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1

Probes for High Field Solid-state NMR of Lossy Biological Samples  

PubMed Central

In solid-state NMR exphydrated samples biopolymers are susceptible to radio-frequency heating and have a significant impact on probe tuning frequency and performance parameters such as sensitivity. These considerations are increasingly important as magnetic field strengths increase with improved magnet technology. Recent developments in the design, construction, and performance of probes for solid-state NMR experiments on stationary lossy biological samples at high magnetic fields are reviewed. PMID:20435493

Grant, Christopher V.; Wu, Chin H.; Opella, Stanley J.

2010-01-01

2

Pulsed gradient NMR probes for solid state studies.  

PubMed

Recently introduced studies of the spatial characteristics of spin dynamics in dipolarly coupled solids rely upon NMR probes with strong magnetic field gradients to create spatial magnetization gratings with periods of from 1 micron to 1 nm. The measurements are carried out as scattering experiments where the spatial displacement of spin coherence is recorded as a phase shift or attenuation of the magnetization grating. Recently we have employed these techniques to make a direct measurement of the spin diffusion rate in single crystal CaF2. Here we discuss designs for strong pulsed gradient NMR probes. Three gradient coil sets were designed and constructed, with coil constants of 0.32, 0.67, and 4.15 T/m/A. When driven by a pulsed current source that provides up to 300 A, pulsed gradients of 100, 200, and 600 T/m, respectively, were generated. These designs are fully described, along with practical issues of coil heating and probe stability. PMID:9615414

Zhang, W; Cory, D G

1998-05-01

3

(113) cd solid-state NMR for probing the coordination sphere in metal-organic frameworks.  

PubMed

Spectroscopic techniques are a powerful tool for structure determination, especially if single-crystal material is unavailable. (113) Cd solid-state NMR is easy to measure and is a highly sensitive probe because the coordination number, the nature of coordinating groups, and the geometry around the metal ion is reflected by the isotropic chemical shift and the chemical-shift anisotropy. Here, a detailed investigation of a series of 27 cadmium coordination polymers by (113) Cd solid-state NMR is reported. The results obtained demonstrate that (113) Cd?NMR is a very sensitive tool to characterize the cadmium environment, also in non-single-crystal materials. Furthermore, this method allows the observation of guest-induced phase transitions supporting understanding of the structural flexibility of coordination frameworks. PMID:25404549

Kuttatheyil, Anusree Viswanath; Handke, Marcel; Bergmann, Jens; Lässig, Daniel; Lincke, Jörg; Haase, Jürgen; Bertmer, Marko; Krautscheid, Harald

2015-01-12

4

A LOW-E MAGIC ANGLE SPINNING PROBE FOR BIOLOGICAL SOLID STATE NMR AT 750 MHz  

PubMed Central

Crossed-coil NMR probes are a useful tool for reducing sample heating for biological solid state NMR. In a crossed-coil probe, the higher frequency 1H field, which is the primary source of sample heating in conventional probes, is produced by a separate low-inductance resonator. Because a smaller driving voltage is required, the electric field across the sample and the resultant heating is reduced. In this work we describe the development of a magic angle spinning (MAS) solid state NMR probe utilizing a dual resonator. This dual resonator approach, referred to as “Low-E,” was originally developed to reduce heating in samples of mechanically aligned membranes. The study of inherently dilute systems, such as proteins in lipid bilayers, via MAS techniques requires large sample volumes at high field to obtain spectra with adequate signal-to-noise ratio under physiologically relevant conditions. With the Low-E approach, we are able to obtain homogeneous and sufficiently strong radiofrequency fields for both 1H and 13C frequencies in a 4 mm probe with a 1H frequency of 750 MHz. The performance of the probe using windowless dipolar recoupling sequences is demonstrated on model compounds as well as membrane embedded peptides. PMID:19138870

McNeill, Seth A.; Gor’kov, Peter L.; Shetty, Kiran; Brey, William W.; Long, Joanna R.

2009-01-01

5

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

SciTech Connect

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.

Fernandez, Christian; Pruski, Marek

2011-06-08

6

Solid-state NMR imaging system  

DOEpatents

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.

Gopalsami, Nachappa (Naperville, IL); Dieckman, Stephen L. (Elmhurst, IL); Ellingson, William A. (Naperville, IL)

1992-01-01

7

Solid-state NMR imaging system  

SciTech Connect

An accessory 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.

Gopalsami, N.; Dieckman, S.L.; Ellingson, W.A.

1990-01-01

8

Acid properties of solid acid catalysts characterized by solid-state 31P NMR of adsorbed phosphorous probe molecules.  

PubMed

A brief review is presented on acidity characterization of solid acid catalysts by means of solid-state phosphor-31 magic-angle-spinning nuclear magnetic resonance ((31)P MAS NMR) spectroscopy using phosphor-containing molecules as probes. It is emphasized that such a simple approach using (31)P MAS NMR of adsorbed phosphorous probe molecules, namely trimethylphosphine (TMP) and trialkylphosphine oxides (R(3)PO), represents a unique technique in providing detailed qualitative and quantitative features, viz. type, strength, distribution, and concentration of acid sites in solid acid catalysts. In particular, it will be shown that when applied with a proper choice of probe molecules with varied sizes and results obtained from elemental analysis, the amounts and locations (intracrystalline vs. extracrystalline) of different types (Brønsted vs. Lewis) of acid sites may be determined. In addition, by incorporating the NMR results with that obtained from theoretical density functional theory (DFT) calculations, correlations between the (31)P chemical shifts (?(31)P) and acidic strengths of Brønsted and Lewis acid sites may also be derived, facilitating a suitable acidity scale for solid acid catalysts. PMID:21785784

Zheng, Anmin; Huang, Shing-Jong; Liu, Shang-Bin; Deng, Feng

2011-09-01

9

An efficient 1H/31P double-resonance solid-state NMR probe that utilizes a scroll coil  

PubMed Central

The construction and performance of a scroll coil double-resonance probe for solid-state NMR on stationary samples is described. The advantages of the scroll coil at the high resonance frequencies of 1H and 31P include: high efficiency, minimal perturbations of tuning by a wide range of samples, minimal RF sample heating of high dielectric samples of biopolymers in aqueous solution, and excellent RF homogeneity. The incorporation of a cable tie cinch for mechanical stability of the scroll coil is described. Experimental results obtained on a Hunter Killer Peptide 1 (HKP1) interacting with phospholipid bilayers of varying lipid composition demonstrate the capabilities of this probe on lossy aqueous samples. PMID:17719813

Grant, Christopher V.; Sit, Siu-Ling; De Angelis, Anna A.; Khuong, Kelli S.; Wu, Chin H.; Plesniak, Leigh A.; Opella, Stanley J.

2007-01-01

10

Probing membrane protein structure using water polarization transfer solid-state NMR  

NASA Astrophysics Data System (ADS)

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.

Williams, Jonathan K.; Hong, Mei

2014-10-01

11

Probing the surface of platinum nanoparticles with 13CO by solid-state NMR and IR spectroscopies  

NASA Astrophysics Data System (ADS)

The synthesis and full characterization of platinum nanoparticles (Pt NPs) prepared by decomposition of the Pt(dba)2 complex in the presence of CO and H2 and stabilized either sterically by a polymer, polyvinylpyrrolidone or chemically by a ligand, diphenylphosphinobutane, are reported. In these studies, 13CO was used as a probe molecule to investigate the surface of the particles, using IR and solid-state NMR spectroscopies with magic angle spinning (MAS-NMR). Three nanosystems with different sizes are described: Pt/PVP/13CO (monomodal: 1.2 nm), Pt/dppb/13CO (bimodal: 1.2 nm and 2.0 nm) and Pt/dppb/H2 (monomodal: 2.0 nm) NPs. Spectroscopic data suggest a modification of the electronic state of the nanoparticles between 1.2 nm and 2.0 nm which can be related to the presence of Knight shift.The synthesis and full characterization of platinum nanoparticles (Pt NPs) prepared by decomposition of the Pt(dba)2 complex in the presence of CO and H2 and stabilized either sterically by a polymer, polyvinylpyrrolidone or chemically by a ligand, diphenylphosphinobutane, are reported. In these studies, 13CO was used as a probe molecule to investigate the surface of the particles, using IR and solid-state NMR spectroscopies with magic angle spinning (MAS-NMR). Three nanosystems with different sizes are described: Pt/PVP/13CO (monomodal: 1.2 nm), Pt/dppb/13CO (bimodal: 1.2 nm and 2.0 nm) and Pt/dppb/H2 (monomodal: 2.0 nm) NPs. Spectroscopic data suggest a modification of the electronic state of the nanoparticles between 1.2 nm and 2.0 nm which can be related to the presence of Knight shift. Electronic supplementary information (ESI) available: Synthesis of the Pt(dba)2 precursor, TEM images of Pt/PVP/H2 and Pt/dppb/13CO NPs, further results from WAXS studies, solution NMR spectra of Pt/dppb/13CO NPs and MAS-NMR spectra of Pt/dppb/13CO and Pt/dppb/H2 NPs at 260 K. See DOI: 10.1039c3nr03948j

Kinayyigit, Solen; Lara, Patricia; Lecante, Pierre; Philippot, Karine; Chaudret, Bruno

2013-12-01

12

Symmetry-Amplified J Splittings for Quadrupolar Spin Pairs: A Solid-State NMR Probe of Homoatomic Covalent Bonds  

PubMed Central

Chemically informative J couplings between pairs of quadrupolar nuclei in dimetallic and dimetalloid coordination motifs are measured using J-resolved solid-state NMR experiments. It is shown that the application of a double-quantum filter is necessary to observe the J splittings and that, under these conditions, only a simple doublet is expected. Interestingly, the splitting is amplified if the spins are magnetically equivalent, making it possible to measure highly precise J couplings and unambiguously probe the symmetry of the molecule. This is demonstrated experimentally by chemically breaking the symmetry about a pair of boron spins by reaction with an N-heterocyclic carbene to form a ?-borylation reagent. The results show that the J coupling is a sensitive probe of bonding in diboron compounds and that the J values quantify the weakening of the B–B bond which occurs when forming an sp2–sp3 diboron compound, which is relevant to their reactivity. Due to the prevalence of quadrupolar nuclei among transition metals, this work also provides a new approach to probe metal–metal bonding; results for Mn2(CO)10 are provided as an example. PMID:23919916

2013-01-01

13

DEVELOPMENT OF MULTIPLE SAMPLE SOLID-STATE NMR PROBES FOR ANALYSIS OF PHARMACEUTICAL COMPOUNDS AND FORMULATIONS  

E-print Network

. Compound 1H Frequency Delay (s) Delay at 9.4 T (s) Ref R.O.Y.* 300 40-70 70-125 4 Cimetidine 360 15 18 5 LY297802 400 5-10 5-10 6 Ephedrine 200 1.5 6 7 Aspirin 300 90 160 † Salicylic Acid 300 1000 1780 † Prednisolone t-Butylacetate 200 3 12 8...297802 Tartrate. J. Pharm. Sci., 1998. 87: p. 1568. 12. Schmidt, W.F. and I.L. Honigberg, Nuclear Magnetic Resonance (NMR) Spectroscopic Investigation of Interaction Energies of Ephedrine Steroisomers in Non Crystalline Solids and its Correlation...

Nelson, Benjamin Nels

2011-12-31

14

Probing Transient Conformational States of Proteins by Solid-State R1? Relaxation-Dispersion NMR Spectroscopy  

PubMed Central

Functionally relevant states of proteins are often only short-lived, and thus difficult to detect. It is shown that R1? relaxation-dispersion experiments in magic-angle spinning solid-state NMR provide access to such transient states. Information about the exchange kinetics and relative populations can be obtained, and also structural information about the short-lived state in terms of chemical shifts and bond vector orientations. PMID:24644028

Ma, Peixiang; Haller, Jens D.; Zajakala, Jérémy; Macek, Pavel; Sivertsen, Astrid C.; Willbold, Dieter; Boisbouvier, Jérôme; Schanda, Paul

2014-01-01

15

A Modified Alderman-Grant Coil Makes Possible an Efficient Cross-Coil Probe for High Field Solid-state NMR of Lossy Biological Samples  

PubMed Central

The design, construction, and performance of a cross-coil double-resonance probe for solid-state NMR experiments on lossy biological samples at high magnetic fields are described. The outer coil is a Modified Alderman-Grant Coil (MAGC) tuned to the 1H frequency. The inner coil consists of a multi-turn solenoid coil that produces a B1 field orthogonal to that of the outer coil. This results in a compact nested cross-coil pair with the inner solenoid coil tuned to the low frequency detection channel. This design has several advantages over multiple-tuned solenoid coil probes, since RF heating from the 1H channel is substantially reduced, it can be tuned for samples with a wide range of dielectric constants, and the simplified circuit design and high inductance inner coil provides excellent sensitivity. The utility of this probe is demonstrated on two electrically lossy samples of membrane proteins in phospholipid bilayers (bicelles) that are particularly difficult for conventional NMR probes. The 72-residue polypeptide embedding the transmembrane helices 3 and 4 of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) (residues 194 – 241) requires a high salt concentration in order to be successfully reconstituted in phospholipid bicelles. A second application is to paramagnetic relaxation enhancement applied to the membrane-bound form of Pf1 coat protein in phospholipid bicelles where the resistance to sample heating enables high duty cycle solid-state NMR experiments to be performed. PMID:19733108

Grant, Christopher V.; Yang, Yuan; Glibowicka, Mira; Wu, Chin H.; Park, Sang Ho; Deber, Charles M.; Opella, Stanley J.

2009-01-01

16

A Modified Alderman-Grant Coil makes possible an efficient cross-coil probe for high field solid-state NMR of lossy biological samples  

NASA Astrophysics Data System (ADS)

The design, construction, and performance of a cross-coil double-resonance probe for solid-state NMR experiments on lossy biological samples at high magnetic fields are described. The outer coil is a Modified Alderman-Grant Coil (MAGC) tuned to the 1H frequency. The inner coil consists of a multi-turn solenoid coil that produces a B 1 field orthogonal to that of the outer coil. This results in a compact nested cross-coil pair with the inner solenoid coil tuned to the low frequency detection channel. This design has several advantages over multiple-tuned solenoid coil probes, since RF heating from the 1H channel is substantially reduced, it can be tuned for samples with a wide range of dielectric constants, and the simplified circuit design and high inductance inner coil provides excellent sensitivity. The utility of this probe is demonstrated on two electrically lossy samples of membrane proteins in phospholipid bilayers (bicelles) that are particularly difficult for conventional NMR probes. The 72-residue polypeptide embedding the transmembrane helices 3 and 4 of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) (residues 194-241) requires a high salt concentration in order to be successfully reconstituted in phospholipid bicelles. A second application is to paramagnetic relaxation enhancement applied to the membrane-bound form of Pf1 coat protein in phospholipid bicelles where the resistance to sample heating enables high duty cycle solid-state NMR experiments to be performed.

Grant, Christopher V.; Yang, Yuan; Glibowicka, Mira; Wu, Chin H.; Park, Sang Ho; Deber, Charles M.; Opella, Stanley J.

2009-11-01

17

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

PubMed

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. PMID:25372426

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

2014-12-10

18

Dynamic nuclear polarization in biomolecular solid state NMR : methods and applications in peptides and membrane proteins  

E-print Network

Solid state NMR can probe structure and dynamics on length scales from the atomic to the supramolecular. However, low sensitivity limits its application in macromolecules. NMR sensitivity can be improved by dynamic nuclear ...

Bajaj, Vikram Singh

2007-01-01

19

A strip-shield improves the efficiency of a solenoid coil in probes for high field solid-state NMR of lossy biological samples  

PubMed Central

A strip-shield inserted between a high inductance double-tuned solenoid coil and the glass tube containing the sample improves the efficiency of probes used for high-field solid-state NMR experiments on lossy aqueous samples of proteins and other biopolymers. A strip-shield is a coil liner consisting of thin copper strips layered on a PTFE (polytetrafluoroethylene) insulator. With lossy samples, the shift in tuning frequency is smaller, the reduction in Q, and RF-induced heating are all significantly reduced when the strip-shield is present. The performance of 800 MHz 1H/15N and 1H/13C double-resonance probes is demonstrated on aqueous samples of membrane proteins in phospholipid bilayers. PMID:19559634

Wu, Chin H.; Grant, Christopher V.; Cook, Gabriel A.; Park, Sang Ho; Opella, Stanley J.

2009-01-01

20

Effect of Ancillary Ligand on Electronic Structure as Probed by 51V Solid-State NMR Spectroscopy for Vanadium-o-Dioxolene Complexes  

PubMed Central

A series of vanadium(V) complexes with o-dioxolene (catecholato) ligands and an ancillary ligand, (N-(salicylideneaminato)ethylenediamine) (hensal), were investigated using 51V solid-state magic angle spinning NMR spectroscopy (51V MAS NMR) to assess the local environment of the vanadium(V). The solid-state 51V NMR parameters of vanadium(V) complexes with a related potentially tetradentate ancillary ligand (N-salicylidene-N?-(2-hydroxyethyl)ethylenediamine) (h2shed) were previously shown to be associated with the size of the HOMO-LUMO gap in the complex, and as such provide insights on the interaction between metal ion and ligand (P. B. Chatterjee, et al., Inorg. Chem 50 (2011) 9794). Our results show that the modification of the ancillary ligand does not impact the observed trend between complexes ranging from catechols with electron rich to electron poor substituents. However, the ancillary ligand does impact the size of the HOMO-LUMO separation in the parent complex and thus the solid-state vanadium NMR chemical shift of the unsubstituted vanadium complex. For these complexes significant changes observed in the isotropic shifts and more modest changes detected in the CQ reflect the electronic changes in the complex as the catechol is varied. However, no obvious trend was observed in the chemical shift anisotropies (?? and ??) with the variation in the catechol. The electronic changes in the coordination environment of the vanadium can be described using solid-state 51V NMR spectroscopy. PMID:24353476

Goncharova-Zapata, Olga; Chatterjee, Pabitra B.; Hou, Guangjin; Quinn, Laurence L.; Li, Mingyue; Yehl, Jenna

2013-01-01

21

Probing self-assembled 1,3,5-benzenetrisamides in isotactic polypropylene by 13C DQ solid-state NMR spectroscopy.  

PubMed

Using (13)C double quantum solid-state NMR spectroscopy, we were able to observe nuclei of a supramolecular BTA based additive on the nanoscale in a matrix of i-PP at a concentration of only 0.09 wt%. These nuclei exhibit the analogous structural features as the crystalline phase of the neat additive. PMID:23175351

Schmidt, Marko; Wittmann, Johannes J; Kress, Roman; Schmidt, Hans-Werner; Senker, Jürgen

2013-01-11

22

Lithium Polymer Electrolytes and Solid State NMR  

NASA Technical Reports Server (NTRS)

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 participation on a variety of other projects, including aero-gels and carbon graphite mat en als. The goals of the polymer electrolyte research are to improve the physical properties of the polymers. This includes improving conductivity, durability, and expanding the temperature range over which it is effective. Currently, good conductivity is only present at high temperatures. My goals are to experiment with different arrangements of rods and coils to achieve these desirable properties. Some of my experiments include changing the number of repeat units in the polymer, the size of the diamines, and the types of coil. Analysis of these new polymers indicates improvement in some properties, such as lower glass transition temperature; however, they are not as flexible as desired. With further research we hope to produce polymers that encompass all of these properties to a high degree.

Berkeley, Emily R.

2004-01-01

23

119Sn solid-state NMR as a local probe for correlations in CeRu4Sn6  

NASA Astrophysics Data System (ADS)

CeRu4Sn6 is a tetragonal ternary compound which develops strong correlations at low temperatures. NMR investigations on the Sn(I={1}/{2})119 nuclei are reported for the first time. The Knight shift K(T)119 at magnetic fields of about 1.8 T is relatively small ( ?-0.33%) and no significant temperature dependence could be resolved. The behavior of the spin-lattice relaxation rate (1/T1)119 at temperatures above approximately 20 K is consistent with a small gap semiconductor ( 1/T1?Texp(-?/kBT),?/kB=33 K). At lower temperatures (1/T1)119 shows an increase towards weaker T-dependence. This is interpreted as the formation of strong correlations around T*=10 K and is consistent with specific heat results in the framework of the Korringa model. Furthermore, measurements on the isostructural reference compound LaRu4Sn6 are presented.

Brüning, E. M.; Baenitz, M.; Gippius, A. A.; Paschen, S.; Strydom, A. M.; Steglich, F.

2006-05-01

24

Solid-State NMR Studies of Amyloid Fibril Structure  

NASA Astrophysics Data System (ADS)

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.

Tycko, Robert

2011-05-01

25

Structural studies of amyloid fibrils using solid-state NMR  

E-print Network

he development of solid-state NMR techniques and application to amyloid fibrils are presented. In addition, a new method of selective inversion based on chemical shift anisotropy is presented. An improved method for highly ...

Caporini, Marc Anthony

2008-01-01

26

Study of Paramagnetic Chromocenes by Solid-State NMR Spectroscopy  

E-print Network

-state NMR spectroscopy to polycrystalline paramagnetic sand- wich compounds was tested for chromocene (Cp2CrStudy of Paramagnetic Chromocenes by Solid-State NMR Spectroscopy Janet Blu¨mel,* Martin Herker), deuteriated chromocene (Cp2Cr-d10), and decamethyl- chromocene (Cp*2Cr). The bulk properties of paramagnetic

Bluemel, Janet

27

Functional groups identified by solid state 13C NMR spectroscopy  

Technology Transfer Automated Retrieval System (TEKTRAN)

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...

28

Parallelizing acquisitions of solid-state NMR spectra with multi-channel probe and multi-receivers: applications to nanoporous solids.  

PubMed

A five-channel ((1)H, (19)F, (31)P, (27)Al, (13)C) 2.5 mm magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) probe is used in combination with three separate receivers for the parallel acquisitions of one (1D) and two-dimensional (2D) NMR spectra in model fluorinated aluminophosphate and porous Al-based metal-organic framework (MOF). Possible combinations to record simultaneously spectra using this set-up are presented, including (i) parallel acquisitions of quantitative 1D NMR spectra of solids containing nuclei with contrasted T1 relaxation rates and (ii) parallel acquisitions of 2D heteronuclear NMR spectra. In solids containing numerous different NMR-accessible nuclei, the number of NMR experiments that have to be acquired to get accurate structural information is high. The strategy we present here, i.e. the multiplication of both the number of irradiation channels in the probe and the number of parallel receivers, offers one possibility to optimize this measurement time. PMID:24011557

Martineau, Charlotte; Decker, Frank; Engelke, Frank; Taulelle, Francis

2013-01-01

29

Solid state NMR spectroscopy as a probe of structure and bonding in the carbides Sc 3TC 4 (T = Co, Ni, Ru, Rh, Os, Ir)  

NASA Astrophysics Data System (ADS)

Scandium transition metal carbides having the formula Sc 3TC 4 (T = Co, Ni, Ru, Rh, Os, Ir) have been structurally characterized by solid state 13C and 45Sc nuclear magnetic resonance spectroscopy. In all the compounds investigated, well-resolved signals are observed for crystallographically distinct carbon and scandium sites, confirming the formation of superstructures in the Rh and Ir compounds at ambient temperature. 45Sc NMR spectra are dominated by anisotropic broadening due to second-order quadrupolar perturbations. The nuclear electric quadrupolar coupling parameters (the coupling constant CQ and the asymmetry parameter ?) are generally found in good agreement with values calculated theoretically from the crystal structure using the WIEN2k program. Furthermore, the spectra reveal large isotropic resonance shift differences between inequivalent Sc sites in a given compound and between sites of the same type for different compounds. Altogether the results illustrate that 45Sc NMR is a sensitive method for detecting isotropic and anisotropic local electron density variations in the Sc 3TC 4 family.

Zhang, Long; Fehse, Constanze; Eckert, Hellmut; Vogt, Christian; Hoffmann, Rolf-Dieter; Pöttgen, Rainer

2007-08-01

30

Solid State NMR and Protein-Protein Interactions in Membranes  

PubMed Central

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

Miao, Yimin; Cross, Timothy A.

2013-01-01

31

Biological membrane structure by solid-state NMR.  

PubMed

Nuclear magnetic resonance (NMR) spectroscopy, and particularly solid-state NMR spectroscopy, is a method of choice to study the structure and dynamics of both the lipid and the protein components of model and biological membranes. Different approaches have been developed to study these systems in which the restricted molecular motions result in broad NMR spectra. This contribution will first present an overview of the different techniques used to study lipid bilayers, namely 31p, 2H and 13C solid-state NMR spectroscopy. On the other hand, the study of the structure of membrane peptides and proteins is a rapidly growing field and several methods developed in the last two decades will be presented. These methods allow the investigation of protein systems for which structural information is often difficult to obtain by techniques such as X-ray diffraction and multidimensional solution NMR. PMID:11471756

Auger, M

2000-10-01

32

Solid-State NMR Spectroscopy for the Physical Chemistry Laboratory  

ERIC Educational Resources Information Center

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…

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

2013-01-01

33

Broadband adiabatic inversion pulses for cross polarization in wideline solid-state NMR spectroscopy  

E-print Network

Broadband adiabatic inversion pulses for cross polarization in wideline solid-state NMR polarization Solid-state NMR Wideline NMR Stationary sample CPMG WURST­CPMG 119 Sn 207 Pb 195 Pt a b s t r a c t Efficient acquisition of ultra-wideline solid-state NMR powder patterns is a continuing challenge. In par

Frydman, Lucio

34

Broadband solid-state MAS NMR of paramagnetic systems.  

PubMed

The combination of new magnet and probe technology with increasingly sophisticated pulse sequences has resulted in an increase in the number of applications of solid-state nuclear magnetic resonance (NMR) spectroscopy to paramagnetic materials and biomolecules. The interaction between the paramagnetic metal ions and the NMR-active nuclei often yields crucial structural or electronic information about the system. In particular the application of magic-angle spinning (MAS) has been shown to be crucial to obtaining resolution that is sufficiently high for studying complex systems. However such systems are generally extremely difficult to study as the shifts and shift anisotropies resulting from the same paramagnetic interaction broaden the spectrum beyond excitation and detection, and the paramagnetic relaxation enhancement (PRE) shortens the lifetimes of the excited signals considerably. One specific area that has therefore been receiving significant attention in recent years, and for which great improvements have been seen, is the development of broadband NMR sequences. The development of new excitation and inversion sequences for paramagnetic systems under MAS has often made the difference between the spectrum being unobtainable, and a complete NMR study being possible. However the development of the new sequences must explicitly take account of the modulation of the anisotropic shift interactions due to the sample rotation, with the resulting spin dynamics often being complicated considerably. The NMR sequences can either be helped or hindered by MAS, with the efficiency of some pulse schemes being destroyed, and others being greatly enhanced. This review describes the pulse sequences that have recently been proposed for broadband excitation, inversion, and refocussing of the signal components of paramagnetic systems. In doing so we define exactly what is meant by "broadband" under spinning conditions, and what the perfect pulse scheme should deliver. We also give a unified description of the spin dynamics under MAS which highlights the strengths and weaknesses of the various schemes, and which can be used as guidance for future research in this area. All the reviewed pulse schemes are evaluated both with simulations and experimental data obtained on the battery material LiFe0.5Mn0.5PO4 which is typical of the complexity of the paramagnetic systems that are currently under study. PMID:25669740

Pell, Andrew J; Pintacuda, Guido

2015-02-01

35

15N chemical shift referencing in solid state NMR.  

PubMed

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. PMID:24746715

Bertani, Philippe; Raya, Jésus; Bechinger, Burkhard

2014-01-01

36

Acid-base interactions and secondary structures of poly-L-lysine probed by 15N and 13C solid state NMR and Ab initio model calculations.  

PubMed

The interactions of the 15N-labeled amino groups of dry solid poly-L-lysine (PLL) with various halogen and oxygen acids HX and the relation to the secondary structure have been studied using solid-state 15N and 13C CPMAS NMR spectroscopy (CP = cross polarization and MAS = magic angle spinning). For comparison, 15N NMR spectra of an aqueous solution of PLL were measured as a function of pH. In order to understand the effects of protonation and hydration on the 15N chemical shifts of the amino groups, DFT and chemical shielding calculations were performed on isolated methylamine-acid complexes and on periodic halide clusters of the type (CH3NH3(+)X(-))n. The combined experimental and computational results reveal low-field shifts of the amino nitrogens upon interaction with the oxygen acids HX = HF, H2SO4, CH3COOH, (CH3)2POOH, H3PO4, HNO3, and internal carbamic acid formed by reaction of the amino groups with gaseous CO2. Evidence is obtained that only hydrogen-bonded species of the type (Lys-NH2***H-X)n are formed in the absence of water. 15N chemical shifts are maximum when H is located in the hydrogen bond center and then decrease again upon full protonation, as found for aqueous solution at low pH. By contrast, halogen acids interact in a different way. They form internal salts of the type (Lys-NH3(+)X(-))n via the interaction of many acid-base pairs. This salt formation is possible only in the beta-sheet conformation. By contrast, the formation of hydrogen-bonded complexes can occur both in beta-sheet domains as well as in alpha-helical domains. The 15N chemical shifts of the protonated ammonium groups increase when the size of the interacting halogen anions is increased from chloride to iodide and when the number of the interacting anions is increased. Thus, the observed high-field 15N shift of ammonium groups upon hydration is the consequence of replacing interacting halogen atoms by oxygen atoms. PMID:19367899

Dos, Alexandra; Schimming, Volkmar; Tosoni, Sergio; Limbach, Hans-Heinrich

2008-12-11

37

Solid-State NMR Characterization of Aluminum Oxide Nanofibers  

SciTech Connect

Aluminum oxide nanofibers have been generated by an electrospinning process, creating fibers with diameters on the nanometer scale and aspect ratios greater than a thousand. These nanofibers have the potential of providing enhanced catalytic properties, due to their large surface area and controllable compositions. Solid-state NMR is being used to investigate both the bulk and surface properties of these materials. 27Al NMR has shown that no chemistry occurs during the electrospinning process, even though potentials in excess of 20 kV are applied to the sample. Thermal treatment of the fibers to convert them to alumina results in the formation of different phases, with the phases identified by the relative populations of 4-, 5-, and 6-coordinate alumina sites. Heating to 525°C or 1200°C produces a species similar to the catalytically active gamma-phase or conversion of the nanofibers into the thermodynamically stable ?-alumina phase, respectively. 1H-27Al CP/MAS has shown that the ?-alumina phase has a low population of surface hydroxyls, whereas the “gamma-alumina” form has a much higher fraction of 5-coordinate sites, compared to materials synthesized by traditional techniques. Organophosphates are being used as molecular probes in the characterization of the nanofiber surfaces. 31P CP/MAS data has revealed the presence of mono-, bi- and tri-denate bound phosphate groups on the surface, with the onset of surface alumina dissolution with sample heating. The application of 1H-31P HETCOR shows that the three different types of bound organophosphates are intermixed, rather than there being separate domains for each type. 31P-27Al CP is also being used to distinguish the types of surface alumina sites bound to the phosphate species.

Cross, Jennifer L.; Tuttle, Ricky W.; Ramsier, Rex D.; Espe, Mathew

2006-07-24

38

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

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

39

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

PubMed

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. PMID:24291330

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

2014-01-01

40

Solid-State NMR Characterization of Gas Vesicle Structure  

PubMed Central

Gas vesicles are gas-filled buoyancy organelles with walls that consist almost exclusively of gas vesicle protein A (GvpA). Intact, collapsed gas vesicles from the cyanobacterium Anabaena flos-aquae were studied by solid-state NMR spectroscopy, and most of the GvpA sequence was assigned. Chemical shift analysis indicates a coil-?-?-?-?-coil peptide backbone, consistent with secondary-structure-prediction algorithms, and complementary information about mobility and solvent exposure yields a picture of the overall topology of the vesicle subunit that is consistent with its role in stabilizing an air-water interface. PMID:20858439

Sivertsen, Astrid C.; Bayro, Marvin J.; Belenky, Marina; Griffin, Robert G.; Herzfeld, Judith

2010-01-01

41

Recrystallized S-Layer Protein of a Probiotic Propionibacterium: Structural and Nanomechanical Changes upon Temperature or pH Shifts Probed by Solid-State NMR and AFM.  

PubMed

Surface protein layers (S layers) are common constituents of the bacterial cell wall and originate from the assembly of strain-dependent surface layer proteins (Slps). These proteins are thought to play important roles in the bacteria's biology and to have very promising technological applications as biomaterials or as part of cell-host cross-talk in probiotic mechanism. The SlpA from Propionibacterium freudenreichii PFCIRM 118 strain was isolated and recrystallized to investigate organization and assembly of the protein using atomic force microscopy and solid-state (1)H and (13)C-nuclear magnetic resonance. SlpA was found to form hexagonal p1 monolayer lattices where the protein exhibited high proportions of disordered regions and of bound water. The lattice structure was maintained, but softened, upon mild heating or acidification, probably in relation with the increasing mobilities of the disordered protein regions. These results gave structural insights on the mobile protein regions exposed by S layer films, upon physiologically relevant changes of their environmental conditions. PMID:25479375

de Sa Peixoto, Paulo; Roiland, Claire; Thomas, Daniel; Briard-Bion, Valérie; Le Guellec, Rozenn; Parayre, Sandrine; Deutsch, Stéphanie-Marie; Jan, Gwénaël; Guyomarc'h, Fanny

2015-01-13

42

Solid State NMR Studies of the Aluminum Hydride Phases  

NASA Technical Reports Server (NTRS)

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.

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

2006-01-01

43

Molecular Structure of Humin and Melanoidin via Solid State NMR  

PubMed Central

Sugar-derived humins and melanoidins figure significantly in food chemistry, agricultural chemistry, biochemistry and prebiotic chemistry. Despite wide interest and significant experimental attention, the amorphous and insoluble nature of the polymers has made them resistant to conventional structural characterization. Here we make use of solid-state NMR methods, including selective 13C substitution, 1H-dephasing, and double quantum filtration. The spectra, and their interpretation, are simplified by relying exclusively on hydronium for catalysis. The results for polymers derived from ribose, deoxyribose and fructose indicate diverse pathways to furans, suggest a simple route to pyrroles in the presence of amines, and reveal a heterogenous network-type polymer in which sugar molecules cross-link the heterocycles. PMID:21456563

Herzfeld, Judith; Rand, Danielle; Matsuki, Yoh; Daviso, Eugenio; Mak-Jurkauskas, Melody; Mamajanov, Irena

2011-01-01

44

Recent developments in solid-state NMR spectroscopy of crystalline microporous materials.  

PubMed

Microporous materials, having pores and channels on the same size scale as small to medium molecules, have found many important applications in current technologies, including catalysis, gas separation and drug storage and delivery. Many of their properties and functions are related to their detailed local structure, such as the type and distribution of active sites within the pores, and the specific structures of these active sites. Solid-state NMR spectroscopy has a strong track record of providing the requisite detailed atomic-level insight into the structures of microporous materials, in addition to being able to probe dynamic processes occurring on timescales spanning many orders of magnitude (i.e., from s to ps). In this Perspective, we provide a brief review of some of the basic experimental approaches used in solid-state NMR spectroscopy of microporous materials, and then discuss some more recent advances in this field, particularly those applied to the study of crystalline materials such as zeolites and metal-organic frameworks. These advances include improved software for aiding spectral interpretation, the development of the NMR-crystallography approach to structure determination, new routes for the synthesis of isotopically-labelled materials, methods for the characterisation of host-guest interactions, and methodologies suitable for observing NMR spectra of paramagnetic microporous materials. Finally, we discuss possible future directions, which we believe will have the greatest impact on the field over the coming years. PMID:24675798

Ashbrook, Sharon E; Dawson, Daniel M; Seymour, Valerie R

2014-05-14

45

Understanding membrane protein interaction and regulation using solid state NMR spectroscopy  

E-print Network

Understanding membrane protein interaction and regulation using solid state NMR spectroscopy-resolution solid state NMR spectroscopy have opened up this technique as a complement to X understanding their sub spectroscopy and their application in understanding regulation of cardiac and skeletal muscle relaxation

Shyamasundar, R.K.

46

Recent advances in solid-state NMR spectroscopy of quadrupolar nuclei.  

PubMed

Nuclear magnetic resonance (NMR) spectroscopy of quadrupolar nuclei (i.e., those with a spin quantum number I > 1/2) has always been viewed as "difficult" owing to the presence of an anisotropic broadening arising from the interaction of the nuclear electric quadrupole moment with the electric field gradient. This quadrupolar interaction can be considerable, resulting in broadening of the spectral resonances often over many MHz. Furthermore, magic-angle spinning (MAS), a conventional approach for increasing the resolution in solid-state NMR, is often unable to remove the broadening completely and high-resolution spectra are generally not obtained. Despite the vast amount of information contained in the anisotropic linewidths and lineshapes, the resolution and sensitivity challenges have, until recently, somewhat limited the application of solid-state NMR for quadrupolar nuclei. In general, structural information, such as that obtained through recoupling techniques or from two-dimensional correlation spectroscopy, is much more difficult to extract easily and accurately. However, recent advances in magnet design, probe hardware and pulse sequence development have significantly improved the ease with which quadrupolar spins can be studied and high-resolution spectra can be obtained, and recent applications are beginning to exploit the wealth of information available. In this discussion, we highlight just a few of the recent developments in this area, including new state-of-the art correlation experiments, the expanding study of nuclei with low gyromagnetic ratio, gamma, the increasing application of first-principles calculations in the solid state, and methods which exploit the quadrupolar broadening to provide information on dynamics. Whilst not a complete review, it is hoped that this brief overview of some of the more exciting recent developments can provide insight into the challenges, and the rewards, involved in the NMR study of quadrupolar nuclei. PMID:19652823

Ashbrook, Sharon E

2009-08-28

47

Investigating gabapentin polymorphism using solid-state NMR spectroscopy.  

PubMed

Solid-state NMR spectroscopy (SSNMR), coupled with powder X-ray diffraction (PXRD), was used to identify the physical forms of gabapentin in samples prepared by recrystallization, spray drying, dehydration, and milling. Four different crystalline forms of gabapentin were observed: form I, a monohydrate, form II, the most stable at ambient conditions, form III, produced by either recrystallization or milling, and an isomorphous desolvate produced from desolvating the monohydrate. As-received gabapentin (form II) was ball-milled for 45 min in both the presence and absence of hydroxypropylcellulose (HPC). The samples were then stored for 2 days at 50°C under 0% relative humidity and analyzed by 13C SSNMR and PXRD. High-performance liquid chromatography was run on the samples to determine the amount of degradation product formed before and after storage. The 1HT1 values measured for the sample varied from 130 s for the as-received unstressed material without HPC to 11 s for the material that had been ball-milled in the presence of HPC. Samples with longer 1HT1 values were substantially more stable than samples that had shorter T1 values. Samples milled with HPC had detectable form III crystals as well. These results suggest that SSNMR can be used to predict gabapentin stability in formulated products. PMID:23180225

Dempah, Kassibla E; Barich, Dewey H; Kaushal, Aditya M; Zong, Zhixin; Desai, Salil D; Suryanarayanan, Raj; Kirsch, Lee; Munson, Eric J

2013-03-01

48

Using low-E resonators to reduce RF heating in biological samples for static solid-state NMR up to 900 MHz  

Microsoft Academic Search

RF heating of solid-state biological samples is known to be a destabilizing factor in high-field NMR experiments that shortens the sample lifetime by continuous dehydration during the high-power cross-polarization and decoupling pulses. In this work, we describe specially designed, large volume, low-E15N–1H solid-state NMR probes developed for 600 and 900MHz PISEMA studies of dilute membrane proteins oriented in hydrated and

Peter L. Gor’kov; Eduard Y. Chekmenev; Conggang Li; Myriam Cotten; Jarrod J. Buffy; Nathaniel J. Traaseth; Gianluigi Veglia; William W. Brey

2007-01-01

49

Solid-State 13C NMR of Liquid Crystalline Polyesters: Variations in Morphology, Alignment, and Dynamics within a Homologous Series  

E-print Network

Solid-State 13C NMR of Liquid Crystalline Polyesters: Variations in Morphology, Alignment polymers was retained into the solid state if their quenchings occur while remaining within the strong NMR, the structures of these polyesters were examined by high-resolution solid-state 13C NMR. It was found that while

Frydman, Lucio

50

Solid-State NMR Examination of Alteration Layers on a Nuclear Waste Glasses  

SciTech Connect

Solid-state NMR is a powerful tool for probing the role and significance of alteration layers in determining the kinetics for the corrosion of nuclear waste glass. NMR methods are used to probe the chemical structure of the alteration layers to elucidate information about their chemical complexity, leading to increased insight into the mechanism of altered layer formation. Two glass compositions were examined in this study: a glass preliminarily designed for nuclear waste immobilization (called AFCI) and a simplified version of this AFCI glass (which we call SA1R). Powdered glasses with controlled and known particles sizes were corroded at 90 °C for periods of one and five months with a surface-area to solution-volume ratio of 100,000 m-1. 1H-29Si CP-CPMG MAS NMR, 1H-27Al CP-MAS NMR, 1H-11B CP-MAS NMR, and 1H-23Na CP-MAS NMR experiments provide isolated structural information about the alteration layers, which differ in structure from that of the pristine glass. Both glasses studied here develop alteration layers composed primarily of [IV]Si species. Aluminum is also retained in the alteration layers, perhaps facilitated by the observed increase in coordination from [IV]Al to [VI]Al, which correlates with a loss of charge balancing cations. 1H-11B CP-MAS NMR observations indicated a retention of boron in hydrated glass layers, which has not been characterized by previous work. For the AFCI glass, secondary phase formation begins during the corrosion times considered here, and these neophases are detected within the alteration layers. We identify precursor phases as crystalline sodium metasilicates. An important finding is that layer thickness depends on the length of the initial alteration stages and varies only with respect to silicon species during the residual rate regime.

