alternative represents solid-state nuclear magnetic resonance (NMR) spectroscopy, allowing the examination of the bulk sample without major pre-treatment In environmental sciences, this technique mostly involves the isotope 13C to study the chemical composition of organic matter in soils, sediments or compost to study the temporal development of humic material or chemical alterations due to variation in environmental parameters. Due to its low sensibility solid-state 15N NMR studies on such samples are only found occasionally. The emphasis of solid-state NMR spectroscopy is not only to determine the gross chemical composition of the material under study via a chemical shift assignment but also a quantitative correlation between the different signal intensities and the relative contribution of the respective C or N types to the total organic C or N content. However, despite increasing popularity, this approach is still viewed as mysterious techniques, in particular with respect to quantification. Accordingly, the purpose of this review is to give a short overview on the possibilities and limitations of this technique in environmental science and in particular for the study of soil organic matter. In general, solid-state 13C NMR spectra of soil organic matter are obtained with the cross polarization magic angle spinning (CPMAS) technique. This

  17. Combining insights from solid-state NMR and first principles calculation: applications to the 19F NMR of octafluoronaphthalene.

    PubMed

    Robbins, Andrew J; Ng, William T K; Jochym, Dominik; Keal, Thomas W; Clark, Stewart J; Tozer, David J; Hodgkinson, Paul

    2007-05-21

    Advances in solid-state NMR methodology and computational chemistry are applied to the (19)F NMR of solid octafluoronaphthalene. It is demonstrated experimentally, and confirmed by density functional theory (DFT) calculations, that the spectral resolution in the magic-angle spinning spectrum is limited by the anisotropy of the bulk magnetic susceptibility (ABMS). This leads to the unusual observation that the resolution improves as the sample is diluted. DFT calculations provide assignments of each of the peaks in the (19)F spectrum, but the predictions are close to the limits of accuracy and correlation information from 2-D NMR is invaluable in confirming the assignments. The effects of non-Gaussian lineshapes on the use of 2-D NMR for mapping correlations of spectral frequencies (e.g. due to the ABMS) are also discussed.

  18. Solid-state NMR spectroscopy of the quadrupolar halogens: chlorine-35/37, bromine-79/81, and iodine-127.

    PubMed

    Bryce, David L; Sward, Gregory D

    2006-04-01

    A thorough review of 35/37Cl, 79/81Br, and 127I solid-state nuclear magnetic resonance (SSNMR) data is presented. Isotropic chemical shifts (CS), quadrupolar coupling constants, and other available information on the magnitude and orientation of the CS and electric field gradient (EFG) tensors for chlorine, bromine, and iodine in diverse chemical compounds is tabulated on the basis of over 200 references. Our coverage is through July 2005. Special emphasis is placed on the information available from the study of powdered diamagnetic solids in high magnetic fields. Our survey indicates a recent notable increase in the number of applications of solid-state quadrupolar halogen NMR, particularly 35Cl NMR, as high magnetic fields have become more widely available to solid-state NMR spectroscopists. We conclude with an assessment of possible future directions for research involving 35/37Cl, 79/81Br, and 127I solid-state NMR spectroscopy.

  19. Structure determination of helical filaments by solid-state NMR spectroscopy

    PubMed Central

    Ahmed, Mumdooh; Spehr, Johannes; König, Renate; Lünsdorf, Heinrich; Rand, Ulfert; Lührs, Thorsten; Ritter, Christiane

    2016-01-01

    The controlled formation of filamentous protein complexes plays a crucial role in many biological systems and represents an emerging paradigm in signal transduction. The mitochondrial antiviral signaling protein (MAVS) is a central signal transduction hub in innate immunity that is activated by a receptor-induced conversion into helical superstructures (filaments) assembled from its globular caspase activation and recruitment domain. Solid-state NMR (ssNMR) spectroscopy has become one of the most powerful techniques for atomic resolution structures of protein fibrils. However, for helical filaments, the determination of the correct symmetry parameters has remained a significant hurdle for any structural technique and could thus far not be precisely derived from ssNMR data. Here, we solved the atomic resolution structure of helical MAVSCARD filaments exclusively from ssNMR data. We present a generally applicable approach that systematically explores the helical symmetry space by efficient modeling of the helical structure restrained by interprotomer ssNMR distance restraints. Together with classical automated NMR structure calculation, this allowed us to faithfully determine the symmetry that defines the entire assembly. To validate our structure, we probed the protomer arrangement by solvent paramagnetic resonance enhancement, analysis of chemical shift differences relative to the solution NMR structure of the monomer, and mutagenesis. We provide detailed information on the atomic contacts that determine filament stability and describe mechanistic details on the formation of signaling-competent MAVS filaments from inactive monomers. PMID:26733681

  20. Solid-state NMR studies of theophylline co-crystals with dicarboxylic acids.

    PubMed

    Pindelska, Edyta; Sokal, Agnieszka; Szeleszczuk, Lukasz; Pisklak, Dariusz Maciej; Kolodziejski, Waclaw

    2014-11-01

    In this work, three polycrystalline materials containing co-crystals of theophylline with malonic, maleic, and glutaric acids were studied using (13)C, (15)N and (1)H solid-state NMR and FT-IR spectroscopy. The NMR assignments were supported by gauge including projector augmented waves (GIPAW) calculations of chemical shielding, performed using X-ray determined geometry. The experimental (13)C cross polarization/magic angle spinning (CP/MAS) NMR results and the calculated isotropic chemical shifts were in excellent agreement. A rapid and convenient method for theophylline co-crystals crystal structure analysis has been proposed for co-crystals, which are potentially new APIs. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. Intercalation complex of proflavine with DNA: Structure and dynamics by solid-state NMR

    SciTech Connect

    Tang, Pei; Juang, Chilong; Harbison, G.S. )

    1990-07-06

    The structure of the complex formed between the intercalating agent proflavine and fibrous native DNA was studied by one- and two-dimensional high-resolution solid-state nuclear magnetic resonance (NMR). Carbon-13-labeled proflavine was used to show that the drug is stacked with the aromatic ring plane perpendicular to the fiber axis and that it is essentially immobile. Natural abundance carbon-13 NMR of the DNA itself shows that proflavine binding does not change the puckering of the deoxyribose ring. However, phosphorus-31 NMR spectra show profound changes in the orientation of the phosphodiester grouping on proflavine binding, with some of the phosphodiesters tilting almost parallel to the helix axis, and a second set almost perpendicular. The first group to the phosphodiesters probably spans the intercalation sites, whereas the tilting of the second set likely compensates for the unwinding of the DNA by the intercalator.

  2. Probing the surface structure of divalent transition metals using surface specific solid-state NMR spectroscopy.

    PubMed

    Mason, Harris E; Harley, Stephen J; Maxwell, Robert S; Carroll, Susan A

    2012-03-06

    Environmental and geochemical systems containing paramagnetic species could benefit by using nuclear magnetic resonance (NMR) spectroscopy due to the sensitivity of the spectral response to small amounts paramagnetic interactions. In this study, we apply commonly used solid-state NMR spectroscopic methods combined with chemometrics analysis to probe sorption behavior of the paramagnetic cations Cu(2+) and Ni(2+)at the amorphous silica surface. We exploit the unique properties of paramagnets to derive meaningful structural information in these systems at low, environmentally relevant cation surface loadings by comparing the NMR response of sorption samples to paramagnetic free samples. These data suggest that a simple sorption model where the cation sorbs as inner sphere complexes at negatively charged, deprotonated silanol sites is appropriate. These results help constrain sorption models that are used to describe metal fate and transport.

  3. Exploring electrolyte organization in supercapacitor electrodes with solid-state NMR

    NASA Astrophysics Data System (ADS)

    Deschamps, Michaël; Gilbert, Edouard; Azais, Philippe; Raymundo-Piñero, Encarnación; Ammar, Mohammed Ramzi; Simon, Patrick; Massiot, Dominique; Béguin, François

    2013-04-01

    Supercapacitors are electrochemical energy-storage devices that exploit the electrostatic interaction between high-surface-area nanoporous electrodes and electrolyte ions. Insight into the molecular mechanisms at work inside supercapacitor carbon electrodes is obtained with 13C and 11B ex situ magic-angle spinning nuclear magnetic resonance (MAS-NMR). In activated carbons soaked with an electrolyte solution, two distinct adsorption sites are detected by NMR, both undergoing chemical exchange with the free electrolyte molecules. On charging, anions are substituted by cations in the negative carbon electrode and cations by anions in the positive electrode, and their proportions in each electrode are quantified by NMR. Moreover, acetonitrile molecules are expelled from the adsorption sites at the negative electrode alone. Two nanoporous carbon materials were tested, with different nanotexture orders (using Raman and 13C MAS-NMR spectroscopies), and the more disordered carbon shows a better capacitance and a better tolerance to high voltages.

  4. Investigation of ligand-receptor systems by high-resolution solid-state NMR: recent progress and perspectives.

    PubMed

    Luca, Sorin; Heise, Henrike; Lange, Adam; Baldus, Marc

    2005-06-01

    Solid-state Nuclear Magnetic Resonance (NMR) provides a general method to study molecular structure and dynamics in a non-crystalline and insoluble environment. We discuss the latest methodological progress to construct 3D molecular structures from solid-state NMR data obtained under magic-angle-spinning conditions. As shown for the neurotensin/NTS-1 system, these methods can be readily applied to the investigation of ligand-binding to G-protein coupled receptors.

  5. Freezing point depression of water in phospholipid membranes: a solid-state NMR study.

    PubMed

    Lee, Dong-Kuk; Kwon, Byung Soo; Ramamoorthy, Ayyalusamy

    2008-12-02

    Lipid-water interaction plays an important role in the properties of lipid bilayers, cryoprotectants, and membrane-associated peptides and proteins. The temperature at which water bound to lipid bilayers freezes is lower than that of free water. Here, we report a solid-state NMR investigation on the freezing point depression of water in phospholipid bilayers in the presence and absence of cholesterol. Deuterium NMR spectra at different temperatures ranging from -75 to + 10 degrees C were obtained from fully (2)H2O-hydrated POPC (1-palmitoyl-2-oleoylphosphatidylcholine) multilamellar vesicles (MLVs), prepared with and without cholesterol, to determine the freezing temperature of water and the effect of cholesterol on the freezing temperature of water in POPC bilayers. Our 2H NMR experiments reveal the motional behavior of unfrozen water molecules in POPC bilayers even at temperatures significantly below 0 degrees C and show that the presence of cholesterol further lowered the freezing temperature of water in POPC bilayers. These results suggest that in the presence of cholesterol the fluidity and dynamics of lipid bilayers can be retained even at very low temperatures as exist in the liquid crystalline phase of the lipid. Therefore, bilayer samples prepared with a cryoprotectant like cholesterol should enable the performance of multidimensional solid-state NMR experiments to investigate the structure, dynamics, and topology of membrane proteins at a very low temperature with enhanced sample stability and possibly a better sensitivity. Phosphorus-31 NMR data suggest that lipid bilayers can be aligned at low temperatures, while 15N NMR experiments demonstrate that such aligned samples can be used to enhance the signal-to-noise ratio of is 15N chemical shift spectra of a 37-residue human antimicrobial peptide, LL-37.

  6. Freezing Point Depression of Water in Phospholipid Membranes — A Solid-State NMR Study

    PubMed Central

    Lee, Dong-Kuk; Kwon, ByungSoo; Ramamoorthy, Ayyalusamy

    2009-01-01

    Lipid-water interaction plays an important role in the properties of lipid bilayers, cryoprotectants, and membrane-associated peptides and proteins. The temperature at which water bound to lipid bilayers freezes is lower than that of free water. Here, we report a solid-state NMR investigation on the freezing point depression of water in phospholipid bilayers in the presence and absence of cholesterol. Deuterium NMR spectra at different temperatures ranging from -75 to +10°C were obtained from fully 2H2O-hydrated POPC (1-palmitoyl-2-oleoyl-phosphatidylcholine) multilamellar vesicles (MLVs), prepared with and without cholesterol, to determine the freezing temperature of water and the effect of cholesterol on the freezing temperature of water in POPC bilayers. Our 2H NMR experiments reveal the motional behavior of unfrozen water molecules in POPC bilayers even at temperatures significantly below 0°C and show that the presence of cholesterol further lowered the freezing temperature of water in POPC bilayers. These results suggest that in the presence of cholesterol the fluidity and dynamics of lipid bilayers can be retained even at very low temperatures as exist in the liquid crystalline phase of the lipid. Therefore, bilayer samples prepared with a cryoprotectant like cholesterol should enable the performance of multidimensional solid-state NMR experiments to investigate the structure, dynamics, and topology of membrane proteins at a very low temperature with enhanced sample stability and possibly a better sensitivity. Phosphorus-31 NMR data suggest that lipid bilayers can be aligned at low temperatures, while 15N NMR experiments demonstrate that such aligned samples can be used to enhance the signal-to-noise ratio of 15N chemical shift spectra of a 37-residue human antimicrobial peptide, LL-37. PMID:18991419

  7. Spatially resolved solid-state 1H NMR for evaluation of gradient-composition polymeric libraries.

    PubMed

    Leisen, Johannes; Gomez, Ismael J; Roper, John A; Meredith, J Carson; Beckham, Haskell W

    2012-07-09

    Polyurethane libraries consisting of films with composition gradients of aliphatic polyisocyanate and hydroxy-terminated polyacrylate resin were characterized using methods of (1)H NMR microimaging (i.e., magnetic resonance imaging, (MRI)) and solid-state NMR. Molecular mobilities and underlying structural information were extracted as a function of the relative content of each of the two components. Routine NMR microimaging using the spin-echo sequence only allows investigations of transverse relaxation of magnetization at echo times >2 ms. A single-exponential decay was found, which is likely due to free, noncross-linked polymer chains. The mobility of these chains decreases with increasing content of the aliphatic polyisocyanate. The concept of a 1D NMR profiler is introduced as a novel modality for library screening, which allows the convenient measurement of static solid-state NMR spectra as a function of spatial location along a library sample that is repositioned in the rf coil between experiments. With this setup the complete transverse relaxation function was measured using Bloch decays and spin echoes. For all positions within the gradient-composition film, relaxation data consisted of at least three components that were attributed to a rigid highly cross-linked resin, an intermediate cross-linked but mobile constituent, and the highly mobile free polymer chains (the latter is also detectable by MRI). Analysis of this overall relaxation function measured via Bloch decays and spin echoes revealed only minor changes in the mobilities of the individual fractions. Findings with respect to the most mobile components are consistent with the results obtained by NMR microimaging. The major effect is the significant increase in the rigid-component fraction with the addition of the hydroxy-terminated polyacrylate resin.

  8. Solid-state 207Pb NMR studies of mixed lead halides, PbFX (X=Cl, Br, or I).

    PubMed

    Glatfelter, Alicia; Dybowski, Cecil; Kragten, David D; Bai, Shi; Perry, Dale L; Lockard, Jenny

    2007-04-01

    Solid-state 207Pb NMR studies have been conducted on mixed lead(II) halides of the type PbFX, where X=Cl, Br, or I. NMR data for the mixed halides are compared to the solid-state NMR data for the divalent, binary lead halides, PbX2 (X=F, Cl, Br, I). The NMR data are evaluated in the context of the structures of the compounds and the effects of the mixed halides on the electronic structure of the divalent lead. Data sets for the mixed halides are discussed and compared to those for the regular lead(II) halides.

  9. Toxin-induced conformational changes in a potassium channel revealed by solid-state NMR

    NASA Astrophysics Data System (ADS)

    Lange, Adam; Giller, Karin; Hornig, Sönke; Martin-Eauclaire, Marie-France; Pongs, Olaf; Becker, Stefan; Baldus, Marc

    2006-04-01

    The active site of potassium (K+) channels catalyses the transport of K+ ions across the plasma membrane-similar to the catalytic function of the active site of an enzyme-and is inhibited by toxins from scorpion venom. On the basis of the conserved structures of K+ pore regions and scorpion toxins, detailed structures for the K+ channel-scorpion toxin binding interface have been proposed. In these models and in previous solution-state nuclear magnetic resonance (NMR) studies using detergent-solubilized membrane proteins, scorpion toxins were docked to the extracellular entrance of the K+ channel pore assuming rigid, preformed binding sites. Using high-resolution solid-state NMR spectroscopy, here we show that high-affinity binding of the scorpion toxin kaliotoxin to a chimaeric K+ channel (KcsA-Kv1.3) is associated with significant structural rearrangements in both molecules. Our approach involves a combined analysis of chemical shifts and proton-proton distances and demonstrates that solid-state NMR is a sensitive method for analysing the structure of a membrane protein-inhibitor complex. We propose that structural flexibility of the K+ channel and the toxin represents an important determinant for the high specificity of toxin-K+ channel interactions.

  10. Motion-adapted pulse sequences for oriented sample (OS) solid-state NMR of biopolymers

    PubMed Central

    Lu, George J.; Opella, Stanley J.

    2013-01-01

    One of the main applications of solid-state NMR is to study the structure and dynamics of biopolymers, such as membrane proteins, under physiological conditions where the polypeptides undergo global motions as they do in biological membranes. The effects of NMR radiofrequency irradiations on nuclear spins are strongly influenced by these motions. For example, we previously showed that the MSHOT-Pi4 pulse sequence yields spectra with resonance line widths about half of those observed using the conventional pulse sequence when applied to membrane proteins undergoing rapid uniaxial rotational diffusion in phospholipid bilayers. In contrast, the line widths were not changed in microcrystalline samples where the molecules did not undergo global motions. Here, we demonstrate experimentally and describe analytically how some Hamiltonian terms are susceptible to sample motions, and it is their removal through the critical π/2 Z-rotational symmetry that confers the “motion adapted” property to the MSHOT-Pi4 pulse sequence. This leads to the design of separated local field pulse sequence “Motion-adapted SAMPI4” and is generalized to an approach for the design of decoupling sequences whose performance is superior in the presence of molecular motions. It works by cancelling the spin interaction by explicitly averaging the reduced Wigner matrix to zero, rather than utilizing the 2π nutation to average spin interactions. This approach is applicable to both stationary and magic angle spinning solid-state NMR experiments. PMID:24006989

  11. Bacteriophage Tail-Tube Assembly Studied by Proton-Detected 4D Solid-State NMR

    DOE PAGES

    Zinke, Maximilian; Fricke, Pascal; Samson, Camille; ...

    2017-07-07

    Obtaining unambiguous resonance assignments remains a major bottleneck in solid-state NMR studies of protein structure and dynamics. Particularly for supramolecular assemblies with large subunits (>150 residues), the analysis of crowded spectral data presents a challenge, even if three-dimensional (3D) spectra are used. Here, we present a proton-detected 4D solid-state NMR assignment procedure that is tailored for large assemblies. The key to recording 4D spectra with three indirect carbon or nitrogen dimensions with their inherently large chemical shift dispersion lies in the use of sparse non-uniform sampling (as low as 2 %). As a proof of principle, we acquired 4D (H)COCANH,more » (H)CACONH, and (H)CBCANH spectra of the 20 kDa bacteriophage tail-tube protein gp17.1 in a total time of two and a half weeks. These spectra were sufficient to obtain complete resonance assignments in a straightforward manner without use of previous solution NMR data.« less

  12. Motion-adapted pulse sequences for oriented sample (OS) solid-state NMR of biopolymers.

    PubMed

    Lu, George J; Opella, Stanley J

    2013-08-28

    One of the main applications of solid-state NMR is to study the structure and dynamics of biopolymers, such as membrane proteins, under physiological conditions where the polypeptides undergo global motions as they do in biological membranes. The effects of NMR radiofrequency irradiations on nuclear spins are strongly influenced by these motions. For example, we previously showed that the MSHOT-Pi4 pulse sequence yields spectra with resonance line widths about half of those observed using the conventional pulse sequence when applied to membrane proteins undergoing rapid uniaxial rotational diffusion in phospholipid bilayers. In contrast, the line widths were not changed in microcrystalline samples where the molecules did not undergo global motions. Here, we demonstrate experimentally and describe analytically how some Hamiltonian terms are susceptible to sample motions, and it is their removal through the critical π/2 Z-rotational symmetry that confers the "motion adapted" property to the MSHOT-Pi4 pulse sequence. This leads to the design of separated local field pulse sequence "Motion-adapted SAMPI4" and is generalized to an approach for the design of decoupling sequences whose performance is superior in the presence of molecular motions. It works by cancelling the spin interaction by explicitly averaging the reduced Wigner matrix to zero, rather than utilizing the 2π nutation to average spin interactions. This approach is applicable to both stationary and magic angle spinning solid-state NMR experiments.

  13. Computer-intensive simulation of solid-state NMR experiments using SIMPSON

    NASA Astrophysics Data System (ADS)

    Tošner, Zdeněk; Andersen, Rasmus; Stevensson, Baltzar; Edén, Mattias; Nielsen, Niels Chr.; Vosegaard, Thomas

    2014-09-01

    Conducting large-scale solid-state NMR simulations requires fast computer software potentially in combination with efficient computational resources to complete within a reasonable time frame. Such simulations may involve large spin systems, multiple-parameter fitting of experimental spectra, or multiple-pulse experiment design using parameter scan, non-linear optimization, or optimal control procedures. To efficiently accommodate such simulations, we here present an improved version of the widely distributed open-source SIMPSON NMR simulation software package adapted to contemporary high performance hardware setups. The software is optimized for fast performance on standard stand-alone computers, multi-core processors, and large clusters of identical nodes. We describe the novel features for fast computation including internal matrix manipulations, propagator setups and acquisition strategies. For efficient calculation of powder averages, we implemented interpolation method of Alderman, Solum, and Grant, as well as recently introduced fast Wigner transform interpolation technique. The potential of the optimal control toolbox is greatly enhanced by higher precision gradients in combination with the efficient optimization algorithm known as limited memory Broyden-Fletcher-Goldfarb-Shanno. In addition, advanced parallelization can be used in all types of calculations, providing significant time reductions. SIMPSON is thus reflecting current knowledge in the field of numerical simulations of solid-state NMR experiments. The efficiency and novel features are demonstrated on the representative simulations.

  14. Computer-intensive simulation of solid-state NMR experiments using SIMPSON.

    PubMed

    Tošner, Zdeněk; Andersen, Rasmus; Stevensson, Baltzar; Edén, Mattias; Nielsen, Niels Chr; Vosegaard, Thomas

    2014-09-01

    Conducting large-scale solid-state NMR simulations requires fast computer software potentially in combination with efficient computational resources to complete within a reasonable time frame. Such simulations may involve large spin systems, multiple-parameter fitting of experimental spectra, or multiple-pulse experiment design using parameter scan, non-linear optimization, or optimal control procedures. To efficiently accommodate such simulations, we here present an improved version of the widely distributed open-source SIMPSON NMR simulation software package adapted to contemporary high performance hardware setups. The software is optimized for fast performance on standard stand-alone computers, multi-core processors, and large clusters of identical nodes. We describe the novel features for fast computation including internal matrix manipulations, propagator setups and acquisition strategies. For efficient calculation of powder averages, we implemented interpolation method of Alderman, Solum, and Grant, as well as recently introduced fast Wigner transform interpolation technique. The potential of the optimal control toolbox is greatly enhanced by higher precision gradients in combination with the efficient optimization algorithm known as limited memory Broyden-Fletcher-Goldfarb-Shanno. In addition, advanced parallelization can be used in all types of calculations, providing significant time reductions. SIMPSON is thus reflecting current knowledge in the field of numerical simulations of solid-state NMR experiments. The efficiency and novel features are demonstrated on the representative simulations.

  15. Solid-State NMR Studies of HIV-1 Capsid Protein Assemblies

    SciTech Connect

    Han, Yun; Ahn, Jinwoo; Concel, Jason; Byeon, In-Ja L.; Gronenborn, Angela M.; Yang, Jun; Polenova, Tatyana E.

    2010-02-17

    In mature HIV-1 virions, the 26.6 kDa CA protein is assembled into a characteristic cone-shaped core (capsid) that encloses the RNA viral genome. The assembled capsid structure is best described by a fullerene cone model that is made up from a hexameric lattice containing a variable number of CA pentamers, thus allowing for closure of tubular or conical structures. In this paper, we present a solid-state NMR analysis of the wild-type HIV-1 CA protein, prepared as conical and spherical assemblies that are stable and are not affected by magic angle spinning of the samples at frequencies between 10 and 25 kHz. Multidimensional homo- and heteronuclear correlation spectra of CA assemblies of uniformly 13C,15Nlabeled CA exhibit narrow lines, indicative of the conformational homogeneity of the protein in these assemblies. For the conical assemblies, partial residue-specific resonance assignments were obtained. Analysis of the NMR spectra recorded for the conical and spherical assemblies indicates that the CA protein structure is not significantly different in the different morphologies. The present results demonstrate that the assemblies of CA protein are amenable to detailed structural analysis by solid-state NMR spectroscopy.

  16. Solid-state (19)F-NMR of peptides in native membranes.

    PubMed

    Koch, Katja; Afonin, Sergii; Ieronimo, Marco; Berditsch, Marina; Ulrich, Anne S

    2012-01-01

    To understand how membrane-active peptides (MAPs) function in vivo, it is essential to obtain structural information about them in their membrane-bound state. Most biophysical approaches rely on the use of bilayers prepared from synthetic phospholipids, i.e. artificial model membranes. A particularly successful structural method is solid-state NMR, which makes use of macroscopically oriented lipid bilayers to study selectively isotope-labelled peptides. Native biomembranes, however, have a far more complex lipid composition and a significant non-lipidic content (protein and carbohydrate). Model membranes, therefore, are not really adequate to address questions concerning for example the selectivity of these membranolytic peptides against prokaryotic vs eukaryotic cells, their varying activities against different bacterial strains, or other related biological issues.Here, we discuss a solid-state (19)F-NMR approach that has been developed for structural studies of MAPs in lipid bilayers, and how this can be translated to measurements in native biomembranes. We review the essentials of the methodology and discuss key objectives in the practice of (19)F-labelling of peptides. Furthermore, the preparation of macroscopically oriented biomembranes on solid supports is discussed in the context of other membrane models. Two native biomembrane systems are presented as examples: human erythrocyte ghosts as representatives of eukaryotic cell membranes, and protoplasts from Micrococcus luteus as membranes from Gram-positive bacteria. Based on our latest experimental experience with the antimicrobial peptide gramicidin S, the benefits and some implicit drawbacks of using such supported native membranes in solid-state (19)F-NMR analysis are discussed.

  17. Experiments Optimized for Magic Angle Spinning and Oriented Sample Solid-State NMR of Proteins

    PubMed Central

    Das, Bibhuti B.; Lin, Eugene C.; Opella, Stanley J.

    2013-01-01

    Structure determination by solid-state NMR of proteins is rapidly advancing as result of recent developments of samples, experimental methods, and calculations. There are a number of different solid-state NMR approaches that utilize stationary, aligned samples or magic angle spinning of unoriented ‘powder’ samples, and depending on the sample and the experimental method can emphasize the measurement of distances or angles, ideally both, as sources of structural constraints. Multi-dimensional correlation spectroscopy of low-gamma nuclei such as 15N and 13C is an important step for making resonance assignments and measurements of angular restraints in membrane proteins. However, the efficiency of coherence transfer predominantly depends upon the strength of dipole-dipole interaction, and this can vary from site to site and between sample alignments, for example, during the mixing of 13C and 15N magnetization in stationary aligned and in magic angle spinning samples. Here, we demonstrate that the efficiency of polarization transfer can be improved by using adiabatic demagnetization and remagnetization techniques on stationary aligned samples; and proton assisted insensitive nuclei cross-polarization in magic angle sample spinning samples. Adiabatic cross-polarization technique provides an alternative mechanism for spin-diffusion experiments correlating 15N/15N and 15N/13C chemical shifts over large distances. Improved efficiency in cross-polarization with 40% – 100% sensitivity enhancements are observed in proteins and single crystals, respectively. We describe solid-state NMR experimental techniques that are optimal for membrane proteins in liquid crystalline phospholipid bilayers under physiological conditions. The techniques are illustrated with data from both single crystals of peptides and of membrane proteins in phospholipid bilayers. PMID:24044695

  18. Boric acid adsorption on humic acids: Ab initio calculation of structures, stabilities, 11B NMR and 11B, 10B isotopic fractionations of surface complexes

    NASA Astrophysics Data System (ADS)

    Tossell, J. A.

    2006-10-01

    Boric acid, B(OH) 3, forms complexes in aqueous solution with a number of bidentate O-containing ligands, HL -, where H 2L is C 2O 4H 2 (oxalic acid), C 3O 4H 4 (malonic acid), C 2H 6O 2 (ethylene glycol), C 6H 6O 2 (catechol), C 10H 8O 2 (dioxynaphthalene) and C 2O 3H 4 (glycolic acid). McElligott and Byrne [McElligott, S., Byrne, R.H., 1998. Interaction of B(OH)30 and HCO3- in seawater: Formation of B(OH)CO3-. Aquat. Geochem.3, 345-356.] have also found B(OH) 3 to form an aqueous complex with HCO3-1. Recently Lemarchand et al. [Lemarchand, E., Schott, J., Gaillardeet, J., 2005. Boron isotopic fractionation related to boron sorption on humic acid and the structure of surface complexes formed. Geochim. Cosmochim. Acta69, 3519-3533] have studied the formation of surface complexes of B(OH) 3 on humic acid, determining 11B NMR shifts and fitted values of formation constants, and 11B, 10B isotope fractionations for a number of surface complexation models. Their work helps to clarify both the nature of the interaction of boric acid with the functional groups in humic acid and the nature of some of these coordinating sites on the humic acid. The determination of isotope fractionations may be seen as a form of vibrational spectroscopy, using the fractionating element as a local probe of the vibrational spectrum. We have calculated quantum mechanically the structures, stabilities, vibrational spectra, 11B NMR spectra and 11B, 10B isotope fractionations of a number of complexes B(OH) 2L - formed by reactions of the type: B(OH)3+HL-⇒B(OH)2L+HO using a 6-311G(d,p) basis set and the B3LYP method for determination of structures, vibrational frequencies and isotopic fractionations, the highly accurate Complete Basis Set-QB3 method for calculating the free energies and the GIAO HF method with a 6-311+G(2d,p) basis for the NMR shieldings. The calculations indicate that oxalic acid, malonic acid, catechol and glycolic acid all form stable complexes (Δ G < 0 for Reaction (1

  19. Structural rearrangements of membrane proteins probed by water-edited solid-state NMR spectroscopy.

    PubMed

    Ader, Christian; Schneider, Robert; Seidel, Karsten; Etzkorn, Manuel; Becker, Stefan; Baldus, Marc

    2009-01-14

    We show that water-edited solid-state NMR spectroscopy allows for probing global protein conformation and residue-specific solvent accessibility in a lipid bilayer environment. The transfer dynamics can be well described by a general time constant, irrespective of protein topology and lipid environment. This approach was used to follow structural changes in response to protein function in the chimeric potassium channel KcsA-Kv1.3. Data obtained as a function of pH link earlier biochemical data to changes in protein structure in a functional bilayer setting.

  20. 6-Aminopenicillanic acid revisited: A combined solid state NMR and in silico refinement

    NASA Astrophysics Data System (ADS)

    Aguiar, Daniel Lima Marques de; San Gil, Rosane Aguiar da Silva; Alencastro, Ricardo Bicca de; Souza, Eugenio Furtado de; Borré, Leandro Bandeira; Vaiss, Viviane da Silva; Leitão, Alexandre Amaral

    2016-09-01

    13C/15N (experimental and ab initio) solid-state NMR was used to achieve an affordable way to improve hydrogen refinement of 6-aminopenicillanic acid (6-APA) structure. The lattice effect on the isotropic chemical shifts was probed by using two different magnetic shielding calculations: isolated molecules and periodic crystal structure. The electron density difference maps of optimized and non-optimized structures were calculated in order to investigate the interactions inside the 6-APA unit cell. The 13C and 15N chemical shifts assignments were unambiguously stablished. In addition, some of the literature 13C resonances ambiguities could be properly solved.

  1. Efficient solid state NMR powder simulations using SMP and MPP parallel computation

    NASA Astrophysics Data System (ADS)

    Kristensen, Jørgen Holm; Farnan, Ian

    2003-04-01

    Methods for parallel simulation of solid state NMR powder spectra are presented for both shared and distributed memory parallel supercomputers. For shared memory architectures the performance of simulation programs implementing the OpenMP application programming interface is evaluated. It is demonstrated that the design of correct and efficient shared memory parallel programs is difficult as the performance depends on data locality and cache memory effects. The distributed memory parallel programming model is examined for simulation programs using the MPI message passing interface. The results reveal that both shared and distributed memory parallel computation are very efficient with an almost perfect application speedup and may be applied to the most advanced powder simulations.

  2. Structural modeling of Vpu from HIV-1 based on solid-state NMR observables

    NASA Astrophysics Data System (ADS)

    Ahn, SeonJoo; Lim, GyuTae; Nam, Seungyoon; Lee, Jinhyuk

    2014-04-01

    Vpu is one of the accessory proteins of HIV-1, and is involved in viral particle release. Viral particle release is enhanced by two proposed functions of Vpu: (i) tetherin interaction and (ii) membrane polarization. Two Vpu functions in viral particle release are still controversial. Here, we investigated the proposed functions by extensive structural modeling of Vpu based on solid-state NMR (Nuclear Magnetic Resonance) observables. We found that Vpu can co-exist in two structural forms: left-handed and right-handed conformation. The co-existence of the two conformations provides a clue to reconcile the controversial issue of its two functions in virus particle release.

  3. Methanol carbonylation over copper-modified mordenite zeolite: A solid-state NMR study.

    PubMed

    Zhou, Lei; Li, Shenhui; Qi, Guodong; Su, Yongchao; Li, Jing; Zheng, Anmin; Yi, Xianfeng; Wang, Qiang; Deng, Feng

    2016-11-01

    The carbonylation of methanol with carbon monoxide to generate methyl acetate over Cu-H-MOR and H-MOR zeolites is studied using solid-state NMR spectroscopy. It is found that the catalytic activity of Cu-H-MOR zeolite is much higher than that of H-MOR zeolite. The presence of Cu(+) species enables the stabilization of dimethyl ether, which efficiently suppresses the hydrocarbon formation during carbonylation process over Cu-H-MOR zeolite. In addition, the carbon monoxide adsorbed on Cu(+) site is not an active species to produce either methyl acetate or acetic acid.

  4. Understanding Surface and Interfacial Chemistry in Functional Nanomaterials via Solid-State NMR.

    PubMed

    Marchetti, Alessandro; Chen, Juner; Pang, Zhenfeng; Li, Shenhui; Ling, Daishun; Deng, Feng; Kong, Xueqian

    2017-04-01

    Surface and interfacial chemistry is of fundamental importance in functional nanomaterials applied in catalysis, energy storage and conversion, medicine, and other nanotechnologies. It has been a perpetual challenge for the scientific community to get an accurate and comprehensive picture of the structures, dynamics, and interactions at interfaces. Here, some recent examples in the major disciplines of nanomaterials are selected (e.g., nanoporous materials, battery materials, nanocrystals and quantum dots, supramolecular assemblies, drug-delivery systems, ionomers, and graphite oxides) and it is shown how interfacial chemistry can be addressed through the perspective of solid-state NMR characterization techniques.

  5. Structural investigation of Lisinopril by powder X-ray diffraction and solid-state NMR

    NASA Astrophysics Data System (ADS)

    Filip, Xenia; Tripon, Carmen; Borodi, Gheorghe; Oprean, Luminiţa; Filip, Claudiu

    2009-08-01

    Structural studies on polycrystalline Lisinopril (N-N-[(s)-1-carboxy-3-phenylpropyl]-L-lysil-L-proline) are performed by combined powder X-Ray diffraction and 13C solid-state nuclear magnetic resonance (NMR). The crystal structure of this drug, used primarily for the treatment of hypertension, has not yet been determined due to the impossibility of synthesizing single crystals of sufficient quality. It is shown here that valuable insights into the crystal and molecular structure of Lisinopril can be obtained on polycrystalline powder based on the complementary character of the information provided by the two techniques.

  6. Solid-state NMR study of geopolymer prepared by sol-gel chemistry

    NASA Astrophysics Data System (ADS)

    Tsai, Yi-Ling; Hanna, John V.; Lee, Yuan-Ling; Smith, Mark E.; Chan, Jerry C. C.

    2010-12-01

    Geopolymers are a new class of materials formed by the condensation of aluminosilicates and silicates obtained from natural minerals or industrial wastes. In this work, the sol-gel method is used to synthesize precursor materials for the preparation of geopolymers. The geopolymer samples prepared by our synthetic route have been characterized by a series of physical techniques, including Fourier-transform infrared, X-ray diffraction, and multinuclear solid-state NMR. The results are very similar to those obtained for the geopolymers prepared from natural kaolinite. We believe that our synthetic approach can offer a good opportunity for the medical applications of geopolymer.

  7. Multinuclear Solid-State NMR Investigation of Hexaniobate and Hexatantalate Compounds.

    PubMed

    Deblonde, Gauthier J-P; Coelho-Diogo, Cristina; Chagnes, Alexandre; Cote, Gérard; Smith, Mark E; Hanna, John V; Iuga, Dinu; Bonhomme, Christian

    2016-06-20

    This work determines the potential of solid-state NMR techniques to probe proton, alkali, and niobium environments in Lindqvist salts. Na7HNb6O19·15H2O (1), K8Nb6O19·16H2O (2), and Na8Ta6O19·24.5H2O (3) have been studied by solid-state static and magic angle spinning (MAS) NMR at high and ultrahigh magnetic field (16.4 and 19.9 T). (1)H MAS NMR was found to be a convenient and straightforward tool to discriminate between protonated and nonprotonated clusters AxH8-xM6O19·nH2O (A = alkali ion; M = Nb, Ta). (93)Nb MAS NMR studies at different fields and MAS rotation frequencies have been performed on 1. For the first time, the contributions of NbO5Oμ2H sites were clearly distinguished from those assigned to NbO6 sites in the hexaniobate cluster. The strong broadening of the resonances obtained under MAS was interpreted by combining chemical shift anisotropy (CSA) with quadrupolar effects and by using extensive fitting of the line shapes. In order to obtain the highest accuracy for all NMR parameters (CSA and quadrupolar), (93)Nb WURST QCPMG spectra in the static mode were recorded at 16.4 T for sample 1. The (93)Nb NMR spectra were interpreted in connection with the XRD data available in the literature (i.e., fractional occupancies of the NbO5Oμ2H sites). 1D (23)Na MAS and 2D (23)Na 3QMAS NMR studies of 1 revealed several distinct sodium sites. The multiplicity of the sites was again compared to structural details previously obtained by single-crystal X-ray diffraction (XRD) studies. The (23)Na MAS NMR study of 3 confirmed the presence of a much larger distribution of sodium sites in accordance with the 10 sodium sites predicted by XRD. Finally, the effect of Nb/Ta substitutions in 1 was also probed by multinuclear MAS NMR ((1)H, (23)Na, and (93)Nb).

  8. Restoring Resolution in Biological Solid-State NMR under Conditions of Off-Magic-Angle Spinning.

    PubMed

    Sarkar, Riddhiman; Rodriguez Camargo, Diana C; Pintacuda, Guido; Reif, Bernd

    2015-12-17

    Spin-state-selective excitation (S3E) experiments allow the selection of individual transitions in a coupled two spin system. We show that in the solid state, the dipole-dipole interaction (DD) between (15)N and (1)H in a (1)H-(15)N bond and the chemical shift anisotropy (CSA) of (15)N in an amide moiety mutually cancel each other for a particular multiplet component at high field, when the sample is spun off the magic angle (Arctan [√2] = 54.74°). The accuracy of the adjustment of the spinning angle is crucial in conventional experiments. We demonstrate that for S3E experiments, the requirement to spin the sample exactly at the magic angle is not mandatory. Applications of solid state NMR in narrow bore magnets will be facilitated where the adjustment of the magic angle is often difficult. The method opens new perspectives for the development of schemes to determine distances and to quantify dynamics in the solid state.

  9. Prediction of recrystallization behavior of troglitazone/polyvinylpyrrolidone solid dispersion by solid-state NMR.

    PubMed

    Ito, Atsutoshi; Watanabe, Tomoyuki; Yada, Shuichi; Hamaura, Takeshi; Nakagami, Hiroaki; Higashi, Kenjirou; Moribe, Kunikazu; Yamamoto, Keiji

    2010-01-04

    The purpose of this study was to elaborate the relationship between the (13)C CP/MAS NMR spectra and the recrystallization behavior during the storage of troglitazone solid dispersions. The solid dispersions were prepared by either the solvent method or by co-grinding. The recrystallization behavior under storage conditions at 40 degrees C/94% RH was evaluated by the Kolmogorov-Johnson-Mehl-Avrami (KJMA) equation. Solid dispersions prepared by the solvent method or by prolonged grinding brought about inhibition of the nucleation and the nuclei growth at the same time. No differences in the PXRD profiles were found in the samples prepared by the co-grinding and solvent methods, however, (13)C CP/MAS NMR showed significant differences in the spectra. The correlation coefficients using partial least square regression analysis between the PXRD profiles and the apparent nuclei-growth constant or induction period to nucleation were 0.1305 or 0.6350, respectively. In contrast, those between the (13)C CP/MAS NMR spectra and the constant or the period were 0.9916 or 0.9838, respectively. The (13)C CP/MAS NMR spectra had good correlation with the recrystallization kinetic parameters evaluated by the KJMA equation. Consequently, solid-state NMR was judged to be a useful tool for the prediction of the recrystallization behavior of solid dispersions.

  10. Dynamics and interactions of ibuprofen in cyclodextrin nanosponges by solid-state NMR spectroscopy

    PubMed Central

    Ferro, Monica; Pastori, Nadia; Punta, Carlo; Melone, Lucio; Panzeri, Walter; Rossi, Barbara; Trotta, Francesco

    2017-01-01

    Two different formulations of cyclodextrin nanosponges (CDNS), obtained by polycondensation of β-cyclodextrin with ethylenediaminetetraacetic acid dianhydride (EDTAn), were treated with aqueous solutions of ibuprofen sodium salt (IbuNa) affording hydrogels that, after lyophilisation, gave two solid CDNS-drug formulations. 1H fast MAS NMR and 13C CP-MAS NMR spectra showed that IbuNa was converted in situ into its acidic and dimeric form (IbuH) after freeze-drying. 13C CP-MAS NMR spectra also indicated that the structure of the nanosponge did not undergo changes upon drug loading compared to the unloaded system. However, the 13C NMR spectra collected under variable contact time cross-polarization (VCT-CP) conditions showed that the polymeric scaffold CDNS changed significantly its dynamic regime on passing from the empty CDNS to the drug-loaded CDNS, thus showing that the drug encapsulation can be seen as the formation of a real supramolecular aggregate rather than a conglomerate of two solid components. Finally, the structural features obtained from the different solid-state NMR approaches reported matched the information from powder X-ray diffraction profiles. PMID:28228859

  11. Proton-Detected Solid-State NMR Spectroscopy of Bone with Ultrafast Magic Angle Spinning

    NASA Astrophysics Data System (ADS)

    Mroue, Kamal H.; Nishiyama, Yusuke; Kumar Pandey, Manoj; Gong, Bo; McNerny, Erin; Kohn, David H.; Morris, Michael D.; Ramamoorthy, Ayyalusamy

    2015-07-01

    While obtaining high-resolution structural details from bone is highly important to better understand its mechanical strength and the effects of aging and disease on bone ultrastructure, it has been a major challenge to do so with existing biophysical techniques. Though solid-state NMR spectroscopy has the potential to reveal the structural details of bone, it suffers from poor spectral resolution and sensitivity. Nonetheless, recent developments in magic angle spinning (MAS) NMR technology have made it possible to spin solid samples up to 110 kHz frequency. With such remarkable capabilities, 1H-detected NMR experiments that have traditionally been challenging on rigid solids can now be implemented. Here, we report the first application of multidimensional 1H-detected NMR measurements on bone under ultrafast MAS conditions to provide atomistic-level elucidation of the complex heterogeneous structure of bone. Our investigations demonstrate that two-dimensional 1H/1H chemical shift correlation spectra for bone are obtainable using fp-RFDR (finite-pulse radio-frequency-driven dipolar recoupling) pulse sequence under ultrafast MAS. Our results infer that water exhibits distinct 1H-1H dipolar coupling networks with the backbone and side-chain regions in collagen. These results show the promising potential of proton-detected ultrafast MAS NMR for monitoring structural and dynamic changes caused by mechanical loading and disease in bone.

  12. Isotope labeling of eukaryotic membrane proteins in yeast for solid-state NMR.

    PubMed

    Fan, Ying; Emami, Sanaz; Munro, Rachel; Ladizhansky, Vladimir; Brown, Leonid S

    2015-01-01

    Solid-state NMR (ssNMR) is a rapidly developing technique for exploring structure and dynamics of membrane proteins, but its progress is hampered by its low sensitivity. Despite the latest technological advances, routine ssNMR experiments still require several milligrams of isotopically labeled protein. While production of bacterial membrane proteins on this scale is usually feasible, obtaining such quantities of eukaryotic membrane proteins is often impossible or extremely costly. We have demonstrated that, by using isotopic labeling in yeast Pichia pastoris, one can inexpensively produce milligram quantities of doubly labeled functional samples, which yield multidimensional ssNMR spectra of high resolution suitable for detailed structural investigation. This was achieved by combining protocols of economical isotope labeling of soluble proteins previously used for solution NMR with protocols of expression of eukaryotic membrane proteins successfully employed for other methods. We review two cases of such isotope labeling, of fungal rhodopsin from Leptosphaeria maculans and human aquaporin-1. © 2015 Elsevier Inc. All rights reserved.

  13. Dynamics and interactions of ibuprofen in cyclodextrin nanosponges by solid-state NMR spectroscopy.

    PubMed

    Ferro, Monica; Castiglione, Franca; Pastori, Nadia; Punta, Carlo; Melone, Lucio; Panzeri, Walter; Rossi, Barbara; Trotta, Francesco; Mele, Andrea

    2017-01-01

    Two different formulations of cyclodextrin nanosponges (CDNS), obtained by polycondensation of β-cyclodextrin with ethylenediaminetetraacetic acid dianhydride (EDTAn), were treated with aqueous solutions of ibuprofen sodium salt (IbuNa) affording hydrogels that, after lyophilisation, gave two solid CDNS-drug formulations. (1)H fast MAS NMR and (13)C CP-MAS NMR spectra showed that IbuNa was converted in situ into its acidic and dimeric form (IbuH) after freeze-drying. (13)C CP-MAS NMR spectra also indicated that the structure of the nanosponge did not undergo changes upon drug loading compared to the unloaded system. However, the (13)C NMR spectra collected under variable contact time cross-polarization (VCT-CP) conditions showed that the polymeric scaffold CDNS changed significantly its dynamic regime on passing from the empty CDNS to the drug-loaded CDNS, thus showing that the drug encapsulation can be seen as the formation of a real supramolecular aggregate rather than a conglomerate of two solid components. Finally, the structural features obtained from the different solid-state NMR approaches reported matched the information from powder X-ray diffraction profiles.

  14. A high-resolution solid-state NMR approach for the structural studies of bicelles.

    PubMed

    Dvinskikh, Sergey; Dürr, Ulrich; Yamamoto, Kazutoshi; Ramamoorthy, Ayyalusamy

    2006-05-17

    Bicelles are increasingly being used as membrane mimicking systems in NMR experiments to investigate the structure of membrane proteins. In this study, we demonstrate the effectiveness of a 2D solid-state NMR approach that can be used to measure the structural constraints, such as heteronuclear dipolar couplings between 1H, 13C, and 31P nuclei, in bicelles without the need for isotopic enrichment. This method does not require a high radio frequency power unlike the presently used rotating-frame separated-local-field (SLF) techniques, such as PISEMA. In addition, multiple dipolar couplings can be measured accurately, and the presence of a strong dipolar coupling does not suppress the weak couplings. High-resolution spectra obtained from magnetically aligned DMPC:DHPC bicelles even in the presence of peptides suggest that this approach will be useful in understanding lipid-protein interactions that play a vital role in shaping up the function of membrane proteins.

  15. A High Resolution Solid State NMR Approach for the Structural Studies of Bicelles

    PubMed Central

    Dvinskikh, Sergey; Dürr, Ulrich; Yamamoto, Kazutoshi; Ramamoorthy, Ayyalusamy

    2008-01-01

    Bicelles are increasingly being used as membrane mimicking systems in NMR experiments to investigate the structure of membrane proteins. In this study, we demonstrate the effectiveness of a 2D solid-state NMR approach that can be used to measure the structural constraints such as heteronuclear dipolar couplings between 1H, 13C and 31P nuclei in bicelles without the need for isotopic enrichment. This method does not require a high radio frequency power unlike the presently used rotating-frame separated-local-field (SLF) techniques like PISEMA. In addition, multiple dipolar couplings can be measured accurately and the presence of a strong dipolar coupling does not suppress the weak couplings. High resolution spectra obtained from magnetically aligned DMPC:DHPC bicelles even in the presence of peptides suggest that this approach will be useful in understanding lipid-protein interactions that play a vital role in shaping up the function of membrane proteins. PMID:16683791

  16. Structural studies of proteins by paramagnetic solid-state NMR spectroscopy

    PubMed Central

    Jaroniec, Christopher P.

    2015-01-01

    Paramagnetism-based nuclear pseudocontact shifts and spin relaxation enhancements contain a wealth of information in solid-state NMR spectra about electron-nucleus distances on the ~20 Å length scale, far beyond that normally probed through measurements of nuclear dipolar couplings. Such data are especially vital in the context of structural studies of proteins and other biological molecules that suffer from a sparse number of experimentally-accessible atomic distances constraining their three-dimensional fold or intermolecular interactions. This perspective provides a brief overview of the recent developments and applications of paramagnetic magic-angle spinning NMR to biological systems, with primary focus on the investigations of metalloproteins and natively diamagnetic proteins modified with covalent paramagnetic tags. PMID:25797004

  17. A solid-state NMR study of the formation of molecular sieve SAPO-34.

    PubMed

    Yan, Zhimin; Chen, Banghao; Huang, Yining

    2009-04-01

    This work examined the formation of a catalytically important microporous material, SAPO-34, in the presence of HF under hydrothermal synthesis conditions. The local environments of P, Al, F and Si atoms in several solid phases obtained at different stages of crystallization were characterized by several solid-state NMR techniques including (31)P, (27)Al, (19)F and (29)Si MAS, (27)Al triple-quantum MAS, (31)P{(27)Al} transfer of populations in double-resonance, (27)Al{(31)P} rotational-echo double-resonance (REDOR), (27)Al-->(31)P heteronuclear correlation spectroscopy, (31)P{(19)F} and (27)Al{(19)F} REDOR as well as (1)H-->(31)P cross polarization. The NMR results provide the new insights into the formation of SAPO-34.

  18. 2H-DNP-enhanced 2H–13C solid-state NMR correlation spectroscopy

    PubMed Central

    Maly, Thorsten; Andreas, Loren B.; Smith, Albert A.

    2015-01-01

    Perdeuteration of biological macromolecules for magic angle spinning solid-state NMR spectroscopy can yield high-resolution 2H–13C correlation spectra and the method is therefore of great interest for the structural biology community. Here we demonstrate that the combination of sample deuteration and dynamic nuclear polarization yields resolved 2H–13C correlation spectra with a signal enhancement of ε ≥ 700 compared to a spectrum recorded with microwaves off and otherwise identical conditions. To our knowledge, this is the first time that 2H-DNP has been employed to enhance MAS-NMR spectra of a biologically relevant system. The DNP process is studied using several polarizing agents and the technique is applied to obtain 2H–13C correlation spectra of U-[2H, 13C] proline. PMID:20458422

  19. Solid-state NMR and EPR Spectroscopy of Mn(2+) -Substituted ATP-Fueled Protein Engines.

    PubMed

    Wiegand, Thomas; Lacabanne, Denis; Keller, Katharina; Cadalbert, Riccardo; Lecoq, Lauriane; Yulikov, Maxim; Terradot, Laurent; Jeschke, Gunnar; Meier, Beat H; Böckmann, Anja

    2017-02-13

    Paramagnetic metal ions deliver structural information both in EPR and solid-state NMR experiments, offering a profitable synergetic approach to study bio-macromolecules. We demonstrate the spectral consequences of Mg(2+) / Mn(2+) substitution and the resulting information contents for two different ATP:Mg(2+) -fueled protein engines, a DnaB helicase from Helicobacter pylori active in the bacterial replisome, and the ABC transporter BmrA, a bacterial efflux pump. We show that, while EPR spectra report on metal binding and provide information on the geometry of the metal centers in the proteins, paramagnetic relaxation enhancements identified in the NMR spectra can be used to localize residues at the binding site. Protein engines are ubiquitous and the methods described herein should be applicable in a broad context.

  20. Applications of high-resolution 1H solid-state NMR.

    PubMed

    Brown, Steven P

    2012-02-01

    This article reviews the large increase in applications of high-resolution (1)H magic-angle spinning (MAS) solid-state NMR, in particular two-dimensional heteronuclear and homonuclear (double-quantum and spin-diffusion NOESY-like exchange) experiments, in the last five years. These applications benefit from faster MAS frequencies (up to 80 kHz), higher magnetic fields (up to 1 GHz) and pulse sequence developments (e.g., homonuclear decoupling sequences applicable under moderate and fast MAS). (1)H solid-state NMR techniques are shown to provide unique structural insight for a diverse range of systems including pharmaceuticals, self-assembled supramolecular structures and silica-based inorganic-organic materials, such as microporous and mesoporous materials and heterogeneous organometallic catalysts, for which single-crystal diffraction structures cannot be obtained. The power of NMR crystallography approaches that combine experiment with first-principles calculations of NMR parameters (notably using the GIPAW approach) are demonstrated, e.g., to yield quantitative insight into hydrogen-bonding and aromatic CH-π interactions, as well as to generate trial three-dimensional packing arrangements. It is shown how temperature-dependent changes in the (1)H chemical shift, linewidth and DQ-filtered signal intensity can be analysed to determine the thermodynamics and kinetics of molecular level processes, such as the making and breaking of hydrogen bonds, with particular application to proton-conducting materials. Other applications to polymers and biopolymers, inorganic compounds and bioinorganic systems, paramagnetic compounds and proteins are presented. The potential of new technological advances such as DNP methods and new microcoil designs is described.

  1. Quantifying the chemical composition of soil organic carbon with solid-state 13C NMR

    NASA Astrophysics Data System (ADS)

    Baldock, J. A.; Sanderman, J.

    2011-12-01

    The vulnerability of soil organic carbon (SOC) to biological decomposition and mineralisation to CO2 is defined at least partially by its chemical composition. Highly aromatic charcoal-like SOC components are more stable to biological decomposition than other forms of carbon including cellulose. Solid-state 13C NMR has gained wide acceptance as a method capable of defining SOC chemical composition and mathematical fitting processes have been developed to estimate biochemical composition. Obtaining accurate estimates depends on an ability to quantitatively detect all carbon present in a sample. Often little attention has been paid to defining the proportion of organic carbon present in a soil that is observable in solid-state 13C NMR analyses of soil samples. However, if such data is to be used to inform carbon cycling studies, it is critical that quantitative assessments of SOC observability be undertaken. For example, it is now well established that a significant discrimination exists against the detection of the low proton content polyaromatic structures typical of charcoal using cross polarisation 13C NMR analyses. Such discrimination does not exist where direct polarisation analyses are completed. In this study, the chemical composition of SOC as defined by cross polarisation and direct polarisation13C NMR analyses will be compared for Australian soils collected from under a diverse range of agricultural managements and climatic conditions. Results indicate that where significant charcoal C contents exist, it is highly under-represented in the acquired CP spectra. For some soils, a discrimination against alkyl carbon was also evident. The ability to derive correction factors to compensate for such discriminations will be assessed and presented.

  2. Peptidoglycan architecture of Gram-positive bacteria by solid-state NMR.

    PubMed

    Kim, Sung Joon; Chang, James; Singh, Manmilan

    2015-01-01

    Peptidoglycan is an essential component of cell wall in Gram-positive bacteria with unknown architecture. In this review, we summarize solid-state NMR approaches to address some of the unknowns in the Gram-positive bacteria peptidoglycan architecture: 1) peptidoglycan backbone conformation, 2) PG-lattice structure, 3) variations in the peptidoglycan architecture and composition, 4) the effects of peptidoglycan bridge-length on the peptidoglycan architecture in Fem mutants, 5) the orientation of glycan strands with respect to the membrane, and 6) the relationship between the peptidoglycan structure and the glycopeptide antibiotic mode of action. Solid-state NMR analyses of Staphylococcus aureus cell wall show that peptidoglycan chains are surprisingly ordered and densely packed. The peptidoglycan disaccharide backbone adopts 4-fold screw helical symmetry with the disaccharide unit periodicity of 40Å. Peptidoglycan lattice in the S. aureus cell wall is formed by cross-linked PG stems that have parallel orientations. The structural characterization of Fem-mutants of S. aureus with varying lengths of bridge structures suggests that the PG-bridge length is an important determining factor for the PG architecture.