Murphy, Kelly A. [Penn State Univ., State College, PA (United States). Dept. of Chemistry; Washton, Nancy M. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States). Environmental Molecular Science Lab.; Ryan, Joseph V. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Pantano, Carlo G. [Penn State Univ., State College, PA (United States). Dept. of Materials Science and Engineering; Mueller, Karl T. [Penn State Univ., State College, PA (United States). Dept. of Chemistry; Pacific Northwest National Laboratory (PNNL), Richland, WA (United States). Environmental Molecular Science Lab.

2013-06-01

51

Arabidopsis thalianafrom Polarization Transfer Solid-State NMR  

SciTech Connect

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.

White, Paul B [Ames Laboratory; Wang, Tuo [Ames Laboratory; Park, Yong Bum [Pennsylvania State University; Cosgrove, Daniel J [Pennsylvania State University; Hong, Mei [Ames Laboratory

2014-07-23

52

Characterization of noninnocent metal complexes using solid-state NMR spectroscopy: o-dioxolene vanadium complexes.  

PubMed

(51)V solid-state NMR (SSNMR) studies of a series of noninnocent vanadium(V) catechol complexes have been conducted to evaluate the possibility that (51)V 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 (51)V NMR chemical shifts cover a wide range from -200 to 400 ppm in solution and from -219 to 530 ppm in the solid state. A linear correlation of (51)V NMR isotropic solution and solid-state chemical shifts of complexes containing noninnocent ligands is observed. These experimental results provide the information needed for the application of (51)V SSNMR spectroscopy in characterizing the electronic properties of a wide variety of vanadium-containing systems and, in particular, those containing noninnocent ligands and that have chemical shifts outside the populated range of -300 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 (51)V SSNMR experiments are a highly sensitive probe of subtle differences in electronic distribution and orbital occupancy in these compounds. Quantum chemical (density functional theory) calculations of NMR parameters for [VO(hshed)(Cat)] yield a (51)V chemical shift anisotropy 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 catechol ligand with electron-donating groups results in an increase in the HOMO-LUMO gap and can be directly followed by an upfield shift for the vanadium catechol complex. In contrast, substitution of the catechol ligand with electron-withdrawing groups results in a decrease in the HOMO-LUMO gap and can directly be followed by a downfield shift for the complex. The vanadium catechol complexes were used in this work because (51)V is a half-integer quadrupolar nucleus whose NMR observables are highly sensitive to the local environment. However, the results are general and could be extended to other redox-active complexes that exhibit coordination chemistry similar to that of the vanadium catechol complexes. PMID:21842875

Chatterjee, Pabitra B; Goncharov-Zapata, Olga; Quinn, Laurence L; Hou, Guangjin; Hamaed, Hiyam; Schurko, Robert W; Polenova, Tatyana; Crans, Debbie C

2011-10-17

53

Solid-State NMR Spectroscopic Study of Phosphate Sorption Mechanisms on Aluminum (Hydr)oxides  

E-print Network

Solid-State NMR Spectroscopic Study of Phosphate Sorption Mechanisms on Aluminum (Hydr)oxides Wei the mechanism of phosphate sorption on aluminum hydroxides under different environ- mental conditions, including

Sparks, Donald L.

54

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

PubMed Central

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

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

2013-01-01

55

Analysis of trivalent cation complexation to functionalized mesoporous silica using solid-state NMR spectroscopy.  

PubMed

Functionalized mesoporous silica has applications in separations science, catalysis, and sensors. In this work, we studied the fundamental interactions of trivalent cations with functionalized mesoporous silica. We contacted trivalent cations of varying ionic radii with N-[5-(trimethoxysilyl)-2-aza-1-oxopentyl]caprolactam functionalized mesoporous silica with the aim of probing the binding mechanism of the metal to the surface of the solid. We studied the functionalized silica using solid-state nuclear magnetic resonance (NMR) spectroscopy before and after contact with the metals of interest. We collected NMR spectra of the various metals, as well as of (29)Si and (13)C to probe the silica substrate and the ligand properties, respectively. The NMR spectra indicate that the metals bind to the functionalized silica via two mechanisms. Aluminum sorbed to both the silica and the ligand, but with different coordination for each. Scandium also sorbed to both the silica and the ligand, and unlike the aluminum, had the same coordination number. Additionally, the functionalized silica was susceptible to acid hydrolysis and two primary mechanisms of degradation were observed: detachment from the silica surface and opening of the seven-membered ring in the ligand. Opening of the seven-membered ring may be beneficial in that it decreases steric hindrance of the molecule for binding. PMID:25265419

Shusterman, Jennifer; Mason, Harris; Bruchet, Anthony; Zavarin, Mavrik; Kersting, Annie B; Nitsche, Heino

2014-11-28

56

342 IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 46, NO. 1, JANUARY 2011 Palm NMR and 1-Chip NMR  

E-print Network

342 IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 46, NO. 1, JANUARY 2011 Palm NMR and 1-Chip NMR Nan in the palm of a hand, is the smallest NMR system ever built, and is 1200 lighter, 1200 smaller, yet 150 more 19, 2010; accepted July 28, 2010. Date of publication October 18, 2010; date of current version

Ham, Donhee

57

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

PubMed Central

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. PMID:24412099

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

2014-01-01

58

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

PubMed

This article reviews the application of solid-state (2)H 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 (2)H 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 (2)H 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 (2)H NMR thus reveals how membrane deformation can affect protein conformational changes within the stress field of the lipid bilayer. This article is part of a Special Issue entitled: NMR Spectroscopy for Atomistic Views of Biomembranes and Cell Surfaces. Guest Editors: Lynette Cegelski and David P. Weliky. PMID:24946141

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

2015-01-01

59

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

ERIC Educational Resources Information Center

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,…

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

2004-01-01

60

Heat Management Strategies for Solid-state NMR of Functional Proteins  

PubMed Central

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

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

2012-01-01

61

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

SciTech Connect

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.

Zilm, K.W.

1984-12-01

62

Solid-State NMR Studies of Pharmaceutical Systems  

Microsoft Academic Search

High?and low?resolution solid?state nuclear magnetic resonance (SSNMR) applications to the study of pharmaceuticals are reviewed. Examples are shown involving the use of mono?and bidimensional SSNMR techniques based on different nuclear interactions and the measurement of several nuclear parameters, such as chemical shifts, line widths, and relaxation times (T1, T2, T1?). The systems investigated include pure active pharmaceutical ingredients (APIs), substances

Marco Geppi; Giulia Mollica; Silvia Borsacchi; Carlo Alberto Veracini

2008-01-01

63

Enhancement of solid-state proton NMR via SPINOE with laser-polarized xenon  

E-print Network

We have first successfully transferred the 129Xe polarization of natural isotopic composition to the proton of solid-state 1HCl via Spin Polarization-Induced Nuclear Overhauser Effect (SPINOE), by mixing the hyperpolarized 129Xe gas and the 1HCl gas and then cooling them to their condensated state in a flow system. The solid-state enhanced factor of the NMR signal of 6 for 1H was observed, and the equation of solid-state polarization enhancement via cross relaxation has also been theoretically deduced. Using this equation, the theoretically calculated enhancement is in agreement with the measured value within error. Also, this technique is maybe useful to establish a solid state NMR quantum computer.

Xin Zhou; Jun Luo; Xian-ping Sun; Xi-zhi Zeng; Shang-wu Ding; Mai-li Liu; Ming-sheng Zhan

2004-01-07

64

Sensitivity enhancement using paramagnetic relaxation in MAS solid-state NMR of perdeuterated proteins  

NASA Astrophysics Data System (ADS)

Previously, Ishii et al., could show that chelated paramagnetic ions can be employed to significantly decrease the recycle delay of a MAS solid-state NMR experiment [N.P. Wickramasinghe, M. Kotecha, A. Samoson, J. Past, Y. Ishii, Sensitivity enhancement in C-13 solid-state NMR of protein microcrystals by use of paramagnetic metal ions for optimizing H-1 T-1 relaxation, J. Magn. Reson. 184 (2007) 350-356]. Application of the method is limited to very robust samples, for which sample stability is not compromised by RF induced heating. In addition, probe integrity might be perturbed in standard MAS PRE experiments due to the use of very short duty cycles. We show that these deleterious effects can be avoided if perdeuterated proteins are employed that have been re-crystallized from D 2O:H 2O = 9:1 containing buffer solutions. The experiments are demonstrated using the SH3 domain of chicken ?-spectrin as a model system. The labeling scheme allows to record proton detected 1H, 15N correlation spectra with very high resolution in the absence of heteronuclear dipolar decoupling. Cu-edta as a doping reagent yields a reduction of the recycle delay by up to a factor of 15. In particular, we find that the 1H T1 for the bulk H N magnetization is reduced from 4.4 s to 0.3 s if the Cu-edta concentration is increased from 0 mM to 250 mM. Possible perturbations like chemical shift changes or line broadening due to the paramagnetic chelate complex are minimal. No degradation of our samples was observed in the course of the experiments.

Linser, Rasmus; Chevelkov, Veniamin; Diehl, Anne; Reif, Bernd

2007-12-01

65

Spinning-rate encoded chemical shift correlations from rotational resonance solid-state NMR experiments  

PubMed Central

Structural measurements in magic-angle-spinning (MAS) solid-state NMR rely heavily on 13C-13C distance measurements. Broadbanded recoupling methods are used to generate many cross-peaks, but have complex polarization transfer mechanisms that limit the precision of distance constraints and can suffer from weak intensities for distant peaks due to relaxation, the broad distribution of polarization, as well as dipolar truncation. Frequency-selective methods that feature narrow-banded recoupling can reduce these effects. Indeed, rotational resonance (R2) experiments have found application in many different biological systems, where they have afforded improved precision and accuracy. Unfortunately, a highly selective transfer mechanism also leads to few cross-peaks in the resulting spectra, which complicates the extraction of multiple constraints. R2-width (R2W) measurements that scan a range of MAS rates to probe the R2 matching conditions of one or more sites can improve precision, and also permit multiple simultaneous distance measurements. Unfortunately, multidimensional R2W can be very time-consuming. Here, we present an approach that facilitates the acquisition of 2D-like spectra based on a series of 1D R2W experiments, by taking advantage of the chemical shift information encoded in the MAS rates where matching occurs. This yields a more time-efficient experiment with many of the benefits of more conventional multidimensional R2W measurements. The obtained spectra reveal long-distance 13C-13C cross-peaks resulting from R2-mediated polarization transfer. This experiment also enables the efficient setup and targeted implementation of traditional R2 or R2W experiments. Analogous applications may extend to other variable-MAS and frequency-selective solid-state NMR experiments. PMID:23475055

Li, Jun; van der Wel, Patrick C. A.

2013-01-01

66

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

PubMed

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 prevent dendrite formation. The in situ method was also applied to monitor (by (11)B NMR) electrochemical double-layer formation in supercapacitors in real time. Though this method is useful, it comes with challenges. The separation of the contributions from the different cell components in the NMR spectra is not trivial because of overlapping resonances. In addition, orientation-dependent NMR interactions, including the spatial- and orientation-dependent bulk magnetic susceptibility (BMS) effects, can lead to resonance broadening. Efforts to understand and mitigate these BMS effects are discussed in this Account. The in situ NMR investigation of fuel cells initially focused on the surface electrochemistry at the electrodes and the electrochemical oxidation of methanol and CO to CO2 on the Pt cathode. On the basis of the (13)C and (195)Pt NMR spectra of the adsorbates and electrodes, CO adsorbed on Pt and other reaction intermediates and complete oxidation products were detected and their mode of binding to the electrodes investigated. Appropriate design and engineering of the NMR hardware has allowed researchers to integrate intact direct methanol fuel cells into NMR probes. Chemical transformations of the circulating methanol could be followed and reaction intermediates could be detected in real time by either (2)H or (13)C NMR spectroscopy. By use of the in situ NMR approach, factors that control fuel cell performance, such as methanol cross over and catalyst performance, were identified. PMID:24041242

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

2013-09-17

67

On the acidity of saponite materials: a combined HRTEM, FTIR, and solid-state NMR study.  

PubMed

Acid clays were prepared by exchanging a synthetic saponite in HCl solutions of different concentration (0.01 and 1M, respectively). A combined experimental approach (XRD, HRTEM, N2 physisorption, solid-state MAS NMR, and TGA) was used to investigate on the structural, morphological, and textural features of the samples treated under mild and strong acid conditions. FTIR spectroscopy of adsorbed probe molecules with different basicity (e.g., CO and NH3) was used to monitor the surface acid properties and acid site distribution. XRD and SS-MAS NMR indicated that the activation under mild acid conditions does not alter the clay structure, while a deep modification of the saponite framework occurred after ion exchange in 1 M HCl solution. The presence of porous amorphous silica phase after treatment under strong acid conditions was confirmed by TEM inspection augmented by SS-MAS NMR and FTIR spectroscopy. N2 and Ar physisorption measurements suggested that cavitation phenomena occurred in saponite structure. N2 physisorption confirmed that the porosity and surface area of the samples are strongly modified upon strong acid treatment. FTIR spectroscopy of adsorbed NH3 pointed out that the H-exchange in mild conditions increased the number of surface Brønsted acid sites. Conversely, these sites are significantly depleted after treatment under strong acid conditions. The use of CO as a FTIR probe molecule, which is applied for the first time to study synthetic acid clays, allowed to monitor distribution and strength of Brønsted acid sites, whose acidity is similar to that of strong acid zeolites. The Al-OH sites with medium acidity are also found in acid-activated saponites. The distribution of strong and medium acid sites is strictly dependent on the acid conditions adopted. PMID:18251562

Bisio, C; Gatti, G; Boccaleri, E; Marchese, L; Bertinetti, L; Coluccia, S

2008-03-18

68

Efficient polarization transfer between spin-1/2 and ¹?N nuclei in solid-state MAS NMR spectroscopy.  

PubMed

Polarization transfer between spin-1/2 nuclei and quadrupolar spin-1 nuclei such as (14)N in solid-state NMR is severely challenged by the typical presence of large quadrupole coupling interactions. This has effectively prevented the use of the abundant (14)N spin as a probe to structural information and its use as an element in multi-dimensional solid-state NMR correlation experiments for assignment and structural characterization. In turn, this has been a contributing factor to the extensive use of isotope labeling in biological solid-state NMR, where (14)N is replaced with (15)N. The alternative strategy of using the abundant (14)N spins calls for methods enabling efficient polarization transfer between (14)N and its binding partners. This work demonstrates that the recently introduced (RESPIRATION)CP transfer method can be optimized to achieve efficient (1)H ?(14)N polarization transfer under magic angle spinning conditions. The method is demonstrated numerically and experimentally on powder samples of NH4NO3 and L-alanine. PMID:24880881

Basse, Kristoffer; Jain, Sheetal Kumar; Bakharev, Oleg; Nielsen, Niels Chr

2014-07-01

69

Zinc Solid-State NMR Spectroscopy of Human Carbonic Anhydrase: Implications for the Enzymatic Mechanism.  

SciTech Connect

Many zinc enzymes utilize zinc bound water as a critical component of a catalytic reaction. The Zn2+ ion activates water through ionization, polarization, or simple displacement depending upon the mechanistic details. The fate of one proton from the bound water is determined primarily by the influence of directly bound Zn-ligands, as well as hydrogen bonding with a secondary coordination sphere of side chains and/or bound waters within the protein. We have employed low temperature solid-state 67Zn NMR spectroscopy to probe the nature of the bonding at Zn2+ in human carbonic anhydrase isozyme II (CAII). In particular we wanted to characterize the 67Zn NMR parameters of the metal with both water and hydroxide as the fourth ligand, but instead we show that hydroxide is bound to Zn2+ over the pH range of 5 to 8.5. These results suggest the accepted mechanism of action of CAII needs to be revised. These data serve to provide further understanding of the observed pH dependence of the activity of this well studied protein.

Lipton, Andrew S.; Heck, Robert W.; Ellis, Paul D.

2004-04-14

70

Analysis of cement/waste mixtures with solid-state NMR spectroscopy  

SciTech Connect

We have used solid-state {sup 2}H and {sup 13}C NMR spectroscopy to study the interaction of phenol with portland cement as a function of cure, loading, and hydration. The {sup 2}H NMR of deuterated phenol is used to follow the microscopic dynamics of a phenoxide ion: typically half of the phenoxide ions are freely mobile and half undergo restricted motion, which indicates bonding to the cement matrix. The {sup 13}C NMR, both CP/MAS sideband analysis and static hole-burning NMR, is consistent with this analysis. A new low-temperature, 18 Tesla field-swept NMR has been used to obtain {sup 27}Al NMR resonances that are otherwise difficult to obtain with conventional NMR methods, unfortunately, the resonance is rather featureless at 4.2 K, thus indicating a critical need for VT field-swept NMR.

Cartledge, F.K.; Butler, L.G. [Louisiana State Univ., Baton Rouge, LA (United States)

1995-12-31

71

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

PubMed Central

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

Hu, Kan-Nian; Tycko, Robert

2010-01-01

72

Solid State NMR Studies of Energy Conversion and Storage Materials  

NASA Astrophysics Data System (ADS)

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.

Jankuru Hennadige, Sohan Roshel De Silva

73

Solid State OXYGEN-17 NMR Studies of Hydrate in Biomolecules and Deuterium NMR Studies of Chain Dynamics in Crystalline bis  

NASA Astrophysics Data System (ADS)

There are two parts in this dissertation. In part one (chapter II-V), solid state ^{17 }O (I = 5/2) NMR is established as a useful and complementary approach to ^2H NMR for studying dynamic disorder of water of hydration in biomolecules. A highly efficient probe is designed and constructed from available small components for conducting these experiments. This reliable probe generates intense RF fields with modest RF power and has a good signal to noise ratio (chapter II). Since ^{17 }O has a large quadrupolar coupling constant (Qcc ~ 7 MHz), a density operator formalism including the 2^{rm nd}-order quadrupolar Hamiltonian is developed for analysing excitation of ^{17} O solid state NMR signals for the +1/2 to -1/2 transition. A simple phase cycling echo sequence is developed for reducing the distortion caused by non-uniform excitation and the resultant patterns are compared with experimental spectra (chapter III). To analyze the lineshape of the central transition determined by the motionally averaged 2^{rm nd}-order quadrupolar perturbation, a 4 ^{rm th}-rank order parameter formalism for the fast motion limit (tau _{rm c} < 10^{-5} s) is developed. It is based on angular momentum coupling theory and requires a maximum of 31 order parameters. By a principal axis transformation, this number can be reduced to 8. To study slower motion, we established an adiabatic intermediate exchange theory for tau_ {rm c} ~ 10^{-5} s. The powder patterns calculated from these theories show good agreement when compared to the experimental spectra of several hydrates which undergo simple dynamics (chapter VI-V). In part two (chapter VI), solid state ^2H NMR is applied to explore phase transition related to chain dynamics in (Cd(CH_3CH _2CH_2CH _2NH_3)_2) Cl_4. This layered structure is a crystalline model of a lipid bilayer and was studied from 120K to 350K. Full order tensors for all sites labeled except for C^{(3)} were systematically measured. We find that changes in the chain dynamics are associated with the occurrence of phase transitions. For T < 120K, we find that the chain has an approximately all trans configuration with small "vibration" increasing in amplitude from the polar "head" of the chain to its hydrophilic "tail". For T > 200K, rapid, large amplitude dynamics of the chain vector caused by gauche-trans isomerization leads to significant tilting of the average chain direction. The order tensors are nonaxial showing the absence of axial rotation which is seen in the rotator phase of paraffins and the liquid crystal phase of lipids. In the range of 120K-200K, the symmetry of the dynamics decreases but substantial population of gauche isomers persists. However, the isomerization rate is slow on the ^2H NMR time scale of 10^{-5} s and spectral narrowing is due largely to small amplitude vibrations. The order tensors calculated from x-ray data or the usual "fixed" lattice rotational-isomeric model differ distinctly from the experimental tensors. We propose a flexible lattice model which successfully relates measured order tensors to the chain dynamics.

Zhang, Huiming

1993-01-01

74

Solid state NMR studies of materials for energy technology  

NASA Astrophysics Data System (ADS)

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.

Nambukara Kodiweera Arachchilage, Chandana K.

75

High-resolution solid-state NMR of quadrupolar nuclei  

Microsoft Academic Search

Quadrupolar nuclei are the most abundant nuclear magnetic resonance (NMR)-receptive nuclei in the Earth's crust, and in many amorphous materials of technological interest (such as zeolite catalysts, ceramics and alloys), and have thus been intensively studied1-7. Of particular interest is the ability to resolve and quantitate the various types of sites present in a given material. Here we present a

Eric Oldfield; Hye Kyung C. Timken; Ben Montez; R. Ramachandran

1985-01-01

76

Rapid acquisition of 14N solid-state NMR spectra with broadband cross polarization.  

PubMed

Nitrogen is an element of utmost importance in chemistry, biology and materials science. Of its two NMR-active isotopes, (14)N and (15)N, solid-state NMR (SSNMR) experiments are rarely conducted upon the former, due to its low gyromagnetic ratio (?) and broad powder patterns arising from first-order quadrupolar interactions. In this work, we propose a methodology for the rapid acquisition of high quality (14)N SSNMR spectra that is easy to implement, and can be used for a variety of nitrogen-containing systems. We demonstrate that it is possible to dramatically enhance (14)N NMR signals in spectra of stationary, polycrystalline samples (i.e., amino acids and active pharmaceutical ingredients) by means of broadband cross polarization (CP) from abundant nuclei (e.g., (1)H). The BRoadband Adiabatic INversion Cross-Polarization (BRAIN-CP) pulse sequence is combined with other elements for efficient acquisition of ultra-wideline SSNMR spectra, including Wideband Uniform-Rate Smooth-Truncation (WURST) pulses for broadband refocusing, Carr-Purcell Meiboom-Gill (CPMG) echo trains for T2-driven S/N enhancement, and frequency-stepped acquisitions. The feasibility of utilizing the BRAIN-CP/WURST-CPMG sequence is tested for (14)N, with special consideration given to (i) spin-locking integer spin nuclei and maintaining adiabatic polarization transfer, and (ii) the effects of broadband polarization transfer on the overlapping satellite transition patterns. The BRAIN-CP experiments are shown to provide increases in signal-to-noise ranging from four to ten times and reductions of experimental times from one to two orders of magnitude compared to analogous experiments where (14)N nuclei are directly excited. Furthermore, patterns acquired with this method are generally more uniform than those acquired with direct excitation methods. We also discuss the proposed method and its potential for probing a variety of chemically distinct nitrogen environments. PMID:24123255

Harris, Kristopher J; Veinberg, Stanislav L; Mireault, Christopher R; Lupulescu, Adonis; Frydman, Lucio; Schurko, Robert W

2013-11-25

77

SOLID STATE NMR STUDY SUPPORTING THE LITHIUM VACANCY DEFECT MODEL IN CONGRUENT LITHIUM  

E-print Network

@ Pergamon SOLID STATE NMR STUDY SUPPORTING THE LITHIUM VACANCY DEFECT MODEL IN CONGRUENT LITHIUM performed on powdered and single crystal lithium niobate of defectivecongruent composition (48.4%LirO;51.6% NbrOr) using a magnetic field strength of 7.05 Tesla with the aim to distinguish between a lithium

Bluemel, Janet

78

Heteronuclear Recoupling in Solid-State Magic-Angle-Spinning NMR via Overtone Irradiation  

E-print Network

Heteronuclear Recoupling in Solid-State Magic-Angle-Spinning NMR via Overtone Irradiation Sungsool undergoing magic-angle- spinning (MAS) is introduced, based on the overtone irradiation of one of the coupled nuclei. It is shown that when I is a quadrupole, for instance 14N, irradiating this spin at a multiple

Frydman, Lucio

79

Adsorption of Ruthenium and Iron Metallocenes on Silica: A Solid-State NMR Study  

E-print Network

Adsorption of Ruthenium and Iron Metallocenes on Silica: A Solid- State NMR Study Kyle J. Cluff, College Station, Texas 77842-3012, United States *S Supporting Information ABSTRACT: Ruthenocene, bis(indenyl)ruthenium, bis(tetrahydroindenyl)- ruthenium, cyclododecane, ferrocene, and ferrocene-d2 have been adsorbed

Bluemel, Janet

80

Using multivariate methods on solid-state 13C NMR data of complex materials  

Microsoft Academic Search

Multivariate data analysis (MVA) has been used as an aid in the analysis and interpretation of 13C NMR spectra in the solid state. The goal of this study was to investigate the effect of some important instrumental parameters and calculation strategies on the outcome of the multivariate data analysis. The samples used were two peat forming plants, Sphagnumfuscum and Carex

Hans Karlström; Mats Nilsson; Bo Nordén

1995-01-01

81

Selective averaging for high-resolution solid-state NMR spectroscopy of aligned samples  

Microsoft Academic Search

Solid-state NMR experiments benefit from being performed at high fields, and this is essential in order to obtain spectra with the resolution and sensitivity required for applications to protein structure determination in aligned samples. Since the amount of rf power that can be applied is limited, especially for aqueous protein samples, the most important pulse sequences suffer from bandwidth limitations

Alexander A. Nevzorov

2007-01-01

82

Selective averaging for high-resolution solid-state NMR spectroscopy of aligned samples  

Microsoft Academic Search

Solid-state NMR experiments benefit from being performed at high fields, and this is essential in order to obtain spectra with the resolution and sensitivity required for applications to protein structure determination in aligned samples. Since the amount of rf power that can be applied is limited, especially for aqueous protein samples, the most important pulse sequences suffer from bandwidth limi-

Alexander A. Nevzorov

2006-01-01

83

Multidimensional solid-state NMR studies of the structure and dynamics of pectic  

E-print Network

-angle-spinning (MAS) solid-state NMR (SSNMR) to investigate the structural role of pectins in the plant CW. Intact of pectin signals, confirming partial pectin removal by chelating agents and sodium carbonate. Importantly of the primary CW with mobility and flexibility, which may be important for pectin functions. This study

Hong, Mei

84

Improved magnetization transfer in solid-state NMR with fast magic angle spinning Markus Weingarth a  

E-print Network

Improved magnetization transfer in solid-state NMR with fast magic angle spinning Markus Weingarth between different spins S such as chemically inequivalent car- bon-13 nuclei in solid samples that are spinning at high frequencies about the magic angle can be enhanced by a phase-alternated recoupling

85

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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...

86

Solid-State 25Mg NMR of a Magnesium(II) Adensosine 5-Triphosphate Complex  

E-print Network

Solid-State 25Mg NMR of a Magnesium(II) Adensosine 5-Triphosphate Complex Christopher V. Grant interacting with RNA, such as magnesium- (II) binding sites within ribozymes, has become a topic of intense such as magnesium(II). X-ray crystallography has been most useful at providing structural information about

Frydman, Lucio

87

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

PubMed Central

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. PMID:12202372

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

2002-01-01

88

Structural characterization of water-bearing silicate and aluminosilicate glasses by high-resolution solid-state NMR  

E-print Network

-resolution solid-state NMR Eric Robert1, , a , Alan Whittington2, , a, , b , Franck Fayona , Michel Pichavantc-resolution solid-state NMR techniques have been applied to hydrous silicate and aluminosilicate glasses: simple acquisition, cross-polarization (CP-MAS), heteronuclear correlation (HETCOR), dipolar dephasing, spin counting

Boyer, Edmond

89

Orientation and Dynamics of an Antimicrobial Peptide in the Lipid Bilayer by Solid-State NMR Spectroscopy  

E-print Network

Orientation and Dynamics of an Antimicrobial Peptide in the Lipid Bilayer by Solid-State NMR and dynamics of an 18-residue antimicrobial peptide, ovispirin, has been investigated using solid-state NMR for understanding the antimicrobial function of this peptide. INTRODUCTION Antimicrobial peptides of mammalian

Hong, Mei

90

Structure and mechanism of b-hairpin antimicrobial peptides in lipid bilayers from solid-state NMR spectroscopy  

E-print Network

Structure and mechanism of b-hairpin antimicrobial peptides in lipid bilayers from solid-state NMR, and dynamics of the arginine-rich b-hairpin antimicrobial peptide PG-1 as studied by solid-state NMR of this representative b-hairpin antimicrobial peptide. We found that PG-1 structure is membrane dependent: in bacteria

Hong, Mei

91

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

PubMed

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 (?E) of the double-well potential, ?E = 3.0 ± 0.5 kJ/mol. We were also able to determine a lower limit of ?E for salicylic acid, ?E > 10 kJ/mol. These asymmetrical features in potential energy curves were confirmed by plane-wave DFT computations, which yielded ?E = 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. PMID:23879687

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

2013-08-22

92

Solid-state 19F-NMR analysis of 19F-labeled tryptophan in gramicidin A in oriented membranes.  

PubMed Central

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

Grage, Stephan L; Wang, Junfeng; Cross, Timothy A; Ulrich, Anne S

2002-01-01

93

Genetic algorithms and solid state NMR pulse sequences  

E-print Network

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 C7 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 C7 pulse sequence. The optimised pulse sequence breaks the synchronicity between r.f. pulses and sample spinning.

Bechmann, Matthias; Sebald, Angelika

2013-01-01

94

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

SciTech Connect

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.

Garbow, J.R.; Fujiwara, Hideji; Sharp, C.R.; Logusch, E.W. (Monsanto Co., St. Louis, MO (United States))

1991-07-23

95

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

PubMed

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. PMID:25194346

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

2014-11-01

96

Measurement of long-range interatomic distances by solid-state tritium-NMR spectroscopy.  

PubMed

For the structural determination of a ligand bound to an amorphous macromolecular system, solid-state NMR can be used to provide interatomic distances. It is shown here that selective labeling in discrete locations with tritium enables accurate measurement of long-range distances owing to the high gyromagnetic ratio of this nucleus, without structural modification of the molecule. This approach gives access to the largest NMR distance ever measured between two nuclei (14.4 A). (3)H MAS NMR appears to be a promising tool for structural applications in the biological and material sciences. PMID:20092274

Yuen, Alexander K L; Lafon, Olivier; Charpentier, Thibault; Roy, Myriam; Brunet, Francine; Berthault, Patrick; Sakellariou, Dimitrios; Robert, Bruno; Rimsky, Sylvie; Pillon, Florence; Cintrat, Jean-Christophe; Rousseau, Bernard

2010-02-17

97

Time-resolved solid-state REDOR NMR studies of UDP N-acetylglucosamine enolpyruvyl transferase.  

PubMed

The new method of time-resolved solid-state rotational echo double resonance (REDOR) NMR spectroscopy introduced recently by this laboratory has been applied to the enzyme uridine N-acetylglucosamine (UDP-NAG) enolpyruvyl transferase (EPT), with the goal of probing the interactions between reactive species and their enzyme active site. The approach has been used in a qualitative fashion with the enzyme-inhibitor and enzyme-intermediate complexes of uniformly 15N-labeled UDP-NAG EPT, trapped under steady-state and pre-steady-state conditions. A different set of intermolecular interactions between the substrates UDP-NAG, UDP-NAG plus 3-Z-fluorophosphoenolpyruvate, covalent O-phosphothioketal, and UDP-NAG plus phosphoenolpyruvate trapped under time-resolved conditions (after 50 ms reaction time), and the EPT enzyme active site were observed, and this is contrasted to a similar study of the interactions in a related enzyme, 5-enolpyruvyl-shikimate-3-phosphate synthase. PMID:8543052

Li, Y; Krekel, F; Ramilo, C A; Amrhein, N; Evans, J N

1995-12-18

98

Probing lead(II) bonding environments in 4-substituted pyridine adducts of (2,6-Me2C6H3S)2Pb: an X-ray structural and solid-state 207Pb NMR study.  

PubMed

The effect of subtle changes in the sigma-electron donor ability of 4-substituted pyridine ligands on the lead(II) coordination environment of (2,6-Me(2)C(6)H(3)S)(2)Pb (1) adducts has been examined. The reaction of 1 with a series of 4-substituted pyridines in toluene or dichloromethane results in the formation of 1:1 complexes [(2,6-Me(2)C(6)H(3)S)(2)Pb(pyCOH)](2) (3), [(2,6-Me(2)C(6)H(3)S)(2)Pb(pyOMe)](2) (4), and (2,6-Me(2)C(6)H(3)S)(2)Pb(pyNMe(2)) (5) (pyCOH = 4-pyridinecarboxaldehyde; pyOMe = 4-methoxypyridine; pyNMe2 = 4-dimethylaminopyridine), all of which have been structurally characterized by X-ray crystallography. The structures of 3 and 4 are dimeric and have psi-trigonal bipyramidal S(3)N bonding environments, with the 4-substituted pyridine nitrogen and bridging sulfur atoms in axial positions and two thiolate sulfur atoms in equatorial sites. Conversely, compound 5 is monomeric and exhibits a psi-trigonal pyramidal S(2)N bonding environment at lead(II). The observed structures may be rationalized in terms of a simple valence bond model and the sigma-electron donor ability of the 4-pyridine ligands as derived from the analysis of proton affinity values. Solid-state (207)Pb NMR experiments are applied in combination with density functional theory (DFT) calculations to provide further insight into the nature of bonding in 4, 5, and (2,6-Me(2)C(6)H(3)S)(2)Pb(py)(2) (2). The lead chemical shielding (CS) tensor parameters of 2, 4, and 5 reveal some of the largest chemical shielding anisotropies (CSA) observed in lead coordination complexes to date. DFT calculations using the Amsterdam Density Functional (ADF) program, which take into account relativistic effects using the zeroth-order regular approximation (ZORA), yield lead CS tensor components and orientations. Paramagnetic contributions to the lead CS tensor from individual pairs of occupied and virtual molecular orbitals (MOs) are examined to gain insight into the origin of the large CSA. The CS tensor is primarily influenced by mixing of the occupied MOs localized on the sulfur and lead atoms with virtual MOs largely comprised of lead 6p orbitals. PMID:17867676

Briand, Glen G; Smith, Andrew D; Schatte, Gabriele; Rossini, Aaron J; Schurko, Robert W

2007-10-15

99

Immobilization of Carbonylnickel Complexes: A Solid-State NMR Study K. D. Behringer and J. Blu1mel*  

E-print Network

oxidation or cross-linking, and therefore narrow NMR lines, and it allows 13C CP/MAS NMR spectroscopy. 1Immobilization of Carbonylnickel Complexes: A Solid-State NMR Study K. D. Behringer and J. Blu1mel- and tricarbonylnickel complexes of these ligands are synthesized, characterized by 61Ni, 31P, 13C, and 1H NMR and IR

Bluemel, Janet

100

Membrane structure and dynamics as viewed by solid-state NMR spectroscopy.  

PubMed

The purpose of the present study is the investigation of the structure and dynamics of biological membranes using solid-state nuclear magnetic resonance (NMR) spectroscopy. Two approaches are used in our laboratory. The first involves the measurement of high-resolution 13C and 1H spectra obtained by the magic angle spinning (MAS) technique while the second approach involves the measurement of 31P and 2H powder spectra in static samples. This paper will present some recent results obtained by high-resolution solid-state 1H NMR on the conformation of gramicidin A incorporated in a phosphatidylcholine bilayers. More specifically, we were able to observe changes in the gramicidin spectra as a function of the cosolubilization solvent initially used to prepare the samples. The interaction between lipid bilayers and an anticancer drug derived from chloroethylurea was also investigated using proton NMR spectroscopy. Finally, we have studied the interaction between cardiotoxin, a toxic protein extracted from snake venom, and negatively charged lipid bilayers using 31P solid-state NMR spectroscopy. PMID:9468622

Auger, M

1997-10-01

101

PFG-assisted selection and suppression of 1H NMR signals in the solid state under fast MAS  

NASA Astrophysics Data System (ADS)

Under fast MAS conditions, techniques for 1H signal selection and suppression, which have originally been developed for solution-state NMR, become applicable to solids. In this work, we describe how WATERGATE and DANTE pulse sequences can be used under MAS to selectively excite or suppress peaks in 1H solid-state spectra. As known from the liquid-state analogues, signal selection and/or suppression is supported by pulsed-field gradients which selectively dephase and rephase transverse magnetisation. Under MAS, the required field gradients are provided by a simple pair of coils which have been built into a standard fast-MAS probe. PFG-assisted techniques enable efficient selection or suppression of 1H peaks in a single transient of the pulse sequence without the need for phase cycles. Therefore, these tools can readily be incorporated into solid-state MAS NMR experiments, which is demonstrated here for 1H- 1H double-quantum NMR spectra of supramolecular systems. In the examples presented here, the 1H signals of interest are relatively weak and need to be observed despite the presence of the strong 1H signal of long alkyl sidechains. PFG-assisted suppression of this strong perturbing signal is shown to be particularly useful for obtaining unambiguous results.

Fischbach, Ingrid; Thieme, Karena; Hoffmann, Anke; Hehn, Manfred; Schnell, Ingo

2003-11-01

102

PFG-assisted selection and suppression of 1H NMR signals in the solid state under fast MAS.  

PubMed

Under fast MAS conditions, techniques for 1H signal selection and suppression, which have originally been developed for solution-state NMR, become applicable to solids. In this work, we describe how WATERGATE and DANTE pulse sequences can be used under MAS to selectively excite or suppress peaks in 1H solid-state spectra. As known from the liquid-state analogues, signal selection and/or suppression is supported by pulsed-field gradients which selectively dephase and rephase transverse magnetisation. Under MAS, the required field gradients are provided by a simple pair of coils which have been built into a standard fast-MAS probe. PFG-assisted techniques enable efficient selection or suppression of 1H peaks in a single transient of the pulse sequence without the need for phase cycles. Therefore, these tools can readily be incorporated into solid-state MAS NMR experiments, which is demonstrated here for 1H-1H double-quantum NMR spectra of supramolecular systems. In the examples presented here, the 1H signals of interest are relatively weak and need to be observed despite the presence of the strong 1H signal of long alkyl sidechains. PFG-assisted suppression of this strong perturbing signal is shown to be particularly useful for obtaining unambiguous results. PMID:14568521

Fischbach, Ingrid; Thieme, Karena; Hoffmann, Anke; Hehn, Manfred; Schnell, Ingo

2003-11-01

103

13C NMR study of spirostanes and furostanes in solution and solid state  

Microsoft Academic Search

A series of compounds deriving from 12?- and 12?-hydroxytigogenin (1, 2), pseudohecogenin 6, 23-bromo derivatives of hecogenin and sarsapogenin (3–5) and products (7–9) of their transformation was analysed by 13C NMR in solution and in the solid state. The model structures containing three or four rings have been calculated by DFT B3LYP\\/6-31G** method. On the basis of the GIAO DFT

Jacek W. Morzycki; Katarzyna Paradowska; Karolina Dabrowska-Balcerzak; Izabella Jastrzebska; Leszek Siergiejczyk; Iwona Wawer

2005-01-01

104

A solid state NMR study of locust bean gum galactomannan and Konjac glucomannan gels  

Microsoft Academic Search

This paper describes a 13C solid state NMR study of hydrated powders and gels of locust bean gum galactomannan-LBG and Konjac glucomannan-KGM. Changes in relative spectral intensities, cross-polarization dynamics (TCH, T1?H) and relaxation times (T1C, T1H, T2H) show that hydration (0–90%) of LBG powders increases the 108Hz frequency molecular motions, probably reflecting the enhanced motion of non-aggregating segments and chain

M. C. Vieira; A. M. Gil

2005-01-01

105

Applications of Solid-State NMR to the Study of Organic\\/Inorganic Multicomponent Materials  

Microsoft Academic Search

The characterization of a variety of organic\\/inorganic multicomponent materials (OIMM) through solid-state NMR (SSNMR) spectroscopy will be reviewed. Many examples of applications to OIMM will be described, based on the observation of different nuclei and the use of various SSNMR methods, such as 1D and 2D techniques, measurements on relaxation and spin diffusion processes. OIMM are a very general category

Marco Geppi; Silvia Borsacchi; Giulia Mollica; Carlo Alberto Veracini

2009-01-01

106

Radiation oxidation of polypropylene: A solid-state 13C NMR study using selective isotopic labeling  

Microsoft Academic Search

Polypropylene samples, in which the three different carbon atoms along the chain were selectively labeled with carbon-13, were subjected to radiation under inert and air atmospheres, and to post-irradiation exposure in air at various temperatures. By using solid-state 13C NMR measurements at room temperature, we have been able to identify and quantify the oxidation products. The isotopic labeling provides insight

Daniel M. Mowery; Roger A. Assink; Dora K. Derzon; Sara B. Klamo; Robert Bernstein; Roger L. Clough

2007-01-01

107

Structures of Amyloid Fibrils and Protein Folding Intermediates: New Insights from Solid State NMR  

NASA Astrophysics Data System (ADS)

I will present recent results from two projects: (1) We are using a combination of solid state NMR techniques and electron microscopy techniques to develop full molecular models for amyloid fibrils formed by the beta-amyloid peptide of Alzheimer's disease and by other peptides and proteins. Amyloid fibrils are often polymorphic, so that the detailed molecular structure depends on growth conditions or other factors. I will describe two structural models for beta-amyloid fibrils with two distinct morphologies. I will also describe efforts to determine which fibril structure develops in the brains of Alzheimer's disease patients, and solid state NMR methods that contribute to our amyloid studies; (2) Structural properties of unfolded or partially folded states of proteins are not well understood. In principle, solid state NMR measurements on freeze-trapped samples can reveal site-specific, quantitative aspects of protein structures in unfolded states. I will describe experiments on thermodynamically unfolded states (i.e., denatured states) and on transient states that are trapped by freezing on the microsecond time scale. Both types of experiments reveal structural properties that are unanticipated and could not be detected by more conventional protein folding measurements.

Tycko, Robert

2009-03-01

108

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

SciTech Connect

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.

Lu, George J.; Opella, Stanley J., E-mail: sopella@ucsd.edu [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0307 (United States)

2014-03-28

109

(35)Cl solid-state NMR of halide ionic liquids at ultrahigh fields.  

PubMed

This Letter describes recent work investigating the solid-state NMR spectra of (35)Cl nuclei in an assortment of ionic liquids under static and MAS conditions at field strengths of 9.4 and 21.1 T. At high field it was possible to resolve and extract information from multiple unique crystallographic sites and to resolve otherwise complex spectra that were analyzed to extract information regarding the electric field gradient (EFG) and chemical shift tensors, including their relative orientation. The NMR parameters were found to be typical of organic salts in general. PMID:19007195

Gordon, Peter G; Brouwer, Darren H; Ripmeester, John A

2008-12-11

110

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

PubMed Central

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

2013-01-01

111

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

PubMed

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. PMID:24398051

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

2014-01-01

112

[superscript 2]H-DNP-enhanced [superscript 2]H-[superscript 13]C solid-state NMR correlation spectroscopy  

E-print Network

Perdeuteration of biological macromolecules for magic angle spinning solid-state NMR spectroscopy can yield high-resolution [superscript 2]H–[superscript 13]C correlation spectra and the method is therefore of great interest ...

Maly, Thorsten

113

Correlation of solid-state NMR relaxation times to functional properties such as chemical stability and particle size  

E-print Network

The purpose of the work presented in this dissertation was to investigate the correlation between the particle size of crystalline active pharmaceutical ingredients (APIs) and their solid-state NMR (SSNMR) proton spin-lattice ...

Dempah, Kassibla Elodie

2013-05-31

114

Probing Surface Charge Fluctuations with Solid-State Nanopores  

PubMed Central

We identify a contribution to the ionic current noise spectrum in solid-state nanopores that exceeds all other noise sources in the frequency band 0.1–10 kHz. Experimental studies of the dependence of this excess noise on pH and electrolyte concentration indicate that the noise arises from surface charge fluctuations. A quantitative model based on surface functional group protonization predicts the observed behaviors and allows us to locally measure protonization reaction rates. This noise can be minimized by operating the nanopore at a deliberately chosen pH. PMID:19659110

Hoogerheide, David P.; Garaj, Slaven; Golovchenko, Jene A.

2009-01-01

115

Quantitative identification of metastable magnesium carbonate minerals by solid-state (13)c NMR spectroscopy.  

PubMed

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. PMID:25437754

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

2015-01-01

116

Interaction of epicatechin gallate with phospholipid membranes as revealed by solid-state NMR spectroscopy.  

PubMed

Epicatechin gallate (ECg), a green tea polyphenol, has various physiological effects. Our previous nuclear Overhauser effect spectroscopy (NOESY) study using solution NMR spectroscopy demonstrated that ECg strongly interacts with the surface of phospholipid bilayers. However, the dynamic behavior of ECg in the phospholipid bilayers has not been clarified, especially the dynamics and molecular arrangement of the galloyl moiety, which supposedly has an important interactive role. In this study, we synthesized [13C]-ECg, in which the carbonyl carbon of the galloyl moiety was labeled by 13C isotope, and analyzed it by solid-state NMR spectroscopy. Solid-state 31P NMR analysis indicated that ECg changes the gel-to-liquid-crystalline phase transition temperature of DMPC bilayers as well as the dynamics and mobility of the phospholipids. In the solid-state 13C NMR analysis under static conditions, the carbonyl carbon signal of the [13C]-ECg exhibited an axially symmetric powder pattern. This indicates that the ECg molecules rotate about an axis tilting at a constant angle to the bilayer normal. The accurate intermolecular-interatomic distance between the labeled carbonyl carbon of [13C]-ECg and the phosphorus of the phospholipid was determined to be 5.3±0.1 Å by 13C-(31)P rotational echo double resonance (REDOR) measurements. These results suggest that the galloyl moiety contributes to increasing the hydrophobicity of catechin molecules, and consequently to high affinity of galloyl-type catechins for phospholipid membranes, as well as to stabilization of catechin molecules in the phospholipid membranes by cation-? interaction between the galloyl ring and quaternary amine of the phospholipid head-group. PMID:21352801

Uekusa, Yoshinori; Kamihira-Ishijima, Miya; Sugimoto, Osamu; Ishii, Takeshi; Kumazawa, Shigenori; Nakamura, Kozo; Tanji, Ken-ichi; Naito, Akira; Nakayama, Tsutomu

2011-06-01

117

Solution and solid-state NMR studies of some cadmium-selenone complexes  

NASA Astrophysics Data System (ADS)

Cadmium(II) complexes of Imidazolidine-2-selenone (ImSe) and its derivatives have been prepared with the general formula Cd(RImSe) 2Cl 2 (where R = Me, Et, Pr, etc.). These complexes are characterized by elemental analysis, IR and NMR ( 1H, 13C, 77Se and 113Cd) spectroscopy. An upfield shift in C=Se resonance of selenones in 13C NMR and in 77Se and high-frequency shifts in N-H resonances in 1H are consistent with the selenium coordination to Cd(II). The 77Se nucleus in Cd(ImSe) 2Cl 2 is shielded by 38 ppm on coordination, relative to the free ligand. The principal components of the 77Se, 113Cd and 13C shielding tensors for the complexes were determined from solid-state NMR data. Large selenium chemical shift anisotropies were observed for these complexes.

Wazeer, Mohammed I. M.; Isab, Anvarhusein A.

2005-12-01

118

Solution and solid-state NMR studies of some cadmium-selenone complexes.  

PubMed

Cadmium(II) complexes of Imidazolidine-2-selenone (ImSe) and its derivatives have been prepared with the general formula Cd(RImSe)2Cl2 (where R=Me, Et, Pr, etc.). These complexes are characterized by elemental analysis, IR and NMR (1H, 13C, 77Se and 113Cd) spectroscopy. An upfield shift in C=Se resonance of selenones in 13C NMR and in 77Se and high-frequency shifts in N-H resonances in 1H are consistent with the selenium coordination to Cd(II). The 77Se nucleus in Cd(ImSe)2Cl2 is shielded by 38 ppm on coordination, relative to the free ligand. The principal components of the 77Se, 113Cd and 13C shielding tensors for the complexes were determined from solid-state NMR data. Large selenium chemical shift anisotropies were observed for these complexes. PMID:15950525

Wazeer, Mohammed I M; Isab, Anvarhusein A

2005-12-01

119

Temperature-resistant bicelles for structural studies by solid-state NMR spectroscopy.  

PubMed

Three-dimensional structure determination of membrane proteins is important to fully understand their biological functions. However, obtaining a high-resolution structure has been a major challenge mainly due to the difficulties in retaining the native folding and function of membrane proteins outside of the cellular membrane environment. These challenges are acute if the protein contains a large soluble domain, as it needs bulk water unlike the transmembrane domains of an integral membrane protein. For structural studies on such proteins either by nuclear magnetic resonance (NMR) spectroscopy or X-ray crystallography, bicelles have been demonstrated to be superior to conventional micelles, yet their temperature restrictions attributed to their thermal instabilities are a major disadvantage. Here, we report an approach to overcome this drawback through searching for an optimum combination of bicellar compositions. We demonstrate that bicelles composed of 1,2-didecanoyl-sn-glycero-3-phosphocholine (DDPC) and 1,2-diheptanoyl-sn-glycero-3-phosphocholin (DHepPC), without utilizing additional stabilizing chemicals, are quite stable and are resistant to temperature variations. These temperature-resistant bicelles have a robust bicellar phase and magnetic alignment over a broad range of temperatures, between -15 and 80 °C, retain the native structure of a membrane protein, and increase the sensitivity of solid-state NMR experiments performed at low temperatures. Advantages of two-dimensional separated-local field (SLF) solid-state NMR experiments at a low temperature are demonstrated on magnetically aligned bicelles containing an electron carrier membrane protein, cytochrome b5. Morphological information on different DDPC-based bicellar compositions, varying q ratio/size, and hydration levels obtained from (31)P NMR experiments in this study is also beneficial for a variety of biophysical and spectroscopic techniques, including solution NMR and magic-angle-spinning (MAS) NMR for a wide range of temperatures. PMID:25565453

Yamamoto, Kazutoshi; Pearcy, Paige; Lee, Dong-Kuk; Yu, Changsu; Im, Sang-Choul; Waskell, Lucy; Ramamoorthy, Ayyalusamy

2015-02-01

120

Sensitivity and resolution enhancement of oriented solid-state NMR: application to membrane proteins.  

PubMed

Oriented solid-state NMR (O-ssNMR) spectroscopy is a major technique for the high-resolution analysis of the structure and topology of transmembrane proteins in native-like environments. Unlike magic angle spinning (MAS) techniques, O-ssNMR spectroscopy requires membrane protein preparations that are uniformly oriented (mechanically or magnetically) so that anisotropic NMR parameters, such as dipolar and chemical shift interactions, can be measured to determine structure and orientation of membrane proteins in lipid bilayers. Traditional sample preparations involving mechanically aligned lipids often result in short relaxation times which broaden the (15)N resonances and encumber the manipulation of nuclear spin coherences. The introduction of lipid bicelles as membrane mimicking systems has changed this scenario, and the more favorable relaxation properties of membrane protein (15)N and (13)C resonances make it possible to develop new, more elaborate pulse sequences for higher spectral resolution and sensitivity. Here, we describe our recent progress in the optimization of O-ssNMR pulse sequences. We explain the theory behind these experiments, demonstrate their application to small and medium size proteins, and describe the technical details for setting up these new experiments on the new generation of NMR spectrometers. PMID:24160761

Gopinath, T; Mote, Kaustubh R; Veglia, Gianluigi

2013-11-01

121

Solid-state {sup 29}Si NMR analysis of amorphous silicon nitride powder  

SciTech Connect

Solid-state {sup 29}Si NMR techniques were used to characterize laser-synthesized silicon nitride powder prepared from the reaction of silane with ammonia. When the powder is exposed to water vapor, a hydrated layer rapidly forms at the surface. A comparison of {sup 29}Si cross polarization (CP) and Bloch decay (BD)-MAS-NMR spectra revealed differences between surface and bulk compositions. CP-NMR identified Si-NH{sub x} (x = 1, 2) species with a chemical shift of {minus}45 ppm in the as-synthesized (unexposed) powder. In BD-NMR spectra, the nitride resonance is observed at {minus}48 ppm. For the hydrated powder, CP-NMR identified additional {triple_bond}Si-OH (Q{sup 3}), {double_bond}Si-(OH){sub 2} (Q{sup 2}), and SiO{sub 2} (Q{sup 4}) species present at the surface. The CP-NMR spectra were corrected for T{sub 1pH} relaxation effects and deconvoluted into individual components in order to extract quantitative measurements of the various species present.

Leone, E.A.; Curran, S.; Kotun, M.E. [AlliedSignal Inc., Morristown, NJ (United States); Carrasquillo, G.; Weeren, R. van; Danforth, S.C. [Rutgers-the State Univ., Piscataway, NJ (United States). Center for Ceramic Research

1996-02-01

122

Characterisation of coke from FCC catalysts by solid state {sup 13}C NMR and mass spectrometry  

SciTech Connect

Coke has been concentrated by demineralisation from deactivated FCC catalysts from both refinery operations with actual feeds and MAT tests using n-hexadecane to facilitate detailed characterisation by solid state {sup 13}C NMR and mass spectrometry. All the catalysts investigated contained about 1% w/w carbon. As for solid fuels, the use of a low-field spectrometer for solid state {sup 13}C NMR in conjunction with the single pulse excitation (SPE or Bloch decay) technique has enabled quantitative carbon skeletal parameters to be obtained for the cokes. Internal standard measurements demonstrated that most of the carbon was observed by SPE and, therefore, NMR-invisible graphitic layers are not thought to be major structural features of the cokes. Differences in feedstock composition were reflected in the structure of the refinery cokes with the aromatic nuclei from a residue feed (5% Conradson carbon) corresponding to 15-20 peri-condensed aromatic rings and being more highly condensed than those from a hydrotreated vacuum gas oil. Mass spectrometry (EI, CI and FIMS) has confirmed that the refinery cokes are highly condensed, but those obtained from n-hexadecane in the MAT tests displayed significant aliphatic character.

Andresen, J.M.; McGhee, B.; Snape, C.E. [Univ. of Strathclyde, Glasgow (United Kingdom)] [and others

1995-12-31

123

Identification of lipid and saccharide constituents of whole microalgal cells by ¹³C solid-state NMR.  

PubMed

Microalgae are unicellular organisms in which plasma membrane is protected by a complex cell wall. The chemical nature of this barrier is important not only for taxonomic identification, but also for interactions with exogenous molecules such as contaminants. In this work, we have studied freshwater (Chlamydomonas reinhardtii) and marine (Pavlova lutheri and Nannochloropsis oculata) microalgae with different cell wall characteristics. C. reinhardtii is covered by a network of fibrils and glycoproteins, while P. lutheri is protected by small cellulose scales, and the picoplankton N. oculata by a rigid cellulose wall. The objective of this work was to determine to what extent the different components of these microorganisms (proteins, carbohydrates, lipids) can be distinguished by ¹³C solid-state NMR with an emphasis on isolating the signature of their cell walls and membrane lipid constituents. By using NMR experiments which select rigid or mobile zones, as well as ¹³C-enriched microalgal cells, we improved the spectral resolution and simplified the highly crowded spectra. Interspecies differences in cell wall constituents, storage sugars and membrane lipid compositions were thus evidenced. Carbohydrates from the cell walls could be distinguished from those incorporated into sugar reserves or glycolipids. Lipids from the plasmalemma and organelle membranes and from storage vacuoles could also be identified. This work establishes a basis for a complete characterization of phytoplankton cells by solid-state NMR. PMID:25065670

Arnold, Alexandre A; Genard, Bertrand; Zito, Francesca; Tremblay, Réjean; Warschawski, Dror E; Marcotte, Isabelle

2015-01-01

124

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

PubMed

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. This article is part of a Special Issue entitled: NMR Spectroscopy for Atomistic Views of Biomembranes and Cell Surfaces. Guest Editors: Lynette Cegelski and David P. Weliky. PMID:24915020

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

2015-01-01

125

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

PubMed

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. PMID:25093693

Tošner, Zden?k; Andersen, Rasmus; Stevensson, Baltzar; Edén, Mattias; Nielsen, Niels Chr; Vosegaard, Thomas

2014-09-01

126

Dynamic Effects on the Powder Line Shapes of Half-Integer Quadrupolar Nuclei: A Solid-State NMR Study of XO4  

E-print Network

Dynamic Effects on the Powder Line Shapes of Half-Integer Quadrupolar Nuclei: A Solid-State NMR, Chicago, Illinois 60607 ReceiVed: August 6, 2001 Multinuclear solid-state nuclear magnetic resonance interest in the solid- state NMR of half-integer quadrupolar nuclei.8-13 This is partly due

Frydman, Lucio

127

Homogeneous nanoparticles to enhance the efficiency of a hydrophobic drug, anti-hyperlipidemic Probucol, characterized by solid-state NMR  

PubMed Central

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 a high-resolution by magic angle spinning solid-state NMR experiments. PMID:19938876

Io, Takeshi; Fukami, Toshiro; Yamamoto, Kazutoshi; Suzuki, Toyofumi; Xu, Jiadi; Tomono, Kazuo; Ramamoorthy, Ayyalusamy

2009-01-01

128

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

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

129

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

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

130

Efficient decoupling and recoupling in solid state NMR for quantum computation  

E-print Network

A scheme for decoupling and selectively recoupling large networks of dipolar-coupled spins is proposed. The scheme relies on a combination of broadband, decoupling pulse sequences applied to all the nuclear spins with a band-selective pulse sequence for single spin rotations or recoupling. The evolution-time overhead required for selective coupling is independent of the number of spins, subject to time-scale constraints, for which we discuss the feasibility. This scheme may improve the scalability of solid-state-NMR quantum computing architectures.

Fumiko Yamaguchi; Thaddeus D. Ladd; Cyrus P. Master; Yoshihisa Yamamoto; Navin Khaneja

2004-11-15

131

Solid-state NMR as a spectroscopic tool for characterizing phosphane-borane frustrated lewis pairs.  

PubMed

Frustrated Lewis pair (FLP) chemistry has provided a new strategy for small molecule binding and/or catalytic activation. It is based on the cooperative reaction behavior of Lewis acid and Lewis base centers that are in close proximity to each other (e.g., within the same molecule) but cannot form a direct bond because of geometrical constraints. The most prominent FLPs are based on intramolecular phosphane-borane adducts, whose catalytic properties can be tailored over wide ranges of reactivity and selectivity. For the structural and chemical design of such systems, a fundamental understanding needs to be developed on how structure, dynamics and covalent interactions between the Lewis centers influence the reactivity profile. Advanced solid-state nuclear magnetic resonance (NMR) spectroscopic techniques afford new opportunities for addressing this challenge. Following a general introduction into the fundamentals of NMR spectroscopy, this review discusses the different types of internal interactions - magnetic shielding, nuclear electric quadrupolar coupling, indirect spin-spin interactions, and "through-space" dipole-dipole couplings - influencing NMR spectra in the solid state. As discussed in detail, each type of interaction bears specific informational content with regard to structural issues in FLP chemistry. One of the most attractive features of solid-state NMR is the possibility of tailoring the effective Hamiltonian by manipulations in either physical space or spin space. Using such "decoupling" or "recoupling" techniques certain types of interactions can be selectively turned off for spectral simplification or turned on for selective evaluation. The present review summarizes the most important selective averaging techniques that have found applications in the characterization of FLPs. In a second step the interaction parameters need to be connected with structure and bonding information. As illustrated in this chapter, ab initio calculations using density functional theory (DFT) methods have become indispensable for this task. Based on this comprehensive strategy including advanced NMR methodology, computer simulations, and ab initio calculations, the present review illustrates the utility of (31)P and (11)B NMR chemical shifts, (11)B electric field gradient tensors, and (31)P-(11)B indirect and direct dipole-dipole interactions for characterizing intramolecular borane-phosphane FLPs, illustrating the potential of this method to (1) quantify the extent of boron-phosphorus bonding interactions (and hence the "degree of frustration") and (2) reveal specific structural details (i.e., boron-phosphorus distances and other local geometry aspects) relating to the catalytic activities of these exciting materials. PMID:23138688

Wiegand, Thomas; Eckert, Hellmut; Grimme, Stefan

2013-01-01

132

Regenerated silk fibers: Structural studies and solid state NMR techniques for efficient multiple distance determinations in proteins  

NASA Astrophysics Data System (ADS)

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 ?-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 ?-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 ?-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 data. This pulse sequence highlights the similarities between multiple quantum NMR and REDOR. From this connection, we name this new class of experiments Multiple Quantum-REDOR. These experiments should allow for efficient simultaneous multiple distance determinations in proteins.

Liivak, Oskar

2000-09-01

133

Structural Studies of Biomaterials Using Double-Quantum Solid-State NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

Proteins directly control the nucleation and growth of biominerals, but the details of molecular recognition at the protein-biomineral interface remain poorly understood. The elucidation of recognition mechanisms at this interface may provide design principles for advanced materials development in medical and ceramic composites technologies. Here, we describe both the theory and practice of double-quantum solid-state NMR (ssNMR) structure-determination techniques, as they are used to determine the secondary structures of surface-adsorbed peptides and proteins. In particular, we have used ssNMR dipolar techniques to provide the first high-resolution structural and dynamic characterization of a hydrated biomineralization protein, salivary statherin, adsorbed to its biologically relevant hydroxyapatite (HAP) surface. Here, we also review NMR data on peptides designed to adsorb from aqueous solutions onto highly porous hydrophobic surfaces with specific helical secondary structures. The adsorption or covalent attachment of biological macromolecules onto polymer materials to improve their biocompatibility has been pursued using a variety of approaches, but key to understanding their efficacy is the verification of the structure and dynamics of the immobilized biomolecules using double-quantum ssNMR spectroscopy.

Drobny, G. P.; Long, J. R.; Karlsson, T.; Shaw, W.; Popham, J.; Oyler, N.; Bower, P.; Stringer, J.; Gregory, D.; Mehta, M.; Stayton, P. S.

2003-10-01

134

Applicability of solid-state 13C CP\\/MAS NMR analysis in Spodosols: chemical removal of magnetic materials  

Microsoft Academic Search

The presence of magnetic species, Fe in particular, decreases the effectiveness of nuclear magnetic resonance (NMR) analysis of soil organic matter (SOM), especially in Spodosols. This study was conducted to evaluate the utility of dithionite, stannous chloride, and hydrofluoric acid (HF) extraction for Fe removal and solid-state 13C NMR spectral enhancement in forested Spodosols. Extraction with 2% HF resulted in

K'o H Dai; Chris E Johnson

1999-01-01

135

Solid-state 13C NMR spectroscopic studies of soil organic matter at two magnetic field strengths  

Microsoft Academic Search

The characterization of soil organic matter by solid-state 13C NMR spectroscopy is increasingly being carried out on NMR spectrometers with higher magnetic fields, despite reservations about the quantitative reliability of spectra acquired at these high magnetic fields. In this study, the performance of 200 and 400 MHz spectrometers is compared for the quantitative analysis of two soil organic matter samples

Ronald J. Smernik

2005-01-01

136

Improving the quality of 2D solid-state NMR spectra of microcrystalline proteins by covariance analysisw  

E-print Network

Improving the quality of 2D solid-state NMR spectra of microcrystalline proteins by covariance: covariance processing of two-dimensional NMR spectra of microcrystalline proteins improves spectral quality of microcrystalline proteins improves spectral resolution and sensitivity over conventional Fourier transformation

137

Experimental aspects in acquisition of wide bandwidth solid-state MAS NMR spectra of low-? nuclei with different opportunities on two commercial NMR spectrometers.  

PubMed

The acquisition and different appearances observed for wide bandwidth solid-state MAS NMR spectra of low-? nuclei, using (14)N as an illustrative nucleus and employing two different commercial spectrometers (Varian, 14.1T and Bruker, 19.6T), have been compared/evaluated and optimized from an experimental NMR and an electronic engineering point of view, to account for the huge differences in these spectra. The large differences in their spectral appearances, employing the recommended/standard experimental set-up for the two different spectrometers, are shown to be associated with quite large differences in the electronic design of the two types of preamplifiers, which are connected to their respective probes through a 50? cable, and are here completely accounted for. This has led to different opportunities for optimum performances in the acquisition of nearly ideal wide bandwidth spectra for low-? nuclei on the two spectrometers by careful evaluation of the length for the 50? probe-to-preamp cable for the Varian system and appropriate changes to the bandwidth (Q) of the NMR probe used on the Bruker spectrometer. Earlier, we reported quite distorted spectra obtained with Varian Unity INOVA spectrometers (at 11.4 and 14.1T) in several exploratory wide bandwidth (14)N MAS NMR studies of inorganic nitrates and amino acids. These spectra have now been compared/evaluated with fully analyzed (14)N MAS spectra correspondingly acquired at 19.6T on a Bruker spectrometer. It is shown that our upgraded version of the STARS simulation/iterative-fitting software is capable of providing identical sets for the molecular spectral parameters and corresponding fits to the experimental spectra, which fully agree with the electronic measurements, despite the highly different appearances for the MAS NMR spectra acquired on the Varian and Bruker spectrometers. PMID:21704544

Jakobsen, Hans J; Bildsøe, Henrik; Gan, Zhehong; Brey, William W

2011-08-01

138

Chain Packing and Trajectory of Isotactic Polypropylene ? Crystals studied by Solid-State NMR  

NASA Astrophysics Data System (ADS)

Isotactic polypropylene (ipp) is one of the simplest polyolefins and the crystalline structures, have been extensively studied. Ipp crystallizes as ? form via isothermal crystallization from the melt state. Packing structures of ? form has been used as structural markers of crystallization process. With the development of high resolution solid-state NMR (SS-NMR) technique, it becomes a powerful tool to investigate order-disorder of chain packing in the crystalline regions. We performed a series of experiments on different samples crystallized at different temperatures and studied the formation of ? crystals influenced by different parameters, such as molecular weight, catalyst type and stereo, region regularity. Using selectively ^13C enriched ipp samples we detect inter-nuclear correlations between the neighboring stems. This information provides chain reentry information. We figure out relationship between the chain reentry and chain packing of ipp ? crystals. The recent discovery of the ipp ?2 single crystal offers a great opportunity to understand this topic also.

Li, Zhen; Cao, Yan; Miyoshi, Toshikazu; Cheng, Stephen

2012-02-01

139

[sup 29]Si solid state NMR study of tricalcium silicate and cement hydration at high temperature  

SciTech Connect

Oilwell cementing involves the placement of a cement slurry in the annulus between the metal casing and the geological formation. Its principal functions are to isolate the different zones within the wellbore and to support the casing at each stage of drilling. [sup 29]Si high resolution solid state NMR has been used to follow the hydration kinetics of class G Portland cement and of its major component: tricalcium silicate Ca[sub 3]SiO[sub 5] (C[sub 3]S). Samples were hydrothermally synthesized at temperatures between 60 and 120C; hydration was stopped at selected reaction times, from 30 minutes to 14 days, by the acetone-ether method of water-removing. [sup 29]Si NMR spectra of hydrates clearly show that, in silicate chains, the ratio between the silicon atoms of end groups and those of middle groups depends not only on the time of hydration, but also on the synthesis temperature.

Masse, S.; Zanni, H. (URA CNRS, Paris (France). Lab. de Physique et Mecanique des Milieux Heterogenes Univ. Pierre et Marie Curie, Paris (France)); Lecourtier, J.; Roussel, J.C.; Rivereau, A. (Inst. Francais du Petrole, Rueil Malmaison (France))

1993-09-01

140

High Resolution Solid State 2D NMR Analysis of Biomass and Biochar.  

PubMed

Solid state NMR methods are required to analyze biomass as a function of its chemical or biological treatment for biofuels, chemicals, or biochar production. The native polymers network in lignocellulosic biomass and other solid materials, such as coal, coke, or biochar, can hardly be analyzed by liquid state NMR due to their poor swelling ability without chemical modification. A (1)H-(13)C two-dimensional heteronuclear correlation (HETCOR) experiment with frequency-switched Lee-Goldburg (FSLG) irradiation is performed on a high field spectrometer (750 MHz). This method leads to previously unattained resolution for biomass and biochar and offers a unique ability to reveal their chemical composition. The formation of aromatic moieties from carbohydrates and lignin thermal conversion is clearly distinguished. This method can be applied to all other carbonaceous materials. PMID:25521946

Le Brech, Yann; Delmotte, Luc; Raya, Jesus; Brosse, Nicolas; Gadiou, Roger; Dufour, Anthony

2015-01-20

141

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

PubMed

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 ?-sheet secondary structure. Mutational studies of conserved hydrophobic residues located in the identified ?-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 ?-strand segments identified by solid-state NMR, we propose that the DUF583 domain adopts a ?-helical architecture, in which 18 ?-strand segments are arranged in six consecutive windings of a ?-helix. PMID:25550503

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

2015-01-13

142

Solid-state NMR studies of the prion protein H1 fragment.  

PubMed

Conformational changes in the prion protein (PrP) seem to be responsible for prion diseases. We have used conformation-dependent chemical-shift measurements and rotational-resonance distance measurements to analyze the conformation of solid-state peptides lacking long-range order, corresponding to a region of PrP designated H1. This region is predicted to undergo a transformation of secondary structure in generating the infectious form of the protein. Solid-state NMR spectra of specifically 13C-enriched samples of H1, residues 109-122 (MKHMAGAAAAGAVV) of Syrian hamster PrP, have been acquired under cross-polarization and magic-angle spinning conditions. Samples lyophilized from 50% acetonitrile/50% water show chemical shifts characteristic of a beta-sheet conformation in the region corresponding to residues 112-121, whereas samples lyophilized from hexafluoroisopropanol display shifts indicative of alpha-helical secondary structure in the region corresponding to residues 113-117. Complete conversion to the helical conformation was not observed and conversion from alpha-helix back to beta-sheet, as inferred from the solid-state NMR spectra, occurred when samples were exposed to water. Rotational-resonance experiments were performed on seven doubly 13C-labeled H1 samples dried from water. Measured distances suggest that the peptide is in an extended, possibly beta-strand, conformation. These results are consistent with the experimental observation that PrP can exist in different conformational states and with structural predictions based on biological data and theoretical modeling that suggest that H1 may play a key role in the conformational transition involved in the development of prion diseases. PMID:8844854

Heller, J; Kolbert, A C; Larsen, R; Ernst, M; Bekker, T; Baldwin, M; Prusiner, S B; Pines, A; Wemmer, D E

1996-08-01

143

Solid-state NMR studies of the prion protein H1 fragment.  

PubMed Central

Conformational changes in the prion protein (PrP) seem to be responsible for prion diseases. We have used conformation-dependent chemical-shift measurements and rotational-resonance distance measurements to analyze the conformation of solid-state peptides lacking long-range order, corresponding to a region of PrP designated H1. This region is predicted to undergo a transformation of secondary structure in generating the infectious form of the protein. Solid-state NMR spectra of specifically 13C-enriched samples of H1, residues 109-122 (MKHMAGAAAAGAVV) of Syrian hamster PrP, have been acquired under cross-polarization and magic-angle spinning conditions. Samples lyophilized from 50% acetonitrile/50% water show chemical shifts characteristic of a beta-sheet conformation in the region corresponding to residues 112-121, whereas samples lyophilized from hexafluoroisopropanol display shifts indicative of alpha-helical secondary structure in the region corresponding to residues 113-117. Complete conversion to the helical conformation was not observed and conversion from alpha-helix back to beta-sheet, as inferred from the solid-state NMR spectra, occurred when samples were exposed to water. Rotational-resonance experiments were performed on seven doubly 13C-labeled H1 samples dried from water. Measured distances suggest that the peptide is in an extended, possibly beta-strand, conformation. These results are consistent with the experimental observation that PrP can exist in different conformational states and with structural predictions based on biological data and theoretical modeling that suggest that H1 may play a key role in the conformational transition involved in the development of prion diseases. PMID:8844854

Heller, J.; Kolbert, A. C.; Larsen, R.; Ernst, M.; Bekker, T.; Baldwin, M.; Prusiner, S. B.; Pines, A.; Wemmer, D. E.

1996-01-01

144

Proton-detected solid-state NMR spectroscopy at aliphatic sites: application to crystalline systems.  

PubMed

When applied to biomolecules, solid-state NMR suffers from low sensitivity and resolution. The major obstacle to applying proton detection in the solid state is the proton dipolar network, and deuteration can help avoid this problem. In the past, researchers had primarily focused on the investigation of exchangeable protons in these systems. In this Account, we review NMR spectroscopic strategies that allow researchers to observe aliphatic non-exchangeable proton resonances in proteins with high sensitivity and resolution. Our labeling scheme is based on u-[(2)H,(13)C]-glucose and 5-25% H2O (95-75% D2O) in the M9 bacterial growth medium, known as RAP (reduced adjoining protonation). We highlight spectroscopic approaches for obtaining resonance assignments, a prerequisite for any study of structure and dynamics of a protein by NMR spectroscopy. Because of the dilution of the proton spin system in the solid state, solution-state NMR (1)HCC(1)H type strategies cannot easily be transferred to these experiments. Instead, we needed to pursue ((1)H)CC(1)H, CC(1)H, (1)HCC or ((2)H)CC(1)H type experiments. In protonated samples, we obtained distance restraints for structure calculations from samples grown in bacteria in media containing [1,3]-(13)C-glycerol, [2]-(13)C-glycerol, or selectively enriched glucose to dilute the (13)C spin system. In RAP-labeled samples, we obtained a similar dilution effect by randomly introducing protons into an otherwise deuterated matrix. This isotopic labeling scheme allows us to measure the long-range contacts among aliphatic protons, which can then serve as restraints for the three-dimensional structure calculation of a protein. Due to the high gyromagnetic ratio of protons, longer range contacts are more easily accessible for these nuclei than for carbon nuclei in homologous experiments. Finally, the RAP labeling scheme allows access to dynamic parameters, such as longitudinal relaxation times T1, and order parameters S(2) for backbone and side chain carbon resonances. We expect that these measurements will open up new opportunities to obtain a more detailed description of protein backbone and side chain dynamics. PMID:23745638

Asami, Sam; Reif, Bernd

2013-09-17

145

Quantitative solid-state 13C NMR with signal enhancement by multiple cross polarization  

NASA Astrophysics Data System (ADS)

A simple new method is presented that yields quantitative solid-state magic-angle spinning (MAS) 13C NMR spectra of organic materials with good signal-to-noise ratios. It achieves long (>10 ms) cross polarization (CP) from 1H without significant magnetization losses due to relaxation and with a moderate duty cycle of the radio-frequency irradiation, by multiple 1-ms CP periods alternating with 1H spin-lattice relaxation periods that repolarize the protons. The new method incorporates previous techniques that yield less distorted CP/MAS spectra, such as a linear variation (“ramp”) of the radio-frequency field strength, and it overcomes their main limitation, which is T1? relaxation of the spin-locked 1H magnetization. The ramp of the radio-frequency field strength and the asymptotic limit of cross polarization makes the spectral intensity quite insensitive to the exact field strengths used. The new multiCP pulse sequence is a “drop-in” replacement for previous CP methods and produces no additional data-processing burden. Compared to the only reliable quantitative 13C NMR method for unlabeled solids previously available, namely direct-polarization NMR, the measuring time is reduced by more than a factor of 50, enabling higher-throughput quantitative NMR studies. The new multiCP technique is validated with 14-kHz MAS on amino-acid derivatives, plant matter, a highly aromatic humic acid, and carbon materials made by low-temperature pyrolysis.

Johnson, Robert L.; Schmidt-Rohr, Klaus

2014-02-01

146

Molecular structure of crude beeswax studied by solid-state 13C NMR  

PubMed Central

13C Solid-state NMR experiments were performed to investigate the structure of beeswax in the native state (crude beeswax) for the first time. From quantitative direct polarization 13C MAS NMR spectrum, it was found that the fraction of internal-chain methylene (int-(CH2)) component compared to other components of crude beeswax was over 95%. The line shape of the int-(CH2) carbon resonance region was comprehensively analyzed in terms of NMR chemical shift. The 13C broad peak component covering from 31 to 35ppm corresponds to int-(CH2) carbons with trans conformation in crystalline domains, whereas the sharp signal at 30.3 ppm corresponds to gauche conformation in the non-crystalline domain. From peak deconvolution of the aliphatic region, it was found that over 85% of the int-(CH2) has a crystal structure and several kinds of molecular packing for int-(CH2), at least three, exist in the crystalline domain. Abbreviation: NMR nuclear magnetic resonance int-(CH2) internal-chain methylene CP cross-polarization MAS magic angle spinning PMID:15861244

Kameda, Tsunenori

2004-01-01

147

Structural insights into the binding of cardiac glycosides to the digitalis receptor revealed by solid-state NMR  

Microsoft Academic Search

Several biologically active derivatives of the cardiotonic steroid ouabain have been made containing NMR isotopes (13C, 2H, and 19F) in the rhamnose sugar and steroid moieties, and examined at the digitalis receptor site of renal Na+\\/K+-ATPase by a combination of solid-state NMR methods. Deuterium NMR spectra of 2H-labeled inhibitors revealed that the sugar group was only loosely associated with the

David A. Middleton; Saffron Rankin; Mikael Esmann; Anthony Watts

2000-01-01

148

GEOC Martial Taillefert Monday, April 08, 2013 72 Glyphosate sorption mechanism at the boehmite/water interface using solid state 31P NMR and P XANES  

E-print Network

/water interface using solid state 31P NMR and P XANES Wei Li1, weili@udel.edu, Xionghan Feng1,4, Paul Northrup2 examined the sorption mechanism of glyphosate to boehmite, a variablecharge soil mineral, using 31P solid state NMR, P Kedge XANES, and density function theory (DFT). The 31P NMR spectra contain three resolved

Sparks, Donald L.

149

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

PubMed

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. PMID:17487978

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

2007-06-01

150

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

NASA Astrophysics Data System (ADS)

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 results to assist with spectral assignment and the identification of the hydrogen bonding interactions.

Tatton, Andrew S.

151

Structural Characterization of Humic Materials Using ^13C NMR Techniques: A Comparison of Solution- and Solid-State Methods  

NASA Astrophysics Data System (ADS)

The analysis of the carbon type distribution and chemical structure of natural organic matter (NOM) by ^13C NMR spectroscopy is an important technique for understanding its origins and reactivity. While prior work has used solution-state NMR techniques, solid-state NMR has the potential to provide this information using less instrument time and sample manipulation, while providing an array of advanced filtering techniques. Analyses of four isolated humic materials with ^13C solid-state magic angle spinning (MAS) NMR techniques are described, including three commercially available samples and one fulvic acid sample isolated from the Rio Grande in New Mexico. This study demonstrates the utility of solid-state ^13C NMR for aquatic NOM structural characterization, comparing these results to the existing solution-state determinations. The solid-state ^13C MAS NMR results are used to determine % carbon distribution, estimates of elemental composition (%C, %H, %(O+N)), aromatic fraction (fa), nonprotonated aromatic fraction (faN), an estimate of aromatic cluster size, and ratio of sp^2 to sp^3 carbons. A Gaussian deconvolution method is introduced that allows for a detailed analysis of carbon type.

Clewett, Catherine; Alam, Todd; Osantowski, Eric; Pullin, Michael

2011-10-01

152

Structure of molecular tweezer complexes in the solid state: NMR experiments, X-ray investigations, and quantum chemical calculations.  