  3. Structure and dynamics of cationic membrane peptides and proteins: Insights from solid-state NMR

    PubMed Central

    Hong, Mei; Su, Yongchao

    2011-01-01

    Many membrane peptides and protein domains contain functionally important cationic Arg and Lys residues, whose insertion into the hydrophobic interior of the lipid bilayer encounters significant energy barriers. To understand how these cationic molecules overcome the free energy barrier to insert into the lipid membrane, we have used solid-state NMR spectroscopy to determine the membrane-bound topology of these peptides. A versatile array of solid-state NMR experiments now readily yields the conformation, dynamics, orientation, depth of insertion, and site-specific protein–lipid interactions of these molecules. We summarize key findings of several Arg-rich membrane peptides, including β-sheet antimicrobial peptides, unstructured cell-penetrating peptides, and the voltage-sensing helix of voltage-gated potassium channels. Our results indicate the central role of guanidinium-phosphate and guanidinium-water interactions in dictating the structural topology of these cationic molecules in the lipid membrane, which in turn account for the mechanisms of this functionally diverse class of membrane peptides. PMID:21344534

  4. Solid-state NMR on a type III antifreeze protein in the presence of ice.

    PubMed

    Siemer, Ansgar B; McDermott, Ann E

    2008-12-24

    Antifreeze proteins (AFPs) are found in fish, insects, plants, and a variety of other organisms where they serve to prevent the growth of ice at subzero temperatures. Type III AFPs cloned from polar fishes have been studied extensively with X-ray crystallography, liquid-state NMR, and site directed mutagenesis and are, therefore, among the best characterized AFPs. A flat surface on the protein has previously been proposed to be the ice-binding site of type III AFP. The detailed nature of the ice binding remains controversial since it is not clear whether only polar or also hydrophobic residues are involved in ice binding and there is no structural information available of a type III AFP bound to ice. Here we present a high-resolution solid-state NMR study of a type III AFP (HPLC-12 isoform) in the presence of ice. The chemical-shift differences we detected between the frozen and the nonfrozen state agree well with the proposed ice-binding site. Furthermore, we found that the (1)H T(1) of HPLC-12 in frozen solution is very long compared to typical (1)H of proteins in the solid state as for example of ubiquitin in frozen solution.

  5. Probing Quadrupolar Nuclei by Solid-State NMR Spectroscopy: Recent Advances

    SciTech Connect

    Fernandez, Christian; Pruski, Marek

    2011-06-08

    Solid-state nuclear magnetic resonance (NMR) of quadrupolar nuclei has recently undergone remarkable development of capabilities for obtaining structural and dynamic information at the molecular level. This review summarizes the key achievements attained during the last couple of decades in solid-state NMR of both integer spin and half-integer spin quadrupolar nuclei. We provide a concise description of the first- and second-order quadrupolar interactions, and their effect on the static and magic angle spinning (MAS) spectra. Methods are explained for efficient excitation of single- and multiple-quantum coherences, and acquisition of spectra under low- and high-resolution conditions. Most of all, we present a coherent, comparative description of the high-resolution methods for half-integer quadrupolar nuclei, including double rotation (DOR), dynamic angle spinning (DAS), multiple-quantum magic angle spinning (MQMAS), and satellite transition magic angle spinning (STMAS). Also highlighted are methods for processing and analysis of the spectra. Finally, we review methods for probing the heteronuclear and homonuclear correlations between the quadrupolar nuclei and their quadrupolar or spin-1/2 neighbors.

  6. β-Helical architecture of cytoskeletal bactofilin filaments revealed by solid-state NMR

    PubMed Central

    Vasa, Suresh; Lin, Lin; Shi, Chaowei; Habenstein, Birgit; Riedel, Dietmar; Kühn, Juliane; Thanbichler, Martin; Lange, Adam

    2015-01-01

    Bactofilins are a widespread class of bacterial filament-forming proteins, which serve as cytoskeletal scaffolds in various cellular pathways. They are characterized by a conserved architecture, featuring a central conserved domain (DUF583) that is flanked by variable terminal regions. Here, we present a detailed investigation of bactofilin filaments from Caulobacter crescentus by high-resolution solid-state NMR spectroscopy. De novo sequential resonance assignments were obtained for residues Ala39 to Phe137, spanning the conserved DUF583 domain. Analysis of the secondary chemical shifts shows that this core region adopts predominantly β-sheet secondary structure. Mutational studies of conserved hydrophobic residues located in the identified β-strand segments suggest that bactofilin folding and polymerization is mediated by an extensive and redundant network of hydrophobic interactions, consistent with the high intrinsic stability of bactofilin polymers. Transmission electron microscopy revealed a propensity of bactofilin to form filament bundles as well as sheet-like, 2D crystalline assemblies, which may represent the supramolecular arrangement of bactofilin in the native context. Based on the diffraction pattern of these 2D crystalline assemblies, scanning transmission electron microscopy measurements of the mass per length of BacA filaments, and the distribution of β-strand segments identified by solid-state NMR, we propose that the DUF583 domain adopts a β-helical architecture, in which 18 β-strand segments are arranged in six consecutive windings of a β-helix. PMID:25550503

  7. Solid-state NMR and TGA studies of silver reduction in chabazite.

    PubMed

    Chen, Fu; Liu, Yan; Wasylishen, Roderick E; Xu, Zhenghe; Kuznicki, Steven M

    2012-03-01

    Silver-exchanged molecular sieves have shown great promise in applications ranging from antimicrobial materials to the adsorption of xenon and iodide, two key contaminants emitted from nuclear reactors. In this work, solid-state 27Al and 29Si MAS NMR and TGA were used to study silver reduction in silver-exchanged chabazite under various thermal conditions. The solid-state NMR results for both 27Al and 29Si show that there are no major changes in the chabazite during silver reduction in an argon stream; however a progressive structural change does take place in the hydrogen stream. The structural change likely involves breaking the silicon oxygen bond of the Si-O-AI fragment of chabazite, leading to the formation of extra-framework aluminum oxide. The TGA results at temperatures up to 600 degrees C indicate that silver reduction is less complete in an argon stream than in a hydrogen stream. In this paper we propose that silver reduction occurs via the following reactions: 2(Ag + ZO-)+H2O --> 1/2O2+2Ag0 + 2ZOH and nAg + mAg = Ag(m+n)n+ (in an argon stream); and Ag(+) + ZO(-) + 1/2H2 = Ag0 + ZOH and 2ZOH = ZO(-) + Z(+) + H2O (in a hydrogen stream).

  8. Chemical structure and heterogeneity differences of two lignins from loblolly pine as investigated by advanced solid-state NMR spectroscopy

    USDA-ARS?s Scientific Manuscript database

    Advanced solid-state NMR was employed to investigate differences in chemical structure and heterogeneity between milled wood lignin (MWL) and residual enzyme lignin (REL). Wiley and conventional milled woods were also studied. The advanced NMR techniques included 13C quantitative direct polarization...

  9. Yeast-expressed human membrane protein aquaporin-1 yields excellent resolution of solid-state MAS NMR spectra.

    PubMed

    Emami, Sanaz; Fan, Ying; Munro, Rachel; Ladizhansky, Vladimir; Brown, Leonid S

    2013-02-01

    One of the biggest challenges in solid-state NMR studies of membrane proteins is to obtain a homogeneous natively folded sample giving high spectral resolution sufficient for structural studies. Eukaryotic membrane proteins are especially difficult and expensive targets in this respect. Methylotrophic yeast Pichia pastoris is a reliable producer of eukaryotic membrane proteins for crystallography and a promising economical source of isotopically labeled proteins for NMR. We show that eukaryotic membrane protein human aquaporin 1 can be doubly ((13)C/(15)N) isotopically labeled in this system and functionally reconstituted into phospholipids, giving excellent resolution of solid-state magic angle spinning NMR spectra.

  10. Sensitivity enhancement in static solid-state NMR experiments via single- and multiple-quantum dipolar coherences.

    PubMed

    Gopinath, T; Veglia, Gianluigi

    2009-04-29

    We present a new method for enhancing the sensitivity in static solid-state NMR experiments for a gain in signal-to-noise ratio of up to 40%. This sensitivity enhancement is different from the corresponding solution NMR sensitivity enhancement schemes and is achieved by combining single- and multiple-quantum dipolar coherences. While this new approach is demonstrated for the polarization inversion spin exchange at magic angle (PISEMA) experiment, it can be generalized to the other separated local field experiments for solid-state NMR spectroscopy. This method will have a direct impact on solid-state NMR spectroscopy of liquid crystals as well as of membrane proteins aligned in lipid membranes.

  11. Retinal Dynamics During Light Activation of Rhodopsin Revealed by Solid-State NMR Spectroscopy

    PubMed Central

    Brown, Michael F.; Salgado, Gilmar F. J.; Struts, Andrey V.

    2016-01-01

    Rhodopsin is a canonical member of class A of the G protein-coupled receptors (GPCR) that are implicated in many of the drug interventions in humans and are of great pharmaceutical interest. The molecular mechanism of rhodopsin activation remains unknown as atomistic structural information for the active metarhodopsin II state is currently lacking. Solid-state 2H NMR constitutes a powerful aproarch to study atomic-level dynamics of membrane proteins. In the present application we describe how information is obtained about interactions of the retinal cofactor with rhodopsin that change with light activation of the photoreceptor. The retinal methyl groups play an important role in rhodopsin function by directing conformational changes upon transition into the active state. Site-specific 2H labels have been introduced into the methyl groups of retinal and solid-state 2H NMR methods applied to obtain order parameters and correlation times that quantify the mobility of the cofactor in the inactive dark state, as well as the cryo-trapped metarhodopsin I and metarhodopsin II states. Analysis of the angular-dependent 2H NMR lineshapes for selectively deuterated methyl groups of rhodopsin in aligned membranes enables determination of the average ligand conformation within the binding pocket. The relaxation data suggest that the β-ionone ring is not expelled from its hydrophobic pocket in the transition from the pre-activated metarhodopsin I to the active metarhodopsin II state. Rather, the major structural changes of the retinal cofactor occur already at the metarhodopsin I state in the activation process. The metarhodopsin I to metarhodopsin II transition involves mainly conformational changes of the protein within the membrane lipid bilayer rather than the ligand. The dynamics of the retinylidene methyl groups upon isomerization are explained by an activation mechanism involving cooperative rearrangments of extracellular loop E2 together with transmembrane helices H5 and

  12. Solid state NMR methods for coal science. Progress report, October 1, 1983-December 31, 1984

    SciTech Connect

    Zilm, K.W.

    1984-12-01

    This report covers the progress made on the title project during the last quarter. While a good deal of our time has been spent setting up our new NMR laboratory, we have made several significant advances in solid state NMR techniques development that will have important applications in structure determination of coal, coal products and other fossil fuels. We have developed a CP/MAS probe that is routinely capable of producing decoupling fields in excess of 100 KHz without excessive power consumption and that has a very homogeneous frequency field. This piece of equipment has proven crucial to the success of a number of new techniques we are developing. In addition to increasing our sensitivity, the intensity, and homogeneity of the R.F. field, this probe now makes a number of multiple pulse techniques feasible. One avenue has been pursued this quarter is to use multiple pulse decoupling to make 2-D spectroscopy feasible in solids and this has resulted in the first proton-carbon chemical shift correlation spectrum of coal. The homogeneity of the R.F. field has also been helpful in some relaxation studies of coals aimed at an improved understanding of the quantitative aspects of /sup 13/C CP/MAS of coals, i.e., are all the carbons observed. Other techniques being investigated include high field /sup 2/D NMR and /sup 2/D zero field NMR. 8 figures, 1 table.

  13. Solid-state and unilateral NMR study of deterioration of a Dead Sea Scroll fragment.

    PubMed

    Masic, A; Chierotti, M R; Gobetto, R; Martra, G; Rabin, I; Coluccia, S

    2012-02-01

    Unilateral and solid-state nuclear magnetic resonance (NMR) analyses were performed on a parchment fragment of the Dead Sea Scroll (DSS). The analyzed sample belongs to the collection of non-inscribed and nontreated fragments of known archaeological provenance from the John Rylands University Library in Manchester. Therefore, it can be considered as original DSS material free from any contamination related to the post-discovery period. Considering the paramount significance of the DSS, noninvasive approaches and portable in situ nondestructive methods are of fundamental importance for the determination of composition, structure, and chemical-physical properties of the materials under study. NMR studies reveal low amounts of water content associated with very short proton relaxation times, T(1), indicating a high level of deterioration of collagen molecules within scroll fragments. In addition, (13)C cross-polarization magic-angle-spinning (CPMAS) NMR spectroscopy shows characteristic peaks of lipids whose presence we attribute to the production technology that did not involve liming. Extraction with chloroform led to the reduction of both lipid and protein signals in the (13)C CPMAS spectrum indicating probable involvement of lipids in parchment degradation processes. NMR absorption and relaxation measurements provide nondestructive, discriminative, and sensitive tools for studying the deterioration effects on the organization and properties of water and collagen within ancient manuscripts.

  14. Solid state (13)C NMR analysis of human gallstones from cancer and benign gall bladder diseases.

    PubMed

    Jayalakshmi, K; Sonkar, Kanchan; Behari, Anu; Kapoor, V K; Sinha, Neeraj

    2009-09-01

    Natural abundance (13)C cross polarized (CP) magic angle spinning (MAS) nuclear magnetic resonance (NMR) analysis of human gall bladder stones collected from patients suffering from malignant and benign gall bladder disease was carried out which revealed different polymorphs of cholesterol in these stones. All gall bladder stones in present study had cholesterol as their main constituent. (13)C CP-MAS NMR analysis revealed three forms of cholesterol molecules in these stones, which are anhydrous form, monohydrate crystalline with amorphous form and monohydrate crystalline form. Our study revealed that stones collected from patients associated with chronic cholecystitis (CC) disease have mostly different polymorph of cholesterol than stones collected from patients associated with gall bladder cancer (GBC). Such study will be helpful in understanding the mechanism of formation of gallstones which are associated with different gall bladder diseases. This is the first study by solid state NMR revealing different crystal polymorphism of cholesterol in human gallstones, extending the applicability of (13)C CP-MAS NMR technique for the routine study of gallstones.

  15. Development of solid-state NMR techniques for the characterisation of pharmaceutical compounds

    NASA Astrophysics Data System (ADS)

    Tatton, Andrew S.

    Structural characterisation in the solid state is an important step in understanding the physical and chemical properties of a material. Solid-state NMR techniques applied to solid delivery forms are presented as an alternative to more established structural characterisation methods. The effect of homonuclear decoupling upon heteronuclear couplings is investigated using a combination of experimental and density-matrix simulation results acquired from a 13C-1H spinecho pulse sequence, modulated by scalar couplings. It is found that third-order cross terms under MAS and homonuclear decoupling contribute to strong dephasing effects in the NMR signal. Density-matrix simulations allow access to parameters currently unattainable in experiment, and demonstrate that higher homonuclear decoupling rf nutation frequencies reduce the magnitude of third-order cross terms. 15N-1H spinecho experiments were applied to pharmaceutically relevant samples to differentiate between the number of directly attached protons. Using this method, proton transfer in an acid-base reaction is proven in pharmaceutical salts. The indirect detection of 14N lineshapes via protons obtained using 2D 14N-1H HMQC experiments is presented, where coherence transfer is achieved via heteronuclear through-space dipolar couplings. The importance of fast MAS frequencies is demonstrated, and it is found that increasing the recoupling duration reveals longer range NH proximities. The 2D 14N-1H HMQC method is used to demonstrate the presence of specific hydrogen bonding interactions, and thus aid in identifying molecular association in a cocrystal and an amorphous dispersion. In addition, hydrogen bonding motifs were identified by observing the changes in the 14N quadrupolar parameters between individual molecular components relative to the respective solid delivery form. First-principles calculations of NMR chemical shifts and quadrupolar parameters using the GIPAW method were combined with 14N-1H experimental

  16. Membrane topology of a 14-mer model amphipathic peptide: a solid-state NMR spectroscopy study.

    PubMed

    Ouellet, Marise; Doucet, Jean-Daniel; Voyer, Normand; Auger, Michèle

    2007-06-05

    We have investigated the interaction between a synthetic amphipathic 14-mer peptide and model membranes by solid-state NMR. The 14-mer peptide is composed of leucines and phenylalanines modified by the addition of crown ethers and forms a helical amphipathic structure in solution and bound to lipid membranes. To shed light on its membrane topology, 31P, 2H, 15N solid-state NMR experiments have been performed on the 14-mer peptide in interaction with mechanically oriented bilayers of dilauroylphosphatidylcholine (DLPC), dimyristoylphosphatidylcholine (DMPC), and dipalmitoylphosphatidylcholine (DPPC). The 31P, 2H, and 15N NMR results indicate that the 14-mer peptide remains at the surface of the DLPC, DMPC, and DPPC bilayers stacked between glass plates and perturbs the lipid orientation relative to the magnetic field direction. Its membrane topology is similar in DLPC and DMPC bilayers, whereas the peptide seems to be more deeply inserted in DPPC bilayers, as revealed by the greater orientational and motional disorder of the DPPC lipid headgroup and acyl chains. 15N{31P} rotational echo double resonance experiments have also been used to measure the intermolecular dipole-dipole interaction between the 14-mer peptide and the phospholipid headgroup of DMPC multilamellar vesicles, and the results indicate that the 14-mer peptide is in contact with the polar region of the DMPC lipids. On the basis of these studies, the mechanism of membrane perturbation of the 14-mer peptide is associated to the induction of a positive curvature strain induced by the peptide lying on the bilayer surface and seems to be independent of the bilayer hydrophobic thickness.

  17. Solid state NMR and LVSEM studies on the hardening of latex modified tile mortar systems

    SciTech Connect

    Rottstegge, J.; Arnold, M.; Herschke, L.; Glasser, G.; Wilhelm, M.; Spiess, H.W. . E-mail: spiess@mpip-mainz.mpg.de; Hergeth, W.D.

    2005-12-15

    Construction mortars contain a broad variety of both inorganic and organic additives beside the cement powder. Here we present a study of tile mortar systems based on portland cement, quartz, methyl cellulose and different latex additives. As known, the methyl cellulose stabilizes the freshly prepared cement paste, the latex additive enhances final hydrophobicity, flexibility and adhesion. Measurements were performed by solid state nuclear magnetic resonance (NMR) and low voltage scanning electron microscopy (LVSEM) to probe the influence of the latex additives on the hydration, hardening and the final tile mortar properties. While solid state NMR enables monitoring of the bulk composition, scanning electron microscopy affords visualization of particles and textures with respect to their shape and the distribution of the different phases. Within the alkaline cement paste, the poly(vinyl acetate) (VAc)-based latex dispersions stabilized by poly(vinyl alcohol) (PVA) were found to be relatively stable against hydrolysis. The influence of the combined organic additives methyl cellulose, poly(vinyl alcohol) and latexes stabilized by poly(vinyl alcohol) on the final silicate structure of the cement hydration products is small. But even small amounts of additives result in an increased ratio of ettringite to monosulfate within the final hydrated tile mortar as monitored by {sup 27}Al NMR. The latex was found to be adsorbed to the inorganic surfaces, acting as glue to the inorganic components. For similar latex water interfaces built up by poly(vinyl alcohol), a variation in the latex polymer composition results in modified organic textures. In addition to the networks of the inorganic cement and of the latex, there is a weak network build up by thin polymer fibers, most probably originating from poly(vinyl alcohol). Besides the weak network, polymer fibers form well-ordered textures covering inorganic crystals such as portlandite.

  18. Atomic substitutions in synthetic apatite; Insights from solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Vaughn, John S.

    Apatite, Ca5(PO4)3X (where X = F, Cl, or OH), is a unique mineral group capable of atomic substitutions for cations and anions of varied size and charge. Accommodation of differing substituents requires some kind of structural adaptation, e.g. new atomic positions, vacancies, or coupled substitutions. These structural adaptations often give rise to important physicochemical properties relevant to a range of scientific disciplines. Examples include volatile trapping during apatite crystallization, substitution for large radionuclides for long-term storage of nuclear fission waste, substitution for fluoride to improve acid resistivity in dental enamel composed dominantly of hydroxylapatite, and the development of novel biomaterials with enhanced biocompatibility. Despite the importance and ubiquity of atomic substitutions in apatite materials, many of the mechanisms by which these reactions occur are poorly understood. Presence of substituents at dilute concentration and occupancy of disordered atomic positions hinder detection by bulk characterization methods such as X-ray diffraction (XRD) and infrared (IR) spectroscopy. Solid-state nuclear magnetic resonance (NMR) spectroscopy is an isotope-specific structural characterization technique that does not require ordered atomic arrangements, and is therefore well suited to investigate atomic substitutions and structural adaptations in apatite. In the present work, solid-state NMR is utilized to investigate structural adaptations in three different types of apatite materials; a series of near-binary F, Cl apatite, carbonate-hydroxylapatite compositions prepared under various synthesis conditions, and a heat-treated hydroxylapatite enriched in 17O. The results indicate that hydroxyl groups in low-H, near binary F,Cl apatite facilitate solid-solution between F and Cl via column reversals, which result in average hexagonal symmetry despite very dilute OH concentration ( 2 mol percent). In addition, 19F NMR spectra indicate

  19. Application of Solid-State NMR Relaxometry for Characterization and Formulation Optimization of Grinding-Induced Drug Nanoparticle.

    PubMed

    Ueda, Keisuke; Higashi, Kenjirou; Moribe, Kunikazu

    2016-03-07

    The formation mechanism of drug nanoparticles was investigated using solid-state nuclear magnetic resonance (NMR) techniques for the efficient discovery of an optimized nanoparticle formulation. The cogrinding of nifedipine (NIF) with polymers, including hydroxypropyl methylcellulose (HPMC) and polyvinylpyrrolidone (PVP), and sodium dodecyl sulfate (SDS) was performed to prepare the NIF nanoparticle formulations. Then, solid-state NMR relaxometry was used for the nanometer-order characterization of NIF in the polymer matrix. Solid-state NMR measurements revealed that the crystal size of NIF was reduced to several tens of nanometers with amorphization of NIF by cogrinding with HPMC and SDS for 100 min. Similarly, the size of the NIF crystal was reduced to less than 90 nm in the 40 min ground mixture of NIF/PVP/SDS. Furthermore, 100 min grinding of NIF/PVP/SDS induced amorphization of almost all the NIF crystals followed by nanosizing. The hydrogen bond between NIF and PVP led to the efficient amorphization of NIF in the NIF/PVP/SDS system compared with NIF/HPMC/SDS system. The efficient nanosizing of the NIF crystal in the solid state, revealed by the solid-state NMR relaxation time measurements, enabled the formation of large amounts of NIF nanoparticles in water followed by the polymer dissolution. In contrast, excess amorphization of the NIF crystals failed to efficiently prepare the NIF nanoparticles. The solid-state characterization of the crystalline NIF revealed good correlation with the NIF nanoparticles formation during aqueous dispersion. Furthermore, the solid-state NMR measurements including relaxometry successfully elucidated the nanometer-order dispersion state of NIF in polymer matrix, leading to the discovery of optimized conditions for the preparation of suitable drug nanoparticles.

  20. Solid state NMR study of SEI formation in lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Zhao, Dachun

    Recently, rechargeable lithium ion batteries, which offer high energy density and long cycle life, are in great demand as power sources for our mobile electronic society. The formation of a solid electrolyte interphase (SEI) on the surface of electrodes in lithium ion batteries plays an essential role in their performance. This thesis presents solid state NMR and MAS NMR results on the SEI, which contribute to our understanding of SEI formation on both cathodes and anodes. This thesis is organized as following: Chapter 1 surveys the history of batteries and the challenges to further development of the lithium ion battery. Fundamental aspects and SEI formation mechanisms are also included in Chapter l. Chapter 2 deals with the principles and experimental techniques of solid state NMR. Chapter 3 presents studies of SEI formation on anode and cathode in lithium ion batteries using electrochemical impedance spectroscopy (EIS) and NMR. The results provide EIS and NMR evidence that cells containing electrolytes with high EC content display less irreversible capacity after high temperature storage. The irreversible capacity is attributed to SEI growth on electrode surfaces. NMR results on cathodes, on the other hand, imply that the presence of Ni in the cathode may reduce cell performance due to the oxidation of Ni 3+ to Ni4+. Our simulations show that a lower EC/DMC ratio is associated with a smaller SEI intensity for the cathode and higher intensity for the anode. Chapter 4 discusses the effect of temperature on SEI formation on anodes and cathodes. NMR measurements show that MCMB graphite based anodes exhibit high stability no chemical shift is evident over a wide temperature range. On cathodes, however, NMR does reveal changes in SEI intensity as a function of temperature. These changes are believed to be the result of decomposition of the SEI. Evidently, then, changes in the performance of the cell as a factor of temperature are, at least in part, due to changes in

  1. Action of the multifunctional peptide BP100 on native biomembranes examined by solid-state NMR.

    PubMed

    Misiewicz, Julia; Afonin, Sergii; Grage, Stephan L; van den Berg, Jonas; Strandberg, Erik; Wadhwani, Parvesh; Ulrich, Anne S

    2015-04-01

    Membrane composition is a key factor that regulates the destructive activity of antimicrobial peptides and the non-leaky permeation of cell penetrating peptides in vivo. Hence, the choice of model membrane is a crucial aspect in NMR studies and should reflect the biological situation as closely as possible. Here, we explore the structure and dynamics of the short multifunctional peptide BP100 using a multinuclear solid-state NMR approach. The membrane alignment and mobility of this 11 amino acid peptide was studied in various synthetic lipid bilayers with different net charge, fluidity, and thickness, as well as in native biomembranes harvested from prokaryotic and eukaryotic cells. (19)F-NMR provided the high sensitivity and lack of natural abundance background that are necessary to observe a labelled peptide even in protoplast membranes from Micrococcus luteus and in erythrocyte ghosts. Six selectively (19)F-labeled BP100 analogues gave remarkably similar spectra in all of the macroscopically oriented membrane systems, which were studied under quasi-native conditions of ambient temperature and full hydration. This similarity suggests that BP100 has the same surface-bound helical structure and high mobility in the different biomembranes and model membranes alike, independent of charge, thickness or cholesterol content of the system. (31)P-NMR spectra of the phospholipid components did not indicate any bilayer perturbation, so the formation of toroidal wormholes or micellarization can be excluded as a mechanism of its antimicrobial or cell penetrating action. However, (2)H-NMR analysis of the acyl chain order parameter profiles showed that BP100 leads to considerable membrane thinning and thereby local destabilization.

  2. Solid-state NMR studies of the reactions of silica surfaces with polyfunctional chloromethylsilanes and ethoxymethylsilanes

    SciTech Connect

    Sindorf, D.W.; Maciel, G.E.

    1983-06-15

    The silylation of silica (Si) surfaces by dimethyldichlorosilane, methyltrichlorosilane, dimethyldiethoxysilane, and methyltriethoxysilane has been studied by solid-state /sup 29/Si and /sup 13/C NMR, by use of cross polarization (CP) and magic-angle spinning (MAS). An earlier formalism for the quantitative analysis of the NRM data has been extended for use with polyfunctional silyating agents and applied in detail to dimethyldichlorosilane reactions. Silylation with ethoxysilane reagents is less amenable to quantitative interpretation but appears to parallel closely the behavior of analogous chlorosilane reagents. With ethoxysilane reagents /sup 13/C NMR is found to be quite useful, especially for determining the fate of ethoxy groups. In all of the cases studied, the products are characterized primarily by single silane-to-surface attachments of each silane silicon atom. The presence of absorbed water is found to play an important role in the course and rate of the silylation reactions, especially those employing ethoxysilane reagents. The NMR data are used to address the question of horizontal and vertical polymerization within the silane phase on the silica surface.

  3. 15N Solid-State NMR as a Probe of Flavin H-bonding

    PubMed Central

    Cui, Dongtao; Koder, Ronald L.; Dutton, P. Leslie; Miller, Anne-Frances

    2011-01-01

    Flavins mediate a wide variety of different chemical reactions in biology. To learn how one cofactor can be made to execute different reactions in different enzymes, we are developing solid-state NMR (SSNMR) to probe the flavin electronic structure, via the 15N chemical shift tensor principal values (δii). We find that SSNMR has superior responsiveness to H-bonds, compared to solution NMR. H-bonding to a model of the flavodoxin active site produced an increase of 10 ppm in the δ11 of N5 although none of the H-bonds directly engage N5, and solution NMR detected only a 4 ppm increase in the isotropic chemical shift (δiso). Moreover SSNMR responded differently to different H-bonding environments as H-bonding with water caused δ11 to decrease by 6 ppm whereas δiso increased by less than 1 ppm. Our density functional theoretical (DFT) calculations reproduce the observations, validating the use of computed electronic structures to understand how H-bonds modulate the flavin’s reactivity. PMID:21619002

  4. Atomic-resolution structure of cytoskeletal bactofilin by solid-state NMR.

    PubMed

    Shi, Chaowei; Fricke, Pascal; Lin, Lin; Chevelkov, Veniamin; Wegstroth, Melanie; Giller, Karin; Becker, Stefan; Thanbichler, Martin; Lange, Adam

    2015-12-01

    Bactofilins are a recently discovered class of cytoskeletal proteins of which no atomic-resolution structure has been reported thus far. The bacterial cytoskeleton plays an essential role in a wide range of processes, including morphogenesis, cell division, and motility. Among the cytoskeletal proteins, the bactofilins are bacteria-specific and do not have a eukaryotic counterpart. The bactofilin BacA of the species Caulobacter crescentus is not amenable to study by x-ray crystallography or solution nuclear magnetic resonance (NMR) because of its inherent noncrystallinity and insolubility. We present the atomic structure of BacA calculated from solid-state NMR-derived distance restraints. We show that the core domain of BacA forms a right-handed β helix with six windings and a triangular hydrophobic core. The BacA structure was determined to 1.0 Å precision (heavy-atom root mean square deviation) on the basis of unambiguous restraints derived from four-dimensional (4D) HN-HN and 2D C-C NMR spectra.

  5. Molecular ordering of mixed surfactants in mesoporous silicas: A solid-state NMR study

    SciTech Connect

    Kobayashi, Takeshi; Mao, Kanmi; Wang, Shy-Guey; Lin, Victor S.-Y.; Pruski, Marek

    2011-02-17

    The use of mixed surfactants in the synthesis of mesoporous silica nanoparticles (MSNs) is of importance in the context of adjusting pore structures, sizes and morphologies. In the present study, the arrangement of molecules in micelles produced from a mixture of two surfactants, cetyltrimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPB) was detailed by solid-state NMR spectroscopy. Proximities of methyl protons in the trimethylammonium headgroup of CTAB and protons in the pyridinium headgroup of CPB were observed under fast magic angle spinning (MAS) by {sup 1}H-{sup 1}H double quantum (DQ) MAS NMR and NOESY. This result suggested that CTAB and CPB co-exist in the pores without forming significant monocomponent domain structures. {sup 1}H-{sup 29}Si heteronuclear correlation (HETCOR) NMR showed that protons in the headgroups of CTAB are in closer proximity to the silica surface than those in the CPB headgroups. The structural information obtained in this investigation leads to better understanding of the mechanisms of self-assembly and their role in determining the structure and morphology of mesoporous materials.

  6. Solid-state (49/47)Ti NMR of titanium-based MCM-41 hybrid materials.

    PubMed

    Ballesteros, Ruth; Fajardo, Mariano; Sierra, Isabel; Force, Carmen; del Hierro, Isabel

    2009-11-03

    Titanium solid-state NMR spectroscopy data for a series of organic-inorganic titanium MCM-41 based materials have been collected. These materials have been synthesized by first modifying the mesoporous silica MCM-41 in one step with a mixture of silanes: a triazine propyl triethoxysilane acting as functional linker and methyltrimethoxysilane or hexamethyldisilizane as capped agents to mask the remaining silanol groups. Second, the appropiate titanium precursor Ti(OPr(i))(4), [{Ti(OPr(i))(3)(OMent)}(2)] (OMent = 1R,2S,5R-(-)-menthoxo), Ti(OPr(i))(4), or [Ti(eta(5)-C(5)HMe(4))Cl(3)], has been immobilized by reaction with the modified MCM-41. Finally, after Ti(OPr(i))(4) immobilization onto the organomodified support the reaction with the chiral (+)-diethyl-l-tartrate was accomplished. The materials without functional linker have been also prepared by reaction in one step of the capped agent and the titanium precursor with the mesoporous silica. Relevant correlations of titanium NMR resonance chemical shifts and line widths can be inferred depending on different factors. The immobilization procedure used to prepare titanium-based MCM-41 hybrid materials and the choice of the silylating reagents employed to mask the silanol groups present on the silica surfaces produce significant differences in the Ti NMR spectra. Furthermore, depending on the electronic and sterical influence of the substituents directly attached to the titanium center, chemical shifts and line widths are modified providing novel information about titanium structure.

  7. Acidity characterization of heterogeneous catalysts by solid-state NMR spectroscopy using probe molecules.

    PubMed

    Zheng, Anmin; Liu, Shang-Bin; Deng, Feng

    2013-01-01

    Characterization of the surface acidic properties of solid acid catalysts is a key issue in heterogeneous catalysis. Important acid features of solid acids, such as their type (Brønsted vs. Lewis acid), distribution and accessibility (internal vs. external sites), concentration (amount), and strength of acid sites are crucial factors dictating their reactivity and selectivity. This short review provides information on different solid-state NMR techniques used for acidity characterization of solid acid catalysts. In particular, different approaches using probe molecules containing a specific nucleus of interest, such as pyridine-d5, 2-(13)C-acetone, trimethylphosphine, and trimethylphosphine oxide, are compared. Incorporation of valuable information (such as the adsorption structure, deprotonation energy, and NMR parameters) from density functional theory (DFT) calculations can yield explicit correlations between the chemical shift of adsorbed probe molecules and the intrinsic acid strength of solid acids. Methods that combine experimental NMR data with DFT calculations can therefore provide both qualitative and quantitative information on acid sites.

  8. Solid state and solution 43Ca NMR of calcium peroxides involved in the disproportionation of hydrogen peroxide by calcium hydroxide.

    PubMed

    Trokiner, Arlette; Bessière, Aurélie; Thouvenot, René; Hau, Damien; Marko, Jean; Nardello, Véronique; Pierlot, Christel; Aubry, Jean-Marie

    2004-06-01

    In order to get some insight into the mechanism of the disproportionation of hydrogen peroxide catalyzed by calcium hydroxide, 43Ca NMR spectra of enriched samples of calcium peroxides and of their precursors have been studied in both solution and solid state. This study demonstrates that no well-defined peroxidized calcium species are formed in solution, showing that the catalytic role of calcium is likely restricted to the solid state. Most of the calcium compounds that could be involved in the catalytic process have been investigated with solid state NMR. The shift and quadrupolar parameters of Ca(OH)2, CaO2.8H2O and CaO2.2H2O2 are reported for the first time. These parameters are different enough to allow the quantitative analysis of a complex mixture of these compounds by NMR.

  9. Polymorphs of Theophylline Characterized by DNP Enhanced Solid-State NMR

    PubMed Central

    2015-01-01

    We show how dynamic nuclear polarization (DNP) enhanced solid-state NMR spectroscopy can be used to characterize polymorphs and solvates of organic solids. We applied DNP to three polymorphs and one hydrated form of the asthma drug molecule theophylline. For some forms of theophylline, sample grinding and impregnation with the radical-containing solution, which are necessary to prepare the samples for DNP, were found to induce polymorphic transitions or desolvation between some forms. We present protocols for sample preparation for solid-state magic-angle spinning (MAS) DNP experiments that avoid the polymorphic phase transitions in theophylline. These protocols include cryogrinding, grinding under inert atmosphere, and the appropriate choice of the impregnating liquid. By applying these procedures, we subsequently demonstrate that two-dimensional correlation experiments, such as 1H–13C and 1H–15N HETCOR or 13C–13C INADEQUATE, can be obtained at natural isotopic abundance in reasonable times, thus enabling more advanced structural characterization of polymorphs. PMID:26393368

  10. Polymorphs of Theophylline Characterized by DNP Enhanced Solid-State NMR.

    PubMed

    Pinon, Arthur C; Rossini, Aaron J; Widdifield, Cory M; Gajan, David; Emsley, Lyndon

    2015-11-02

    We show how dynamic nuclear polarization (DNP) enhanced solid-state NMR spectroscopy can be used to characterize polymorphs and solvates of organic solids. We applied DNP to three polymorphs and one hydrated form of the asthma drug molecule theophylline. For some forms of theophylline, sample grinding and impregnation with the radical-containing solution, which are necessary to prepare the samples for DNP, were found to induce polymorphic transitions or desolvation between some forms. We present protocols for sample preparation for solid-state magic-angle spinning (MAS) DNP experiments that avoid the polymorphic phase transitions in theophylline. These protocols include cryogrinding, grinding under inert atmosphere, and the appropriate choice of the impregnating liquid. By applying these procedures, we subsequently demonstrate that two-dimensional correlation experiments, such as (1)H-(13)C and (1)H-(15)N HETCOR or (13)C-(13)C INADEQUATE, can be obtained at natural isotopic abundance in reasonable times, thus enabling more advanced structural characterization of polymorphs.

  11. Methodology for solid state NMR off-resonance study of molecular dynamics in heteronuclear systems.

    PubMed

    Jurga, Kazimierz; Woźniak-Braszak, Aneta; Baranowski, Mikołaj

    2015-10-01

    Methodology for the study of dynamics in heteronuclear systems in the laboratory frame was described in the previous paper [1]. Now the methodology for the study of molecular dynamics in the solid state heteronuclear systems in the rotating frame is presented. The solid state NMR off-resonance experiments were carried out on a homemade pulse spectrometer operating at the frequency of 30.2 MHz for protons. This spectrometer includes a specially designed probe which contains two independently tuned and electrically isolated coils installed in the coaxial position on the dewar. A unique probe design allows working at three slightly differing frequencies off and on resonance for protons and at the frequency of 28.411 MHz for fluorine nuclei with complete absence of their electrical interference. The probe allows simultaneously creating rf magnetic fields at off-resonance frequencies within the range of 30.2-30.6 MHz and at the frequency of 28.411 MHz. Presented heteronuclear cross-relaxation off-resonance experiments in the rotating frame provide information about molecular dynamics.

  12. Intensity and mosaic spread analysis from PISEMA tensors in solid-state NMR

    NASA Astrophysics Data System (ADS)

    Quine, J. R.; Achuthan, S.; Asbury, T.; Bertram, R.; Chapman, M. S.; Hu, J.; Cross, T. A.

    2006-04-01

    The solid-state NMR experiment PISEMA, is a technique for determining structures of proteins, especially membrane proteins, from oriented samples. One method for determining the structure is to find orientations of local molecular frames (peptide planes) with respect to the unit magnetic field direction, B0. This is done using equations that compute the coordinates of this vector in the frames. This requires an analysis of the PISEMA function and its degeneracies. As a measure of the sensitivity of peptide plane orientations to the data, we use these equations to derive a formula for the intensity function in the powder pattern. With this function and other measures, we investigate the effect of small changes in peptide plane orientations depending on the location of the resonances in the powder pattern spectrum. This gives us an indication of the change in lineshape due to mosaic spread and a way to interpret these in terms of an orientational error bar.

  13. Intensity and mosaic spread analysis from PISEMA tensors in solid-state NMR.

    PubMed

    Quine, J R; Achuthan, S; Asbury, T; Bertram, R; Chapman, M S; Hu, J; Cross, T A

    2006-04-01

    The solid-state NMR experiment PISEMA, is a technique for determining structures of proteins, especially membrane proteins, from oriented samples. One method for determining the structure is to find orientations of local molecular frames (peptide planes) with respect to the unit magnetic field direction, B0. This is done using equations that compute the coordinates of this vector in the frames. This requires an analysis of the PISEMA function and its degeneracies. As a measure of the sensitivity of peptide plane orientations to the data, we use these equations to derive a formula for the intensity function in the powder pattern. With this function and other measures, we investigate the effect of small changes in peptide plane orientations depending on the location of the resonances in the powder pattern spectrum. This gives us an indication of the change in lineshape due to mosaic spread and a way to interpret these in terms of an orientational error bar.

  14. Proton decoupling and recoupling under double-nutation irradiation in solid-state NMR

    NASA Astrophysics Data System (ADS)

    Takeda, Kazuyuki; Wakisaka, Asato; Takegoshi, K.

    2014-12-01

    The effect of 1H decoupling in magic-angle spinning solid-state NMR is studied under radiofrequency irradiation causing simultaneous nutations around a pair of orthogonal axes. Double-nutation with an arbitrary pair of nutation frequencies is implemented through modulation of the amplitude, phase, and frequency of the transmitting pulses. Similarity and difference of double-nutation decoupling and two-pulse phase-modulation decoupling schemes [A. E. Bennett, C. M. Rienstra, M. Auger, K. V. Lakshmi, and R. G. Griffin, J. Chem. Phys. 103, 6951-6958 (1995) and I. Scholz, P. Hodgkinson, B. H. Meier, and M. Ernst, J. Chem. Phys. 130, 114510 (2009)] are discussed. The structure of recoupling bands caused by interference of the 1H spin nutation with sample spinning is studied by both experiments and numerical simulations.

  15. Molecular dynamics of neutral polymer bonding agent (NPBA) as revealed by solid-state NMR spectroscopy.

    PubMed

    Hu, Wei; Su, Yongchao; Zhou, Lei; Pang, Aimin; Cai, Rulin; Ma, Xingang; Li, Shenhui

    2014-01-22

    Neutral polymer bonding agent (NPBA) is one of the most promising polymeric materials, widely used in nitrate ester plasticized polyether (NEPE) propellant as bonding agent. The structure and dynamics of NPBA under different conditions of temperatures and sample processing are comprehensively investigated by solid state NMR (SSNMR). The results indicate that both the main chain and side chain of NPBA are quite rigid below its glass transition temperature (Tg). In contrast, above the Tg, the main chain remains relatively immobilized, while the side chains become highly flexible, which presumably weakens the interaction between bonding agent and the binder or oxidant fillers and in turn destabilizes the high modulus layer formed around the oxidant fillers. In addition, no obvious variation is found for the microstructure of NPBA upon aging treatment or soaking with acetone. These experimental results provide useful insights for understanding the structural properties of NPBA and its interaction with other constituents of solid composite propellants under different processing and working conditions.

  16. Proton decoupling and recoupling under double-nutation irradiation in solid-state NMR

    SciTech Connect

    Takeda, Kazuyuki Wakisaka, Asato; Takegoshi, K.

    2014-12-14

    The effect of {sup 1}H decoupling in magic-angle spinning solid-state NMR is studied under radiofrequency irradiation causing simultaneous nutations around a pair of orthogonal axes. Double-nutation with an arbitrary pair of nutation frequencies is implemented through modulation of the amplitude, phase, and frequency of the transmitting pulses. Similarity and difference of double-nutation decoupling and two-pulse phase-modulation decoupling schemes [A. E. Bennett, C. M. Rienstra, M. Auger, K. V. Lakshmi, and R. G. Griffin, J. Chem. Phys. 103, 6951–6958 (1995) and I. Scholz, P. Hodgkinson, B. H. Meier, and M. Ernst, J. Chem. Phys. 130, 114510 (2009)] are discussed. The structure of recoupling bands caused by interference of the {sup 1}H spin nutation with sample spinning is studied by both experiments and numerical simulations.

  17. Natural abundance 14N and 15N solid-state NMR of pharmaceuticals and their polymorphs

    DOE PAGES

    Veinberg, Stanislav L.; Johnston, Karen E.; Jaroszewicz, Michael J.; ...

    2016-06-08

    14N ultra-wideline (UW), 1H{15N} indirectly-detected HETCOR (idHETCOR) and 15N dynamic nuclear polarization (DNP) solid-state NMR (SSNMR) experiments, in combination with plane-wave density functional theory (DFT) calculations of 14N EFG tensors, were utilized to characterize a series of nitrogen-containing active pharmaceutical ingredients (APIs), including HCl salts of scopolamine, alprenolol, isoprenaline, acebutolol, dibucaine, nicardipine, and ranitidine. Here, a case study applying these methods for the differentiation of polymorphs of bupivacaine HCl is also presented. All experiments were conducted upon samples with naturally-abundant nitrogen isotopes. For most of the APIs, it was possible to acquire frequency-stepped UW 14N SSNMR spectra of stationarymore » samples, which display powder patterns corresponding to pseudo-tetrahedral (i.e., RR'R"NH+ and RR'NH2+) or other (i.e., RNH2 and RNO2) nitrogen environments.« less

  18. Folding of xylan onto cellulose fibrils in plant cell walls revealed by solid-state NMR

    NASA Astrophysics Data System (ADS)

    Simmons, Thomas J.; Mortimer, Jenny C.; Bernardinelli, Oigres D.; Pöppler, Ann-Christin; Brown, Steven P.; Deazevedo, Eduardo R.; Dupree, Ray; Dupree, Paul

    2016-12-01

    Exploitation of plant lignocellulosic biomass is hampered by our ignorance of the molecular basis for its properties such as strength and digestibility. Xylan, the most prevalent non-cellulosic polysaccharide, binds to cellulose microfibrils. The nature of this interaction remains unclear, despite its importance. Here we show that the majority of xylan, which forms a threefold helical screw in solution, flattens into a twofold helical screw ribbon to bind intimately to cellulose microfibrils in the cell wall. 13C solid-state magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, supported by in silico predictions of chemical shifts, shows both two- and threefold screw xylan conformations are present in fresh Arabidopsis stems. The twofold screw xylan is spatially close to cellulose, and has similar rigidity to the cellulose microfibrils, but reverts to the threefold screw conformation in the cellulose-deficient irx3 mutant. The discovery that induced polysaccharide conformation underlies cell wall assembly provides new principles to understand biomass properties.

  19. A solid-state NMR method to determine domain sizes in multi-component polymer formulations

    NASA Astrophysics Data System (ADS)

    Schlagnitweit, Judith; Tang, Mingxue; Baias, Maria; Richardson, Sara; Schantz, Staffan; Emsley, Lyndon

    2015-12-01

    Polymer domain sizes are related to many of the physical properties of polymers. Here we present a solid-state NMR experiment that is capable of measuring domain sizes in multi-component mixtures. The method combines selective excitation of carbon magnetization to isolate a specific component with proton spin diffusion to report on domain size. We demonstrate the method in the context of controlled release formulations, which represents one of today's challenges in pharmaceutical science. We show that we can measure domain sizes of interest in the different components of industrial pharmaceutical formulations at natural isotopic abundance containing various (modified) cellulose derivatives, such as microcrystalline cellulose matrixes that are film-coated with a mixture of ethyl cellulose (EC) and hydroxypropyl cellulose (HPC).

  20. Formation of Organic Molecular Nanocrystals under Rigid Confinement with Analysis by Solid State NMR.

    PubMed

    Yang, X; Ong, T C; Michaelis, V K; Heng, S; Huang, J; Griffin, R G; Myerson, A S

    2014-10-21

    Crystallization in rigid confinement is a promising method to obtain organic molecular nanocrystals. However, the crystallization behavior and the related characterization methods are not well studied. Here we present a systematic study of the nucleation of organic molecular nanocrystals in rigid pores. Four different compounds were studied, ibuprofen, fenofibrate, griseofulvin, and indomethacin, which range from simple to complex molecules. Solid-state Nuclear Magnetic Resonance (NMR) was employed to analyse the structure of these compounds inside pores which are difficult to characterize by other analytical methods. We successfully demonstrated the production of nano-crystalline ibuprofen, fenofibrate and griseofulvin in porous silica particles with ~ 40 nm pores. These nanocrystals showed significant enhancement in dissolution rates. These results help advance the fundamental understanding of nucleation under rigid confinement and may lead to potential applications in developing new formulations in the pharmaceutical industry.

  1. Structural studies of methyl brevifolincarboxylate in solid state by means of NMR spectroscopy and DFT calculations

    NASA Astrophysics Data System (ADS)

    Wolniak, Michał; Tomczyk, Michał; Gudej, Jan; Wawer, Iwona

    2006-12-01

    Methyl brevifolincarboxylate isolated from the herb of Potentilla argentea L. (Rosaceae) is a representative of the naturally occurring polyphenols. The compound is of pharmaceutical interest mainly because of its antiviral and antioxidant properties. 13C NMR spectra were recorded for solution and solid phase. 13C CPMAS spectra were assigned by comparison with solution data, dipolar dephasing and short contact time experiments. The correctness of assignments was verified by GIAO DFT calculations of shielding constants. The differences between the solution and solid state chemical shift values were explained in terms of orientation of OH groups and intramolecular hydrogen bonds. The splitting of the C1 dbnd O resonance shows that there exists a polymorphism in the solid phase, which might be due to the formation of intramolecular hydrogen bond involving carbonyl or methoxy oxygen (i.e. C10 sbnd OH⋯O dbnd C or C10 sbnd OH⋯OCH 3).

  2. Orientational order of Australian spider silks as determined by solid-state NMR.

    PubMed

    Bonev, B; Grieve, S; Herberstein, M E; Kishore, A I; Watts, A; Separovic, F

    2006-06-05

    A simple solid-state NMR method was used to study the structure of (13)C- and (15)N-enriched silk from two Australian orb-web spider species, Nephila edulis and Argiope keyserlingi. Carbon-13 and (15)N spectra from alanine- or glycine-labeled oriented dragline silks were acquired with the fiber axis aligned parallel or perpendicular to the magnetic field. The fraction of oriented component was determined from each amino acid, alanine and glycine, using each nucleus independently, and attributed to the ordered crystalline domains in the silk. The relative fraction of ordered alanine was found to be higher than the fraction of ordered glycine, akin to the observation of alanine-rich domains in silk-worm (Bombyx mori) silk. A higher degree of crystallinity was observed in the dragline silk of N. edulis compared with A. keyserlingi, which correlates with the superior mechanical properties of the former.

  3. Formation of Organic Molecular Nanocrystals under Rigid Confinement with Analysis by Solid State NMR

    PubMed Central

    Yang, X.; Ong, T. C.; Michaelis, V. K.; Heng, S.; Huang, J.; Griffin, R. G.; Myerson, A. S.

    2014-01-01

    Crystallization in rigid confinement is a promising method to obtain organic molecular nanocrystals. However, the crystallization behavior and the related characterization methods are not well studied. Here we present a systematic study of the nucleation of organic molecular nanocrystals in rigid pores. Four different compounds were studied, ibuprofen, fenofibrate, griseofulvin, and indomethacin, which range from simple to complex molecules. Solid-state Nuclear Magnetic Resonance (NMR) was employed to analyse the structure of these compounds inside pores which are difficult to characterize by other analytical methods. We successfully demonstrated the production of nano-crystalline ibuprofen, fenofibrate and griseofulvin in porous silica particles with ~ 40 nm pores. These nanocrystals showed significant enhancement in dissolution rates. These results help advance the fundamental understanding of nucleation under rigid confinement and may lead to potential applications in developing new formulations in the pharmaceutical industry. PMID:25258590

  4. Solid-state NMR studies of proteins immobilized on inorganic surfaces

    DOE PAGES

    Shaw, Wendy J.

    2014-10-29

    Solid state NMR is the primary tool for studying the quantitative, site-specific structure, orientation, and dynamics of biomineralization proteins under biologically relevant conditions. Two calcium phosphate proteins, statherin and leucine rich amelogenin protein (LRAP), have been studied in depth and have different features, challenging our ability to extract design principles. More recent studies of the significantly larger full-length amelogenin represent a challenging but necessary step to ultimately investigate the full diversity of biomineralization proteins. Interactions of amino acids and silaffin peptide with silica are also being studied, along with qualitative studies of proteins interacting with calcium carbonate. Dipolar recoupling techniquesmore » have formed the core of the quantitative studies, yet, the need for isolated spin pairs makes this approach costly and time intensive. The use of multi-dimensional techniques is advancing, methodology which, despite its challenges with these difficult-to-study proteins, will continue to drive future advancements in this area.« less

  5. Solid-state NMR studies of proteins immobilized on inorganic surfaces

    SciTech Connect

    Shaw, Wendy J.

    2014-10-29

    Solid state NMR is the primary tool for studying the quantitative, site-specific structure, orientation, and dynamics of biomineralization proteins under biologically relevant conditions. Two calcium phosphate proteins, statherin and leucine rich amelogenin protein (LRAP), have been studied in depth and have different features, challenging our ability to extract design principles. More recent studies of the significantly larger full-length amelogenin represent a challenging but necessary step to ultimately investigate the full diversity of biomineralization proteins. Interactions of amino acids and silaffin peptide with silica are also being studied, along with qualitative studies of proteins interacting with calcium carbonate. Dipolar recoupling techniques have formed the core of the quantitative studies, yet, the need for isolated spin pairs makes this approach costly and time intensive. The use of multi-dimensional techniques is advancing, methodology which, despite its challenges with these difficult-to-study proteins, will continue to drive future advancements in this area.

  6. Sine-squared shifted pulses for recoupling interactions in solid-state NMR

    NASA Astrophysics Data System (ADS)

    Jain, Mukul G.; Rajalakshmi, G.; Equbal, Asif; Mote, Kaustubh R.; Agarwal, Vipin; Madhu, P. K.

    2017-06-01

    Rotational-Echo DOuble-Resonance (REDOR) is a versatile experiment for measuring internuclear distance between two heteronuclear spins in solid-state NMR. At slow to intermediate magic-angle spinning (MAS) frequencies, the measurement of distances between strongly coupled spins is challenging due to rapid dephasing of magnetisation. This problem can be remedied by employing the pulse-shifted version of REDOR known as Shifted-REDOR (S-REDOR) that scales down the recoupled dipolar coupling. In this study, we propose a new variant of the REDOR sequence where the positions of the π pulses are determined by a sine-squared function. This new variant has scaling properties similar to S-REDOR. We use theory, numerical simulations, and experiments to compare the dipolar recoupling efficiencies and the experimental robustness of the three REDOR schemes. The proposed variant has advantages in terms of radiofrequency field requirements at fast MAS frequencies.

  7. Solid-state NMR study of geopolymer prepared by sol-gel chemistry

    SciTech Connect

    Tsai, Yi-Ling; Hanna, John V.; Lee, Yuan-Ling; Smith, Mark E.; Chan, Jerry C.C.

    2010-12-15

    Geopolymers are a new class of materials formed by the condensation of aluminosilicates and silicates obtained from natural minerals or industrial wastes. In this work, the sol-gel method is used to synthesize precursor materials for the preparation of geopolymers. The geopolymer samples prepared by our synthetic route have been characterized by a series of physical techniques, including Fourier-transform infrared, X-ray diffraction, and multinuclear solid-state NMR. The results are very similar to those obtained for the geopolymers prepared from natural kaolinite. We believe that our synthetic approach can offer a good opportunity for the medical applications of geopolymer. -- Graphical abstract: Geopolymer prepared by the sol-gel route has the same spectroscopic properties as the sample prepared from the natural kaolinite. Display Omitted

  8. Spectral assignments and NMR parameter-structure relationships in borates using high-resolution 11B NMR and density functional theory.

    PubMed

    Alderman, Oliver L G; Iuga, Dinu; Howes, Andrew P; Pike, Kevin J; Holland, Diane; Dupree, Ray

    2013-06-07

    High-resolution, solid-state (11)B NMR spectra have been obtained at high magnetic fields for a range of polycrystalline borates using double-rotation (DOR), multiple-quantum magic angle spinning and isotopic dilution. DOR linewidths can be less than 0.2 ppm in isotopically diluted samples, allowing highly accurate values for the isotropic chemical shift, δiso, and electric field gradient to be obtained. The experimental values are used as a test of density functional calculations using both projector augmented wave based CASTEP and WIEN2k. The CASTEP calculations of δiso are generally in very good agreement with experiment, having r.m.s. deviation 0.40 ppm. WIEN2k calculations of electric field gradient magnitude, CQ, and asymmetry, η, are also in excellent agreement with experiment, with r.m.s. deviations 0.038 MHz and 0.042 respectively. However, whilst CASTEP gives a similar deviation for η (0.043) it overestimates CQ by ∼15%. After scaling of the calculated electric field gradient by 0.842 the deviation in CQ is practically identical to that of the WIEN2k calculations. The spectral assignments that follow from the experimental and computational results allow identification of correlations between δiso and (a) the average B-O-B bond angle, θ[combining overline], for both three and four coordinated boron, giving δiso(B(III)) = (185.1 -θ[combining overline])/3.42 ppm and δiso(B(IV)) = (130.2 -θ[combining overline])/5.31 ppm; and (b) the ring-site T(3) unit trigonal planar angular deviation, Stri, giving δiso(T(3)(ring)) = (1.642 × 10(-2)-Stri)/(8.339 × 10(-4)) ppm.