PubMed

The structure of supramolecular complexes formed by a naphthalene-spaced tweezer molecule as host and 1,4-dicyanobenzene (DCNB), 1,2,4,5-tetracyanobenzene (TCNB), and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) as aromatic, electron-deficient guests is investigated by solid-state NMR and X-ray diffraction measurements. Quantum chemical calculations using linear scaling methods are applied to predict and to assign the 1H NMR chemical shifts of the complexes. By combining experiment and theory, insights into intra- and intermolecular effects influencing the proton chemical shifts of the host-guest system are provided in the solid state. PMID:17263413

Schaller, Torsten; Büchele, Uta P; Klärner, Frank-Gerrit; Bläser, Dieter; Boese, Roland; Brown, Steven P; Spiess, Hans Wolfgang; Koziol, Felix; Kussmann, Jörg; Ochsenfeld, Christian

2007-02-01

153

Study of ion diffusional motion in ionic liquid-based polymer electrolytes by simultaneous solid state NMR and DTA.  

PubMed

Polymer electrolytes containing ionic liquid (IL), 2-methyl-1,3-dipropylimidazolium dihydrogenphosphate (MDPImH2PO4) have been studied by (1)H solid state NMR and differential thermal analysis (DTA) simultaneously by using a specially designed probe. To the best of our knowledge, this is the first report of its kind for IL based polymer electrolytes. The variation of NMR line width with temperature for the IL and polymer electrolytes shows line narrowing at the glass transition and melting temperature. The onset of long-range ion diffusional motion also takes place at these temperatures and is accompanied by a sudden increase in ionic conductivity value by 2-3 orders of magnitude. The presence of amorphous and crystalline phases in IL-based polymer electrolytes has been observed from X-ray diffraction (XRD) studies, and the amorphous phase is the high conducting phase in these polymer electrolytes. The IL-based polymer electrolytes have been observed to be thermally stable up to 200 °C. The results obtained from ion transport studies have also been supported by Fourier transform infrared (FTIR), XRD, and cyclic voltammetry (CV) studies. PMID:23350657

Rajput, Dushyant Singh; Yamada, Koji; Sekhon, S S

2013-02-28

154

Membrane insertion and orientation of polyalanine peptides: a (15)N solid-state NMR spectroscopy investigation.  

PubMed Central

Polyalanine-based peptides were prepared by solid-phase peptide synthesis, labeled with (15)N at selected sites, reconstituted into oriented phosphatidylcholine bilayers, and investigated by proton-decoupled (15)N solid-state NMR spectroscopy. The anisotropic (15)N chemical shift is a direct indicator of helix alignment with respect to the membrane normal. The in-plane to transmembrane equilibrium is the focus of this study. Time- and solvent-dependent transmembrane alignments of K(3)A(18)K(3) have been obtained, and these are stabilized when a few alanine residues are replaced with leucine. The results are discussed in the context of a model where polyalanines adopt a variety of configurations, which are interconnected by multiple equilibria. The data indicate hydrophobicity values of alanine close to zero when studied in the context of helical polypeptides (> or =24 residues) and phospholipid bilayers. PMID:11566795

Bechinger, B

2001-01-01

155

Study of Multiple Rounds of Error Correction in Solid State NMR QIP  

E-print Network

Methods to control errors will be essential for quantum information processing. It is widely believed that fault-tolerant quantum error correction is the leading contender to achieve this goal. Although the theory of fault-tolerant quantum error correction is very well understood, experimental implementation has been lagging. We study the feasibility of implementing repeated rounds of quantum error correction with refreshed ancillas in solid state nuclear magnetic resonance (NMR). In particular we study the procedure proposed for extracting entropy that consists of two stages; an error correcting code optimized to function at finite temperature, and an implementation of heat-bath algorithmic cooling to refresh the ancilla qubits. Two algorithms are presented which implement this method, one for performing tests on 4 qubits, the other for practical implementation on 6 qubits. The effects of imperfect implementation are examined in both the error correction and refreshing stages.

Ben Criger; Osama Moussa; Raymond Laflamme

2011-03-22

156

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

SciTech Connect

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

Tsai, Yi-Ling [Department of Chemistry, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan ROC (China); Hanna, John V. [Department of Physics, The University of Warwick, Coventry CV4 7AL (United Kingdom); Lee, Yuan-Ling, E-mail: yuanlinglee@ntu.edu.t [Graduate Institute of Clinical Dentistry, National Taiwan University and Hospital, No. 1, Changde Street, Taipei 10048, Taiwan ROC (China); Smith, Mark E., E-mail: M.E.Smith.1@warwick.ac.u [Department of Physics, The University of Warwick, Coventry CV4 7AL (United Kingdom); Chan, Jerry C.C., E-mail: chanjcc@ntu.edu.t [Department of Chemistry, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan ROC (China)

2010-12-15

157

Covariance Spectroscopy in High-Resolution Multi-dimensional Solid-state NMR  

PubMed Central

Covariance spectroscopy (COV), a statistical method that provides increased sensitivity, can be applied to two-dimensional high-resolution solid-state NMR experiments, such as homonuclear spin-exchange spectroscopy. We proposed the alternative States sampling scheme to the experimental time by 50%. By combining COV with other processing methods for non-uniform sampling (NUS), many different three-dimensional experiments can be performed with substantial increases in overall sensitivity. As an example, we show a three-dimensional homonuclear spin-exchange / separated-local-field (SLF) spectrum that enables the assignment of resonances and the measurement of structural restraints from a single experiment performed in a limited amount of time. PMID:24380813

Lin, Eugene C.; Opella, Stanley J.

2014-01-01

158

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

159

An Amyloid Organelle, Solid-state NMR Evidence for Cross-? Assembly of Gas Vesicles*  

PubMed Central

Functional amyloids have been identified in a wide range of organisms, taking on a variety of biological roles and being controlled by remarkable mechanisms of directed assembly. Here, we report that amyloid fibrils constitute the ribs of the buoyancy organelles of Anabaena flos-aquae. The walls of these gas-filled vesicles are known to comprise a single protein, GvpA, arranged in a low pitch helix. However, the tertiary and quaternary structures have been elusive. Using solid-state NMR correlation spectroscopy we find detailed evidence for an extended cross-? structure. This amyloid assembly helps to account for the strength and amphiphilic properties of the vesicle wall. Buoyancy organelles thus dramatically extend the scope of known functional amyloids. PMID:22147705

Bayro, Marvin J.; Daviso, Eugenio; Belenky, Marina; Griffin, Robert G.; Herzfeld, Judith

2012-01-01

160

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

PubMed Central

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

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

2013-01-01

161

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

NASA Astrophysics Data System (ADS)

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.

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

2000-12-01

162

Conformational Disorder of Membrane Peptides Investigated from Solid-State NMR Linewidths and Lineshapes  

PubMed Central

A challenge in the application of solid-state NMR spectroscopy to membrane peptides and proteins is the relatively broad linewidths compared to solution NMR spectra. To understand the linewidth contributions to membrane protein NMR spectra, we have measured the inhomogeneous and homogeneous linewidths of several well-studied membrane peptides under immobilized conditions. 13C T2 relaxation times of uniformly 13C-labeled residues show that the homogeneous linewidths of the peptides are comparable to those of crystalline model compounds under identical 1H decoupling and magic-angle-spinning conditions, indicating that the homogeneous linewidths are determined by conformation-independent factors, including residual dipolar coupling, J coupling and intrinsic T2 relaxation. However, the membrane peptides exhibit larger apparent linewidths than the crystalline compounds, indicating conformational disorder. A cationic cell-penetrating peptide, the human immunodeficiency virus TAT, exhibits the largest apparent linewidths, which are about 5-fold larger than the homogeneous linewidths, while the transmembrane helix of the influenza M2 peptide and the ?-hairpin antimicrobial peptide PG-1 show moderately larger apparent linewidths than the crystalline compounds. These results are consistent with the random coil nature of the TAT peptide, which contrasts with the intramolecularly hydrogen-bonded M2 and PG-1. Cross peak lineshapes of 2D double-quantum correlation spectra show that the conformational disorder can occur at the residue level and can result from three origins: lipid-peptide interaction, intrinsic conformational disorder encoded in the amino acid sequence, and sidechain rotameric averaging. A particularly important lipid-peptide interaction for cationic membrane peptides is guanidinium-phosphate ion pair interaction. Thus, NMR linewidths and lineshapes are useful for understanding the conformational disorder of membrane peptides and proteins. PMID:21806038

Su, Yongchao; Hong, Mei

2011-01-01

163

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

164

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

PubMed

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. PMID:22801707

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

2012-09-01

165

“CLASSIC NMR”: An In-Situ NMR Strategy for Mapping the Time-Evolution of Crystallization Processes by Combined Liquid-State and Solid-State Measurements**  

PubMed Central

A new in-situ NMR strategy (termed CLASSIC NMR) for mapping the evolution of crystallization processes is reported, involving simultaneous measurement of both liquid-state and solid-state NMR spectra as a function of time. This combined strategy allows complementary information to be obtained on the evolution of both the solid and liquid phases during the crystallization process. In particular, as crystallization proceeds (monitored by solid-state NMR), the solution state becomes more dilute, leading to changes in solution-state speciation and the modes of molecular aggregation in solution, which are monitored by liquid-state NMR. The CLASSIC NMR experiment is applied here to yield new insights into the crystallization of m-aminobenzoic acid. PMID:25044662

Hughes, Colan E; Williams, P Andrew; Harris, Kenneth D M

2014-01-01

166

Variable-temperature solid-state NMR studies of iron(II) and iron(III) complexes  

E-print Network

of nondia- magnetic solid materials using variable-temperature C cross-polarization/magic-angle spinning NMR spectroscopy. Solid Fe(II)/Zn(11) solutions (alloys) are used to simulate various high-spin/low-spin compositions of the spin crossover complex... coupled system, (OEPFe)20, in the solid state. Comparisons to a similar solution-state NMR study of the same complex provide evidence for significant structural differences in the two phases. DEDICATION This thesis is dedicated to my wonderful husband...

Shepard, Patricia Arlene

2012-06-07

167

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

PubMed

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%. PMID:17920878

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

2008-07-01

168

Solid-state NMR analyses reveal the structure dependence of the molecular dynamics for ?-amino acids.  

PubMed

The molecular dynamics of metabolites is structure dependent and vitally important for the interactive functions in their potential applications as natural materials. To understand the relationship between molecular structure and dynamics, the molecular motions of four structurally related ?-amino acids (?-alanine, ?-aminobutyric acid, 5-aminovaleric acid, and 6-aminocaproic acid) were investigated by measuring their proton spin-lattice relaxation times (T(1), T(1?)) as a function of temperature (180-440 K). (13)C CPMAS NMR and DSC analyses were performed to obtain complementary information. All of these ?-amino acids showed no phase transition in the temperature range studied but had outstandingly long proton T(1) at 300 MHz and even at 20 MHz for the deuterated forms. The molecular dynamics of all these ?-amino acids were dominated by the reorientation motions of amino groups and backbone motions except in ?-alanine. The activation energies for amino group reorientations were positively correlated with the strength of hydrogen bonds involving these groups in the crystals and the carbon-chain lengths, whereas such energies for the backbone motions were inversely correlated with the carbon-chain lengths. These findings provided essential information for the molecular dynamics of ?-amino acids and demonstrated the combined solid-state NMR methods as a useful approach for understanding the structural dependence of molecular dynamics. PMID:22251439

Huang, Jing; Zhang, Limin; Tang, Huiru

2012-02-23

169

Optimizing Oriented Planar-Supported Lipid Samples for Solid-State Protein NMR  

PubMed Central

Sample orientation relative to the static magnetic field of an NMR spectrometer allows study of membrane proteins in the lipid bilayer setting. The straightforward preparation and handling of extremely thin mica substrates with consistent surface properties has prompted us to examine oriented phospholipid bilayer and hexagonal phases on mica. The spectral characteristics of oriented lipid samples formed on mica are as good as or better than those on glass. Nine solvents with varying dielectric constants were used to cast lipid films or for vesicle spreading; film characteristics were then compared, and static solid-state 31P-NMR was used to characterize the degree of orientation of the hydrated lipid species. Lipids with four headgroup chemistries were tested: 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG), 1,2-dioleoyl-sn-glycero-3-phosphate (DOPA), and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE). Solvent affected orientation of POPG, DOPA, and DOPE, but not POPC. Film characteristics varied with solvent, with ramifications for producing homogeneous oriented lipid samples. POPC was used to optimize the amount of lipid per substrate and compare hydration methods. POPG did not orient reproducibly, whereas POPG-POPC mixtures did. DOPA showed 1–2 oriented states depending upon hydration level and deposition method. DOPE formed an oriented hexagonal phase that underwent a reversible temperature-induced phase transition to the oriented bilayer phase. PMID:16085766

Rainey, Jan K.; Sykes, Brian D.

2005-01-01

170

Natural abundance high field (43)Ca solid state NMR in cement science.  

PubMed

This work is a systematic attempt to determine the possibilities and the limitations of the (43)Ca high field solid state NMR in the study of cement-based materials. The low natural abundance (0.135%) and small gyromagnetic ratio of (43)Ca present a serious challenge even in a high magnetic field. The NMR spectra of a number of cement compounds of known structure and composition are examined. The spectra of several phases important in cement science, e.g., anhydrous beta di-calcium silicate (beta-C(2)S) and tri-calcium (C(3)S) silicate were obtained for the first time and the relation of spectroscopic and structural parameters is discussed. The method was also applied to the hydrated C(3)S and synthetic calcium silicate hydrates (C-S-H) of different composition in order to understand the state of calcium and transformations in the structure during hydrolysis. The spectra of hydrated C(3)S reveals a calcium environment similar to that of the C-S-H samples and 11 A Tobermorite. These observations support the validity of using layered crystalline C-S-H systems as structural models for the C-S-H that forms in the hydration of Portland cement. PMID:20463996

Moudrakovski, Igor L; Alizadeh, Rouhollah; Beaudoin, James J

2010-07-14

171

Tetraphosphine Linker Scaffolds with a Tetraphenyltin Core for Superior Immobilized Catalysts: A Solid-State NMR Study  

E-print Network

the mechanism of the phosphonium formation in more detail by utilizing solid-state NMR spectroscopy. It has also been a point of interest to study the linkers and catalysts under realistic conditions, in the presence of solvents. Therefore, HRMAS (high...

Perera, Melanie Ingrid

2012-10-19

172

The structure, dynamics and orientation of antimicrobial peptides in membranes by multidimensional solid-state NMR spectroscopy  

Microsoft Academic Search

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 ?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

Burkhard Bechinger

1999-01-01

173

Solid-State NMR Investigation of the Selective Perturbation of Lipid Bilayers by the Cyclic Antimicrobial Peptide RTD-1  

E-print Network

Antimicrobial Peptide RTD-1 Jarrod J. Buffy, Melissa J. McCormick, Sungsool Wi, Alan Waring,§ Robert I. Lehrer antimicrobial peptide isolated from rhesus macaque leukocytes. Using 31P, 2H, 13C, and 15N solid-state NMR, we-1 differ significantly from those of PG-1, a related -hairpin antimicrobial peptide. A number

Hong, Mei

174

High-Temperature Steam-Treatment of PBI, PEKK, and a PEKK-PBI Blend: A Solid-State NMR and IR Spectroscopic Study  

E-print Network

High-Temperature Steam-Treatment of PBI, PEKK, and a PEKK-PBI Blend: A Solid-State NMR and IR-treated at 149 C (300 F) and 316 C (600 F). IR and solid- state NMR spectroscopy are used to study chemical angle spinning (CP/MAS) upon steam-treatment are reversible, and not of a chemical nature, indicating

Bluemel, Janet

175

A spectrometer designed for 6.7 and 14.1 T DNP-enhanced solid-state MAS NMR using quasi-optical microwave transmission  

E-print Network

A spectrometer designed for 6.7 and 14.1 T DNP-enhanced solid-state MAS NMR using quasi t A Dynamic Nuclear Polarisation (DNP) enhanced solid-state Magic Angle Spinning (MAS) NMR spectrom- eter of Physics, University of Warwick, CV4 7AL, United Kingdom b School of Physics and Astronomy, University

Watts, Anthony

176

antimicrobial peptide in lipid bilayers from solid-state NMR Membrane-dependent oligomeric structure and pore formation of a {beta}-hairpin  

E-print Network

antimicrobial peptide in lipid bilayers from solid-state NMR Membrane-dependent oligomeric antimicrobial peptide in lipid bilayers from solid-state NMR Rajeswari Mani*, Sarah D. Cady*, Ming Tang*, Alan J and insertion of protegrin-1 (PG-1), a -hairpin antimicrobial peptide, in lipid bilayers that mimic either

Hong, Mei

177

Variable-temperature 13C solid-state NMR study of the molecular structure of honeybee wax and silk.  

PubMed

To elucidate the native-state crystal structure of beeswax from the Japanese bee, Apis cerana japonica, we determined the relationship between temperature and the 13C solid-state nuclear magnetic resonance (NMR) chemical shift of methylene carbon of beeswax, with comparison to n-alkanes and polyethylene in the orthorhombic, monoclinic, or triclinic crystal form. Variable-temperature 13C solid-state NMR observations of n-alkanes and polyethylene revealed that the chemical shifts of methylene carbon in the orthorhombic crystal form increased linearly with increasing temperature, that of the triclinic form decreased, and that of the monoclinic form was unaltered. These relations were compared with results of variable-temperature 13C solid-state NMR observation of beeswax. Results clarified that the two crystal forms comprising the beeswax in the native state are orthorhombic and monoclinic. The variable-temperature 13C solid-state NMR observations were also applied to interpret the differential scanning calorimetry (DSC) curve of beeswax. They were used to clarify the structural changes of beeswax for widely various temperatures. For beeswax secreted by the Japanese bee, the transition from the orthorhombic form to the rotator phase occurred at 36 degrees C, that is from the crystalline to the intermediate state at 45 degrees C. Moreover, the variable-temperature 13C solid-state NMR spectrum of honeybee silk in the native state was observed. Results demonstrated that the secondary structures of honeybee silk proteins in the native state comprised coexisting alpha-helix and beta-sheet conformations and that the amount of alpha-helices was greater. The alpha-helix content of honeybee silk was compared with that of hornet silk produced by Vespa larvae. PMID:19007807

Kameda, Tsunenori; Tamada, Yasushi

2009-01-01

178

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

NASA Astrophysics Data System (ADS)

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 (?), such as protons, to the less abundant 13C nuclei with low ? 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. The Hartmann-Hahn condition can be expressed as ?HB1H = ?CB1C, where ?H and ?C are the gyromagnetic ratios of protons and carbons, whereas B1H and B1C are the 1H and 13C radio-frequency (r.f.) fields applied to the nuclei. The Hartmann-Hahn condition is affected by the H-C dipolar interaction strength (Stejskal & Memory, 1994). All the factors affecting dipolar interactions may mismatch the Hartmann-Hahn condition and prevent a quantitative representation of the NOM chemical composition (Conte et al., 2004). It has been reported that under low speed MAS conditions, broad matching profiles are centered around the Hartmann-Hahn condition....... With increasing spinning speed the Hartmann-Hahn matching profiles break down in a series of narrow matching bands separated by the rotor frequency (Stejskal & Memory, 1994). In order to account for the instability of the Hartmann-Hahn condition at higher rotor spin rates (>10 kHz), variable amplitude cross-polarization techniques (RAMP-CP) have been developed (Metz et al., 1996). So far, to our knowledge, the prevailing way used to obtain quantitative 13C-CPMAS NMR results was to optimize the 1H and 13C spin lock r.f. fields on simple standard systems such as glycine and to use those r.f. field values to run experiments on unknown organic samples. The aim of the present study was to experimentally evidence that the stability of the Hartmann-Hahn condition was different for different samples with a known structure. Moreover, Hartmann-Hahn profiles of four different humic acids (HAs) were also provided in order to show that the 1H/13C r.f. spin lock field strength must also be tested on the HAs prior to a quantitative evaluation of their 13C-CPMAS NMR spectra. Baldock, J.A., Oades, J.M., Nelson, P.N., Skene, T.M., Golchin, A. & Clarke, P., 1997. Assessing the extent of decomposition of natural organic materials using solid-state C-13 NMR spectroscopy. Australian Journal of Soil Research, 35, 1061-1083. Conte, P., Piccolo, A., van Lagen, B., Buurman, P. & de Jager, P.A., 1997. Quantitative Aspects of So

Berns, Anne E.; Conte, Pellegrino

2010-05-01

179

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

NASA Astrophysics Data System (ADS)

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 layered niobates and their chemical or physical properties, and provide insights into further modifications and improvements. The primary objectives of this work are summarized below: I. Synthesis of series of layered niobates (ALaNb2O7 , A = Cs, Rb, K; KNb3O8; K4Nb 6O17; RbLa2NbTi2O10 and RbCaLaNb2TiO10) by microwave heating or cation exchange methods, their protonated forms by acid exchange (HLaNb2O 7, H3ONb3O8 and HNb3O 8, H4Nb8O17, HLa2NbTi 2O10 and HCaLaNb2TiO10), and three nanosheet niobates by exfoliation (HNb3O8, H4Nb 6O17 and HLaNb2O7 nanosheets). II. Structural characterizations of all niobates by powder XRD and solid-state NMR spectroscopy. Powder XRD is used to determine lattice constants and long-range structural ordering. Solid-state NMR is used to determine the electric field gradient parameters, chemical shift anisotropy parameters and dipolar coupling constants. Solid-state NMR techniques include 93Nb MQMAS, wide-line VOCS echo and WURST-echo; 1H{93Nb} CP, TRAPDOR, S-RESPDOR and iS-RESPDOR experiments. III. Understanding the trends of changes in NMR parameters with respect to cation exchange, exfoliation and compositional alteration, and correlation of the NMR parameters with local environments and possible structural rearrangements. IV. Identification of proton locations in the acid-exchanged niobates and surface acidity for the exfoliated nanosheets, based on 1H chemical shifts and dipolar coupling information from CP, S-RESPDOR and iS-RESPDOR experiments.

Liu, Ting

180

Interactions of fullerenes and calixarenes in the solid state studied with [sup 13]C CP-MAS NMR  

SciTech Connect

We report our findings on the interactions of fullerenes with calixarenes, forming a solid-state complex between C[sub 60] and 4-tert-butylcalix[8]arene, and solid state NMR of this complex. Complexation of C[sub 60] with calix[8]arene can occur in CS[sub 2] and in benzene solution, leading to the formation of a solid-state complex. The experiments indicate a 1:1 stoichiometry for the complex. C[sub 70] does not form similar complexes with calix[8]arenes, leading to the possibility of transferring C[sub 60] to the solid phase, separating it from C[sub 70] remaining in solution. The solid-state complexation in benzene, leading to precipitation, provides strong evidence for establishment of an interaction between C[sub 60] and 1. A change of the conformation of the calixarene upon complexation is indicated by the OH shift in the IR and the solid-state CP-MAS NMR data. 17 refs., 2 figs.

Williams, R.M.; Zwier, J.M.; Verhoeven, J.W. (Univ. of Amsterdam (Netherlands)); Nachtegaal, G.H.; Kentgens, A.P.M. (Univ. of Nijmegen (Netherlands))

1994-07-27

181

Elucidating Metabolic Pathways for Amino Acid Incorporation Into Dragline Spider Silk using 13C Enrichment and Solid State NMR  

PubMed Central

Spider silk has been evolutionarily optimized for contextual mechanical performance over the last 400 million years. Despite precisely balanced mechanical properties, which have yet to be reproduced, the underlying molecular architecture of major ampullate spider silk can be simplified being viewed as a versatile block copolymer. Four primary amino acid motifs: polyalanine, (GA)n, GPGXX, and GGX (X = G,A,S,Q,L,Y) will be considered in this study. Although synthetic mimetics of many of these amino acid motifs have been produced in several biological systems, the source of spider silk’s mechanical integrity remains elusive. Mechanical robustness may be a product not only of the amino acid structure but also of the tertiary structure of the silk. Historically, solid state Nuclear Magnetic Resonance (ssNMR) has been used to reveal the crystalline structure of the polyalanine motif; however, limitations in amino acid labeling techniques have obscured the structures of the GGX and GPGXX motifs thought to be responsible for the structural mobility of spider silk. We describe the use of metabolic pathways to label tyrosine for the first time as well as to improve the labeling efficiency of proline. These improved labeling techniques will allow the previously unknown tertiary structures of major ampullate silk to be probed. PMID:21334448

Creager, Melinda S.; Izdebski, Thomas; Brooks, Amanda E.; Lewis, Randolph V.

2013-01-01

182

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

PubMed

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 chain trajectory and molecular dynamics for the lamellar thickening process are discussed. PMID:19891458

Miyoshi, Toshikazu; Mamun, Al; Hu, Wei

2010-01-14

183

High-Resolution NMR of Quadrupolar Nuclei in the Solid State  

SciTech Connect

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 {pi}-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{sup o} (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 (VEFCI?), is presented, along with experimental work on adamantane and polycarbonate.

Gann, Sheryl Lee

1995-11-30

184

Melittin-induced changes in lipid multilayers. A solid-state NMR study.  

PubMed Central

Solid-state 1H, 13C, 14N, and 31P NMR spectroscopy was used to study the effects of the bee venom peptide, melittin, on aligned multilayers of dimyristoyl-, dilauryl- and ditetradecyl-phosphatidylcholines above the gel to liquid-crystalline transition temperature, Tc. Both 31P spectra from the lipid headgroups and 1H resonances from the lipid acyl chain methylene groups indicate that the peptide does not affect the mosaic spread of the lipid molecules at lipid:peptide molar ratios of 10:1, or higher. None of the samples prepared above Tc showed any evidence of the formation of hexagonal or isotropic phases. Melittin-induced changes in the chemical shift anisotropy of the headgroup phosphate and the lipid carbonyl groups, and in the choline 14N quadrupole splittings, show that the peptide has effects on the headgroup order and on the molecular organization in the sections of the acyl chains nearest to the bilayer surface. The spin-lattice relaxation time for the lipid acyl chain methylene protons was found to increase and the rotating-frame longitudinal relaxation time to markedly decrease with the addition of melittin, suggesting that motions on the nanosecond time scale are restricted, whereas the slower, collective motions are enhanced in the presence of the peptide. PMID:1420892

Smith, R; Separovic, F; Bennett, F C; Cornell, B A

1992-01-01

185

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

PubMed

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. PMID:24451254

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

2013-01-01

186

Solid-state NMR analysis of a boron-containing pharmaceutical hydrochloride salt.  

PubMed

A novel crystalline form of the boron-containing antibacterial drug (S)-3-(aminomethyl)-7-(3-hydroxypropoxy)benzo[c] [1,2]oxaborol-1(3H)-ol hydrochloride is studied by solid-state nuclear magnetic resonance (SSNMR) and single-crystal X-ray diffraction techniques. After determination of the crystal structure by X-ray diffraction, SSNMR spectroscopy of this form is performed to obtain structural information using experimental approaches based on dipolar correlation, chemical shift analysis, and quadrupolar interaction analysis. 1H SSNMR experiments at 16.4 T using magic-angle spinning (MAS) and homonuclear dipolar decoupling, 2D SSNMR experiments based on (1)H–(13)C and (1)H–(11)B dipolar heteronuclear correlation, and density functional theory (DFT) calculations are combined in a novel approach to obtain a nearly complete assignment of the (1)H spectrum of this crystalline phase. (11)B and (35)Cl chemical shift and quadrupolar parameters are obtained using the analysis of MAS spectra and are found to be accurately reproduced using DFT calculations. NMR chemical shielding and electric field gradient parameters obtained using these methods are related to hydrogen-bonding trends in the crystal structure. The results illustrate the increasing capability of SSNMR techniques involving (1)H, (11)B, and (35)Cl SSNMR in the analysis of the crystal structure of a pharmaceutical compound containing covalently bonded boron. PMID:23918278

Vogt, Frederick G; Williams, Glenn R; Copley, Royston C B

2013-10-01

187

Solid-state NMR and EPR study of fluorinated carbon nanofibers  

SciTech Connect

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.

Zhang Wei [Laboratoire des Materiaux Inorganiques, UMR CNRS 6002-Clermont Universite, 24 av. des Landais, 63177 Aubiere Cedex (France)], E-mail: wei.zhang@univ-bpclermont.fr; Dubois, Marc [Laboratoire des Materiaux Inorganiques, UMR CNRS 6002-Clermont Universite, 24 av. des Landais, 63177 Aubiere Cedex (France)], E-mail: marc.dubois@univ-bpclermont.fr; Guerin, Katia [Laboratoire des Materiaux Inorganiques, UMR CNRS 6002-Clermont Universite, 24 av. des Landais, 63177 Aubiere Cedex (France)], E-mail: katia.guerin@univ-bpclermont.fr; Hamwi, Andre [Laboratoire des Materiaux Inorganiques, UMR CNRS 6002-Clermont Universite, 24 av. des Landais, 63177 Aubiere Cedex (France)], E-mail: andre.hamwi@univ-bpclermont.fr; Giraudet, Jerome [Matiere Condensee et Resonance Magnetique, Universite Libre de Bruxelles (U. L. B.), CP 232, Boulevard du Triomphe, B-1050 Bruxelles (Belgium)], E-mail: jerome.giraudet@ulb.ac.be; Masin, Francis [Matiere Condensee et Resonance Magnetique, Universite Libre de Bruxelles (U. L. B.), CP 232, Boulevard du Triomphe, B-1050 Bruxelles (Belgium)], E-mail: fmasin@ulb.ac.be

2008-08-15

188

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

PubMed Central

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 ?- and ?-forms of CuPc, the most widely used polymorphs, by solid-state NMR (SSNMR) and Raman spectroscopy. 13C high-resolution SSNMR spectra of ?- and ?-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 ?- and ?-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

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

2010-01-01

189

High field (33)S solid state NMR and first-principles calculations in potassium sulfates.  

PubMed

A set of potassium sulfates presenting a variety of sulfur environments (K(2)SO(4), KHSO(4), K(2)S(2)O(7), and K(2)S(2)O(8)) has been studied by (33)S solid state NMR at 21 T. Low natural abundance (0.75%) and small gyromagnetic ratio of (33)S presented a serious challenge even at such a high magnetic field. Nevertheless, using the QCPMG technique we were able to obtain good signals from the sites with C(Q) values approaching 16 MHz. Assignment of the sites and the relative orientations of the EFG tensors were assisted by quantum mechanical calculations using the Gaussian 98 and CASTEP packages. The Gaussian 98 calculations were performed using the density functional method and gauge independent atomic orbitals on molecular clusters of about 100-120 atoms. The CASTEP calculations utilized periodic boundary conditions and a gauge-including projector augmented-wave pseudopotential approach. Although only semiquantitative agreement is observed between the experimental and calculated parameters, the calculations are a very useful aid in the interpretation of experimental data. PMID:20055518

Moudrakovski, Igor; Lang, Stephen; Patchkovskii, Serguei; Ripmeester, John

2010-01-14

190

Membrane interactions of phylloseptin-1, -2, and -3 peptides by oriented solid-state NMR spectroscopy.  

PubMed

Phylloseptin-1, -2, and -3 are three members of the family of linear cationic antimicrobial peptides found in tree frogs. The highly homologous peptides encompass 19 amino acids, and only differ in the amino acid composition and charge at the six most carboxy-terminal residues. Here, we investigated how such subtle changes are reflected in their membrane interactions and how these can be correlated to their biological activities. To this end, the three peptides were labeled with stable isotopes, reconstituted into oriented phospholipid bilayers, and their detailed topology determined by a combined approach using (2)H and (15)N solid-state NMR spectroscopy. Although phylloseptin-2 and -3 adopt perfect in-plane alignments, the tilt angle of phylloseptin-1 deviates by 8° probably to assure a more water exposed localization of the lysine-17 side chain. Furthermore, different azimuthal angles are observed, positioning the amphipathic helices of all three peptides with the charged residues well exposed to the water phase. Interestingly, our studies also reveal that two orientation-dependent (2)H quadrupolar splittings from methyl-deuterated alanines and one (15)N amide chemical shift are sufficient to unambiguously determine the topology of phylloseptin-1, where quadrupolar splittings close to the maximum impose the most stringent angular restraints. As a result of these studies, a strategy is proposed where the topology of a peptide structure can be determined accurately from the labeling with (15)N and (2)H isotopes of only a few amino acid residues. PMID:25140425

Resende, Jarbas M; Verly, Rodrigo M; Aisenbrey, Christopher; Cesar, Amary; Bertani, Philippe; Piló-Veloso, Dorila; Bechinger, Burkhard

2014-08-19

191

Structural constraints for the Crh protein from solid-state NMR experiments  

PubMed Central

We demonstrate that short, medium and long-range constraints can be extracted from proton mediated, rare-spin detected correlation solid-state NMR experiments for the microcrystalline 10.4 × 2 kDa dimeric model protein Crh. Magnetization build-up curves from cross signals in NHHC and CHHC spectra deliver detailed information on side chain conformers and secondary structure for interactions between spin pairs. A large number of medium and long-range correlations can be observed in the spectra, and an analysis of the resolved signals reveals that the constraints cover the entire sequence, also including inter-monomer contacts between the two molecules forming the domain-swapped Crh dimer. Dynamic behavior is shown to have an impact on cross signals intensities, as indicated for mobile residues or regions by contacts predicted from the crystal structure, but absent in the spectra. Our work validates strategies involving proton distance measurements for large and complex proteins as the Crh dimer, and confirms the magnetization transfer properties previously described for small molecules in solid protein samples. Electronic supplementary material The online version of this article (doi:10.1007/s10858-008-9229-3) contains supplementary material, which is available to authorized users. PMID:18320329

Gardiennet, Carole; Loquet, Antoine; Etzkorn, Manuel; Heise, Henrike; Baldus, Marc

2008-01-01

192

Fine refinement of solid state structure of racemic form of phospho-tyrosine employing NMR Crystallography approach.  

PubMed

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. PMID:25240460

Paluch, Piotr; Pawlak, Tomasz; Oszajca, Marcin; Lasocha, Wieslaw; Potrzebowski, Marek J

2014-09-01

193

New insights into the bonding arrangements of L- and D-glutamates from solid state 17O NMR  

NASA Astrophysics Data System (ADS)

Magic angle spinning (MAS) from L- and D-glutamic acid-HCl at 14.1 T produces highly structured and very similar NMR spectra. Lines from all 4 oxygen sites are readily distinguished and assigned. These 17O NMR spectra are very different from the previously reported 17O spectrum of the D, L-form presumably because that was a racemic crystal. 17O NMR from L-monosodium glutamate-HCl is very different again requiring the application of double angle rotation and 3 quantum MAS NMR to provide resolution of 5 different sites. Hence high resolution 17O solid state NMR techniques offer possible new insight into biochemical bonding processes.

Lemaitre, V.; Pike, K. J.; Watts, A.; Anupold, T.; Samoson, A.; Smith, M. E.; Dupree, R.

2003-03-01

194

Solid-state NMR/NQR and first-principles study of two niobium halide cluster compounds.  

PubMed

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 ?iso((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 ?33) 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 (?11) 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. PMID:24581866

Peri?, Berislav; Gautier, Régis; Pickard, Chris J; Bosio?i?, Marko; Grbi?, Mihael S; Požek, Miroslav

2014-01-01

195

High resolution NMR as a local probe of structure, conformation, and mobility in solid polymers  

NASA Astrophysics Data System (ADS)

Because the NMR frequency of a dipolar nucleus is exquisitely sensitive to the structural and conformational natures of its immediate environment, high resolution NMR can be utilized to probe the structures, conformations, and motions (via resonance relaxation) of the constituent molecules belonging to solid samples. By means of a single polymer example (polypropylene) we attempt to illustrate how structural, conformational, and motional information about solid polymers can be obtained by employing high resolution, solid state NMR.

Tonelli, Alan E.

1995-08-01

196

Solid-state 13C NMR and molecular modeling studies of acetyl aleuritolic acid obtained from Croton cajucara Benth  

NASA Astrophysics Data System (ADS)

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.

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

197

Efficient design of multituned transmission line NMR probes: the electrical engineering approach.  

PubMed

Transmission line-based multi-channel solid state NMR probes have many advantages regarding the cost of construction, number of RF-channels, and achievable RF-power levels. Nevertheless, these probes are only rarely employed in solid state-NMR-labs, mainly owing to the difficult experimental determination of the necessary RF-parameters. Here, the efficient design of multi-channel solid state MAS-NMR probes employing transmission line theory and modern techniques of electrical engineering is presented. As technical realization a five-channel ((1)H, (31)P, (13)C, (2)H and (15)N) probe for operation at 7 Tesla is described. This very cost efficient design goal is a multi port single coil transmission line probe based on the design developed by Schaefer and McKay. The electrical performance of the probe is determined by measuring of Scattering matrix parameters (S-parameters) in particular input/output ports. These parameters are compared to the calculated parameters of the design employing the S-matrix formalism. It is shown that the S-matrix formalism provides an excellent tool for examination of transmission line probes and thus the tool for a rational design of these probes. On the other hand, the resulting design provides excellent electrical performance. From a point of view of Nuclear Magnetic Resonance (NMR), calibration spectra of particular ports (channels) are of great importance. The estimation of the ?/2 pulses length for all five NMR channels is presented. PMID:21316931

Frydel, J A; Krzystyniak, M; Pienkowski, D; Pietrzak, M; de Sousa Amadeu, N; Ratajczyk, T; Idzik, K; Gutmann, T; Tietze, D; Voigt, S; Fenn, A; Limbach, H H; Buntkowsky, G

2011-01-01

198

The heterogeneous nature of microbial products as shown by solid-state 13 C CP\\/MAS NMR spectroscopy  

Microsoft Academic Search

Homoionic Na-, Ca-, and Al-clays were prepared from the 13C-labelled (99.9% atom) glucose were incorporated into the artificial soils to study the effects of clay types, exchangeable cations and clay contents on the mineralization of glucose-carbon and glucose-derived organic materials. Chemical transformation of glucose-carbon upon incorporation into microbial products and metabolites, was followed using solid-state13C CP\\/MAS NMR spectroscopy.

A. Golchin; P. Clarke; J. M. Oades

1996-01-01

199

Cellulose crystallinity and ordering of hemicelluloses in pine and birch pulps as revealed by solid-state NMR spectroscopic methods  

Microsoft Academic Search

Solid-state 13C NMR spectroscopy was used to determine the degree of cellulose crystallinity (CrI) in kraft, flow-through kraft and polysulphide–anthraquinone (PS–AQ) pulps of pine and birch containing various amounts of hemicelluloses. The applicability of acid hydrolysis and the purely spectroscopic proton spin-relaxation based spectral edition (PSRE) method to remove the interfering hemicellulose signals prior to the determination of CrI were

Tiina Liitiä; Sirkka Liisa Maunu; Bo Hortling; Tarja Tamminen; Osmo Pekkala; Antero Varhimo

2003-01-01

200

Three-dimensional experiment for solid-state NMR of aligned protein samples in high field magnets  

Microsoft Academic Search

A pulse sequence that yields three-dimensional 1H chemical shift \\/ 1H-15N heteronuclear dipolar coupling \\/ 15N chemical shift solid-state NMR spectra is demonstrated on a uniformly 15N labeled membrane protein in magnetically aligned phospholipid bilayers. Based on SAMPI4, the pulse sequence yields high\\u000a resolution in all three dimensions at a 1H resonance frequency of 900 MHz with the relatively low rf

Alexander A. Nevzorov; Sang Ho Park

2007-01-01

201

Time dependent solid-state 13C NMR study on alkaline hydrolysis of polyacrylonitrile hollow fiber ultrafiltration membranes  

Microsoft Academic Search

The effects of alkaline hydrolysis on the chemical structure of polyacrylonitrile (PAN) hollow fiber ultrafiltration (UF) membrane were studied using solid-state 13C NMR spectroscopy. The PAN membrane was hydrolyzed in an NaOH solution of pH 13, which is generally used in water industry for anti-fouling treatments of UF membranes but is much weaker than the alkaline concentrations (0.5–2.5N) used so

Yong Hun Choi; Chang Min Choi; Dae Ho Choi; Younkee Paik; Byung Jae Park; Young Kil Joo; Nam Joon Kim

2011-01-01

202

A combined solid-state NMR and X-ray crystallography study of the bromide ion environments in triphenylphosphonium bromides.  

PubMed

Multinuclear ((31)P and (79/81)Br), multifield (9.4, 11.75, and 21.1 T) solid-state nuclear magnetic resonance experiments are performed for seven phosphonium bromides bearing the triphenylphosphonium cation, a molecular scaffold found in many applications in chemistry. This is undertaken to fully characterise their bromine electric field gradient (EFG) tensors, as well as the chemical shift (CS) tensors of both the halogen and the phosphorus nuclei, providing a rare and novel insight into the local electronic environments surrounding them. New crystal structures, obtained from single-crystal X-ray diffraction, are reported for six compounds to aid in the interpretation of the NMR data. Among them is a new structure of BrPPh(4), because the previously reported one was inconsistent with our magnetic resonance data, thereby demonstrating how NMR data of non-standard nuclei can correct or improve X-ray diffraction data. Our results indicate that, despite sizable quadrupolar interactions, (79/81)Br magnetic resonance spectroscopy is a powerful characterisation tool that allows for the differentiation between chemically similar bromine sites, as shown through the range in the characteristic NMR parameters. (35/37)Cl solid-state NMR data, obtained for an analogous phosphonium chloride sample, provide insight into the relationship between unit cell volume, nuclear quadrupolar coupling constants, and Sternheimer antishielding factors. The experimental findings are complemented by gauge-including projector-augmented wave (GIPAW) DFT calculations, which substantiate our experimentally determined strong dependence of the largest component of the bromine CS tensor, ?(11), on the shortest Br-P distance in the crystal structure, a finding that has possible application in the field of NMR crystallography. This trend is explained in terms of Ramsey's theory on paramagnetic shielding. Overall, this work demonstrates how careful NMR studies of underexploited exotic nuclides, such as (79/81)Br, can afford insights into structure and bonding environments in the solid state. PMID:22434717

Burgess, Kevin M N; Korobkov, Ilia; Bryce, David L

2012-04-27

203

Impact of reduction on the properties of metal bisdithiolenes: multinuclear solid-state NMR and structural studies on Pt(tfd)2 and its reduced forms.  

PubMed

Transition-metal dithiolene complexes have interesting structures and fascinating redox properties, making them promising candidates for a number of applications, including superconductors, photonic devices, chemical sensors, and catalysts. However, not enough is known about the molecular electronic origins of these properties. Multinuclear solid-state NMR spectroscopy and first-principles calculations are used to examine the molecular and electronic structures of the redox series [Pt(tfd)(2)](z-) (tfd = S(2)C(2)(CF(3))(2); z = 0, 1, 2; the anionic species have [NEt(4)](+) countercations). Single-crystal X-ray structures for the neutral (z = 0) and the fully reduced forms (z = 2) were obtained. The two species have very similar structures but differ slightly in their intraligand bond lengths. (19)F-(195)Pt CP/CPMG and (195)Pt magic-angle spinning (MAS) NMR experiments are used to probe the diamagnetic (z = 0, 2) species, revealing large platinum chemical shielding anisotropies (CSA) with distinct CS tensor properties, despite the very similar structural features of these species. Density functional theory (DFT) calculations are used to rationalize the large platinum CSAs and CS tensor orientations of the diamagnetic species using molecular orbital (MO) analysis, and are used to explain their distinct molecular electronic structures in the context of the NMR data. The paramagnetic species (z = 1) is examined using both EPR spectroscopy and (13)C and (19)F MAS NMR spectroscopy. Platinum g-tensor components were determined by using solid-state EPR experiments. The unpaired electron spin densities at (13)C and (19)F nuclei were measured by employing variable-temperature (13)C and (19)F NMR experiments. DFT and ab initio calculations are able to qualitatively reproduce the experimentally measured g-tensor components and spin densities. The combination of experimental and theoretical data confirm localization of unpaired electron density in the pi-system of the dithiolene rings. PMID:19236015

Tang, Joel A; Kogut, Elzbieta; Norton, Danielle; Lough, Alan J; McGarvey, Bruce R; Fekl, Ulrich; Schurko, Robert W

2009-03-19

204

Contribution of multi-nuclear solid state NMR to the characterization of the Thalassiosira pseudonana diatom cell wall.  

PubMed

A major issue in the study of biosilicification processes is the harsh chemical conditions required for silica dissolution, which often lead to denaturation of the associated bio-organic matter. In order to demonstrate the potential of solid state NMR for investigating silicified materials of natural origin, this technique was applied to isotopically enriched Thalassiosira pseudonana diatom cells. (29)Si, (1)H,(31)P, (13)C and (15)N solid state NMR studies were performed on whole cells, SDS-extracted and H(2)O(2)-cleaned silica shells. Cross-polarization techniques were useful for identifying the presence of mobile and rigid molecules, allowing loosely bound and silica-entrapped species to be discriminated. Successive cleaning procedures efficiently eliminated weakly associated organic matter. The H(2)O(2)-cleaned silica shell still contained carbohydrates (mainly chitin) and proteins as well as lipids. This suggests that the role of lipids in diatom shell formation may have been underestimated so far, demonstrating the potential of solid state NMR for studying composite biomaterials. PMID:18278484

Tesson, Benoit; Masse, Sylvie; Laurent, Guillaume; Maquet, Jocelyne; Livage, Jacques; Martin-Jézéquel, Véronique; Coradin, Thibaud

2008-04-01

205

Solid-state 115In and 31P NMR studies of triarylphosphine indium trihalide adducts.  

PubMed

Solid-state (115)In and (31)P NMR spectroscopy, relativistic density functional theory (DFT) calculations, and single-crystal X-ray diffraction were used to investigate a series of triarylphosphine indium(III) trihalide adducts, X(3)In(PR(3)) and X(3)In(PR(3))(2) (X = Cl, Br or I; PR(3) = triarylphosphine ligand). The electric field gradient tensors at indium as well as the indium and phosphorus magnetic shielding tensors and the direct and indirect (115)In-(31)P spin-spin coupling were characterized; for complexes possessing a C(3) symmetry axis, the anisotropy in the indirect spin-spin coupling, DeltaJ((115)In,(31)P), was also determined. The (115)In quadrupolar coupling constants, C(Q)((115)In), range from +/-1.25 +/- 0.10 to -166.0 +/- 2.0 MHz. For any given phosphine ligand, the indium nuclei are most shielded for X = I and least shielded for X = Cl, a trend also observed for other group-13 nuclei in M(III) complexes. This experimental trend, attributed to spin-orbit effects of the halogen ligands, is reproduced by the DFT calculations. The spans of the indium magnetic shielding tensors for these complexes, delta(11)-delta(33), range from 40 +/- 7 to 710 +/- 60 ppm; those determined for phosphorus range from 28 +/- 1.5 to 50 +/- 3 ppm. Values of (1)J((115)In,(31)P) range from 550 +/- 20 to 2500 +/- 20 Hz. For any given halide, the (1)J((115)In,(31)P) values generally increase with increasing basicity of the PR(3) ligand. Calculated values of (1)J((115)In,(31)P) and DeltaJ((115)In,(31)P) duplicate experimental trends and indicate that both the Fermi-contact and spin-dipolar Fermi-contact mechanisms make important contributions to the (1)J((115)In,(31)P) tensors. PMID:20349956

Chen, Fu; Ma, Guibin; Bernard, Guy M; Cavell, Ronald G; McDonald, Robert; Ferguson, Michael J; Wasylishen, Roderick E

2010-04-21

206

2H-solid state NMR and DSC study of isobutyric acid in mesoporous silica materials.  

PubMed

Solid state deuterium NMR has been used to study the molecular motion of d(6)-isobutyric acid (d(6)-iBA) in the pure (unconfined) state and confined in the cylindrical pores of two periodic mesoporous silica materials (MCM-41, pore size 3.3 nm and SBA-15, pore size 8 nm), and in a controlled pore glass (CPG-10-75, pore size ca. 10 nm). The line shape analysis of the spectra at different temperatures revealed three rotational states of the iBA molecules: liquid (fast anisotropic reorientation of the molecule), solid I (rotation of the methyl group) and solid II (no rotational motion on the time scale of the experiment). Transition temperatures between these states were determined from the temperature dependence of the fraction of molecules in these states. Whereas the solid I-solid II transition temperature is not affected by confinement, a significant lowering of the liquid-solid I transition temperature in the pores relative to the bulk acid was found for the three matrix materials, exhibiting an unusual dependence on pore size and pore morphology. Complementary DSC measurements on the same systems show that the rotational melting (solid I-liquid) of d(6)-iBA in the pores occurs at a temperature 20-45 K below the thermodynamic melting point. This finding indicated that the decoupling of rotational and translational degrees of freedom in phase transitions in confined systems previously found for benzene is not restricted to molecules with non-specific interactions, but represents a more general phenomenon. PMID:17487322

Vyalikh, A; Emmler, Th; Shenderovich, I; Zeng, Y; Findenegg, G H; Buntkowsky, G

2007-06-14

207

Solid-state NMR studies of aminocarboxylic salt bridges in L-lysine modified cellulose.  

PubMed

LysCel is a cellulose-based material in which l-lysine molecules are grafted with their amino side chains to the cellulose hydroxyl groups. This modification increases considerably the mechanical strength and resistance of cellulosic structures toward water. It has been attributed to the formation of double salt bridges between lysine aminocarboxyl groups in the zwitterionic state. In order to characterize this unusual structure, we have performed high-resolution solid-state (15)N and (13)C CPMAS NMR experiments on LysCel samples labeled with (15)N in the alpha-position or epsilon-position. Furthermore, (13)C-(15)N REDOR experiments were performed on LysCel where half of the aminocarboxyl groups were labeled in 1-position with 13C and the other half in alpha-position with (15)N. The comparison with the 13C and 15N chemical shifts of l-leucine lyophilized at different pH shows that the aminocarboxyl groups of LysCel are indeed zwitterionic. The REDOR experiments indicate distances of about 3.5 A between the carboxyl carbon and the nitrogen atoms of different aminocarboxyl groups, indicating that the latter are in close contact with each other. However, the data are not compatible with isolated aminocarboxyl dimers but indicate the assembly of zwitterionic aminocarboxyl dimers either in a flat ribbon or as tetramers, exhibiting similar intra- and interdimer (13)C...(15)N distances. This interaction of several aminocarboxyl groups is responsible for the zwitterionic state, in contrast to the gas phase, where amino acid dimers exhibiting two OHN hydrogen bonds are neutral. PMID:19117475

Manríquez, Ricardo; López-Dellamary, Fernando A; Frydel, Jaroslaw; Emmler, Thomas; Breitzke, Hergen; Buntkowsky, Gerd; Limbach, Hans-Heinrich; Shenderovich, Ilja G

2009-01-29

208

Radiation oxidation of polypropylene: A solid-state 13C NMR study using selective isotopic labeling  

NASA Astrophysics Data System (ADS)

Polypropylene samples, in which the three different carbon atoms along the chain were selectively labeled with carbon-13, were subjected to radiation under inert and air atmospheres, and to post-irradiation exposure in air at various temperatures. By using solid-state 13C NMR measurements at room temperature, we have been able to identify and quantify the oxidation products. The isotopic labeling provides insight into chemical reaction mechanisms, since oxidation products can be traced back to their positions of origin on the macromolecule. The major products include peroxides and alcohols, both formed at tertiary carbon sites along the chain. Other products include methyl ketones, acids, esters, peresters, and hemiketals formed from reaction at the tertiary carbon, together with in-chain ketones and esters from reaction at the secondary chain carbon. No evidence is found of products arising from reactions at the methyl side chain. Significant temperature-dependent differences are apparent; for example much higher yields of chain-end methyl ketones, which are the indicator product of chain scission, are generated for both elevated temperature irradiation and for post-irradiation treatment at elevated temperatures. Time-dependent plots of yields of the various oxidation products have been obtained under a wide range of conditions, including the post-irradiation oxidation of a sample at room temperature in air that has been monitored for 2 years. Radiation-oxidation products of polypropylene are contrasted to products measured for 13C-labeled polyethylene in an earlier investigation: the peroxides formed in irradiated polypropylene are remarkably longer lived, the non-peroxidic products are significantly different, and the overall ratios of oxidation products in polypropylene change relatively little as a function of the extent of oxidation.

Mowery, Daniel M.; Assink, Roger A.; Derzon, Dora K.; Klamo, Sara B.; Bernstein, Robert; Clough, Roger L.

2007-05-01

209

Structural water in carbonated hydroxylapatite and fluorapatite: confirmation by solid state (2)H NMR.  

PubMed

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. PMID:22057814

Yoder, Claude H; Pasteris, Jill D; Worcester, Kimberly N; Schermerhorn, Demetra V

2012-01-01

210

Advanced solid-state NMR approaches for structure determination of membrane proteins and amyloid fibrils.  

PubMed

Solid-state NMR (SSNMR) spectroscopy has become an important technique for studying the biophysics and structure biology of proteins. This technique is especially useful for insoluble membrane proteins and amyloid fibrils, which are essential for biological functions and are associated with human diseases. In the past few years, as major contributors to the rapidly advancing discipline of biological SSNMR, we have developed a family of methods for high-resolution structure determination of microcrystalline, fibrous, and membrane proteins. Key developments include order-of-magnitude improvements in sensitivity, resolution, instrument stability, and sample longevity under data collection conditions. These technical advances now enable us to apply new types of 3D and 4D experiments to collect atomic-resolution structural restraints in a site-resolved manner, such as vector angles, chemical shift tensors, and internuclear distances, throughout large proteins. In this Account, we present the technological advances in SSNMR approaches towards protein structure determination. We also describe the application of those methods for large membrane proteins and amyloid fibrils. Particularly, the SSNMR measurements of an integral membrane protein DsbB support the formation of a charge-transfer complex between DsbB and ubiquinone during the disulfide bond transfer pathways. The high-resolution structure of the DsbA-DsbB complex demonstrates that the joint calculation of X-ray and SSNMR restraints for membrane proteins with low-resolution crystal structure is generally applicable. The SSNMR investigations of ?-synuclein fibrils from both wild type and familial mutants reveal that the structured regions of ?-synuclein fibrils include the early-onset Parkinson's disease mutation sites. These results pave the way to understanding the mechanism of fibrillation in Parkinson's disease. PMID:23659727

Tang, Ming; Comellas, Gemma; Rienstra, Chad M

2013-09-17

211

Local environment and distribution of alkali ions in polyelectrolyte complexes studied by solid-state NMR.  

PubMed

Polyelectrolyte complexes (PECs) formed by the addition of substoichiometric amounts of (poly(diallyldimethyl ammonium chloride)) (PDADMAC) solutions to sodium or lithium poly(styrene sulfonate) (Na- or Li-PSS) solution contain adjustable amounts of charge balancing Li(+) or Na(+) cations, which possess ionic mobility of interest for solid electrolyte applications. Very little is known regarding the local environments and the spatial distributions of these cations and their interactions with the polyelectrolyte chains in these amorphous materials. To address such issues, the present work develops a comprehensive solid state NMR strategy based on complementary high-resolution magic-angle spinning (MAS) NMR and various dipolar spectroscopic techniques. (6,7)Li and (23)Na chemical shifts measured on a series of PECs with general composition described by B((2x-1))PSS(x)PDADMA((1-x)) (B = Li or Na and 0.53 ?x? 1) reveal composition-independent local cation environments. In contrast, (7)Li{(6)Li} spin echo double resonance (SEDOR) experiments measured on (6)Li enriched materials and (7)Li{(1)H} rotational echo double resonance (REDOR) experiments are consistent with an approximately random ion distribution. The same conclusion is suggested by (23)Na{(1)H} REDOR measurements on the analogous sodium containing system indicating a non-segregated PEC structure. In apparent contrast to this conclusion, (23)Na spin echo decay spectroscopy yields nearly constant dipolar second moments over a wide composition range. This can be explained by considering that the (23)Na spin echo decays are affected by both (23)Na-(23)Na homonuclear dipolar couplings and (23)Na-(1)H heteronuclear dipolar interactions in the presence of strong homonuclear (1)H-(1)H spin exchange. In protonated Na-PSS both contributions are of comparable magnitude. In the PECs the contribution from (23)Na-(23)Na interactions decreases, while that from (23)Na-(1)H dipolar couplings with the protons from the PDADMA chains increases with decreasing Na content, resulting in superimposed opposite dependences on the ion concentration. All results for Li and Na containing PECs point at a non-phase separated polymer network with uniform ionic sites of very similar environment. The cations can be viewed as randomly distributed and located close to the polyion sulfate groups. PMID:21465039

Causemann, Susanne; Schönhoff, Monika; Eckert, Hellmut

2011-05-21

212

Lipid bilayer preparations of membrane proteins for oriented and magic-angle spinning solid-state NMR samples  

PubMed Central

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

Das, Nabanita; Murray, Dylan T; Cross, Timothy A

2014-01-01

213

Chemistry and Physics of Lipids 132 (2004) 89100 Solid-state nuclear magnetic resonance studies of HIV and  

E-print Network

Chemistry and Physics of Lipids 132 (2004) 89­100 Solid-state nuclear magnetic resonance studies in lipid bilayers have been probed with 15 N solid-state nuclear magnetic resonance (NMR) spectroscopy, the data suggest that the solid-state NMR experiments can test models which correlate peptide orientation

Weliky, David

214

With the view of enhancing the resolution in solid state NMR, we investigated the use of single crystals in CP-MAS. Model  

E-print Network

a significantly wider impact on structure determination than previously thought. Increasing 13C CP-MAS NMR of Florida. Citation: S. Dugar, R. Fu., N.S. Dalal, Increasing 13C CP-MAS NMR Resolution Using SingleWith the view of enhancing the resolution in solid state NMR, we investigated the use of single

215

CHHC and [superscript 1]H–[superscript 1]H magnetization exchange: Analysis by experimental solid-state NMR and 11-spin density-matrix simulations  

E-print Network

A protocol is presented for correcting the effect of non-specific cross-polarization in CHHC solid-state MAS NMR experiments, thus allowing the recovery of the [superscript 1]H–[superscript 1]H magnetization exchange ...

Aluas, Mihaela

216

Applications of DNP and solid-state NMR for protein structure determination  

E-print Network

Magic Angle Spinning (MAS) solid state nuclear magnetic resonance (SSNMR) is a developing method for determining the structures and studying the dynamics and functions of biological molecules. This method is particularly ...

Mayrhofer, Rebecca Maria

2010-01-01

217

Methods for Increasing Sensitivity and Throughput of Solid-State NMR Spectroscopy of Pharmaceutical Solids  

E-print Network

Solid-state nuclear magnetic resonance (SSNMR) spectroscopy has been demonstrated to be a powerful technique for investigating solid dosage formulations. SSNMR has the ability to determine physical form, molecular structure, ...

Schieber, Loren

2010-01-22

218

A solid-state 13C NMR analysis of molecular dynamics in aramide polymers.  

PubMed

The local dynamics of aromatic cores was analyzed for a homologous series of polyamides in the solid phase incorporating phenyl, biphenyl and naphthyl groups. Preliminary wide-line and spin-relaxation variable-temperature (1)H NMR measurements revealed the presence of thermally activated molecular motions for each polymer studied. A number of (13)C NMR experiments were then implemented to further clarify the nature and extent of such motions. These included (1)H-(13)C 2D separate-local-field measurements, whose line shapes revealed that motions involved for all cases a superposition of states. These could in principle be associated with rigid and mobile populations in these semi-crystalline aramides, a model that yielded a proper description of the spectra at all temperatures. To further probe this model the relaxation behavior of the aramides'(13)C spins was monitored in the rotating frame as a function of temperature, in both the presence and absence of homonuclear (1)H-(1)H decoupling. The variations observed in these measurements evidenced a thermally activated, relatively broad distribution of motional rates in the polymers. Editing the 2D local-field data according to the (13)C relaxation also supported this heterogeneous dynamic model. The mechanism underlying this behavior and implications towards the (13)C analysis of motions in aramides in particular and complex polymers in general, is briefly discussed. PMID:16199142

McElheny, Dan; Frydman, Veronica; Frydman, Lucio

2006-02-01

219

Tannin fingerprinting in vegetable tanned leather by solid state NMR spectroscopy and comparison with leathers tanned by other processes.  

PubMed

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 ²?Al-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. PMID:21278677

Romer, Frederik H; Underwood, Andrew P; Senekal, Nadine D; Bonnet, Susan L; Duer, Melinda J; Reid, David G; van der Westhuizen, Jan H

2011-01-01

220

Design of a triple resonance magic angle sample spinning probe for high field solid state nuclear magnetic resonance  

NASA Astrophysics Data System (ADS)

Standard design and construction practices used in building nuclear magnetic resonance (NMR) probes for the study of solid state samples become difficult if not entirely impractical to implement as the 1H resonance frequency approaches the self resonance frequency of commercial capacitors. We describe an approach that utilizes short variable transmission line segments as tunable reactances. Such an approach effectively controls stray reactances and provides a higher Q alternative to ceramic chip capacitors. The particular probe described is built to accommodate a 2.5 mm magic angle spinning rotor system, and is triply tuned to 13C, 15N, and 1H frequencies for use at 18.8 T (200, 80, and 800 MHz, respectively). Isolation of the three radio frequency (rf) channels is achieved using both a rejection trap and a transmission line notch filter. The compact geometry of this design allows three channels with high power handling capability to fit in a medium bore (63 mm) magnet. Extended time variable temperature operation is integral to the mechanical design, enabling the temperature control necessary for investigation of biological macromolecules. Accurate measurement of the air temperature near the sample rotor is achieved using a fiber optic thermometer, which does not interfere with the rf electronics. We also demonstrate that acceptable line shapes are only readily achieved using zero magnetic susceptibility wire in construction of the sample coil. Computer simulation of the circuit aided in the physical design of the probe. Representative data illustrating the efficiency, rf homogeneity, and signal to noise factor of the probe are presented.

Martin, Rachel W.; Paulson, Eric K.; Zilm, Kurt W.

2003-06-01

221

High-resolution solid-state NMR spectroscopy as a tool for investigation of enantioselective inclusion complexation.  

PubMed

In this paper, we showed the application of solid state-NMR (SS NMR) spectroscopy in structural studies of chiral compounds employing sample of (E)-1-diphenylphosphinoylpent-3-en-2-ol 1 as a model compound. Racemate of 1 was fully characterized by NMR techniques (both in liquid and solid phase) and X-ray crystallography. Theoretical calculations employing the GIAO approach were used to explain the influence of hydrogen bonding on 31P NMR shielding parameter in racemate. Enantioselective inclusion complexation (EIC) method with TADDOL as host molecule was applied to separate of enantiomers. The formation of host-guest complex and decomplexation procedure was monitored by means of the SS NMR. The liquid-state NMR, due to similarity of 13C and 31P spectral parameters was not able to distinguish racemate from enantiomer. In the solid phase, owing to distinction of hydrogen bonding and molecular packing in the crystal lattice, racemate and enantiomers were easy recognized by NMR spectroscopy. PMID:17537616

Gajda, J; Jeziorna, A; Ciesielski, W; Potrzebowski, W M; Prezdo, W W; Potrzebowski, M J

2007-05-01

222

250GHz CW gyrotron oscillator for dynamic nuclear polarization in biological solid state NMR.  

PubMed

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 (1)H 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-(13)C, (15)N]-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 12 mA) at frequencies between 320 and 365 GHz, suggesting an efficient route for the generation of even higher frequency radiation. The low starting currents were attributed to an elevated cavity Q, which is confirmed by cavity thermal load measurements. We conclude with an appendix containing a detailed description of the control system that safely automates all aspects of the gyrotron operation. PMID:17942352

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

223

Ultra-broadband NMR probe: numerical and experimental study of transmission line NMR probe.  

PubMed

We have reinvestigated a transmission line NMR probe first published by Lowe and co-workers in 1970s [Rev. Sci. Instrum. 45 (1974) 631; 48 (1977) 268] numerically and experimentally. The probe is expected to be ultra-broadband, thus might enable new types of solid-state NMR experiments. The NMR probe consists of a coil and capacitors which are connected to the coil at regular intervals. The circuit is the same as a cascaded LC low-pass filter, except there are nonzero mutual inductances between different coil sections. We evaluated the mutual inductances by Neumann's formula and calculated the electrical characteristics of the probe as a function of a carrier frequency. We found that they were almost the same as those of a cascaded LC low-pass filter, when the inductance L of a section was estimated from the inductance of the whole coil divided by the number of the sections, and if C was set to the capacitance in a section. For example, the characteristic impedance of a transmission line coil is given by Z=(L/C)(1/2). We also calculated the magnitude and the distribution of RF magnetic field inside the probe. The magnitude of RF field decreases when the carrier frequency is increased because the phase delay between neighboring sections is proportional to the carrier frequency. For cylindrical coils, the RF field is proportional to (pinu/2nu(d))(1/2)exp(-nu/nu(d)), where the decay frequency nu(d) is determined by the dimensions of the coil. The observed carrier frequency thus must be much smaller than the decay frequency. This condition restricts the size of transmission line coils. We made a cylindrical coil for a 1H NMR probe operating below 400 MHz. It had a diameter 2.3mm and a pitch 1.2mm. Five capacitors of 6pF were connected at every three turns. The RF field strength was 40 and 60 kHz at the input RF power 100 W by a calculation and by experiments, respectively. The calculations showed that the RF field inhomogeneity along the coil axis was caused by a standing wave of current, which arose from the reflections at the coil ends. The calculation showed that the homogeneity could be improved by decreasing the pitch near the both ends and making their impedance close to that at the center. PMID:12810012

Kubo, Atsushi; Ichikawa, Shinji

2003-06-01

224

Chemical and nanometer-scale structure of kerogen and its change during thermal maturation investigated by advanced solid-state 13C NMR spectroscopy  

USGS Publications Warehouse

We have used advanced and quantitative solid-state nuclear magnetic resonance (NMR) techniques to investigate structural changes in a series of type II kerogen samples from the New Albany Shale across a range of maturity (vitrinite reflectance R0 from 0.29% to 1.27%). Specific functional groups such as CH3, CH2, alkyl CH, aromatic CH, aromatic C-O, and other nonprotonated aromatics, as well as "oil prone" and "gas prone" carbons, have been quantified by 13C NMR; atomic H/C and O/C ratios calculated from the NMR data agree with elemental analysis. Relationships between NMR structural parameters and vitrinite reflectance, a proxy for thermal maturity, were evaluated. The aromatic cluster size is probed in terms of the fraction of aromatic carbons that are protonated (???30%) and the average distance of aromatic C from the nearest protons in long-range H-C dephasing, both of which do not increase much with maturation, in spite of a great increase in aromaticity. The aromatic clusters in the most mature sample consist of ???30 carbons, and of ???20 carbons in the least mature samples. Proof of many links between alkyl chains and aromatic rings is provided by short-range and long-range 1H-13C correlation NMR. The alkyl segments provide most H in the samples; even at a carbon aromaticity of 83%, the fraction of aromatic H is only 38%. While aromaticity increases with thermal maturity, most other NMR structural parameters, including the aromatic C-O fractions, decrease. Aromaticity is confirmed as an excellent NMR structural parameter for assessing thermal maturity. In this series of samples, thermal maturation mostly increases aromaticity by reducing the length of the alkyl chains attached to the aromatic cores, not by pronounced growth of the size of the fused aromatic ring clusters. ?? 2010 Elsevier Ltd. All rights reserved.

Mao, J.; Fang, X.; Lan, Y.; Schimmelmann, A.; Mastalerz, M.; Xu, L.; Schmidt-Rohr, K.

2010-01-01

225

Correlating lipid bilayer fluidity with sensitivity and resolution of polytopic membrane protein spectra by solid-state NMR spectroscopy.  

PubMed

Solid-state NMR spectroscopy has emerged as an excellent tool to study the structure and dynamics of membrane proteins under native-like conditions in lipid bilayers. One of the key considerations in experimental design is the uniaxial rotational diffusion of the protein that can affect the NMR spectral observables. In this regard, temperature plays a fundamental role in modulating the phase properties of the lipids, which directly influences the rotational diffusion rate of the protein in the bilayer. In fact, it is well established that below the main phase transition temperature of the lipid bilayer the protein's motion is significantly slowed while above this critical temperature the rate is increased. In this article, we carried out a systematic comparison of the signal intensity and spectral resolution as a function of temperature using magic-angle-spinning (MAS) solid-state NMR spectroscopy. These observables were directly correlated with the relative fluidity of the lipid bilayer as inferred from differential scanning calorimetry (DSC). We applied our hybrid biophysical approach to two polytopic membrane proteins from the small multidrug resistance family (EmrE and SugE) reconstituted into model membrane lipid bilayers (DMPC-14:0 and DPPC-16:0). From these experiments, we conclude that the rotational diffusion giving optimal spectral resolution occurs at a bilayer fluidity of ~5%, which corresponds to the percentage of lipids in the fluid or liquid-crystalline fraction. At the temperature corresponding to this critical value of fluidity, there is sufficient mobility to reduce inhomogeneous line broadening that occurs at lower temperatures. A greater extent of fluidity leads to faster uniaxial rotational diffusion and a sigmoidal-type reduction in the NMR signal intensity, which stems from intermediate-exchange dynamics where the motion has a similar frequency as the NMR observables (i.e., dipolar couplings and chemical shift anisotropy). These experiments provide insight into the optimal temperature range and corresponding bilayer fluidity to study membrane proteins by solid-state NMR spectroscopy. This article is part of a Special Issue entitled, NMR Spectroscopy for Atomistic Views of Biomembranes and Cell Surfaces. Guest Editors: Lynette Cegelski and David P. Weliky. PMID:24835018

Banigan, James R; Gayen, Anindita; Traaseth, Nathaniel J

2015-01-01

226

3D DUMAS: Simultaneous acquisition of three-dimensional magic angle spinning solid-state NMR experiments of proteins  

NASA Astrophysics Data System (ADS)

Using the DUMAS (Dual acquisition Magic Angle Spinning) solid-state NMR approach, we created new pulse schemes that enable the simultaneous acquisition of three dimensional (3D) experiments on uniformly 13C, 15N labeled proteins. These new experiments exploit the simultaneous cross-polarization (SIM-CP) from 1H to 13C and 15N to acquire two 3D experiments simultaneously. This is made possible by bidirectional polarization transfer between 13C and 15N and the long living 15N z-polarization in solid state NMR. To demonstrate the power of this approach, four 3D pulse sequences (NCACX, CANCO, NCOCX, CON(CA)CX) are combined into two pulse sequences (3D DUMAS-NCACX-CANCO, 3D DUMAS-NCOCX-CON(CA)CX) that allow simultaneous acquisition of these experiments, reducing the experimental time by approximately half. Importantly, the 3D DUMAS-NCACX-CANCO experiment alone makes it possible to obtain the majority of the backbone sequential resonance assignments for microcrystalline U-13C,15N ubiquitin. The DUMAS approach is general and applicable to many 3D experiments, nearly doubling the performance of NMR spectrometers.

Gopinath, T.; Veglia, Gianluigi

2012-07-01

227

The topology of lysine-containing amphipathic peptides in bilayers by circular dichroism, solid-state NMR, and molecular modeling.  

PubMed Central

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

Vogt, B; Ducarme, P; Schinzel, S; Brasseur, R; Bechinger, B

2000-01-01

228

Solution and Solid-State NMR Structural Studies of Antimicrobial Peptides LPcin-I and LPcin-II  

PubMed Central

Lactophoricin (LPcin-I) is an antimicrobial, amphiphatic, cationic peptide with 23-amino acid residues isolated from bovine milk. Its analogous peptide, LPcin-II, lacks six N-terminal amino acids compared to LPcin-I. Interestingly, LPcin-II does not display any antimicrobial activity, whereas LPcin-I inhibits the growth of both Gram-negative and Gram-positive bacteria without exhibiting any hemolytic activity. Uniformly 15N-labeled LPcin peptides were prepared by the recombinant expression of fusion proteins in Escherichia coli, and their properties were characterized by electrospray ionization mass spectrometry, circular dichroism spectroscopy, and antimicrobial activity tests. To understand the structure-activity relationship of these two peptides, they were studied in model membrane environments by a combination of solution and solid-state NMR spectroscopy. We determined the tertiary structure of LPcin-I and LPcin-II in the presence of dodecylphosphorylcholine micelles by solution NMR spectroscopy. Magnetically aligned unflipped bicelle samples were used to investigate the structure and topology of LPcin-I and LPcin-II by solid-state NMR spectroscopy. PMID:21889457

Park, Tae-Joon; Kim, Ji-Sun; Ahn, Hee-Chul; Kim, Yongae

2011-01-01

229

Quantitative analysis of backbone motion in proteins using MAS solid-state NMR spectroscopy  

Microsoft Academic Search

We present a comprehensive analysis of protein dynamics for a micro-crystallin protein in the solid-state. Experimental data\\u000a include 15N T\\u000a 1 relaxation times measured at two different magnetic fields as well as 1H–15N dipole, 15N CSA cross correlated relaxation rates which are sensitive to the spectral density function J(0) and are thus a measure of T\\u000a 2 in the solid-state.

Veniamin Chevelkov; Uwe Fink; Bernd Reif

2009-01-01

230

A study of a moleculartweezer host-guest system by a combination of quantum-chemical calculations and solid-state NMR experiments.  

PubMed

A study of a host-guest system consisting of a naphthalene-spaced tweezer with a 1,4 dicyanobenzene guest molecule is presented. The complex is investigated using a combination of quantum-chemical calculations and solid-state NMR experiments. The advantages of such an approach are illustrated. The focus is on the calculation of (1) 1H NMR and (2) 13C NMR chemical shifts for model fragments of the solid-state structure, (3) the analysis of host-guest interactions important for molecular recognition, and (4) the investigation of the process of a guest molecule rotation. For modeling the solid-state structure, up to three host-guest units are considered and the convergence with respect to the size of the solid-state fragment is investigated. PMID:12469808

Ochsenfeld, Christian; Koziol, Felix; Brown, Steven P; Schaller, Torsten; Seelbach, Uta P; Klärner, Frank-Gerrit

2002-01-01

231

Conformation of the glycosidic linkage in a disaccharide investigated by double-quantum solid-state NMR.  

PubMed

Double-quantum heteronuclear local field NMR is performed on a sample of a 13C2-labeled disaccharide, in which the two 13C spins are located on opposite sides of the glycosidic linkage. The evolution of the double-quantum coherences is found to be consistent with the solid-state conformation of the molecule, as previously determined by X-ray diffraction. The dependence of the double-quantum evolution on the glycosidic torsional angles is examined by using a graphical molecular manipulation program interfaced to a numerical spin simulation module. PMID:11444948

Ravindranathan, S; Karlsson, T; Lycknert, K; Widmalm, G; Levitt, M H

2001-07-01

232

Multiple acquisition/multiple observation separated local field/chemical shift correlation solid-state magic angle spinning NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Multiple acquisition spectroscopy (MACSY) experiments that enable multiple free induction decays to be recorded during individual experiments are demonstrated. In particular, the experiments incorporate separated local field spectroscopy into homonuclear and heteronuclear correlation spectroscopy. The measured heteronuclear dipolar couplings are valuable in structure determination as well as in enhancing resolution by providing an additional frequency axis. In one example four different three-dimensional spectra are obtained in a single experiment, demonstrating that substantial potential saving in experimental time is available when multiple multi-dimensional spectra are required as part of solid-state NMR studies.

Das, Bibhuti B.; Opella, Stanley J.

2014-08-01

233

Solid state 13C NMR and FT-IR spectroscopy of the cocoon silk of two common spiders  

NASA Astrophysics Data System (ADS)

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 ?-sheet structures, whereas that of Araneus diadematus shows a more complex structure, containing also ?-strands and ?-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.

Bramanti, Emilia; Catalano, Donata; Forte, Claudia; Giovanneschi, Mario; Masetti, Massimo; Veracini, Carlo Alberto

2005-11-01

234

Investigating the interaction between peptides of the amphipathic helix of Hcf106 and the phospholipid bilayer by solid-state NMR spectroscopy  

PubMed Central

The chloroplast twin arginine translocation (cpTat) system transports highly folded precursor proteins into the thylakoid lumen using the protonmotive force as its only energy source. Hcf106, as one of the core components of the cpTat system, is part of the precursor receptor complex and functions in the initial precursor-binding step. Hcf106 is predicted to contain a single amino terminal transmembrane domain followed by a Pro-Gly hinge, a predicted amphipathic ?-helix (APH), and a loosely structured carboxy terminus. Hcf106 has been shown biochemically to insert spontaneously into thylakoid membranes. To better understand the membrane active capabilities of Hcf106, we used solid-state NMR spectroscopy to investigate those properties of the APH. In this study, synthesized peptides of the predicted Hcf106 APH (amino acids 28–65) were incorporated at increasing mol% into 1-palmitoyl-2-oleoyl-sn-glycero-phosphocholine (POPC) and POPC/MGDG (monogalactosyldiacylglycerol; mole ratio 85:15) multilamellar vesicles (MLVs) to probe the peptide-lipid interaction. Solid-state 31P NMR and 2H NMR spectroscopic experiments revealed that the peptide perturbs the headgroup and the acyl chain regions of phospholipids as indicated by changes in spectral lineshape, chemical shift anisotropy (CSA) line width, and 2H order SCD parameters. In addition, the comparison between POPC MLVs and POPC/MGDG MLVs indicated that the lipid bilayer composition affected peptide perturbation of the lipids, and such perturbation appeared to be more intense in a system more closely mimicking a thylakoid membrane. PMID:24144541

Zhang, Lei; Liu, Lishan; Maltsev, Sergey; Lorigan, Gary A.; Dabney-Smith, Carole

2013-01-01

235

Immobilization and chelation of metal complexes with bifunctional phosphine ligands: a solid-state NMR study  

E-print Network

.5747 Garching, Germany 29Si CP MAS NMR shows that a transition-metalcomplex with two bifunctional phosphine or an addition reaction to surface siloxane groups takes place.'3 This can be seen in the 29Si CP MAS NMR-state NMR study Klaus D. Behringer and Janet Blumel" Anorganisch-chemisches Institut der TU Miinchen, 8

Bluemel, Janet

236

Crystallinity and compositional changes in carbonated apatites: Evidence from (31)P solid-state NMR, Raman, and AFM analysis.  

PubMed

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-) ?1 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 ?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. PMID:24273344

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

237

The use of solid state nuclear magnetic resonance (NMR) to study the effect of composition on the properties of equilibrium fluid cracking catalysts (FCCs)  

Microsoft Academic Search

Solid state nuclear magnetic resonance (NMR) spectroscopy together with microactivity testing have been used to characterize the changes that occur in a fluid cracking catalyst (FCC) during gas oil cracking in a refinery fluid catalytic cracking unit (FCCU). The 29Si NMR spectra of fresh FCCs show the well known five peaks pattern attributed to the presence of HY-type crystals. However,

M. L Occelli; U Voigt; H Eckert

2004-01-01

238

Quadrupole effects in high-resolution phosphorus-31 solid-state NMR spectra of triphenylphosphine copper(I) complexes  

NASA Astrophysics Data System (ADS)

High-resolution 31P solid-state NMR spectra of triphenylphosphine copper(I) complexes, obtained by combining proton dipolar decoupling, proton-phosphorus cross polarization, and magic-angle sample spinning, often reveal asymmetric quartets rather than single resonance lines. These splittings arise from coupling with the nuclear spin {3}/{2} of the quadrupolar copper nucleus. Theoretical NMR spectra of spins I = {1}/{2} coupled to spins S > {1}/{2} are presented for powders spinning at the magic angle. Scalar as well as dipolar interactions are considered for the S = 1 and S = {3}/{2} cases. The magnetic field dependence of the observed asymmetric quartets in bis(triphenylphosphine)copper(I)nitrate can be accounted for by assuming a combination of scalar and dipolar coupling between phosphorus and copper. The spectra allow the determination of the scalar coupling constant, the dipolar coupling constant, and the copper quadrupole constant. Also, their signs can be established.

Menger, E. M.; Veeman, W. S.

239

Solid-state NMR as an effective method of polymorphic analysis: solid dosage forms of clopidogrel hydrogensulfate.  

PubMed

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. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 104:106-113, 2015. PMID:25393324

Pindelska, Edyta; Szeleszczuk, Lukasz; Pisklak, Dariusz Maciej; Mazurek, Andrzej; Kolodziejski, Waclaw

2015-01-01

240

Residual methyl protonation in perdeuterated proteins for multi-dimensional correlation experiments in MAS solid-state NMR spectroscopy  

NASA Astrophysics Data System (ADS)

NMR studies involving perdeuterated proteins focus in general on exchangeable amide protons. However, non-exchangeable sites contain as well a small amount of protons as the employed precursors for protein biosynthesis are not completely proton depleted. The degree of methyl group protonation is in the order of 9% for CD 2H using >97% deuterium enriched glucose. We show in this manuscript that this small amount of residual protonation is sufficient to perform 2D and 3D MAS solid-state NMR experiments. In particular, we suggest a HCCH-TOBSY type experiment which we successfully employ to assign the methyl resonances in aliphatic side chains in a perdeuterated sample of the SH3 domain of chicken ?-spectrin.