  9. Strong-coupling s-wave Superconductor MgB2 : ^11B NMR Study

    NASA Astrophysics Data System (ADS)

    Kotegawa, Hisashi; Ishida, Kenji; Kitaoka, Yoshio; Muranaka, Takahiro; Nakagawa, Norimasa; Takagiwa, Hiroyuki; Akimitsu, Jun

    2002-03-01

    We report nuclear magnetic resonance (NMR) results on the recently discovered superconductor MgB_2. This binary compound exhibits a remarkably high superconducting (SC) transition temperature, Tc of ~40K, and thus attracts a great deal of attention. Numerous theoretical and experimental approaches have been performed in order to investigate SC characteristics in this compound. We have investigated a SC gap structure of MgB2 through the measurement of ^11B nuclear spin-lattice relaxation time, T_1. ^11(1/T_1T) is independent of the temperature (T) in the normal state, and decreases exponentially in the SC state, accompanied with a tiny coherence peak just below T_c. The T dependence of 1/T_1T in the SC state can be accounted for by an s-wave SC model with a large gap size of 2Δ /k_BTc ~ 5 which suggests to be in a strong-coupling regime. We carried out the measurement in Al-doped Mg_1-xAl_xB_2. 1/T1 in the SC state revealed that the size in SC gap is not changed by substituting Al for Mg. The reduction in Tc is shown to be due to the decrease of N(E_F). According to the McMillan equation, the experimental relation between Tc and the relative change in N(E_F) allowed us to estimate a characteristic phonon frequency ω ~ 700K and an electron-phonon coupling constant λ ~ 0.87. These results suggest that the high-Tc superconductivity in MgB2 is mediated by the strong electron-phonon coupling with high-frequency phonons.

  10. Sparse (13)C labelling for solid-state NMR studies of P. pastoris expressed eukaryotic seven-transmembrane proteins.

    PubMed

    Liu, Jing; Liu, Chang; Fan, Ying; Munro, Rachel A; Ladizhansky, Vladimir; Brown, Leonid S; Wang, Shenlin

    2016-05-01

    We demonstrate a novel sparse (13)C labelling approach for methylotrophic yeast P. pastoris expression system, towards solid-state NMR studies of eukaryotic membrane proteins. The labelling scheme was achieved by co-utilizing natural abundance methanol and specifically (13)C labelled glycerol as carbon sources in the expression medium. This strategy improves the spectral resolution by 1.5 fold, displays site-specific labelling patterns, and has advantages for collecting long-range distance restraints for structure determination of large eukaryotic membrane proteins by solid-state NMR.

  11. Chemical reactivity of graphene oxide towards amines elucidated by solid-state NMR

    NASA Astrophysics Data System (ADS)

    Vacchi, Isabella A.; Spinato, Cinzia; Raya, Jésus; Bianco, Alberto; Ménard-Moyon, Cécilia

    2016-07-01

    Graphene oxide (GO) is an attractive nanomaterial for many applications. Controlling the functionalization of GO is essential for the design of graphene-based conjugates with novel properties. But, the chemical composition of GO has not been fully elucidated yet. Due to the high reactivity of the oxygenated moieties, mainly epoxy, hydroxyl and carboxyl groups, several derivatization reactions may occur concomitantly. The reactivity of GO with amine derivatives has been exploited in the literature to design graphene-based conjugates, mainly through amidation. However, in this study we undoubtedly demonstrate using magic angle spinning (MAS) solid-state NMR that the reaction between GO and amine functions occurs via ring opening of the epoxides, and not by amidation. We also prove that there is a negligible amount of carboxylic acid groups in two GO samples obtained by a different synthesis process, hence eliminating the possibility of amidation reactions with amine derivatives. This work brings additional insights into the chemical reactivity of GO, which is fundamental to control its functionalization, and highlights the major role of MAS NMR spectroscopy for a comprehensive characterization of derivatized GO.Graphene oxide (GO) is an attractive nanomaterial for many applications. Controlling the functionalization of GO is essential for the design of graphene-based conjugates with novel properties. But, the chemical composition of GO has not been fully elucidated yet. Due to the high reactivity of the oxygenated moieties, mainly epoxy, hydroxyl and carboxyl groups, several derivatization reactions may occur concomitantly. The reactivity of GO with amine derivatives has been exploited in the literature to design graphene-based conjugates, mainly through amidation. However, in this study we undoubtedly demonstrate using magic angle spinning (MAS) solid-state NMR that the reaction between GO and amine functions occurs via ring opening of the epoxides, and not by

  12. Solid-state NMR identification and quantification of newly formed aluminosilicate phases in weathered kaolinite systems.

    PubMed

    Crosson, Garry S; Choi, Sunkyung; Chorover, Jon; Amistadi, Mary Kay; O'Day, Peggy A; Mueller, Karl T

    2006-01-19

    The weathering of a specimen kaolinite clay was studied over the course of 369 d via solid-state 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and high-field 27Al MAS NMR. The chosen baseline solution conditions (0.05 mol kg-1 of Al, 2 mol kg-1 of Na+, 1 mol kg-1 of NO3-, 1 mol kg-1 of OH-, and pH approximately 13.8) approximate those of solutions leaking from waste tanks at the Hanford Site in Richland, WA. Nonradioactive Cs and Sr cations were added to this synthetic tank waste leachate (STWL) solution at concentrations of 10(-3), 10(-4), and 10(-5) molal (m) to represent their radionuclide counterparts. The transformations of silicon- and aluminum-containing solid phase species were monitored quantitatively by using NMR spectroscopy, with the resulting spectra directly reporting the influence of the initial Cs and Sr on formation and transformation of the neo-formed solids. At the lowest concentration of Cs and Sr employed (10(-5) m in each cation) peaks consistent with the formation of zeolite-like minerals were detected via 29Si and 27Al MAS NMR as early as 33 d. At concentrations of 10(-3) m in each cation, new silicon species are not detected until 93 d, although neophases containing four-coordinate aluminum were detectable at earlier reaction times via 27Al MAS NMR. At the highest magnetic field strengths employed in this NMR study, deconvolutions of resonances detected in the tetrahedral region of the 27Al MAS spectra yielded multiple components, indicating the existence of at least four new aluminum-containing phases. Two of these phases are identified as sodalite and cancrinite through comparison with diffuse-reflectance infrared (DRIFT) spectra and powder X-ray diffraction (XRD) results, while a third phase may correlate with a previously detected aluminum-rich chabazite phase. All measurable solid reaction products have been quantified via their 27Al MAS resonances acquired at high magnetic field strengths (17.6 T), and

  13. Solid-State NMR Identification and Quantification of Newly Formed Aluminosilicate Phases in Weathered Kaolinite Systems

    SciTech Connect

    Crosson, Garry S.; Choi, Sunkyung; Chorover, Jon; Amistadi, Mary K.; O'Day, Peggy A.; Mueller, Karl T.

    2006-01-19

    The weathering of a specimen kaolinite clay was studied over the course of 369 d via solid-state 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and high-field 27Al MAS NMR. The chosen baseline solution conditions (0.05 mol kg-1 of Al, 2 mol kg-1 of Na+, 1 mol kg-1 of NO3 -, 1 mol kg-1 of OH-, and pH ~13.8) approximate those of solutions leaking from waste tanks at the Hanford Site in Richland, WA. Nonradioactive Cs and Sr cations were added to this synthetic tank waste leachate (STWL) solution at concentrations of 10-3, 10-4, and 10-5 molal (m) to represent their radionuclide counterparts. The transformations of silicon- and aluminum-containing solid phase species were monitored quantitatively by using NMR spectroscopy, with the resulting spectra directly reporting the influence of the initial Cs and Sr on formation and transformation of the neo-formed solids. At the lowest concentration of Cs and Sr employed (10-5 m in each cation) peaks consistent with the formation of zeolite-like minerals were detected via 29Si and 27Al MAS NMR as early as 33 d. At concentrations of 10-3 m in each cation, new silicon species are not detected until 93 d, although neophases containing four-coordinate aluminum were detectable at earlier reaction times via 27Al MAS NMR. At the highest magnetic field strengths employed in this NMR study, deconvolutions of resonances detected in the tetrahedral region of the 27Al MAS spectra yielded multiple components, indicating the existence of at least four new aluminum-containing phases. Two of these phases are identified as sodalite and cancrinite through comparison with diffuse-reflectance infrared (DRIFT) spectra and powder X-ray diffraction (XRD) results, while a third phase may correlate with a previously detected aluminum-rich chabazite phase. All measurable solid reaction products have been quantified via their 27Al MAS resonances acquired at high magnetic field strengths (17.6 T), and the quantitative

  14. Solid state NMR method development and studies of biological and biomimetic nanocomposites

    SciTech Connect

    Hu, Yanyan

    2011-01-01

    This thesis describes application and development of advanced solid-state nuclear magnetic resonance techniques for complex materials, in particular organic-inorganic nanocomposites and thermoelectric tellurides. The apatite-collagen interface, essential for understanding the biomineralization process in bone and engineering the interface for controlled bio-mimetic synthesis and optimized mechanical properties, is buried within the nanocomposite of bone. We used multinuclear solid-state NMR to study the composition and structure of the interface. Citrate has been identified as the main organic molecule strongly bound to the apatite surface with a density of 1/(2 nm)2, covering 1/6 of the total surface area in bovine bone. Citrate provides more carboxylate groups, one of the key functional groups found to affect apatite nucleation and growth, than all the non-collagenous proteins all together in bone; thus we propose that citrate stabilizes apatite crystals at a very small thickness of ~3 nm (4 unit cells) to increase bone fracture tolerance. The hypothesis has been confirmed in vitro by adding citrate in the bio-mimetic synthesis of polymerhydroxyapatite nanocomposites. The results have shown that the size of hydroxyapatite nanocrystals decreases as increasing citrate concentration. With citrate concentrations comparable to that in body fluids, similar-sized nanocrystals as in bone have been produced. Besides the dimensions of the apatite crystals, the composition of bone also affects its biofunctional and macroscopic mechanical properties; therefore, our team also extended its effort to enhance the inorganic portion in our bio-mimetic synthesis from originally 15 wt% to current 50 wt% compared to 65 wt% in bovine bone, by using Lysine-Leucine hydroxyapatite nucleating diblock co-polypeptide, which forms a gel at very low concentration. In this thesis, various advanced solid state NMR techniques have been employed to characterize nanocomposites

  15. SIMPSON: A general simulation program for solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Bak, Mads; Rasmussen, Jimmy T.; Nielsen, Niels Chr.

    2011-12-01

    A computer program for fast and accurate numerical simulation of solid-state NMR experiments is described. The program is designed to emulate a NMR spectrometer by letting the user specify high-level NMR concepts such as spin systems, nuclear spin interactions, RF irradiation, free precession, phase cycling, coherence-order filtering, and implicit/explicit acquisition. These elements are implemented using the Tel scripting language to ensure a minimum of programming overhead and direct interpretation without the need for compilation, while maintaining the flexibility of a full-featured programming language. Basicly, there are no intrinsic limitations to the number of spins, types of interactions, sample conditions (static or spinning, powders, uniaxially oriented molecules, single crystals, or solutions), and the complexity or number of spectral dimensions for the pulse sequence. The applicability ranges from simple ID experiments to advanced multiple-pulse and multiple-dimensional experiments, series of simulations, parameter scans, complex data manipulation/visualization, and iterative fitting of simulated to experimental spectra. A major effort has been devoted to optimizing the computation speed using state-of-the-art algorithms for the time-consuming parts of the calculations implemented in the core of the program using the C programming language. Modification and maintenance of the program are facilitated by releasing the program as open source software (General Public License) currently at http://nmr.imsb.au.dk. The general features of the program are demonstrated by numerical simulations of various aspects for REDOR, rotational resonance, DRAMA, DRAWS, HORROR, C7, TEDOR, POST-C7, CW decoupling, TPPM, F-SLG, SLF, SEMA-CP, PISEMA, RFDR, QCPMG-MAS, and MQ-MAS experiments.

  16. SIMPSON: A General Simulation Program for Solid-State NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Bak, Mads; Rasmussen, Jimmy T.; Nielsen, Niels Chr.

    2000-12-01

    A computer program for fast and accurate numerical simulation of solid-state NMR experiments is described. The program is designed to emulate a NMR spectrometer by letting the user specify high-level NMR concepts such as spin systems, nuclear spin interactions, RF irradiation, free precession, phase cycling, coherence-order filtering, and implicit/explicit acquisition. These elements are implemented using the Tcl scripting language to ensure a minimum of programming overhead and direct interpretation without the need for compilation, while maintaining the flexibility of a full-featured programming language. Basicly, there are no intrinsic limitations to the number of spins, types of interactions, sample conditions (static or spinning, powders, uniaxially oriented molecules, single crystals, or solutions), and the complexity or number of spectral dimensions for the pulse sequence. The applicability ranges from simple 1D experiments to advanced multiple-pulse and multiple-dimensional experiments, series of simulations, parameter scans, complex data manipulation/visualization, and iterative fitting of simulated to experimental spectra. A major effort has been devoted to optimizing the computation speed using state-of-the-art algorithms for the time-consuming parts of the calculations implemented in the core of the program using the C programming language. Modification and maintenance of the program are facilitated by releasing the program as open source software (General Public License) currently at http://nmr.imsb.au.dk. The general features of the program are demonstrated by numerical simulations of various aspects for REDOR, rotational resonance, DRAMA, DRAWS, HORROR, C7, TEDOR, POST-C7, CW decoupling, TPPM, F-SLG, SLF, SEMA-CP, PISEMA, RFDR, QCPMG-MAS, and MQ-MAS experiments.

  17. Structural investigation of aluminium doped ZnO nanoparticles by solid-state NMR spectroscopy.

    PubMed

    Avadhut, Yamini S; Weber, Johannes; Hammarberg, Elin; Feldmann, Claus; Schmedt auf der Günne, Jörn

    2012-09-07

    The electrical conductivity of aluminium doped zinc oxide (AZO, ZnO:Al) materials depends on doping induced defects and grain structure. This study aims at relating macroscopic electrical conductivity of AZO nanoparticles with their atomic structure, which is non-trivial because the derived materials are heavily disordered and heterogeneous in nature. For this purpose we synthesized AZO nanoparticles with different doping levels and narrow size distribution by a microwave assisted polyol method followed by drying and a reductive treatment with forming gas. From these particles electrically conductive, optically transparent films were obtained by spin-coating. Characterization involved energy-dispersive X-ray analysis, wet chemical analysis, X-ray diffraction, electron microscopy and dynamic light scattering, which provided a basis for a detailed structural solid-state NMR study. A multinuclear ((27)Al, (13)C, (1)H) spectroscopic investigation required a number of 1D MAS NMR and 2D MAS NMR techniques (T(1)-measurements, (27)Al-MQMAS, (27)Al-(1)H 2D-PRESTO-III heteronuclear correlation spectroscopy), which were corroborated by quantum chemical calculations with an embedded cluster method (EEIM) at the DFT level. From the combined data we conclude that only a small part of the provided Al is incorporated into the ZnO structure by substitution of Zn. The related (27)Al NMR signal undergoes a Knight shift when the material is subjected to a reductive treatment with forming gas. At higher (formal) doping levels Al forms insulating (Al, H and C containing) side-phases, which cover the surface of the ZnO:Al particles and increase the sheet resistivity of spin-coated material. Moreover, calculated (27)Al quadrupole coupling constants serve as a spectroscopic fingerprint by which previously suggested point-defects can be identified and in their great majority be ruled out.

  18. Studying Dynamics by Magic-Angle Spinning Solid-State NMR Spectroscopy: Principles and Applications to Biomolecules

    PubMed Central

    Schanda, Paul; Ernst, Matthias

    2016-01-01

    Magic-angle spinning solid-state NMR spectroscopy is an important technique to study molecular structure, dynamics and interactions, and is rapidly gaining importance in biomolecular sciences. Here we provide an overview of experimental approaches to study molecular dynamics by MAS solid-state NMR, with an emphasis on the underlying theoretical concepts and differences of MAS solid-state NMR compared to solution-state NMR. The theoretical foundations of nuclear spin relaxation are revisited, focusing on the particularities of spin relaxation in solid samples under magic-angle spinning. We discuss the range of validity of Redfield theory, as well as the inherent multi-exponential behavior of relaxation in solids. Experimental challenges for measuring relaxation parameters in MAS solid-state NMR and a few recently proposed relaxation approaches are discussed, which provide information about time scales and amplitudes of motions ranging from picoseconds to milliseconds. We also discuss the theoretical basis and experimental measurements of anisotropic interactions (chemical-shift anisotropies, dipolar and quadrupolar couplings), which give direct information about the amplitude of motions. The potential of combining relaxation data with such measurements of dynamically-averaged anisotropic interactions is discussed. Although the focus of this review is on the theoretical foundations of dynamics studies rather than their application, we close by discussing a small number of recent dynamics studies, where the dynamic properties of proteins in crystals are compared to those in solution. PMID:27110043

  19. Preparation of uniformly isotope labeled KcsA for solid state NMR: Expression, purification, reconstitution into liposomes and functional assay

    PubMed Central

    Bhate, Manasi P.; Wylie, Benjamin J.; Thompson, Ameer; Tian, Lin; Nimigean, Crina; McDermott, Ann E.

    2013-01-01

    We report the expression, purification, liposome reconstitution and functional validation of uniformly 13C and 15N isotope labeled KcsA, a bacterial potassium channel that has high homology with mammalian channels, for solid-state NMR studies. The expression and purification is optimized for an average yield of ~ 35–40 milligrams per liter of M9 media in a time-efficient way. The protein purity is confirmed by gel electrophoresis and the protein concentration is quantified by UV-Vis absorption spectroscopy. Protocols to efficiently reconstitute KcsA into liposomes are also presented. The presence of liposomes is confirmed by cryo-electron microscopy images and the effect of magic angle spinning on liposome packing is shown. High-resolution solid-state NMR spectra of uniformly isotope labeled KcsA in these liposomes reveal that our protocol yields to a very homogenous KcsA sample with high signal to noise and several well-resolved residues in NMR spectra. Electrophysiology of our samples before and after solid-state NMR show that channel function and selectivity remain intact after the solid-state NMR. PMID:23916531

  20. Solid-State 17O NMR Study of Benzoic Acid Adsorption On Metal Oxide Surfaces

    SciTech Connect

    Hagaman, Edward {Ed} W; Chen, Banghao; Jiao, Jian; Parsons, Williams

    2012-01-01

    Solid-state 17O NMR spectra of 17O-labeled benzoic and anisic acids are reported and benzoic acid is used to probe the surface of metal oxides. Complexes formed when benzoic acid is dry-mixed with mesoporous silica, and nonporous titania and alumina are characterized. Chemical reactions with silica are not observed. The nature of benzoic acid on silica is a function of the water content of the oxide. The acid disperses in the pores of the silica if the silica is in equilibrium with ambient laboratory humidity. The acid displays high mobility as evidenced by a liquid-like, Lorentzian resonance. Excess benzoic acid remains as the crystalline hydrogen-bonded dimer. Benzoic acid reacts with titania and alumina surfaces in equilibrium with laboratory air to form the corresponding titanium and aluminum benzoates. In both materials the oxygen of the 17O-labeled acid is bound to the metal, showing the reaction proceeds by bond formation between oxygen deficient metal sites and the oxygen of the carboxylic acid. 27Al MAS NMR confirms this mechanism for the reaction on alumina. Dry mixing of benzoic acid with alumina rapidly quenches pentacoordinate aluminum sites, excellent evidence that these sites are confined to the surface of the alumina particles.

  1. Origin of the different emission wavelengths in Alq 3 analyzed by solid-state NMR

    NASA Astrophysics Data System (ADS)

    Kaji, Hironori; Fukushima, Tatsuya; Takami, Kousuke; Kusaka, Yasunari

    2007-09-01

    Tris(8-hydroxyquinoline) aluminum(III) (Alq 3) is one of the most widely used materials in organic light-emitting diodes (OLEDs), and the relationship between the structures and the luminescent wavelengths is of recent interest; yellowish-green emissions are observed for the α- and amorphous Alq 3, whereas blue emissions are found for the γ- and δ-Alq 3. In order to clarify the relationship between the structures and the emission wavelengths, we carried out solid-state nuclear magnetic resonance (NMR) experiments on the different polymorphs of Alq 3 and the amorphous state. Based on 27Al and 13C magic angle spinning (MAS) NMR experiments, it is found that the isomeric state of the amorphous Alq 3 is the same as that of α-Alq 3 and is different from those of γ- and δ-Alq 3. Not only for the amorphous, but also for α-Alq 3, the local structures are found to be disordered. We also obtained clear evidence that γ-Alq 3 is in the facial isomeric state. It is suggested that δ-Alq 3 is also facial. The difference between γ- and δ-Alq 3 is the intermolecular packing; the effect of intermolecular packing is found only for δ-Alq 3. A further confirmation of the isomeric states of these Alq 3 samples is obtained from temperature-dependent X-ray diffraction experiments.

  2. Solid-state NMR reveals differential carbohydrate utilization in diapausing Culex pipiens

    PubMed Central

    Chang, James; Singh, Jugeshwar; Kim, Sungshil; Hockaday, William C.; Sim, Cheolho; Kim, Sung Joon

    2016-01-01

    Culex pipiens is the mosquito that vectors West Nile Virus and other human-pathogenic flavivruses in North America. In response to shortened day length and lower temperatures, female Cx. pipiense prepares for the diapause by actively feeding on carbohydrates to increase the biosynthesis of glycogen and lipid to store energy for overwintering. The effect of feeding different carbohydrates on glycogen and lipid biosynthesis in diapausing mosquitoes was investigated in vivo using 13C solid-state NMR. Diapause-destined adult females and nondiapausing counterparts after adult eclosion were fed with three different carbohydrate sources for 7 days: 1) 10% sucrose, 2) 10% D-[13C6]glucose, and 3) 1% D-[13C6]glucose co-provisioned with 10% sucrose. NMR measurements show that sucrose and glucose are metabolized differently in diapausing mosquitoes. Mosquitoes fed on sucrose primarily accumulate glycogen with increased branching structures, but less of lipids. In contrast, mosquitoes fed exclusively on glucose show accumulation of both glycogen and lipid with increased aliphatic chain length. Glucose is exclusively metabolized for the biosynthesis of triacylglyceride when mosquitoes were co-fed with sucrose. Our findings provide novel insights into the insect carbohydrate metabolism that governs glycogen and lipid biosynthesis during diapause, which is fundamental for the insect survival during inimical environments. PMID:27853281

  3. Detection of chiral defects in crystalline organic solids using solid-state NMR spectroscopy.

    PubMed

    Berendt, Robert T; Munson, Eric J

    2011-05-01

    The marketing of enantiopure pharmaceuticals has become more common due to regulatory and safety concerns surrounding the potential differences in biological activity of opposite enantiomers. However, achieving the desired enantiopurity can be a challenge, and low levels of the undesired enantiomer (chiral impurity) may be present in the final product. The location and nature of this impurity can potentially alter pharmaceutically relevant properties. In this article, we show that it is possible to identify and quantitate the crystallographic locations of small amounts of one enantiomer (l) in the presence of predominantly the opposite D-enantiomer using solid-state nuclear magnetic resonance (NMR) spectroscopy. Proline was used as a model compound, and crystalline samples containing both D- and L-proline were prepared by solvent evaporation, lyophilization, spray drying, and cryogrinding. Isotopic labeling, (13)C cross polarization-magic angle spinning NMR spectral subtractions, and (1)H T(1) spin-lattice relaxation measurements allowed selective observation and characterization of the crystal environments into which the L-proline impurity was incorporated upon concurrent crystallization with D-proline. Results show that L-proline was incorporated in up to four different crystalline forms, including L-proline as a kinetically trapped substitutional chiral defect in the D-proline host crystal lattice.

  4. Solid state NMR methods for coal science. Progress report, July 1, 1983-September 31, 1984

    SciTech Connect

    Zilm, K.W.

    1984-12-01

    This report covers the progress made on the title project during the last quarter. While a good deal of our time has been spent setting up our new NMR laboratory, we have made several significant advances in solid state NMR technique development that will have important applications in structure determination of coal, coal products and other fossil fuels. We have developed a CP/MAS probe that is routinely capable of producing decoupling fields in excess of 100 KHz without excessive power consumption and that has a very homogeneous radio frequency field. This piece of equipment has proven crucial to the success of a number of new techniques we are developing. In addition to increasing our sensitivity, the intensity, and homogeneity of the R.F. field, this probe now makes a number of multiple pulse techniques feasible. One avenue that has been pursued this quarter is understanding how to better decouple and thus increase the resolution of /sup 13/C CP/MAS spectra. It has been found that improved decoupling does lead to an increase in resolution in coal C-13 CP-MAS spectra. Preliminary results indicate it is now possible to resolve four bands in the aliphatic region and to substantially narrow CH/sub 2/ resonances in whole coals. 4 figures.

  5. Wheat bran biodegradation by Pleurotus ostreatus: a solid-state carbon-13 NMR study.

    PubMed

    Locci, Emanuela; Laconi, Samuela; Pompei, Raffaello; Scano, Paola; Lai, Adolfo; Marincola, Flaminia Cesare

    2008-07-01

    Solid-state (13)C nuclear magnetic resonance (NMR) and elemental analysis techniques were used to monitor the degradation of wheat bran by the white-rot fungus Pleurotus ostreatus during a 62-day cultivation period. The weight loss and in vitro organic matter digestibility of the substrate were also evaluated after fungal treatment. The (13)C NMR spectra of degraded wheat bran samples showed a lower content in carbohydrates and a higher content in aliphatic and carboxylic groups than the untreated control sample. In parallel, changes in the wheat bran elemental composition evidenced a decrease in carbon content and a concomitant increase in nitrogen and oxygen content during mycelium growth. These results clearly indicate the occurrence of progressive changes in the composition of wheat bran during fungal treatment and are interpreted in terms of preferential degradation of amorphous vs. crystalline polysaccharides by the fungal mycelium and accumulation of proteins in the substrate. At the end of the cultivation period, the treated samples experienced an average weight loss of 20% and an increase in organic matter digestibility of 17%.

  6. Comparison among Magnus/Floquet/Fer expansion schemes in solid-state NMR

    SciTech Connect

    Takegoshi, K. Miyazawa, Norihiro; Sharma, Kshama; Madhu, P. K.

    2015-04-07

    We here revisit expansion schemes used in nuclear magnetic resonance (NMR) for the calculation of effective Hamiltonians and propagators, namely, Magnus, Floquet, and Fer expansions. While all the expansion schemes are powerful methods there are subtle differences among them. To understand the differences, we performed explicit calculation for heteronuclear dipolar decoupling, cross-polarization, and rotary-resonance experiments in solid-state NMR. As the propagator from the Fer expansion takes the form of a product of sub-propagators, it enables us to appreciate effects of time-evolution under Hamiltonians with different orders separately. While 0th-order average Hamiltonian is the same for the three expansion schemes with the three cases examined, there is a case that the 2nd-order term for the Magnus/Floquet expansion is different from that obtained with the Fer expansion. The difference arises due to the separation of the 0th-order term in the Fer expansion. The separation enables us to appreciate time-evolution under the 0th-order average Hamiltonian, however, for that purpose, we use a so-called left-running Fer expansion. Comparison between the left-running Fer expansion and the Magnus expansion indicates that the sign of the odd orders in Magnus may better be reversed if one would like to consider its effect in order.

  7. Solid-State NMR Study of Li-Assisted Dehydrogenation of Ammonia Borane

    SciTech Connect

    Kobayashi, Takeshi; Hlova, Ihor; Singh, Niraj; Pecharsky, Vitalij; Pruski, Marek

    2012-03-21

    The mechanism of thermochemical dehydrogenation of the 1:3 mixture of Li3AlH6 and NH3BH3 (AB) has been studied by the extensive use of solid-state NMR spectroscopy and theoretical calculations. The activation energy for the dehydrogenation is estimated to be 110 kJ mol–1, which is lower than for pristine AB (184 kJ mol–1). The major hydrogen release from the mixture occurs at 60 and 72 °C, which compares favorably with pristine AB and related hydrogen storage materials, such as lithium amidoborane (LiNH2BH3, LiAB). The NMR studies suggest that Li3AlH6 improves the dehydrogenation kinetics of AB by forming an intermediate compound (LiAB)x(AB)1–x. A part of AB in the mixture transforms into LiAB to form this intermediate, which accelerates the subsequent formation of branched polyaminoborane species and further release of hydrogen. The detailed reaction mechanism, in particular the role of lithium, revealed in the present study highlights new opportunities for using ammonia borane and its derivatives as hydrogen storage materials.

  8. Thin-film solid-state proton NMR measurements using a synthetic mica substrate: Polymer blends

    NASA Astrophysics Data System (ADS)

    VanderHart, David L.; Prabhu, Vivek M.; Lavery, Kristopher A.; Dennis, Cindi L.; Rao, Ashwin B.; Lin, Eric K.

    2009-11-01

    Solid-state proton nuclear magnetic resonance (NMR) measurements are performed successfully on polymer blend thin films through the use of synthetic mica as a substrate. When used as a substrate, synthetic fluorophlogopite mica with its proton-free, diamagnetic character, allows for adequate measurement sensitivity while minimally perturbing the proton thin-film spectra, especially relative to more commonly available natural micas. Specifically, we use multiple-pulse techniques in the presence of magic-angle spinning to measure the degree of mixing in two different polymer blend thin films, polystyrene/poly(xylylene ether) and poly(1-methyladamantyl methacrylate) (PMAdMA)/triphenylsulfonium perfluorobutanesulfonate (TPS-PFBS), spin-coated onto mica substrates. Our earlier studies had focused on bulk systems where NMR signals are stronger, but may not be representative of thin films of the same systems that are relevant to many applications such as photoresist formulations in the electronics industry. The superiority of synthetic over natural paramagnetic mica is demonstrated by the maintenance of resolution and spinning sideband intensities (relative to bulk samples) for the synthetic mica samples. In contrast, degraded resolution and large spinning sidebands are shown to typify spectra of the natural mica samples. This approach can be applied to many other proton measurements of solid thin films, thereby greatly extending the types of systems to be investigated. Magnetic susceptibility measurements are also reported for all micas used.

  9. Thin-film solid-state proton NMR measurements using a synthetic mica substrate: polymer blends.

    PubMed

    VanderHart, David L; Prabhu, Vivek M; Lavery, Kristopher A; Dennis, Cindi L; Rao, Ashwin B; Lin, Eric K

    2009-11-01

    Solid-state proton nuclear magnetic resonance (NMR) measurements are performed successfully on polymer blend thin films through the use of synthetic mica as a substrate. When used as a substrate, synthetic fluorophlogopite mica with its proton-free, diamagnetic character, allows for adequate measurement sensitivity while minimally perturbing the proton thin-film spectra, especially relative to more commonly available natural micas. Specifically, we use multiple-pulse techniques in the presence of magic-angle spinning to measure the degree of mixing in two different polymer blend thin films, polystyrene/poly(xylylene ether) and poly(1-methyladamantyl methacrylate) (PMAdMA)/triphenylsulfonium perfluorobutanesulfonate (TPS-PFBS), spin-coated onto mica substrates. Our earlier studies had focused on bulk systems where NMR signals are stronger, but may not be representative of thin films of the same systems that are relevant to many applications such as photoresist formulations in the electronics industry. The superiority of synthetic over natural paramagnetic mica is demonstrated by the maintenance of resolution and spinning sideband intensities (relative to bulk samples) for the synthetic mica samples. In contrast, degraded resolution and large spinning sidebands are shown to typify spectra of the natural mica samples. This approach can be applied to many other proton measurements of solid thin films, thereby greatly extending the types of systems to be investigated. Magnetic susceptibility measurements are also reported for all micas used.

  10. Characterisation of pitch fractions by quantitative solid state {sup 13}C NMR

    SciTech Connect

    Andresen, J.M.; Dennison, P.R.; Maroto-Valer, M.M.

    1994-12-31

    Thermal and other pretreatments of pitch fractions are being widely investigated as a means to increase the extent of mesophase formation in relation to the production of high performance carbons. The structural changes that occur can be assessed using carbon skeletal parameters but, although solid state {sup 13}C NMR has been used for this purpose, the quantitative reliability of the technique has still to be established for pitch fractions. It was demonstrated previously that, as for coals, cross-polarisation (CP) can vastly underestimate quaternary aromatic carbon concentrations. A combination of a low magnetic field strength to avoid problems with spinning sidebands and the simple Bloch decay or single pulse excitation (SPE) technique is now generally recognised as offering the most satisfactory approach for obtaining quantitative {sup 13}C NMR results for coals and related materials. In this study, single pulse excitation (SPE) and associated relaxation measurements have been conducted at low field on coal-derived pitches and their toluene-insoluble (TI) fractions, together with a biomass-derived pitch and the results compared with those from CP.

  11. Chemical reactivity of graphene oxide towards amines elucidated by solid-state NMR.

    PubMed

    Vacchi, Isabella A; Spinato, Cinzia; Raya, Jésus; Bianco, Alberto; Ménard-Moyon, Cécilia

    2016-07-14

    Graphene oxide (GO) is an attractive nanomaterial for many applications. Controlling the functionalization of GO is essential for the design of graphene-based conjugates with novel properties. But, the chemical composition of GO has not been fully elucidated yet. Due to the high reactivity of the oxygenated moieties, mainly epoxy, hydroxyl and carboxyl groups, several derivatization reactions may occur concomitantly. The reactivity of GO with amine derivatives has been exploited in the literature to design graphene-based conjugates, mainly through amidation. However, in this study we undoubtedly demonstrate using magic angle spinning (MAS) solid-state NMR that the reaction between GO and amine functions occurs via ring opening of the epoxides, and not by amidation. We also prove that there is a negligible amount of carboxylic acid groups in two GO samples obtained by a different synthesis process, hence eliminating the possibility of amidation reactions with amine derivatives. This work brings additional insights into the chemical reactivity of GO, which is fundamental to control its functionalization, and highlights the major role of MAS NMR spectroscopy for a comprehensive characterization of derivatized GO.

  12. Heat Management Strategies for Solid-state NMR of Functional Proteins

    PubMed Central

    Fowler, Daniel J.; Harris, Michael J.; Thompson, Lynmarie K.

    2012-01-01

    Modern solid-state NMR methods can acquire high-resolution protein spectra for structure determination. However, these methods use rapid sample spinning and intense decoupling fields that can heat and denature the protein being studied. Here we present a strategy to avoid destroying valuable samples. We advocate first creating a sacrificial sample, which contains unlabeled protein (or no protein) in buffer conditions similar to the intended sample. This sample is then doped with the chemical shift thermometer Sm2Sn2O7. We introduce a pulse scheme called TCUP (for Temperature Calibration Under Pulseload) that can characterize the heating of this sacrificial sample rapidly, under a variety of experimental conditions, and with high temporal resolution. Sample heating is discussed with respect to different instrumental variables such as spinning speed, decoupling strength and duration, and cooling gas flow rate. The effects of different sample preparation variables are also discussed, including ionic strength, the inclusion of cryoprotectants, and the physical state of the sample (i.e. liquid, solid, or slurry). Lastly, we discuss probe detuning as a measure of sample thawing that does not require retuning the probe or using chemical shift thermometer compounds. Use of detuning tests and chemical shift thermometers with representative sample conditions makes it possible to maximize the efficiency of the NMR experiment while retaining a functional sample. PMID:22868258

  13. Suppressing background signals in solid state NMR via the Electronic Mixing-Mediated Annihilation (EMMA) method.

    PubMed

    Mollica, Giulia; Ziarelli, Fabio; Tintaru, Aura; Thureau, Pierre; Viel, Stéphane

    2012-05-01

    A simple procedure to effectively suppress background signals arising from various probe head components (e.g. stator, rotors, inserts) in solid state NMR is presented. Similarly to the ERETIC™ method, which uses an electronic signal as an internal standard for quantification, the proposed scheme is based on an electronically generated time-dependent signal that is injected into the receiver coil of the NMR probe head during signal acquisition. More specifically, the line shape, width and frequency of this electronic signal are determined by deconvoluting the background signal in the frequency domain. This deconvoluted signal is then converted into a time-dependent function through inverse Fourier Transform, which is used to generate the shaped pulse that is fed into the receiver coil during the acquisition of the Free Induction Decay. The power of the shaped pulse is adjusted to match the intensity of the background signal, and its phase is shifted by 180° with respect to the receiver reference phase. This so-called Electronic Mixing-Mediated Annihilation (EMMA) methodology is demonstrated here with a (13)C Single Pulse Magic Angle Spinning spectrum of an isotopically enriched (13)C histidine solid sample recorded under quantitative conditions. Copyright © 2012 Elsevier Inc. All rights reserved.

  14. Suppressing background signals in solid state NMR via the Electronic Mixing-Mediated Annihilation (EMMA) method

    NASA Astrophysics Data System (ADS)

    Mollica, Giulia; Ziarelli, Fabio; Tintaru, Aura; Thureau, Pierre; Viel, Stéphane

    2012-05-01

    A simple procedure to effectively suppress background signals arising from various probe head components (e.g. stator, rotors, inserts) in solid state NMR is presented. Similarly to the ERETIC™ method, which uses an electronic signal as an internal standard for quantification, the proposed scheme is based on an electronically generated time-dependent signal that is injected into the receiver coil of the NMR probe head during signal acquisition. More specifically, the line shape, width and frequency of this electronic signal are determined by deconvoluting the background signal in the frequency domain. This deconvoluted signal is then converted into a time-dependent function through inverse Fourier Transform, which is used to generate the shaped pulse that is fed into the receiver coil during the acquisition of the Free Induction Decay. The power of the shaped pulse is adjusted to match the intensity of the background signal, and its phase is shifted by 180° with respect to the receiver reference phase. This so-called Electronic Mixing-Mediated Annihilation (EMMA) methodology is demonstrated here with a 13C Single Pulse Magic Angle Spinning spectrum of an isotopically enriched 13C histidine solid sample recorded under quantitative conditions.

  15. Heat management strategies for solid-state NMR of functional proteins.

    PubMed

    Fowler, Daniel J; Harris, Michael J; Thompson, Lynmarie K

    2012-09-01

    Modern solid-state NMR methods can acquire high-resolution protein spectra for structure determination. However, these methods use rapid sample spinning and intense decoupling fields that can heat and denature the protein being studied. Here we present a strategy to avoid destroying valuable samples. We advocate first creating a sacrificial sample, which contains unlabeled protein (or no protein) in buffer conditions similar to the intended sample. This sample is then doped with the chemical shift thermometer Sm2Sn2O7. We introduce a pulse scheme called TCUP (for Temperature Calibration Under Pulseload) that can characterize the heating of this sacrificial sample rapidly, under a variety of experimental conditions, and with high temporal resolution. Sample heating is discussed with respect to different instrumental variables such as spinning speed, decoupling strength and duration, and cooling gas flow rate. The effects of different sample preparation variables are also discussed, including ionic strength, the inclusion of cryoprotectants, and the physical state of the sample (i.e. liquid, solid, or slurry). Lastly, we discuss probe detuning as a measure of sample thawing that does not require retuning the probe or using chemical shift thermometer compounds. Use of detuning tests and chemical shift thermometers with representative sample conditions makes it possible to maximize the efficiency of the NMR experiment while retaining a functional sample.

  16. Probing Silica-Biomolecule Interactions by Solid-State NMR and Molecular Dynamics Simulations.

    PubMed

    Brückner, Stephan Ingmar; Donets, Sergii; Dianat, Arezoo; Bobeth, Manfred; Gutiérrez, Rafael; Cuniberti, Gianaurelio; Brunner, Eike

    2016-11-08

    Understanding the molecular interactions between inorganic phases such as silica and organic material is fundamental for chromatographic applications, for tailoring silica-enzyme interactions, and for elucidating the mechanisms of biomineralization. The formation, structure, and properties of the organic/inorganic interface is crucial in this context. Here, we investigate the interaction of selectively (13)C-labeled choline with (29)Si-labeled monosilicic acid/silica at the molecular level. Silica/choline nanocomposites were analyzed by solid-state NMR spectroscopy in combination with extended molecular dynamics (MD) simulations to understand the silica/organic interface. Cross-polarization magic angle spinning (CP MAS)-based NMR experiments like (1)H-(13)C CP-REDOR (rotational-echo double resonance), (1)H-(13)C HETCOR (heteronuclear correlation), and (1)H-(29)Si-(1)H double CP are employed to determine spatial parameters. The measurement of (29)Si-(13)C internuclear distances for selectively (13)C-labeled choline provides an experimental parameter that allows the direct verification of MD simulations. Atomistic modeling using classical MD methodologies is performed using the INTERFACE force field. The modeling results are in excellent agreement with the experimental data and reveal the relevant molecular conformations as well as the nature and interplay of the interactions between the choline cation and the silica surface. Electrostatic interactions and hydrogen bonding are both important and depend strongly on the hydration level as well as the charge state of the silica surface.

  17. Comparison among Magnus/Floquet/Fer expansion schemes in solid-state NMR

    NASA Astrophysics Data System (ADS)

    Takegoshi, K.; Miyazawa, Norihiro; Sharma, Kshama; Madhu, P. K.

    2015-04-01

    We here revisit expansion schemes used in nuclear magnetic resonance (NMR) for the calculation of effective Hamiltonians and propagators, namely, Magnus, Floquet, and Fer expansions. While all the expansion schemes are powerful methods there are subtle differences among them. To understand the differences, we performed explicit calculation for heteronuclear dipolar decoupling, cross-polarization, and rotary-resonance experiments in solid-state NMR. As the propagator from the Fer expansion takes the form of a product of sub-propagators, it enables us to appreciate effects of time-evolution under Hamiltonians with different orders separately. While 0th-order average Hamiltonian is the same for the three expansion schemes with the three cases examined, there is a case that the 2nd-order term for the Magnus/Floquet expansion is different from that obtained with the Fer expansion. The difference arises due to the separation of the 0th-order term in the Fer expansion. The separation enables us to appreciate time-evolution under the 0th-order average Hamiltonian, however, for that purpose, we use a so-called left-running Fer expansion. Comparison between the left-running Fer expansion and the Magnus expansion indicates that the sign of the odd orders in Magnus may better be reversed if one would like to consider its effect in order.

  18. Comparison among Magnus/Floquet/Fer expansion schemes in solid-state NMR.

    PubMed

    Takegoshi, K; Miyazawa, Norihiro; Sharma, Kshama; Madhu, P K

    2015-04-07

    We here revisit expansion schemes used in nuclear magnetic resonance (NMR) for the calculation of effective Hamiltonians and propagators, namely, Magnus, Floquet, and Fer expansions. While all the expansion schemes are powerful methods there are subtle differences among them. To understand the differences, we performed explicit calculation for heteronuclear dipolar decoupling, cross-polarization, and rotary-resonance experiments in solid-state NMR. As the propagator from the Fer expansion takes the form of a product of sub-propagators, it enables us to appreciate effects of time-evolution under Hamiltonians with different orders separately. While 0th-order average Hamiltonian is the same for the three expansion schemes with the three cases examined, there is a case that the 2nd-order term for the Magnus/Floquet expansion is different from that obtained with the Fer expansion. The difference arises due to the separation of the 0th-order term in the Fer expansion. The separation enables us to appreciate time-evolution under the 0th-order average Hamiltonian, however, for that purpose, we use a so-called left-running Fer expansion. Comparison between the left-running Fer expansion and the Magnus expansion indicates that the sign of the odd orders in Magnus may better be reversed if one would like to consider its effect in order.

  19. Solid-state NMR reveals differential carbohydrate utilization in diapausing Culex pipiens

    NASA Astrophysics Data System (ADS)

    Chang, James; Singh, Jugeshwar; Kim, Sungshil; Hockaday, William C.; Sim, Cheolho; Kim, Sung Joon

    2016-11-01

    Culex pipiens is the mosquito that vectors West Nile Virus and other human-pathogenic flavivruses in North America. In response to shortened day length and lower temperatures, female Cx. pipiense prepares for the diapause by actively feeding on carbohydrates to increase the biosynthesis of glycogen and lipid to store energy for overwintering. The effect of feeding different carbohydrates on glycogen and lipid biosynthesis in diapausing mosquitoes was investigated in vivo using 13C solid-state NMR. Diapause-destined adult females and nondiapausing counterparts after adult eclosion were fed with three different carbohydrate sources for 7 days: 1) 10% sucrose, 2) 10% D-[13C6]glucose, and 3) 1% D-[13C6]glucose co-provisioned with 10% sucrose. NMR measurements show that sucrose and glucose are metabolized differently in diapausing mosquitoes. Mosquitoes fed on sucrose primarily accumulate glycogen with increased branching structures, but less of lipids. In contrast, mosquitoes fed exclusively on glucose show accumulation of both glycogen and lipid with increased aliphatic chain length. Glucose is exclusively metabolized for the biosynthesis of triacylglyceride when mosquitoes were co-fed with sucrose. Our findings provide novel insights into the insect carbohydrate metabolism that governs glycogen and lipid biosynthesis during diapause, which is fundamental for the insect survival during inimical environments.

  20. Dynamic membrane interactions of antibacterial and antifungal biomolecules, and amyloid peptides, revealed by solid-state NMR spectroscopy.

    PubMed

    Naito, Akira; Matsumori, Nobuaki; Ramamoorthy, Ayyalusamy

    2017-06-06

    A variety of biomolecules acting on the cell membrane folds into a biologically active structure in the membrane environment. It is, therefore, important to determine the structures and dynamics of such biomolecules in a membrane environment. While several biophysical techniques are used to obtain low-resolution information, solid-state NMR spectroscopy is one of the most powerful means for determining the structure and dynamics of membrane bound biomolecules such as antibacterial biomolecules and amyloidogenic proteins; unlike X-ray crystallography and solution NMR spectroscopy, applications of solid-state NMR spectroscopy are not limited by non-crystalline, non-soluble nature or molecular size of membrane-associated biomolecules. This review article focuses on the applications of solid-state NMR techniques to study a few selected antibacterial and amyloid peptides. Solid-state NMR studies revealing the membrane inserted bent α-helical structure associated with the hemolytic activity of bee venom melittin and the chemical shift oscillation analysis used to determine the transmembrane structure (with α-helix and 310-helix in the N- and C-termini, respectively) of antibiotic peptide alamethicin are discussed in detail. Oligomerization of an amyloidogenic islet amyloid polypeptide (IAPP, or also known as amylin) resulting from its aggregation in a membrane environment, molecular interactions of the antifungal natural product amphotericin B with ergosterol in lipid bilayers, and the mechanism of lipid raft formation by sphingomyelin studied using solid state NMR methods are also discussed in this review article. This article is part of a Special Issue entitled "Biophysical Exploration of Dynamical Ordering of Biomolecular Systems" edited by Dr. Koichi Kato. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Solid-state NMR Study of Ion Adsorption and Charge Storage in Graphene Film Supercapacitor Electrodes

    NASA Astrophysics Data System (ADS)

    Li, Kecheng; Bo, Zheng; Yan, Jianhua; Cen, Kefa

    2016-12-01

    Graphene film has been demonstrated as promising active materials for electric double layer capacitors (EDLCs), mainly due to its excellent mechanical flexibility and freestanding morphology. In this work, the distribution and variation pattern of electrolyte ions in graphene-film based EDLC electrodes are investigated with a 11B magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. For neutral graphene films soaked with different amounts of electrolytes (1 M TEABF4/ACN), weakly and strongly adsorbed anions are identified based on the resonances at different 11B chemical shifts. Unlike other porous carbonaceous materials, the strongly adsorbed anions are found as the major electrolyte anions components in graphene films. Further measurements on the ion population upon charging are carried out with applying different charging voltages on the graphene films. Results indicate that the charging process of graphene-film based EDLCs can be divided into two distinct charge storage stages (i.e., ejection of co-ions and adsorption of counter-ions) for different voltages. The as-obtained results will be useful for the design and fabrication of high performance graphene-film based EDLCs.

  2. Solid-state NMR Study of Ion Adsorption and Charge Storage in Graphene Film Supercapacitor Electrodes.

    PubMed

    Li, Kecheng; Bo, Zheng; Yan, Jianhua; Cen, Kefa

    2016-12-21

    Graphene film has been demonstrated as promising active materials for electric double layer capacitors (EDLCs), mainly due to its excellent mechanical flexibility and freestanding morphology. In this work, the distribution and variation pattern of electrolyte ions in graphene-film based EDLC electrodes are investigated with a (11)B magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. For neutral graphene films soaked with different amounts of electrolytes (1 M TEABF4/ACN), weakly and strongly adsorbed anions are identified based on the resonances at different (11)B chemical shifts. Unlike other porous carbonaceous materials, the strongly adsorbed anions are found as the major electrolyte anions components in graphene films. Further measurements on the ion population upon charging are carried out with applying different charging voltages on the graphene films. Results indicate that the charging process of graphene-film based EDLCs can be divided into two distinct charge storage stages (i.e., ejection of co-ions and adsorption of counter-ions) for different voltages. The as-obtained results will be useful for the design and fabrication of high performance graphene-film based EDLCs.

  3. Solid-state NMR Study of Ion Adsorption and Charge Storage in Graphene Film Supercapacitor Electrodes

    PubMed Central

    Li, Kecheng; Bo, Zheng; Yan, Jianhua; Cen, Kefa

    2016-01-01

    Graphene film has been demonstrated as promising active materials for electric double layer capacitors (EDLCs), mainly due to its excellent mechanical flexibility and freestanding morphology. In this work, the distribution and variation pattern of electrolyte ions in graphene-film based EDLC electrodes are investigated with a 11B magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. For neutral graphene films soaked with different amounts of electrolytes (1 M TEABF4/ACN), weakly and strongly adsorbed anions are identified based on the resonances at different 11B chemical shifts. Unlike other porous carbonaceous materials, the strongly adsorbed anions are found as the major electrolyte anions components in graphene films. Further measurements on the ion population upon charging are carried out with applying different charging voltages on the graphene films. Results indicate that the charging process of graphene-film based EDLCs can be divided into two distinct charge storage stages (i.e., ejection of co-ions and adsorption of counter-ions) for different voltages. The as-obtained results will be useful for the design and fabrication of high performance graphene-film based EDLCs. PMID:28000786

  4. A stable amorphous statin: solid-state NMR and dielectric studies on dynamic heterogeneity of simvastatin.

    PubMed

    Nunes, Teresa G; Viciosa, M Teresa; Correia, Natália T; Danède, F; Nunes, Rita G; Diogo, Hermínio P

    2014-03-03

    Statins have been widely used as cholesterol-lowering agents. However, low aqueous solubility of crystalline statins and, consequently, reduced biovailability require seeking for alternative forms and formulations to ensure an accurate therapeutic window. The objective of the present study was to evaluate the stability of amorphous simvastatin by probing molecular dynamics using two nondestructive techniques: solid-state NMR and dielectric relaxation spectroscopy. Glassy simvastatin was obtained by the melt quench technique. (13)C cross-polarization/magic-angle-spinning (CP/MAS) NMR spectra and (1)H MAS NMR spectra were obtained from 293 K up to 333 K (Tg ≈ 302 K). The (13)C spin-lattice relaxation times in the rotating frame, T1ρ, were measured as a function of temperature, and the correlation time and activation energy data obtained for local motions in different frequency scales revealed strong dynamic heterogeneity, which appears to be essential for the stability of the amorphous form of simvastatin. In addition, the (1)H MAS measurements presented evidence for mobility of the hydrogen atoms in hydroxyl groups which was assigned to noncooperative secondary relaxations. The complex dielectric permittivity of simvastatin was monitored in isochronal mode at five frequencies (from 0.1 to 1000 kHz), by carrying out a heating/cooling cycle allowing to obtain simvastatin in the supercooled and glassy states. The results showed that no dipolar moment was lost due to immobilization, thus confirming that no crystallization had taken place. Complementarily, the present study focused on the thermal stability of simvastatin using thermogravimetric analysis while the thermal events were followed up by differential scanning calorimetry and dielectric relaxation spectroscopy. Overall, the results confirm that the simvastatin in the glass form reveals a potential use in the solid phase formulation on the pharmaceutical industry.

  5. Solid-state NMR studies of the dynamics and structure of mouse keratin intermediate filaments

    SciTech Connect

    Mack, J.W.; Torchia, D.A.; Steinert, P.M.

    1988-07-26

    The molecular dynamics and structural organization of mouse epidermal keratin intermediate filaments (IF) have been studied via solid-state nuclear magnetic resonance (NMR) experiments performed on IF labeled both in vivo and in vitro with isotopically enriched amino acids. As a probe of the organization of the peripheral glycine-rich end domains of the IF, carbon-13 NMR experiments have been performed on subfilamentous forms (prekeratin) and on IF reassembled in vitro that had been labeled with either (1-/sup 13/C)glycine or (2-/sup 13/C)glycine, as more than 90% of the glycines of the keratins are located in the end domains. Measurements of carbon relaxation times, nuclear Overhauser enhancements, and signal intensities show that the motions of the peptide backbone in the end domains are effectively isotropic. These results indicate that the end domains of IF are remarkably flexible and have little or no structural order. To probe the structural organization of the coiled-coil rod domains of the IF, separate samples of native keratin IF, raised in primary tissue culture, were labeled with L-(1-/sup 13/C)leucine, L-(/sup 2/H/sub 10/)leucine, or L-(2,3,3-/sup 2/H/sub 3/)leucine, as greater than 90% of the leucyl residues of the keratin IF types studied are located in the coiled coils which form the central core of IF. Deuterium NMR experiments performed on IF labeled with deuteriated leucines indeed reveal a marked degree of peptide backbone rigidity within the coiled coils, confirming the initial conclusions of the carbon-13 data. These data, demonstrating relative peptide backbone rigidity yet side-chain flexibility, are interpreted to mean that the coiled coils of these keratin IF are not tightly packed together but rather form a somewhat looser structure which permits a significant degree of side-chain mobility.

  6. β-Sheet core of tau paired helical filaments revealed by solid-state NMR.

    PubMed

    Daebel, Venita; Chinnathambi, Subashchandrabose; Biernat, Jacek; Schwalbe, Martin; Habenstein, Birgit; Loquet, Antoine; Akoury, Elias; Tepper, Katharina; Müller, Henrik; Baldus, Marc; Griesinger, Christian; Zweckstetter, Markus; Mandelkow, Eckhard; Vijayan, Vinesh; Lange, Adam

    2012-08-29

    One of the hallmarks of Alzheimer's disease is the self-assembly of the microtubule-associated protein tau into fibers termed "paired helical filaments" (PHFs). However, the structural basis of PHF assembly at atomic detail is largely unknown. Here, we applied solid-state nuclear magnetic resonance (ssNMR) spectroscopy to investigate in vitro assembled PHFs from a truncated three-repeat tau isoform (K19) that represents the core of PHFs. We found that the rigid core of the fibrils is formed by amino acids V306 to S324, only 18 out of 99 residues, and comprises three β-strands connected by two short kinks. The first β-strand is formed by the well-studied hexapeptide motif VQIVYK that is known to self-aggregate in a steric zipper arrangement. Results on mixed [(15)N:(13)C]-labeled K19 fibrils show that β-strands are stacked in a parallel, in-register manner. Disulfide bridges formed between C322 residues of different molecules lead to a disturbance of the β-sheet structure, and polymorphism in ssNMR spectra is observed. In particular, residues K321-S324 exhibit two sets of resonances. Experiments on K19 C322A PHFs further confirm the influence of disulfide bond formation on the core structure. Our structural data are supported by H/D exchange NMR measurements on K19 as well as a truncated four-repeat isoform of tau (K18). Site-directed mutagenesis studies show that single-point mutations within the three different β-strands result in a significant loss of PHF aggregation efficiency, highlighting the importance of the β-structure-rich regions for tau aggregation.