Agarwal, Vipin; Reif, Bernd

2008-09-01

241

?B-Crystallin: A Hybrid Solid-State/Solution-State NMR Investigation Reveals Structural Aspects of the Heterogeneous Oligomer  

SciTech Connect

Atomic-level structural information on ?B-Crystallin (?B), 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 ?B assembled from 175-residue 20-kDa subunits. An ?100-residue ?-crystallin domain is common to all small heat-shock proteins, and solution-state NMR was performed on two different ?- crystallin domain constructs isolated from ?B. In vitro, the chaperone-like activities of full-length ?B and the isolated ?-crystallin domain are identical. Chemical shifts of the backbone and C? resonances have been obtained for residues 64–162 (?-crystallin domain plus part of the C-terminus) in ?B and the isolated ?-crystallin domain by solid-state and solution-state NMR, respectively. Both sets of data strongly predict six ?-strands in the ?-crystallin domain. A majority of residues in the ?-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 ?-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 ?B. Evidence for a novel dimerization motif in the human ?-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 ?-crystallin domain undergoes a dimer–monomer transition over the pH range 7.5–6.8. This steep pHdependent switch may be important for ?B to function optimally (e.g., to preserve the filament integrity of cardiac muscle proteins such as actin and desmin during cardiac ischemia, which is accompanied by acidosis).

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

242

Some studies on a solid-state sulfur probe for coal gasification systems  

NASA Technical Reports Server (NTRS)

As a part of a program for the development of a sulfur probe for monitoring the sulfur potential in coal gasification reactors, an investigation was conducted regarding the efficiency of the solid electrolyte cell Ar+H2+H2S/CaS+CaF2+(Pt)//CaF2//Pt)+CaF2+CaS/H2S+H2+Ar. A demonstration is provided of the theory, design, and operation of a solid-state sulfur probe based on CaF2 electrolyte. It was found that the cell responds to changes in sulfur potential in a manner predicted by the Nernst equation. The response time of the cell at 1225 K, after a small change in temperature or gas composition, was 2.5 Hr, while at a lower temperature of 990 K the response time was approximately 9 hr. The cell emf was insensitive to a moderate increase in the flow rate of the test gas and/or the reference gas. The exact factors affecting the slow response time of galvanic cells based on a CaF2 electrolyte have not yet been determined. The rate-limiting steps may be either the kinetics of electrode reactions or the rate of transport through the electrolyte.

Jacob, K. T.; Rao, D. B.; Nelson, H. G.

1978-01-01

243

Specification and visualization of anisotropic interaction tensors in polypeptides and numerical simulations in biological solid-state NMR.  

PubMed

Software facilitating numerical simulation of solid-state NMR experiments on polypeptides is presented. The Tcl-controlled SIMMOL program reads in atomic coordinates in the PDB format from which it generates typical or user-defined parameters for the chemical shift, J coupling, quadrupolar coupling, and dipolar coupling tensors. The output is a spin system file for numerical simulations, e.g., using SIMPSON (Bak, Rasmussen, and Nielsen, J. Magn. Reson. 147, 296 (2000)), as well as a 3D visualization of the molecular structure, or selected parts of this, with user-controlled representation of relevant tensors, bonds, atoms, peptide planes, and coordinate systems. The combination of SIMPSON and SIMMOL allows straightforward simulation of the response of advanced solid-state NMR experiments on typical nuclear spin interactions present in polypeptides. Thus, SIMMOL may be considered a "sample changer" to the SIMPSON "computer spectrometer" and proves to be very useful for the design and optimization of pulse sequences for application on uniformly or extensively isotope-labeled peptides where multiple-spin interactions need to be considered. These aspects are demonstrated by optimization and simulation of novel DCP and C7 based 2D N(CO)CA, N(CA)CB, and N(CA)CX MAS correlation experiments for multiple-spin clusters in ubiquitin and by simulation of PISA wheels from PISEMA spectra of uniaxially oriented bacteriorhodopsin and rhodopsin under conditions of finite RF pulses and multiple spin interactions. PMID:11820824

Bak, Mads; Schultz, Robert; Vosegaard, Thomas; Nielsen, Niels Chr

2002-01-01

244

Arginine Dynamics in a Membrane-Bound Cationic Beta-Hairpin Peptide from Solid-State NMR  

PubMed Central

The site-specific motion of Arg residues in a membrane-bound disulfide-linked antimicrobial peptide, protegrin-1 (PG-1), is investigated using magic-angle spinning solid-state NMR, to better understand the membrane insertion and lipid interaction of this cationic membrane-disruptive peptide. C-H and N-H dipolar couplings and 13C chemical shift anisotropies were measured in the anionic POPE/POPG membrane and found to be reduced from the rigid-limit values by varying extents, indicating the presence of segmental motion. An Arg residue at the ?-turn region of the peptide shows much weaker spin interactions, indicating larger amplitudes of motion, than an Arg residue in the ?-strand region of the peptide. This is consistent with the exposure of the ?-turn to the membrane surface and the immersion of the ?-strand in the hydrophobic middle of the membrane, and supports the previously proposed oligomerization of the peptide into ?-barrels in the anionic membrane. 13C T2 and 1H T1? relaxation times indicate that the ?-turn backbone undergoes large-amplitude intermediate-timescale motion in the fluid phase of the membrane, causing significant line broadening and loss of spectral intensity. This study illustrates the strong correlation between the dynamics and the structure of membrane proteins and the capability of solid-state NMR spectroscopy for providing detailed information on site-specific dynamics in complex membrane protein assemblies. PMID:18442147

Tang, Ming; Waring, Alan J.; Hong, Mei

2010-01-01

245

Proton-detected scalar coupling based assignment strategies in MAS solid-state NMR spectroscopy applied to perdeuterated proteins  

NASA Astrophysics Data System (ADS)

Assignment of proteins in MAS (magic angle spinning) solid-state NMR relies so far on correlations among heteronuclei. This strategy is based on well dispersed resonances in the 15N dimension. In many complex cases like membrane proteins or amyloid fibrils, an additional frequency dimension is desirable in order to spread the amide resonances. We show here that proton detected HNCO, HNCA, and HNCACB type experiments can successfully be implemented in the solid-state. Coherences are sufficiently long lived to allow pulse schemes of a duration greater than 70 ms before incrementation of the first indirect dimension. The achieved resolution is comparable to the resolution obtained in solution-state NMR experiments. We demonstrate the experiments using a triply labeled sample of the SH3 domain of chicken ?-spectrin, which was re-crystallized in H 2O/D 2O using a ratio of 1/9. We employ paramagnetic relaxation enhancement (PRE) using EDTA chelated Cu II to enable rapid data acquisition.

Linser, Rasmus; Fink, Uwe; Reif, Bernd

2008-07-01

246

Optimization of an absolute sensitivity in a glassy matrix during DNP-enhanced multidimensional solid-state NMR experiments.  

PubMed

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. PMID:24480716

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

247

High-field solid-state (67)Zn NMR spectroscopy of several zinc-amino acid complexes.  

PubMed

We report the results of our solid-state (67)Zn NMR study of the various zinc sites in four zinc-amino acid coordination complexes: bis(glycinato)zinc(II) monohydrate; bis(l-alaninato)zinc(II); bis(l-histidinato)zinc(II) dihydrate; and sodium bis(l-cysteinato)zincate(II) hexahydrate; as well as a related complex, bis(imidazole)zinc(II) chloride. We demonstrate the advantages of using high (21.1 T) applied magnetic fields for detecting (67)Zn directly at ambient temperatures using the quadrupolar Carr-Purcell Meiboom-Gill (QCPMG) pulse sequence. The stepped-frequency technique was employed in cases where the central-transition (CT) (67)Zn NMR spectra were too broad to be uniformly excited. The parameters of the anisotropic zinc tensors were extracted by iterative simulations of the experimental spectra. In all cases, the quadrupolar interaction is found to dominate the central-transition (67)Zn NMR spectra; no convincing effects from chemical shift anisotropy (CSA) on the NMR spectra of the five complexes could be reliably detected at this field strength. Analyses of the experimental NMR spectra reveal that the (67)Zn quadrupolar coupling constants (C(Q)) range from 7.05 to 26.4 MHz, the isotropic chemical shifts (delta(iso)) range from 140 to 265 ppm, and the quadrupolar asymmetry parameters (eta(Q)) range from 0.20 to 0.95. The first report of the NMR spectral features of pentacoordinated zinc sites is included for two complexes. Quantum chemical calculations of the electric field gradient (EFG) and magnetic shielding tensors reproduced the experimental results to a reasonable extent. Moreover, the computationally determined orientations of both tensors permit correlations between NMR tensor properties and zinc local environments to be understood. PMID:19919076

Mroué, Kamal H; Power, William P

2010-01-14

248

Crystallinity and compositional changes in carbonated apatites: Evidence from {sup 31}P solid-state NMR, Raman, and AFM analysis  

SciTech Connect

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?}?{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 ?{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.

McElderry, John-David P.; Zhu, Peizhi [Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055 (United States); Mroue, Kamal H. [Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055 (United States); Department of Biophysics, University of Michigan, Ann Arbor, MI 48109-1055 (United States); Xu, Jiadi [Department of Biophysics, University of Michigan, Ann Arbor, MI 48109-1055 (United States); Pavan, Barbara [Department of Chemistry and Science of Advanced Materials Program, Central Michigan University, Mt. Pleasant, MI 48859 (United States); Fang, Ming [Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055 (United States); Zhao, Guisheng; McNerny, Erin; Kohn, David H.; Franceschi, Renny T. [School of Dentistry, University of Michigan, Ann Arbor, MI 48109-1055 (United States); Holl, Mark M.Banaszak [Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055 (United States); Tecklenburg, Mary M.J., E-mail: mary.tecklenburg@cmich.edu [Department of Chemistry and Science of Advanced Materials Program, Central Michigan University, Mt. Pleasant, MI 48859 (United States); Ramamoorthy, Ayyalusamy [Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055 (United States); Department of Biophysics, University of Michigan, Ann Arbor, MI 48109-1055 (United States); Morris, Michael D. [Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055 (United States)

2013-10-15

249

Simultaneous use of solution, solid-state NMR and X-ray crystallography to study the conformational landscape of the Crh protein during oligomerization and crystallization  

PubMed Central

We explore, using the Crh protein dimer as a model, how information from solution NMR, solid-state NMR and X-ray crystallography can be combined using structural bioinformatics methods, in order to get insights into the transition from solution to crystal. Using solid-state NMR chemical shifts, we filtered intra-monomer NMR distance restraints in order to keep only the restraints valid in the solid state. These filtered restraints were added to solid-state NMR restraints recorded on the dimer state to sample the conformational landscape explored during the oligomerization process. The use of non-crystallographic symmetries then permitted the extraction of converged conformers subsets. Ensembles of NMR and crystallographic conformers calculated independently display similar variability in monomer orientation, which supports a funnel shape for the conformational space explored during the solution-crystal transition. Insights into alternative conformations possibly sampled during oligomerization were obtained by analyzing the relative orientation of the two monomers, according to the restraint precision. Molecular dynamics simulations of Crh confirmed the tendencies observed in NMR conformers, as a paradoxical increase of the distance between the two ?1a strands, when the structure gets closer to the crystallographic structure, and the role of water bridges in this context. PMID:21918624

Bardiaux, Benjamin; Favier, Adrien; Etzkorn, Manuel; Baldus, Marc; Böckmann, Anja; Nilges, Michael; Malliavin, Thérèse E

2010-01-01

250

A spectrometer designed for 6.7 and 14.1 T DNP-enhanced solid-state MAS NMR using quasi-optical microwave transmission  

NASA Astrophysics Data System (ADS)

A Dynamic Nuclear Polarisation (DNP) enhanced solid-state Magic Angle Spinning (MAS) NMR spectrometer operating at 6.7 T is described and demonstrated. The 187 GHz TE13 fundamental mode of the FU CW VII gyrotron is used as the microwave source for this magnetic field strength and 284 MHz 1H DNP-NMR. The spectrometer is designed for use with microwave frequencies up to 395 GHz (the TE16 second-harmonic mode of the gyrotron) for DNP at 14.1 T (600 MHz 1H NMR). The pulsed microwave output from the gyrotron is converted to a quasi-optical Gaussian beam using a Vlasov antenna and transmitted to the NMR probe via an optical bench, with beam splitters for monitoring and adjusting the microwave power, a ferrite rotator to isolate the gyrotron from the reflected power and a Martin-Puplett interferometer for adjusting the polarisation. The Gaussian beam is reflected by curved mirrors inside the DNP-MAS-NMR probe to be incident at the sample along the MAS rotation axis. The beam is focussed to a ˜1 mm waist at the top of the rotor and then gradually diverges to give much more efficient coupling throughout the sample than designs using direct waveguide irradiation. The probe can be used in triple channel HXY mode for 600 MHz 1H and double channel HX mode for 284 MHz 1H, with MAS sample temperatures ?85 K. Initial data at 6.7 T and ˜1 W pulsed microwave power are presented with 13C enhancements of 60 for a frozen urea solution (1H-13C CP), 16 for bacteriorhodopsin in purple membrane (1H-13C CP) and 22 for 15N in a frozen glycine solution (1H-15N CP) being obtained. In comparison with designs which irradiate perpendicular to the rotation axis the approach used here provides a highly efficient use of the incident microwave beam and an NMR-optimised coil design.

Pike, Kevin J.; Kemp, Thomas F.; Takahashi, Hiroki; Day, Robert; Howes, Andrew P.; Kryukov, Eugeny V.; MacDonald, James F.; Collis, Alana E. C.; Bolton, David R.; Wylde, Richard J.; Orwick, Marcella; Kosuga, Kosuke; Clark, Andrew J.; Idehara, Toshitaka; Watts, Anthony; Smith, Graham M.; Newton, Mark E.; Dupree, Ray; Smith, Mark E.

2012-02-01

251

Characterisation of different polymorphs of tris(8-hydroxyquinolinato)aluminium(III) using solid-state NMR and DFT calculations  

PubMed Central

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 (?-phase) and the facial (?-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 ?-phase and the ?-phase, although the fluorescence emission shows no substantial difference between the ?-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 ?-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 ?-phase of Alq3 (containing meridional isomer) from the solid-state NMR studies. Solid-state NMR can hence be used as an effective complementary tool to XRD for characterisation and structural elucidation. PMID:19900275

Goswami, Mithun; Nayak, Pabitra K; Periasamy, N; Madhu, PK

2009-01-01

252

Solid-state NMR strategies for the structural characterization of paramagnetic NO adducts of Frustrated Lewis Pairs (FLPs).  

PubMed

By N,N addition of NO to the norbonane annulated borane-phosphane Frustrated Lewis pair (FLP) 1 a five-membered heterocyclic persistent aminoxyl radical 2 and its diamagnetic hydroxylamine reduction product 3 are prepared, and the comprehensive multinuclear solid state NMR characterization ((1)H, (11)B, (19)F, (31)P) of these FLP adducts is reported. Signal quantification experiments using a standard addition method reveal that the (11)B and (31)P NMR signals observed in 2 actually arise from molecular impurities of 3 embedded in the paramagnetic crystal. In contrast analogous quantification experiments reveal that the (1)H and (19)F MAS-NMR spectra originate from spin-carrying molecules. Peak assignments are based on DFT-calculated Mulliken spin densities, which lead to the surprising result that the largest paramagnetic shift affecting a proton NMR resonance in 2 originates from intermolecular interactions. For the (19)F nuclei, experiments and calculations indicate that paramagnetic shift effects are very small. In this case, assignments are based on DFT chemical shift calculations carried out on diamagnetic 3 and (19)F((11)B) Rotational Echo Adiabatic Passage DOuble Resonance (REAPDOR) experiments. The set of experiments described here defines an efficient strategy for the structural analysis of paramagnetic FLP adducts. PMID:24815176

Wiegand, Thomas; Sajid, Muhammad; Kehr, Gerald; Erker, Gerhard; Eckert, Hellmut

2014-01-01

253

Investigations of the structure and "interfacial" surface chemistry of Bioglass (RTM) materials by solid-state multinuclear NMR spectroscopy  

NASA Astrophysics Data System (ADS)

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 formation of surface silica species and follow the formation of phosphate species, respectively, while cross-polarization magic-angle spinning (CP/MAS) 29Si and 31P NMR have provided information about low intensity NMR peaks due to various silicon- and phosphorus-species present in the vicinity of associated protons on the surface of in vitro reacted BioglassRTM materials. The solid-state NMR investigations of the "interfacial" surface reactions of BioglassRTM materials are discussed in the context of the structure of these materials and the influence of this structure on the kinetics and the mechanism of their "interfacial" surface chemistry. (Abstract shortened by UMI.) BioglassRTM, trademark, University of Florida, Gainesville, FL, 32611.

Sarkar, Gautam

254

Understanding API-polymer proximities in amorphous stabilized composite drug products using fluorine-carbon 2D HETCOR solid-state NMR.  

PubMed

A simple and robust method for obtaining fluorine-carbon proximities was established using a (19)F-(13)C heteronuclear correlation (HETCOR) two-dimensional (2D) solid-state nuclear magnetic resonance (ssNMR) experiment under magic-angle spinning (MAS). The method was applied to study a crystalline active pharmaceutical ingredient (API), avagacestat, containing two types of fluorine atoms and its API-polymer composite drug product. These results provide insight into the molecular structure, aid with assigning the carbon resonances, and probe API-polymer proximities in amorphous spray dried dispersions (SDD). This method has an advantage over the commonly used (1)H-(13)C HETCOR because of the large chemical shift dispersion in the fluorine dimension. In the present study, fluorine-carbon distances up to 8 Å were probed, giving insight into the API structure, crystal packing, and assignments. Most importantly, the study demonstrates a method for probing an intimate molecular level contact between an amorphous API and a polymer in an SDD, giving insights into molecular association and understanding of the role of the polymer in API stability (such as recrystallization, degradation, etc.) in such novel composite drug products. PMID:25152063

Abraham, Anuji; Crull, George

2014-10-01

255

High-resolution high-frequency dynamic nuclear polarization for biomolecular solid state NMR  

E-print Network

Dynamic Nuclear Polarization (DNP) has exploded in popularity over the last few years, finally realizing its potential to overcome the detrimental lack of sensitivity that has plagued performing NMR experiments. Applied ...

Barnes, Alexander B. (Alexander Benjamin)

2011-01-01

256

The use of 13C labeling to enhance the sensitivity of 13C solid-state CPMAS NMR to study polymorphism in low dose solid formulations.  

PubMed

(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. PMID:15614820

Booy, Kees-Jan; Wiegerinck, Peter; Vader, Jan; Kaspersen, Frans; Lambregts, Dorette; Vromans, Herman; Kellenbach, Edwin

2005-02-01

257

Probing solid-state nanopores with light for the detection of unlabeled analytes.  

PubMed

Nanopore sensing has enabled label-free single-molecule measurements on a wide variety of analytes, including DNA, RNA, and protein complexes. Much progress has been made toward biotechnological applications; however, electrically probing the ion current introduces nonideal noise components. Here we further develop a method to couple an ionic current to a photon-by-photon counting of fluorescent signal from Ca(2+)-sensitive dyes and demonstrate label-free optical detection of biopolymer translocation through solid-state nanopores using TIRF and confocal microscopy. We show that by fine adjustment of the CaCl2 gradient, EGTA concentration, and voltage, the optical signals can be localized to the immediate vicinity of the pore. Consequently, the noise spectral density distribution in the optical signal exhibits a nearly flat distribution throughout the entire frequency range. With the use of high-speed photon counting devices in confocal microscopy and higher photon count rates using stronger light sources, we can improve the signal-to-noise ratio of signal acquisition, while the use of wide-field imaging in TIRF can allow for simultaneous quantitative imaging of large arrays of nanopores. PMID:25363680

Anderson, Brett N; Assad, Ossama N; Gilboa, Tal; Squires, Allison H; Bar, Daniel; Meller, Amit

2014-11-25

258

Humic acids as proxies for assessing different Mediterranean forest soils signatures using solid-state CPMAS 13C NMR spectroscopy.  

PubMed

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. PMID:23332874

Duarte, Regina M B O; Fernández-Getino, Ana P; Duarte, Armando C

2013-06-01

259

Acceleration of natural-abundance solid-state MAS NMR measurements on bone by paramagnetic relaxation from gadolinium-DTPA  

NASA Astrophysics Data System (ADS)

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.

Mroue, Kamal H.; Zhang, Rongchun; Zhu, Peizhi; McNerny, Erin; Kohn, David H.; Morris, Michael D.; Ramamoorthy, Ayyalusamy

2014-07-01

260

A multinuclear solid state NMR spectroscopic study of the structural evolution of disordered calcium silicate sol-gel biomaterials.  

PubMed

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. PMID:25494341

Lin, Zhongjie; Jones, Julian R; Hanna, John V; Smith, Mark E

2015-01-28

261

Solid-state (63)Cu and (65)Cu NMR spectroscopy of inorganic and organometallic copper(I) complexes.  

PubMed

Solid-state 63Cu and 65Cu NMR experiments have been conducted on a series of inorganic and organometallic copper(I) complexes possessing a variety of spherically asymmetric two-, three-, and four-coordinate Cu coordination environments. Variations in structure and symmetry, and corresponding changes in the electric field gradient (EFG) tensors, yield 63/65Cu quadrupolar coupling constants (CQ) ranging from 22.0 to 71.0 MHz for spherically asymmetric Cu sites. These large quadrupolar interactions result in spectra featuring quadrupolar-dominated central transition patterns with breadths ranging from 760 kHz to 6.7 MHz. Accordingly, Hahn-echo and/or QCPMG pulse sequences were applied in a frequency-stepped manner to rapidly acquire high S/N powder patterns. Significant copper chemical shielding anisotropies (CSAs) are also observed in some cases, ranging from 1000 to 1500 ppm. 31P CP/MAS NMR spectra for complexes featuring 63/65Cu-31P spin pairs exhibit residual dipolar coupling and are simulated to determine both the sign of CQ and the EFG tensor orientations relative to the Cu-P bond axes. X-ray crystallographic data and theoretical (Hartree-Fock and density functional theory) calculations of 63/65Cu EFG and CS tensors are utilized to examine the relationships between NMR interaction tensor parameters, the magnitudes and orientations of the principal components, and molecular structure and symmetry. PMID:17924623

Tang, Joel A; Ellis, Bobby D; Warren, Timothy H; Hanna, John V; Macdonald, Charles L B; Schurko, Robert W

2007-10-31

262

Hydration properties of regioselectively etherified celluloses monitored by 2H and 13C solid-state MAS NMR spectroscopy.  

PubMed

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. PMID:24750769

Larsen, Flemming H; Schöbitz, Michael; Schaller, Jens

2012-06-20

263

Investigating miscibility and molecular mobility of nifedipine-PVP amorphous solid dispersions using solid-state NMR spectroscopy.  

PubMed

Solid-state NMR (SSNMR) (1)H T1 and T1? 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 T1? 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 T1? values. Variable-temperature SSNMR (1)H T1? relaxation measurements revealed a change in relaxation time at approximately 20 °C below Tg, suggesting increased molecular mobility above that temperature. PMID:24256090

Yuan, Xiaoda; Sperger, Diana; Munson, Eric J

2014-01-01

264

Molecular composition of recycled organic wastes, as determined by solid-state {sup 13}C NMR and elemental analyses  

SciTech Connect

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.

Eldridge, S.M., E-mail: simon.eldridge@dpi.nsw.gov.au [Environmental Futures Centre, School of Environment, Griffith University, Nathan, QLD 4111 (Australia); NSW Department of Primary Industries, Bruxner Highway, Wollongbar, NSW 2477 (Australia); Chen, C.R. [Environmental Futures Centre, School of Environment, Griffith University, Nathan, QLD 4111 (Australia); Xu, Z.H. [Environmental Futures Centre, School of Biomolecular and Physical Sciences, Griffith University, Nathan, QLD 4111 (Australia); Nelson, P.N. [School of Earth and Environmental Sciences, James Cook University, Cairns, QLD 4870 (Australia); Boyd, S.E. [Environmental Futures Centre, School of Biomolecular and Physical Sciences, Griffith University, Nathan, QLD 4111 (Australia); Meszaros, I. [Formerly NSW Department of Primary Industries, Richmond, NSW 2753 (Australia); Chan, K.Y. [Graduate School of Environment, Macquarie University, North Ryde, NSW 2109 (Australia); Formerly NSW Department of Primary Industries, Richmond, NSW 2753 (Australia)

2013-11-15

265

Synthesis and evaluation of nitroxide-based oligoradicals for low-temperature dynamic nuclear polarization in solid state NMR.  

PubMed

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. PMID:24887201

Yau, Wai-Ming; Thurber, Kent R; Tycko, Robert

2014-07-01

266

An experimental and theoretical NMR study of NH-benzimidazoles in solution and in the solid state: proton transfer and tautomerism  

PubMed Central

Summary This paper reports the 1H, 13C and 15N NMR experimental study of five benzimidazoles in solution and in the solid state (13C and 15N CPMAS NMR) as well as the theoretically calculated (GIAO/DFT) chemical shifts. We have assigned unambiguously the "tautomeric positions" (C3a/C7a, C4/C7 and C5/C6) of NH-benzimidazoles that, in some solvents and in the solid state, appear different (blocked tautomerism). In the case of 1H-benzimidazole itself we have measured the prototropic rate in HMPA-d 18. PMID:25161719

Nieto, Carla I; Cabildo, Pilar; García, M Ángeles; Elguero, José

2014-01-01

267

Recoupling of chemical shift anisotropies in solid-state NMR under high-speed magic-angle spinning and in uniformly 13C-labeled systems  

NASA Astrophysics Data System (ADS)

We demonstrate the possibility of recoupling chemical shift anisotropy (CSA) interactions in solid-state nuclear magnetic resonance (NMR) under high-speed magic-angle spinning (MAS) while retaining a static CSA powder pattern line shape and simultaneously attenuating homonuclear dipole-dipole interactions. CSA recoupling is accomplished by a rotation-synchronized radio-frequency pulse sequence with symmetry properties that permit static CSA line shapes to be obtained. We suggest a specific recoupling sequence, which we call ROCSA, for which the scaling factors for CSA and homonuclear dipole-dipole interactions are 0.272 and approximately 0.05, respectively. This sequence is suitable for high-speed 13C MAS NMR experiments on uniformly 13C-labeled organic compounds, including biopolymers. We demonstrate the ROCSA sequence experimentally by measuring the 13C CSA patterns of the uniformly labeled, polycrystalline compounds L-alanine and N-acetyl-D,L-valine at MAS frequencies of 11 and 20 kHz. We also present experimental data for amyloid fibrils formed by a 15-residue fragment of the ?-amyloid peptide associated with Alzheimer's disease, in which four amino acid residues are uniformly labeled, demonstrating the applicability to biochemical systems of high molecular weight and significant complexity. Analysis of the CSA patterns in the amyloid fibril sample demonstrates the utility of ROCSA measurements as probes of peptide and protein conformation in noncrystalline solids.

Chan, Jerry C. C.; Tycko, Robert

2003-05-01

268

Hydration properties and phosphorous speciation in native, gelatinized and enzymatically modified potato starch analyzed by solid-state MAS NMR.  

PubMed

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 ?-amylase (BB) catalyzed exo-hydrolysis. Carbons of the glycosidic ?-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. PMID:23911477

Larsen, Flemming H; Kasprzak, Miros?aw M; Lærke, Helle N; Knudsen, Knud Erik B; Pedersen, Sven; Jørgensen, Anne S; Blennow, Andreas

2013-09-12

269

A simple method for analyzing 51V solid-state NMR spectra of complex systems.  

PubMed

Five vanadium complexes as models for biological systems were investigated using (51)V-MAS-NMR spectroscopy. All spectra show an uncommon line shape, which can be attributed to a shorter relaxation time of the satellite transition in contrast to the central one. A method for the reliable analysis of such kind of spectra is presented for the first time and the most important NMR parameters of the investigated complexes (quadrupolar coupling constant C(Q), asymmetry of the EFG tensor ?(Q), isotropic chemical shift ?(iso), chemical shift anisotropy ?(?) and asymmetry of the CSA tensor ?(?)) are presented. These results are of particular importance with respect to the analysis of the (51)V-MAS-NMR spectra of vanadium moieties in biological matrices such as vanadium chloroperoxidase, which show hitherto unexplained low intensity of the satellite sideband pattern. PMID:21601435

Fenn, Annika; Wächtler, Maria; Breitzke, Hergen; Buchholz, Axel; Lippold, Ines; Plass, Winfried; Buntkowsky, Gerd

2011-09-01

270

Unambiguous assignment of short- and long-range structural restraints by solid-state NMR spectroscopy with segmental isotope labeling.  

PubMed

We present an efficient method for the reduction of spectral complexity in the solid-state NMR spectra of insoluble protein assemblies, without loss of signal intensity. The approach is based on segmental isotope labeling by using the split intein DnaE from Nostoc punctiforme. We show that the segmentally (13) C,(15) N-labeled prion domain of HET-s exhibits significantly reduced spectral overlap while retaining the wild-type structure and spectral quality. A large number of unambiguous distance restraints were thus collected from a single two-dimensional (13) C,(13) C cross-correlation spectrum. The observed resonances could be unambiguously identified as intramolecular without the need for preparing a dilute, less sensitive sample. PMID:25394265

Schubeis, Tobias; Lührs, Thorsten; Ritter, Christiane

2015-01-01

271

Detection of drug active ingredients by chemometric processing of solid-state NMR spectrometry data -- the case of acetaminophen.  

PubMed

This paper presents a preliminary study in building discriminant models from solid-state NMR spectrometry data to detect the presence of acetaminophen in over-the-counter pharmaceutical formulations. The dataset, containing 11 spectra of pure substances and 21 spectra of various formulations, was processed by partial least squares discriminant analysis (PLS-DA). The model found coped with the discrimination, and its quality parameters were acceptable. It was found that standard normal variate preprocessing had almost no influence on unsupervised investigation of the dataset. The influence of variable selection with the uninformative variable elimination by PLS method was studied, reducing the dataset from 7601 variables to around 300 informative variables, but not improving the model performance. The results showed the possibility to construct well-working PLS-DA models from such small datasets without a full experimental design. PMID:22816260

Paradowska, Katarzyna; Jamróz, Marta Katarzyna; Koby?ka, Mariola; Gowin, Ewelina; Maczka, Paulina; Skibi?ski, Robert; Komsta, ?ukasz

2012-01-01

272

Solid-State NMR Studies of Fossil Fuels using One- and Two-Dimensional Methods at High Magnetic Field  

SciTech Connect

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.

Althaus, Stacey M.; Mao, Kanmi; Kennedy, Gordon J.; Pruski, Marek

2012-06-24

273

Solid state (13)C NMR and FT-IR spectroscopy of the cocoon silk of two common spiders.  

PubMed

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 (13)C 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 beta-sheet structures, whereas that of Araneus diadematus shows a more complex structure, containing also beta-strands and beta-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. PMID:16257700

Bramanti, Emilia; Catalano, Donata; Forte, Claudia; Giovanneschi, Mario; Masetti, Massimo; Veracini, Carlo Alberto

2005-11-01

274

Rapid and accurate determination of the lignin content of lignocellulosic biomass by solid-state NMR.  

PubMed

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. PMID:25404762

Fu, Li; McCallum, Scott A; Miao, Jianjun; Hart, Courtney; Tudryn, Gregory J; Zhang, Fuming; Linhardt, Robert J

2015-02-01

275

Solid-state NMR studies of the adsorption of acetylene on platinum/alumina catalysts  

E-print Network

/y-alumina and subsequently evacuated. 25 "C Bloch Decay/MAS NMR spectra of cyclohexane adsorbed onto 10%Pt/y-alumina. 27 FT mass spectra taken at a field strength of 3-Tesla. 28 CAVERN uC CP/MAS NMR spectra of an overpressure of acetylene on 10%Pt/y-alumina adsorbed... pumped two-section ion cell, an Extrel 2001 data system, and a 3-Tesla Oxford superconducting magnet. ~~ Samples were introduced into the cell by a variable leak valve (at sample pressure of 4 x 10' torr). Ionization was performed by electron impact...

Lambregts, Marsha Jo Lupher

2012-06-07

276

Solid-state variable-temperature NMR study of the phase separation of polybutadiene polyurethane zwitterionomers  

NASA Astrophysics Data System (ADS)

Polybutadiene polyurethane (PBDPU) zwitterionomers based on 4,4'-diphenylmethane diisocyanate (MDI), methyl-diethanolamine (MDEA), and hydroxy terminated polybutadiene are studied with variable-temperature (VT) wide-line 1H NMR. Spin—spin relaxation times ( T2) and spin—lattice relaxation times ( T1) are measured. It is found that phase separation of PBDPU does not change significantly upon ionization. The initial incorporation of ionization groups destroys the crystallinity of the hard segment while further ionization enhances physical crosslinks in the hard phase. The results are compared with a previous VT NMR study on polyether polyurethane zwitterionomers based on MDI, MDEA and 1000 Da molecular weight polytetramethylene oxide.

Yang, G.; Chen, Q.; Wang, Y.; Yang, C.; Wu, X.

1994-07-01

277

Characterizing the Secondary Protein Structure of Black Widow Dragline Silk Using Solid-State NMR & X-ray Diffraction  

PubMed Central

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 ?-sheet nanocrystallites oriented parallel to the fiber axis and an amorphous region with oriented (anisotropic) and isotropic components. The combination of two-dimensional (2D) 13C-13C through-space and through-bond solid-state NMR experiments provide chemical shifts that are used to determine detailed information about 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 ?-sheet (poly(Alan) and poly(Gly-Ala)), 31-helix (poly(Gly-Gly-Xaa), and ?-helix (poly(Gln-Gln-Ala-Tyr)) components. Glycine is determined to be in ?-sheet (poly(Gly-Ala)) and 31-helical (poly(Gly-Gly-Xaa)) regions, while serine is present in ?-sheet (poly(Gly-Ala-Ser)), 31-helix (poly(Gly-Gly-Ser)), and ?-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. PMID:24024617

Jenkins, Janelle E.; Sampath, Sujatha; Butler, Emily; Kim, Jihyun; Henning, Robert W.; Holland, Gregory P.; Yarger, Jeffery L.

2013-01-01

278

Characterizing the secondary protein structure of black widow dragline silk using solid-state NMR and X-ray diffraction.  

PubMed

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 ?-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 ?-sheet (poly(Alan) and poly(Gly-Ala)), 3(1)-helix (poly(Gly-Gly-Xaa), and ?-helix (poly(Gln-Gln-Ala-Tyr)) components. Glycine is determined to be in ?-sheet (poly(Gly-Ala)) and 3(1)-helical (poly(Gly-Gly-X(aa))) regions, while serine is present in ?-sheet (poly(Gly-Ala-Ser)), 3(1)-helix (poly(Gly-Gly-Ser)), and ?-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. PMID:24024617

Jenkins, Janelle E; Sampath, Sujatha; Butler, Emily; Kim, Jihyun; Henning, Robert W; Holland, Gregory P; Yarger, Jeffery L

2013-10-14

279

New stannide ScAgSn: determination of the superstructure via two-dimensional 45Sc solid state NMR.  

PubMed

The new stannide ScAgSn was synthesized by induction melting of the elements in a sealed tantalum tube and subsequent annealing. ScAgSn crystallizes with a pronounced subcell structure: ZrNiAl type, P2m, a = 708.2(2) pm, c = 433.9(1) pm, wR2 = 0.1264, 321 F2 values, and 14 variables. The Guinier powder pattern reveals weak superstructure reflections pointing to a TiFeSi-type structural arrangement: I2cm, a = 708.1(1) pm, b = 1225.2(2) pm, c = 869.9(1) pm, wR2 = 0.0787, 5556 F2 values, and 49 variables. So far the growth of high-quality single crystals failed. Determination of the superstructure was partly based on merohedral triplet X-ray data augmented by 119Sn Mössbauer spectroscopy and 119Sn and 45Sc solid-state NMR data. In particular, the observation of three crystallographically inequivalent sites in 45Sc NMR triple quantum magic-angle spinning (TQ-MAS) NMR spectra provided unambiguous proof of the superstructure proposed. The ScAgSn structure consists of a three-dimensional [AgSn] network (with Ag-Sn distances between 273 and 280 pm) in which the scandium atoms are located in distorted hexagonal channels, each having five tin and two silver nearest neighbors. Both crystallographically independent tin sites have a tricapped trigonal prismatic coordination, that is, [Sn1Sc6Ag3] and [Sn2Ag6Sc3] environments, which are well distinguished in the 119Sn NMR and Mössbauer spectra because of their different site symmetries. PMID:17257019

Sebastian, C Peter; Zhang, Long; Fehse, Constanze; Hoffmann, Rolf-Dieter; Eckert, Hellmut; Pöttgen, Rainer

2007-02-01

280

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

SciTech Connect

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.

Kobayashi, Takeshi [Ames Laboratory; Gupta, Shalabh [Ames Laboratory; Caporini, Marc A [Bruker BioSpin Corporation; Pecharsky, Vitalij K [Ames Laboratory; Pruski, Marek [Ames Laboratory

2014-08-28

281

13C-NMR study of 4-azasteroids in solution and solid state  

Microsoft Academic Search

A group of biologically active 4-azasteroids was studied by 13C-NMR spectroscopy in solution and in the solid phase. A full assignment of signals in the spectra of samples in chloroform was performed for thirteen 4-azasteroids using two-dimensional techniques. Substituent and steric effects of a nitrogen atom, and their influence on chemical shifts of the neighboring carbon atoms are discussed. CP

Jacek W. Morzycki; Iwona Wawer; Agnieszka Gryszkiewicz; Jadwiga Maj; Leszek Siergiejczyk; Alicja Zaworska

2002-01-01

282

Solid state NMR study of dietary fiber powders from aronia, bilberry, black currant and apple  

Microsoft Academic Search

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 T1?H partially relaxed spectra enabled the identification of several constituents: microcrystalline cellulose, pectins, lignins, cutin-like polymers and condensed tannins. The fiber powders

I. Wawer; M. Wolniak; K. Paradowska

2006-01-01

283

Multidimensional Dipolar Exchange-Assisted Recoupling Measurements in Solid-State NMR  

Microsoft Academic Search

Aseries of uni- and multidimensional variants of the dipolar exchange-assisted recoupling (DEAR) NMR experiment is described and applied to determinations of 13C–14N dipolar local field spectra in amino acids and dipeptides. The DEAR protocol recouples nearby nuclei by relying on differences in their relative rates of longitudinal relaxation, and has the potential to give quantitative geometric results without requiring radiofrequency

Joseph R. Sachleben; Peter Beverwyk; Lucio Frydman

2000-01-01

284

Solid state 13C-NMR spectroscopy and XRD studies of commercial and pyrolytic carbon blacks  

Microsoft Academic Search

The bulk chemistry of commercial carbon blacks and carbon blacks obtained by vacuum pyrolysis (CBP) of used tires was investigated by 13C-NMR spectroscopy with and without magic angle spinning of the sample. Two different kinds of carbon atoms can be distinguished: Graphite like carbon atoms in poly-condensed aromatic rings and carbon atoms in a less ordered environment. Commercial carbon blacks

Hans Darmstadt; Christian Roy; Serge Kaliaguine; Guoying Xu; Michèle Auger; Alain Tuel; Veda Ramaswamy

2000-01-01

285

Tracking Stable Isotope Enrichment in Tree Seedlings with Solid-State NMR Spectroscopy  

PubMed Central

Enriching plant tissues with 13C and 15N isotopes has provided long-lasting, non-reactive tracers to quantify rates of terrestrial elemental fluxes (e.g., soil organic matter decomposition). However, the molecular location and level of isotope enrichment may differ among plant tissues. This factor is central to the integrity and interpretation of tracer data, but is seldom considered in experiments. We propose a rapid, non-destructive method to quantify molecular isotope allocation using solid-state 13C and 15N nuclear magnetic resonance spectroscopy. With this method, we tracked and quantified the fate of multiple pulses of 13CO2(g) and K 15NO3(l) in boreal tree seedling roots and leaves as a function of time. Results show that initial preferential 13C carbohydrate enrichment in the leaves was followed by redistribution to more complex compounds after seven days. While 13C allocation within the roots was uniform across molecules, 15N results indicate an initial enrichment of amine molecules after two hours. PMID:23056911

Norris, Charlotte E.; Quideau, Sylvie A.; Landhäusser, Simon M.; Bernard, Guy M.; Wasylishen, Roderick E.