  7. Sensitivity-enhanced solid-state NMR detection of expansin's target in plant cell walls

    SciTech Connect

    Wang, Tuo; Park, Yong Bum; Caporini, Marc A.; Rosay, Melanie; Zhong, Linghao; Cosgrove, Daniel J.; Hong, Mei

    2013-08-29

    Structure determination of protein binding to noncrystalline macromolecular assemblies such as plant cell walls (CWs) poses a significant structural biology challenge. CWs are loosened during growth by expansin proteins, which weaken the noncovalent network formed by cellulose, hemicellulose, and pectins, but the CW target of expansins has remained elusive because of the minute amount of the protein required for activity and the complex nature of the CW. Using solid-state NMR spectroscopy, combined with sensitivity-enhancing dynamic nuclear polarization (DNP) and differential isotopic labeling of expansin and polysaccharides, we have now determined the functional binding target of expansin in the Arabidopsis thaliana CW. By transferring the electron polarization of a biradical dopant to the nuclei, DNP allowed selective detection of 13C spin diffusion from trace concentrations of 13C, 15N-labeled expansin in the CW to nearby polysaccharides. From the spin diffusion data of wild-type and mutant expansins, we conclude that to loosen the CW, expansin binds highly specific cellulose domains enriched in xyloglucan, whereas more abundant binding to pectins is unrelated to activity. Molecular dynamics simulations indicate short 13C-13C distances of 4–6 Å between a hydrophobic surface of the cellulose microfibril and an aromatic motif on the expansin surface, consistent with the observed NMR signals. DNP-enhanced 2D 13C correlation spectra further reveal that the expansin-bound cellulose has altered conformation and is enriched in xyloglucan, thus providing unique insight into the mechanism of CW loosening. DNP-enhanced NMR provides a powerful, generalizable approach for investigating protein binding to complex macromolecular targets.

  8. Low-power broadband solid-state MAS NMR of 14N

    NASA Astrophysics Data System (ADS)

    Pell, Andrew J.; Sanders, Kevin J.; Wegner, Sebastian; Pintacuda, Guido; Grey, Clare P.

    2017-05-01

    We propose two broadband pulse schemes for 14N solid-state magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) that achieves (i) complete population inversion and (ii) efficient excitation of the double-quantum spectrum using low-power single-sideband-selective pulses. We give a comprehensive theoretical description of both schemes using a common framework that is based on the jolting-frame formalism of Caravatti et al. [J. Magn. Reson. 55, 88 (1983)]. This formalism is used to determine for the first time that we can obtain complete population inversion of 14N under low-power conditions, which we do here using single-sideband-selective adiabatic pulses. It is then used to predict that double-quantum coherences can be excited using low-power single-sideband-selective pulses. We then proceed to design a new experimental scheme for double-quantum excitation. The final double-quantum excitation pulse scheme is easily incorporated into other NMR experiments, as demonstrated here for double quantum-single quantum 14N correlation spectroscopy, and 1H-14N dipolar heteronuclear multiple-quantum correlation experiments. These pulses and irradiation schemes are evaluated numerically using simulations on single crystals and full powders, as well as experimentally on ammonium oxalate ((NH4)2C2O4) at moderate MAS and glycine at ultra-fast MAS. The performance of these new NMR methods is found to be very high, with population inversion efficiencies of 100% and double-quantum excitation efficiencies of 30%-50%, which are hitherto unprecedented for the low radiofrequency field amplitudes, up to the spinning frequency, that are used here.

  9. 31P Solid State NMR Studies of ZrP, Mg3P2, and CdPS3

    DTIC Science & Technology

    1988-01-01

    valence , in contrast to that in ZrP, Mg3P2, and MgP4. The 3 1 p solid state NMR spectra are shown in Figure 9. The MAS spectrum reveals a single...orange crystals were recovered from hot concentrated HCa . In one experi- RESULTS AND DISCUSSION ment, brilliant black polyhedral crystals of ZnSnP, were

  10. The role of solid state 13 C NMR spectroscopy in studies of the nature of native celluloses

    Treesearch

    R.H. Atalla; D.L. VanderHart

    1999-01-01

    Published spectroscopic observations pertaining to the crystal structure of native celluloses are reviewed for the purpose of defining our current level of understanding about crystalline polymorphism in these materials. Emphasis is placed on observations from solid state 13 C nuclear magnetic resonance (NMR), which first led to the postulate that most native,...

  11. Application of solid state NMR for the study of surface bound species and fossil fuels

    NASA Astrophysics Data System (ADS)

    Althaus, Stacey

    Recent advances in solid state NMR have been utilized to study a variety of systems. These advancements have allowed for the acquisition of sequences previously only available for solution state detection. The protocol for the measurement of coals and other carbonaceous materials was updated to incorporate the recent advancements in fast magic angle spinning (MAS) and high magnetic fields. Argonne Premium Coals were used to test the sensitivity and resolution of the experiments preformed at high field and fast MAS. The higher field spectra were shown to be slightly less sensitive than the traditional lower field spectra, however, the new high field fast MAS spectra had better resolution. This increased resolution allowed for the separation of a variety of different functional groups, thereby allowing the composition of the coal to be determined. The use of 1 H detection allowed for 2D spectra of coals for the first time. These spectra could be filtered to examine either through-space or through-bond correlations. Indirect detection via 1 H was also pivotal in the detection of natural abundance 15 N spectra. Through-space and through-bond 2D spectra of natural abundance bulk species are shown with a sensitivity increase of 15 fold over traditional detection. This sensitivity enhancement allowed for the detection of natural abundance 15 N surface bound species in 2D, something that could not be acquired via traditional methods. The increased efficiency of the through-space magnetization transfer, Cross polarization, at fast MAS compared to the slower MAS rates is shown. The through-bond magnetization transfer via INEPT was examined and the effect of J-coupling is confirmed. Solid State NMR can be utilized to help improve catalytic interactions. Solid state NMR was used to examine the aldol condensation between p-nitrobenzaldehyde and acetone. The formation of a stable intermediate with p-nitrobenzaldehyde was found on the primary functionalized amine mesoporous

  12. Investigation of Local Structures in Layered Niobates by Solid-state NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Ting

    Research on ion-exchangeable layered niobates has attracted great attention due to their unique structures and corresponding variations in properties and applications, such as ion conductors, solid acids, and water splitting catalysts. Families of layered niobates include double-layered or triple-layered Dion-Jacobson type perovskites (ALaNb2O7, A = Cs, Rb, K, H; AM2Nb3O10, A = Rb, K, H; M = Sr, Ca), layered niobates with both edge and corner sharing of NbO6 octahedra (KNb3O8, HNb3O6, Nb 6O17 and H4Nb6O17) and many others. Lately, more developments in the layered niobates through a variety of topochemical manipulations have been achieved. The topochemical reactions include ion exchange, exfoliation, substitution, and etc. As a result, many new materials have been successfully prepared, for example, solid solutions (ALa2NbTi2O10, ACaLaNb2TiO 10 and ACa2Nb3-xTaxO10, etc.), nanosheets (HNb3O8, H4Nb6O17, HLaNb2O7, HCa2Nb3O10, etc., to intercalate with organic molecules such as tetrabutylammonium hydroxide or n-butylamines), and nanoscrolls (from H2K2Nb 6O17). While these structural modifications often induce improvements in properties, the fundamental mechanisms of improvements in properties upon the modifications, especially local structural arrangements are poorly understood, which is often limited by structural characterizations. Particularly, the characterizations of the exfoliated nanosheets can be difficult by conventional X-ray diffraction (XRD) method due to disordered structures. Alternatively, solid-state nuclear magnetic resonance (NMR) spectroscopy is a useful tool to study local structures in solids. The structural information can be extracted by examining intrinsic interactions, such as quadrupolar, chemical shielding, and dipolar interactions, which are all associated with local environments surrounding a specific nucleus, 1H or 93Nb in layered niobates. The ultimate goal of this dissertation is to understand the relationships between local structures of

  13. Effect of pressure on the intermediate-valence semiconductor SmB6: 11B-NMR

    NASA Astrophysics Data System (ADS)

    Nishiyama, Kohei; Mito, Takeshi; Ueda, Ko-ichi; Koyama, Takehide; Kohara, Takao; Pristáš, Gabriel; Gabáni, Slavomír; Reiffers, Marián; Flachbart, Karol; Komaki, Yasuhiro; Kokubu, Mitsutane; Fukazawa, Hideto; Kohori, Yoh; Takeshita, Nao; Shitsevalova, Natalia

    2013-06-01

    We report the first high-pressure 11B-NMR studies above 3 GPa on the intermediate-valence semiconductor SmB6. A 11B-NMR line obtained at 4.9 GPa, the highest pressure for the measurements, and at 1.9 K shows quite similar a line shape to that at ambient pressure, indicating no structural or magnetic phase transition up to this pressure. The temperature dependence of the spin lattice relaxation rate 1/ T 1 at 4.9 GPa still exhibits an activation-type temperature dependence characteristic of semiconductors, which reveals an obvious decrease in the insulating gap by about 30% compared to the gap at ambient pressure. The present experimental facts of a finite insulator gap and no magnetic order at 4.9 GPa are consistent with recent transport measurements performed under better hydrostatic pressures.

  14. Uniaxial plastic deformation of isotactic polypropylene studied by solid-state NMR

    NASA Astrophysics Data System (ADS)

    Kang, Jia

    At alleviated temperatures, some semicrystralline polymers can be stretched to very large deformation ratios. Such deformations of semicrystalline polymers have been extensively studied since 1960s. Based on experimental observations and theoretical investigations, solid-state transformation (three stage model) proposed in 1971 and local melting and recrystallization in 1978 have been considered two major mechanisms to explain the deformations of polymer crystals. With the elucidation of molecular dynamics in the last two decades, it was proposed in 1999 that helical jump motion plays an important role in crystal deformation. On the other hand, the new structures induced by deformation also influence the molecular motions and resultant properties of deformed polymers. Such processing-structure-property relationship is very important to understand the polymer behaviors as well as to inform the polymer industry. In this dissertation, using the advanced tool of solid-state NMR (ss-NMR), we achieve three goals: Firstly, we investigate the hierarchical crystalline structural changes of isotactic polypropylene (i PP) upon high temperature stretching to understand the deformation process. Secondly, we evaluate the roles of local packing structure and crystal thickness in determining the stem motions and thermal properties of deformed alpha-form iPP. Thirdly, we utilize 13C-labeled isotactic polypropylene (iPP) to trace the change of chain folding number as a function of e to conclude molecular-level deformation mechanism. To realize the first and second goals, the chain packing, crystal thickness, molecular dynamics, and melting temperature (Tm) of a-form iPP drawn uniaxially at high temperatures of 100 - 150 °C were investigated using solid-state (SS) NMR and DSC. Two types of iPP samples with disordered (alpha1) and relatively ordered (alpha2-rich) packing structures were prepared via different thermal treatments and drawn up to an engineering strain ( e) of

  15. Molecular ordering and molecular dynamics in isotactic-polypropylene characterized by solid state NMR.

    PubMed

    Miyoshi, Toshikazu; Mamun, Al; Hu, Wei

    2010-01-14

    The order-disorder phenomenon of local packing structures, space heterogeneity, and molecular dynamics and average lamellar thickness, , of the alpha form of isotactic polypropylene (iPP) crystallized at various supercooling temperatures, DeltaT, are investigated by solid-state (SS) NMR and SAXS, respectively. increases with lowering DeltaT, and extrapolations of (-1) versus averaged melting point, , gives an equilibrium melting temperature, T(m)(0) = 457 +/- 4 K. High-power TPPM decoupling with a field strength of 110 kHz extremely improves (13)C high-resolution SS-NMR spectral resolution of the ordered crystalline signals at various DeltaT. A high-resolution (13)C SS-NMR spectrum combined with a conventional spin-lattice relaxation time in the rotating frame (T(1rhoH)) filter easily accesses an order-disorder phenomenon for upward and downward orientations of stems and their packing in the crystalline region. It is found that ordered packing fraction, f(order), increases with lowering DeltaT and reaches a maximum value of 62% at DeltaT = 34 K. The ordering phenomenon of stem packing indicates that chain-folding direction changes from random in the disordered packing to order in the ordered packing along the a sin theta axis under a hypothesis of adjacent re-entry structures. It is also found that f(order) significantly increases prior to enhancement of lamellar thickness. Additionally, annealing experiments indicate that is significantly enhanced after a simultaneous process of partial melting and recrystallization/reorganization into the ordered packing at annealing temperature >/=423 K. Furthermore, the center-bands only detection of exchange (CODEX) NMR method demonstrates that time-kinetic parameters of helical jump motions are highly influenced by DeltaT. These dynamic constraints are interpreted in terms of increment of and packing ordering. Through these new results related to molecular structures and dynamics, roles of polymer

  16. Structural Changes Associated with Transthyretin Misfolding and Amyloid Formation Revealed by Solution and Solid-State NMR

    SciTech Connect

    Lim, Kwang Hun; Dasari, Anvesh K. R.; Hung, Ivan; Gan, Zhehong; Kelly, Jeffery W.; Wemmer, David E.

    2016-03-21

    Elucidation of structural changes involved in protein misfolding and amyloid formation is crucial for unraveling the molecular basis of amyloid formation. We report structural analyses of the amyloidogenic intermediate and amyloid aggregates of transthyretin using solution and solid-state nuclear magnetic resonance (NMR) spectroscopy. These NMR solution results show that one of the two main β-sheet structures (CBEF β-sheet) is maintained in the aggregation-competent intermediate, while the other DAGH β-sheet is more flexible on millisecond time scales. Magic-angle-spinning solid-state NMR revealed that AB loop regions interacting with strand A in the DAGH β-sheet undergo conformational changes, leading to the destabilized DAGH β-sheet.

  17. Structural Changes Associated with Transthyretin Misfolding and Amyloid Formation Revealed by Solution and Solid-State NMR

    DOE PAGES

    Lim, Kwang Hun; Dasari, Anvesh K. R.; Hung, Ivan; ...

    2016-03-21

    Elucidation of structural changes involved in protein misfolding and amyloid formation is crucial for unraveling the molecular basis of amyloid formation. We report structural analyses of the amyloidogenic intermediate and amyloid aggregates of transthyretin using solution and solid-state nuclear magnetic resonance (NMR) spectroscopy. These NMR solution results show that one of the two main β-sheet structures (CBEF β-sheet) is maintained in the aggregation-competent intermediate, while the other DAGH β-sheet is more flexible on millisecond time scales. Magic-angle-spinning solid-state NMR revealed that AB loop regions interacting with strand A in the DAGH β-sheet undergo conformational changes, leading to the destabilized DAGHmore » β-sheet.« less

  18. High-Resolution Solid-State NMR Characterization of Ligand Binding to a Protein Immobilized in a Silica Matrix.

    PubMed

    Cerofolini, Linda; Giuntini, Stefano; Louka, Alexandra; Ravera, Enrico; Fragai, Marco; Luchinat, Claudio

    2017-08-31

    Solid-state NMR is becoming a powerful tool to detect atomic-level structural features of biomolecules even when they are bound to (or trapped in) solid systems that lack long-range three-dimensional order. We here demonstrate that it is possible to probe protein-ligand interactions from a protein-based perspective also when the protein is entrapped in silica, thus translating into biomolecular solid-state NMR all of the considerations that are usually made to understand the chemical nature of the interaction of a protein with its ligands. This work provides a proof of concept that also immobilized enzymes can be used for protein-based NMR protein-ligand interactions for drug discovery.

  19. Testing the limits of sensitivity in a solid-state structural investigation by combined X-ray powder diffraction, solid-state NMR, and molecular modelling.

    PubMed

    Filip, Xenia; Borodi, Gheorghe; Filip, Claudiu

    2011-10-28

    A solid state structural investigation of ethoxzolamide is performed on microcrystalline powder by using a multi-technique approach that combines X-ray powder diffraction (XRPD) data analysis based on direct space methods with information from (13)C((15)N) solid-state Nuclear Magnetic Resonance (SS-NMR) and molecular modeling. Quantum chemical computations of the crystal were employed for geometry optimization and chemical shift calculations based on the Gauge Including Projector Augmented-Wave (GIPAW) method, whereas a systematic search in the conformational space was performed on the isolated molecule using a molecular mechanics (MM) approach. The applied methodology proved useful for: (i) removing ambiguities in the XRPD crystal structure determination process and further refining the derived structure solutions, and (ii) getting important insights into the relationship between the complex network of non-covalent interactions and the induced supra-molecular architectures/crystal packing patterns. It was found that ethoxzolamide provides an ideal case study for testing the accuracy with which this methodology allows to distinguish between various structural features emerging from the analysis of the powder diffraction data.

  20. 35Cl dynamic nuclear polarization solid-state NMR of active pharmaceutical ingredients

    SciTech Connect

    Hirsh, David A.; Rossini, Aaron J.; Emsley, Lyndon; Schurko, Robert W.

    2016-08-24

    In this paper, we show how to obtain efficient dynamic nuclear polarization (DNP) enhanced 35Cl solid-state NMR (SSNMR) spectra at 9.4 T and demonstrate how they can be used to characterize the molecular-level structure of hydrochloride salts of active pharmaceutical ingredients (APIs) in both bulk and low wt% API dosage forms. 35Cl SSNMR central-transition powder patterns of chloride ions are typically tens to hundreds of kHz in breadth, and most cannot be excited uniformly with high-power rectangular pulses or acquired under conditions of magic-angle spinning (MAS). Herein, we demonstrate the combination of DNP and 1H–35Cl broadband adiabatic inversion cross polarization (BRAIN-CP) experiments for the acquisition of high quality wideline spectra of APIs under static sample conditions, and obtain signals up to 50 times greater than in spectra acquired without the use of DNP at 100 K. We report a new protocol, called spinning-on spinning-off (SOSO) acquisition, where MAS is applied during part of the polarization delay to increase the DNP enhancements and then the MAS rotation is stopped so that a wideline 35Cl NMR powder pattern free from the effects of spinning sidebands can be acquired under static conditions. This method provides an additional two-fold signal enhancement compared to DNP-enhanced SSNMR spectra acquired under purely static conditions. DNP-enhanced 35Cl experiments are used to characterize APIs in bulk and dosage forms with Cl contents as low as 0.45 wt%. These results are compared to DNP-enhanced 1H–13C CP/MAS spectra of APIs in dosage forms, which are often hindered by interfering signals arising from the binders, fillers and other excipient materials.

  1. 35Cl dynamic nuclear polarization solid-state NMR of active pharmaceutical ingredients

    DOE PAGES

    Hirsh, David A.; Rossini, Aaron J.; Emsley, Lyndon; ...

    2016-08-24

    In this paper, we show how to obtain efficient dynamic nuclear polarization (DNP) enhanced 35Cl solid-state NMR (SSNMR) spectra at 9.4 T and demonstrate how they can be used to characterize the molecular-level structure of hydrochloride salts of active pharmaceutical ingredients (APIs) in both bulk and low wt% API dosage forms. 35Cl SSNMR central-transition powder patterns of chloride ions are typically tens to hundreds of kHz in breadth, and most cannot be excited uniformly with high-power rectangular pulses or acquired under conditions of magic-angle spinning (MAS). Herein, we demonstrate the combination of DNP and 1H–35Cl broadband adiabatic inversion cross polarizationmore » (BRAIN-CP) experiments for the acquisition of high quality wideline spectra of APIs under static sample conditions, and obtain signals up to 50 times greater than in spectra acquired without the use of DNP at 100 K. We report a new protocol, called spinning-on spinning-off (SOSO) acquisition, where MAS is applied during part of the polarization delay to increase the DNP enhancements and then the MAS rotation is stopped so that a wideline 35Cl NMR powder pattern free from the effects of spinning sidebands can be acquired under static conditions. This method provides an additional two-fold signal enhancement compared to DNP-enhanced SSNMR spectra acquired under purely static conditions. DNP-enhanced 35Cl experiments are used to characterize APIs in bulk and dosage forms with Cl contents as low as 0.45 wt%. These results are compared to DNP-enhanced 1H–13C CP/MAS spectra of APIs in dosage forms, which are often hindered by interfering signals arising from the binders, fillers and other excipient materials.« less

  2. 15N solid-state NMR provides a sensitive probe of oxidized flavin reactive sites.

    PubMed

    Koder, Ronald L; Walsh, Joseph D; Pometun, Maxim S; Dutton, P Leslie; Wittebort, Richard J; Miller, Anne-Frances

    2006-11-29

    Flavins are central to the reactivity of a wide variety of enzymes and electron transport proteins. There is great interest in understanding the basis for the different reactivities displayed by flavins in different protein contexts. We propose solid-state nuclear magnetic resonance (SS-NMR) as a tool for directly observing reactive positions of the flavin ring and thereby obtaining information on their frontier orbitals. We now report the SS-NMR signals of the redox-active nitrogens N1 and N5, as well as that of N3. The chemical shift tensor of N5 is over 720 ppm wide, in accordance with the predictions of theory and our calculations. The signal of N3 can be distinguished on the basis of coupling to 1H absent for N1 and N5, as well as the shift tensor span of only 170 ppm, consistent with N3's lower aromaticity and lack of a nonbonding lone pair. The isotropic shifts and spans of N5 and N1 reflect two opposite extremes of the chemical shift range for "pyridine-type" N's, consistent with their electrophilic and nucleophilic chemical reactivities, respectively. Upon flavin reduction, N5's chemical shift tensor contracts dramatically to a span of less than 110 ppm, and the isotropic chemical shift changes by approximately 300 ppm. Both are consistent with loss of N5's nonbonding lone pair and decreased aromaticity, and illustrate the responsiveness of the 15N chemical shift principal values to electronic structure. Thus. 15N chemical shift principal values promise to be valuable tools for understanding electronic differences that underlie variations in flavin reactivity, as well as the reactivities of other heterocyclic cofactors.

  3. High-Resolution NMR of Quadrupolar Nuclei in the Solid State

    SciTech Connect

    Gann, Sheryl Lee

    1995-11-01

    This dissertation describes recent developments in solid state nuclear magnetic resonance (NMR), for the most part involving the use of dynamic-angle spinning (DAS) NMR to study quadrupolar nuclei. Chapter 1 introduces some of the basic concepts and theory that will be referred to in later chapters, such as the density operator, product operators, rotations, coherence transfer pathways, phase cycling, and the various nuclear spin interactions, including the quadrupolar interaction. Chapter 2 describes the theory behind motional averaging experiments, including DAS, which is a technique where a sample is spun sequentially about two axis oriented at different angles with respect to the external magnetic field such that the chemical shift and quadrupolar anisotropy are averaged to zero. Work done on various rubidium-87 salts is presented as a demonstration of DAS. Chapter 3 explains how to remove sidebands from DAS and magic-angle spinning (MAS) experiments, which result from the time-dependence of the Hamiltonian under sample spinning conditions, using rotor-synchronized π-pulses. Data from these experiments, known as DAH-180 and MAH-180, respectively, are presented for both rubidium and lead salts. In addition, the applicability of this technique to double rotation (DOR) experiments is discussed. Chapter 4 concerns the addition of cross-polarization to DAS (CPDAS). The theory behind spin locking and cross polarizing quadrupolar nuclei is explained and a method of avoiding the resulting problems by performing cross polarization at 0° $\\parallel$ with respect to the magnetic field is presented. Experimental results are shown for a sodium-23 compound, sodium pyruvate, and for oxygen-17 labeled L-akmine. In Chapter 5, a method for broadening the Hartmann-Hahn matching condition under MAS, called variable effective field cross-polarization (VEFCP), is presented, along with experimental work on adamantane and polycarbonate.

  4. A solid-state NMR study of phospholipid-cholesterol interactions: sphingomyelin-cholesterol binary systems.

    PubMed

    Guo, Wen; Kurze, Volker; Huber, Thomas; Afdhal, Nezam H; Beyer, Klaus; Hamilton, James A

    2002-09-01

    We used solid-state NMR techniques to probe the interactions of cholesterol (Chol) with bovine brain sphingomyelin (SM) and for comparison of the interactions of Chol with dipalmitoylphosphatidylcholine (DPPC), which has a similar gel-to-liquid crystalline transition temperature. (1)H-, (31)P-, and (13)C-MASNMR yielded high-resolution spectra from multilamellar dispersions of unlabeled brain SM and Chol for analysis of chemical shifts and linewidths. In addition, (2)H-NMR spectra of oriented lipid membranes with specific deuterium labels gave information about membrane ordering and mobility. Chol disrupted the gel-phase of pure SM and increased acyl chain ordering in the liquid crystalline phase. As inferred from (13)C chemical shifts, the boundaries between the ordered and disordered liquid crystalline phases (L and L) were similar for SM and DPPC. The solubility limit of Chol in SM was ~50 mol %, the same value as previously reported for DPPC membranes. We found no evidence for specific H-bonding between Chol and the amide group of SM. The order parameters of a probe molecule, d31-sn1-DPPC, in SM were slightly higher than in DPPC for all carbons except the terminal groups at 30 mol % but were not significantly different at 5 and 60 mol % Chol. These studies show a general similarity with some subtle differences in the way Chol interacts with DPPC and SM. In the environment of a typical biomembrane, the higher proportion of saturated fatty acyl chains in SM compared to other phospholipids may be the most significant factor influencing interactions with Chol.

  5. Calcination products of gibbsite studied by X-ray diffraction, XPS and solid-state NMR

    SciTech Connect

    Malki, A.; Mekhalif, Z.; Detriche, S.; Fonder, G.; Boumaza, A.; Djelloul, A.

    2014-07-01

    The changes caused by heat treatment of gibbsite powder at 300–1473 K were studied using the X-ray diffraction (XRD), X-ray photoemission (XPS) spectra and {sup 27}Al magic angle spinning nuclear magnetic resonance spectroscopy ({sup 27}Al MAS NMR). XRD analysis indicates that the transformation sequence involves the formation of κ-Al{sub 2}O{sub 3} as an intermediate phase between χ- and α-Al{sub 2}O{sub 3}. The crystallite size of χ-Al{sub 2}O{sub 3} is as small as 10 nm. XPS analysis indicates that the ratio of aluminium atoms to oxygen atoms in χ-Al{sub 2}O{sub 3} and κ-Al{sub 2}O{sub 3} increases, whereas the expected ratio is observed in α-Al{sub 2}O{sub 3}. The percentage of AlO{sub 4} units in the transition aluminas follows the same behaviour as the ratio of Al/O. - Graphical abstract: The percentage of AlO{sub 4} units in transition aluminas follows the same behaviour as the ratio of Al/O. - Highlights: • Calcination products of gibbsite studied by XRD, XPS and solid-state NMR. • The crystallite size of χ-Al{sub 2}O{sub 3} is as small as 10 nm. • The Al/O atomic ratio determined by XPS is larger than 2/3 in χ-Al{sub 2}O{sub 3} and κ-Al{sub 2}O{sub 3}. • The percentage of AlO{sub 4} in the aluminas follows the same behaviour as the Al/O atomic ratio.

  6. Characterization of the Particle Size and Polydispersity of Dicumarol Using Solid-State NMR Spectroscopy.

    PubMed

    Dempah, Kassibla Elodie; Lubach, Joseph W; Munson, Eric J

    2017-03-06

    A variety of particle sizes of a model compound, dicumarol, were prepared and characterized in order to investigate the correlation between particle size and solid-state NMR (SSNMR) proton spin-lattice relaxation ((1)H T1) times. Conventional laser diffraction and scanning electron microscopy were used as particle size measurement techniques and showed crystalline dicumarol samples with sizes ranging from tens of micrometers to a few micrometers. Dicumarol samples were prepared using both bottom-up and top-down particle size control approaches, via antisolvent microprecipitation and cryogrinding. It was observed that smaller particles of dicumarol generally had shorter (1)H T1 times than larger ones. Additionally, cryomilled particles had the shortest (1)H T1 times encountered (8 s). SSNMR (1)H T1 times of all the samples were measured and showed as-received dicumarol to have a T1 of 1500 s, whereas the (1)H T1 times of the precipitated samples ranged from 20 to 80 s, with no apparent change in the physical form of dicumarol. Physical mixtures of different sized particles were also analyzed to determine the effect of sample inhomogeneity on (1)H T1 values. Mixtures of cryoground and as-received dicumarol were clearly inhomogeneous as they did not fit well to a one-component relaxation model, but could be fit much better to a two-component model with both fast-and slow-relaxing regimes. Results indicate that samples of crystalline dicumarol containing two significantly different particle size populations could be deconvoluted solely based on their differences in (1)H T1 times. Relative populations of each particle size regime could also be approximated using two-component fitting models. Using NMR theory on spin diffusion as a reference, and taking into account the presence of crystal defects, a model for the correlation between the particle size of dicumarol and its (1)H T1 time was proposed.

  7. Morphology, 31P Spin Diffusion, and Phase Transitions in a Representative Semicrystalline Polyphosphazene by Solid-State NMR

    DTIC Science & Technology

    1992-01-01

    NMR 12. PERSONAL AUTHOR(S) S. Taylor, J. White, N. Elbaum, R. Crosby, G. Gampbell, J. Haw and G. Hatfield 13a. TYPE OF REPORT 13b. TIMr y§;YPD 5/14 DATE...by block numoer) Solid-state NMR spectroscopy was used to investigate the morphology and molecular dynamics of poly[bis(3-methylphenoxy)phosphazene...PB3MP, a representative semicrystalline polyphospha-zene. Variable temperature 31p magic-angle spinning (MAS) NMR spectra revealed two well resolved

  8. Folding of xylan onto cellulose fibrils in plant cell walls revealed by solid-state NMR

    PubMed Central

    Simmons, Thomas J.; Mortimer, Jenny C.; Bernardinelli, Oigres D.; Pöppler, Ann-Christin; Brown, Steven P.; deAzevedo, Eduardo R.; Dupree, Ray; Dupree, Paul

    2016-01-01

    Exploitation of plant lignocellulosic biomass is hampered by our ignorance of the molecular basis for its properties such as strength and digestibility. Xylan, the most prevalent non-cellulosic polysaccharide, binds to cellulose microfibrils. The nature of this interaction remains unclear, despite its importance. Here we show that the majority of xylan, which forms a threefold helical screw in solution, flattens into a twofold helical screw ribbon to bind intimately to cellulose microfibrils in the cell wall. 13C solid-state magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, supported by in silico predictions of chemical shifts, shows both two- and threefold screw xylan conformations are present in fresh Arabidopsis stems. The twofold screw xylan is spatially close to cellulose, and has similar rigidity to the cellulose microfibrils, but reverts to the threefold screw conformation in the cellulose-deficient irx3 mutant. The discovery that induced polysaccharide conformation underlies cell wall assembly provides new principles to understand biomass properties. PMID:28000667

  9. Nutrient-dependent structural changes in S. aureus peptidoglycan revealed by solid-state NMR spectroscopy.

    PubMed

    Zhou, Xiaoxue; Cegelski, Lynette

    2012-10-16

    The bacterial cell wall is essential to cell survival and is a major target of antibiotics. The main component of the bacterial cell wall is peptidoglycan, a cage-like macromolecule that preserves cellular integrity and maintains cell shape. The insolubility and heterogeneity of peptidoglycan pose a challenge to conventional structural analyses. Here we use solid-state NMR combined with specific isotopic labeling to probe a key structural feature of the Staphylococcus aureus peptidoglycan quantitatively and nondestructively. We observed that both the cell-wall morphology and the peptidoglycan structure are functions of growth stage in S. aureus synthetic medium (SASM). Specifically, S. aureus cells at stationary phase have thicker cell walls with nonuniformly thickened septa compared to cells in exponential phase, and remarkably, 12% (±2%) of the stems in their peptidoglycan do not have pentaglycine bridges attached. Mechanistically, we determined that these observations are triggered by the depletion of glycine in the nutrient medium, which is coincident with the start of the stationary phase, and that the production of the structurally altered peptidoglycan can be prevented by the addition of excess glycine. We also demonstrated that the structural changes primarily arise within newly synthesized peptidoglycan rather than through the modification of previously synthesized peptidoglycan. Collectively, our observations emphasize the plasticity in bacterial cell-wall assembly and the possibility to manipulate peptidoglycan structure with external stimuli.

  10. Analysis of structural variability in pharmaceutical excipients using solid-state NMR spectroscopy.

    PubMed

    Sperger, Diana M; Munson, Eric Jon

    2011-09-01

    Polysaccharide-based excipients comprise the majority of most solid dosage forms and can vary dramatically in terms of structural and functionally related properties. Analytical methods for characterizing these important formulation components are crucial. Solid-state NMR spectroscopy (SSNMR) can provide a wealth of information on these materials while offering the advantages of non-destructive sample preparation and selectivity. The overall objective of this work is to identify SSNMR parameters that can be used to detect differences among these excipients. Excipients were obtained from a wide range of suppliers and analyzed as received; (13)C SSNMR spectra were acquired using a Chemagnetics CMX-300 spectrometer operating at approximately 75 MHz. The resolution of SSNMR signals of many excipients allows for positive identification of the major form present. Alginic acid and sodium alginate can be differentiated based on carbonyl peak position. Analysis of relative peak intensities provides insight into the purity of a carrageenan sample compared to known standards. The SSNMR spectrum of starch can be used to identify the source and to quantitate the amorphous and crystalline content. Relaxation values and peak areas of starch derivatives can be related to the degree of hydrolysis, providing an alternative method for determining dextrose equivalent. Differences in peak intensities and relaxation time values of HPMC samples can be correlated to the amount of methoxy subsituent groups. Important characteristics of excipients such as form identification, structural differences, crystalline and amorphous content, and water content variations can be detected using SSNMR spectroscopy.

  11. Distinguishing Polymorphs of the Semiconducting Pigment Copper Phthalocyanine by Solid-state NMR and Raman Spectroscopy

    PubMed Central

    Shaibat, Medhat A.; Casabianca, Leah B.; Siberio-Pérez, Diana Y.; Matzger, Adam J; Ishii, Yoshitaka

    2010-01-01

    Cu(II)(phthalocyanine) (CuPc) is broadly utilized as an archetypal molecular semiconductor and is the most widely used blue printing pigment. CuPc crystallizes in six different forms; the chemical and physical properties are substantially modulated by its molecular packing among these polymorphs. Despite the growing importance of this system, spectroscopic identification of different polymorphs for CuPc has posed difficulties. This study presents the first example of spectroscopic distinction of α- and β-forms of CuPc, the most widely used polymorphs, by solid-state NMR (SSNMR) and Raman spectroscopy. 13C high-resolution SSNMR spectra of α- and β-CuPc using very-fast magic angle spinning (VFMAS) at 20 kHz show that hyperfine shifts sensitively reflect polymorphs of CuPc. The experimental results were confirmed by ab initio chemical shift calculations. 13C and 1H SSNMR relaxation times of α- and β-CuPc under VFMAS also showed marked differences, presumably because of the difference in electronic spin correlation times in the two forms. Raman spectroscopy also provided another reliable method of differentiation between the two polymorphs. PMID:20225842

  12. Structure and backbone dynamics of a microcrystalline metalloprotein by solid-state NMR

    PubMed Central

    Knight, Michael J.; Pell, Andrew J.; Bertini, Ivano; Felli, Isabella C.; Gonnelli, Leonardo; Pierattelli, Roberta; Herrmann, Torsten; Emsley, Lyndon; Pintacuda, Guido

    2012-01-01

    We introduce a new approach to improve structural and dynamical determination of large metalloproteins using solid-state nuclear magnetic resonance (NMR) with 1H detection under ultrafast magic angle spinning (MAS). The approach is based on the rapid and sensitive acquisition of an extensive set of 15N and 13C nuclear relaxation rates. The system on which we demonstrate these methods is the enzyme Cu, Zn superoxide dismutase (SOD), which coordinates a Cu ion available either in Cu+ (diamagnetic) or Cu2+ (paramagnetic) form. Paramagnetic relaxation enhancements are obtained from the difference in rates measured in the two forms and are employed as structural constraints for the determination of the protein structure. When added to 1H-1H distance restraints, they are shown to yield a twofold improvement of the precision of the structure. Site-specific order parameters and timescales of motion are obtained by a Gaussian axial fluctuation (GAF) analysis of the relaxation rates of the diamagnetic molecule, and interpreted in relation to backbone structure and metal binding. Timescales for motion are found to be in the range of the overall correlation time in solution, where internal motions characterized here would not be observable. PMID:22723345

  13. A (13)C solid-state NMR investigation of four cocrystals of caffeine and theophylline.

    PubMed

    Vigilante, Nicolas J; Mehta, Manish A

    2017-03-01

    We report an analysis of the (13)C solid-state NMR chemical shift data in a series of four cocrystals involving two active pharmaceutical ingredient (API) mimics (caffeine and theophylline) and two diacid coformers (malonic acid and glutaric acid). Within this controlled set, we make comparisons of the isotropic chemical shifts and the principal values of the chemical shift tensor. The dispersion at 14.1 T (600 MHz (1)H) shows crystallographic splittings in some of the resonances in the magic angle spinning spectra. By comparing the isotropic chemical shifts of individual C atoms across the four cocrystals, we are able to identify pronounced effects on the local electronic structure at some sites. We perform a similar analysis of the principal values of the chemical shift tensors for the anisotropic C atoms (most of the ring C atoms for the API mimics and the carbonyl C atoms of the diacid coformers) and link them to differences in the known crystal structures. We discuss the future prospects for extending this type of study to incorporate the full chemical shift tensor, including its orientation in the crystal frame of reference.

  14. Distinguishing polymorphs of the semiconducting pigment copper phthalocyanine by solid-state NMR and Raman spectroscopy.

    PubMed

    Shaibat, Medhat A; Casabianca, Leah B; Siberio-Pérez, Diana Y; Matzger, Adam J; Ishii, Yoshitaka

    2010-04-08

    Cu(II)(phthalocyanine) (CuPc) is broadly utilized as an archetypal molecular semiconductor and is the most widely used blue printing pigment. CuPc crystallizes in six different forms; the chemical and physical properties are substantially modulated by its molecular packing among these polymorphs. Despite the growing importance of this system, spectroscopic identification of different polymorphs for CuPc has posed difficulties. This study presents the first example of spectroscopic distinction of alpha- and beta-forms of CuPc, the most widely used polymorphs, by solid-state NMR (SSNMR) and Raman spectroscopy. (13)C high-resolution SSNMR spectra of alpha- and beta-CuPc using very-fast magic angle spinning (VFMAS) at 20 kHz show that hyperfine shifts sensitively reflect polymorphs of CuPc. The experimental results were confirmed by ab initio chemical shift calculations. (13)C and (1)H SSNMR relaxation times of alpha- and beta-CuPc under VFMAS also showed marked differences, presumably because of the difference in electronic spin correlation times in the two forms. Raman spectroscopy also provided another reliable method of differentiation between the two polymorphs.

  15. Solid-state NMR and EPR study of fluorinated carbon nanofibers

    SciTech Connect

    Zhang Wei Dubois, Marc Guerin, Katia Hamwi, Andre Giraudet, Jerome Masin, Francis

    2008-08-15

    Carbon nanofibers were fluorinated in two manners, in pure fluorine gas (direct fluorination) and with a fluorinating agent (TbF{sub 4} during the so-called controlled fluorination). The resulting fluorinated nanofibers have been investigated by solid-state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR). This underlines that the fluorination mechanisms differ since a (CF){sub n} structural type is obtained, whatever the temperature, with the controlled reaction, whereas, during the direct process, a (C{sub 2}F){sub n} type is formed over a wide temperature range. Through a careful characterization of the products, i.e. density of dangling bonds (as internal paramagnetic centers), structural type (acting on molecular motion) and specific surface area (related to the amount of physisorbed O{sub 2}), the effect of atmospheric oxygen molecules on the spin-lattice nuclear relaxation has been underlined. - Graphical abstract: Scheme of the fluorination process using F{sub 2} and TbF{sub 4} as fluorinating agent.

  16. Revisiting magnesium chelation by teichoic acid with phosphorus solid-state NMR and theoretical calculations.

    PubMed

    Wickham, Jason R; Halye, Jeffrey L; Kashtanov, Stepan; Khandogin, Jana; Rice, Charles V

    2009-02-19

    Teichoic acids are essential components of the Gram-positive bacterial cell wall. One of their many functions is metal binding, a vital process for bacterial growth. With the combination of phosphorus-31 solid-state NMR spectroscopy and theoretical calculations using density functional theory (DFT), we have determined that the binding mode between teichoic acids and magnesium involves bidentate coordination by the phosphate groups of teichoic acid. Measurement of chemical shift anisotropy tensors gave a reduced anisotropy (delta) of 49.25 ppm and an asymmetry (eta) of 0.7. DFT calculations with diglycerol phosphate and triglycerol diphosphate model compounds were completed with Mg(2+) in anhydrous as well as partially hydrated bidentate and fully hydrated monodentate, bidentate, and bridging binding modes. (31)P CSA tensors were calculated from the energy-minimized model compounds using the combined DFT and GIAO methods, resulting in dramatically different tensor values for each binding mode. The anhydrous bidentate chelation mode was found to be a good approximation of the experimental data, an observation that alters the current monodentate paradigm for metal chelation by teichoic acids.

  17. Solid-state NMR studies of proteins immobilized on inorganic surfaces.

    PubMed

    Shaw, Wendy J

    2015-09-01

    Solid state NMR is the primary tool for studying the quantitative, site-specific structure, orientation, and dynamics of biomineralization proteins under biologically relevant conditions. Two calcium phosphate proteins, statherin (43 amino acids) and leucine rich amelogenin protein (LRAP; 59 amino acids), have been studied in depth and have different dynamic properties and 2D- and 3D-structural features. These differences make it difficult to extract design principles used in nature for building materials with properties such as high strength, unusual morphologies, or uncommon phases. Consequently, design principles needed for developing synthetic materials controlled by proteins are not clear. Many biomineralization proteins are much larger than statherin and LRAP, necessitating the study of larger biomineralization proteins. More recent studies of the significantly larger full-length amelogenin (180 residues) represent a significant step forward to ultimately investigate the full diversity of biomineralization proteins. Interactions of amino acids, a silaffin derived peptide, and the model LK peptide with silica are also being studied, along with qualitative studies of the organic matrices interacting with calcium carbonate. Dipolar recoupling techniques have formed the core of the quantitative studies, yet the need for isolated spin pairs makes this approach costly and time intensive. The use of multi-dimensional techniques to study biomineralization proteins is becoming more common, methodology which, despite its challenges with these difficult-to-study proteins, will continue to drive future advancements in this area. Copyright © 2015 Elsevier Inc. All rights reserved.

  18. Indirect detection of infinite-speed MAS solid-state NMR spectra

    NASA Astrophysics Data System (ADS)

    Perras, Frédéric A.; Venkatesh, Amrit; Hanrahan, Michael P.; Goh, Tian Wei; Huang, Wenyu; Rossini, Aaron J.; Pruski, Marek

    2017-03-01

    Heavy spin-1/2 nuclides are known to possess very large chemical shift anisotropies that can challenge even the most advanced magic-angle-spinning (MAS) techniques. Wide manifolds of overlapping spinning sidebands and insufficient excitation bandwidths often obfuscate meaningful spectral information and force the use of static, low-resolution solid-state (SS)NMR methods for the characterization of materials. To address these issues, we have merged fast-magic-angle-turning (MAT) and dipolar heteronuclear multiple-quantum coherence (D-HMQC) experiments to obtain D-HMQC-MAT pulse sequences which enable the rapid acquisition of 2D SSNMR spectra that correlate isotropic 1H chemical shifts to the indirectly detected isotropic ;infinite-MAS; spectra of heavy spin-1/2 nuclides. For these nuclides, the combination of fast MAS and 1H detection provides a high sensitivity, which rivals the DNP-enhanced ultra-wideline SSNMR. The new pulse sequences were used to determine the Pt coordination environments in a complex mixture of decomposition products of transplatin and in a metal-organic framework with Pt ions coordinated to the linker ligands.

  19. Protein fold determined by paramagnetic magic-angle spinning solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Sengupta, Ishita; Nadaud, Philippe S.; Helmus, Jonathan J.; Schwieters, Charles D.; Jaroniec, Christopher P.

    2012-05-01

    Biomacromolecules that are challenging for the usual structural techniques can be studied with atomic resolution by solid-state NMR spectroscopy. However, the paucity of distance restraints >5 Å, traditionally derived from measurements of magnetic dipole-dipole couplings between protein nuclei, is a major bottleneck that hampers such structure elucidation efforts. Here, we describe a general approach that enables the rapid determination of global protein fold in the solid phase via measurements of nuclear paramagnetic relaxation enhancements (PREs) in several analogues of the protein of interest containing covalently attached paramagnetic tags, without the use of conventional internuclear distance restraints. The method is demonstrated using six cysteine-EDTA-Cu2+ mutants of the 56-residue B1 immunoglobulin-binding domain of protein G, for which ~230 longitudinal backbone 15N PREs corresponding to distances of ~10-20 Å were obtained. The mean protein fold determined in this manner agrees with the X-ray structure with a backbone atom root-mean-square deviation of 1.8 Å.

  20. Spectral editing: selection of methyl groups in multidimensional solid-state magic-angle spinning NMR.

    PubMed

    Jehle, Stefan; Hiller, Matthias; Rehbein, Kristina; Diehl, Anne; Oschkinat, Hartmut; van Rossum, Barth-Jan

    2006-11-01

    A simple spectroscopic filtering technique is presented that may aid the assignment of (13)C and (15)N resonances of methyl-containing amino-acids in solid-state magic-angle spinning (MAS) NMR. A filtering block that selects methyl resonances is introduced in two-dimensional (2D) (13)C-homonuclear and (15)N-(13)C heteronuclear correlation experiments. The 2D (13)C-(13)C correlation spectra are recorded with the methyl filter implemented prior to a (13)C-(13)C mixing step. It is shown that these methyl-filtered (13)C-homonuclear correlation spectra are instrumental in the assignment of C(delta) resonances of leucines by suppression of C(gamma)-C(delta) cross peaks. Further, a methyl filter is implemented prior to a (15)N-(13)C transferred-echo double resonance (TEDOR) exchange scheme to obtain 2D (15)N-(13)C heteronuclear correlation spectra. These experiments provide correlations between methyl groups and backbone amides. Some of the observed sequential (15)N-(13)C correlations form the basis for initial sequence-specific assignments of backbone signals of the outer-membrane protein G.

  1. High-resolution solid-state NMR structure of Alanyl-Prolyl-Glycine

    PubMed Central

    Barnes, Alexander B.; Andreas, Loren B.; Huber, Matthias; Ramachandran, Ramesh; van der Wel, Patrick C.A.; Veshtort, Mikhail; Griffin, Robert G.; Mehta, Manish A.

    2014-01-01

    We present a de novo high-resolution structure of the peptide Alanyl-Prolyl-Glycine using a combination of sensitive solid-state NMR techniques that each yield precise structural constraints. High-quality 13C–13C distance constraints are extracted by fitting rotational resonance width (R2W) experiments using Multimode Multipole Floquet Theory and experimental chemical shift anisotropy (CSA) orientations. In this strategy, a structure is first calculated using DANTE-REDOR and torsion angle measurements and the resulting relative CSA orientations are used as an input parameter in the 13C–13C distance calculations. Finally, a refined structure is calculated using all the constraints. We investigate the effect of different structural constraints on structure quality, as determined by comparison to the crystal structure and also self-consistency of the calculated structures. Inclusion of all or subsets of these constraints into CNS calculations resulted in high-quality structures (0.02 Å backbone RMSD using all 11 constraints). PMID:19596601

  2. Characterization of Stratum Corneum Molecular Dynamics by Natural-Abundance 13C Solid-State NMR

    PubMed Central

    Bouwstra, Joke A.; Sparr, Emma; Topgaard, Daniel

    2013-01-01

    Despite the enormous potential for pharmaceutical applications, there is still a lack of understanding of the molecular details that can contribute to increased permeability of the stratum corneum (SC). To investigate the influence of hydration and heating on the SC, we record the natural-abundance 13C signal of SC using polarization transfer solid-state NMR methods. Resonance lines from all major SC components are assigned. Comparison of the signal intensities obtained with the INEPT and CP pulse sequences gives information on the molecular dynamics of SC components. The majority of the lipids are rigid at 32°C, and those lipids co-exist with a small pool of mobile lipids. The ratio between mobile and rigid lipids increases with hydration. An abrupt change of keratin filament dynamics occurs at RH = 80–85%, from completely rigid to a structure with rigid backbone and mobile protruding terminals. Heating has a strong effect on the lipid mobility, but only a weak influence on the keratin filaments. The results provide novel molecular insight into how the SC constituents are affected by hydration and heating, and improve the understanding of enhanced SC permeability, which is associated with elevated temperatures and SC hydration. PMID:23626744

  3. Solid-state NMR chemical shift assignments for AL-09 VL immunoglobulin light chain fibrils.

    PubMed

    Piehl, Dennis W; Blancas-Mejía, Luis M; Ramirez-Alvarado, Marina; Rienstra, Chad M

    2017-04-01

    Light chain (AL) amyloidosis is a systemic disease characterized by the formation of immunoglobulin light-chain fibrils in critical organs of the body. The light-chain protein AL-09 presents one severe case of cardiac AL amyloidosis, which contains seven mutations in the variable domain (VL) relative to its germline counterpart, κI O18/O8 VL. Three of these mutations are non-conservative-Y87H, N34I, and K42Q-and previous work has shown that they are responsible for significantly reducing the protein's thermodynamic stability, allowing fibril formation to occur with fast kinetics and across a wide-range of pH conditions. Currently, however, there is extremely limited structural information available which explicitly describes the residues that are involved in supporting the misfolded fibril structure. Here, we assign the site-specific (15)N and (13)C chemical shifts of the rigid residues of AL-09 VL fibrils by solid-state NMR, reporting on the regions of the protein involved in the fibril as well as the extent of secondary structure.

  4. Raftlike Mixtures of Sphingomyelin and Cholesterol Investigated by Solid-State 2H NMR Spectroscopy

    PubMed Central

    Bartels, Tim; Lankalapalli, Ravi S.; Bittman, Robert; Beyer, Klaus; Brown, Michael F.

    2009-01-01

    Sphingomyelin is a lipid that is abundant in the nervous systems of mammals, where it is associated with putative microdomains in cellular membranes and undergoes alterations due to aging or neurodegeneration. We investigated the effect of varying the concentration of cholesterol in binary and ternary mixtures with N-palmitoylsphingomyelin (PSM) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) using deuterium nuclear magnetic resonance (2H NMR) spectroscopy in both macroscopically aligned and unoriented multilamellar dispersions. In our experiments, we used PSM and POPC perdeuterated on the N-acyl and sn-1 acyl chains, respectively. By measuring solid-state 2H NMR spectra of the two lipids separately in mixtures with the same compositions as a function of cholesterol mole fraction and temperature, we obtained clear evidence for the coexistence of two liquid-crystalline domains in distinct regions of the phase diagram. According to our analysis of the first moments M1 and the observed 2H NMR spectra, one of the domains appears to be a liquid-ordered phase. We applied a mean-torque potential model as an additional tool to calculate the average hydrocarbon thickness, the area per lipid, and structural parameters such as chain extension and thermal expansion coefficient in order to further define the two coexisting phases. Our data imply that phase separation takes place in raftlike ternary PSM/POPC/cholesterol mixtures over a broad temperature range but vanishes at cholesterol concentrations equal to or greater than a mole fraction of 0.33. Cholesterol interacts preferentially with sphingomyelin only at smaller mole fractions, above which a homogeneous liquid-ordered phase is present. The reasons for these phase separation phenomena seem to be differences in the effects of cholesterol on the configurational order of the palmitoyl chains in PSM-d31 and POPC-d31 and a difference in the affinity of cholesterol for sphingomyelin observed at low temperatures

  5. Thermal decomposition of t-butylamine borane studied by in situ solid state NMR

    SciTech Connect

    Feigerle, J.; Smyrl, N. R.; Morrell, J. S.; Stowe, A. C.

    2010-03-18

    of the amine borane fuel more feasible [22]. In the present study, tert-butylamine borane is investigated by heteronuclear in situ solid state NMR to understand hydrogen release from a hydrocarbon containing amine borane. tbutylamine borane has similar physical properties to amine borane with a melting point of 96 C. A single proton has been replaced with a t-butylamine group resulting in a weakening of the dihydrogen bonding framework. t-butylamine borane has a theoretical gravimetric hydrogen density of 15.1%; however, isobutane can also be evolved rather than hydrogen. If decomposition yields one mole isobutane and two moles hydrogen, 4.5 wt% H2 gas will be evolved. More importantly for the present work, the resulting spent fuel should be comprised of both (BNH)n and (CBNH)n polyimidoboranes.

  6. Solid-state (13)C CP MAS NMR spectroscopy of mushrooms gives directly the ratio between proteins and polysaccharides.

    PubMed

    Pizzoferrato, L; Manzi, P; Bertocchi, F; Fanelli, C; Rotilio, G; Paci, M

    2000-11-01

    The solid-state (13)C CP MAS NMR technique has the potential of monitoring the chemical composition in the solid state of an intact food sample. This property has been utilized to study mushrooms of different species (Pleurotus ostreatus, Pleurotus eryngii, Pleurotus pulmunarius, and Lentinula edodes), already characterized by chemical analyses for protein and dietary fiber components. Solid-state (13)C CP MAS NMR spectroscopy reveals a large difference in the ratio between the glucidic and the proteic resonances probably depending on the mushroom species. An accurate inspection by model compounds and suitable mixtures of proteins and saccharides gives a methodology to interpret these experimental data. A good correlation (R(2) = 0.93; R(2) = 0.81) has been obtained by comparing the NMR data with the results of the chemical analyses. The results suggest the possibility to perform a taxonomic study and/or a nutritional study on the basis of the ratio between protein and polysaccharide levels determined by NMR or chemical methodologies.

  7. Structural study of the membrane protein MscL using cell-free expression and solid-state NMR.

    PubMed

    Abdine, Alaa; Verhoeven, Michiel A; Park, Kyu-Ho; Ghazi, Alexandre; Guittet, Eric; Berrier, Catherine; Van Heijenoort, Carine; Warschawski, Dror E

    2010-05-01

    High-resolution structures of membrane proteins have so far been obtained mostly by X-ray crystallography, on samples where the protein is surrounded by detergent. Recent developments of solid-state NMR have opened the way to a new approach for the study of integral membrane proteins inside a membrane. At the same time, the extension of cell-free expression to the production of membrane proteins allows for the production of proteins tailor made for NMR. We present here an in situ solid-state NMR study of a membrane protein selectively labeled through the use of cell-free expression. The sample consists of MscL (mechano-sensitive channel of large conductance), a 75kDa pentameric alpha-helical ion channel from Escherichia coli, reconstituted in a hydrated lipid bilayer. Compared to a uniformly labeled protein sample, the spectral crowding is greatly reduced in the cell-free expressed protein sample. This approach may be a decisive step required for spectral assignment and structure determination of membrane proteins by solid-state NMR. Copyright 2010 Elsevier Inc. All rights reserved.

  8. Structure of the Dimerization Interface in the Mature HIV-1 Capsid Protein Lattice from Solid State NMR of Tubular Assemblies.

    PubMed

    Bayro, Marvin J; Tycko, Robert

    2016-07-13

    The HIV-1 capsid protein (CA) forms the capsid shell that encloses RNA within a mature HIV-1 virion. Previous studies by electron microscopy have shown that the capsid shell is primarily a triangular lattice of CA hexamers, with variable curvature that destroys the ideal symmetry of a planar lattice. The mature CA lattice depends on CA dimerization, which occurs through interactions between helix 9 segments of the C-terminal domain (CTD) of CA. Several high-resolution structures of the CTD-CTD dimerization interface have been reported, based on X-ray crystallography and multidimensional solution nuclear magnetic resonance (NMR), with significant differences in amino acid side chain conformations and helix 9-helix 9 orientations. In a structural model for tubular CA assemblies based on cryogenic electron microscopy (cryoEM) [Zhao et al. Nature, 2013, 497, 643-646], the dimerization interface is substantially disordered. The dimerization interface structure in noncrystalline CA assemblies and the extent to which this interface is structurally ordered within a curved lattice have therefore been unclear. Here we describe solid state NMR measurements on the dimerization interface in tubular CA assemblies, which contain the curved triangular lattice of a mature virion, including quantitative measurements of intermolecular and intramolecular distances using dipolar recoupling techniques, solid state NMR chemical shifts, and long-range side chain-side chain contacts. When combined with restraints on the distance and orientation between helix 9 segments from the cryoEM study, the solid state NMR data lead to a unique high-resolution structure for the dimerization interface in the noncrystalline lattice of CA tubes. These results demonstrate that CA lattice curvature is not dependent on disorder or variability in the dimerization interface. This work also demonstrates the feasibility of local structure determination within large noncrystalline assemblies formed by high

  9. Elastic deformation and area per lipid of membranes: atomistic view from solid-state deuterium NMR spectroscopy.

    PubMed

    Kinnun, Jacob J; Mallikarjunaiah, K J; Petrache, Horia I; Brown, Michael F

    2015-01-01

    This article reviews the application of solid-state ²H nuclear magnetic resonance (NMR) spectroscopy for investigating the deformation of lipid bilayers at the atomistic level. For liquid-crystalline membranes, the average structure is manifested by the segmental order parameters (SCD) of the lipids. Solid-state ²H NMR yields observables directly related to the stress field of the lipid bilayer. The extent to which lipid bilayers are deformed by osmotic pressure is integral to how lipid-protein interactions affect membrane functions. Calculations of the average area per lipid and related structural properties are pertinent to bilayer remodeling and molecular dynamics (MD) simulations of membranes. To establish structural quantities, such as area per lipid and volumetric bilayer thickness, a mean-torque analysis of ²H NMR order parameters is applied. Osmotic stress is introduced by adding polymer solutions or by gravimetric dehydration, which are thermodynamically equivalent. Solid-state NMR studies of lipids under osmotic stress probe membrane interactions involving collective bilayer undulations, order-director fluctuations, and lipid molecular protrusions. Removal of water yields a reduction of the mean area per lipid, with a corresponding increase in volumetric bilayer thickness, by up to 20% in the liquid-crystalline state. Hydrophobic mismatch can shift protein states involving mechanosensation, transport, and molecular recognition by G-protein-coupled receptors. Measurements of the order parameters versus osmotic pressure yield the elastic area compressibility modulus and the corresponding bilayer thickness at an atomistic level. Solid-state ²H NMR thus reveals how membrane deformation can affect protein conformational changes within the stress field of the lipid bilayer.

  10. Glass Structure by Scattering Methods and Spectroscopy — D. SOLID STATE NMR AS A STRUCTURAL TOOL IN GLASS SCIENCE

    NASA Astrophysics Data System (ADS)

    Eckert, Hellmut

    The following sections are included: * Introduction * Fundamentals of Solid State NMR * Nuclear magnetism and resonance * Spectroscopic technique * Internal interactions * Chemical shielding interaction * Direct magnetic dipole-dipole coupling * Nuclear electric quadrupolar interaction * Experimental separation strategies * Magic-angle spinning * Multi-dimensional NMR * Structural Issues in Non-crystalline Solids and Glasses * Short-Range Order in Oxide Glasses * Local coordination number and symmetry * Bond angle distribution functions * Spatial distribution of modifier cations and structural implications of the mixed-alkali effect * Short-Range Order in Non-Oxide Glasses * Chemical bond distribution and intermediate range order * Chemical equilibria and kinetics in glassforming liquids * Future Perspectives * Towards higher resolution for quadrupolar nuclei * Recovery of dipolar interactions in MAS-NMR: site connectivities * Double resonance NMR in heteronuclear systems * Zero- and double quantum NMR in homonuclear systems * Acknowledgments * References

  11. Visualization and processing of computed solid-state NMR parameters: MagresView and MagresPython.

    PubMed

    Sturniolo, Simone; Green, Timothy F G; Hanson, Robert M; Zilka, Miri; Refson, Keith; Hodgkinson, Paul; Brown, Steven P; Yates, Jonathan R

    2016-09-01

    We introduce two open source tools to aid the processing and visualisation of ab-initio computed solid-state NMR parameters. The Magres file format for computed NMR parameters (as implemented in CASTEP v8.0 and QuantumEspresso v5.0.0) is implemented. MagresView is built upon the widely used Jmol crystal viewer, and provides an intuitive environment to display computed NMR parameters. It can provide simple pictorial representation of one- and two-dimensional NMR spectra as well as output a selected spin-system for exact simulations with dedicated spin-dynamics software. MagresPython provides a simple scripting environment to manipulate large numbers of computed NMR parameters to search for structural correlations. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  12. Fine refinement of solid state structure of racemic form of phospho-tyrosine employing NMR Crystallography approach.

    PubMed

    Paluch, Piotr; Pawlak, Tomasz; Oszajca, Marcin; Lasocha, Wieslaw; Potrzebowski, Marek J

    2015-02-01

    We present step by step facets important in NMR Crystallography strategy employing O-phospho-dl-tyrosine as model sample. The significance of three major techniques being components of this approach: solid state NMR (SS NMR), X-ray diffraction of powdered sample (PXRD) and theoretical calculations (Gauge Invariant Projector Augmented Wave; GIPAW) is discussed. Each experimental technique provides different set of structural constraints. From the PXRD measurement the size of the unit cell, space group and roughly refined molecular structure are established. SS NMR provides information about content of crystallographic asymmetric unit, local geometry, molecular motion in the crystal lattice and hydrogen bonding pattern. GIPAW calculations are employed for validation of quality of elucidation and fine refinement of structure. Crystal and molecular structure of O-phospho-dl-tyrosine solved by NMR Crystallography is deposited at Cambridge Crystallographic Data Center under number CCDC 1005924. Copyright © 2014 Elsevier Inc. All rights reserved.

  13. Retinal Conformation and Dynamics in Activation of Rhodopsin Illuminated by Solid-state 2H NMR Spectroscopy†

    PubMed Central

    Brown, Michael F.; Martínez-Mayorga, Karina; Nakanishi, Koji; Salgado, Gilmar F. J.; Struts, Andrey V.

    2010-01-01

    Solid-state NMR spectroscopy gives a powerful avenue for investigating G protein-coupled receptors and other integral membrane proteins in a native-like environment. This article reviews the use of solid-state 2H NMR to study the retinal cofactor of rhodopsin in the dark state as well as the meta I and meta II photointermediates. Site-specific 2H NMR labels have been introduced into three regions (methyl groups) of retinal that are crucially important for the photochemical function of rhodopsin. Despite its phenomenal stability 2H NMR spectroscopy indicates retinal undergoes rapid fluctuations within the protein binding cavity. The spectral lineshapes reveal the methyl groups spin rapidly about their three-fold (C3) axes with an order parameter for the off-axial motion of SC3 ≈ 0.9. For the dark state, the 2H NMR structure of 11-cis-retinal manifests torsional twisting of both the polyene chain and the β-ionone ring due to steric interactions of the ligand and the protein. Retinal is accommodated within the rhodopsin binding pocket with a negative pretwist about the C11=C12 double bond. Conformational distortion explains its rapid photochemistry and reveals the trajectory of the 11-cis to trans isomerization. In addition, 2H NMR has been applied to study the retinylidene dynamics in the dark and light-activated states. Upon isomerization there are drastic changes in the mobility of all three methyl groups. The relaxation data support an activation mechanism whereby the β-ionone ring of retinal stays in nearly the same environment, without a large displacement of the ligand. Interactions of the β-ionone ring and the retinylidene Schiff base with the protein transmit the force of the retinal isomerization. Solid-state 2H NMR thus provides information about the flow of energy that triggers changes in hydrogen-bonding networks and helix movements in the activation mechanism of the photoreceptor. PMID:19267870

  14. Solid-state NMR/NQR and first-principles study of two niobium halide cluster compounds.

    PubMed

    Perić, Berislav; Gautier, Régis; Pickard, Chris J; Bosiočić, Marko; Grbić, Mihael S; Požek, Miroslav

    2014-01-01

    Two hexanuclear niobium halide cluster compounds with a [Nb6X12](2+) (X=Cl, Br) diamagnetic cluster core, have been studied by a combination of experimental solid-state NMR/NQR techniques and PAW/GIPAW calculations. For niobium sites the NMR parameters were determined by using variable Bo field static broadband NMR measurements and additional NQR measurements. It was found that they possess large positive chemical shifts, contrary to majority of niobium compounds studied so far by solid-state NMR, but in accordance with chemical shifts of (95)Mo nuclei in structurally related compounds containing [Mo6Br8](4+) cluster cores. Experimentally determined δiso((93)Nb) values are in the range from 2,400 to 3,000 ppm. A detailed analysis of geometrical relations between computed electric field gradient (EFG) and chemical shift (CS) tensors with respect to structural features of cluster units was carried out. These tensors on niobium sites are almost axially symmetric with parallel orientation of the largest EFG and the smallest CS principal axes (Vzz and δ33) coinciding with the molecular four-fold axis of the [Nb6X12](2+) unit. Bridging halogen sites are characterized by large asymmetry of EFG and CS tensors, the largest EFG principal axis (Vzz) is perpendicular to the X-Nb bonds, while intermediate EFG principal axis (Vyy) and the largest CS principal axis (δ11) are oriented in the radial direction with respect to the center of the cluster unit. For more symmetrical bromide compound the PAW predictions for EFG parameters are in better correspondence with the NMR/NQR measurements than in the less symmetrical chlorine compound. Theoretically predicted NMR parameters of bridging halogen sites were checked by (79/81)Br NQR and (35)Cl solid-state NMR measurements. Copyright © 2014 Elsevier Inc. All rights reserved.

  15. {sup 9}Be and {sup 11}B NMR study of superconductivity in boron doped UBe{sub 13}

    SciTech Connect

    Ahrens, E.T.; Heffner, R.H.; Hammel, P.C.; Reyes, A.P.; Smith, J.L.; Clark, W.G.

    1994-06-09

    We present {sup 9}Be and {sup 11}B NMR spin-lattice relaxation rate (1/T{sub 1}) measurements in UBe{sub 13-x}B{sub x} for x = 0.03 and 0.07 over the temperature range 0.096 K to 2 K. The temperature dependence of 1/T{sub 1} shows a strong B concentration dependence, especially at low temperatures. We interpret this behavior as consistent with gapless superconductivity induced by the addition of B impurities. The ratio of the {sup 9}Be to {sup 11}B 1/T{sub 1} increases with decreasing temperature below {Tc} indicating additional contributions to the {sup 9}Be relaxation rate, possibly from nuclear spin diffusion to normal-state vortex cores or paramagnetic impurities.

  16. On The Potential of Dynamic Nuclear Polarization Enhanced Diamonds in Solid-State and Dissolution (13) C NMR Spectroscopy.

    PubMed

    Bretschneider, Christian O; Akbey, Ümit; Aussenac, Fabien; Olsen, Greg L; Feintuch, Akiva; Oschkinat, Hartmut; Frydman, Lucio

    2016-09-05

    Dynamic nuclear polarization (DNP) is a versatile option to improve the sensitivity of NMR and MRI. This versatility has elicited interest for overcoming potential limitations of these techniques, including the achievement of solid-state polarization enhancement at ambient conditions, and the maximization of (13) C signal lifetimes for performing in vivo MRI scans. This study explores whether diamond's (13) C behavior in nano- and micro-particles could be used to achieve these ends. The characteristics of diamond's DNP enhancement were analyzed for different magnetic fields, grain sizes, and sample environments ranging from cryogenic to ambient temperatures, in both solution and solid-state experiments. It was found that (13) C NMR signals could be boosted by orders of magnitude in either low- or room-temperature solid-state DNP experiments by utilizing naturally occurring paramagnetic P1 substitutional nitrogen defects. We attribute this behavior to the unusually long electronic/nuclear spin-lattice relaxation times characteristic of diamond, coupled with a time-independent cross-effect-like polarization transfer mechanism facilitated by a matching of the nitrogen-related hyperfine coupling and the (13) C Zeeman splitting. The efficiency of this solid-state polarization process, however, is harder to exploit in dissolution DNP-enhanced MRI contexts. The prospects for utilizing polarized diamond approaching nanoscale dimensions for both solid and solution applications are briefly discussed.

  17. Probing membrane protein structure using water polarization transfer solid-state NMR.

    PubMed

    Williams, Jonathan K; Hong, Mei

    2014-10-01

    Water plays an essential role in the structure and function of proteins, lipid membranes and other biological macromolecules. Solid-state NMR heteronuclear-detected (1)H polarization transfer from water to biomolecules is a versatile approach for studying water-protein, water-membrane, and water-carbohydrate interactions in biology. We review radiofrequency pulse sequences for measuring water polarization transfer to biomolecules, the mechanisms of polarization transfer, and the application of this method to various biological systems. Three polarization transfer mechanisms, chemical exchange, spin diffusion and NOE, manifest themselves at different temperatures, magic-angle-spinning frequencies, and pulse irradiations. Chemical exchange is ubiquitous in all systems examined so far, and spin diffusion plays the key role in polarization transfer within the macromolecule. Tightly bound water molecules with long residence times are rare in proteins at ambient temperature. The water polarization-transfer technique has been used to study the hydration of microcrystalline proteins, lipid membranes, and plant cell wall polysaccharides, and to derive atomic-resolution details of the kinetics and mechanism of ion conduction in channels and pumps. Using this approach, we have measured the water polarization transfer to the transmembrane domain of the influenza M2 protein to obtain information on the structure of this tetrameric proton channel. At short mixing times, the polarization transfer rates are site-specific and depend on the pH, labile protons, sidechain conformation, as well as the radial position of the residues in this four-helix bundle. Despite the multiple dependences, the initial transfer rates reflect the periodic nature of the residue positions from the water-filled pore, thus this technique provides a way of gleaning secondary structure information, helix tilt angle, and the oligomeric structure of membrane proteins.

  18. Solid-State NMR Investigation of Bio-chars Produced from Biomass Components and Whole Biomasses

    DOE PAGES

    Ben, Haoxi; Hao, Naijia; Liu, Qian; ...

    2017-08-24

    Bio-char is a by-product from thermochemical treatment of biomass and has been identified as an energy condensed product with a comparable heating value as commercial coal. However, the combustion of such solid product as an energy resource is only a preliminary application. It is highly possible to convert bio-char, which always has a condensed aromatic and porous structure to various high-value products. The investigations of the structures and formation pathways for the bio-char are very important to any future applications. In this study, six different biomass components, including cellulose, lignin, and tannin, and three whole biomasses—pine wood, pine residue, andmore » pine bark—have been used to produce bio-char at 400, 500, and 600 °C. Solid-state NMR and FT-IR have been employed in this study to characterize the structures for the bio-chars. The results indicated that the bio-chars produced from lignin contained some methoxyl groups, and the bio-chars produced from tannin contained significantly higher amount of phenolic hydroxyl groups. Compared to the bio-chars produced from pine wood and residue, the bio-chars produced from pine bark contained more aromatic C–O bonds, and aliphatic C–O and C–C bonds, which may be due to the significantly higher amount of lignin and tannin in the pine bark. Furthermore, the elevated amounts of aromatic C–O and aliphatic C–O and C–C bonds in the bio-chars from pine bark appeared to be completely decomposed at 600 °C.« less

  19. Probing Membrane Protein Structure Using Water Polarization Transfer Solid-State NMR

    PubMed Central

    Williams, Jonathan K.; Hong, Mei

    2014-01-01

    Water plays an essential role in the structure and function of proteins, lipid membranes and other biological macromolecules. Solid-state NMR heteronuclear-detected 1H polarization transfer from water to biomolecules is a versatile approach for studying water-protein, water-membrane, and water-carbohydrate interactions in biology. We review radiofrequency pulse sequences for measuring water polarization transfer to biomolecules, the mechanisms of polarization transfer, and the application of this method to various biological systems. Three polarization transfer mechanisms, chemical exchange, spin diffusion and NOE, manifest themselves at different temperatures, magic-angle-spinning frequencies, and pulse irradiations. Chemical exchange is ubiquitous in all systems examined so far, and spin diffusion plays the key role in polarization transfer within the macromolecule. Tightly bound water molecules with long residence times are rare in proteins at ambient temperature. The water polarization-transfer technique has been used to study the hydration of microcrystalline proteins, lipid membranes, and plant cell wall polysaccharides, and to derive atomic-resolution details of the kinetics and mechanism of ion conduction in channels and pumps. Using this approach, we have measured the water polarization transfer to the transmembrane peptide of the influenza M2 protein to obtain information on the structure of this tetrameric proton channel. At short mixing times, the polarization transfer rates are site-specific and depend on the pH, labile protons, sidechain conformation, as well as the radial position of the residues in this four-helix bundle. Despite the multiple dependences, the initial transfer rates reflect the periodic nature of the residue positions from the water-filled pore, thus this technique provides a way of gleaning secondary structure information, helix tilt angle, and the oligomeric structure of membrane proteins. PMID:25228502

  20. Rheological and solid-state NMR assessments of copovidone/clotrimazole model solid dispersions.

    PubMed

    Yang, Fengyuan; Su, Yongchao; Zhu, Lei; Brown, Chad D; Rosen, Lawrence A; Rosenberg, Kenneth J

    2016-03-16

    This study aims to assess several model solid dispersions by using dynamic oscillatory rheology, solid-state NMR and other solid phase characterization techniques, and correlate their viscoelastic responses with processing methods and microstructures. A model active pharmaceutical ingredient (API), clotrimazole, was compounded with copovidone to form solid dispersions via various techniques with different mixing capabilities. Physicochemical characterizations of the resulting solid dispersions demonstrated that simple physical mixing led to a poorly mixed blend manifested by existence of large API crystalline content and heterogeneous distribution. Cryogenic milling significantly improved mixing of two components as a result of reduced particle size and increased contact surface area, but produced limited amorphous content. In contrast, hot melt extrusion (HME) processing resulted in a homogenous amorphous solid dispersion because of its inherent mixing efficiency. Storage modulus and viscosities versus frequency of different solid dispersions indicated that the incorporation of API into the polymer matrix resulted in a plasticizing effect which reduced the viscosity. The crystalline/aggregated forms of API also exhibited more elastic response than its amorphous/dispersed counterpart. Temperature ramps of the physical mixture with high API concentration captured a critical temperature, at which a bump was observed in damping factor. This bump was attributed to the dissolution of crystalline API into the polymer. In addition, heating-cooling cycles of various solid dispersions suggested that cryomilling and HME processing could form a homogeneous solid dispersion at low API content, whereas high drug concentration led to a relatively unstable dispersion due to supersaturation of API in the polymer. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Structural water in carbonated hydroxylapatite and fluorapatite: confirmation by solid state (2)H NMR.

    PubMed

    Yoder, Claude H; Pasteris, Jill D; Worcester, Kimberly N; Schermerhorn, Demetra V

    2012-01-01

    Water is well recognized as an important component in bone, typically regarded as a constituent of collagen, a pore-filling fluid in bone, and an adsorbed species on the surface of bone crystallites. The possible siting and role of water within the structure of the apatite crystallites have not been fully explored. In our experiments, carbonated hydroxyl- and fluorapatites were prepared in D(2)O and characterized by elemental analysis, thermal gravimetric analysis, powder X-ray diffraction, and infrared and Raman spectroscopy. Two hydroxylapatites and two fluorapatites, with widely different amounts of carbonate were analyzed by solid state (2)H NMR spectroscopy using the quadrupole echo pulse sequence, and each spectrum showed one single line as well as a low-intensity powder pattern. The relaxation time of 7.1 ms for 5.9 wt% carbonated hydroxylapatite indicates that the single line is likely due to rapid, high-symmetry jumps in translationally rigid D(2)O molecules, indicative of structural incorporation within the lattice. Discrimination between structurally incorporated and adsorbed water is enhanced by the rapid exchange of surface D(2)O with atmospheric H(2)O. Moreover, a (2)H resonance was observed for samples dried under a variety of conditions, including in vacuo heating to 150°C. In contrast, a sample heated to 500°C produced no deuterium resonance, indicating that structural water had been released by that temperature. We propose that water is located in the c-axis channels. Because structural water is observed even for apatites with very low carbonate content, some of the water molecules must lie between the monovalent ions.

  2. Susceptibility corrections in solid-state NMR experiments with oriented membrane samples. Part I: applications

    NASA Astrophysics Data System (ADS)

    Glaser, Ralf W.; Ulrich, Anne S.

    2003-09-01

    Chemical shift referencing of solid-state NMR experiments on oriented membranes has to compensate for bulk magnetic susceptibility effects that are associated with the non-spherical sample shape, as described in the accompanying paper [J. Magn. Reson. 164 (2003) 115-127]. The resulting frequency deviations can be on the order of 10 ppm, which is serious for nuclei with a narrow chemical shift anisotropy such as 1H or 13C, and in some cases even 19F. Two referencing schemes are proposed here to compensate for these effects: A flat (0.4 mm) glass container with an isotropic reference molecule dissolved in a thin film of liquid is stacked on top of the oriented membrane sample. Alternatively, the intrinsic proton signal of the hydrated lipid can be used for chemical shift referencing. Further aspects related to magnetic susceptibility are discussed, such as air gaps in susceptibility-matched probeheads, the benefits of shimming, and limitations in the accuracy of orientational constraints. A biological application is illustrated by a series of experiments on the antimicrobial peptide PGLa, aimed at understanding its concentration-dependent membranolytic effect. To address a wide range of molar peptide/lipid ratios between 1:3000 and 1:8, multilayers of hydrated DMPC containing a 19F-labeled peptide were oriented between stacked glass plates. Maintaining an approximately constant amount of peptide gives rise to thick samples (18 plates) at low, and thin samples (3 plates) at high peptide/lipid ratio. Accurate referencing was critical to reveal a small but significant change over 5 ppm in the anisotropic chemical shift of the 19F label on the peptide, indicative of a change in the orientation and/or dynamics of PGLa in the membrane.

  3. Probing membrane protein structure using water polarization transfer solid-state NMR

    NASA Astrophysics Data System (ADS)

    Williams, Jonathan K.; Hong, Mei

    2014-10-01

    Water plays an essential role in the structure and function of proteins, lipid membranes and other biological macromolecules. Solid-state NMR heteronuclear-detected 1H polarization transfer from water to biomolecules is a versatile approach for studying water-protein, water-membrane, and water-carbohydrate interactions in biology. We review radiofrequency pulse sequences for measuring water polarization transfer to biomolecules, the mechanisms of polarization transfer, and the application of this method to various biological systems. Three polarization transfer mechanisms, chemical exchange, spin diffusion and NOE, manifest themselves at different temperatures, magic-angle-spinning frequencies, and pulse irradiations. Chemical exchange is ubiquitous in all systems examined so far, and spin diffusion plays the key role in polarization transfer within the macromolecule. Tightly bound water molecules with long residence times are rare in proteins at ambient temperature. The water polarization-transfer technique has been used to study the hydration of microcrystalline proteins, lipid membranes, and plant cell wall polysaccharides, and to derive atomic-resolution details of the kinetics and mechanism of ion conduction in channels and pumps. Using this approach, we have measured the water polarization transfer to the transmembrane domain of the influenza M2 protein to obtain information on the structure of this tetrameric proton channel. At short mixing times, the polarization transfer rates are site-specific and depend on the pH, labile protons, sidechain conformation, as well as the radial position of the residues in this four-helix bundle. Despite the multiple dependences, the initial transfer rates reflect the periodic nature of the residue positions from the water-filled pore, thus this technique provides a way of gleaning secondary structure information, helix tilt angle, and the oligomeric structure of membrane proteins.

  4. Solid-state 13C NMR and molecular modeling studies of acetyl aleuritolic acid obtained from Croton cajucara Benth

    NASA Astrophysics Data System (ADS)

    da Silva San Gil, Rosane Aguiar; Albuquerque, Magaly Girão; de Alencastro, Ricardo Bicca; da Cunha Pinto, Angelo; do Espírito Santo Gomes, Fabiano; de Castro Dantas, Tereza Neuma; Maciel, Maria Aparecida Medeiros

    2008-08-01

    Solid-state 13C nuclear magnetic resonance ( 13C NMR) with magic-angle spinning (MAS) and with cross-polarization and magic-angle spinning (CP/MAS) spectra, and differential scanning calorimetry (DSC) techniques were used to obtain structural data from a sample of acetyl aleuritolic acid (AAA) extracted from the stem bark of Croton cajucara Benth. (Euphorbiaceae) and recrystallized from acetone. Since solid-state 13C NMR results suggested the presence of more than one molecule in the unitary cell for the AAA, DSC analysis and molecular modeling calculations were used to access this possibility. The absence of phase transition peaks in the DSC spectra and the dimeric models of AAA simulated using the semi-empirical PM3 method are in agreement with that proposal.

  5. Structure and ionic interactions of organic-inorganic composite polymer electrolytes studied by solid-state NMR and Raman spectroscopy.

    PubMed

    Joo, Chan Gyu; Bronstein, Lyudmila M; Karlinsey, Robert L; Zwanziger, Josef W

    2002-01-01

    Solid-state NMR studies of composite polymer electrolytes are reported. The materials consist of polyethylene oxide and an organic inorganic composite, together with a lithium salt, and are candidates for electrolytes in solid-state lithium ion batteries. Silicon and aluminum MAS and multiple quantum MAS are used to characterize the network character of the organic-inorganic composite, and spin diffusion measurements are used to determine the nanostructure of the polymer/composite blending. Multiple quantum spin counting is used to measure the ion aggregation. The NMR results are supported by Raman spectra, calorimetry, and impedance spectroscopy. From these experiments it is concluded that the composite suppresses polymer crystallization without suppressing its local mobility, and also suppresses the tendency for the ions to aggregate. This polymer composite thus appears very promising for application in lithium ion batteries.

  6. The Surface of Nanoparticle Silicon as Studied by Solid-State NMR

    PubMed Central

    Faulkner, Rebecca A.; DiVerdi, Joseph A.; Yang, Yuan; Kobayashi, Takeshi; Maciel, Gary E.

    2012-01-01

    The surface structure and adjacent interior of commercially available silicon nanopowder (np-Si) was studied using multinuclear, solid-state NMR spectroscopy. The results are consistent with an overall picture in which the bulk of the np-Si interior consists of highly ordered (“crystalline”) silicon atoms, each bound tetrahedrally to four other silicon atoms. From a combination of 1H, 29Si and 2H magic-angle-spinning (MAS) NMR results and quantum mechanical 29Si chemical shift calculations, silicon atoms on the surface of “as-received” np-Si were found to exist in a variety of chemical structures, with apparent populations in the order (a) (Si–O–)3Si–H > (b) (Si–O–)3SiOH > (c) (HO–)nSi(Si)m(–OSi)4−m−n ≈ (d) (Si–O–)2Si(H)OH > (e) (Si–O–)2Si(–OH)2 > (f) (Si–O–)4Si, where Si stands for a surface silicon atom and Si represents another silicon atom that is attached to Si by either a Si–Si bond or a Si–O–Si linkage. The relative populations of each of these structures can be modified by chemical treatment, including with O2 gas at elevated temperature. A deliberately oxidized sample displays an increased population of (Si–O–)3Si–H, as well as (Si–O–)3SiOH sites. Considerable heterogeneity of some surface structures was observed. A combination of 1H and 2H MAS experiments provide evidence for a substantial population of silanol (Si–OH) moieties, some of which are not readily H-exchangeable, along with the dominant Si–H sites, on the surface of “as-received” np-Si; the silanol moieties are enhanced by deliberate oxidation. An extension of the DEPTH background suppression method is also demonstrated that permits measurement of the T2 relaxation parameter simultaneously with background suppression. PMID:28809292

  7. Quantitative determination of lead in mixtures of lead(II) halidesusing solid-state 207pb nmr spectroscopy

    SciTech Connect

    Glatfelter, Alicia; Stephenson, Nicole; Bai, Shi; Dybowski,Cecil; Perry, Dale L.

    2006-11-01

    A multi-spectrum technique for facile, quantitativedetermination of lead in solid materials using solid-state 207Pb NMR thatavoids the major problem of uniform excitation across a wide spectralrange has been demonstrated. The method can be employed without chemicalseparation or other chemical manipulations and without any prior samplepreparation, resulting in a non-destructive analysis, and producingresults that are in agreement with gravimetric analyses of mixed samplesof the lead halides.

  8. Sodium ion effect on silk fibroin conformation characterized by solid-state NMR and generalized 2D NMR NMR correlation

    NASA Astrophysics Data System (ADS)

    Ruan, Qing-Xia; Zhou, Ping

    2008-07-01

    In the present work, we investigated Na + ion effect on the silk fibroin (SF) conformation. Samples are Na +-involved regenerated silk fibroin films. 13C CP-MAS NMR demonstrates that as added [Na +] increases, partial silk fibroin conformation transit from helix-form to β-form at certain Na + ion concentration which is much higher than that in Bombyx mori silkworm gland. The generalized two-dimensional NMR-NMR correlation analysis reveals that silk fibroin undergoes several intermediate states during its conformation transition process as [Na +] increase. The appearance order of the intermediates is followed as: helix and/or random coil → helix-like → β-sheet-like → β-sheet, which is the same as that produced by pH decrease from 6.8 to 4.8 in the resultant regenerated silk fibroin films. The binding sites of Na + to silk fibroin might involve the carbonyl oxygen atom of certain amino acids sequence which could promote the formation of β-sheet conformation. Since the Na +sbnd O bond is weak, the ability of Na + inducing the secondary structure transition is weaker than those of Ca 2+, Cu 2+ and even K +. It is maybe a reason why the sodium content is much lower than potassium in the silkworm gland.

  9. Adsorption-desorption induced structural changes of Cu-MOF evidenced by solid state NMR and EPR spectroscopy.

    PubMed

    Jiang, Yijiao; Huang, Jun; Kasumaj, Besnik; Jeschke, Gunnar; Hunger, Michael; Mallat, Tamas; Baiker, Alfons

    2009-02-18

    Adsorption-desorption induced structural changes of Cu(bpy)(H(2)O)(2)(BF(4)),(bpy) (bpy = 4,4'-bipyridine) [Cu-MOF] have been evidenced by combined NMR and EPR spectroscopy. Upon adsorption of probe molecules even at a few mbar, EPR spectra show that they are activated to form complexes at Cu(II) sites, which results in a change of the Cu-MOF's structure as indicated by a high-field shift of the (11)B MAS NMR. After desorption, both EPR and (11)B MAS NMR spectra evidenced that the structure of the Cu-MOF reversibly shifted to the original state. This observation indicates that MOFs can undergo structural changes during processes where adsorption-desorption steps are involved such as gas storage, separation, and catalysis.

  10. Structure of the light-harvesting bacteriochlorophyll c assembly in chlorosomes from Chlorobium limicola determined by solid-state NMR

    PubMed Central

    Egawa, Ayako; Fujiwara, Toshimichi; Mizoguchi, Tadashi; Kakitani, Yoshinori; Koyama, Yasushi; Akutsu, Hideo

    2007-01-01

    We have determined the atomic structure of the bacteriochlorophyll c (BChl c) assembly in a huge light-harvesting organelle, the chlorosome of green photosynthetic bacteria, by solid-state NMR. Previous electron microscopic and spectroscopic studies indicated that chlorosomes have a cylindrical architecture with a diameter of ≈10 nm consisting of layered BChl molecules. Assembly structures in huge noncrystalline chlorosomes have been proposed based mainly on structure-dependent chemical shifts and a few distances acquired by solid-state NMR, but those studies did not provide a definite structure. Our approach is based on 13C dipolar spin-diffusion solid-state NMR of uniformly 13C-labeled chlorosomes under magic-angle spinning. Approximately 90 intermolecular CC distances were obtained by simultaneous assignment of distance correlations and structure optimization preceded by polarization-transfer matrix analysis. It was determined from the ≈90 intermolecular distances that BChl c molecules form piggyback-dimer-based parallel layers. This finding rules out the well known monomer-based structures. A molecular model of the cylinder in the chlorosome was built by using this structure. It provided insights into the mechanisms of efficient light harvesting and excitation transfer to the reaction centers. This work constitutes an important advance in the structure determination of huge intact systems that cannot be crystallized. PMID:17215361

  11. Dynamics of benzimidazole ethylphosphonate: a solid-state NMR study of anhydrous composite proton-conducting electrolytes.

    PubMed

    Yan, Z Blossom; De Almeida, Nicole E; Traer, Jason W; Goward, Gillian R

    2013-11-07

    Imidazole phosphate and phosphonate solid acids model the hydrogen-bonding networks and dynamics of the anhydrous electrolyte candidate for proton exchange membrane fuel cells. Solid-state NMR reveals that phosphate and phosphonate anion dynamics dominate the rate of long-range proton transport, and that the presence of a membrane host facilitates proton mobility, as evidenced by a decreased correlation time of the composites (80 ± 15 ms) relative to the pristine salt (101 ± 5 ms). Benzimidazole ethylphosphonate (Bi-ePA) is chosen as a model salt to investigate the membrane system. The hydrogen-bonding structure of Bi-ePA is established using X-ray diffraction coupled with solid-state (1)H-(1)H DQC NMR. The anion dynamics has been determined using solid-state (31)P CODEX NMR. By comparing the dynamics of ethylphosphonate groups in pristine salt and membrane-salt composites, it is clear that the rotation process involves three-site exchange. Through data interpretation, a stretched exponential function is introduced with the stretching exponent, β, ranging 0 < β ≤ 1. The (31)P CODEX data for pristine salt are fitted with single exponential decay where β = 1; however, the data for the membrane-salt composites are fitted with stretched exponential functions, where β has a constant value of 0.5. This β value suggests a non-Gaussian distribution of the dynamic systems in the composite sample, which is introduced by the membrane host.

  12. Solid-state NMR on bacterial cells: selective cell wall signal enhancement and resolution improvement using dynamic nuclear polarization.

    PubMed

    Takahashi, Hiroki; Ayala, Isabel; Bardet, Michel; De Paëpe, Gaël; Simorre, Jean-Pierre; Hediger, Sabine

    2013-04-03

    Dynamic nuclear polarization (DNP) enhanced solid-state nuclear magnetic resonance (NMR) has recently emerged as a powerful technique for the study of material surfaces. In this study, we demonstrate its potential to investigate cell surface in intact cells. Using Bacillus subtilis bacterial cells as an example, it is shown that the polarizing agent 1-(TEMPO-4-oxy)-3-(TEMPO-4-amino)propan-2-ol (TOTAPOL) has a strong binding affinity to cell wall polymers (peptidoglycan). This particular interaction is thoroughly investigated with a systematic study on extracted cell wall materials, disrupted cells, and entire cells, which proved that TOTAPOL is mainly accumulating in the cell wall. This property is used on one hand to selectively enhance or suppress cell wall signals by controlling radical concentrations and on the other hand to improve spectral resolution by means of a difference spectrum. Comparing DNP-enhanced and conventional solid-state NMR, an absolute sensitivity ratio of 24 was obtained on the entire cell sample. This important increase in sensitivity together with the possibility of enhancing specifically cell wall signals and improving resolution really opens new avenues for the use of DNP-enhanced solid-state NMR as an on-cell investigation tool.

  13. Solid-state NMR as an effective method of polymorphic analysis: solid dosage forms of clopidogrel hydrogensulfate.

    PubMed

    Pindelska, Edyta; Szeleszczuk, Lukasz; Pisklak, Dariusz Maciej; Mazurek, Andrzej; Kolodziejski, Waclaw

    2015-01-01

    Clopidogrel hydrogensulfate (HSCL) is an antiplatelet agent, one of top-selling drugs in the world. In this paper, we have described a rapid and convenient method of verification which polymorph of HSCL is present in its final solid dosage form. Our methodology based on solid-state NMR spectroscopy and ab initio gauge-including projector-augmented wave calculations of NMR shielding constants is appropriate for currently available commercial solid dosage forms of HSCL. Furthermore, such structural characterization can assist with the development of new pharmaceutical products containing HSCL and also be useful in the identification of counterfeit drugs.

  14. The contribution of solid-state NMR spectroscopy to understanding biomineralization: Atomic and molecular structure of bone

    NASA Astrophysics Data System (ADS)

    Duer, Melinda J.

    2015-04-01

    Solid-state NMR spectroscopy has had a major impact on our understanding of the structure of mineralized tissues, in particular bone. Bone exemplifies the organic-inorganic composite structure inherent in mineralized tissues. The organic component of the extracellular matrix in bone is primarily composed of ordered fibrils of collagen triple-helical molecules, in which the inorganic component, calcium phosphate particles, composed of stacks of mineral platelets, are arranged around the fibrils. This perspective argues that key factors in our current structural model of bone mineral have come about through NMR spectroscopy and have yielded the primary information on how the mineral particles interface and bind with the underlying organic matrix. The structure of collagen within the organic matrix of bone or any other structural tissue has yet to be determined, but here too, this perspective shows there has been real progress made through application of solid-state NMR spectroscopy in conjunction with other techniques. In particular, NMR spectroscopy has highlighted the fact that even within these structural proteins, there is considerable dynamics, which suggests that one should be cautious when using inherently static structural models, such as those arising from X-ray diffraction analyses, to gain insight into molecular roles. It is clear that the NMR approach is still in its infancy in this area, and that we can expect many more developments in the future, particularly in understanding the molecular mechanisms of bone diseases and ageing.

  15. Molecular characterization and quantification using state of the art solid-state adiabatic TOBSY NMR in burn trauma.

    PubMed

    Righi, Valeria; Andronesi, Ovidiu; Mintzopoulos, Dionyssios; Tzika, A Aria

    2009-12-01

    We describe a novel solid-state nuclear magnetic resonance (NMR) method that maximizes the advantages of high-resolution magic-angle-spinning (HRMAS), relative conventional liquid-state NMR approaches, when applied to intact biopsies of skeletal muscle specimens collected from burn trauma patients. This novel method, termed optimized adiabatic TOtal through Bond correlation SpectroscopY (TOBSY) solid-state NMR pulse sequence for two-dimensional (2D) 1H-1H homonuclear scalar-coupling longitudinal isotropic mixing, was demonstrated to provide a 40-60% improvement in signal-to-noise ratio (SNR) relative to its liquid-state analogue TOCSY (TOtal Correlation SpectroscopY). Using 1- and 2-dimensional HRMAS NMR experiments, we identified several metabolites in burned tissues. Quantification of metabolites in burned tissues showed increased levels of lipid compounds, intracellular metabolites (e.g., taurine and phosphocreatine) and substantially decreased water-soluble metabolites (e.g., glutathione, carnosine, glucose, glutamine/glutamate and alanine). These findings demonstrate that HRMAS NMR Spectroscopy using TOBSY is a feasible technique that reveals new insights into the pathophysiology of burn trauma. Moreover, this method has applications that facilitate the development of novel therapeutic strategies.

  16. Lipid bilayer preparations of membrane proteins for oriented and magic-angle spinning solid-state NMR samples

    PubMed Central

    Das, Nabanita; Murray, Dylan T; Cross, Timothy A

    2014-01-01

    Solid-state NMR spectroscopy has been used successfully for characterizing the structure and dynamics of membrane proteins as well as their interactions with other proteins in lipid bilayers. such an environment is often necessary for achieving native-like structures. sample preparation is the key to this success. Here we present a detailed description of a robust protocol that results in high-quality membrane protein samples for both magic-angle spinning and oriented-sample solid-state NMR. the procedure is demonstrated using two proteins: CrgA (two transmembrane helices) and rv1861 (three transmembrane helices), both from Mycobacterium tuberculosis. the success of this procedure relies on two points. First, for samples for both types of NMR experiment, the reconstitution of the protein from a detergent environment to an environment in which it is incorporated into liposomes results in ‘complete’ removal of detergent. second, for the oriented samples, proper dehydration followed by rehydration of the proteoliposomes is essential. By using this protocol, proteoliposome samples for magic-angle spinning NMR and uniformly aligned samples (orientational mosaicity of <1°) for oriented-sample NMR can be obtained within 10 d. PMID:24157546

  17. The contribution of solid-state NMR spectroscopy to understanding biomineralization: atomic and molecular structure of bone.

    PubMed

    Duer, Melinda J

    2015-04-01

    Solid-state NMR spectroscopy has had a major impact on our understanding of the structure of mineralized tissues, in particular bone. Bone exemplifies the organic-inorganic composite structure inherent in mineralized tissues. The organic component of the extracellular matrix in bone is primarily composed of ordered fibrils of collagen triple-helical molecules, in which the inorganic component, calcium phosphate particles, composed of stacks of mineral platelets, are arranged around the fibrils. This perspective argues that key factors in our current structural model of bone mineral have come about through NMR spectroscopy and have yielded the primary information on how the mineral particles interface and bind with the underlying organic matrix. The structure of collagen within the organic matrix of bone or any other structural tissue has yet to be determined, but here too, this perspective shows there has been real progress made through application of solid-state NMR spectroscopy in conjunction with other techniques. In particular, NMR spectroscopy has highlighted the fact that even within these structural proteins, there is considerable dynamics, which suggests that one should be cautious when using inherently static structural models, such as those arising from X-ray diffraction analyses, to gain insight into molecular roles. It is clear that the NMR approach is still in its infancy in this area, and that we can expect many more developments in the future, particularly in understanding the molecular mechanisms of bone diseases and ageing. Copyright © 2015 Elsevier Inc. All rights reserved.

  18. Powder-XRD and (14) N magic angle-spinning solid-state NMR spectroscopy of some metal nitrides.

    PubMed

    Kempgens, Pierre; Britton, Jonathan

    2016-05-01

    Some metal nitrides (TiN, ZrN, InN, GaN, Ca3 N2 , Mg3 N2 , and Ge3 N4 ) have been studied by powder X-ray diffraction (XRD) and (14) N magic angle-spinning (MAS) solid-state NMR spectroscopy. For Ca3 N2 , Mg3 N2 , and Ge3 N4 , no (14) N NMR signal was observed. Low speed (νr  = 2 kHz for TiN, ZrN, and GaN; νr  = 1 kHz for InN) and 'high speed' (νr  = 15 kHz for TiN; νr  = 5 kHz for ZrN; νr  = 10 kHz for InN and GaN) MAS NMR experiments were performed. For TiN, ZrN, InN, and GaN, powder-XRD was used to identify the phases present in each sample. The number of peaks observed for each sample in their (14) N MAS solid-state NMR spectrum matches perfectly well with the number of nitrogen-containing phases identified by powder-XRD. The (14) N MAS solid-state NMR spectra are symmetric and dominated by the quadrupolar interaction. The envelopes of the spinning sidebands manifold are Lorentzian, and it is concluded that there is a distribution of the quadrupolar coupling constants Qcc 's arising from structural defects in the compounds studied.

  19. Characterization of Protein-Protein Interfaces in Large Complexes by Solid-State NMR Solvent Paramagnetic Relaxation Enhancements.

    PubMed

    Öster, Carl; Kosol, Simone; Hartlmüller, Christoph; Lamley, Jonathan M; Iuga, Dinu; Oss, Andres; Org, Mai-Liis; Vanatalu, Kalju; Samoson, Ago; Madl, Tobias; Lewandowski, Józef R

    2017-09-06

    Solid-state NMR is becoming a viable alternative for obtaining information about structures and dynamics of large biomolecular complexes, including ones that are not accessible to other high-resolution biophysical techniques. In this context, methods for probing protein-protein interfaces at atomic resolution are highly desirable. Solvent paramagnetic relaxation enhancements (sPREs) proved to be a powerful method for probing protein-protein interfaces in large complexes in solution but have not been employed toward this goal in the solid state. We demonstrate that (1)H and (15)N relaxation-based sPREs provide a powerful tool for characterizing intermolecular interactions in large assemblies in the solid state. We present approaches for measuring sPREs in practically the entire range of magic angle spinning frequencies used for biomolecular studies and discuss their benefits and limitations. We validate the approach on crystalline GB1, with our experimental results in good agreement with theoretical predictions. Finally, we use sPREs to characterize protein-protein interfaces in the GB1 complex with immunoglobulin G (IgG). Our results suggest the potential existence of an additional binding site and provide new insights into GB1:IgG complex structure that amend and revise the current model available from studies with IgG fragments. We demonstrate sPREs as a practical, widely applicable, robust, and very sensitive technique for determining intermolecular interaction interfaces in large biomolecular complexes in the solid state.

  20. Characterization of Protein–Protein Interfaces in Large Complexes by Solid-State NMR Solvent Paramagnetic Relaxation Enhancements

    PubMed Central

    2017-01-01

    Solid-state NMR is becoming a viable alternative for obtaining information about structures and dynamics of large biomolecular complexes, including ones that are not accessible to other high-resolution biophysical techniques. In this context, methods for probing protein–protein interfaces at atomic resolution are highly desirable. Solvent paramagnetic relaxation enhancements (sPREs) proved to be a powerful method for probing protein–protein interfaces in large complexes in solution but have not been employed toward this goal in the solid state. We demonstrate that 1H and 15N relaxation-based sPREs provide a powerful tool for characterizing intermolecular interactions in large assemblies in the solid state. We present approaches for measuring sPREs in practically the entire range of magic angle spinning frequencies used for biomolecular studies and discuss their benefits and limitations. We validate the approach on crystalline GB1, with our experimental results in good agreement with theoretical predictions. Finally, we use sPREs to characterize protein–protein interfaces in the GB1 complex with immunoglobulin G (IgG). Our results suggest the potential existence of an additional binding site and provide new insights into GB1:IgG complex structure that amend and revise the current model available from studies with IgG fragments. We demonstrate sPREs as a practical, widely applicable, robust, and very sensitive technique for determining intermolecular interaction interfaces in large biomolecular complexes in the solid state. PMID:28780861

  1. Methionine bound to Pd/γ-Al2O3 catalysts studied by solid-state (13)C NMR.

    PubMed

    Johnson, Robert L; Schwartz, Thomas J; Dumesic, James A; Schmidt-Rohr, Klaus

    2015-11-01

    The chemisorption and breakdown of methionine (Met) adsorbed on Pd/γ-Al2O3 catalysts were investigated by solid-state NMR. (13)C-enriched Met (ca. 0.4mg) impregnated onto γ-Al2O3 or Pd/γ-Al2O3 gives NMR spectra with characteristic features of binding to γ-Al2O3, to Pd nanoparticles, and oxidative or reductive breakdown of Met. The SCH3 groups of Met showed characteristic changes in chemical shift on γ-Al2O3 (13ppm) vs. Pd (19ppm), providing strong evidence for preferential binding to Pd, while the NC carbon generates a small resonance at 96ppm assigned to a distinct nonprotonated species bound to O or Pd. Additionally, NMR shows that the SCH3 groups of Met are mobile on γ-Al2O3 but immobilized by binding to Pd particles; on small Pd particles (ca. 4nm), the NCH groups undergo large-amplitude motions. In a reducing environment, Met breaks down by C-S bond cleavage followed by formation of C2-C4 organic acids. The SCH3 signal shifts to 22ppm, which is likely the signature of the principal species responsible for strong catalyst inhibition. These experiments demonstrate that solid-state magic-angle spinning NMR of (13)C-enriched Met can be a sensitive probe to investigate catalyst surfaces and characterize catalyst inhibition both before reaction and postmortem.

  2. Tannin fingerprinting in vegetable tanned leather by solid state NMR spectroscopy and comparison with leathers tanned by other processes.

    PubMed

    Romer, Frederik H; Underwood, Andrew P; Senekal, Nadine D; Bonnet, Susan L; Duer, Melinda J; Reid, David G; van der Westhuizen, Jan H

    2011-01-28

    Solid state ¹³C-NMR spectra of pure tannin powders from four different sources--mimosa, quebracho, chestnut and tara--are readily distinguishable from each other, both in pure commercial powder form, and in leather which they have been used to tan. Groups of signals indicative of the source, and type (condensed vs. hydrolyzable) of tannin used in the manufacture are well resolved in the spectra of the finished leathers. These fingerprints are compared with those arising from leathers tanned with other common tanning agents. Paramagnetic chromium (III) tanning causes widespread but selective disappearance of signals from the spectrum of leather collagen, including resonances from acidic aspartyl and glutamyl residues, likely bound to Cr (III) structures. Aluminium (III) and glutaraldehyde tanning both cause considerable leather collagen signal sharpening suggesting some increase in molecular structural ordering. The ²⁷Al-NMR signal from the former material is consistent with an octahedral coordination by oxygen ligands. Solid state NMR thus provides easily recognisable reagent specific spectral fingerprints of the products of vegetable and some other common tanning processes. Because spectra are related to molecular properties, NMR is potentially a powerful tool in leather process enhancement and quality or provenance assurance.

  3. Solid-state 19F-NMR analysis of 19F-labeled tryptophan in gramicidin A in oriented membranes.

    PubMed Central

    Grage, Stephan L; Wang, Junfeng; Cross, Timothy A; Ulrich, Anne S

    2002-01-01

    The response of membrane-associated peptides toward the lipid environment or other binding partners can be monitored by solid-state NMR of suitably labeled side chains. Tryptophan is a prominent amino acid in transmembrane helices, and its (19)F-labeled analogues are generally biocompatible and cause little structural perturbation. Hence, we use 5F-Trp as a highly sensitive NMR probe to monitor the conformation and dynamics of the indole ring. To establish this (19)F-NMR strategy, gramicidin A was labeled with 5F-Trp in position 13 or 15, whose chi(1)/chi(2) torsion angles are known from previous (2)H-NMR studies. First, the alignment of the (19)F chemical shift anisotropy tensor within the membrane was deduced by lineshape analysis of oriented samples. Next, the three principal axes of the (19)F chemical shift anisotropy tensor were assigned within the molecular frame of the indole ring. Finally, determination of chi(1)/chi(2) for 5F-Trp in the lipid gel phase showed that the side chain alignment differs by up to 20 degrees from its known conformation in the liquid crystalline state. The sensitivity gain of (19)F-NMR and the reduction in the amount of material was at least 10-fold compared with previous (2)H-NMR studies on the same system and 100-fold compared with (15)N-NMR. PMID:12496101

  4. Red coralline algae assessed as marine pH proxies using 11B MAS NMR

    NASA Astrophysics Data System (ADS)

    Cusack, M.; Kamenos, N. A.; Rollion-Bard, C.; Tricot, G.

    2015-02-01

    Reconstructing pH from biogenic carbonates using boron isotopic compositions relies on the assumption that only borate, and no boric acid, is present. Red coralline algae are frequently used in palaeoenvironmental reconstruction due to their widespread distribution and regular banding frequency. Prior to undertaking pH reconstructions using red coralline algae we tested the boron composition of the red coralline alga Lithothamnion glaciale using high field NMR. In bulk analysed samples, thirty percent of boron was present as boric acid. We suggest that prior to reconstructing pH using coralline algae 1) species-specific boron compositions and 2) within-skeleton special distributions of boron are determined for multiple species. This will enable site selective boron analyses to be conducted validating coralline algae as palaeo-pH proxies based on boron isotopic compositions.

  5. Red coralline algae assessed as marine pH proxies using 11B MAS NMR.

    PubMed

    Cusack, M; Kamenos, N A; Rollion-Bard, C; Tricot, G

    2015-02-02

    Reconstructing pH from biogenic carbonates using boron isotopic compositions relies on the assumption that only borate, and no boric acid, is present. Red coralline algae are frequently used in palaeoenvironmental reconstruction due to their widespread distribution and regular banding frequency. Prior to undertaking pH reconstructions using red coralline algae we tested the boron composition of the red coralline alga Lithothamnion glaciale using high field NMR. In bulk analysed samples, thirty percent of boron was present as boric acid. We suggest that prior to reconstructing pH using coralline algae 1) species-specific boron compositions and 2) within-skeleton special distributions of boron are determined for multiple species. This will enable site selective boron analyses to be conducted validating coralline algae as palaeo-pH proxies based on boron isotopic compositions.

  6. Heating and temperature gradients of lipid bilayer samples induced by RF irradiation in MAS solid-state NMR experiments.

    PubMed

    Wang, Jing; Zhang, Zhengfeng; Zhao, Weijing; Wang, Liying; Yang, Jun

    2016-05-09

    The MAS solid-state NMR has been a powerful technique for studying membrane proteins within the native-like lipid bilayer environment. In general, RF irradiation in MAS NMR experiments can heat and potentially destroy expensive membrane protein samples. However, under practical MAS NMR experimental conditions, detailed characterization of RF heating effect of lipid bilayer samples is still lacking. Herein, using (1) H chemical shift of water for temperature calibration, we systematically study the dependence of RF heating on hydration levels and salt concentrations of three lipids in MAS NMR experiments. Under practical (1) H decoupling conditions used in biological MAS NMR experiments, three lipids show different dependence of RF heating on hydration levels as well as salt concentrations, which are closely associated with the properties of lipids. The maximum temperature elevation of about 10 °C is similar for the three lipids containing 200% hydration, which is much lower than that in static solid-state NMR experiments. The RF heating due to salt is observed to be less than that due to hydration, with a maximum temperature elevation of less than 4 °C in the hydrated samples containing 120 mmol l(-1) of salt. Upon RF irradiation, the temperature gradient across the sample is observed to be greatly increased up to 20 °C, as demonstrated by the remarkable broadening of (1) H signal of water. Based on detailed characterization of RF heating effect, we demonstrate that RF heating and temperature gradient can be significantly reduced by decreasing the hydration levels of lipid bilayer samples from 200% to 30%. Copyright © 2016 John Wiley & Sons, Ltd.

  7. Unraveling the complexity of protein backbone dynamics with combined (13)C and (15)N solid-state NMR relaxation measurements.

    PubMed

    Lamley, Jonathan M; Lougher, Matthew J; Sass, Hans Juergen; Rogowski, Marco; Grzesiek, Stephan; Lewandowski, Józef R

    2015-09-14

    Typically, protein dynamics involve a complex hierarchy of motions occurring on different time scales between conformations separated by a range of different energy barriers. NMR relaxation can in principle provide a site-specific picture of both the time scales and amplitudes of these motions, but independent relaxation rates sensitive to fluctuations in different time scale ranges are required to obtain a faithful representation of the underlying dynamic complexity. This is especially pertinent for relaxation measurements in the solid state, which report on dynamics in a broader window of time scales by more than 3 orders of magnitudes compared to solution NMR relaxation. To aid in unraveling the intricacies of biomolecular dynamics we introduce (13)C spin-lattice relaxation in the rotating frame (R1ρ) as a probe of backbone nanosecond-microsecond motions in proteins in the solid state. We present measurements of (13)C'R1ρ rates in fully protonated crystalline protein GB1 at 600 and 850 MHz (1)H Larmor frequencies and compare them to (13)C'R1, (15)N R1 and R1ρ measured under the same conditions. The addition of carbon relaxation data to the model free analysis of nitrogen relaxation data leads to greatly improved characterization of time scales of protein backbone motions, minimizing the occurrence of fitting artifacts that may be present when (15)N data is used alone. We also discuss how internal motions characterized by different time scales contribute to (15)N and (13)C relaxation rates in the solid state and solution state, leading to fundamental differences between them, as well as phenomena such as underestimation of picosecond-range motions in the solid state and nanosecond-range motions in solution.

  8. The topology of lysine-containing amphipathic peptides in bilayers by circular dichroism, solid-state NMR, and molecular modeling.

    PubMed Central

    Vogt, B; Ducarme, P; Schinzel, S; Brasseur, R; Bechinger, B

    2000-01-01

    In order to better understand the driving forces that determine the alignment of amphipathic helical polypeptides with respect to the surface of phospholipid bilayers, lysine-containing peptide sequences were designed, prepared by solid-phase chemical synthesis, and reconstituted into membranes. CD spectroscopy indicates that all peptides exhibit a high degree of helicity in the presence of SDS micelles or POPC small unilamellar vesicles. Proton-decoupled (31)P-NMR solid-state NMR spectroscopy demonstrates that in the presence of peptides liquid crystalline phosphatidylcholine membranes orient well along glass surfaces. The orientational distribution and dynamics of peptides labeled with (15)N at selected sites were investigated by proton-decoupled (15)N solid-state NMR spectroscopy. Polypeptides with a single lysine residue adopt a transmembrane orientation, thereby locating this polar amino acid within the core region of the bilayer. In contrast, peptides with > or = 3 lysines reside along the surface of the membrane. With 2 lysines in the center of an otherwise hydrophobic amino acid sequence the peptides assume a broad orientational distribution. The energy of lysine discharge, hydrophobic, polar, and all other interactions are estimated to quantitatively describe the polypeptide topologies observed. Furthermore, a molecular modeling algorithm based on the hydrophobicities of atoms in a continuous hydrophilic-hydrophobic-hydrophilic potential describes the experimentally observed peptide topologies well. PMID:11053137

  9. Combining solid-state and solution-state 31P NMR to study in vivo phosphorus metabolism.

    PubMed Central

    Cholli, A L; Yamane, T; Jelinski, L W

    1985-01-01

    Otherwise unavailable information concerning the distribution of phosphorylated compounds in biological systems is obtained by a combined solid-state/solution-state NMR approach, illustrated here for oocytes from Rana pipiens. General methodology is developed, and further extensions are proposed. The following conclusions pertain to the specific system under examination. (i) Nucleoside phosphates can be observed by magic-angle sample spinning of the lyophilized material. (ii) The solid-state NMR technique of dipolar decoupling provides no additional resolution of the phospholipid and phosphoprotein components of the yolk. However, cellular death produces sufficient pH changes to cause the phospholipid and protein phosphate peaks to become resolvable. The concentration of nucleoside phosphates also decreases. (iii) The phospholipid and phosphoprotein components are shown by computer simulation to be present in a ratio of 40:60, respectively. (iv) The amounts of inorganic phosphate, nucleoside phosphates, and sugar phosphates are determined by solution-state NMR observation of the perchloric acid extract of the oocytes. PMID:3871524

  10. Protein secondary structure of Green Lynx spider dragline silk investigated by solid-state NMR and X-ray diffraction.