2012-01-01

286

High-temperature steam-treatment of PBI, PEEK, and PEKK polymers with H2O and D2O: A solid-state NMR study  

E-print Network

-state NMR study Jacqueline C. Pope a , Hung-Jue Sue b , Tim Bremner b, c, ** , Janet Blümel a 2014 Keywords: Steam-treatment of PBI, PEEK, PEKK Solid-state NMR Water and D2O uptake polymers a b with D2O steam at temperatures of 150 and 315 C. All samples are studied by TGA, IR, 13 C CP/MAS, 1 H

Bluemel, Janet

287

A Solid-State NMR Study of Tungsten Methyl Group Dynamics in [W(5-C5Me5)Me4][PF6  

E-print Network

A Solid-State NMR Study of Tungsten Methyl Group Dynamics in [W(5-C5Me5)Me4][PF6] Douglas C. Maus Spinning (MAS) 13C and static 2H NMR studies of the dynamics of the methyl groups coordinated to tungsten in [WCp*Me4][PF6] (Cp* ) 5-C5Me5). The temperature-dependent broadening of the axial methyl 13C line can

Griffin, Robert G.

288

Source indicators of humic substances: an elemental composition, solid state 13C CP\\/MAS NMR and Py-GC\\/MS Study  

Microsoft Academic Search

Humic substances (HS) isolated from swamp water, surface soil, peat and brown coal were characterized using elemental composition, solid state 13C CP\\/MAS NMR and Py-GC\\/MS analysis. A substantial amount of information with regard to the source, maturity, depositional environment and degree of degradation of humic substances was obtained. The elemental composition, atomic ratio, 13C NMR spectra and Py-GC\\/MS results indicated

X. Q Lu; J. V Hanna; W. D Johnson

2000-01-01

289

Comparing quantum-chemical calculation methods for structural investigation of zeolite crystal structures by solid-state NMR spectroscopy.  

PubMed

Combining quantum-chemical calculations and ultrahigh-field NMR measurements of (29)Si chemical shielding (CS) tensors has provided a powerful approach for probing the fine details of zeolite crystal structures. In previous work, the quantum-chemical calculations have been performed on 'molecular fragments' extracted from the zeolite crystal structure using Hartree-Fock methods (as implemented in Gaussian). Using recently acquired ultrahigh-field (29) Si NMR data for the pure silica zeolite ITQ-4, we report the results of calculations using recently developed quantum-chemical calculation methods for periodic crystalline solids (as implemented in CAmbridge Serial Total Energy Package (CASTEP) and compare these calculations to those calculated with Gaussian. Furthermore, in the context of NMR crystallography of zeolites, we report the completion of the NMR crystallography of the zeolite ITQ-4, which was previously solved from NMR data. We compare three options for the 'refinement' of zeolite crystal structures from 'NMR-solved' structures: (i) a simple target-distance based geometry optimization, (ii) refinement of atomic coordinates in which the differences between experimental and calculated (29)Si CS tensors are minimized, and (iii) refinement of atomic coordinates to minimize the total energy of the lattice using CASTEP quantum-chemical calculations. All three refinement approaches give structures that are in remarkably good agreement with the single-crystal X-ray diffraction structure of ITQ-4. PMID:20623826

Brouwer, Darren H; Moudrakovski, Igor L; Darton, Richard J; Morris, Russell E

2010-12-01

290

Solid state NMR study and density functional theory (DFT) calculations of structure and dynamics of poly(p-xylylenes).  

PubMed

High resolution solid state (13)C nuclear magnetic resonance (SS NMR) measurements were carried out on poly(p-xylylene) (PPX). The samples comprised vapor-deposited specimens as well as pure alpha and beta polymorphs of this polymer. The measurements were performed using cross-polarization and magic angle spinning (CP/MAS) techniques. Density functional theory gauge-including-atomic-orbital (DFT GIAO) calculations of NMR shielding parameters (13)C sigma(ii) were performed for the optimized geometry and structure of a xylylene trimer, acquired from the X-ray data, including intermolecular interactions. Two-dimensional phase adjusted spinning sideband (2D PASS) correlation was employed for the assignment of the values of the principal elements (13)C delta(ii) of the chemical shift tensor (CST). A comparative analysis of shielding (sigma(ii)) versus chemical shift (delta(ii)) parameters showed substantial differences between the molecular dynamics of alpha and beta polymorphs. This observation was further supported by the measurements of (13)C T(1) relaxation times and the analysis of cross-polarization kinetics. Frequency switched Lee-Goldburg heteronuclear correlation (FSLG HETCOR) for the (1)H-(13)C system was used in order to analyze molecular packing in both polymorphs. As a result of all of the above measurements, new insight into the mechanism of thermal phase transition from the alpha to the beta polymorph of poly(p-xylylene) is presented. PMID:19331396

Sroka-Bartnicka, A; Olejniczak, S; Ciesielski, W; Nosal, A; Szymanowski, H; Gazicki-Lipman, M; Potrzebowski, M J

2009-04-23

291

Solid-state NMR sequential assignments of the amyloid core of full-length Sup35p.  

PubMed

Sup35p is a yeast prion and is responsible for the [PSI(+)] trait in Saccharomyces cerevisiae. With 685 amino acids, full-length soluble and fibrillar Sup35p are challenging targets for structural biology as they cannot be investigated by X-ray crystallography or NMR in solution. We present solid-state NMR studies of fibrils formed by the full-length Sup35 protein. We detect an ordered and rigid core of the protein that gives rise to narrow and strong peaks, while large parts of the protein show either static disorder or dynamics on time scales which interfere with dipolar polarization transfer or shorten the coherence lifetime. Thus, only a small subset of resonances is observed in 3D spectra. Here we describe in detail the sequential assignments of the 22 residues for which resonances are observed in 3D spectra: their chemical shifts mostly corresponding to ?-sheet secondary structure. We suspect that these residues form the amyloid core of the fibril. PMID:23943018

Schütz, Anne K; Habenstein, Birgit; Luckgei, Nina; Bousset, Luc; Sourigues, Yannick; Nielsen, Anders B; Melki, Ronald; Böckmann, Anja; Meier, Beat H

2014-10-01

292

Vanadium(V) environments in bismuth vanadates: A structural investigation using Raman spectroscopy and solid state 51V NMR  

NASA Astrophysics Data System (ADS)

The Bi 2O 3?V 2O 5 system was examined using Raman spectroscopy and solid state 51V wideline, magic-angle spinning (MAS), and nutation NMR spectroscopy. The methods are shown to be complementary in the identification of the various phases and in the characterization of their vanadium site symmetries. Most of the compositions examined (1:1 ? Bi:V ? 60:1) are multiphasic. Depending on the Bi:V ratio, the following phases have been identified: BiVO 4, Bi 4V 2O 11, a triclinic type-II phase, a cubic type-I phase, ?-Bi 2O 3 doped with V(V) (sillenite), and ?-Bi 2O 3. Detailed spectroscopic characterization reveals that vanadium is tetrahedrally coordinated in all these compounds, and that the degree of symmetry increases with increasing Bi:V ratio. At the highest Bi:V ratios, the combined interpretation of the Raman and NMR data provides strong evidence for the presence of Bi 5+O 4 tetrahedra.

Hardcastle, Franklin D.; Wachs, Israel E.; Eckert, Hellmut; Jefferson, David A.

1991-02-01

293

Application of Solid-State 13C NMR Spectroscopy and Dipolar Dephasing Technique to Determine the Extent of Condensation in Technical Lignins  

Microsoft Academic Search

Solid-state 13C NMR spectroscopy and dipolar dephasing technique was used to determine the extent of condensation in various technical lignins. The accuracy of dipolar dephasing method was first investigated with the aid of some lignin model compounds and two various methods to determine the degree of condensation were compared. On the basis of the model compound experiments both methods based

T. Liitiä; S. L. Maunu; J. Sipilä; B. Hortling

2002-01-01

294

Fine hierarchy of the V-O bonds by advanced solid state NMR: novel Pb4(VO2)(PO4)3 structure as a textbook case.  

PubMed

We report here a complete structural characterization of a new lead Pb(4)(VO(2))(PO(4))(3) vanadophosphate compound by single crystal X-ray diffraction and (51)V and (31)P solid-state NMR spectroscopy. Although structural data are commonly used for the estimation of bond lengths and further delimitation of the true coordination number (e.g., octahedral: 6 versus 5 + 1 versus 4 + 2), we show here for the first time by solid-state NMR a more accurate appreciation of the V-O bonding scheme in this complex oxide which appears well adapted to the full series of vanado-phosphate materials. The direct characterization of V-O-P bridges through the J-mediated correlation (51)V{(31)P} heteronuclear multiple quantum coherence (J-HMQC) technique allows a contrasted hierarchy of the V-O electronic delocalization and indirectly supports the presence or not of the V-O bond. In the reported lead vanado-phosphate structure, the two vanadium polyhedra that have been assigned to octahedra from a bond length point of view have been finally reclassified as tetra- and penta-coordinated units on the basis of the solid-state NMR results. More generally, we believe that the improved characterization of interatomic bonds in various vanado-phosphate structures by solid-state NMR will contribute to a better understanding of the structure/property relationships in this important class of materials. PMID:23190003

Tricot, Grégory; Mentré, Olivier; Cristol, Sylvain; Delevoye, Laurent

2012-12-17

295

Solid state 13 C CP MAS NMR characterization of the chemical structure of terrestrial organic matter from areas with differing vegetational backgrounds  

Microsoft Academic Search

Twelve samples of terrestrial organic matter from areas of different vegetational background were selected for study. The samples were examined with solid state 13C NMR using Cross Polarisation and Magic Angle Spinning (CP MAS). The examination was done on whole soil samples, because isolation and separation of humic substances may alter the chemical structure of the organic matter. The soil

Marit Krosshavn; Jon Björgum; Timothy E. Southon; Eiliv Steinnes

296

The study of a monocotyledon abscission zone using microscopic, chemical, enzymatic and solid state 13C CP\\/MAS NMR analyses  

Microsoft Academic Search

We have investigated distinguishing features in cells of the abscission zone of a monocotyledon fruit, the oil palm Elaeis guineensis. The cell walls of the abscission zone and the subtending mesocarp and pedicel have been analysed by light and transmission electron microscopy, by chemical methods and by solid state 13C CP\\/MAS NMR spectroscopy. Results show that these abscission zone cells

Janice Henderson; Heather A. Davies; Stephen J. Heyes; Daphne J. Osborne

2001-01-01

297

Dynamic Structure of a Protein Hydrogel: A Solid-State NMR Study S. B. Kennedy, E. R. deAzevedo, W. A. Petka, and T. P. Russell  

E-print Network

Dynamic Structure of a Protein Hydrogel: A Solid-State NMR Study S. B. Kennedy, E. R. deAzevedo, W used to study the dynamic structure of a genetically engineered multidomain protein hydrogel CODEX experiment. The motion is rigid-body in nature with a correlation time of about 80 ms at room

Hong, Mei

298

Exploiting the Synergy of Powder X-ray Diffraction and Solid-State NMR Spectroscopy in Structure Determination of Organic Molecular Solids  

PubMed Central

We report a strategy for structure determination of organic materials in which complete solid-state nuclear magnetic resonance (NMR) spectral data is utilized within the context of structure determination from powder X-ray diffraction (XRD) data. Following determination of the crystal structure from powder XRD data, first-principles density functional theory-based techniques within the GIPAW approach are exploited to calculate the solid-state NMR data for the structure, followed by careful scrutiny of the agreement with experimental solid-state NMR data. The successful application of this approach is demonstrated by structure determination of the 1:1 cocrystal of indomethacin and nicotinamide. The 1H and 13C chemical shifts calculated for the crystal structure determined from the powder XRD data are in excellent agreement with those measured experimentally, notably including the two-dimensional correlation of 1H and 13C chemical shifts for directly bonded 13C–1H moieties. The key feature of this combined approach is that the quality of the structure determined is assessed both against experimental powder XRD data and against experimental solid-state NMR data, thus providing a very robust validation of the veracity of the structure. PMID:24386493

2013-01-01

299

Matrix-free dynamic nuclear polarization enables solid-state NMR 13C-13C correlation spectroscopy of proteins at natural isotopic abundance.  

PubMed

We introduce a general approach for dynamic nuclear polarization (DNP) enhanced solid-state NMR that overcomes the current problems in DNP experiments caused by the use of frozen solutions. Notably, we report for the first time a 2D (13)C-(13)C correlation spectrum of a protein without the use of isotopic labeling. PMID:24013616

Takahashi, Hiroki; Hediger, Sabine; De Paëpe, Gaël

2013-10-21

300

H Solid-State NMR Study of Lipid Clustering by Cationic Antimicrobial and Cell-Penetrating Peptides in Model Bacterial Membranes  

E-print Network

/POPG (3:1) membranes, and membranes containing one of four cationic peptides: two antimicrobial peptidesA 2 H Solid-State NMR Study of Lipid Clustering by Cationic Antimicrobial and Cell-Penetrating Peptides in Model Bacterial Membranes Byungsu Kwon, Alan J. Waring,§ and Mei Hong * Department

Hong, Mei

301

27Al and 29Si solid-state NMR characterization of calcium-aluminosilicate-hydrate.  

PubMed

Calcium silicate hydrate (C-S-H) is the main constituent of hydrated cement paste and determines its cohesive properties. Because of the environmental impact of cement industry, it is more and more common to replace a part of the clinker in cement by secondary cementitious materials (SCMs). These SCMs are generally alumina-rich and as a consequence some aluminum is incorporated into the C-S-H. This may have consequences on the cohesion and durability of the material, and it is thus of importance to know the amount and the location of Al in C-S-H and what the parameters are that control these features. The present paper reports the (29)Si and (27)Al MAS NMR analyses of well-characterized C-A-S-H samples (C-S-H containing Al). These samples were synthesized using an original procedure that successfully leads to pure C-A-S-H of controlled compositions in equilibrium with well-characterized solutions. The (27)Al MAS NMR spectra were quantitatively interpreted assuming a tobermorite-like structure for C-A-S-H to determine the aluminum location in this structure. For this purpose, an in-house written software was used which allows decomposing several spectra simultaneously using the same constrained spectral parameters for each resonance but with variable intensities. The hypothesis on the aluminum location in the C-A-S-H structure determines the proportion of each silicon site. Therefore, from the (27)Al NMR quantitative results and the chemical composition of each sample, the intensity of each resonance line in the (29)Si spectra was set. The agreement between the experimental and calculated (29)Si MAS NMR spectra corroborates the assumed C-A-S-H structure and the proposed Al incorporation mechanism. The consistency between the results obtained for all compositions provides another means to assess the assumptions on the C-A-S-H structure. It is found that Al substitutes Si mainly in bridging positions and moderately in pairing positions in some conditions. Al in pairing site is observed only for Ca/(Si+Al) ratios greater than 0.95 (equivalent to 4 mmol.L(-1) of calcium hydroxide). Finally, the results suggest that penta and hexa-coordinated aluminum are adsorbed on the sides of the C-A-S-H particles. PMID:22277014

Pardal, Xiaolin; Brunet, Francine; Charpentier, Thibault; Pochard, Isabelle; Nonat, André

2012-02-01

302

13C-NMR study of 4-azasteroids in solution and solid state.  

PubMed

A group of biologically active 4-azasteroids was studied by 13C-NMR spectroscopy in solution and in the solid phase. A full assignment of signals in the spectra of samples in chloroform was performed for thirteen 4-azasteroids using two-dimensional techniques. Substituent and steric effects of a nitrogen atom, and their influence on chemical shifts of the neighboring carbon atoms are discussed. CP MAS spectra were obtained for five 4-azasteroids including finasteride. The spectra confirmed polymorphism of the latter compound. In addition to the polymorphic forms that are already known, a new molecular complex of finasteride with dioxane is reported. PMID:11996935

Morzycki, Jacek W; Wawer, Iwona; Gryszkiewicz, Agnieszka; Maj, Jadwiga; Siergiejczyk, Leszek; Zaworska, Alicja

2002-06-01

303

High Resolution Solid State 13C NMR Spectroscopy of Sporopollenins from Different Plant Taxa  

PubMed Central

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

Guilford, William J.; Schneider, Diane M.; Labovitz, Jeffrey; Opella, Stanley J.

1988-01-01

304

Solid-state NMR analysis of a complex crystalline phase of ronacaleret hydrochloride.  

PubMed

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. PMID:25133518

Vogt, Frederick G; Williams, Glenn R; Strohmeier, Mark; Johnson, Matthew N; Copley, Royston C B

2014-08-28

305

Dipole tensor-based atomic-resolution structure determination of a nanocrystalline protein by solid-state NMR  

PubMed Central

Magic-angle spinning (MAS) solid-state NMR (SSNMR) techniques have emerged in recent years for solving complete structures of uniformly labeled proteins lacking macroscopic order. Strategies used thus far have relied primarily on semiquantitative distance restraints, analogous to the nuclear Overhauser effect (NOE) routinely used in solution NMR. Here, we present a complementary approach for using relative orientations of molecular fragments, determined from dipolar line shapes. Whereas SSNMR distance restraints typically have an uncertainty of ?1 ?, the tensor-based experiments report on relative vector (pseudobond) angles with precision of a few degrees. By using 3D techniques of this type, vector angle (VEAN) restraints were determined for the majority of the 56-residue B1 immunoglobulin binding domain of protein G [protein GB1 (a total of 47 HN-HN, 49 HN-HC, and 12 HA-HB restraints)]. By using distance restraints alone in the structure calculations, the overall backbone root-mean-square deviation (bbRMSD) was 1.01 ± 0.13 ? (1.52 ± 0.12 ? for all heavy atoms), which improved to 0.49 ± 0.05 ? (1.19 ± 0.07 ?) on the addition of empirical chemical shift [torsion angle likelihood obtained from shift and sequence similarity (TALOS)] restraints. VEAN restraints further improved the ensemble to 0.31 ± 0.06 ? bbRMSD (1.06 ± 0.07 ?); relative to the structure with distances alone, most of the improvement remained (bbRMSD 0.64 ± 0.09 ?; 1.29 ± 0.07 ?) when TALOS restraints were removed before refinement. These results represent significant progress toward atomic-resolution protein structure determination by SSNMR, capabilities that can be applied to a large range of membrane proteins and fibrils, which are often not amenable to solution NMR or x-ray crystallography. PMID:18344321

Franks, W. Trent; Wylie, Benjamin J.; Schmidt, Heather L. Frericks; Nieuwkoop, Andrew J.; Mayrhofer, Rebecca-Maria; Shah, Gautam J.; Graesser, Daniel T.; Rienstra, Chad M.

2008-01-01

306

Hyperpolarized NMR Probes for Biological Assays  

PubMed Central

During the last decade, the development of nuclear spin polarization enhanced (hyperpolarized) molecular probes has opened up new opportunities for studying the inner workings of living cells in real time. The hyperpolarized probes are produced ex situ, introduced into biological systems and detected with high sensitivity and contrast against background signals using high resolution NMR spectroscopy. A variety of natural, derivatized and designed hyperpolarized probes has emerged for diverse biological studies including assays of intracellular reaction progression, pathway kinetics, probe uptake and export, pH, redox state, reactive oxygen species, ion concentrations, drug efficacy or oncogenic signaling. These probes are readily used directly under natural conditions in biofluids and are often directly developed and optimized for cellular assays, thus leaving little doubt about their specificity and utility under biologically relevant conditions. Hyperpolarized molecular probes for biological NMR spectroscopy enable the unbiased detection of complex processes by virtue of the high spectral resolution, structural specificity and quantifiability of NMR signals. Here, we provide a survey of strategies used for the selection, design and use of hyperpolarized NMR probes in biological assays, and describe current limitations and developments. PMID:24441771

Meier, Sebastian; Jensen, Pernille R.; Karlsson, Magnus; Lerche, Mathilde H.

2014-01-01

307

Solid state NMR and IR characterization of wood polymer structure in relation to tree provenance.  

PubMed

(13)C nuclear magnetic resonance and mid-infrared spectroscopies were used for characterizing changes in the chemical structure of wood polymers (cellulose, hemicellulose and lignin) in relation to the tree growth location. Samples of three provenances in Europe (Finland, Poland and Italy) were selected for studies. The requirement was to use untreated solid wood samples to minimize any manipulation to the nanostructure of native wood. The results confirm that the chemical and physical properties of samples belonging to the same wood species (Picea abies Karst.) differ due to the origin. Both FT-IR and dynamic NMR spectroscopies were able to correctly discriminate samples originating from three different provenances in Europe. Such methods might be very useful for both, research and understanding of wood microstructure and its variability due to the growth conditions. PMID:25498692

Santoni, Ilaria; Callone, Emanuela; Sandak, Anna; Sandak, Jakub; Dirè, Sandra

2015-03-01

308

Effects of molecular mobility on high resolution solid state NMR spectra: model systems  

SciTech Connect

It is the intention of this paper to point to some of the problems due to molecular motion and to suggest a few solutions to those problems. A few examples will be presented of model systems which demonstrate the effects of motion on the NMR spectroscopy and a very qualitative example of severe spectral distortion in fulvic acids will be shown. In the following discussions we will use concepts derived from the oft repeated thermodynamic picture shown in figure 1. When dealing with a homogeneous, pure compound this picture is sufficient but in a heterogeneous mixture, it is likely that there will be different compounds and different domains all with slightly different versions of figure 1 with poor thermodynamic contact between them. Thus optimal conditions for cross polarization in one domain may be totally inappropriate for another. 59 refs., 10 figs.

Earl, W.L.

1986-01-01

309

Pore structure, thinning effect, and lateral diffusive dynamics of oriented lipid membranes interacting with antimicrobial peptide protegrin-1: 31P and 2H solid-state NMR study.  

PubMed

Membrane pores that are induced in oriented membranes by an antimicrobial peptide (AMP), protegrin-1 (PG-1), are investigated by (31)P and (2)H solid state NMR spectroscopy. We incorporated a well-studied peptide, protegrin-1 (PG-1), a beta-sheet AMP, to investigate AMP-induced dynamic supramolecular lipid assemblies at different peptide concentrations and membrane compositions. Anisotropic NMR line shapes specifying toroidal pores and thinned membranes, which are formed in membrane bilayers by the binding of AMPs, have been analyzed for the first time. Theoretical NMR line shapes of lipids distributed on the surface of toroidal pores and thinned membranes reproduce reasonably well the line shape characteristics of our experimentally measured (31)P and (2)H solid-state NMR spectra of oriented lipids binding with PG-1. The lateral diffusions of lipids are also analyzed from the motionally averaged one- and two-dimensional (31)P and (2)H solid-state NMR spectra of oriented lipids that are binding with AMPs. PMID:18700738

Wi, Sungsool; Kim, Chul

2008-09-11

310

Modeling an in-register, parallel "iowa" a? fibril structure using solid-state NMR data from labeled samples with rosetta.  

PubMed

Determining the structures of amyloid fibrils is an important first step toward understanding the molecular basis of neurodegenerative diseases. For ?-amyloid (A?) fibrils, conventional solid-state NMR structure determination using uniform labeling is limited by extensive peak overlap. We describe the characterization of a distinct structural polymorph of A? using solid-state NMR, transmission electron microscopy (TEM), and Rosetta model building. First, the overall fibril arrangement is established using mass-per-length measurements from TEM. Then, the fibril backbone arrangement, stacking registry, and "steric zipper" core interactions are determined using a number of solid-state NMR techniques on sparsely (13)C-labeled samples. Finally, we perform Rosetta structure calculations with an explicitly symmetric representation of the system. We demonstrate the power of the hybrid Rosetta/NMR approach by modeling the in-register, parallel "Iowa" mutant (D23N) at high resolution (1.2Å backbone rmsd). The final models are validated using an independent set of NMR experiments that confirm key features. PMID:25543257

Sgourakis, Nikolaos G; Yau, Wai-Ming; Qiang, Wei

2015-01-01

311

Pressure-Induced Changes in Crystal-Melt Partitiong Coefficient between Silicate Melts and Crystals: A View from Solid-State NMR  

NASA Astrophysics Data System (ADS)

Silicate melts in the Earth's interior played essential roles in physicochemical differentiation of the early Earth. Diverse macroscopic properties of silicate melts in the Earth's interior including crystal-melt partitioning depend on their atomic structures at high pressures. Despite their essential implications to many geophysical and geodynamic problems, little is known about the nature of silicate glasses at high pressure, including the densification mechanisms and the atomistic origins of the macroscopic properties at high pressure, mostly due to the lack of suitable high-pressure experimental probes. Recent advances in high-resolution multi-dimensional solid-state NMR and synchrotron x-ray raman scattering yielded improved insights into the structure of oxide glasses with varying pressure (e.g. Lee SK. Geochim. Cosmochim. Acta 2005, 69, p3695; Lee SK et al. Nature Materials 2005, 4, p851; Lee SK et al. Phys. Rev. Lett. 2007, 98, 105502)). The structural information from the above advanced spectroscopic tools has been useful to calculate thermodynamic properties including crystal-melt partitioning coefficient (Lee SK. Geochim. Cosmochim. Acta 2005). Here, we report the spectroscopic evidence of differential pressure dependence controlling the abundances of several types oxygen configuration in complex silicate glasses at high pressure. While all of the glasses studied exhibit a general trend of decreasing non-bridging oxygen concentration with pressure, the details of their pressure dependence is strongly dependent on the composition of melts. Several types of non- bridging oxygen in the divers glass also have varying pressure dependence. Fraction of [4,5]Al-O-[4,5]Al in aluminosilicate glasses, a measure of configurational entropy in aluminosilicate glasses decreases with pressure, suggesting a decrease in configurational disorder caused by the mixing among high energy framework units. We then calculated the crystal-melt partition coefficient from the structural information from solid-state NMR and inelastic x-ray scattering. Our results indicate that the detailed structural information around oxygen in silicate melts at high pressures should be taken into the modeling of their thermodynamic properties.

Cody, G.; Lee, S.; Mysen, B.; Fei, Y.

2007-12-01

312

Probing porous media with gas diffusion NMR  

NASA Technical Reports Server (NTRS)

We show that gas diffusion nuclear magnetic resonance (GD-NMR) provides a powerful technique for probing the structure of porous media. In random packs of glass beads, using both laser-polarized and thermally polarized xenon gas, we find that GD-NMR can accurately measure the pore space surface-area-to-volume ratio, S/V rho, and the tortuosity, alpha (the latter quantity being directly related to the system's transport properties). We also show that GD-NMR provides a good measure of the tortuosity of sandstone and complex carbonate rocks.

Mair, R. W.; Wong, G. P.; Hoffmann, D.; Hurlimann, M. D.; Patz, S.; Schwartz, L. M.; Walsworth, R. L.

1999-01-01

313

Solid-State Selective 13C Excitation and Spin Diffusion NMR to Resolve Spatial Dimensions in Plant Cell Walls  

SciTech Connect

The average spatial dimensions between major biopolymers within the plant cell wall can be resolved using a solid-state NMR technique referred to as a {sup 13}C cross-polarization (CP) SELDOM (selectively by destruction of magnetization) with a mixing time delay for spin diffusion. Selective excitation of specific aromatic lignin carbons indicates that lignin is in close proximity to hemicellulose followed by amorphous and finally crystalline cellulose. {sup 13}C spin diffusion time constants (T{sub SD}) were extracted using a two-site spin diffusion theory developed for {sup 13}C nuclei under magic angle spinning (MAS) conditions. These time constants were then used to calculate an average lower-limit spin diffusion length between chemical groups within the plant cell wall. The results on untreated {sup 13}C enriched corn stover stem reveal that the lignin carbons are, on average, located at distances {approx}0.7-2.0 nm from the carbons in hemicellulose and cellulose, whereas the pretreated material had larger separations.

Foston, M.; Katahira, R.; Gjersing, E.; Davis, M. F.; Ragauskas, A. J.

2012-02-15

314

Signal enhancement for the sensitivity-limited solid state NMR experiments using a continuous, non-uniform acquisition scheme  

NASA Astrophysics Data System (ADS)

We describe a sampling scheme for the two-dimensional (2D) solid state NMR experiments, which can be readily applied to the sensitivity-limited samples. The sampling scheme utilizes continuous, non-uniform sampling profile for the indirect dimension, i.e. the acquisition number decreases as a function of the evolution time ( t1) in the indirect dimension. For a beta amyloid (A?) fibril sample, we observed overall 40-50% signal enhancement by measuring the cross peak volume, while the cross peak linewidths remained comparable to the linewidths obtained by regular sampling and processing strategies. Both the linear and Gaussian decay functions for the acquisition numbers result in similar percentage of increment in signal. In addition, we demonstrated that this sampling approach can be applied with different dipolar recoupling approaches such as radiofrequency assisted diffusion (RAD) and finite-pulse radio-frequency-driven recoupling (fpRFDR). This sampling scheme is especially suitable for the sensitivity-limited samples which require long signal averaging for each t1 point, for instance the biological membrane proteins where only a small fraction of the sample is isotopically labeled.

Qiang, Wei

2011-12-01

315

Solid-state NMR study reveals collagen I structural modifications of amino acid side chains upon fibrillogenesis.  

PubMed

In vivo, collagen I, the major structural protein in human body, is found assembled into fibrils. In the present work, we study a high concentrated collagen sample in its soluble, fibrillar, and denatured states using one and two dimensional {(1)H}-(13)C solid-state NMR spectroscopy. We interpret (13)C chemical shift variations in terms of dihedral angle conformation changes. Our data show that fibrillogenesis increases the side chain and backbone structural complexity. Nevertheless, only three to five rotameric equilibria are found for each amino acid residue, indicating a relatively low structural heterogeneity of collagen upon fibrillogenesis. Using side chain statistical data, we calculate equilibrium constants for a great number of amino acid residues. Moreover, based on a (13)C quantitative spectrum, we estimate the percentage of residues implicated in each equilibrium. Our data indicate that fibril formation greatly affects hydroxyproline and proline prolyl pucker ring conformation. Finally, we discuss the implication of these structural data and propose a model in which the attractive force of fibrillogenesis comes from a structural reorganization of 10 to 15% of the amino acids. These results allow us to further understand the self-assembling process and fibrillar structure of collagen. PMID:23341452

De Sa Peixoto, Paulo; Laurent, Guillaume; Azaïs, Thierry; Mosser, Gervaise

2013-03-15

316

Signal enhancement for the sensitivity-limited solid state NMR experiments using a continuous, non-uniform acquisition scheme  

PubMed Central

We describe a sampling scheme for the two-dimensional (2D) solid state NMR experiments, which can be readily applied to the sensitivity-limited samples. The sampling scheme utilizes continuous, non-uniform sampling profile for the indirect dimension, i.e. the acquisition number decreases as a function of the evolution time (t1) in the indirect dimension. For a beta amyloid (A?) fibril sample, we observed overall 40 ~ 50% signal enhancement by measuring the cross peak volume, while the cross peak linewidths remained comparable to the linewidths obtained by regular sampling and processing strategies. Both the linear and Gaussian decay functions for the acquisition numbers result in similar percentage of increment in signal. In addition, we demonstrated that this sampling approach can be applied with different dipolar recoupling approaches such as radiofrequency assisted diffusion (RAD) and finite-pulse radio-frequency-driven recoupling (fpRFDR). This sampling scheme is especially suitable for the sensitivity-limited samples which require long signal averaging for each t1 point, for instance the biological membrane proteins where only a small fraction of the sample is isotopically labeled. PMID:21930405

Qiang, Wei

2011-01-01

317

Effects of Arginine Density on the Membrane-Bound Structure of a Cationic Antimicrobial Peptide from Solid-State NMR  

PubMed Central

Solid-state NMR spectroscopy is used to determine the membrane-bound topological structure of a cationic ?-hairpin antimicrobial peptide in which the number of Arg residues has been halved. The parent peptide, PG-1, was previously found to form transmembrane ?-barrels in anionic membranes where the Arg residues complex with the lipid phosphate groups to cause toroidal pore defects in the membrane. In comparison, the charge-attenuated and less active mutant studied here forms ?-sheets that lie on the surface of the zwitterionic membrane and only partially insert into the anionic membrane. The mutant also exhibits much looser contact with the lipid headgroups. These results indicate that transmembrane insertion and tight Arg-phosphate association are two important elements for strong antimicrobial activities of this class of peptides. Comparison with other ?-hairpin antimicrobial peptides studied so far further suggests a relative potency scale for the various mechanisms of action for the ?-sheet family of antimicrobial peptides. The transmembrane insertion – toroidal pore mechanism is the most potent in disrupting the lipid bilayer, followed by the large-amplitude in-plane motional mechanism. The carpet model, where peptides aggregate on the membrane surface to cause lateral expansion and eventual micellization of the membrane, is a weaker mechanism of action. PMID:19059201

Tang, Ming; Waring, Alan J.; Hong, Mei

2014-01-01

318

51V Solid-state NMR and Density-Functional Theory Studies of Eight-Coordinate Non-Oxo Vanadium Complexes: Oxidized Amavadin  

PubMed Central

SUMMARY Using 51V magic angle spinning solid-state NMR spectroscopy and Density Functional Theory calculations we have characterized the chemical shift and quadrupolar coupling parameters for two eight-coordinate vanadium complexes, [PPh4][V(V)(HIDPA)2] and [PPh4][V(V)(HIDA)2]; HIDPA = 2,2?-(hydroxyimino)dipropionate and HIDA = 2,2?-(hydroxyimino)diacetate. The coordination geometry under examination is the less common non-oxo eight coordinate distorted dodecahedral geometry that has not been previously investigated by solid-state NMR spectroscopy. Both complexes were isolated by oxidizing their reduced forms: [V(IV)(HIDPA)2]2- and [V(IV)(HIDA)2]2-. V(IV)(HIDPA)22- is also known as amavadin, a vanadium-containing natural product present in the Amanita muscaria mushroom and responsible for vanadium accumulation in nature. The quadrupolar coupling constants, CQ, are found to be moderate, 5.0 to 6.4 MHz while the chemical shift anisotropies are relatively small for vanadium complexes, ?420 and 360 ppm. The isotropic chemical shifts in the solid state are ?220 and ?228 ppm for the two compounds, and near the chemical shifts observed in solution. Presumably this is a consequence of the combined effects of the increased coordination number and the absence of oxo groups. Density Functional Theory calculations of the electric field gradient parameters are in good agreement with the NMR results while the chemical shift parameters show some deviation from the experimental values. Future work on this unusual coordination geometry and a combined analysis by solid-state NMR and Density Functional Theory should provide a better understanding of the correlations between experimental NMR parameters and the local structure of the vanadium centers. PMID:19421628

Ooms, Kristopher J.; Bolte, Stephanie E.; Baruah, Bharat; Choudhary, Muhammad Aziz; Crans, Debbie C.; Polenova, Tatyana

2014-01-01

319

33S NMR cryogenic probe for taurine detection  

NASA Astrophysics Data System (ADS)

With the goal of a S33 nuclear magnetic resonance (NMR) probe applicable to in vivo NMR on taurine-biological samples, we have developed the S33 NMR cryogenic probe, which is applicable to taurine solutions. The NMR sensitivity gain relative to a conventional broadband probe is as large as 3.5. This work suggests that improvements in the preamplifier could allow NMR measurements on 100 ?M taurine solutions, which is the level of sensitivity necessary for biological samples.

Hobo, Fumio; Takahashi, Masato; Maeda, Hideaki

2009-03-01

320

Conformation and Orientation of Gramicidin a in Oriented Phospholipid Bilayers Measured by Solid State Carbon-13 NMR  

PubMed Central

Three analogues of the helical ionophore gramicidin A have been synthesized with 13C-labeled carbonyls (13C=O) incorporated at either Gly2, Ala3, or Val7. A fourth compound incorporated 13C at both the carbonyl and ?-carbon of Gly2 within the same molecule. These labels were studied using solid-state, proton-enhanced, 13C nuclear magnetic resonance (NMR) in hydrated dispersions of dimyristoylphosphatidylcholine (DMPC)-gramicidin A. The dispersions were aligned on glass coverslips whose orientation to the magnetic field could be varied through 180°. The orientation dependence of the NMR spectrum was used to obtain an accurate measurement of the 13C chemical shift anisotropy (CSA), and in the case of the fourth compound, the 13C—13C dipolar coupling constant. From the measured CSA and estimates of the orientation of the 13C shielding tensor, we are able to determine the direction of the 13C=O bonds and to compare these with the predictions of the various reported models for the configuration of gramicidin A in phospholipid bilayers. Our results are consistent with the left-handed ??6.3LD single-stranded helix (Urry, D. W., J. T. Walker, and T. L. Trapane. 1982. J. Membr. Biol. 69:225-231). The right-handed ??6.3LD single-stranded helix observed for gramicidin A in sodium dodecyl sulfate micelles (Arseniev, A. S., I. L. Barsukov, V. F. Bystrov, A. L. Loize, and Yu A. Ovchinnikov. 1985. FEBS (Fed. Eur. Biochem. Soc.) Lett. 186:168-174) yields a poorer fit to the data. However, the width of the carbonyl resonances suggests a distribution of molecular geometries possibly resulting from a spread in the helix pitch and handedness. Double-stranded helices and ? sheet structures are excluded. In dispersions in which the lipid is in the L? phase, the gramicidin A undergoes rapid reorientation about an axis which is centered on the normal to the plane of the coverslips. When the supporting lipid is in the L?? phase the helices are rigid on the timescale of 13C-NMR. The configuration of gramicidin A is unaltered by L?-L?? phase transition of the bilayer lipid. PMID:19431717

Cornell, Bruce A.; Separovic, Frances; Baldassi, Attilio J.; Smith, Ross

1988-01-01

321

Mechanism of formation of humus coatings on mineral surfaces 3. Composition of adsorbed organic acids from compost leachate on alumina by solid-state 13C NMR  

USGS Publications Warehouse

The adsorption of compost leachate DOC on alumina is used as a model for elucidation of the mechanism of formation of natural organic coatings on hydrous metal oxide surfaces in soils and sediments. Compost leachate DOC is composed mainly of organic acid molecules. The solid-state 13C NMR spectra of these organic acids indicate that they are very similar in composition to aquatic humic substances. Changes in the solid-state 13C NMR spectra of compost leachate DOC fractions adsorbed on alumina indicate that the DOC molecules are most likely adsorbed on metal oxide surfaces through a combination of polar and hydrophobic interaction mechanisms. This combination of polar and hydrophobic mechanism leads to the formation of bilayer coatings of the leachate molecules on the oxide surfaces.

Wershaw, R.L.; Llaguno, E.C.; Leenheer, J.A.

1996-01-01

322

The Muon g-2 Experiment The NMR Probe Circuitry  

E-print Network

The Muon g-2 Experiment The NMR Probe Circuitry Upgrading the Circuit Building the Circuit Future Work Updating NMR Probe Electronics in the Muon g-2 Experiment Audrey Kvam University of Washington September 1, 2014 Audrey Kvam Updating NMR Probe Electronics in the Muon g-2 Experiment #12;The Muon g-2

Washington at Seattle, University of - Department of Physics, Electroweak Interaction Research Group

323

Solid state CP\\/MAS 13C NMR of the insoluble organic matter of the Orgueil and Murchison meteorites: quantitative study  

Microsoft Academic Search

Solid state CP\\/MAS 13C nuclear magnetic resonance (NMR) study of the insoluble organic fraction isolated by HF\\/HCl treatment under an inert atmosphere from the Orgueil and Murchison carbonaceous meteorites is reported. Based on these spectra, eight different types of carbons (aro- and ali-linked CH3, CH2, aliphatic C-linked to heteroelements, protonated and non-protonated aromatic C, carboxyls and carbonyls) were identified, their

Alain Gardinier; Sylvie Derenne; François Robert; Françoise Behar; Claude Largeau; Jocelyne Maquet

2000-01-01

324

1D and 2D solid state NMR investigations of the framework structure of As-synthesized AlPO 4-14  

Microsoft Academic Search

The framework structure of As-synthesized A1PO4-14 has been investigated with a combination of different one-dimensional 27Al and 31P solid state NMR techniques and 27Al31P double resonance methods. The results are found to be fully consistent with the assumed structural model. 27Al MAS and DOR experiments at three different magnetic field strengths together with simulations show the presence of two tetrahedral

C. A. Fyfe; H. Meyer zu Altenschildesche; K. C. Wong-Moon; H. Grondey; J. M. Chezeau

1997-01-01

325

Local environment and composition of magnesium gallium layered double hydroxides determined from solid-state 1H and 71Ga NMR spectroscopy  

SciTech Connect

Ordering of gallium(III) in a series of magnesium gallium layered double hydroxides (LDH’s), [Mg1-xGax(OH)2(NO3)x yH2O], was determined using solid-state 1H and 71Ga NMR spectroscopy. Depletion of Ga in these LDH’s is demonstrated to be the result of soluble [Ga(OH)4]-complexes formed during synthesis.