    PubMed

    Xu, Dian; Shi, Xiangyan; Thompson, Forrest; Weber, Warner S; Mou, Qiushi; Yarger, Jeffery L

    2015-11-01

    In this study, the secondary structure of the major ampullate silk from Peucetia viridans (Green Lynx) spiders is characterized by X-ray diffraction and solid-state NMR spectroscopy. From X-ray diffraction measurement, β-sheet nanocrystallites were observed and found to be highly oriented along the fiber axis, with an orientational order, fc≈0.98. The size of the nanocrystallites was determined to be on average 2.5nm×3.3nm×3.8nm. Besides a prominent nanocrystalline region, a partially oriented amorphous region was also observed with an fa≈0.89. Two-dimensional (13)C-(13)C through-space and through-bond solid-state NMR experiments were employed to elucidate structure details of P. viridans silk proteins. It reveals that β-sheet nanocrystallites constitutes 40.0±1.2% of the protein and are dominated by alanine-rich repetitive motifs. Furthermore, based upon the NMR data, 18±1% of alanine, 60±2% glycine and 54±2% serine are incorporated into helical conformations. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Protein secondary structure of Green Lynx spider dragline silk investigated by solid-state NMR and X-ray diffraction

    PubMed Central

    Xu, Dian; Shi, Xiangyan; Thompson, Forrest; Weber, Warner S.; Mou, Qiushi; Yarger, Jeffery L

    2016-01-01

    In this study, the secondary structure of the major ampullate silk from Peucetia viridans (Green Lynx) spiders is characterized by X-ray diffraction and solid-state NMR spectroscopy. From X-ray diffraction measurement, β-sheet nanocrystallites were observed and found to be highly oriented along the fiber axis, with an orientational order, fc ≈ 0.98. The size of the nanocrystallites was determined to be on average 2.5 nm × 3.3 nm × 3.8 nm. Besides a prominent nanocrystalline region, a partially oriented amorphous region was also observed with an fa ≈ 0.89. Two-dimensional 13C–13C through-space and through-bond solid-state NMR experiments were employed to elucidate structure details of P. viridans silk proteins. It reveals that β-sheet nanocrystallites constitutes 40.0 ± 1.2% of the protein and are dominated by alanine-rich repetitive motifs. Furthermore, based upon the NMR data, 18 ± 1% of alanine, 60 ± 2% glycine and 54 ± 2% serine are incorporated into helical conformations. PMID:26226457

  12. Solid state {sup 31}P NMR study of phosphonate binding sites in guanidine-functionalized, molecular imprinted silica xerogels

    SciTech Connect

    Sasaki, D.Y.; Alam, T.D.

    2000-01-03

    Phosphonate binding sites in guanidine and ammonium surface-functionalized silica xerogels were prepared via the molecular imprinting technique and characterized using solid state {sup 31}P MAS NMR. One-point, two-point, and non-specific host-guest interactions between phenylphosphonic acid (PPA) and the functionalized gels were distinguished by characteristic chemical shifts of the observed absorption peaks. Using solid state as well as solution phase NMR analyses, absorptions observed at 15.5 ppm and 6.5 ppm were identified as resulting from the 1:1 (one-point) and 2:1 (two-point) guanidine to phosphonate interactions, respectively. Similar absorptions were observed with the ammonium functionalized gels. By examining the host-guest interactions within the gels, the efficiency of the molecular imprinting procedure with regard to the functional monomer-to-template interaction could be readily assessed. Template removal followed by substrate adsorption studies conducted on the guanidine functionalized gels provided a method to evaluate the binding characteristics of the receptor sites to a phosphonate substrate. During these experiments, {sup 29}Si and {sup 31}P MAS NMR acted as diagnostic monitors to identify structural changes occurring in the gel matrix and at the receptor site from solvent mediated processes.

  13. Bottom-up and top-down solid-state NMR approaches for bacterial biofilm matrix composition

    NASA Astrophysics Data System (ADS)

    Cegelski, Lynette

    2015-04-01

    The genomics and proteomics revolutions have been enormously successful in providing crucial "parts lists" for biological systems. Yet, formidable challenges exist in generating complete descriptions of how the parts function and assemble into macromolecular complexes and whole-cell assemblies. Bacterial biofilms are complex multicellular bacterial communities protected by a slime-like extracellular matrix that confers protection to environmental stress and enhances resistance to antibiotics and host defenses. As a non-crystalline, insoluble, heterogeneous assembly, the biofilm extracellular matrix poses a challenge to compositional analysis by conventional methods. In this perspective, bottom-up and top-down solid-state NMR approaches are described for defining chemical composition in complex macrosystems. The "sum-of-the-parts" bottom-up approach was introduced to examine the amyloid-integrated biofilms formed by Escherichia coli and permitted the first determination of the composition of the intact extracellular matrix from a bacterial biofilm. An alternative top-down approach was developed to define composition in Vibrio cholerae biofilms and relied on an extensive panel of NMR measurements to tease out specific carbon pools from a single sample of the intact extracellular matrix. These two approaches are widely applicable to other heterogeneous assemblies. For bacterial biofilms, quantitative parameters of matrix composition are needed to understand how biofilms are assembled, to improve the development of biofilm inhibitors, and to dissect inhibitor modes of action. Solid-state NMR approaches will also be invaluable in obtaining parameters of matrix architecture.

  14. Structure of the coat protein in fd filamentous bacteriophage particles determined by solid-state NMR spectroscopy

    PubMed Central

    Zeri, Ana Carolina; Mesleh, Michael F.; Nevzorov, Alexander A.; Opella, Stanley J.

    2003-01-01

    The atomic resolution structure of fd coat protein determined by solid-state NMR spectroscopy of magnetically aligned filamentous bacteriophage particles differs from that previously determined by x-ray fiber diffraction. Most notably, the 50-residue protein is not a single curved helix, but rather is a nearly ideal straight helix between residues 7 and 38, where there is a distinct kink, and then a straight helix with a different orientation between residues 39 and 49. Residues 1–5 have been shown to be mobile and unstructured, and proline 6 terminates the helix. The structure of the coat protein in virus particles, in combination with the structure of the membrane-bound form of the same protein in bilayers, also recently determined by solid-state NMR spectroscopy, provides insight into the viral assembly process. In addition to their roles in molecular biology and biotechnology, the filamentous bacteriophages continue to serve as model systems for the development of experimental methods for determining the structures of proteins in biological supramolecular assemblies. New NMR results include the complete sequential assignment of the two-dimensional polarization inversion spin-exchange at the magic angle spectrum of a uniformly 15N-labeled 50-residue protein in a 1.6 × 107 Da particle in solution, and the calculation of the three-dimensional structure of the protein from orientational restraints with an accuracy equivalent to an rms deviation of ≈1Å. PMID:12750469

  15. Solid-State (17)O NMR of Oxygen-Nitrogen Singly Bonded Compounds: Hydroxylammonium Chloride and Sodium Trioxodinitrate (Angeli's Salt).

    PubMed

    Lu, Jiasheng; Kong, Xianqi; Terskikh, Victor; Wu, Gang

    2015-07-23

    We report a solid-state NMR study of (17)O-labeled hydroxylammonium chloride ([H(17)O-NH3]Cl) and sodium trioxodinitrate monohydrate (Na2[(17)ONNO2]·H2O, Angeli's salt). The common feature in these two compounds is that they both contain oxygen atoms that are singly bonded to nitrogen. For this class of oxygen-containing functional groups, there is very limited solid-state (17)O NMR data in the literature. In this work, we experimentally measured the (17)O chemical shift and quadrupolar coupling tensors. With the aid of plane-wave DFT computation, the (17)O NMR tensor orientations were determined in the molecular frame of reference. We found that the characteristic feature of an O-N single bond is that the (17)O nucleus exhibits a large quadrupolar coupling constant (13-15 MHz) but a rather small chemical shift anisotropy (100-250 ppm), in sharp contrast with the nitroso (O═N) functional group for which both quantities are very large (e.g., 16 MHz and 3000 ppm, respectively).

  16. EASY-GOING deconvolution: combining accurate simulation and evolutionary algorithms for fast deconvolution of solid-state quadrupolar NMR spectra.

    PubMed

    Grimminck, Dennis L A G; Polman, Ben J W; Kentgens, Arno P M; Meerts, W Leo

    2011-08-01

    A fast and accurate fit program is presented for deconvolution of one-dimensional solid-state quadrupolar NMR spectra of powdered materials. Computational costs of the synthesis of theoretical spectra are reduced by the use of libraries containing simulated time/frequency domain data. These libraries are calculated once and with the use of second-party simulation software readily available in the NMR community, to ensure a maximum flexibility and accuracy with respect to experimental conditions. EASY-GOING deconvolution (EGdeconv) is equipped with evolutionary algorithms that provide robust many-parameter fitting and offers efficient parallellised computing. The program supports quantification of relative chemical site abundances and (dis)order in the solid-state by incorporation of (extended) Czjzek and order parameter models. To illustrate EGdeconv's current capabilities, we provide three case studies. Given the program's simple concept it allows a straightforward extension to include other NMR interactions. The program is available as is for 64-bit Linux operating systems. Copyright © 2011 Elsevier Inc. All rights reserved.

  17. Analysis of Molecular Orientation in Organic Semiconducting Thin Films Using Static Dynamic Nuclear Polarization Enhanced Solid-State NMR.

    PubMed

    Suzuki, Katsuaki; Kubo, Shosei; Aussenac, Fabien; Engelke, Frank; Fukushima, Tatsuya; Kaji, Hironori

    2017-10-09

    Molecular orientation in amorphous organic semiconducting thin film devices is an important issue affecting device performances. However, to date it has not been possible to analyze the "distribution" of the orientations. Although solid-state NMR (ssNMR) can provide information on the distribution of molecular orientations, the technique is limited because of the small amounts of sample in the devices and the low sensitivity of ssNMR. Here, we report the first application of dynamic nuclear polarization enhanced ssNMR (DNP-ssNMR) to orientational analysis of amorphous phenyldi(pyren-1-yl)phosphine oxide (POPy2). The 31P DNP-ssNMR spectra exhibited a sufficient signal-to-noise ratio to quantify the distribution of molecular orientations in amorphous films: the P=O axis of the vacuum-deposited and drop-cast POPy2 shows anisotropic and isotropic distribution, respectively. The different molecular orientations reflect the molecular origin of the different charge transport behaviors. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Ab Initio Quality NMR Parameters in Solid-State Materials Using a High-Dimensional Neural-Network Representation.

    PubMed

    Cuny, Jérôme; Xie, Yu; Pickard, Chris J; Hassanali, Ali A

    2016-02-09

    Nuclear magnetic resonance (NMR) spectroscopy is one of the most powerful experimental tools to probe the local atomic order of a wide range of solid-state compounds. However, due to the complexity of the related spectra, in particular for amorphous materials, their interpretation in terms of structural information is often challenging. These difficulties can be overcome by combining molecular dynamics simulations to generate realistic structural models with an ab initio evaluation of the corresponding chemical shift and quadrupolar coupling tensors. However, due to computational constraints, this approach is limited to relatively small system sizes which, for amorphous materials, prevents an adequate statistical sampling of the distribution of the local environments that is required to quantitatively describe the system. In this work, we present an approach to efficiently and accurately predict the NMR parameters of very large systems. This is achieved by using a high-dimensional neural-network representation of NMR parameters that are calculated using an ab initio formalism. To illustrate the potential of this approach, we applied this neural-network NMR (NN-NMR) method on the (17)O and (29)Si quadrupolar coupling and chemical shift parameters of various crystalline silica polymorphs and silica glasses. This approach is, in principal, general and has the potential to be applied to predict the NMR properties of various materials.

  19. Proton clouds to measure long-range contacts between nonexchangeable side chain protons in solid-state NMR.

    PubMed

    Sinnige, Tessa; Daniëls, Mark; Baldus, Marc; Weingarth, Markus

    2014-03-26

    We show that selective labeling of proteins with protonated amino acids embedded in a perdeuterated matrix, dubbed 'proton clouds', provides general access to long-range contacts between nonexchangeable side chain protons in proton-detected solid-state NMR, which is important to study protein tertiary structure. Proton-cloud labeling significantly improves spectral resolution by simultaneously reducing proton line width and spectral crowding despite a high local proton density in clouds. The approach is amenable to almost all canonical amino acids. Our method is demonstrated on ubiquitin and the β-barrel membrane protein BamA.

  20. On the structure of amorphous calcium carbonate--a detailed study by solid-state NMR spectroscopy.

    PubMed

    Nebel, Holger; Neumann, Markus; Mayer, Christian; Epple, Matthias

    2008-09-01

    The calcium carbonate phases calcite, aragonite, vaterite, monohydrocalcite (calcium carbonate monohydrate), and ikaite (calcium carbonate hexahydrate) were studied by solid-state NMR spectroscopy ( (1)H and (13)C). Further model compounds were sodium hydrogencarbonate, potassium hydrogencarbonate, and calcium hydroxide. With the help of these data, the structure of synthetically prepared additive-free amorphous calcium carbonate (ACC) was analyzed. ACC contains molecular water (as H 2O), a small amount of mobile hydroxide, and no hydrogencarbonate. This supports the concept of ACC as a transient precursor in the formation of calcium carbonate biominerals.

  1. Use of microcoil probehead for determination of the structure of oriented silk fibers by solid-state NMR.

    PubMed

    Yamauchi, K; Imada, T; Asakura, T

    2005-09-22

    A microcoil probehead for solid-state NMR was developed with a two-channel radio-frequency circuit, and 13C observation with a proton-decoupling probehead was performed to obtain information on the distribution of the orientation of silk fibroin molecules in the fiber. The coil (1 mm (diameter) x 5 mm (length)) of the probehead was placed at the angles 90 degrees and 30 degrees , relative to the static magnetic field. Only 70 mug of [1-13C]Gly silk fibroin fiber was used in a magnet of 9.4 T (400 MHz for proton channel).

  2. Solid-State ¹⁷O NMR studies of organic and biological molecules: Recent advances and future directions.

    PubMed

    Wu, Gang

    2016-02-01

    This Trends article highlights the recent advances published between 2012 and 2015 in solid-state (17)O NMR for organic and biological molecules. New developments in the following areas are described: (1) new oxygen-containing functional groups, (2) metal organic frameworks, (3) pharmaceuticals, (4) probing molecular motion in organic solids, (5) dynamic nuclear polarization, and (6) paramagnetic coordination compounds. For each of these areas, the author offers his personal views on important problems to be solved and possible future directions. Copyright © 2015 Elsevier Inc. All rights reserved.

  3. 1H-detected solid-state NMR of proteins entrapped in bioinspired silica: a new tool for biomaterials characterization

    PubMed Central

    Ravera, Enrico; Cerofolini, Linda; Martelli, Tommaso; Louka, Alexandra; Fragai, Marco; Luchinat, Claudio

    2016-01-01

    Proton-detection in solid-state NMR, enabled by high magnetic fields (>18 T) and fast magic angle spinning (>50 kHz), allows for the acquisition of traditional 1H-15N experiments on systems that are too big to be observed in solution. Among those, proteins entrapped in a bioinspired silica matrix are an attractive target that is receiving a large share of attention. We demonstrate that 1H-detected SSNMR provides a novel approach to the rapid assessment of structural integrity in proteins entrapped in bioinspired silica. PMID:27279168

  4. Structure determination of membrane proteins in their native phospholipid bilayer environment by rotationally aligned solid-state NMR spectroscopy.

    PubMed

    Opella, Stanley J

    2013-09-17

    One of the most important topics in experimental structural biology is determining the structures of membrane proteins. These structures represent one-third of all of the information expressed from a genome, distinguished by their locations within the phospholipid bilayer of cells, organelles, or enveloped viruses. Their highly hydrophobic nature and insolubility in aqueous media means that they require an amphipathic environment. They have unique functions in transport, catalysis, channel formation, and signaling. Researchers are particularly interested in G-protein coupled receptors (GPCRs) because they modulate many biological processes, and about half of the approximately 800 of these proteins within the human genome are or can be turned into drug receptors that affect a wide range of diseases. Because of experimental difficulties, researchers have studied membrane proteins using a wide variety of artificial media that mimic membranes, such as mixed organic solvents or detergents. More sophisticated mimics include bilayer discs (bicelles) and the lipid cubic phase (LCP), but both of these contain a very large detergent component, which can disrupt the stability and function of membrane proteins. To have confidence in the resulting structures and their biological functions and to avoid disrupting these delicate proteins, the structures of membrane proteins should be determined in their native environment of liquid crystalline phospholipid bilayers under physiological conditions. This Account describes a recently developed general method for determining the structures of unmodified membrane proteins in phospholipid bilayers by solid-state NMR spectroscopy. Because it relies on the natural, rapid rotational diffusion of these proteins about the bilayer normal, this method is referred to as rotationally aligned (RA) solid-state NMR. This technique elaborates on oriented sample (OS) solid-state NMR, its complementary predecessor. These methods exploit the power of

  5. Dipolar Assisted Assignment Protocol (DAAP) for MAS solid-state NMR of rotationally aligned membrane proteins in phospholipid bilayers

    NASA Astrophysics Data System (ADS)

    Das, Bibhuti B.; Zhang, Hua; Opella, Stanley J.

    2014-05-01

    A method for making resonance assignments in magic angle spinning solid-state NMR spectra of membrane proteins that utilizes the range of heteronuclear dipolar coupling frequencies in combination with conventional chemical shift based assignment methods is demonstrated. The Dipolar Assisted Assignment Protocol (DAAP) takes advantage of the rotational alignment of the membrane proteins in liquid crystalline phospholipid bilayers. Improved resolution is obtained by combining the magnetically inequivalent heteronuclear dipolar frequencies with isotropic chemical shift frequencies. Spectra with both dipolar and chemical shift frequency axes assist with resonance assignments. DAAP can be readily extended to three- and four-dimensional experiments and to include both backbone and side chain sites in proteins.

  6. 1H-detected solid-state NMR of proteins entrapped in bioinspired silica: a new tool for biomaterials characterization

    NASA Astrophysics Data System (ADS)

    Ravera, Enrico; Cerofolini, Linda; Martelli, Tommaso; Louka, Alexandra; Fragai, Marco; Luchinat, Claudio

    2016-06-01

    Proton-detection in solid-state NMR, enabled by high magnetic fields (>18 T) and fast magic angle spinning (>50 kHz), allows for the acquisition of traditional 1H-15N experiments on systems that are too big to be observed in solution. Among those, proteins entrapped in a bioinspired silica matrix are an attractive target that is receiving a large share of attention. We demonstrate that 1H-detected SSNMR provides a novel approach to the rapid assessment of structural integrity in proteins entrapped in bioinspired silica.

  7. Sensitivity Enhanced Heteronuclear Correlation Spectroscopy in Multidimensional Solid-State NMR of Oriented Systems via Chemical Shift Coherences

    PubMed Central

    Gopinath, T.; Traaseth, Nathaniel J.; Mote, Kaustubh; Veglia, Gianluigi

    2011-01-01

    We present new sensitivity enhanced schemes for heteronuclear correlation spectroscopy (HETCOR) in solid-state NMR of oriented systems. These new schemes will enhance the sensitivity of the HETCOR by 40% for the two dimensional experiments (SE-HETCOR) and up to 180% for the 3D HETCOR- separated local field version (SE-PISEMAI-HETCOR). The signal enhancement is demonstrated for a single crystal of 15N N-acetylleucine and the integral membrane protein sarcolipin oriented in lipid bicelles. These new methods will significantly reduce the time needed to acquire multidimensional experiments for membrane proteins oriented in magnetically or mechanically aligned lipid bilayers as well as liquid crystalline materials. PMID:20345172

  8. Sensitivity enhanced heteronuclear correlation spectroscopy in multidimensional solid-state NMR of oriented systems via chemical shift coherences.

    PubMed

    Gopinath, T; Traaseth, Nathaniel J; Mote, Kaustubh; Veglia, Gianluigi

    2010-04-21

    We present new sensitivity enhanced schemes for heteronuclear correlation spectroscopy (HETCOR) in solid-state NMR of oriented systems. These schemes will enhance the sensitivity of the HETCOR by 40% for the two-dimensional experiments (SE-HETCOR) and up to 180% for the 3D HETCOR-separated local field version (SE-PISEMAI-HETCOR). The signal enhancement is demonstrated for a single crystal of ((15)N)N-acetylleucine and the integral membrane protein sarcolipin oriented in lipid bicelles. These methods will significantly reduce the time needed to acquire multidimensional experiments for membrane proteins oriented in magnetically or mechanically aligned lipid bilayers as well as liquid crystalline materials.

  9. Probing conformational disorder in neurotensin by two-dimensional solid-state NMR and comparison to molecular dynamics simulations.

    PubMed

    Heise, Henrike; Luca, Sorin; de Groot, Bert L; Grubmüller, Helmut; Baldus, Marc

    2005-09-01

    An approach is introduced to characterize conformational ensembles of intrinsically unstructured peptides on the atomic level using two-dimensional solid-state NMR data and their combination with molecular dynamics simulations. For neurotensin, a peptide that binds with high affinity to a G-protein coupled receptor, this method permits the investigation of the changes in conformational preferences of a neurotransmitter transferred from a frozen aqueous solution via a lipid model phase to the receptor-bound form. The results speak against a conformational pre-organization of the ligand in detergents in which the receptor has been shown to be functional. Further extensions to the study of protein folding are possible.

  10. Investigation of the interface in silica-encapsulated liposomes by combining solid state NMR and first principles calculations.

    PubMed

    Folliet, Nicolas; Roiland, Claire; Bégu, Sylvie; Aubert, Anne; Mineva, Tzonka; Goursot, Annick; Selvaraj, Kaliaperumal; Duma, Luminita; Tielens, Frederik; Mauri, Francesco; Laurent, Guillaume; Bonhomme, Christian; Gervais, Christel; Babonneau, Florence; Azaïs, Thierry

    2011-10-26

    In the context of nanomedicine, liposils (liposomes and silica) have a strong potential for drug storage and release schemes: such materials combine the intrinsic properties of liposome (encapsulation) and silica (increased rigidity, protective coating, pH degradability). In this work, an original approach combining solid state NMR, molecular dynamics, first principles geometry optimization, and NMR parameters calculation allows the building of a precise representation of the organic/inorganic interface in liposils. {(1)H-(29)Si}(1)H and {(1)H-(31)P}(1)H Double Cross-Polarization (CP) MAS NMR experiments were implemented in order to explore the proton chemical environments around the silica and the phospholipids, respectively. Using VASP (Vienna Ab Initio Simulation Package), DFT calculations including molecular dynamics, and geometry optimization lead to the determination of energetically favorable configurations of a DPPC (dipalmitoylphosphatidylcholine) headgroup adsorbed onto a hydroxylated silica surface that corresponds to a realistic model of an amorphous silica slab. These data combined with first principles NMR parameters calculations by GIPAW (Gauge Included Projected Augmented Wave) show that the phosphate moieties are not directly interacting with silanols. The stabilization of the interface is achieved through the presence of water molecules located in-between the head groups of the phospholipids and the silica surface forming an interfacial H-bonded water layer. A detailed study of the (31)P chemical shift anisotropy (CSA) parameters allows us to interpret the local dynamics of DPPC in liposils. Finally, the VASP/solid state NMR/GIPAW combined approach can be extended to a large variety of organic-inorganic hybrid interfaces.

  11. Characterization of Non-Innocent Metal Complexes Using Solid-State NMR Spectroscopy: o-Dioxolene Vanadium Complexes

    PubMed Central

    Chatterjee, Pabitra B.; Goncharov-Zapata, Olga; Quinn, Laurence L.; Hou, Guangjin; Hamaed, Hiyam; Schurko, Robert W.; Polenova, Tatyana; Crans, Debbie C.

    2012-01-01

    51V solid-state NMR (SSNMR) studies of a series of non-innocent vanadium(V) catechol complexes have been conducted to evaluate the possibility that 51V NMR observables, quadrupolar and chemical shift anisotropies, and electronic structures of such compounds can be used to characterize these compounds. The vanadium(V) catechol complexes described in these studies have relatively small quadrupolar coupling constants, which cover a surprisingly small range from 3.4 to 4.2 MHz. On the other hand, isotropic 51V NMR chemical shifts cover a wide range from −200 ppm to 400 ppm in solution and from −219 to 530 ppm in the solid state. A linear correlation of 51V NMR isotropic solution and solid-state chemical shifts of complexes containing non-innocent ligands is observed. These experimental results provide the information needed for the application of 51V SSNMR spectroscopy in characterizing the electronic properties of a wide variety of vanadium-containing systems, and in particular those containing non-innocent ligands and that have chemical shifts outside the populated range of −300 ppm to −700 ppm. The studies presented in this report demonstrate that the small quadrupolar couplings covering a narrow range of values reflect the symmetric electronic charge distribution, which is also similar across these complexes. These quadrupolar interaction parameters alone are not sufficient to capture the rich electronic structure of these complexes. In contrast, the chemical shift anisotropy tensor elements accessible from 51V SSNMR experiments are a highly sensitive probe of subtle differences in electronic distribution and orbital occupancy in these compounds. Quantum chemical (DFT) calculations of NMR parameters for [VO(hshed)(Cat)] yield 51V CSA tensor in reasonable agreement with the experimental results, but surprisingly, the calculated quadrupolar coupling constant is significantly greater than the experimental value. The studies demonstrate that substitution of the

  12. Medium-Range Structural Organization of Phosphorus-Bearing Borosilicate Glasses Revealed by Advanced Solid-State NMR Experiments and MD Simulations: Consequences of B/Si Substitutions.

    PubMed

    Yu, Yang; Stevensson, Baltzar; Edén, Mattias

    2017-10-05

    The short and intermediate range structures of a large series of bioactive borophosphosilicate (BPS) glasses were probed by solid-state nuclear magnetic resonance (NMR) spectroscopy and atomistic molecular dynamics (MD) simulations. Two BPS glass series were designed by gradually substituting SiO2 by B2O3 in the respective phosphosilicate base compositions 24.1Na2O-23.3CaO-48.6SiO2-4.0P2O5 ("S49") and 24.6Na2O-26.7CaO-46.1SiO2-2.6P2O5 ("S46"), the latter constituting the "45S5 Bioglass" utilized for bone grafting applications. The BPS glass networks are built by interconnected SiO4, BO4, and BO3 moieties, whereas P exists mainly as orthophosphate anions, except for a minor network-associated portion involving P-O-Si and P-O-B([4]) motifs, whose populations were estimated by heteronuclear (31)P{(11)B} NMR experimentation. The high Na(+)/Ca(2+) contents give fragmented glass networks with large amounts of nonbridging oxygen (NBO) anions. The MD-generated glass models reveal an increasing propensity for NBO accommodation among the network units according to BO4 < SiO4 < BO3 ≪ PO4. The BO4/BO3 intermixing was examined by double-quantum-single-quantum correlation (11)B NMR experiments, which evidenced the presence of all three BO3-BO3, BO3-BO4, and BO4-BO4 connectivities, with B([3])-O-B([4]) bridges dominating. Notwithstanding that B([4])-O-B([4]) linkages are disfavored, both NMR spectroscopy and MD simulations established their presence in these modifier-rich BPS glasses, along with non-negligible B([4])-NBO contacts, at odds with the conventional structural view of borosilicate glasses. We discuss the relative propensities for intermixing of the Si/B/P network formers. Despite the absence of pronounced preferences for Si-O-Si bond formation, the glass models manifest subtle subnanometer-sized structural inhomogeneities, where SiO4 tetrahedra tend to self-associate into small chain/ring motifs embedded in BO3/BO4-dominated domains.

  13. Intermolecular packing and alignment in an ordered beta-hairpin antimicrobial peptide aggregate from 2D solid-state NMR.

    PubMed

    Tang, Ming; Waring, Alan J; Hong, Mei

    2005-10-12

    The aggregation and packing of a membrane-disruptive beta-hairpin antimicrobial peptide, protegrin-1 (PG-1), in the solid state are investigated to understand its oligomerization and hydrogen-bonding propensity. Incubation of PG-1 in phosphate buffer saline produced well-ordered nanometer-scale aggregates, as indicated by 13C and 15N NMR line widths, chemical shifts, and electron microscopy. Two-dimensional 13C and 1H spin diffusion experiments using C-terminus strand and N-terminus strand labeled peptides indicate that the beta-hairpin molecules in these ordered aggregates are oriented parallel to each other with like strands lining the intermolecular interface. In comparison, disordered and lyophilized peptide samples are randomly packed with both parallel and antiparallel alignments. The PG-1 aggregates show significant immobilization of the Phe ring near the beta-turn, further supporting the structural ordering. The intermolecular packing of PG-1 found in the solid state is consistent with its oligomerization in lipid bilayers. This solid-state aggregation approach may be useful for determining the quaternary structure of peptides in general and for gaining insights into the oligomerization of antimicrobial peptides in lipid bilayers in particular.

  14. Dynamic nuclear polarization solid-state NMR in heterogeneous catalysis research

    SciTech Connect

    Kobayashi, Takeshi; Perras, Frédéric A.; Slowing, Igor I.; Sadow, Aaron D.; Pruski, Marek

    2015-10-20

    In this study, a revolution in solid-state nuclear magnetic resonance (SSNMR) spectroscopy is taking place, attributable to the rapid development of high-field dynamic nuclear polarization (DNP), a technique yielding sensitivity improvements of 2–3 orders of magnitude. This higher sensitivity in SSNMR has already impacted materials research, and the implications of new methods on catalytic sciences are expected to be profound.

  15. Dynamic nuclear polarization solid-state NMR in heterogeneous catalysis research

    DOE PAGES

    Kobayashi, Takeshi; Perras, Frédéric A.; Slowing, Igor I.; ...

    2015-10-20

    In this study, a revolution in solid-state nuclear magnetic resonance (SSNMR) spectroscopy is taking place, attributable to the rapid development of high-field dynamic nuclear polarization (DNP), a technique yielding sensitivity improvements of 2–3 orders of magnitude. This higher sensitivity in SSNMR has already impacted materials research, and the implications of new methods on catalytic sciences are expected to be profound.

  16. NMR crystallography: structure and properties of materials from solid-state nuclear magnetic resonance observables.

    PubMed

    Bryce, David L

    2017-07-01

    This topical review provides a brief overview of recent developments in NMR crystallography and related NMR approaches to studying the properties of molecular and ionic solids. Areas of complementarity with diffraction-based methods are underscored. These include the study of disordered systems, of dynamic systems, and other selected examples where NMR can provide unique insights. Highlights from the literature as well as recent work from my own group are discussed.

  17. Toward a structure determination method for biomineral-associated protein using combined solid- state NMR and computational structure prediction.

    PubMed

    Masica, David L; Ash, Jason T; Ndao, Moise; Drobny, Gary P; Gray, Jeffrey J

    2010-12-08

    Protein-biomineral interactions are paramount to materials production in biology, including the mineral phase of hard tissue. Unfortunately, the structure of biomineral-associated proteins cannot be determined by X-ray crystallography or solution nuclear magnetic resonance (NMR). Here we report a method for determining the structure of biomineral-associated proteins. The method combines solid-state NMR (ssNMR) and ssNMR-biased computational structure prediction. In addition, the algorithm is able to identify lattice geometries most compatible with ssNMR constraints, representing a quantitative, novel method for investigating crystal-face binding specificity. We use this method to determine most of the structure of human salivary statherin interacting with the mineral phase of tooth enamel. Computation and experiment converge on an ensemble of related structures and identify preferential binding at three crystal surfaces. The work represents a significant advance toward determining structure of biomineral-adsorbed protein using experimentally biased structure prediction. This method is generally applicable to proteins that can be chemically synthesized. Copyright © 2010 Elsevier Ltd. All rights reserved.

  18. Probing the interaction of U(vi) with phosphonate-functionalized mesoporous silica using solid-state NMR spectroscopy.

    PubMed

    Uribe, Eva C; Mason, Harris E; Shusterman, Jennifer A; Bruchet, Anthony; Nitsche, Heino

    2016-06-21

    The fundamental interaction of U(vi) with diethylphosphatoethyl triethoxysilane functionalized SBA-15 mesoporous silica is studied by macroscopic batch experiments and solid-state NMR spectroscopy. DPTS-functionalized silica has been shown to extract U(vi) from nitric acid solutions at or above pH 3. Extraction is dependent on pH and ionic strength. Single-pulse (31)P NMR on U(vi) contacted samples revealed that U(vi) only interacts with a fraction of the ligands present on the surface. At pH 4 the U(vi) extraction capacity of the material is limited to 27-37% of the theoretical capacity, based on ligand loading. We combined single pulse (31)P NMR on U(vi)-contacted samples with batch studies to measure a ligand-to-metal ratio of approximately 2 : 1 at pH 3 and 4. Batch studies and cross-polarization NMR measurements reveal that U(vi) binds to deprotonated phosphonate and/or silanol sites. We use (31)P-(31)P DQ-DRENAR NMR studies to compare the average dipolar coupling between phosphorus spins for both U(vi)-complexed and non-complexed ligand environments. These measurements reveal that U(vi) extraction is not limited by inadequate surface distribution of ligands, but rather by low stability of the surface phosphonate complex.

  19. Probing the interaction of U(VI) with phosphonate-functionalized mesoporous silica using solid-state NMR spectroscopy

    DOE PAGES

    Uribe, Eva C.; Mason, Harris E.; Shusterman, Jennifer A.; ...

    2016-05-30

    The fundamental interaction of U(VI) with diethylphosphatoethyl triethoxysilane functionalized SBA-15 mesoporous silica is studied by macroscopic batch experiments and solid-state NMR spectroscopy. DPTS-functionalized silica has been shown to extract U(VI) from nitric acid solutions at or above pH 3. Extraction is dependent on pH and ionic strength. Single-pulse 31P NMR on U(VI) contacted samples revealed that U(VI)only interacts with a fraction of the ligands present on the surface. At pH 4 the U(VI) extraction capacity of the material is limited to 27–37% of the theoretical capacity, based on ligand loading. We combined single pulse 31P NMR on U(VI)-contacted samples withmore » batch studies to measure a ligand-to-metal ratio of approximately 2 : 1 at pH 3 and 4. Batch studies and cross-polarization NMR measurements reveal that U(VI) binds to deprotonated phosphonate and/or silanol sites. We use 31P–31P DQ-DRENAR NMR studies to compare the average dipolar coupling between phosphorus spins for both U(VI)-complexed and non-complexed ligand environments. Furthermore, these measurements reveal that U(VI) extraction is not limited by inadequate surface distribution of ligands, but rather by low stability of the surface phosphonate complex.« less

  20. Crystallinity and compositional changes in carbonated apatites: Evidence from (31)P solid-state NMR, Raman, and AFM analysis.

    PubMed

    McElderry, John-David P; Zhu, Peizhi; Mroue, Kamal H; Xu, Jiadi; Pavan, Barbara; Fang, Ming; Zhao, Guisheng; McNerny, Erin; Kohn, David H; Franceschi, Renny T; Holl, Mark M Banaszak; Tecklenburg, Mary M J; Ramamoorthy, Ayyalusamy; Morris, Michael D

    2013-10-01

    Solid-state (magic-angle spinning) NMR spectroscopy is a useful tool for obtaining structural information on bone organic and mineral components and synthetic model minerals at the atomic-level. Raman and (31)P NMR spectral parameters were investigated in a series of synthetic B-type carbonated apatites (CAps). Inverse (31)P NMR linewidth and inverse Raman PO4(3-) ν1 bandwidth were both correlated with powder XRD c-axis crystallinity over the 0.3-10.3 wt% CO3(2-) range investigated. Comparison with bone powder crystallinities showed agreement with values predicted by NMR and Raman calibration curves. Carbonate content was divided into two domains by the (31)P NMR chemical shift frequency and the Raman phosphate ν1 band position. These parameters remain stable except for an abrupt transition at 6.5 wt% carbonate, a composition which corresponds to an average of one carbonate per unit cell. This near-binary distribution of spectroscopic properties was also found in AFM-measured particle sizes and Ca/P molar ratios by elemental analysis. We propose that this transition differentiates between two charge-balancing ion-loss mechanisms as measured by Ca/P ratios. These results define a criterion for spectroscopic characterization of B-type carbonate substitution in apatitic minerals.

  1. Crystallinity and compositional changes in carbonated apatites: Evidence from 31P solid-state NMR, Raman, and AFM analysis

    PubMed Central

    McElderry, John-David P.; Zhu, Peizhi; Mroue, Kamal H.; Xu, Jiadi; Pavan, Barbara; Fang, Ming; Zhao, Guisheng; McNerny, Erin; Kohn, David H.; Franceschi, Renny T.; Holl, Mark M. Banaszak; Tecklenburg, Mary M.J.; Ramamoorthy, Ayyalusamy; Morris, Michael D.

    2013-01-01

    Solid-state (magic-angle spinning) NMR spectroscopy is a useful tool for obtaining structural information on bone organic and mineral components and synthetic model minerals at the atomic-level. Raman and 31P NMR spectral parameters were investigated in a series of synthetic B-type carbonated apatites (CAps). Inverse 31P NMR linewidth and inverse Raman PO43− ν1 bandwidth were both correlated with powder XRD c-axis crystallinity over the 0.3–10.3 wt% CO32− range investigated. Comparison with bone powder crystallinities showed agreement with values predicted by NMR and Raman calibration curves. Carbonate content was divided into two domains by the 31P NMR chemical shift frequency and the Raman phosphate ν1 band position. These parameters remain stable except for an abrupt transition at 6.5 wt% carbonate, a composition which corresponds to an average of one carbonate per unit cell. This near-binary distribution of spectroscopic properties was also found in AFM-measured particle sizes and Ca/P molar ratios by elemental analysis. We propose that this transition differentiates between two charge-balancing ion-loss mechanisms as measured by Ca/P ratios. These results define a criterion for spectroscopic characterization of B-type carbonate substitution in apatitic minerals. PMID:24273344

  2. Structural Evolution and Li Dynamics in Nanophase Li3PS4 by Solid-State and Pulsed Field Gradient NMR

    SciTech Connect

    Gobet, Mallory; Greenbaum, Steve; Sahu, Gayatri; Liang, Chengdu

    2014-01-01

    The ceramic lithium ion conductor -Li3PS4 has a disordered and nanoporous structure that leads to an enhancement in ionic conductivity by some three orders of magnitude compared to the crystalline phase. The phase is prepared by thermal treatment of an inorganic-organic complex based on Li3PS4 and THF. Multinuclear (1H, 6,7Li, 31P) solid state NMR spectroscopy is used to characterize the structural phase evolution of the starting material at various steps in the thermal treatment. The phase formed after high temperature treatment is recognized as spectroscopically distinct from the bulk -Li3PS4 compound. Also formed is an amorphous lithium thiophosphate phase that is metastable as verified by annealing over an extended period. Lithium ion self-diffusion coefficients are measurable by standard pulsed gradient NMR methods at 100oC and with values consistent with the high ionic conductivity previously reported for this material.

  3. Characterization by solid-state NMR and selective dissolution techniques of anhydrous and hydrated CEM V cement pastes

    SciTech Connect

    Brunet, F.; Charpentier, T.; Chao, C.N.; Peycelon, H.; Nonat, A.

    2010-02-15

    The long term behaviour of cement based materials is strongly dependent on the paste microstructure and also on the internal chemistry. A CEM V blended cement containing pulverised fly ash (PFA) and blastfurnace slag (BFS) has been studied in order to understand hydration processes which influence the paste microstructure. Solid-state NMR spectroscopy with complementary X-ray diffraction analysis and selective dissolution techniques have been used for the characterization of the various phases (C{sub 3}S, C{sub 2}S, C{sub 3}A and C{sub 4}AF) of the clinker and additives and then for estimation of the degree of hydration of these same phases. Their quantification after simulation of experimental {sup 29}Si and {sup 27}Al MAS NMR spectra has allowed us to follow the hydration of recent (28 days) and old (10 years) samples that constitutes a basis of experimental data for the prediction of hydration model.

  4. Light activation of rhodopsin: insights from molecular dynamics simulations guided by solid-state NMR distance restraints

    PubMed Central

    Hornak, Viktor; Ahuja, Shivani; Eilers, Markus; Goncalves, Joseph A.; Sheves, Mordechai; Reeves, Philip J.; Smith, Steven O.

    2009-01-01

    Structural restraints provided by solid-state NMR measurements of the metarhodopsin II intermediate are combined with molecular dynamics simulations to help visualize the structural changes in the light activation of rhodopsin. Since the time scale for the formation of the metarhodopsin II intermediate (> 1 ms) is beyond that readily accessible by molecular dynamics, we use NMR distance restraints derived from 13C dipolar recoupling measurements to guide the simulations. The simulations yield a working model for how photoisomerization of the 11-cis retinylidene chromophore bound within the interior of rhodopsin is coupled to transmembrane helix motion and receptor activation. The mechanism of activation that emerges is that multiple switches on the extracellular (or intradiscal) side of rhodopsin trigger structural changes that converge to disrupt the ionic lock between helices H3 and H6 on the intracellular side of the receptor. PMID:20004206

  5. Wheat-germ cell-free production of prion proteins for solid-state NMR structural studies.

    PubMed

    Noirot, Claire; Habenstein, Birgit; Bousset, Luc; Melki, Ronald; Meier, Beat H; Endo, Yaeta; Penin, François; Böckmann, Anja

    2011-04-30

    The expression of soluble, functional protein on a preparative scale poses a central challenge for structural studies. Cell-free protein expression has become a valuable alternative to cell-based methods, and allows today the expression of milligram quantities of protein. Its use is particularly attractive for NMR studies as it allows a multitude of isotopic labeling schemes. We have implemented and further developed protocols to prepare cell-free extracts from wheat germ to produce recombinant protein for solid-state NMR studies. Furthermore, we established the Renilla luciferase model to optimise and evaluate extract quality, and report first productions of the prions Ure2p and HET-s devoted to structural studies currently ongoing in our laboratories.

  6. alphaB-crystallin: a hybrid solid-state/solution-state NMR investigation reveals structural aspects of the heterogeneous oligomer.

    PubMed

    Jehle, Stefan; van Rossum, Barth; Stout, Joseph R; Noguchi, Satoshi M; Falber, Katja; Rehbein, Kristina; Oschkinat, Hartmut; Klevit, Rachel E; Rajagopal, Ponni

    2009-02-06

    Atomic-level structural information on alphaB-Crystallin (alphaB), a prominent member of the small heat-shock protein family, has been a challenge to obtain due its polydisperse oligomeric nature. We show that magic-angle spinning solid-state NMR can be used to obtain high-resolution information on an approximately 580-kDa human alphaB assembled from 175-residue 20-kDa subunits. An approximately 100-residue alpha-crystallin domain is common to all small heat-shock proteins, and solution-state NMR was performed on two different alpha-crystallin domain constructs isolated from alphaB. In vitro, the chaperone-like activities of full-length alphaB and the isolated alpha-crystallin domain are identical. Chemical shifts of the backbone and C(beta) resonances have been obtained for residues 64-162 (alpha-crystallin domain plus part of the C-terminus) in alphaB and the isolated alpha-crystallin domain by solid-state and solution-state NMR, respectively. Both sets of data strongly predict six beta-strands in the alpha-crystallin domain. A majority of residues in the alpha-crystallin domain have similar chemical shifts in both solid-state and solution-state, indicating similar structures for the domain in its isolated and oligomeric forms. Sites of intersubunit interaction are identified from chemical shift differences that cluster to specific regions of the alpha-crystallin domain. Multiple signals are observed for the resonances of M68 in the oligomer, identifying the region containing this residue as existing in heterogeneous environments within alphaB. Evidence for a novel dimerization motif in the human alpha-crystallin domain is obtained by a comparison of (i) solid-state and solution-state chemical shift data and (ii) (1)H-(15)N heteronuclear single quantum coherence spectra as a function of pH. The isolated alpha-crystallin domain undergoes a dimer-monomer transition over the pH range 7.5-6.8. This steep pH-dependent switch may be important for alphaB to function

  7. αB-Crystallin. A Hybrid Solid-State/Solution-State NMR Investigation Reveals Structural Aspects of the Heterogeneous Oligomer

    SciTech Connect

    Jehle, Stefan; van Rossum, Barth; Stout, Joseph R.; Noguchi, Satoshi M.; Falber, Katja; Rehbein, Kristina; Oschkinat, Hartmut; Klevit, Rachel E.; Rajagopal, Ponni

    2008-11-14

    Atomic-level structural information on αB-Crystallin (αB), a prominent member of the small heat-shock protein family, has been a challenge to obtain due its polydisperse oligomeric nature. We show that magic-angle spinning solid-state NMR can be used to obtain high-resolution information on an ~580-kDa human αB assembled from 175-residue 20-kDa subunits. An ~100-residue α-crystallin domain is common to all small heat-shock proteins, and solution-state NMR was performed on two different α- crystallin domain constructs isolated from αB. In vitro, the chaperone-like activities of full-length αB and the isolated α-crystallin domain are identical. Chemical shifts of the backbone and Cβ resonances have been obtained for residues 64–162 (α-crystallin domain plus part of the C-terminus) in αB and the isolated α-crystallin domain by solid-state and solution-state NMR, respectively. Both sets of data strongly predict six β-strands in the α-crystallin domain. A majority of residues in the α-crystallin domain have similar chemical shifts in both solid-state and solution-state, indicating similar structures for the domain in its isolated and oligomeric forms. Sites of intersubunit interaction are identified from chemical shift differences that cluster to specific regions of the α-crystallin domain. Multiple signals are observed for the resonances of M68 in the oligomer, identifying the region containing this residue as existing in heterogeneous environments within αB. Evidence for a novel dimerization motif in the human α-crystallin domain is obtained by a comparison of (i) solid-state and solution-state chemical shift data and (ii) 1H–15N heteronuclear single quantum coherence spectra as a function of pH. The isolated α-crystallin domain undergoes a dimer–monomer transition over the pH range 7.5–6.8. This steep pHdependent switch may be important for αB to function optimally (e.g., to preserve the filament integrity

  8. Identification of double four-ring units in germanosilicate ITQ-13 zeolite by solid-state NMR spectroscopy.

    PubMed

    Liu, Xiaolong; Chu, Yueying; Wang, Qiang; Wang, Weiyu; Wang, Chao; Xu, Jun; Deng, Feng

    2017-05-17

    Well-crystallized Ge-free and Ge-ITQ-13 were successfully obtained by solid state synthesis method. The Ge/Si ratio and the water content that are the two important factors in the synthesis of germanosilicate zeolites were explored for the formation of ITQ-13. The effect of the mineralizing agents (NH4F and NH4Cl) on the ITQ-13 synthesis was investigated as well. The obtained pure silica ITQ-13 and Ge-ITQ-13 were characterized by one- and two-dimensional solid- state NMR techniques. One-dimensional (1D) (19)F MAS, (1)H→(29)Si CP/MAS and (19)F→(29)Si CP/MAS NMR spectroscopy evidenced the formation of pure Si-D4R (double four ring) and Ge-D4R units, with the latter being generated by substitution of Si atom from the former units. The detailed configurations of the Ge-D4R units in ITQ-13 was revealed by two-dimensional (2D) (29)Si{(19)F} HETCOR NMR spectroscopy. With the help of theoretical calculations on the (19)F and (29)Si NMR chemical shifts, six types of D4R units were determined. The formation of the specific D4R unit confirms the structural directing roles of Ge atom and F ions in the formation of the D4R units in zeolite framework. The identification of the SiOSi bonds in the D4R units that connects the layers of ITQ-13 framework provided rationale for the high stability of the ITQ-13 in the degermanation treatment. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. A solid-state NMR study of hydrogen-bonding networks and ion dynamics in benzimidazole salts.

    PubMed

    Traer, Jason W; Britten, James F; Goward, Gillian R

    2007-05-24

    On the basis of our solid-state NMR characterization of dynamics in two model salts, we draw the analogy to the fuel cell membrane candidate, phosphoric acid-doped poly(benzimidazole), and conclude that phosphate anion dynamics contribute to long-range proton transport, whereas the mobility of the polymer itself is not a contributing factor. This is contrasted with emerging membrane candidates, which rely on fully covalently bonded acid donors and acceptors, and target high-temperature PEM fuel cell operation in the absence of liquid electrolyte. The hydrogen-bonding structures of benzimidazolium phosphate and benzimidazolium methane phosphonate are established using X-ray diffraction paired with solid-state 1H DQF NMR. By comparing the dynamics of the phosphate and methane phosphonate anions with the dynamics of imidazolium and benzimidazolium cations, the relative importance of these processes in proton transport is determined. The imidazolium cation is known to undergo two-site ring reorientation on the millisecond time scale. In contrast, it is shown here that the benzimidazolium rings are immobile in analogous salts, on a time scale extending into the tens of seconds. Therefore, we look to the phosphate anions and demonstrate that the time scale of tetrahedral reorientation is comparably fast (50 ms). Moreover, the 31P CODEX NMR data clearly indicate a four-site jump process. In contrast, the methane phosphonate undergoes a three-site jump on a slower time scale (75 ms). A mechanism for a zigzag pathway of proton transport through the phosphonate salt crystallites is developed based on the 31P CODEX and 1H variable-temperature MAS NMR data.

  10. Optimization of an absolute sensitivity in a glassy matrix during DNP-enhanced multidimensional solid-state NMR experiments.

    PubMed

    Takahashi, Hiroki; Fernández-de-Alba, Carlos; Lee, Daniel; Maurel, Vincent; Gambarelli, Serge; Bardet, Michel; Hediger, Sabine; Barra, Anne-Laure; De Paëpe, Gaël

    2014-02-01

    Thanks to instrumental and theoretical development, notably the access to high-power and high-frequency microwave sources, high-field dynamic nuclear polarization (DNP) on solid-state NMR currently appears as a promising solution to enhance nuclear magnetization in many different types of systems. In magic-angle-spinning DNP experiments, systems of interest are usually dissolved or suspended in glass-forming matrices doped with polarizing agents and measured at low temperature (down to ∼100K). In this work, we discuss the influence of sample conditions (radical concentration, sample temperature, etc.) on DNP enhancements and various nuclear relaxation times which affect the absolute sensitivity of DNP spectra, especially in multidimensional experiments. Furthermore, DNP-enhanced solid-state NMR experiments performed at 9.4 T are complemented by high-field CW EPR measurements performed at the same magnetic field. Microwave absorption by the DNP glassy matrix is observed even below the glass transition temperature caused by softening of the glass. Shortening of electron relaxation times due to glass softening and its impact in terms of DNP sensitivity is discussed. Copyright © 2014. Published by Elsevier Inc.

  11. Probing hydrogen bonding in cocrystals and amorphous dispersions using (14)N-(1)H HMQC solid-state NMR.

    PubMed

    Tatton, Andrew S; Pham, Tran N; Vogt, Frederick G; Iuga, Dinu; Edwards, Andrew J; Brown, Steven P

    2013-03-04

    Cocrystals and amorphous solid dispersions have generated interest in the pharmaceutical industry as an alternative to more established solid delivery forms. The identification of intermolecular hydrogen bonding interactions in a nicotinamide palmitic acid cocrystal and a 50% w/w acetaminophen-polyvinylpyrrolidone solid dispersion are reported using advanced solid-state magic-angle spinning (MAS) NMR methods. The application of a novel (14)N-(1)H HMQC experiment, where coherence transfer is achieved via through-space couplings, is shown to identify specific hydrogen bonding motifs. Additionally, (1)H isotropic chemical shifts and (14)N electric field gradient (EFG) parameters, both accessible from (14)N-(1)H HMQC experiments, are shown to be sensitive to changes in hydrogen bonding geometry. Numerous indicators of molecular association are accessible from this experiment, including NH cross-peaks occurring from intermolecular hydrogen bonds and changes in proton chemical shifts or electric field gradient parameters. First-principles calculations using the GIPAW approach that yield accurate estimates of isotropic chemical shifts, and EFG parameters were used to assist in assignment. It is envisaged that (14)N-(1)H HMQC solid state NMR experiments could become a valuable screening technique of solid delivery forms in the pharmaceutical industry.

  12. Structure of uniaxially aligned 13C labeled silk fibroin fibers with solid state 13C-NMR

    NASA Astrophysics Data System (ADS)

    Demura, Makoto; Yamazaki, Yasunobu; Asakura, Tetsuo; Ogawa, Katsuaki

    1998-01-01

    Carbon-13 isotopic labeling of B. mori silk fibroin was achieved biosynthetically with [1- 13C] glycine in order to determine the carbonyl bond orientation angle of glycine sites with the silk fibroin. Angular dependence of 13C solid state NMR spectra of uniaxially oriented silk fibroin fiber block sample due to the carbonyl 13C chemical shift anisotropy was simulated according to the chemical shift transformation with Euler angles, αF and βF, from principal axis system (PAS) to fiber axis system (FAS). The another Euler angles, αDCO and βDCO, for transformation from PAS to the molecular symmetry axis were determined from the [1- 13C] glycine sequence model compounds for the silk fibroin. By the combination of these Euler angles, the carbonyl bond orientation angle with respect to FAS of the [1- 13C] glycine sites of the silk fibroin was determined to be 90 ± 5°. This value is in agreement with the X-ray diffraction and our previous solid state NMR data of B. mori silk fibroin fiber (a typical β-pleated sheet) within experimental error.

  13. Study of cross - relaxation and molecular dynamics in the solid 3-(trifluoromethyl) benzoic acid by solid state NMR off - resonance.

    PubMed

    Woźniak-Braszak, Aneta

    2017-02-01

    Molecular dynamics of the solid 3-(trifluoromethyl) benzoic acid containing proton (1)H and fluorine (19)F nuclei was explored by the solid-state NMR off - resonance technique. Contrary to the previous experiments the proton nuclei system I relaxed in the off - resonance effective field B→e while fluorine nuclei system S was saturated for short time in comparison to the relaxation time T1I. New cross - relaxation solid - state NMR off - resonance experiments were conducted on a homebuilt pulse spectrometer operating at the on-resonance frequency of 30.2MHz, at the off - resonance frequency varied between 30.2 and 30.6MHz for protons and at the frequency of 28.411MHz for fluorines, respectively. Based on the experimental data the dispersions of the proton off - resonance spin - lattice relaxation rate ρρ(I), the fluorine off - resonance spin - lattice relaxation rate ρρ(S) and the cross - relaxation rate σρ in the rotating frame were determined. Copyright © 2016 Elsevier Inc. All rights reserved.

  14. Effective Hamiltonians by optimal control: solid-state NMR double-quantum planar and isotropic dipolar recoupling.

    PubMed

    Tosner, Zdenek; Glaser, Steffen J; Khaneja, Navin; Nielsen, Niels Chr

    2006-11-14

    We report the use of optimal control algorithms for tailoring the effective Hamiltonians in nuclear magnetic resonance (NMR) spectroscopy through sophisticated radio-frequency (rf) pulse irradiation. Specifically, we address dipolar recoupling in solid-state NMR of powder samples for which case pulse sequences offering evolution under planar double-quantum and isotropic mixing dipolar coupling Hamiltonians are designed. The pulse sequences are constructed numerically to cope with a range of experimental conditions such as inhomogeneous rf fields, spread of chemical shifts, the intrinsic orientation dependencies of powder samples, and sample spinning. While the vast majority of previous dipolar recoupling sequences are operating through planar double-or zero-quantum effective Hamiltonians, we present here not only improved variants of such experiments but also for the first time homonuclear isotropic mixing sequences which transfers all I(x), I(y), and I(z) polarizations from one spin to the same operators on another spin simultaneously and with equal efficiency. This property may be exploited to increase the signal-to-noise ratio of two-dimensional experiments by a factor of square root 2 compared to conventional solid-state methods otherwise showing the same efficiency. The sequences are tested numerically and experimentally for a powder of (13)C(alpha),(13)C(beta)-L-alanine and demonstrate substantial sensitivity gains over previous dipolar recoupling experiments.

  15. Crystallinity and compositional changes in carbonated apatites: Evidence from {sup 31}P solid-state NMR, Raman, and AFM analysis

    SciTech Connect

    McElderry, John-David P.; Zhu, Peizhi; Mroue, Kamal H.; Xu, Jiadi; Pavan, Barbara; Fang, Ming; Zhao, Guisheng; McNerny, Erin; Kohn, David H.; Franceschi, Renny T.; Holl, Mark M.Banaszak; Tecklenburg, Mary M.J.; Ramamoorthy, Ayyalusamy; Morris, Michael D.

    2013-10-15

    Solid-state (magic-angle spinning) NMR spectroscopy is a useful tool for obtaining structural information on bone organic and mineral components and synthetic model minerals at the atomic-level. Raman and {sup 31}P NMR spectral parameters were investigated in a series of synthetic B-type carbonated apatites (CAps). Inverse {sup 31}P NMR linewidth and inverse Raman PO{sub 4}{sup 3−}ν{sub 1} bandwidth were both correlated with powder XRD c-axis crystallinity over the 0.3–10.3 wt% CO{sub 3}{sup 2−} range investigated. Comparison with bone powder crystallinities showed agreement with values predicted by NMR and Raman calibration curves. Carbonate content was divided into two domains by the {sup 31}P NMR chemical shift frequency and the Raman phosphate ν{sub 1} band position. These parameters remain stable except for an abrupt transition at 6.5 wt% carbonate, a composition which corresponds to an average of one carbonate per unit cell. This near-binary distribution of spectroscopic properties was also found in AFM-measured particle sizes and Ca/P molar ratios by elemental analysis. We propose that this transition differentiates between two charge-balancing ion-loss mechanisms as measured by Ca/P ratios. These results define a criterion for spectroscopic characterization of B-type carbonate substitution in apatitic minerals. - Graphical abstract: Carbonated apatite shows an abrupt change in spectral (NMR, Raman) and morphological (AFM) properties at a composition of about one carbonate substitution per unit cell. Display Omitted - Highlights: • Crystallinity (XRD), particle size (AFM) of carbonated apatites and bone mineral. • Linear relationships among crystallinity, {sup 31}P NMR and Raman inverse bandwidths. • Low and high carbonated apatites use different charge-balancing ion-loss mechanism.

  16. Combining (27)Al Solid-State NMR and First-Principles Simulations To Explore Crystal Structure in Disordered Aluminum Oxynitride.

    PubMed

    Tu, Bingtian; Liu, Xin; Wang, Hao; Wang, Weimin; Zhai, Pengcheng; Fu, Zhengyi

    2016-12-19

    The nuclear magnetic resonance (NMR) technique gives insight into the local information in a crystal structure, while Rietveld refinement of powder X-ray diffraction (PXRD) sketches out the framework of a crystal lattice. In this work, first-principles calculations were combined with the solid-state NMR technique and Rietveld refinement to explore the crystal structure of a disordered aluminum oxynitride (γ-alon). The theoretical NMR parameters (chemical shift, δiso, quadrupolar coupling constants, CQ, and asymmetry parameter, η) of Al22.5O28.5N3.5, predicted by the gauge-including projector augmented wave (GIPAW) algorithm, were used to facilitate the analytical investigation of the (27)Al magic-angle spinning (MAS) NMR spectra of the as-prepared sample, whose formula was confirmed to be Al2.811O3.565N0.435 by quantitative analysis. The experimental δiso, CQ, and η of (27)Al showed a small discrepancy compared with theoretical models. The ratio of aluminum located at the 8a to 16d sites was calculated to be 0.531 from the relative integration of peaks in the (27)Al NMR spectra. The occupancies of aluminum at the 8a and 16d positions were determined through NMR investigations to be 0.9755 and 0.9178, respectively, and were used in the Rietveld refinement to obtain the lattice parameter and anion parameter of Al2.811O3.565N0.435. The results from (27)Al NMR investigations and PXRD structural refinement complemented each other. This work provides a powerful and accessible strategy to precisely understand the crystal structure of novel oxynitride materials with multiple disorder.

  17. Solid-State (17) O NMR Reveals Hydrogen-Bonding Energetics: Not All Low-Barrier Hydrogen Bonds Are Strong.

    PubMed

    Lu, Jiasheng; Hung, Ivan; Brinkmann, Andreas; Gan, Zhehong; Kong, Xianqi; Wu, Gang

    2017-02-22

    While NMR and IR spectroscopic signatures and structural characteristics of low-barrier hydrogen bond (LBHB) formation are well documented in the literature, direct measurement of the LBHB energy is difficult. Here, we show that solid-state (17) O NMR spectroscopy can provide unique information about the energy required to break a LBHB. Our solid-state (17) O NMR data show that the HB enthalpy of the O⋅⋅⋅H⋅⋅⋅N LBHB formed in crystalline nicotinic acid is only 7.7±0.5 kcal mol(-1) , suggesting that not all LBHBs are particularly strong.

  18. Identification of Li-Ion Battery SEI Compounds through (7)Li and (13)C Solid-State MAS NMR Spectroscopy and MALDI-TOF Mass Spectrometry.

    PubMed

    Huff, Laura A; Tavassol, Hadi; Esbenshade, Jennifer L; Xing, Wenting; Chiang, Yet-Ming; Gewirth, Andrew A

    2016-01-13

    Solid-state (7)Li and (13)C MAS NMR spectra of cycled graphitic Li-ion anodes demonstrate SEI compound formation upon lithiation that is followed by changes in the SEI upon delithiation. Solid-state (13)C DPMAS NMR shows changes in peaks associated with organic solvent compounds (ethylene carbonate and dimethyl carbonate, EC/DMC) upon electrochemical cycling due to the formation of and subsequent changes in the SEI compounds. Solid-state (13)C NMR spin-lattice (T1) relaxation time measurements of lithiated Li-ion anodes and reference poly(ethylene oxide) (PEO) powders, along with MALDI-TOF mass spectrometry results, indicate that large-molecular-weight polymers are formed in the SEI layers of the discharged anodes. MALDI-TOF MS and NMR spectroscopy results additionally indicate that delithiated anodes exhibit a larger number of SEI products than is found in lithiated anodes.

  19. Rapid and accurate determination of the lignin content of lignocellulosic biomass by solid-state NMR.

    PubMed

    Fu, Li; McCallum, Scott A; Miao, Jianjun; Hart, Courtney; Tudryn, Gregory J; Zhang, Fuming; Linhardt, Robert J

    2015-02-01

    Biofuels and biomaterials, produced from lignocellulosic feedstock, require facile access to cellulose and hemicellulose to be competitive with petroleum processing and sugar-based fermentation. Physical-chemical barriers resulting from lignin complicates the hydrolysis biomass into fermentable sugars. Thus, the amount of lignin within a substrate is critical in determining biomass processing. The application of (13)C cross-polarization, magic-angle spinning, and solid-state nuclear magnetic resonance for the direct quantification of lignin content in biomass is examined. Using a standard curve constructed from pristine lignin and cellulose, the lignin content of a biomass sample is accurately determined through direct measurement without chemical or enzymatic pre-treatment.

  20. Regenerated silk fibers: Structural studies and solid state NMR techniques for efficient multiple distance determinations in proteins

    NASA Astrophysics Data System (ADS)

    Liivak, Oskar

    2000-09-01

    Material Science is the science of understanding the relationship between the molecular level structure of a material and its macroscopic properties. Such research requires both the ability to determine molecular structure and the ability to control and modify the molecular structure. The present research into silks, especially the dragline silk from the spider Nephila clavipes , is occurring at a time when these two criteria are beginning to be met for proteins like spider silk. Genetic engineering has evolved to the point where material scientists have full control over the primary sequence of amino acids that comprise proteins. In addition, solid state nuclear magnetic resonance (NMR) techniques exist which allow us to probe molecular structure. This work applies solid state NMR to the study of the structure of silk fibers. In particular, we focus on techniques of fiber regeneration from solution. The purpose is not only to develop the techniques by which genetically engineered fibers could be spun into fibers for mass production but also as a tool into fundamental silk research. Results on these regenerated fibers show a correlation between the fraction of the silk's alanine residues which are in the β-sheet conformation and the ultimate tensile strength of the fibers. In addition, in a clever mating of the fiber regeneration technique and the solid state NMR distance measurement experiment, rotational echo double resonance (REDOR), we investigate the supramolecular topology of the alanine β-sheet crystals. Even though the REDOR technique has failings for the complicated ISn spin systems found in the silk samples, a qualitative analysis does indicate that the β-sheet crystals are intermolecular. Finally, we investigate a new class of REDOR-like experiments which are designed to overcome the failings of REDOR in ISn spin systems. Experimental data is shown to validate these ideas. An alternate pulse sequence is also introduced and verified with experimental

  1. Characterisation of different polymorphs of tris(8-hydroxyquinolinato)aluminium(III) using solid-state NMR and DFT calculations

    PubMed Central

    Goswami, Mithun; Nayak, Pabitra K; Periasamy, N; Madhu, PK

    2009-01-01

    Background Organic light emitting devices (OLED) are becoming important and characterisation of them, in terms of structure, charge distribution, and intermolecular interactions, is important. Tris(8-hydroxyquinolinato)-aluminium(III), known as Alq3, an organomettalic complex has become a reference material of great importance in OLED. It is important to elucidate the structural details of Alq3 in its various isomeric and solvated forms. Solid-state nuclear magnetic resonance (NMR) is a useful tool for this which can also complement the information obtained with X-ray diffraction studies. Results We report here 27Al one-dimensional (1D) and two-dimensional (2D) multiple-quantum magic-angle spinning (MQMAS) NMR studies of the meridional (α-phase) and the facial (δ-phase) isomeric forms of Alq3. Quadrupolar parameters are estimated from the 1D spectra under MAS and anisotropic slices of the 2D spectra and also calculated using DFT (density functional theory) quantum-chemical calculations. We have also studied solvated phase of Alq3 containing ethanol in its lattice. We show that both the XRD patterns and the quadrupolar parameters of the solvated phase are different from both the α-phase and the δ-phase, although the fluorescence emission shows no substantial difference between the α-phase and the solvated phase. Moreover, we have shown that after the removal of ethanol from the matrix the solvated Alq3 has similar XRD patterns and quadrupolar parameters to that of the α-phase. Conclusion The 2D MQMAS experiments have shown that all the different modifications of Alq3 have 27Al in single unique crystallographic site. The quadrupolar parameters predicted using the DFT calculation under the isodensity polarisable continuum model resemble closely the experimentally obtained values. The solvated phase of Alq3 containing ethanol has structural difference from the α-phase of Alq3 (containing meridional isomer) from the solid-state NMR studies. Solid-state NMR can

  2. Synthesis and solid-state NMR characterization of cubic mesoporous silica SBA-1 functionalized with sulfonic acid groups.

    PubMed

    Tsai, Hui-Hsu Gavin; Chiu, Po-Jui; Jheng, Guang-Liang; Ting, Chun-Chiang; Pan, Yu-Chi; Kao, Hsien-Ming

    2011-07-01

    Well-ordered cubic mesoporous silicas SBA-1 functionalized with sulfonic acid groups have been synthesized through in situ oxidation of mercaptopropyl groups with H(2)O(2) via co-condensation of tetraethoxysilane (TEOS) and 3-mercaptopropyltrimethoxysilane (MPTMS) templated by cetyltriethylammonium bromide (CTEABr) under strong acidic conditions. Various synthesis parameters such as the amounts of H(2)O(2) and MPTMS on the structural ordering of the resultant materials were systematically investigated. The materials thus obtained were characterized by a variety of techniques including powder X-ray diffraction (XRD), multinuclear solid-state Nuclear Magnetic Resonance (NMR) spectroscopy, (29)Si{(1)H} 2D HETCOR (heteronuclear correlation) NMR spectroscopy, thermogravimetric analysis (TGA), and nitrogen sorption measurements. By using (13)C CPMAS NMR technique, the status of the incorporated thiol groups and their transformation to sulfonic acid groups can be monitored and, as an extension, to define the optimum conditions to be used for the oxidation reaction to be quantitative. In particular, (29)Si{(1)H} 2D HETCOR NMR revealed that the protons in sulfonic acid groups are in close proximity to the silanol Q(3) species, but not close enough to form a hydrogen bond.

  3. Structure and Dynamics of Extracellular Loops in Human Aquaporin-1 from Solid-State NMR and Molecular Dynamics.

    PubMed

    Wang, Shenlin; Ing, Christopher; Emami, Sanaz; Jiang, Yunjiang; Liang, Hongjun; Pomès, Régis; Brown, Leonid S; Ladizhansky, Vladimir

    2016-09-22

    Multiple moderate-resolution crystal structures of human aquaporin-1 have provided a foundation for understanding the molecular mechanism of selective water translocation in human cells. To gain insight into the interfacial structure and dynamics of human aquaporin-1 in a lipid environment, we performed nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics simulations. Using magic angle spinning solid-state NMR, we report a near complete resonance assignment of the human aquaporin-1. Chemical shift analysis of the secondary structure identified pronounced deviations from crystallographic structures in extracellular loops A and C, including the cis Y37-P38 bond in loop A, as well as ordering and immobilization of loop C. Site-specific H/D exchange measurements identify a number of protected nitrogen-bearing side chains and backbone amide groups, involved in stabilizing the loops. A combination of molecular dynamics simulations with NMR-derived restraints and filtering based on solvent accessibility allowed for the determination of a structural model of extracellular loops largely consistent with NMR results. The simulations reveal loop stabilizing interactions that alter the extracellular surface of human AQP1, with possible implications for water transport regulation through the channel. Modulation of water permeation may occur as a result of rearrangement of side chains from loop C in the extracellular vestibule of hAQP1, affecting the aromatic arginine selectivity filter.

  4. Detergent-like properties of magainin antibiotic peptides: a 31P solid-state NMR spectroscopy study.

    PubMed

    Bechinger, Burkhard

    2005-06-15

    (31)P solid-state NMR spectroscopy has been used to investigate the macroscopic phase behavior of phospholipid bilayers in the presence of increasing amounts of magainin antibiotic peptides. Addition of >1 mol% magainin 2 to gel-phase DMPC or liquid crystalline POPC membranes respectively, results in (31)P NMR spectra that are characterized by the coexistence of isotropic signals and line shapes typical for phospholipid bilayers. The isotropic signal intensity is a function of temperature and peptide concentration. At peptide concentrations >4 mol% of the resulting phospholipid (31)P NMR spectra are characteristic of magnetically oriented POPC bilayers suggesting the formation of small disk-like micelles or perforated sheets. In contrast, addition of magainin to acidic phospholipids results in homogenous bilayer-type (31)P NMR spectra with reduced chemical shift anisotropies. The results presented are in good agreement with the interfacial insertion of magainin helices with an alignment parallel to the surface of the phospholipid bilayers. The resulting curvature strain results in detergent-like properties of the amphipathic helical peptides.

  5. Molecular Dynamics and Morphology of High Performance Elastomers and Fibers by Solid State NMR

    DTIC Science & Technology

    2016-06-30

    nuclear magnetic resonance (ssNMR) spectroscopy to investigate the chemical structure and physical state of the residual phosphorous in PBO fiber...ssNMR) spectroscopy to investigate the chemical structure and physical state of the residual phosphorous in PBO fiber, which has been long suspected to...phosphorous. The present report investigates the chemical structure and physical state of the residual phosphorous in PBO fiber using 31P solid

  6. Solid-state Hadamard NMR spectroscopy: simultaneous measurements of multiple selective homonuclear scalar couplings.

    PubMed

    Kakita, Veera Mohana Rao; Kupče, Eriks; Bharatam, Jagadeesh

    2015-02-01

    Unambiguous measurement of homonuclear scalar couplings (J) in multi-spin scalar network systems is not straightforward. Further, the direct measurement of J-couplings is obscured in solid-state samples due to the dipolar and chemical shift anisotropy (CSA)-dominated line broadening, even under the magic angle spinning (MAS). We present a new multiple frequency selective spin-echo method based on Hadamard matrix encoding, for simultaneous measurement of multiple homonuclear scalar couplings (J) in the solid-state. In contrast to the Hadamard encoded selective excitation schemes known for the solution-state, herein the selectivity is achieved during refocusing period. The Hadamard encoded refocusing scheme concurrently allows to create the spin-spin commutation property between number of spin-pairs of choice in uniformly labelled molecules, which, therefore avoids (1) the repetition of the double selective refocusing experiments for each spin-pair and (2) the synthesis of expensive selective labelled molecules. The experimental scheme is exemplified for determining (1)JCC and (3)JCC values in (13)C6l-Histidine.HCl molecule, which are found to be in excellent agreement with those measured in conventional double frequency selective refocusing mode as well as in the solution-state. This method can be simply extended to 2D/3D pulse schemes and be applied to small bio-molecular solids.

  7. Reorientational dynamics and solid-phase transformation of ammonium dicyanamide into dicyandiamide: a (2)H solid-state NMR study.

    PubMed

    Lotsch, Bettina V; Schnick, Wolfgang; Naumann, Ernst; Senker, Jürgen

    2007-10-11

    The reorientational dynamics of ammonium dicyanamide ND4[N(C[triple bond]N)2] and the kinetics as well as the mechanism of the solid-state isomerization reaction from ammonium dicyanamide into dicyandiamide (N[triple bond]C-N==C(NH2)2) was studied by means of 2H and 14N solid-state NMR spectroscopy in a temperature range between 38 and 390 K. Whereas in previous investigations the mechanism of the solid-state transformation was investigated by means of vibrational and magic angle spinning solid-state NMR spectroscopy as well as neutron diffraction, we here present a comprehensive 2H study of the ammonium ion dynamics prior to and during the course of the reaction, thereby highlighting possible cross correlations between dynamics and reactivity involving the ammonium ion. The ND4+ group was found to undergo thermally activated random jumps in a tetrahedral potential, which is increasingly distorted with increasing temperature, giving rise to an asymmetrically compressed or elongated tetrahedron with deviations from the tetrahedral angle of up to 6 degrees . The correlation time follows an Arrhenius law with an activation energy of Ea = 25.8(2) kJ mol(-1) and an attempt frequency of tau0(-1) = 440(80) THz. The spin-lattice relaxation times were fitted according to a simple Bloembergen-Purcell-Pound type model with a T1 minimum of 4 ms at 230 K. Temperature-dependent librational amplitudes were extracted by line-shape simulations between 38 and 390 K and contrasted with those obtained by neutron diffraction, their values ranging between 5 and 28 degrees . The onset and progress of the solid-phase transformation were followed in situ at temperatures above 372 K and could be classified as a strongly temperature-dependent, heterogeneous two-step reaction proceeding with rapid evolution of ammonia and comparatively slow subsequent reintegration into the solid. On the microscopic level, this correlates with a rapid proton transfer -- possibly triggered by a coupling

  8. Investigations of the structure and "interfacial" surface chemistry of Bioglass (RTM) materials by solid-state multinuclear NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Sarkar, Gautam

    Bioactive materials such as BioglassRTM 45S5 (45% SiO 2, 24.5% CaO, 24.5% Na2O, and 6% P2O5 by weight) are sodium-phosphosilicate glasses containing independent three-dimensional silicate and phosphate networks and Na+ and Ca2+ ions as modifying cations. Due to their bioactivity, these materials are currently used as implants and for other surgical and clinical applications. The bioactivity of BioglassesRTM is due to their unique capability to form chemical bonds to tissues through an octacalciumphosphate (OCP)- and/or hydroxyapatite-like (HA) "interfacial" matrix. The formation of OCP and/or HA is preceded by the formation of a silica-rich surface layer and the subsequent growth of an amorphous calcium phosphate (a-CP) layer. Structural characterization of a series of commercial and synthesized Bioglass materials 45S5 52S, 55S, 60S, and synthesized 17O-labelled "Bioglass materials 45S, 52S, 55S and 60S" have been obtained using solid-state single-pulse magic-angle spinning (SP/MAS) 17O, 23Na, 29Si and 31P NMR. The 17O NMR isotropic chemical shifts and estimates of the quadrupole coupling constants (Cq) [at fixed asymmetry parameter ( hQ ) values of zero] have been obtained from solid-state spin-echo 17O SP/MAS NMR spectra of 17O-labelled "Bioglasses". The simulation results of these spectra reveal the presence of both bridging-oxygens (BO, i.e. ≡ Si-17OSi ≡ ) and non-bridging oxygens (NBO, i.e. ≡ Si-17O-Na+/Ca2+ ) in the silicate networks in these materials. 17O NMR spectra of these Bioglass materials do not show any direct evidence for the presence of BO and NBO atoms in the phosphate units; however, they are expected to be present in small amounts. In vitro reactions of BioglassRTM 45S5, 60S and 77S powders have been used to study the "interfacial" surface chemistry of these materials in simulated body-fluid (SBF, Kyoto or K9 solution) and/or 17O-enriched tris-buffer solution. 29Si and 31P SP/MAS NMR have been used to identify and quantify the extent of

  9. NMR crystallography to probe the breathing effect of the MIL-53(Al) metal-organic framework using solid-state NMR measurements of (13)C-(27)Al distances.

    PubMed

    Giovine, Raynald; Volkringer, Christophe; Trébosc, Julien; Amoureux, Jean Paul; Loiseau, Thierry; Lafon, Olivier; Pourpoint, Frédérique

    2017-03-01

    The metal-organic framework MIL-53(Al) (aluminium terephthalate) exhibits a structural transition between two porous structures with large pore (lp) or narrow pore (np) configurations. This transition, called the breathing effect, is observed upon changes in temperature or external pressure, as well as with the adsorption of guest molecules, such as H2O, within the pores. We show here how these different pore openings can be detected by observing the dephasing of (13)C magnetization under (13)C-(27)Al dipolar couplings using Rotational-Echo Saturation-Pulse Double-Resonance (RESPDOR) solid-state NMR experiments with Simultaneous Frequency and Amplitude Modulation (SFAM) recoupling. These double-resonance NMR experiments between (13)C and (27)Al nuclei, which have close Larmor frequencies, are feasible thanks to the use of a frequency splitter. The experimental SFAM-RESPDOR signal fractions agree well with those simulated from the MIL-53(Al)-lp and -np crystal structures obtained from powder X-ray diffraction analysis. Hence, these (13)C-(27)Al solid-state NMR experiments validate these structures and confirm their rigidity. A similar agreement is reported for the framework ligands in the as-synthesized (as) MIL-53(Al), in which the pores contain free ligands. Furthermore, in this case, (13)C-{(27)Al} SFAM-RESPDOR experiments allow an estimation of the average distance between the free ligands and the (27)Al nuclei of the framework.

  10. New insights on the mechanism of palladium-catalyzed hydrolysis of sodium borohydride from 11B NMR measurements.

    PubMed

    Guella, G; Zanchetta, C; Patton, B; Miotello, A

    2006-08-31

    To gain insight on the mechanistic aspects of the palladium-catalyzed hydrolysis of NaBH(4) in alkaline media, the kinetics of the reaction has been investigated by (11)B NMR (nuclear magnetic resonance) measurements taken at different times during the reaction course. Working with BH(4)(-) concentration in the range 0.05-0.1 M and with a [substrate]/[catalyst] molar ratio of 0.03-0.11, hydrolysis has been found to follow a first-order kinetic dependence from concentration of both the substrate and the catalyst (Pd/C 10 wt %). We followed the reaction of NaBH(4) and its perdeuterated analogue NaBD(4) in H(2)O, in D(2)O and H(2)O/D(2)O mixtures. When the process was carried out in D(2)O, deuterium incorporation in BH(4)(-) afforded BH(4)(-)(n)D(n)(-) (n = 1, 2, 3, 4) species, and a competition between hydrolysis and hydrogen/deuterium exchange processes was observed. By fitting the kinetics NMR data by nonlinear least-squares regression techniques, the rate constants of the elementary steps involved in the palladium-catalyzed borohydride hydrolysis have been evaluated. Such a regression analysis was performed on a reaction scheme wherein the starting reactant BH(4)(-) is allowed both to reversibly exchange hydrogen with deuterium atoms of D(2)O and to irreversibly hydrolyze into borohydroxy species B(OD)(4)(-). In contrast to acid-catalyzed hydrolysis of sodium borohydride, our results indicate that in the palladium-catalyzed process the rate constants of the exchange processes are higher than those of the corresponding hydrolysis reactions.

  11. Synthesis and solid-state NMR structural characterization of 13C-labeled graphite oxide.

    PubMed

    Cai, Weiwei; Piner, Richard D; Stadermann, Frank J; Park, Sungjin; Shaibat, Medhat A; Ishii, Yoshitaka; Yang, Dongxing; Velamakanni, Aruna; An, Sung Jin; Stoller, Meryl; An, Jinho; Chen, Dongmin; Ruoff, Rodney S

    2008-09-26

    The detailed chemical structure of graphite oxide (GO), a layered material prepared from graphite almost 150 years ago and a precursor to chemically modified graphenes, has not been previously resolved because of the pseudo-random chemical functionalization of each layer, as well as variations in exact composition. Carbon-13 (13C) solid-state nuclear magnetic resonance (SSNMR) spectra of GO for natural abundance 13C have poor signal-to-noise ratios. Approximately 100% 13C-labeled graphite was made and converted to 13C-labeled GO, and 13C SSNMR was used to reveal details of the chemical bonding network, including the chemical groups and their connections. Carbon-13-labeled graphite can be used to prepare chemically modified graphenes for 13C SSNMR analysis with enhanced sensitivity and for fundamental studies of 13C-labeled graphite and graphene.

  12. The use of multinuclear solid-state NMR to evaluate polystyrene/silica composites

    NASA Astrophysics Data System (ADS)

    Nogueira, Regina F.; Tavares, Maria Inês B.; Ferreira, Antônio G.

    2012-08-01

    Organic-inorganic hybrid materials have attracted much interest because of their novel and specific characteristics. One method to obtain these materials is in situ polymerization through free-radical polymerization. In this study, styrene monomers were covalently linked to silica (SiO2) using the suspension polymerization technique. In the reaction process, benzoyl peroxide was used as an initiator; poly(vinyl alcohol) was used as a suspension agent and water was used as the reaction environment. The styrene/silica composites were characterized in relation to chemical structure and microstructure using solution and solid-state nuclear magnetic resonance, and thermal analysis was performed by differential scanning calorimetry to evaluate the thermal transition temperature ( T g). All results showed that styrene/silica nanocomposites were obtained. The material with 2.5 % SiO2 showed the best characteristics.

  13. Rapid and accurate determination of the lignin content of lignocellulosic biomass by solid-state NMR

    PubMed Central

    Fu, Li; McCallum, Scott A.; Miao, Jianjun; Hart, Courtney; Tudryn, Gregory J.; Zhang, Fuming; Linhardt, Robert J.

    2014-01-01

    Biofuels and biomaterials, produced from lignocellulosic feedstock, require facile access to cellulose and hemicellulose to be competitive with petroleum processing and sugar-based fermentation. Physical-chemical barriers resulting from lignin complicates the hydrolysis biomass into fermentable sugars. Thus, the amount of lignin within a substrate is critical in determining biomass processing. The application of 13C cross-polarization, magic-angle spinning, and solid-state nuclear magnetic resonance for the direct quantification of lignin content in biomass is examined. Using a standard curve constructed from pristine lignin and cellulose, the lignin content of a biomass sample is accurately determined through direct measurement without chemical or enzymatic pre-treatment. PMID:25404762

  14. Dynamic nuclear polarization experiments at 14.1 T for solid-state NMR.

    PubMed

    Matsuki, Yoh; Takahashi, Hiroki; Ueda, Keisuke; Idehara, Toshitaka; Ogawa, Isamu; Toda, Mitsuru; Akutsu, Hideo; Fujiwara, Toshimichi

    2010-06-14

    Instrumentation for high-field dynamic nuclear polarization (DNP) at 14.1 T was developed to enhance the nuclear polarization for NMR of solids. The gyrotron generated 394.5 GHz submillimeter (sub-mm) wave with a power of 40 W in the second harmonic TE(0,6) mode. The sub-mm wave with a power of 0.5-3 W was transmitted to the sample in a low-temperature DNP-NMR probe with a smooth-wall circular waveguide system. The (1)H polarization enhancement factor of up to about 10 was observed for a (13)C-labeled compound with nitroxyl biradical TOTAPOL. The DNP enhancement was confirmed by the static magnetic field dependence of the NMR signal amplitude at 90 K. Improvements of the high-field DNP experiments are discussed.

  15. New in situ solid-state NMR techniques for probing the evolution of crystallization processes: pre-nucleation, nucleation and growth.

    PubMed

    Hughes, Colan E; Williams, P Andrew; Keast, Victoria L; Charalampopoulos, Vasileios G; Edwards-Gau, Gregory R; Harris, Kenneth D M

    2015-01-01

    The application of in situ techniques for investigating crystallization processes promises to yield significant new insights into fundamental aspects of crystallization science. With this motivation, we recently developed a new in situ solid-state NMR technique that exploits the ability of NMR to selectively detect the solid phase in heterogeneous solid-liquid systems (of the type that exist during crystallization from solution), with the liquid phase "invisible" to the measurement. As a consequence, the technique allows the first solid particles produced during crystallization to be observed and identified, and allows the evolution of different solid phases (e.g., polymorphs) present during the crystallization process to be monitored as a function of time. This in situ solid-state NMR strategy has been demonstrated to be a powerful approach for establishing the sequence of solid phases produced during crystallization and for the discovery of new polymorphs. The most recent advance of the in situ NMR methodology has been the development of a strategy (named "CLASSIC NMR") that allows both solid-state NMR and liquid-state NMR spectra to be measured (essentially simultaneously) during the crystallization process, yielding information on the complementary changes that occur in both the solid and liquid phases as a function of time. In this article, we present new results that highlight the application of our in situ NMR techniques to successfully unravel different aspects of crystallization processes, focusing on: (i) the application of a CLASSIC NMR approach to monitor competitive inclusion processes in solid urea inclusion compounds, (ii) exploiting liquid-state NMR to gain insights into co-crystal formation between benzoic acid and pentafluorobenzoic acid, and (iii) applications of in situ solid-state NMR for the discovery of new solid forms of trimethylphosphine oxide and L-phenylalanine. Finally, the article discusses a number of important fundamental issues

  16. Which kind of aromatic structures are produced during biomass charring? New insights provided by modern solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Knicker, Heike; Paneque-Carmona, Marina; Velasco-Molina, Marta; de la Rosa, José Maria; León-Ovelar, Laura Regina; Fernandez-Boy, Elena

    2017-04-01

    Intense research on biochar and charcoal of the last years has revealed that depending on the production conditions, the chemical and physical characteristics of their aromatic network can greatly vary. Since such variations are determining the behavior and stability of charred material in soils, a better understanding of the structural changes occurring during their heating and the impact of those changes on their function is needed. One method to characterize pyrogenic organic matter (PyOM) represents solid-state 13C NMR spectroscopy applying the cross polarization (CP) magic angle spinning technique (MAS). A drawback of this technique is that the quantification of NMR spectra of samples with highly condensed and proton-depleted structures is assumed to be bias. Typical samples with such attributes are charcoals produced at temperatures above 700°C under pyrolytic conditions. Commonly their high condensation degree leads to graphenic structures that are not only reducing the CP efficiency but create also a conductive lattice which acts as a shield and prevents the entering of the excitation pulse into the sample during the NMR experiments. Since the latter can damage the NMR probe and in the most cases the obtained NMR spectra show only one broad signal assignable to aromatic C, this technique is rarely applied for characterizing high temperature chars or soot. As a consequence, a more detailed knowledge of the nature of the aromatic ring systems is still missing. The latter is also true for the aromatic domains of PyOM produced at lower temperatures, since older NMR instruments operating at low magnetic fields deliver solid-state 13C NMR spectra with low resolution which turns a more detailed analysis of the aromatic chemical shift region into a challenging task. In order to overcome this disadvantages, modern NMR spectroscopy offers not only instruments with greatly improved resolution but also special pulse sequences for NMR experiments which allow a more

  17. Acceleration of natural-abundance solid-state MAS NMR measurements on bone by paramagnetic relaxation from gadolinium-DTPA

    NASA Astrophysics Data System (ADS)

    Mroue, Kamal H.; Zhang, Rongchun; Zhu, Peizhi; McNerny, Erin; Kohn, David H.; Morris, Michael D.; Ramamoorthy, Ayyalusamy

    2014-07-01

    Reducing the data collection time without affecting the signal intensity and spectral resolution is one of the major challenges for the widespread application of multidimensional nuclear magnetic resonance (NMR) spectroscopy, especially in experiments conducted on complex heterogeneous biological systems such as bone. In most of these experiments, the NMR data collection time is ultimately governed by the proton spin-lattice relaxation times (T1). For over two decades, gadolinium(III)-DTPA (Gd-DTPA, DTPA = Diethylene triamine pentaacetic acid) has been one of the most widely used contrast-enhancement agents in magnetic resonance imaging (MRI). In this study, we demonstrate that Gd-DTPA can also be effectively used to enhance the longitudinal relaxation rates of protons in solid-state NMR experiments conducted on bone without significant line-broadening and chemical-shift-perturbation side effects. Using bovine cortical bone samples incubated in different concentrations of Gd-DTPA complex, the 1H T1 values were calculated from data collected by 1H spin-inversion recovery method detected in natural-abundance 13C cross-polarization magic angle spinning (CPMAS) NMR experiments. Our results reveal that the 1H T1 values can be successfully reduced by a factor of 3.5 using as low as 10 mM Gd-DTPA without reducing the spectral resolution and thus enabling faster data acquisition of the 13C CPMAS spectra. These results obtained from 13C-detected CPMAS experiments were further confirmed using 1H-detected ultrafast MAS experiments on Gd-DTPA doped bone samples. This approach considerably improves the signal-to-noise ratio per unit time of NMR experiments applied to bone samples by reducing the experimental time required to acquire the same number of scans.

  18. High-field 19.6 T 27Al solid-state MAS NMR of in vitro aluminated brain tissue

    NASA Astrophysics Data System (ADS)

    Bryant, Pamela L.; Lukiw, Walter J.; Gan, Zhehong; Hall, Randall W.; Butler, Leslie G.

    2004-10-01

    The combination of 27Al high-field solid-state NMR (19.6 T) with rapid spinning speeds (17.8 kHz) is used to acquire 27Al NMR spectra of total RNA human brain temporal lobe tissues exposed to 0.10 mM Al 3+ (as AlCl 3) and of human retinal pigment epithelial cells (ARPE-19), grown in 0.10 mM AlCl 3. The spectra of these model systems show multiple Al 3+ binding sites, good signal/noise ratios and apparent chemical shift dispersions. A single broad peak (-3 to 11 ppm) is seen for the aluminated ARPE-19 cells, consistent with reported solution-state NMR chemical shifts of Al-transferrin. The aluminated brain tissue has a considerably different 27Al MAS NMR spectrum. In addition to the transferrin-type resonance, additional peaks are seen. Tentative assignments include: -9 to -3 ppm, octahedral AlO 6 (phosphate and water); 9 ppm, condensed AlO 6 units (Al-O-Al bridges); 24 ppm, tetrahedral AlO 3N and/or octahedral Al-carbonate; and 35 ppm, more N-substituted aluminum and /or tetrahedral AlO 4. Thus, brain tissue is susceptible to a broad range of coordination by aluminum. Furthermore, the moderate 27Al C Q values (all less than 10 MHz) suggest future NMR studies may be performed at 9.4 T and a spin rate of 20 kHz.

  19. A multinuclear solid state NMR spectroscopic study of the structural evolution of disordered calcium silicate sol-gel biomaterials.

    PubMed

    Lin, Zhongjie; Jones, Julian R; Hanna, John V; Smith, Mark E

    2015-01-28

    Disordered sol-gel prepared calcium silicate biomaterials show significant, composition dependent ability to bond with bone. Bone bonding is attributed to rapid hydroxycarbonate apatite (HCA) formation on the glass surface after immersion in body fluid (or implantation). Atomic scale details of the development of the structure of (CaO)x(SiO2)1-x (x = 0.2, 0.3 and 0.5) under heat treatment and subsequent dissolution in simulated body fluid (SBF) are revealed through a multinuclear solid state NMR approach using one-dimensional (17)O, (29)Si, (31)P and (1)H. Central to this study is the combination of conventional static and magic angle spinning (MAS) and two-dimensional (2D) triple quantum (3Q) (17)O NMR experiments that can readily distinguish and quantify the bridging (BOs) and non-bridging (NBOs) oxygens in the silicate network. Although soluble calcium is present in the sol, the (17)O NMR results reveal that the sol-gel produced network structure is initially dominated by BOs after gelation, aging and drying (e.g. at 120 °C), indicating a nanoscale mixture of the calcium salt and a predominantly silicate network. Only once the calcium salt is decomposed at elevated temperatures do the Ca(2+) ions become available to break BO. Apatite forming ability in SBF depends strongly on the surface OH and calcium content. The presence of calcium aids HCA formation via promotion of surface hydration and the ready availability of Ca(2+) ions. (17)O NMR shows the rapid loss of NBOs charge balanced by calcium as it is leached into the SBF. The formation of nanocrystalline, partially ordered HCA can be detected via(31)P NMR. This data indicates the importance of achieving the right balance of BO/NBO for optimal biochemical response and network properties.

  20. Humic acids as proxies for assessing different Mediterranean forest soils signatures using solid-state CPMAS 13C NMR spectroscopy.

    PubMed

    Duarte, Regina M B O; Fernández-Getino, Ana P; Duarte, Armando C

    2013-06-01

    Humic acids (HAs) of four representative forest soils profiles from Central Spain (two with different vegetation - pine and oak - but same parent material - granitie, and two with same vegetation - holm oak - but different parent material - granite and limestone) were investigated by solid-state cross polarization with magic angle spinning (13)C nuclear magnetic resonance (NMR) spectroscopy. The objectives included the investigation of the impact of different forest properties on HA composition, assessing how the structural characteristics of the HA vary with soil depth, and evaluating the role of HA as surrogates for mapping the different forest soils signatures using structural data derived from (13)C NMR spectroscopy. On average, alkyl C is the dominant C constituent (38-48% of the total NMR peak area) in all HA samples, followed by aromatic (12-22%) and O-alkyl C (12-19%), and finally carboxyl C (7.0-10%). The NMR data also indicated that HA composition is likely to be differently affected by the soil physico-chemical properties and type of forest vegetation. The structural characteristics of the HA from soil under oak did not differ broadly downward in the profile, whereas soil HA under pine forest exhibits a somewhat higher recalcitrant nature as a consequence of a higher degree of decomposition. The soil HA from holm oak forests differed from the other two forest soils, exhibiting a progressive decomposition of the alkyl C structures with increasing depth, while the carbohydrate-like indicator (O-alkyl C) is apparently being protected from mineralization in the horizons below the ground level. Overall, these differences in soil HA NMR signatures are an important diagnostic tool for understanding the role of different soil environmental factors on the structural composition of HA from Mediterranean forest soils. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. Distinguishing Bicontinuous Lipid Cubic Phases from Isotropic Membrane Morphologies Using 31P Solid-State NMR Spectroscopy

    PubMed Central

    Yang, Yu; Yao, Hongwei

    2015-01-01

    Nonlamellar lipid membranes are frequently induced by proteins that fuse, bend, and cut membranes. Understanding the mechanism of action of these proteins requires the elucidation of the membrane morphologies that they induce. While hexagonal phases and lamellar phases are readily identified by their characteristic solid-state NMR lineshapes, bicontinuous lipid cubic phases are more difficult to discern, since the static NMR spectra of cubic-phase lipids consist of an isotropic 31P or 2H peak, indistinguishable from the spectra of isotropic membrane morphologies such as micelles and small vesicles. To date, small-angle X-ray scattering is the only method to identify bicontinuous lipid cubic phases. To explore unique NMR signatures of lipid cubic phases, we first describe the orientation distribution of lipid molecules in cubic phases and simulate the static 31P chemical shift lineshapes of oriented cubic-phase membranes in the limit of slow lateral diffusion. We then show that 31P T2 relaxation times differ significantly between isotropic micelles and cubic-phase membranes: the latter exhibit two-orders-of magnitude shorter T2 relaxation times. These differences are explained by the different timescales of lipid lateral diffusion on the cubic-phase surface versus the timescales of micelle tumbling. Using this relaxation NMR approach, we investigated a DOPE membrane containing the transmembrane domain (TMD) of a viral fusion protein. The static 31P spectrum of DOPE shows an isotropic peak, whose T2 relaxation times correspond to that of a cubic phase. Thus, the viral fusion protein TMD induces negative Gaussian curvature, which is an intrinsic characteristic of cubic phases, to the DOPE membrane. This curvature induction has important implications to the mechanism of virus-cell fusion. This study establishes a simple NMR diagnostic probe of lipid cubic phases, which is expected to be useful for studying many protein-induced membrane remodeling phenomena in biology

  2. Sum frequency generation and solid-state NMR study of the structure, orientation, and dynamics of polystyrene-adsorbed peptides

    PubMed Central

    Weidner, Tobias; Breen, Nicholas F.; Li, Kun; Drobny, Gary P.; Castner, David G.

    2010-01-01

    The power of combining sum frequency generation (SFG) vibrational spectroscopy and solid-state nuclear magnetic resonance (ssNMR) spectroscopy to quantify, with site specificity and atomic resolution, the orientation and dynamics of side chains in synthetic model peptides adsorbed onto polystyrene (PS) surfaces is demonstrated in this study. Although isotopic labeling has long been used in ssNMR studies to site-specifically probe the structure and dynamics of biomolecules, the potential of SFG to probe side chain orientation in isotopically labeled surface-adsorbed peptides and proteins remains largely unexplored. The 14 amino acid leucine-lysine peptide studied in this work is known to form an α-helical secondary structure at liquid-solid interfaces. Selective, individual deuteration of the isopropyl group in each leucine residue was used to probe the orientation and dynamics of each individual leucine side chain of LKα14 adsorbed onto PS. The selective isotopic labeling methods allowed SFG analysis to determine the orientations of individual side chains in adsorbed peptides. Side chain dynamics were obtained by fitting the deuterium ssNMR line shape to specific motional models. Through the combined use of SFG and ssNMR, the dynamic trends observed for individual side chains by ssNMR have been correlated with side chain orientation relative to the PS surface as determined by SFG. This combination provides a more complete and quantitative picture of the structure, orientation, and dynamics of these surface-adsorbed peptides than could be obtained if either technique were used separately. PMID:20628016

  3. A solid state NMR study of layered double hydroxides intercalated with para-amino salicylate, a tuberculosis drug.

    PubMed

    Jensen, Nicholai Daugaard; Bjerring, Morten; Nielsen, Ulla Gro

    2016-09-01

    Para-amino salicylate (PAS), a tuberculosis drug, was intercalated in three different layered double hydroxides (MgAl, ZnAl, and CaAl-LDH) and the samples were studied by multi-nuclear ((1)H, (13)C, and (27)Al) solid state NMR (SSNMR) spectroscopy in combination with powder X-ray diffraction (PXRD), elemental analysis and IR-spectroscopy to gain insight into the bulk and atomic level structure of these LDHs especially with a view to the purity of the LDH-PAS materials and the concentration of impurities. The intercalations of PAS in MgAl-, ZnAl-, and CaAl-LDH's were confirmed by (13)C SSNMR and PXRD. Moreover, (13)C MAS NMR and infrared spectroscopy show that PAS did not decompose during synthesis. Large amounts (20-41%) of amorphous aluminum impurities were detected in the structure using (27)Al single pulse and 3QMAS NMR spectra, which in combination with (1)H single and double quantum experiments also showed that the M(II):Al ratio was higher than predicted from the bulk metal composition of MgAl-PAS and ZnAl-PAS. Moreover, the first high-resolution (1)H SSNMR spectra of a CaAl LDH is reported and assigned using (1)H single and double quantum experiments in combination with (27)Al{(1)H} HETCOR.

  4. Synthesis and evaluation of nitroxide-based oligoradicals for low-temperature dynamic nuclear polarization in solid state NMR.

    PubMed

    Yau, Wai-Ming; Thurber, Kent R; Tycko, Robert

    2014-07-01

    We describe the synthesis of new nitroxide-based biradical, triradical, and tetraradical compounds and the evaluation of their performance as paramagnetic dopants in dynamic nuclear polarization (DNP) experiments in solid state nuclear magnetic resonance (NMR) spectroscopy with magic-angle spinning (MAS). Under our experimental conditions, which include temperatures in the 25-30 K range, a 9.4 T magnetic field, MAS frequencies of 6.2-6.8 kHz, and microwave irradiation at 264.0 GHz from a 800 mW extended interaction oscillator source, the most effective compounds are triradicals that are related to the previously-described compound DOTOPA-TEMPO (see Thurber et al., 2010), but have improved solubility in glycerol/water solvent near neutral pH. Using these compounds at 30 mM total nitroxide concentration, we observe DNP enhancement factors of 92-128 for cross-polarized (13)C NMR signals from (15)N,(13)C-labeled melittin in partially protonated glycerol/water, and build-up times of 2.6-3.8s for (1)H spin polarizations. Net sensitivity enhancements with biradical and tetraradical dopants, taking into account absolute (13)C NMR signal amplitudes and build-up times, are approximately 2-4 times lower than with the best triradicals. Published by Elsevier Inc.

  5. Synthesis and evaluation of nitroxide-based oligoradicals for low-temperature dynamic nuclear polarization in solid state NMR

    PubMed Central

    Yau, Wai-Ming; Thurber, Kent R.; Tycko, Robert

    2014-01-01

    We describe the synthesis of new nitroxide-based biradical, triradical, and tetraradical compounds and the evaluation of their performance as paramagnetic dopants in dynamic nuclear polarization (DNP) experiments in solid state nuclear magnetic resonance (NMR) spectroscopy with magic-angle spinning (MAS). Under our experimental conditions, which include temperatures in the 25–30 K range, a 9.4 T magnetic field, MAS frequencies of 6.2–6.8 kHz, and microwave irradiation at 264.0 GHz from a 800 mW extended interaction oscillator source, the most effective compounds are triradicals that are related to the previously-described compound DOTOPA-TEMPO (see Thurber et al., 2010), but have improved solubility in glycerol/water solvent near neutral pH. Using these compounds at 30 mM total nitroxide concentration, we observe DNP enhancement factors of 92–128 for cross-polarized 13C NMR signals from 15N,13C-labeled melittin in partially protonated glycerol/water, and build-up times of 2.6–3.8 s for 1H spin polarizations. Net sensitivity enhancements with biradical and tetraradical dopants, taking into account absolute 13C NMR signal amplitudes and build-up times, are approximately 2–4 times lower than with the best triradicals. PMID:24887201

  6. Hydration water dynamics in bovine serum albumin at low temperatures as studied by deuterium solid-state NMR

    NASA Astrophysics Data System (ADS)

    Miyatou, Tatsuya; Araya, Takashi; Ohashi, Ryutaro; Ida, Tomonori; Mizuno, Motohiro

    2016-10-01

    Solid state 2H NMR was used to investigate changes in the structure and dynamics of hydration waters of bovine serum albumin (BSA) due to glass transitions. The 2H NMR spectra were separated into fast and slow components based on differences in spin-lattice relaxation time T1. The fast components corresponded to water molecules interacting with protein while the slow components were the water molecules similar to bulk water and deuterons of the protein backbone. Simulation analysis of the 2H NMR spectra of the fast components was used to assess the mode and rate of motions of hydration waters around the protein. At low temperatures, the water molecules underwent a 180° flip and slow reorientation in the tetrahedral sites. The distribution of the rate of the 180° flip and the D-O-D angle of water molecules were clarified. The distribution of the D-O-D angle of water molecules spread with decreasing temperature. The marked slowing down in the reorientation of water molecules was observed at a glass transition of around 200 K, which is linked to the disordered region of the protein. In contrast, the 180° flip of water molecules occurred frequently, even below 200 K. A freeze of the 180° flip of water molecules was observed around the glass transition temperature of 110 K, where primary hydrate water formed a direct hydrogen bond with the protein, making it perfectly immobile.

  7. Unlocking the molecular structure of fungal melanin using 13C biosynthetic labeling and solid-state NMR.

    PubMed

    Tian, Shiying; Garcia-Rivera, Javier; Yan, Bin; Casadevall, Arturo; Stark, Ruth E

    2003-07-15

    Melanins are enigmatic pigments found in all biological kingdoms that are associated with a variety of functions, including microbial virulence. Despite being ubiquitous in nature, melanin pigments have long resisted atomic-level structural examination because of their insolubility and amorphous organization. Cryptococcus neoformans is a human pathogenic fungus that melanizes only when provided with exogenous substrate, thus offering a unique system for exploring questions related to melanin structure at the molecular level. We have exploited the requirement for exogenous substrate in melanin synthesis as well as the capabilities of high-resolution solid-state nuclear magnetic resonance (NMR) to establish the predominantly aliphatic composition of l-dopa melanin and to introduce (13)C labels that permit the identification of proximal carbons in the developing biopolymer. By swelling solid melanin samples in organic solvents and using two-dimensional heteronuclear NMR in conjunction with magic-angle spinning, we have identified chemical bonding patterns typical of alkane, alkene, alcohol, ketone, ester, and indole functional groups. These findings demonstrate the feasibility of a novel approach to determining the structure of melanin using metabolic labeling and NMR spectroscopy.

  8. Molecular composition of recycled organic wastes, as determined by solid-state {sup 13}C NMR and elemental analyses

    SciTech Connect

    Eldridge, S.M.; Chen, C.R.; Xu, Z.H.; Nelson, P.N.; Boyd, S.E.; Meszaros, I.; Chan, K.Y.

    2013-11-15

    Highlights: • Model estimated the molecular C components well for most RO wastes. • Molecular nature of organic matter in RO wastes varied widely. • Molecular composition by NMR modelling preferable to extraction techniques. • Some model shortcomings in estimating molecular composition of biochars. • Waste molecular composition important for carbon/nutrient outcomes in soil. - Abstract: Using solid state {sup 13}C NMR data and elemental composition in a molecular mixing model, we estimated the molecular components of the organic matter in 16 recycled organic (RO) wastes representative of the major materials generated in the Sydney basin area. Close correspondence was found between the measured NMR signal intensities and those predicted by the model for all RO wastes except for poultry manure char. Molecular nature of the organic matter differed widely between the RO wastes. As a proportion of organic C, carbohydrate C ranged from 0.07 to 0.63, protein C from <0.01 to 0.66, lignin C from <0.01 to 0.31, aliphatic C from 0.09 to 0.73, carbonyl C from 0.02 to 0.23, and char C from 0 to 0.45. This method is considered preferable to techniques involving imprecise extraction methods for RO wastes. Molecular composition data has great potential as a predictor of RO waste soil carbon and nutrient outcomes.

  9. Expression, Functional Characterization, and Solid-State NMR Investigation of the G Protein-Coupled GHS Receptor in Bilayer Membranes

    PubMed Central

    Schrottke, Stefanie; Kaiser, Anette; Vortmeier, Gerrit; Els-Heindl, Sylvia; Worm, Dennis; Bosse, Mathias; Schmidt, Peter; Scheidt, Holger A.; Beck-Sickinger, Annette G.; Huster, Daniel

    2017-01-01

    The expression, functional reconstitution and first NMR characterization of the human growth hormone secretagogue (GHS) receptor reconstituted into either DMPC or POPC membranes is described. The receptor was expressed in E. coli. refolded, and reconstituted into bilayer membranes. The molecule was characterized by 15N and 13C solid-state NMR spectroscopy in the absence and in the presence of its natural agonist ghrelin or an inverse agonist. Static 15N NMR spectra of the uniformly labeled receptor are indicative of axially symmetric rotational diffusion of the G protein-coupled receptor in the membrane. In addition, about 25% of the 15N sites undergo large amplitude motions giving rise to very narrow spectral components. For an initial quantitative assessment of the receptor mobility, 1H-13C dipolar coupling values, which are scaled by molecular motions, were determined quantitatively. From these values, average order parameters, reporting the motional amplitudes of the individual receptor segments can be derived. Average backbone order parameters were determined with values between 0.56 and 0.69, corresponding to average motional amplitudes of 40–50° of these segments. Differences between the receptor dynamics in DMPC or POPC membranes were within experimental error. Furthermore, agonist or inverse agonist binding only insignificantly influenced the average molecular dynamics of the receptor. PMID:28387359

  10. Investigating miscibility and molecular mobility of nifedipine-PVP amorphous solid dispersions using solid-state NMR spectroscopy.

    PubMed

    Yuan, Xiaoda; Sperger, Diana; Munson, Eric J

    2014-01-06

    Solid-state NMR (SSNMR) (1)H T1 and T1ρ relaxation times were used to evaluate the miscibility of amorphous solid dispersions of nifedipine (NIF) and polyvinylpyrrolidone (PVP) prepared by three different methods: melt quenching in the typical lab setting, spray drying and melt quenching in the NMR rotor while spinning. Of the five compositions prepared by melt quenching in the lab setting, the 95:5 and 90:10 NIF:PVP (w:w) amorphous solid dispersions were not miscible while 75:25, 60:40, and 50:50 NIF:PVP dispersions were miscible by the (1)H T1ρ measurements. The domain size of the miscible systems was estimated to be less than 4.5 nm. Amorphous solid dispersions with composition of 90:10 NIF:PVP prepared by spray drying and melt quenching in the NMR rotor showed miscibility by (1)H T1ρ values. Variable-temperature SSNMR (1)H T1ρ relaxation measurements revealed a change in relaxation time at approximately 20 °C below Tg, suggesting increased molecular mobility above that temperature.

  11. Hydration properties of regioselectively etherified celluloses monitored by 2H and 13C solid-state MAS NMR spectroscopy.

    PubMed

    Larsen, Flemming H; Schöbitz, Michael; Schaller, Jens

    2012-06-20

    The hydration properties of 2,3-O-hydroxypropylcellulose (HPC) and 2,3-O-hydroxyethylcellulose (HEC) were analyzed by multi-nuclear solid-state MAS NMR spectroscopy. By 13C single-pulse (SP) MAS and cross-polarization (CP) MAS NMR, differences between the immobile regions and all parts of the polysaccharides were detected as a function of hydration. Complementary information about the water environments was observed by 2H MAS NMR. By this approach it was demonstrated that side chains in 2,3-O-HPC and 2,3-O-HEC were easier to hydrate than the cellulose backbone. Furthermore the motion of water was more restricted (slower) in 2,3-O-HPC than in 2,3-O-HEC. For both polysaccharides the hydration could be explained by a two-step process: in step one increased ordering of the immobile regions occurs after which the entire polymer is hydrated in step two. Copyright © 2012 Elsevier Ltd. All rights reserved.

  12. Reassessment of MxiH subunit orientation and fold within native Shigella T3SS needles using surface labelling and solid-state NMR

    PubMed Central

    Verasdonck, Joeri; Shen, Da-Kang; Treadgold, Alexander; Arthur, Christopher; Böckmann, Anja; Meier, Beat H.; Blocker, Ariel J.

    2015-01-01

    T3SSs are essential virulence determinants of many Gram-negative bacteria, used to inject bacterial effectors of virulence into eukaryotic host cells. Their major extracellular portion, a ∼50 nm hollow, needle-like structure, is essential to host cell sensing and the conduit for effector secretion. It is formed of a small, conserved subunit arranged as a helical polymer. The structure of the subunit has been studied by electron cryomicroscopy within native polymers and by solid-state NMR in recombinant polymers, yielding two incompatible atomic models. To resolve this controversy, we re-examined the native polymer used for electron cryomicroscopy via surface labelling and solid-state NMR. Our data show the orientation and overall fold of the subunit within this polymer is as established by solid-state NMR for recombinant polymers. PMID:26439285

  13. The use of 13C labeling to enhance the sensitivity of 13C solid-state CPMAS NMR to study polymorphism in low dose solid formulations.

    PubMed

    Booy, Kees-Jan; Wiegerinck, Peter; Vader, Jan; Kaspersen, Frans; Lambregts, Dorette; Vromans, Herman; Kellenbach, Edwin

    2005-02-01

    (13)C labeling was used to enhance the sensitivity of (13)C solid-state NMR to study the effect of tabletting on the polymorphism of a steroidal drug. The steroidal drug Org OD 14 was (13)C labeled and formulated into tablets containing only 0.5-2.5% active ingredient. The tablets were subsequently studied by solid-state (13)C CPMAS NMR. The crystalline form present in tablets could readily be analyzed in tablets. No change in crystalline form was observed as a result of formulation or in subsequent stability studies. Solid-state NMR in combination with (13)C labeling can, in suitable cases, be used as a strategy to study the effect of formulation on the polymorphism of low dose drugs.

  14. Solid State NMR Investigations of Chain Dynamics and Network Order in Model Poly(dimethylsiloxane) Elastomers

    SciTech Connect

    Lewicki, J P; Mayer, B P; Wilson, T S; Chinn, S C; Maxwell, R S

    2010-12-09

    This work is at a relatively early stage, however it has been demonstrated that we can reliably probe basic network architectures using the MQ-NMR technique. The initial results are in good agreement with what is known from standard network theory and will serve as a basis for the study of progressively increasing structural complexity in Siloxane network systems.

  15. Quantitative solid state NMR analysis of residues from acid hydrolysis of loblolly pine wood.

    PubMed

    Sievers, Carsten; Marzialetti, Teresita; Hoskins, Travis J C; Valenzuela Olarte, Mariefel B; Agrawal, Pradeep K; Jones, Christopher W

    2009-10-01

    The composition of solid residues from hydrolysis reactions of loblolly pine wood with dilute mineral acids is analyzed by (13)C Cross Polarization Magic Angle Spinning (CP MAS) NMR spectroscopy. Using this method, the carbohydrate and lignin fractions are quantified in less than 3h as compared to over a day using wet chemical methods. In addition to the quantitative information, (13)C CP MAS NMR spectroscopy provides information on the formation of additional extractives and pseudo lignin from the carbohydrates. Being a non-destructive technique, NMR spectroscopy provides unambiguous evidence of the presence of side reactions and products, which is a clear advantage over the wet chemical analytical methods. Quantitative results from NMR spectroscopy and proximate analysis are compared for the residues from hydrolysis of loblolly pine wood under 13 different conditions; samples were treated either at 150 degrees C or 200 degrees C in the presence of various acids (HCl, H(2)SO(4), H(3)PO(4), HNO(3) and TFA) or water. The lignin content determined by both methods differed on averaged by 2.9 wt% resulting in a standard deviation of 3.5 wt%. It is shown that solid degradation products are formed from saccharide precursors under harsh reaction conditions. These degradation reactions limit the total possible yield of monosaccharides from any subsequent reaction.

  16. A theoretical perspective on the accuracy of rotational resonance (R 2)-based distance measurements in solid-state NMR

    NASA Astrophysics Data System (ADS)

    Pandey, Manoj Kumar; Ramachandran, Ramesh

    2010-03-01

    The application of solid-state NMR methodology for bio-molecular structure determination requires the measurement of constraints in the form of 13C-13C and 13C-15N distances, torsion angles and, in some cases, correlation of the anisotropic interactions. Since the availability of structurally important constraints in the solid state is limited due to lack of sufficient spectral resolution, the accuracy of the measured constraints become vital in studies relating the three-dimensional structure of proteins to its biological functions. Consequently, the theoretical methods employed to quantify the experimental data become important. To accentuate this aspect, we re-examine analytical two-spin models currently employed in the estimation of 13C-13C distances based on the rotational resonance (R 2) phenomenon. Although the error bars for the estimated distances tend to be in the range 0.5-1.0 Å, R 2 experiments are routinely employed in a variety of systems ranging from simple peptides to more complex amyloidogenic proteins. In this article we address this aspect by highlighting the systematic errors introduced by analytical models employing phenomenological damping terms to describe multi-spin effects. Specifically, the spin dynamics in R 2 experiments is described using Floquet theory employing two different operator formalisms. The systematic errors introduced by the phenomenological damping terms and their limitations are elucidated in two analytical models and analysed by comparing the results with rigorous numerical simulations.

  17. Hydration properties and phosphorous speciation in native, gelatinized and enzymatically modified potato starch analyzed by solid-state MAS NMR.

    PubMed

    Larsen, Flemming H; Kasprzak, Mirosław M; Lærke, Helle N; Knudsen, Knud Erik B; Pedersen, Sven; Jørgensen, Anne S; Blennow, Andreas

    2013-09-12

    Hydration of granular, gelatinized and molecularly modified states of potato starch in terms of molecular mobility were analyzed by (13)C and (31)P solid-state MAS NMR. Gelatinization (GEL) tremendously reduced the immobile fraction compared to native (NA) starch granules. This effect was enhanced by enzyme-assisted catalytic branching with branching enzyme (BE) or combined BE and β-amylase (BB) catalyzed exo-hydrolysis. Carbons of the glycosidic α-1,6 linkages required high hydration rates before adopting uniform chemical shifts indicating solid-state disorder and poor water accessibility. Comparative analysis of wheat and waxy maize starches demonstrated that starches were similar upon gelatinization independent of botanical origin and that the torsion angles of the glycosidic linkages were averages of the crystalline A and B type structures. In starch suspension phosphorous in immobile regions was only observed in NA starch. Moreover phosphorous was observed in a minor pH-insensitive form and as major phosphate in hydrated GEL and BE starches.

  18. Solid-state NMR analysis of the {beta}-strand orientation of the protofibrils of amyloid {beta}-protein

    SciTech Connect

    Doi, Takashi; Masuda, Yuichi; Irie, Kazuhiro; Akagi, Ken-ichi; Monobe, Youko; Imazawa, Takayoshi; Takegoshi, K.

    2012-11-30

    Highlights: Black-Right-Pointing-Pointer The supramolecular structure of A{beta}42 protofibrils was analyzed by solid-state NMR. Black-Right-Pointing-Pointer The Ala-21 residue in the A{beta}42 protofibrils is included in a slightly disordered {beta}-strand. Black-Right-Pointing-Pointer The A{beta}42 protofibrils do not form intermolecular in-register parallel {beta}-sheets. -- Abstract: Alzheimer's disease (AD) is caused by abnormal deposition (fibrillation) of a 42-residue amyloid {beta}-protein (A{beta}42) in the brain. During the process of fibrillation, the A{beta}42 takes the form of protofibrils with strong neurotoxicity, and is thus believed to play a crucial role in the pathogenesis of AD. To elucidate the supramolecular structure of the A{beta}42 protofibrils, the intermolecular proximity of the Ala-21 residues in the A{beta}42 protofibrils was analyzed by {sup 13}C-{sup 13}C rotational resonance experiments in the solid state. Unlike the A{beta}42 fibrils, an intermolecular {sup 13}C-{sup 13}C correlation was not found in the A{beta}42 protofibrils. This result suggests that the {beta}-strands of the A{beta}42 protofibrils are not in an in-register parallel orientation. A{beta}42 monomers would assemble to form protofibrils with the {beta}-strand conformation, then transform into fibrils by forming intermolecular parallel {beta}-sheets.

  19. Solid state 13C NMR and FT-IR spectroscopy of the cocoon silk of two common spiders

    NASA Astrophysics Data System (ADS)

    Bramanti, Emilia; Catalano, Donata; Forte, Claudia; Giovanneschi, Mario; Masetti, Massimo; Veracini, Carlo Alberto

    2005-11-01

    The structure of the silk from cocoons of two common spiders, Araneus diadematus (family Araneidae) and Achaearanea tepidariorum (family Theridiidae) was investigated by means of 13C solid state NMR and FT-IR spectroscopies. The combined use of these two techniques allowed us to highlight differences in the two samples. The cocoon silk of Achaearanea tepidariorum is essentially constituted by helical and β-sheet structures, whereas that of Araneus diadematus shows a more complex structure, containing also β-strands and β-turns. Moreover, the former silk is essentially crystalline while the latter contains more mobile domains. The structural differences of the two cocoon silks are ascribed to the different habitat of the two species.

  20. The structure, dynamics and orientation of antimicrobial peptides in membranes by multidimensional solid-state NMR spectroscopy.

    PubMed

    Bechinger, B

    1999-12-15

    Linear peptide antibiotics have been isolated from amphibians, insects and humans and used as templates to design cheaper and more potent analogues for medical applications. Peptides such as cecropins or magainins are < or = 40 amino acids in length. Many of them have been prepared by solid-phase peptide synthesis with isotopic labels incorporated at selected sites. Structural analysis by solid-state NMR spectroscopy and other biophysical techniques indicates that these peptide antibiotics strongly interact with lipid membranes. In bilayer environments they exhibit amphipathic alpha-helical conformations and alignments of the helix axis parallel to the membrane surface. This contrasts the transmembrane orientations observed for alamethicin or gramicidin A. Models that have been proposed to explain the antibiotic and pore-forming activities of membrane-associated peptides, as well as other experimental results, include transmembrane helical bundles, wormholes, carpets, detergent-like effects or the in-plane diffusion of peptide-induced bilayer instabilities.

  1. 2D 31P solid state NMR spectroscopy, electronic structure and thermochemistry of PbP7

    NASA Astrophysics Data System (ADS)

    Benndorf, Christopher; Hohmann, Andrea; Schmidt, Peer; Eckert, Hellmut; Johrendt, Dirk; Schäfer, Konrad; Pöttgen, Rainer

    2016-03-01

    Phase pure polycrystalline PbP7 was prepared from the elements via a lead flux. Crystalline pieces with edge-lengths up to 1 mm were obtained. The assignment of the previously published 31P solid state NMR spectrum to the seven distinct crystallographic sites was accomplished by radio-frequency driven dipolar recoupling (RFDR) experiments. As commonly found in other solid polyphosphides there is no obvious correlation between the 31P chemical shift and structural parameters. PbP7 decomposes incongruently under release of phosphorus forming liquid lead as remainder. The thermal decomposition starts at T>550 K with a vapor pressure almost similar to that of red phosphorus. Electronic structure calculations reveal PbP7 as a semiconductor according to the Zintl description and clearly shows the stereo-active Pb-6s2 lone pairs in the electron localization function ELF.

  2. Cationic Membrane Peptides: Atomic-Level Insight of Structure-Activity Relationships from Solid-State NMR

    PubMed Central

    Su, Yongchao; Li, Shenhui; Hong, Mei

    2012-01-01

    Many membrane-active peptides, such as cationic cell-penetrating peptides (CPPs) and antimicrobial peptides (AMPs), conduct their biological functions by interacting with the cell membrane. The interactions of charged residues with lipids and water facilitate membrane insertion, translocation or disruption of these highly hydrophobic species. In this mini-review we will summarize high-resolution structural and dynamic findings towards the understanding of the structure-activity relationship of lipid membrane-bound CPPs and AMPs, as examples of the current development of solid-state NMR (SSNMR) techniques for studying membrane peptides. We will present the most recent atomic-resolution structure of the guanidinium-phosphate complex, as constrained from experimentally measured site-specific distances. These SSNMR results will be valuable specifically for understanding the intracellular translocation pathway of CPPs and antimicrobial mechanism of AMPs, and more generally broaden our insight into how cationic macromolecules interact with and cross the lipid membrane. PMID:23108593

  3. Easy-Going On-Spectrometer Optimisation of Phase Modulated Homonuclear Decoupling Sequences in Solid-State NMR

    NASA Astrophysics Data System (ADS)

    Grimminck, Dennis L. A. G.; Vasa, Suresh K.; Meerts, W. Leo; Kentgens, P. M.

    2011-06-01

    A global optimisation scheme for phase modulated proton homonuclear decoupling sequences in solid-state NMR is presented. Phase modulations, parameterised by DUMBO Fourier coefficients, were optimized using a Covariance Matrix Adaptation Evolution Strategies algorithm. Our method, denoted EASY-GOING homonuclear decoupling, starts with featureless spectra and optimises proton-proton decoupling, during either proton or carbon signal detection. On the one hand, our solutions closely resemble (e)DUMBO for moderate sample spinning frequencies and medium radio-frequency (rf) field strengths. On the other hand, the EASY-GOING approach resulted in a superior solution, achieving significantly better resolved proton spectra at very high 680 kHz rf field strength. N. Hansen, and A. Ostermeier. Evol. Comput. 9 (2001) 159-195 B. Elena, G. de Paepe, L. Emsley. Chem. Phys. Lett. 398 (2004) 532-538

  4. Solid-State NMR Studies of Fossil Fuels using One- and Two-Dimensional Methods at High Magnetic Field

    SciTech Connect

    Althaus, Stacey M.; Mao, Kanmi; Kennedy, Gordon J.; Pruski, Marek

    2012-06-24

    We examine the opportunities offered by advancements in solid-state NMR (SSNMR) methods, which increasingly rely on the use of high magnetic fields and fast magic angle spinning (MAS), in the studies of coals and other carbonaceous materials. The sensitivity of one- and two-dimensional experiments tested on several Argonne Premium coal samples is only slightly lower than that of traditional experiments performed at low magnetic fields in large MAS rotors, since higher receptivity per spin and the use of 1H detection of low-gamma nuclei can make up for most of the signal loss due to the small rotor size. The advantages of modern SSNMR methodology in these studies include improved resolution, simplicity of pulse sequences, and the possibility of using J-coupling during mixing.

  5. Solid-state proton NMR of paramagnetic metal complexes: DANTE spin echoes for selective excitation in inhomogeneously broadened lines

    NASA Astrophysics Data System (ADS)

    Carnevale, Diego; Perez Linde, A. J.; Bauer, Gerald; Bodenhausen, Geoffrey

    2013-08-01

    The paramagnetic complex bis(oxazolinylphenyl)amine-Fe(III)Cl2 is investigated by means of solid-state proton NMR at 18.8 T (800 MHz) using magic-angle spinning at 65 kHz. Spin echoes that are excited and refocused by combs of rotor-synchronized pulses in the manner of 'Delays Alternating with Nutation for Tailored Excitation' (DANTE) allow one to characterize different chemical environments that severely overlap in conventional MAS spectra. Such sequences combine two apparently contradictory features: an overall bandwidth exceeding several MHz, and very selective irradiation of a few kHz within inhomogeneously broadened sidebands. The experimental hyperfine interactions correlate well with DFT calculations.

  6. A general theoretical description of the influence of isotropic chemical shift in dipolar recoupling experiments for solid-state NMR

    NASA Astrophysics Data System (ADS)

    Shankar, Ravi; Ernst, Matthias; Madhu, P. K.; Vosegaard, Thomas; Nielsen, Niels Chr.; Nielsen, Anders B.

    2017-04-01

    We present a general theoretical description that allows us to describe the influence of isotropic chemical shift in homonuclear and heteronuclear dipolar recoupling experiments in magic-angle-spinning solid-state NMR. Through a transformation of the Hamiltonian into an interaction frame with the combined radio-frequency irradiation and the isotropic chemical shift, we determine an effective Hamiltonian to first order with respect to the relevant internal nuclear spin interactions. This unravels the essential resonance conditions for efficient dipolar recoupling. Furthermore, we propose how to handle situations where the resonance conditions are not exactly fulfilled. To verify the general theoretical description, we compare numerical simulations using a time-sliced time-dependent Hamiltonian with simulations using the calculated effective Hamiltonian for propagation. The comparisons are exemplified for the homonuclear dipolar recoupling experiments C 721 and POST-C 721 .

  7. Investigation of gamma-irradiated vegetable seeds with high-resolution solid-state 13C NMR.

    PubMed

    Bardet, Michel; Maron, Sébastien; Foray, Marie Françoise; Berger, Maurice; Guillermo, Armel

    2004-04-01

    13C solid-state NMR was used to investigate the effects of gamma radiation on vegetable seeds, Pisum sativum and Latuca sativa, at absorbed doses that inhibit their germination. By combining single-pulse excitation and cross-polarization experiments under magic angle spinning, both liquid and solid domains of seeds can be characterized. We showed that the liquid domains, mostly made of triacylglycerols (TAG), of vegetable seeds are not sensitive to radiation. The main structural changes have been observed in the embryonic axes of seeds when the seeds are water-imbibed before irradiation. These results rule out a starting hypothesis concerning the potential role of TAG contained in oil bodies as a potential source of aldehydes that could further react with DNA moiety.

  8. Homogeneous nanoparticles to enhance the efficiency of a hydrophobic drug, antihyperlipidemic probucol, characterized by solid-state NMR.

    PubMed

    Io, Takeshi; Fukami, Toshiro; Yamamoto, Kazutoshi; Suzuki, Toyofumi; Xu, Jiadi; Tomono, Kazuo; Ramamoorthy, Ayyalusamy

    2010-02-01

    A low absorption in the gastrointestinal tract of hydrophobic pharmaceutical compounds in use today considerably limits their bioavailability, and therefore they are taken in large doses in order to reach the therapeutic plasma concentration, which inevitably results in undesired side effects. In this study, we demonstrate a new nanoparticle approach to overcome this problem, and our experimental results show that this approach has a high efficiency of drug loading and is easily adaptable to industrial scale. Characterization of nanoparticles containing a cholesterol-lowering hydrophobic drug, probucol, using a variety of biophysical techniques revealed higher homogeneity of these particles compared to those prepared using other approaches. Intermolecular interactions of these nanoparticles are probed at high resolution by magic angle spinning solid-state NMR experiments.

  9. Unique molecular dynamics of structural elements in an asymmetric Janus bisamide supramolecule characterized by solid-state NMR.

    PubMed

    Chen, Wei; Sun, Hao-Jan; Miyoshi, Toshikazu

    2013-10-31

    An asymmetric tapered Janus bisamide supramolecule consisting of 1,4-bis[3,4,5-tris(alkan-1-yloxy)benzamido]benzene bisamide (abbreviated as C22PhBAEO3) can possess three-dimensional (3D) long-range order under mild thermal treatment conditions. To understand its structural formation and unique phase-transition processes, the locally detailed structure and molecular dynamics of its structural elements in disordered and ordered phases of C22PhBAEO3 were investigated using various solid-state (SS) NMR techniques at the atomic level. On the basis of the determined conformations and packing structures of the alkyl chains in ordered and disordered crystalline phases, along with the geometry and kinetic parameters of the structural elements' dynamics, this study addresses the self-assembly, the phase-transition mechanisms, and the relationship between the structure and dynamics of these asymmetric Janus bisamide supramolecules.

  10. Proton-detected solid-state NMR spectroscopy of a zinc diffusion facilitator protein in native nanodiscs

    PubMed Central

    Bersch, Beate; Dörr, Jonas M.; Hessel, Audrey; Killian, J. Antoinette; Schanda, Paul

    2017-01-01

    The structure, dynamics and function of membrane proteins are intimately linked to the properties of the membrane environment in which the proteins are embedded. For structural and biophysical characterization, membrane proteins generally need to be extracted from the membrane, and reconstituted in a suitable membrane-mimicking environment. Ensuring functional and structural integrity in these environments is often a major concern. The styrene/maleic acid co-polymer has recently been shown to be able to extract lipid/membrane protein patches directly from native membranes, forming nanosize discoidal proteolipid particles, also referred to as native nanodiscs. Here we show, for the first time, that high-resolution solid-state NMR spectra can be obtained from an integral membrane protein in native nanodiscs, as exemplified with the 2 x 34 kDa-large bacterial cation diffusion facilitator CzcD from Cupriavidus metallidurans CH34. PMID:28128538

  11. An efficient method and device for transfer of semisolid materials into solid-state NMR spectroscopy rotors

    NASA Astrophysics Data System (ADS)

    Hisao, Grant S.; Harland, Michael A.; Brown, Robert A.; Berthold, Deborah A.; Wilson, Thomas E.; Rienstra, Chad M.

    2016-04-01

    The study of mass-limited biological samples by magic angle spinning (MAS) solid-state NMR spectroscopy critically relies upon the high-yield transfer of material from a biological preparation into the MAS rotor. This issue is particularly important for maintaining biological activity and hydration of semi-solid samples such as membrane proteins in lipid bilayers, pharmaceutical formulations, microcrystalline proteins and protein fibrils. Here we present protocols and designs for rotor-packing devices specifically suited for packing hydrated samples into Pencil-style 1.6 mm, 3.2 mm standard, and 3.2 mm limited speed MAS rotors. The devices are modular and therefore readily adaptable to other rotor and/or ultracentrifugation tube geometries.

  12. Effect of Ca:Mg ratio on precipitated P species identified using 31P solid state NMR

    NASA Astrophysics Data System (ADS)

    Manimel Wadu, M.

    2009-04-01

    M.C.W. Manimel Wadu1, O.O Akinremi1, S. Kroeker2 1Department of Soil Science, University of Manitoba, Winnipeg, R3T 2N2, Canada 2Department of Chemistry, University of Manitoba, Winnipeg, R3T 2N2, Canada Agronomic efficiency of added P fertilizer is reduced by the precipitation reactions with the exchangeable Ca and Mg in calcareous soils. We hypothesized that the ratio of Ca to Mg on the soil exchange complex will affect the species of P that is precipitated and its solubility in the soil. A laboratory experiment was conducted using a model calcareous soil system which was composed of resin (Amberlite IRP69) and sand coated with CaCO3 packed into a column. The resin was pre saturated with Ca and Mg in order to achieve five different saturation ratios of Ca:Mg approximately as 100:0, 70:30, 50:50, 30:70 and 0:100. Monoammonium Phosphate was applied to the soil surface to simulate one-dimensional diffusive transport. The column was then incubated for 2 weeks. Chemical analysis for water and acid soluble P, pH, NH4, Ca and Mg was performed on 2mm sections of the soil to a depth of 10 cm. This paper will present and discuss the distribution of P along the soil column. Unlike similar studies that have speculated on the precipitation of P, this study will identify and quantify the P species that is formed using 31P solid state NMR technique. Such knowledge will be helpful in understanding the effect of Ca and Mg on P availability in calcareous system and the role of each cation on P precipitation. Key words: P fertilizers, Ca, Mg, model system, solid state NMR

  13. Characterizing the secondary protein structure of black widow dragline silk using solid-state NMR and X-ray diffraction.

    PubMed

    Jenkins, Janelle E; Sampath, Sujatha; Butler, Emily; Kim, Jihyun; Henning, Robert W; Holland, Gregory P; Yarger, Jeffery L

    2013-10-14

    This study provides a detailed secondary structural characterization of major ampullate dragline silk from Latrodectus hesperus (black widow) spiders. X-ray diffraction results show that the structure of black widow major ampullate silk fibers is comprised of stacked β-sheet nanocrystallites oriented parallel to the fiber axis and an amorphous region with oriented (anisotropic) and isotropic components. The combination of two-dimensional (2D) (13)C-(13)C through-space and through-bond solid-state NMR experiments provide chemical shifts that are used to determine detailed information about the amino acid motif secondary structure in black widow spider dragline silk. Individual amino acids are incorporated into different repetitive motifs that make up the majority of this protein-based biopolymer. From the solid-state NMR measurements, we assign distinct secondary conformations to each repetitive amino acid motif and, hence, to the amino acids that make up the motifs. Specifically, alanine is incorporated in β-sheet (poly(Alan) and poly(Gly-Ala)), 3(1)-helix (poly(Gly-Gly-Xaa), and α-helix (poly(Gln-Gln-Ala-Tyr)) components. Glycine is determined to be in β-sheet (poly(Gly-Ala)) and 3(1)-helical (poly(Gly-Gly-X(aa))) regions, while serine is present in β-sheet (poly(Gly-Ala-Ser)), 3(1)-helix (poly(Gly-Gly-Ser)), and β-turn (poly(Gly-Pro-Ser)) structures. These various motif-specific secondary structural elements are quantitatively correlated to the primary amino acid sequence of major ampullate spidroin 1 and 2 (MaSp1 and MaSp2) and are shown to form a self-consistent model for black widow dragline silk.

  14. Structure and dynamics in the methylated exopyridine anthracene rotaxane: 13C, 1H and 19F solid-state NMR studies

    NASA Astrophysics Data System (ADS)

    Bourdon, X.; Leupold, J.; Mehring, M.; Thies, J.; Kidd, T.; Loontjens, T.

    2000-11-01

    We report on the structural and dynamic characterization by solid state NMR of a new rotaxane consisting of a thread molecule enclosed by a macrocycle, which can eventually shuttle or rotate along/around the thread. Different kinds of slow and fast motions are detected in the methylated exopyridine anthracene rotaxane by 1H, 13C and 19F relaxation time versus temperature measurements. Analysis of the proton decoupled and temperature dependent 19F NMR spectra gives some indications of the possible motions of the macrocycle and breaking of the hydrogen bond in the solid-state at temperatures above 360 K.

  15. Solid-state NMR of nanomachines involved in photosynthetic energy conversion.

    PubMed

    Alia, A; Buda, Francesco; de Groot, Huub J M; Matysik, Jörg

    2013-01-01

    Magic-angle spinning NMR, often in combination with photo-CIDNP, is applied to determine how photosynthetic antennae and reaction centers are activated in the ground state to perform their biological function upon excitation by light. Molecular modeling resolves molecular mechanisms by way of computational integration of NMR data with other structure-function analyses. By taking evolutionary historical contingency into account, a better biophysical understanding is achieved. Chlorophyll cofactors and proteins go through self-assembly trajectories that are engineered during evolution and lead to highly homogeneous protein complexes optimized for exciton or charge transfer. Histidine-cofactor interactions allow biological nanomachines to lower energy barriers for light harvesting and charge separation in photosynthetic energy conversion. In contrast, in primordial chlorophyll antenna aggregates, excessive heterogeneity is paired with much less specific characteristics, and both exciton and charge-transfer character are encoded in the ground state.

  16. Cation substitution in β-tricalcium phosphate investigated using multi-nuclear, solid-state NMR

    NASA Astrophysics Data System (ADS)

    Grigg, Andrew T.; Mee, Martin; Mallinson, Phillip M.; Fong, Shirley K.; Gan, Zhehong; Dupree, Ray; Holland, Diane

    2014-04-01

    The substitution of aluminium, gallium and sodium cations into β-tricalcium phosphate (β-TCP; Ca3(PO4)2) has been investigated, and the Ca sites involved successfully determined, using a combination of 1D 31P, 27Al, 71Ga, 23Na and 43Ca (natural abundance) NMR and 2D 27Al{31P}, 71Ga{31P} and 23Na{31P} rotary-resonance-recoupled heteronuclear multiple-quantum correlation (R3-HMQC) NMR. Over the compositional range studied, substitution of Ca2+ by Al3+ or Ga3+ was observed only on the Ca(5) site, whilst substitution by Na+ was confined to the Ca(4) site. Some AlPO4 or GaPO4 second phase was observed at the highest doping levels in the Al3+ and Ga3+ substituted samples.

  17. Characterization of pyrogenic organic matter by 2-dimenstional HETeronucleus CORelation solid-state 13C NMR (HETCOR) spectroscopy

    NASA Astrophysics Data System (ADS)

    Knicker, Heike

    2016-04-01

    During the last years, increasing evidences are provided that the common view of charcoal as a polyaromatic network is too much simplified. Experiments with model compounds indicated that it represents a heterogeneous mixture of thermally altered biomacromolecules with N, O and likely also S substitutions as common features. If produced from a N-rich feedstock, the so called black nitrogen (BN) has to be considered as an integral part of the aromatic charcoal network. In order to study this network one-dimensional (1D) solid-state nuclear magnetic resonance (NMR) spectroscopy is often applied. However, this technique suffers from broad resonance lines and low resolution. Applying 2D techniques can help but until recently, this was unfeasible for natural organic matter (NOM) due to sensitivity problems and the high complexity of the material. On the other hand, during the last decade, the development of stronger magnetic field instruments and advanced pulse sequences has put them into reach for NOM research. Although 2D NMR spectroscopy has many different applications, all pulse sequences are based on the introduction of a preparation time during which the magnetization of a spin system is adjusted into a state appropriate to whatever properties are to be detected in the indirect dimension. Then, the spins are allowed to evolve with the given conditions and after their additional manipulation during a mixing period the modulated magnetization is detected. Assembling several 1D spectra with incrementing evolution time creates a data set which is two-dimensional in time (t1, t2). Fourier transformation of both dimensions leads to a 2D contour plot correlating the interactions detected in the indirect dimension t1 with the signals detected in the direct dimension t2. The so called solid-state heteronuclear correlation (HETCOR) NMR spectroscopy represents a 2D technique allows the determination which protons are interacting with which carbons. In the present work this

  18. Improving resolution in proton solid-state NMR by removing nitrogen-14 residual dipolar broadening

    NASA Astrophysics Data System (ADS)

    Stein, Robin S.; Elena, Bénédicte; Emsley, Lyndon

    2008-06-01

    Residual dipolar coupling between quadrupolar and other nuclei under MAS has not usually been thought to be important in high field NMR spectroscopy. We show that coupling to 14N broadens 1H lineshapes significantly even at 11.7 T, and that we can decouple 14N from 1H during 1H homonuclear decoupling to successfully improve 1H resolution. The method used for decoupling is the application of evenly spaced pulses to the quadrupolar nucleus.

  19. Protein fold determined by paramagnetic magic-angle spinning solid-state NMR spectroscopy

    PubMed Central

    Sengupta, Ishita; Nadaud, Philippe S.; Helmus, Jonathan J.; Schwieters, Charles D.; Jaroniec, Christopher P.

    2012-01-01

    Biomacromolecules that are challenging for the usual structural techniques can be studied with atomic resolution by solid-state nuclear magnetic resonance. However, the paucity of >5 Å distance restraints, traditionally derived from measurements of magnetic dipole-dipole couplings between protein nuclei, is a major bottleneck that hampers such structure elucidation efforts. Here we describe a general approach that enables the rapid determination of global protein fold in the solid phase via measurements of nuclear paramagnetic relaxation enhancements (PREs) in several analogs of the protein of interest containing covalently-attached paramagnetic tags, without the use of conventional internuclear distance restraints. The method is demonstrated using six cysteine-EDTA-Cu2+ mutants of the 56-residue B1 immunoglobulin-binding domain of protein G, for which ~230 longitudinal backbone 15N PREs corresponding to ~10-20 Å distances were obtained. The mean protein fold determined in this manner agrees with the X-ray structure with a backbone atom root-mean-square deviation of 1.8 Å. PMID:22522262

  20. Membrane proteins in their native habitat as seen by solid-state NMR spectroscopy

    PubMed Central

    Brown, Leonid S; Ladizhansky, Vladimir

    2015-01-01

    Membrane proteins play many critical roles in cells, mediating flow of material and information across cell membranes. They have evolved to perform these functions in the environment of a cell membrane, whose physicochemical properties are often different from those of common cell membrane mimetics used for structure determination. As a result, membrane proteins are difficult to study by traditional methods of structural biology, and they are significantly underrepresented in the protein structure databank. Solid-state Nuclear Magnetic Resonance (SSNMR) has long been considered as an attractive alternative because it allows for studies of membrane proteins in both native-like membranes composed of synthetic lipids and in cell membranes. Over the past decade, SSNMR has been rapidly developing into a major structural method, and a growing number of membrane protein structures obtained by this technique highlights its potential. Here we discuss membrane protein sample requirements, review recent progress in SSNMR methodologies, and describe recent advances in characterizing membrane proteins in the environment of a cellular membrane. PMID:25973959

  1. A unified heteronuclear decoupling strategy for magic-angle-spinning solid-state NMR spectroscopy

    SciTech Connect

    Equbal, Asif; Bjerring, Morten; Nielsen, Niels Chr. E-mail: ncn@inano.au.dk; Madhu, P. K. E-mail: ncn@inano.au.dk

    2015-05-14

    A unified strategy of two-pulse based heteronuclear decoupling for solid-state magic-angle spinning nuclear magnetic resonance is presented. The analysis presented here shows that different decoupling sequences like two-pulse phase-modulation (TPPM), X-inverse-X (XiX), and finite pulse refocused continuous wave (rCW{sup A}) are basically specific solutions of a more generalized decoupling scheme which incorporates the concept of time-modulation along with phase-modulation. A plethora of other good decoupling conditions apart from the standard, TPPM, XiX, and rCW{sup A} decoupling conditions are available from the unified decoupling approach. The importance of combined time- and phase-modulation in order to achieve the best decoupling conditions is delineated. The consequences of different indirect dipolar interactions arising from cross terms comprising of heteronuclear and homonuclear dipolar coupling terms and also those between heteronuclear dipolar coupling and chemical-shift anisotropy terms are presented in order to unfold the effects of anisotropic interactions under different decoupling conditions. Extensive numerical simulation results are corroborated with experiments on standard amino acids.

  2. Solid state NMR methods for coal science. Progress report, July 1, 1985-September 30, 1985

    SciTech Connect

    Zilm, K.W.

    1986-02-01

    This report covers the progress made on the title project during the last quarter. During the last three months we have concentrated on further developing a new 2-D NMR method that should be useful for coals. As outlined in a previous report this new technique separates the contribution of methines, methylenes and methyl or quaternary carbons to the carbon-13 CPMAS spectra of coals. In contrast to the heteronuclear shift correlation method, which observes only protonated carbons, this method observes all carbon centers seen in a standard CPMAS spectrum. The method has been successfully applied to polystyrene in which a methylene and methine resonance overlap. In this system we have a worst case as the interpretation is somewhat complicated by molecular motion in the solid. The results are still close to quantitative even with this complication. We have also investigated a new series of pulse sequences that we call Echo train NMR that were discovered in our earlier studies on decoupling methods. These sequences will be principally useful in enhancing the sensitivity of powder NMR spectra. In many cases the peak signal to noise of powder spectra can be enhanced by factors of up to 100. 6 figs.

  3. Probing the environment of neurotensin whilst bound to the neurotensin receptor by solid state NMR.

    PubMed

    Williamson, P T F; Bains, S; Chung, C; Cooke, R; Watts, A

    2002-05-08

    A functionally active analogue of neurotensin, neurotensin(8-13), has been observed whilst bound to the agonist-binding site of the rat neurotensin receptor by nuclear magnetic resonance (NMR). Through the application of slow magic angle sample spinning and high-power proton decoupling, sufficient resolution and sensitivity were obtained in the carbon-13 spectrum to allow an assignment of many of the side chain resonances arising from uniformly carbon-13/nitrogen-15-labelled neurotensin(8-13) whilst bound to the neurotensin receptor. Significant perturbations in carbon-13 chemical shift were observed upon the binding of the neurotensin(8-13) to the receptor. Most importantly significant shifts were observed in both the carboxy terminus and tyrosine side chain of the neurotensin(8-13), suggesting that these sites are important in the interaction of the neurotensin with the agonist-binding site on the neurotensin receptor. Conversely, no perturbations were observed for the carbon-13 sites within the guanidinium groups of the arginine side chains, indicating little interaction with the receptor-binding site, or a shielding of the local environment by the surrounding nitrogen atoms. These NMR observations lend further support to previous structure-activity studies, site-directed mutagenesis and modelling studies of the agonist-binding site of the neurotensin receptor, from which the same specific residues for which NMR perturbations were observed are important for neurotensin receptor activation by neurotensin.

  4. Conformational analysis of opioid peptides in the solid states and the membrane environments by NMR spectroscopy.

    PubMed

    Naito, Aira; Nishimura, Katsuyuki

    2004-01-01

    Determination of conformations and structures of opioid peptides in the membrane environments is an essential step to understand the action of the peptide to the specialized receptors. This information not only gains insight into the structure-function relationship of opioid peptide but also gives proper guidelines to design a new drug to have same neuroendocrine functions. This review provides the structural studies of three types of opioid peptide families such as enkephalin, beta-endorphin and dynorphin in the solid states and the membrane environments. The structures of enkephalins show that they take beta-bend, extended and double beta-bend structures in the crystals. Moreover, enkephalin molecules take a variety of structures in the crystals and are easily converted to the other structures with slightly different torsion angles. On the other hand, beta-bend structures are mostly seen in the membrane environments. Membrane bound structure of dynorphin shows that the N-terminus forms alpha-helical structure and is inserted into the membrane with the helical axis almost perpendicular to the membrane surface. It is discussed that the helical region of the extracellular loop II of the kappa-opioid receptor may interact with the helical region of dynorphin with a high affinity in the membrane environments. beta-endorphin takes alpha-helical structure at N-terminus and the central regions and the rest of regions take unordered structure when the bind to the membrane. Since the membrane bound structures of opioid peptides differ from those of the solution states, membrane association is an important process for exerting the affinity and the selectivity to the specific opioid receptors.

  5. Solid-state NMR analysis of a complex crystalline phase of ronacaleret hydrochloride.

    PubMed

    Vogt, Frederick G; Williams, Glenn R; Strohmeier, Mark; Johnson, Matthew N; Copley, Royston C B

    2014-08-28

    A crystalline phase of the pharmaceutical compound ronacaleret hydrochloride is studied by solid-state nuclear magnetic resonance (SSNMR) spectroscopy and single-crystal X-ray diffraction. The crystal structure is determined to contain two independent cationic molecules and chloride anions in the asymmetric unit, which combine with the covalent structure of the molecule to yield complex SSNMR spectra. Experimental approaches based on dipolar correlation, chemical shift tensor analysis, and quadrupolar interaction analysis are employed to obtain detailed information about this phase. Density functional theory (DFT) calculations are used to predict chemical shielding and electric field gradient (EFG) parameters for comparison with experiment. (1)H SSNMR experiments performed at 16.4 T using magic-angle spinning (MAS) and homonuclear dipolar decoupling provide information about hydrogen bonding and molecular connectivity that can be related to the crystal structure. (19)F and (13)C assignments for the Z' = 2 structure are obtained using DFT calculations, (19)F homonuclear dipolar correlation, and (13)C-(19)F heteronuclear dipolar correlation experiments. (35)Cl MAS experiments at 16.4 T observe two chlorine sites that are assigned using calculated chemical shielding and EFG parameters. SSNMR dipolar correlation experiments are used to extract (1)H-(13)C, (1)H-(15)N, (1)H-(19)F, (13)C-(19)F, and (1)H-(35)Cl through-space connectivity information for many positions of interest. The results allow for the evaluation of the performance of a suite of SSNMR experiments and computational approaches as applied to a complex but typical pharmaceutical solid phase.

  6. 250 GHz CW Gyrotron Oscillator for Dynamic Nuclear Polarization in Biological Solid State NMR

    PubMed Central

    Bajaj, Vikram S.; Hornstein, Melissa K.; Kreischer, Kenneth E.; Sirigiri, Jagadishwar R.; Woskov, Paul P.; Mak-Jurkauskas, Melody L.; Herzfeld, Judith; Temkin, Richard J.; Griffin, Robert G.

    2009-01-01

    In this paper, we describe a 250 GHz gyrotron oscillator, a critical component of an integrated system for magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments at 9T, corresponding to 380 MHz 1H frequency. The 250 GHz gyrotron is the first gyro-device designed with the goal of seamless integration with an NMR spectrometer for routine DNP-enhanced NMR spectroscopy and has operated under computer control for periods of up to 21 days with a 100% duty cycle. Following a brief historical review of the field, we present studies of the membrane protein bacteriorhodopsin (bR) using DNP-enhanced multidimensional NMR. These results include assignment of active site resonances in [U-13C,15N]-bR and demonstrate the utility of DNP for studies of membrane proteins. Next, we review the theory of gyro-devices from quantum mechanical and classical viewpoints and discuss the unique considerations that apply to gyrotron oscillators designed for DNP experiments. We then characterize the operation of the 250 GHz gyrotron in detail, including its long-term stability and controllability. We have measured the spectral purity of the gyrotron emission using both homodyne and heterodyne techniques. Radiation intensity patterns from the corrugated waveguide that delivers power to the NMR probe were measured using two new techniques to confirm pure mode content: a thermometric approach based on the temperature-dependent color of liquid crystalline media applied to a substrate and imaging with a pyroelectric camera. We next present a detailed study of the mode excitation characteristics of the gyrotron. Exploration of the operating characteristics of several fundamental modes reveals broadband continuous frequency tuning of up to 1.8 GHz as a function of the magnetic field alone, a feature that may be exploited in future tunable gyrotron designs. Oscillation of the 250 GHz gyrotron at the second harmonic of cyclotron resonance begins at extremely low beam currents (as low

  7. Solid state NMR study of dietary fiber powders from aronia, bilberry, black currant and apple.

    PubMed

    Wawer, I; Wolniak, M; Paradowska, K

    2006-09-01

    13C CPMAS NMR spectra of dietary fiber powders from aronia (chokeberry), bilberry, black currant and apple were recorded. The spectra are complex owing to superposition of resonances from different polysaccharides and polyphenolic compounds. Standard, dipolar dephased and the TH(1rho) partially relaxed spectra enabled the identification of several constituents: microcrystalline cellulose, pectins, lignins, cutin-like polymers and condensed tannins. The fiber powders obtained from berries contain significant amounts of anthocyanins, as indicated by their dark violet color, but not verified by chemical shifts. The anthocyanin-rich extract from aronia berries and its major components, cyanidin-3-O-galactoside and (-)epicatechin were also studied.

  8. High Resolution Solid State 13C NMR Spectroscopy of Sporopollenins from Different Plant Taxa

    PubMed Central

    Guilford, William J.; Schneider, Diane M.; Labovitz, Jeffrey; Opella, Stanley J.

    1988-01-01

    The extremely chemically resistant component of the cell wall of spores, pollens, and some microorganisms, sporopollenin, is generally accepted to be derived from carotenoids or carotenoid esters. However, we report here that 13C NMR analyses of sporopollenin from several sources shows that this widely held view is incorrect, with one possible exception. Sporopollenin is not a unique substance but rather a series of related biopolymers derived from largely saturated precursors such as fatty acids. The biopolymers contain widely varying amounts of oxygen in the form of ether, hydroxyl, carboxylic acid, ester, and ketone groups. PMID:16665854

  9. 250 GHz CW gyrotron oscillator for dynamic nuclear polarization in biological solid state NMR

    NASA Astrophysics Data System (ADS)

    Bajaj, Vikram S.; Hornstein, Melissa K.; Kreischer, Kenneth E.; Sirigiri, Jagadishwar R.; Woskov, Paul P.; Mak-Jurkauskas, Melody L.; Herzfeld, Judith; Temkin, Richard J.; Griffin, Robert G.

    2007-12-01

    In this paper, we describe a 250 GHz gyrotron oscillator, a critical component of an integrated system for magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments at 9 T, corresponding to 380 MHz 1H frequency. The 250 GHz gyrotron is the first gyro-device designed with the goal of seamless integration with an NMR spectrometer for routine DNP enhanced NMR spectroscopy and has operated under computer control for periods of up to 21 days with a 100% duty cycle. Following a brief historical review of the field, we present studies of the membrane protein bacteriorhodopsin (bR) using DNP enhanced multidimensional NMR. These results include assignment of active site resonances in [U- 13C, 15N]-bR and demonstrate the utility of DNP for studies of membrane proteins. Next, we review the theory of gyro-devices from quantum mechanical and classical viewpoints and discuss the unique considerations that apply to gyrotron oscillators designed for DNP experiments. We then characterize the operation of the 250 GHz gyrotron in detail, including its long-term stability and controllability. We have measured the spectral purity of the gyrotron emission using both homodyne and heterodyne techniques. Radiation intensity patterns from the corrugated waveguide that delivers power to the NMR probe were measured using two new techniques to confirm pure mode content: a thermometric approach based on the temperature-dependent color of liquid crystalline media applied to a substrate and imaging with a pyroelectric camera. We next present a detailed study of the mode excitation characteristics of the gyrotron. Exploration of the operating characteristics of several fundamental modes reveals broadband continuous frequency tuning of up to 1.8 GHz as a function of the magnetic field alone, a feature that may be exploited in future tunable gyrotron designs. Oscillation of the 250 GHz gyrotron at the second harmonic of cyclotron resonance begins at extremely low beam currents (as

  10. Solid-State NMR Study of Metastable Immiscibility in Alkali Borosilicate Glasses

    NASA Astrophysics Data System (ADS)

    Du, L.; Stebbins, J. F.

    2001-12-01

    Liquid-liquid phase separation is a critical issue in controlling and designing the physical properties of borosilicate glasses such as chemical durability, crystal nucleation, and high temperature strength and can provide insight into unmixing in natural magmatic systems as well. It is important to clarify this phenomenon, especially the immiscibility boundaries, which can be difficult to determine by conventional methods. High resolution NMR can provide a sensitive probe for the observation of phase separation in glass systems. In the M2O-B2O3-SiO2 system (M= Li, Na, K), we have used oxygen-17 MQMAS (Multiple Quantum Magic Angle Spinning) technique to explore changes in connectivities between SiO4, BO3 and BO4 units, based on changes in populations of bridging oxygens, such as B-O-B, B-O-Si and Si-O-Si, and of non-bridging oxygens. We have also used boron-11 MAS and MQMAS to quantify populations of borate units with varying first shell coordination and connectivity to other network units, e.g., "ring" vs. "non-ring" BO3 groups. In a series of alkali borosilicates of the same stoichiometry, the population of Si-O-B oxygen for the Li glass is significantly lower than that for Na and K borosilicates. This implies that the Li glass has a greater degree of phase separation at a submicroscopic scale as expected from phase diagrams. O-17 MQMAS NMR is also useful in determining the effect of quenching rate and annealing temperature on the degree of phase separation. In the Na borosilicates, a reduced concentration of Si-O-B in compositions within the immiscibility region suggests that even optically homogeneous glasses have small-scale heterogeneity. In the B-11 MAS and MQMAS studies, the ratio of BO3 to BO4 does not change with annealing. The non-ring BO3, however, converts to ring BO3 with annealing, which increases the degree of phase separation. In the study of Na2O-B2O3-SiO2 glasses with different Na contents, Si-O-B(III) and Si-O-B(IV) as well as B-O-B(III) and B

  11. Identification of different oxygen species in oxide nanostructures with (17)O solid-state NMR spectroscopy.

    PubMed

    Wang, Meng; Wu, Xin-Ping; Zheng, Sujuan; Zhao, Li; Li, Lei; Shen, Li; Gao, Yuxian; Xue, Nianhua; Guo, Xuefeng; Huang, Weixin; Gan, Zhehong; Blanc, Frédéric; Yu, Zhiwu; Ke, Xiaokang; Ding, Weiping; Gong, Xue-Qing; Grey, Clare P; Peng, Luming

    2015-02-01

    Nanostructured oxides find multiple uses in a diverse range of applications including catalysis, energy storage, and environmental management, their higher surface areas, and, in some cases, electronic properties resulting in different physical properties from their bulk counterparts. Developing structure-property relations for these materials requires a determination of surface and subsurface structure. Although microscopy plays a critical role owing to the fact that the volumes sampled by such techniques may not be representative of the whole sample, complementary characterization methods are urgently required. We develop a simple nuclear magnetic resonance (NMR) strategy to detect the first few layers of a nanomaterial, demonstrating the approach with technologically relevant ceria nanoparticles. We show that the (17)O resonances arising from the first to third surface layer oxygen ions, hydroxyl sites, and oxygen species near vacancies can be distinguished from the oxygen ions in the bulk, with higher-frequency (17)O chemical shifts being observed for the lower coordinated surface sites. H2 (17)O can be used to selectively enrich surface sites, allowing only these particular active sites to be monitored in a chemical process. (17)O NMR spectra of thermally treated nanosized ceria clearly show how different oxygen species interconvert at elevated temperature. Density functional theory calculations confirm the assignments and reveal a strong dependence of chemical shift on the nature of the surface. These results open up new strategies for characterizing nanostructured oxides and their applications.

  12. Investigating lanthanide dopant distributions in Yttrium Aluminum Garnet (YAG) using solid state paramagnetic NMR.

    PubMed

    McCarty, Ryan J; Stebbins, Jonathan F

    2016-10-01

    This paper demonstrates the approach of using paramagnetic effects observed in NMR spectra to investigate the distribution of lanthanide dopant cations in YAG (yttrium aluminum garnet, Y3Al5O12) optical materials, as a complimentary technique to optical spectroscopy and other standard methods of characterization. We investigate the effects of Ce(3+), Nd(3+), Yb(3+), Tm(3+), and Tm(3+)-Cr(3+) on (27)Al and (89)Y NMR spectra. We note shifted resonances for both AlO4 and AlO6 sites. In some cases, multiple shifted peaks are observable, and some of these can be empirically assigned to dopant cations in known configurations to the observed nuclides. In many cases, AlO6 peaks shifted by more than one magnetic neighbor can be detected. In general, we observe that the measured intensities of shifted resonances, when spinning sidebands are included, are consistent with predictions from models with dopant cations that are randomly distributed throughout the lattice. In at least one set of (27)Al spectra, we identify two sub-peaks possibly resulting from two paramagnetic cations with magnetically coupled spin states neighboring the observed nucleus. We identify systematic changes in the spectra related to known parameters describing the magnetic effects of lanthanide cations, such as larger shift distances when the expectation value of electron spins is greater. We lastly comment on the promise of this technique in future analyses of laser and other crystalline oxide materials. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. Identification of different oxygen species in oxide nanostructures with 17O solid-state NMR spectroscopy

    PubMed Central

    Wang, Meng; Wu, Xin-Ping; Zheng, Sujuan; Zhao, Li; Li, Lei; Shen, Li; Gao, Yuxian; Xue, Nianhua; Guo, Xuefeng; Huang, Weixin; Gan, Zhehong; Blanc, Frédéric; Yu, Zhiwu; Ke, Xiaokang; Ding, Weiping; Gong, Xue-Qing; Grey, Clare P.; Peng, Luming

    2015-01-01

    Nanostructured oxides find multiple uses in a diverse range of applications including catalysis, energy storage, and environmental management, their higher surface areas, and, in some cases, electronic properties resulting in different physical properties from their bulk counterparts. Developing structure-property relations for these materials requires a determination of surface and subsurface structure. Although microscopy plays a critical role owing to the fact that the volumes sampled by such techniques may not be representative of the whole sample, complementary characterization methods are urgently required. We develop a simple nuclear magnetic resonance (NMR) strategy to detect the first few layers of a nanomaterial, demonstrating the approach with technologically relevant ceria nanoparticles. We show that the 17O resonances arising from the first to third surface layer oxygen ions, hydroxyl sites, and oxygen species near vacancies can be distinguished from the oxygen ions in the bulk, with higher-frequency 17O chemical shifts being observed for the lower coordinated surface sites. H217O can be used to selectively enrich surface sites, allowing only these particular active sites to be monitored in a chemical process. 17O NMR spectra of thermally treated nanosized ceria clearly show how different oxygen species interconvert at elevated temperature. Density functional theory calculations confirm the assignments and reveal a strong dependence of chemical shift on the nature of the surface. These results open up new strategies for characterizing nanostructured oxides and their applications. PMID:26601133

  14. DNP-enhanced ultrawideline solid-state NMR spectroscopy: Studies of platinum in metal–organic frameworks

    DOE PAGES

    Kobayashi, Takeshi; Perras, Frederic A.; Goh, Tian Wei; ...

    2016-06-06

    Ultrawideline dynamic nuclear polarization (DNP)-enhanced 195Pt solid-state NMR (SSNMR) spectroscopy and theoretical calculations are used to determine the coordination of atomic Pt species supported within the pores of metal–organic frameworks (MOFs). The 195Pt SSNMR spectra, with breadths reaching 10,000 ppm, were obtained by combining DNP with broadbanded cross-polarization and CPMG acquisition. Although the DNP enhancements in static samples are lower than those typically observed under magic-angle spinning conditions, the presented measurements would be very challenging using the conventional SSNMR methods. The DNP-enhanced ultrawideline NMR spectra served to separate signals from cis- and trans-coordinated atomic Pt2+ species supported on the UiO-66-NH2more » MOF. Here, the data revealed a dominance of kinetic effects in the formation of Pt2+ complexes and the thermodynamic effects in their reduction to nanoparticles. A single cis-coordinated Pt2+ complex was confirmed in MOF-253.« less

  15. DNP-enhanced ultrawideline solid-state NMR spectroscopy: Studies of platinum in metal–organic frameworks

    SciTech Connect

    Kobayashi, Takeshi; Perras, Frederic A.; Goh, Tian Wei; Metz, Tanner L.; Huang, Wenyu; Pruski, Marek

    2016-06-06

    Ultrawideline dynamic nuclear polarization (DNP)-enhanced 195Pt solid-state NMR (SSNMR) spectroscopy and theoretical calculations are used to determine the coordination of atomic Pt species supported within the pores of metal–organic frameworks (MOFs). The 195Pt SSNMR spectra, with breadths reaching 10,000 ppm, were obtained by combining DNP with broadbanded cross-polarization and CPMG acquisition. Although the DNP enhancements in static samples are lower than those typically observed under magic-angle spinning conditions, the presented measurements would be very challenging using the conventional SSNMR methods. The DNP-enhanced ultrawideline NMR spectra served to separate signals from cis- and trans-coordinated atomic Pt2+ species supported on the UiO-66-NH2 MOF. Here, the data revealed a dominance of kinetic effects in the formation of Pt2+ complexes and the thermodynamic effects in their reduction to nanoparticles. A single cis-coordinated Pt2+ complex was confirmed in MOF-253.

  16. Color-discriminating retinal configurations of sensory rhodopsin I by photo-irradiation solid-state NMR spectroscopy.

    PubMed

    Yomoda, Hiroki; Makino, Yoshiteru; Tomonaga, Yuya; Hidaka, Tetsurou; Kawamura, Izuru; Okitsu, Takashi; Wada, Akimori; Sudo, Yuki; Naito, Akira

    2014-07-01

    SRI (sensory rhodopsin I) can discriminate multiple colors for the attractant and repellent phototaxis. Studies aimed at revealing the color-dependent mechanism show that SRI is a challenging system not only in photobiology but also in photochemistry. During the photoreaction of SRI, an M-intermediate (attractant) transforms into a P-intermediate (repellent) by absorbing blue light. Consequently, SRI then cycles back to the G-state. The photoreactions were monitored with the (13)C NMR signals of [20-(13)C]retnal-SrSRI using in situ photo-irradiation solid-state NMR spectroscopy. The M-intermediate was trapped at -40 °C by illumination at 520 nm. It was transformed into the P-intermediate by subsequent illumination at 365 nm. These results reveal that the G-state could be directly transformed to the P-intermediate by illumination at 365 nm. Thus, the stationary trapped M- and P-intermediates are responsible for positive and negative phototaxis, respectively. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Parameter independent low-power heteronuclear decoupling for fast magic-angle spinning solid-state NMR

    NASA Astrophysics Data System (ADS)

    Equbal, Asif; Madhu, P. K.; Meier, Beat H.; Nielsen, Niels Chr.; Ernst, Matthias; Agarwal, Vipin

    2017-02-01

    Major advances have recently been made in the field of heteronuclear dipolar decoupling in solid-state nuclear magnetic resonance (NMR). These developments have improved the resolution and sensitivity of the NMR spectrum of spins coupled to protons. One such new scheme, denoted as rCWApA, has proven to be robust with practically no need for parameter optimization [A. Equbal et al. Chem. Phys. Lett., 635, 339 (2015)]. Most of the experiments with rCWApA have been carried out in the regimes of slow to moderate magic-angle spinning while simultaneously applying high decoupling radio-frequency amplitudes. Here, we explore the performance of the rCWApA sequence and its predecessor rCWA in the regime of low-power radio-frequency irradiation and fast magic-angle spinning. The robustness of the refocused continuous-wave (rCW) schemes to experimental parameters such as pulse lengths and offset irradiation is demonstrated. Numerical simulations and analytical theory have been used to understand the effects of various nuclear spin interactions on the decoupling performance of the low-power rCW decoupling scheme relative to other decoupling methods. This has lead to the design of an "optimum low-power decoupling sequence" that can be used without parameter optimization. This result is particularly important in the context of samples with low signal to noise.

  18. DNP-enhanced ultrawideline 207Pb solid-state NMR spectroscopy: an application to cultural heritage science

    DOE PAGES

    Kobayashi, Takeshi; Perras, Frederic A.; Murphy, Anna; ...

    2017-02-17

    Dynamic nuclear polarization (DNP) is used to enhance the (ultra)wideline 207Pb solid-state NMR spectra of lead compounds of relevance in the preservation of cultural heritage objects. The DNP SSNMR experiments enabled, for the first time, the detection of the basic lead carbonate phase of the lead white pigment by 207Pb SSNMR spectroscopy. Variable-temperature experiments revealed that the short T'2 relaxation time of the basic lead carbonate phase hinders the acquisition of the NMR signal at room temperature. We additionally observe that the DNP enhancement is twice as large for lead palmitate (a lead soap, which is a degradation product implicatedmore » in the visible deterioration of lead-based oil paintings), than it is for the basic lead carbonate. As a result, this enhancement has allowed us to detect the formation of a lead soap in an aged paint film by 207Pb SSNMR spectroscopy; which may aid in the detection of deterioration products in smaller samples removed from works of art.« less

  19. Probing physical and chemical changes in cortical bone due to osteoporosis and type 2 diabetes by solid-state NMR

    NASA Astrophysics Data System (ADS)

    Zhou, Donghua; Taylor, Amanda; Rendina, Beth; Smith, Brenda; Department of Physics Collaboration; Department of Nutritional Sciences Collaboration

    2013-03-01

    Approximately 1.5 million fractures occur each year in the U.S. due to osteoporosis, which is characterized by decreased bone mineral density and deterioration of bone micro-architecture. On the other hand, type 2 diabetes also significantly increases fracture risks, despite having a normal or even higher bone mineral density. Solid-state NMR has been applied to bone tissues from normal and disease-inflicted mouse models to study structural and chemical dynamics as the disease progresses. Proton relaxation experiments were performed to measure water populations in the bone matrix and pores. Collagen-bound water has strong influence on bone resilience, while water content in the