Petersen, Line B.; Lipton, Andrew S.; Zorin, Vadim; Nielsen, Ulla Gro

2014-11-01

326

Orphan spin operators enable the acquisition of multiple 2D and 3D magic angle spinning solid-state NMR spectra  

NASA Astrophysics Data System (ADS)

We propose a general method that enables the acquisition of multiple 2D and 3D solid-state NMR spectra for U-13C, 15N-labeled proteins. This method, called MEIOSIS (Multiple ExperIments via Orphan SpIn operatorS), makes it possible to detect four coherence transfer pathways simultaneously, utilizing orphan (i.e., neglected) spin operators of nuclear spin polarization generated during 15N-13C cross polarization (CP). In the MEIOSIS experiments, two phase-encoded free-induction decays are decoded into independent nuclear polarization pathways using Hadamard transformations. As a proof of principle, we show the acquisition of multiple 2D and 3D spectra of U-13C, 15N-labeled microcrystalline ubiquitin. Hadamard decoding of CP coherences into multiple independent spin operators is a new concept in solid-state NMR and is extendable to many other multidimensional experiments. The MEIOSIS method will increase the throughput of solid-state NMR techniques for microcrystalline proteins, membrane proteins, and protein fibrils.

Gopinath, T.; Veglia, Gianluigi

2013-05-01

327

Structure and Alignment of the Membrane-Associated Peptaibols Ampullosporin A and Alamethicin by Oriented 15N and 31P Solid-State NMR Spectroscopy  

PubMed Central

Abstract Ampullosporin A and alamethicin are two members of the peptaibol family of antimicrobial peptides. These compounds are produced by fungi and are characterized by a high content of hydrophobic amino acids, and in particular the ?-tetrasubstituted amino acid residue ?-aminoisobutyric acid. Here ampullosporin A and alamethicin were uniformly labeled with 15N, purified and reconstituted into oriented phophatidylcholine lipid bilayers and investigated by proton-decoupled 15N and 31P solid-state NMR spectroscopy. Whereas alamethicin (20 amino acid residues) adopts transmembrane alignments in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membranes the much shorter ampullosporin A (15 residues) exhibits comparable configurations only in thin membranes. In contrast the latter compound is oriented parallel to the membrane surface in 1,2-dimyristoleoyl-sn-glycero-3-phosphocholine and POPC bilayers indicating that hydrophobic mismatch has a decisive effect on the membrane topology of these peptides. Two-dimensional 15N chemical shift – 1H-15N dipolar coupling solid-state NMR correlation spectroscopy suggests that in their transmembrane configuration both peptides adopt mixed ?-/310-helical structures which can be explained by the restraints imposed by the membranes and the bulky ?-aminoisobutyric acid residues. The 15N solid-state NMR spectra also provide detailed information on the helical tilt angles. The results are discussed with regard to the antimicrobial activities of the peptides. PMID:18835909

Salnikov, Evgeniy S.; Friedrich, Herdis; Li, Xing; Bertani, Philippe; Reissmann, Siegmund; Hertweck, Christian; O'Neil, Joe D.J.; Raap, Jan; Bechinger, Burkhard

2009-01-01

328

Solid State CARBON-13 NMR and Thermal Analysis of Conformational Motion and Disorder in Small and Large Molecules  

NASA Astrophysics Data System (ADS)

In this work it is attempted to explore the conformational motion and disorder through a large number of examples of molecular systems differing in shape, rigidity, and molecular weight: a series of tetra-n-alkylammonium bromides and iodides, a liquid-crystal-forming molecule, N,N ^'-bis(4-n-octyloxybenzal)-1,4 -phenylenediamine (OOBPD), and polymers, poly (oxy-1,4-(3 -methylphenylene)ethylene-1,4-phenyleneoxy-nonamethylene ] (MBPE-9) and poly (oxy-1,4 -(3-methylphenylene)ethylene-1,4-phenyleneoxypentamethylene ] (MBPE-5). The techniques used to study the conformational motion and disorder are mainly solid state ^{13}C nuclear magnetic resonance (NMR) spectroscopy and thermal analysis. The results of this work show that conformational disordered states (condis crystals) exist indeed in these molecules containing flexible chemical bonds (single bonds) or more than one accessible conformer. The unique characteristics of the condis crystal and the phase transitions to a condis crystal and to isotropic state have been studied in detail. It could be shown that motifs in condis crystals show only conformational disorder but maintaining orientational and positional order, while liquid and plastic crystals show conformational motion in addition to their characteristic positional and orientational disorder and motion, respectively. The molecular motion in the condis state is slow compared to well-known plastic and liquid crystals. Besides the large -amplitude motion in a first-order transition, it is documented that gradual start of motion is possible increasing the conformational entropy over a broad temperature range.

Cheng, Jinlong

329

Characterization of crystal forms of ?-estradiol thermal analysis, Raman microscopy, X-ray analysis and solid-state NMR  

NASA Astrophysics Data System (ADS)

The structure and select crystalline properties of a common drug (estradiol) used in a transdermal drug delivery system are investigated. Four different crystal forms of estradiol (EA, EC, ED and EM) were prepared in the laboratory and characterized by thermal analysis, optical microscopy, Raman microspectroscopy, and solid-state NMR. Variable temperature X-ray studies were carried out on form A (EA) to determine whether the crystal structure changed as a function of temperature. These four forms exhibited different thermal behavior. EA and EC had similar melting points. This study clearly shows that water cannot be released from the crystal lattice of EA unless melting is achieved, and exposing EA to temperatures below the melting point only results in a partial release of hydrogen bonded water. EC was prepared by melting EA and subsequently cooling it to room temperature. Form EC was anhydrous, as it did not exhibit water loss, as opposed to EA, which had about 3.5% water in its crystal structure. ED was very difficult to prepare and manifested itself only as a mixture with EC. Its melting point was about 10°C lower than that of EC. It is thought to be an unstable form due to its simultaneous occurrence with EC and the inability to isolate it. EM is a solvate of methanol, not a polymorph. Its melting point was similar to EA and EC. From thermogravimetry/differential thermal analysis and differential scanning calorimetry data, it was apparent that estradiol formed a hemisolvate with methanol. All four forms had different morphologies. Raman microscopy was carried out on the different crystal forms. The spectra of EC and ED were almost identical. Thermal analysis revealed that this is due to the highly unstable nature of ED and its tendency to either convert spontaneously to EC or occur in mixtures with it.

Variankaval, N. E.; Jacob, K. I.; Dinh, S. M.

2000-08-01

330

Direct Speciation of Phosphorus in Alum-Amended Poultry Litter: Solid-State 31P NMR Investigation  

SciTech Connect

Amending poultry litter (PL) with aluminum sulfate (alum) has proven to be effective in reducing water-soluble phosphorus (P) in the litter and in runoff from fields that have received PL applications; it has therefore been suggested as a best management practice. Although its effectiveness has been demonstrated on a macroscopic scale in the field, little is known about P speciation in either alumamended or unamended litter. This knowledge is important for the evaluation of the long-term stability and bioavailability of P, which is a necessary prerequisite for the assessment of the sustainability of intensive poultry operations. Both solid state MAS and CP-MAS {sup 31}P NMR as well as {sup 31}P({sup 27}Al) TRAPDOR were used to investigate P speciation in alumamended and unamended PL. The results indicate the presence of a complex mixture of organic and inorganic orthophosphate phases. A calcium phosphate phase, probably a surface precipitate on calcium carbonate, could be identified in both unamended and alum-amended PL, as well as physically bound HPO{sub 4}{sup 2-}. Phosphate associated with Al was found in the alum-amended PL, most probably a mixture of a poorly ordered wavellite and phosphate surface complexes on aluminum hydroxide that had been formed by the hydrolysis of alum. However, a complex mixture of organic and inorganic phosphate species could not be resolved. Phosphate associated with Al comprised on average 40{+-}14% of the total P in alum-amended PL, whereas calcium phosphate phases comprised on average 7{+-}4% in the alum-amended PL and 14{+-}5% in the unamended PL.

Hunger, Stefan; Cho, Herman M.; Sims, James T.; Sparks, Donald L.

2004-02-01

331

Water-polysaccharide interactions in the primary cell wall of Arabidopsis thaliana from polarization transfer solid-state NMR.  

PubMed

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 (1)H polarization to polysaccharides through distance- and mobility-dependent (1)H-(1)H dipolar couplings and detecting it through polysaccharide (13)C 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. PMID:24984197

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

2014-07-23

332

Deciphering membrane insertion of the diphtheria toxin T domain by specular neutron reflectometry and solid-state NMR spectroscopy.  

PubMed

Insertion and translocation of soluble proteins into and across biological membranes are involved in many physiological and pathological processes, but remain poorly understood. Here, we describe the pH-dependent membrane insertion of the diphtheria toxin T domain in lipid bilayers by specular neutron reflectometry and solid-state NMR spectroscopy. We gained unprecedented structural resolution using contrast-variation techniques that allow us to propose a sequential model of the membrane-insertion process at angstrom resolution along the perpendicular axis of the membrane. At pH 6, the native tertiary structure of the T domain unfolds, allowing its binding to the membrane. The membrane-bound state is characterized by a localization of the C-terminal hydrophobic helices within the outer third of the cis fatty acyl-chain region, and these helices are oriented predominantly parallel to the plane of the membrane. In contrast, the amphiphilic N-terminal helices remain in the buffer, above the polar headgroups due to repulsive electrostatic interactions. At pH 4, repulsive interactions vanish; the N-terminal helices penetrate the headgroup region and are oriented parallel to the plane of the membrane. The C-terminal helices penetrate deeper into the bilayer and occupy about two thirds of the acyl-chain region. These helices do not adopt a transmembrane orientation. Interestingly, the T domain induces disorder in the surrounding phospholipids and creates a continuum of water molecules spanning the membrane. We propose that this local destabilization permeabilizes the lipid bilayer and facilitates the translocation of the catalytic domain across the membrane. PMID:19576225

Chenal, Alexandre; Prongidi-Fix, Lydia; Perier, Aurélie; Aisenbrey, Christopher; Vernier, Grégory; Lambotte, Stephan; Haertlein, Michael; Dauvergne, Marie-Thérèse; Fragneto, Giovanna; Bechinger, Burkhard; Gillet, Daniel; Forge, Vincent; Ferrand, Michel

2009-09-01

333

Active-site structure of the thermophilic Foc-subunit ring in membranes elucidated by solid-state NMR.  

PubMed

FoF1-ATP synthase uses the electrochemical potential across membranes or ATP hydrolysis to rotate the Foc-subunit ring. To elucidate the underlying mechanism, we carried out a structural analysis focused on the active site of the thermophilic c-subunit (TFoc) ring in membranes with a solid-state NMR method developed for this purpose. We used stereo-array isotope labeling (SAIL) with a cell-free system to highlight the target. TFoc oligomers were purified using a virtual ring His tag. The membrane-reconstituted TFoc oligomer was confirmed to be a ring indistinguishable from that expressed in E. coli on the basis of the H(+)-translocation activity and high-speed atomic force microscopic images. For the analysis of the active site, 2D (13)C-(13)C correlation spectra of TFoc rings labeled with SAIL-Glu and -Asn were recorded. Complete signal assignment could be performed with the aid of the C(?)i+1-C(?)i correlation spectrum of specifically (13)C,(15)N-labeled TFoc rings. The C(?) chemical shift of Glu-56, which is essential for H(+) translocation, and related crosspeaks revealed that its carboxyl group is protonated in the membrane, forming the H(+)-locked conformation with Asn-23. The chemical shift of Asp-61 C(?) of the E. coli c ring indicated an involvement of a water molecule in the H(+) locking, in contrast to the involvement of Asn-23 in the TFoc ring, suggesting two different means of proton storage in the c rings. PMID:24461014

Kang, Su-Jin; Todokoro, Yasuto; Yumen, Ikuko; Shen, Bo; Iwasaki, Iku; Suzuki, Toshiharu; Miyagi, Atsushi; Yoshida, Masasuke; Fujiwara, Toshimichi; Akutsu, Hideo

2014-01-21

334

Active-Site Structure of the Thermophilic Foc-Subunit Ring in Membranes Elucidated by Solid-State NMR  

PubMed Central

FoF1-ATP synthase uses the electrochemical potential across membranes or ATP hydrolysis to rotate the Foc-subunit ring. To elucidate the underlying mechanism, we carried out a structural analysis focused on the active site of the thermophilic c-subunit (TFoc) ring in membranes with a solid-state NMR method developed for this purpose. We used stereo-array isotope labeling (SAIL) with a cell-free system to highlight the target. TFoc oligomers were purified using a virtual ring His tag. The membrane-reconstituted TFoc oligomer was confirmed to be a ring indistinguishable from that expressed in E. coli on the basis of the H+-translocation activity and high-speed atomic force microscopic images. For the analysis of the active site, 2D 13C-13C correlation spectra of TFoc rings labeled with SAIL-Glu and -Asn were recorded. Complete signal assignment could be performed with the aid of the C?i+1-C?i correlation spectrum of specifically 13C,15N-labeled TFoc rings. The C? chemical shift of Glu-56, which is essential for H+ translocation, and related crosspeaks revealed that its carboxyl group is protonated in the membrane, forming the H+-locked conformation with Asn-23. The chemical shift of Asp-61 C? of the E. coli c ring indicated an involvement of a water molecule in the H+ locking, in contrast to the involvement of Asn-23 in the TFoc ring, suggesting two different means of proton storage in the c rings. PMID:24461014

Kang, Su-Jin; Todokoro, Yasuto; Yumen, Ikuko; Shen, Bo; Iwasaki, Iku; Suzuki, Toshiharu; Miyagi, Atsushi; Yoshida, Masasuke; Fujiwara, Toshimichi; Akutsu, Hideo

2014-01-01

335

Molecular-level secondary structure, polymorphism, and dynamics of full-length -synuclein fibrils studied by solid-state NMR  

NASA Astrophysics Data System (ADS)

The 140-residue protein -synuclein (AS) is able to form amyloid fibrils and as such is the main component of protein inclusions involved in Parkinson's disease. We have investigated the structure and dynamics of full-length AS fibrils by high-resolution solid-state NMR spectroscopy. Homonuclear and heteronuclear 2D and 3D spectra of fibrils grown from uniformly 13C/15N-labeled AS and AS reverse-labeled for two of the most abundant amino acids, K and V, were analyzed. 13C and 15N signals exhibited linewidths of <0.7 ppm. Sequential assignments were obtained for 48 residues in the hydrophobic core region. We identified two different types of fibrils displaying chemical-shift differences of up to 13 ppm in the 15N dimension and up to 5 ppm for backbone and side-chain 13C chemical shifts. EM studies suggested that molecular structure is correlated with fibril morphology. Investigation of the secondary structure revealed that most amino acids of the core region belong to -strands with similar torsion angles in both conformations. Selection of regions with different mobility indicated the existence of monomers in the sample and allowed the identification of mobile segments of the protein within the fibril in the presence of monomeric protein. At least 35 C-terminal residues were mobile and lacked a defined secondary structure, whereas the N terminus was rigid starting from residue 22. Our findings agree well with the overall picture obtained with other methods and provide insight into the amyloid fibril structure and dynamics with residue-specific resolution. EM | protein structure | amyloid | Parkinson's disease | protein aggregation


Heise, Henrike; Hoyer, Wolfgang; Becker, Stefan; Andronesi, Ovidiu C.; Riedel, Dietmar; Baldus, Marc

2005-11-01

336

Theoretical predictions of the two-dimensional solid-state NMR spectra: A case study of the 13C-1H correlations in metergoline  

NASA Astrophysics Data System (ADS)

A new method for the treatment of data from multidimensional solid-state NMR investigations is described. It approximates the theoretical NMR chemical shifts from the chemical shielding values obtained by first-principles calculations and subsequently treats these results to quantify the similarity between predicted and experimental chemical shift correlations. The test case of this approach is performed for the measured and several sets of computed 13C-1H heteronuclear correlations in the polymorphic form I of metergoline, which is relatively large, pharmaceutically active system. The proposed protocol is general, however, and it can be immediately applied to study other compounds and nuclei.

Czernek, Ji?í; Brus, J.

2013-10-01

337

Structures of ?-hairpin Antimicrobial Protegrin Peptides in Lipopolysaccharide Membranes: Mechanism of Gram Selectivity Obtained From Solid-State NMR  

PubMed Central

The structural basis for the Gram selectivity of two disulfide-bonded ?-hairpin antimicrobial peptides (AMPs) is investigated using solid-state NMR spectroscopy. The hexa-arginine PG-1 exhibits potent activities against both Gram-positive and Gram-negative bacteria, while a mutant of PG-1 with only three cationic residues maintains Gram-positive activity but is 30-fold less active against Gram-negative bacteria. We determined the topological structure and lipid interactions of these two peptides in a lipopolysaccharide (LPS)-rich membrane that mimics the outer membrane of Gram-negative bacteria and in the POPE/POPG membrane, which mimics the membrane of Gram-positive bacteria. 31P NMR lineshapes indicate that both peptides cause less orientational disorder to the LPS-rich membrane than to the POPE/POPG membrane. 13C chemical shifts and 13C-1H dipolar couplings show that both peptides maintain their ?-hairpin conformation in these membranes and are largely immobilized, but the mutant exhibited noticeable intermediate-timescale motion in the LPS membrane at physiological temperature, suggesting shallow insertion. Indeed, 1H spin diffusion from lipid chains to the peptides showed that PG-1 fully inserted into the LPS-rich membrane whereas the mutant did not. The 13C-31P distances between the most hydrophobically embedded Arg of PG-1 and the lipid 31P are significantly longer in the LPS membrane than in the POPE/POPG membrane, indicating that PG-1 does not cause toroidal pore defects in the LPS membrane, in contrast to its behavior in the POPE/POPG membrane. Taken together, these data indicate that PG-1 causes transmembrane pores of the barrel-stave type in the LPS membrane, thus allowing further translocation of the peptide into the inner membrane of Gram-negative bacteria to kill the cells. In comparison, the less cationic mutant cannot fully cross the LPS membrane due to weaker electrostatic attractions, thus causing weaker antimicrobial activities. Therefore, strong electrostatic attraction between the peptide and the membrane surface, ensured by having a sufficient number of Arg residues, is essential for potent antimicrobial activities against Gram-negative bacteria. The data provide a rational basis for controlling Gram selectivity of AMPs by adjusting the charge densities. PMID:21302955

Su, Yongchao; Waring, Alan J.; Ruchala, Piotr; Hong, Mei

2011-01-01

338

Insights on the Interactions of Synthetic Amphipathic Peptides with Model Membranes as Revealed by 31P and 2H Solid-State NMR and Infrared Spectroscopies  

PubMed Central

We studied the interaction between synthetic amphipathic peptides and model membranes by solid-state NMR and infrared spectroscopies. Peptides with 14 and 21 amino acids composed of leucines and phenylalanines modified by the addition of crown ethers were synthesized. The 14-mer and 21-mer peptides both possess a helical amphipathic structure. To shed light on their membrane interaction, 31P and 2H solid-state NMR experiments were performed on both peptides in interaction with dimyristoylphosphatidylcholine vesicles in the absence and presence of cholesterol, dimyristoylphosphatidylglycerol vesicles, and oriented bicelles. 31P NMR experiments on multilamellar vesicles reveal that the dynamics and/or orientation of the polar headgroups are weakly yet markedly affected by the presence of the peptides, whereas 31P NMR experiments on bicelles indicate no significant changes in the morphology and orientation of the bicelles. On the other hand, 2H NMR experiments on vesicles reveal that the acyl chain order is affected differently depending on the membrane lipidic composition and on the peptide hydrophobic length. Finally, infrared spectroscopy was used to study the interfacial region of the bilayer. Based on these studies, mechanisms of membrane perturbation are proposed for the 14-mer and 21-mer peptides in interaction with model membranes depending on the bilayer composition and peptide length. PMID:16533836

Ouellet, Marise; Bernard, Geneviève; Voyer, Normand; Auger, Michèle

2006-01-01

339

1H, 13C MAS NMR and DFT GIAO study of quercetin and its complex with Al(III) in solid state.  

PubMed

Quercetin (Q) as a pentahydroxy flavonoid, has three possible chelating sites competing in complexation processes. (1)H and (13)C MAS NMR spectra were recorded for solid quercetin and its Al(III) complex (AlQ). (1)H MAS spectrum of quercetin shows a broad resonance at ca. 12 ppm that confirms the existence of intramolecular C5-OH … O=C4 hydrogen bond. Such a signal is absent in the spectrum of AlQ, which is in accordance with other spectroscopic data and the suggested model for the solid-state structure of the complex. DFT GIAO calculations were used to verify the experimental (13)C CPMAS NMR data and to suggest the best model structure for the complex AlQ. The calculated shielding constants for different conformers of isolated quercetin molecules, quercetin trimer as taken from the X-ray data, and different model structures for possible Al(III) complexes were compared with the (13)C CPMAS NMR experimental values. The results demonstrate the importance of intermolecular interactions when dealing with structures in solid state and the successful application of the combined DFT GIAO and (13)C CPMAS NMR approach. All data confirm that the chelating site of Q in the solid complex AlQ involves the deprotonated C5-OH and the C4=O groups at ring C, in contrast to the available studies performed in solution. PMID:22459171

Ahmedova, Anife; Paradowska, Katarzyna; Wawer, Iwona

2012-05-01

340

Anomalous diffusion in a gel-fluid lipid environment: a combined solid-state NMR and obstructed random-walk perspective.  

PubMed

Lateral diffusion is an essential process for the functioning of biological membranes. Solid-state nuclear magnetic resonance (NMR) is, a priori, a well-suited technique to study lateral diffusion within a heterogeneous environment such as the cell membrane. Moreover, restriction of lateral motions by lateral heterogeneities can be used as a means to characterize their geometry. The goal of this work is to understand the advantages and limitations of solid-state NMR exchange experiments in the study of obstructed lateral diffusion in model membranes. For this purpose, simulations of lateral diffusion on a sphere with varying numbers and sizes of immobile obstacles and different percolation properties were performed. From the results of these simulations, two-dimensional 31P NMR exchange maps and time-dependent autocorrelation functions were calculated. The results indicate that the technique is highly sensitive to percolation properties, total obstacle area, and, within certain limits, obstacle size. A practical example is shown, namely the study of the well-characterized DMPC-DSPC binary mixture. The comparison of experimental and simulated results yielded obstacle sizes in the range of hundreds of nanometers, therefore bridging the gap between previously published NMR and fluorescence recovery after photobleaching results. The method could also be applied to the study of membrane protein lateral diffusion in model membranes. PMID:15454443

Arnold, Alexandre; Paris, Michaël; Auger, Michèle

2004-10-01

341

The stoichiometry of synthetic alunite as a function of hydrothermal aging investigated by solid-state NMR spectroscopy, powder X-ray diffraction and infrared spectroscopy  

NASA Astrophysics Data System (ADS)

The stoichiometry of a series of synthetic alunite [nominally KAl3(SO4)2(OH)6] samples prepared by hydrothermal methods as a function of reaction time (1-31 days) has been investigated by powder X-ray diffraction, Fourier transform infrared spectroscopy as well as solid-state 1H and 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The 1H MAS NMR spectra recorded at high magnetic field (21.1 T, 900 MHz) allowed for a clear separation of the different proton environments and for quantitative determination of the aluminum vacancy concentration as a function of time. The concentration of structural defects determined from, i.e., aluminum vacancies was reduced from 4 to 1 %, as the reaction time was extended from one to 31 days based on 1H MAS NMR. This was further supported by an increase of the unit cell parameter c, which is indicative of the relative concentration of potassium defects present, from 17.261(1) to 17.324(5) Å. Solid-state 27Al MAS NMR revealed a decrease in the defect concentration as a function of time and showed the presence of 7-10 % impurities in the samples.

Grube, Elisabeth; Nielsen, Ulla Gro

2014-11-01

342

High-resolution solid-state oxygen-17 NMR of actinide-bearing compounds: an insight into the 5f chemistry.  

PubMed

A massive interest has been generated lately by the improvement of solid-state magic-angle spinning (MAS) NMR methods for the study of a broad range of paramagnetic organic and inorganic materials. The open-shell cations at the origin of this paramagnetism can be metals, transition metals, or rare-earth elements. Actinide-bearing compounds and their 5f unpaired electrons remain elusive in this intensive research area due to their well-known high radiotoxicity. A dedicated effort enabling the handling of these highly radioactive materials now allows their analysis using high-resolution MAS NMR (>55 kHz). Here, the study of the local structure of a series of actinide dioxides, namely, ThO2, UO2, NpO2, PuO2, and AmO2, using solid-state (17)O MAS NMR is reported. An important increase of the spectral resolution is found due to the removal of the dipolar broadening proving the efficiency of this technique for structural analysis. The NMR parameters in these systems with numerous and unpaired 5f electrons were interpreted using an empirical approach. Single-ion model calculations were performed for the first time to determine the z component of electron spin on each of the actinide atoms, which is proportional to the shifts. A similar variation thereof was observed only for the heavier actinides of this study. PMID:24926812

Martel, Laura; Magnani, Nicola; Vigier, Jean-Francois; Boshoven, Jacobus; Selfslag, Chris; Farnan, Ian; Griveau, Jean-Christophe; Somers, Joseph; Fanghänel, Thomas

2014-07-01

343

Identification of lithium-sulfur battery discharge products through 6Li and 33S solid-state MAS and 7Li solution NMR spectroscopy  

NASA Astrophysics Data System (ADS)

6Li and 33S solid-state magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy was used to identify the discharge products in lithium-sulfur (Li-S) battery cathodes. Cathodes were stopped at different potentials throughout battery discharge and measured ex-situ to obtain chemical shifts and T2 relaxation rates of the products formed. The chemical shifts in the spectra of both 6Li and 33S NMR demonstrate that long-chain, soluble lithium polysulfide species formed at the beginning of discharge are indistinguishable from each other (similar chemical shifts), while short-chain, insoluble polysulfide species that form at the end of discharge (presumably Li2S2 and Li2S) have a different chemical shift, thus distinguishing them from the soluble long-chain products. T2 relaxation measurements of discharged cathodes were also performed which resulted in two groupings of T2 rates that follow a trend and support the previous conclusions that long-chain polysulfide species are converted to shorter chain species during discharge. Through the complementary techniques of 1-D 6Li and 33S solid-state MAS NMR spectroscopy, solution 7Li and 1H NMR spectroscopy, and T2 relaxation rate measurements, structural information about the discharge products of Li-S batteries is obtained.

Huff, Laura A.; Rapp, Jennifer L.; Baughman, Jessi A.; Rinaldi, Peter L.; Gewirth, Andrew A.

2015-01-01

344

31P Solid State NMR Studies of Metal Selenophosphates Containing [P2Se6]4-, [P4Se10]4-, [PSe4]3-, [P2Se7]4-, and [P2Se9]4-Ligands  

E-print Network

31P Solid State NMR Studies of Metal Selenophosphates Containing [P2Se6]4-, [P4Se10]4-, [PSe4]3-, [P2Se7]4-, and [P2Se9]4- Ligands Christian G. Canlas, Mercouri G. Kanatzidis, and David P. Weliky P solid-state nuclear magnetic resonance (NMR) spectra of 12 metal-containing selenophosphates have

Weliky, David

345

Solid-state NMR structure characterization of a 13CO-Labeled Ir(I) complex with a P,N-donor ligand including ultrafast MAS methods.  

PubMed

The structural characterization of a (13)CO-labeled Ir(I) complex bearing an P,N-donor ligand (1-[2-(diphenylphosphino)ethyl]pyrazole), [Ir(PyP)((13)CO)Cl] is demonstrated using a series of tailored solid-state NMR techniques based on ultrafast (60 kHz) Magic Angle Spinning (MAS), which facilitates correlations with narrow proton line-widths. Our 1D (1)H MAS and 2D (13)C and (31)P CP-MAS NMR spectra provided structural information similar to that obtained using NMR spectroscopy in solution. We employed high-resolution 2D solid-state correlation spectroscopy ((1)H-(13)C HETCOR, (1)H-(31)P correlation) to characterize the networks of dipolar couplings between protons and carbon/phosphorus. (1)H-(1)H SQ-SQ correlation spectra showed the dipolar contacts between all protons in a similar fashion to its solution counterpart, NOESY. The use of the (1)H single quantum/double quantum experiments made it possible to observe the dipolar-coupling contacts between immediately adjacent protons. Additionally, internuclear (13)CO-(31)P distance measurements were performed using REDOR. The combination of all of these techniques made it possible to obtain comprehensive structural information on the molecule [Ir(PyP)((13)CO)Cl] in the solid state, which is in excellent agreement with the single crystal X-ray structure of the complex, and demonstrates the enormous value of ultrafast MAS NMR techniques for a broad range of future applications. PMID:24992359

Tregubov, Andrey A; Linser, Rasmus; Vuong, Khuong Q; Rawal, Aditiya; Gehman, John D; Messerle, Barbara A

2014-07-21

346

Solid State  

NSDL National Science Digital Library

This is a webpage filled with Solid State learning objects with over 40 lessons in: Semiconductor Diodes, Rectifier Flitering and Regulation, D/A and A/D Converters, Opto Electronic Devices, Operational Amplifiers, Transistors, Thyristors, and Timers.

347

Study of the mechanism of thermal chemical processes in the crystals of YAF tripeptides by means of mass spectrometry and solid state NMR.  

PubMed

Thermal reactions in two Tyr-Ala-Phe (YAF) tripeptide crystals with different molecular packing (monoclinic and hexagonal), distinct stereochemistry of central amino acid (D or L alanine) and specific arrangement of molecules in the crystal lattice (head-to-tail) were investigated. Samples were heated up to 180 °C, while the melting point for YAF crystals is above the 220 °C. Below the melting temperature, in both cases the chemical reactions leading to formation of cyclic dipeptides (YA diketopiperazine) and leaving of phenylalanine were observed. Two possible mechanisms of chemical reaction in the crystal lattice assuming intra- and/or intermolecular pathways were considered. (13)C and (15)N enriched YAF samples were employed to study of mechanism of solid state reactivity using mass spectrometry and advanced solid state NMR techniques (2D DARR (Dipolar Assisted Rotational Resonance) and 2D Double CP (Cross-Polarization) correlations). PMID:24070178

Drabik, Ewelina; Jeziorna, Agata; Bienias, Urszula; Trzeciak-Karlikowska, Katarzyna; Pawlak, Tomasz; Paluch, Piotr; Potrzebowski, Marek J

2013-10-31

348

Alkaline-earth metal carboxylates characterized by 43Ca and 87Sr solid-state NMR: impact of metal-amine bonding.  

PubMed

A series of calcium and strontium complexes featuring aryl carboxylate ligands has been prepared and characterized by alkaline-earth ((43)Ca and (87)Sr) solid-state NMR experiments in a magnetic field of 21.1 T. In the 11 compounds studied as part of this work, a range of coordination motifs are observed including nitrogen atom binding to Ca(2+) and Sr(2+), a binding mode which has not been investigated previously by (43)Ca or (87)Sr solid-state NMR. (43)Ca isotopic enrichment has enabled the full characterization of the (43)Ca electric field gradient (EFG) and chemical shift tensors of the two calcium sites in calcium p-aminosalicylate (Ca(pams)), where both NMR interactions are affected by the presence of a nitrogen atom in the first coordination sphere of one of the metal sites. The (43)Ca isotropic chemical shift is sensitive to the Ca-N distance as exemplified by the NMR parameters of a second form of Ca(pams) and density functional theory (DFT) calculations. Studies of the strontium analogue, Sr(pams), confirm a similar sensitivity of the (87)Sr EFG tensor to the presence or absence of nitrogen in the first coordination sphere. To our knowledge, this is the first systematic (87)Sr NMR study of strontium complexes featuring organic ligands. The |CQ((87)Sr)| values are found to be sensitive to the coordination number about Sr(2+). In general, this work has also established a larger data set of reliable experimental |CQ((43)Ca)| values which correlate well with those obtained using gauge-including projector-augmented-wave (GIPAW) DFT calculations. It is found that the use of a recently recommended quadrupole moment for (43)Ca, -44.4 mbarn, improves the agreement with experimental values. This contribution lays the groundwork for the interpretation of (43)Ca and (87)Sr NMR spectra of more challenging systems, particularly where nitrogen-alkaline earth metal bonding is occurring. PMID:24359541

Burgess, Kevin M N; Xu, Yang; Leclerc, Matthew C; Bryce, David L

2014-01-01

349

Nanoscale spatial resolution probes for scanning thermal microscopy of solid state materials  

NASA Astrophysics Data System (ADS)

Scanning thermal microscopy (SThM) uses micromachined thermal sensors integrated in a force sensing cantilever with a nanoscale tip that can be highly useful for exploration of thermal management of nanoscale semiconductor devices as well as mapping of surface and subsurface properties of related materials. Whereas SThM is capable to image externally generated heat with nanoscale resolution, its ability to map and measure thermal conductivity of materials has been mainly limited to polymers or similar materials possessing low thermal conductivity in the range from 0.1 to 1 W m-1 K-1, with lateral resolution on the order of 1 ?m. In this paper, we use linked experimental and theoretical approaches to analyse thermal performance and sensitivity of the micromachined SThM probes in order to expand their applicability to a broader range of nanostructures from polymers to semiconductors and metals. We develop physical models of interlinked thermal and electrical phenomena in these probes and their interaction with the sample on the mesoscopic length scale of few tens of nm and then validate these models using experimental measurements of the real probes, which provided the basis for analysing SThM performance in exploration of nanostructures. Our study then highlights critical features of these probes, namely, the geometrical location of the thermal sensor with respect to the probe apex, thermal conductance of the probe to the support base, heat conduction to the surrounding gas, and the thermal conductivity of tip material adjacent to the apex. It furthermore allows us to propose a novel design of the SThM probe that incorporates a multiwall carbon nanotube or similar high thermal conductivity graphene sheet material with longitudinal dimensions on micrometre length scale positioned near the probe apex that can provide contact areas with the sample on the order of few tens of nm. The new sensor is predicted to provide greatly improved spatial resolution to thermal properties of nanostructures as well as to expand the sensitivity of the SThM probe to materials with heat conductivity values up to 100-1000 W m-1 K-1.

Tovee, P.; Pumarol, M.; Zeze, D.; Kjoller, Kevin; Kolosov, O.

2012-12-01

350

Determination of Structural Topology of a Membrane Protein in Lipid -Bilayers using Polarization Optimized Experiments (POE) for Static and MAS Solid State NMR Spectroscopy  

PubMed Central

The low sensitivity inherent to both the static and magic angle spinning techniques of solid-state NMR (ssNMR) spectroscopy has thus far limited the routine application of multidimensional experiments to determine the structure of membrane proteins in lipid bilayers. Here, we demonstrate the advantage of using a recently developed class of experiments, polarization optimized experiments (POE), for both static and MAS spectroscopy to achieve higher sensitivity and substantial time-savings for 2D and 3D experiments. We used sarcolipin, a single pass membrane protein, reconstituted in oriented bicelles (for oriented ssNMR) and multilamellar vesicles (for MAS ssNMR) as a benchmark. The restraints derived by these experiments are then combined into a hybrid energy function to allow simultaneous determination of structure and topology. The resulting structural ensemble converged to a helical conformation with a backbone RMSD ? 0.44 Å, a tilt angle of 24° ± 1°, and an azimuthal angle of 55° ± 6°. This work represents a crucial first step toward obtaining high-resolution structures of large membrane proteins using combined multidimensional O-ssNMR and MAS-ssNMR. PMID:23963722

Mote, Kaustubh R.; Gopinath, T.; Veglia, Gianluigi

2013-01-01

351

Tilt and Azimuthal Angles of a Transmembrane Peptide: A Comparison between Molecular Dynamics Calculations and Solid-State NMR Data of Sarcolipin in Lipid Membranes  

PubMed Central

We report molecular dynamics simulations in the explicit membrane environment of a small membrane-embedded protein, sarcolipin, which regulates the sarcoplasmic reticulum Ca-ATPase activity in both cardiac and skeletal muscle. In its monomeric form, we found that sarcolipin adopts a helical conformation, with a computed average tilt angle of 28 ± 6° and azymuthal angles of 66 ± 22°, in reasonable accord with angles determined experimentally (23 ± 2° and 50 ± 4°, respectively) using solid-state NMR with separated-local-field experiments. The effects of time and spatial averaging on both 15N chemical shift anisotropy and 1H/15N dipolar couplings have been analyzed using short-time averages of fast amide out-of-plane motions and following principal component dynamic trajectories. We found that it is possible to reproduce the regular oscillatory patterns observed for the anisotropic NMR parameters (i.e., PISA wheels) employing average amide vectors. This work highlights the role of molecular dynamics simulations as a tool for the analysis and interpretation of solid-state NMR data. PMID:19413970

Shi, Lei; Cembran, Alessandro; Gao, Jiali; Veglia, Gianluigi

2009-01-01

352

Study of host-guest interactions in benzodiazacoronands by means of solid state NMR spectroscopy, X-ray diffraction and quantum mechanical computations.  

PubMed

In this work we present solid state data for five host-guest complexes formed by N-(4,19-dioxo-2,8,15,21-tetraoxa-5,18-diazatricyclohexacosa-1(25),9(14),10,12,22(26),23-hexaen-26-yl)-benzamide (1) belonging to the group of benzodiazacoronands, achiral compounds for which chiral crystals were found (J. Kalisiak and J. Jurczak, Cryst. Growth Des., 2006, 6, 20). The X-ray structure was resolved for four of them. It was found that 1 crystallizes in P2(1)/c, P1 and P2(1)/n achiral space groups. Differentiation of molecular packing and the presence of guest molecules within the crystal lattice were analyzed with solid state NMR. An attempt was made to correlate changes in (13)C ?(ii) and (15)N ?(ii) chemical shift tensor values, obtained from analysis of spinning sidebands of 1D and 2D (2D PASS) NMR spectra, with changes in the strength of hydrogen bonding. Quantum mechanical DFT GIAO calculations of NMR shielding parameters carried out on structures with coordinates taken from XRD were employed for signals assignment and verification of structural constraints. PMID:21384038

Nowicka, Katarzyna; Bujacz, Anna; Paluch, Piotr; Sobczuk, Adam; Jeziorna, Agata; Ciesielski, W?odzimierz; Bujacz, Grzegorz D; Jurczak, Janusz; Potrzebowski, Marek J

2011-04-14

353

Solid state NMR spectroscopy as a precise tool for assigning the tautomeric form and proton position in the intramolecular bridges of o-hydroxy Schiff bases.  

PubMed

Two analogous Schiff bases, (S,E)-2-((1-hydroxy-3-methyl-1,1-diphenylbutan-2-ylimino)methyl)phenol (1) and (S,Z)-2-hydroxy-6-((1-hydroxy-3-methyl-1,1-diphenylbutan-2-ylamino)methylene)cyclohexa-2,4-dienone (2), exist in the solid state as phenol-imine and keto-amine tautomers, respectively. Their crystal structures were solved using the X-ray diffraction method. Sample 1 forms orthorhombic crystals of space group P2(1)2(1)2(1), while 2 forms monoclinic crystals of space group P2(1). In each sample, one molecule is in the asymmetric unit of the crystal structure. One-dimensional and two-dimensional solid state NMR techniques were used for structure assignment and for inspection of the (13)C and (15)N ?(ii) of the chemical shift tensor (CST) values. NMR study indicates that the span (? = ?(11)-?(33)) and the skew (? = 3(?(22)-?(iso)/?) are extremely sensitive to change in the tautomeric form of the Schiff bases. Theoretical calculations of NMR shielding parameters for 1 and 2 and a model compound with reduced aliphatic residue were performed using the GIAO method with B3LYP functional and 6-311++g(d,p) basis sets. From comparative analysis of the experimental and theoretical parameters, it was concluded that the position of hydrogen in the intramolecular bridge has tremendous influence on (13)C and (15)N CST parameters. Inspection of ? and ? parameters allowed for the establishment of the nature of the hydrogen bonding and the assignment of the equilibrium proton position in the intramolecular bridges in the solid state. PMID:21049987

Jaworska, Magdalena; Hrynczyszyn, Pawe? B; We?niak, Miros?aw; Wojtczak, Andrzej; Nowicka, Katarzyna; Krasi?ski, Grzegorz; Kassassir, Hassan; Ciesielski, W?odzimierz; Potrzebowski, Marek J

2010-12-01

354

Structure and Topology of the Huntingtin 1–17 Membrane Anchor by a Combined Solution and Solid-State NMR Approach  

PubMed Central

The very amino-terminal domain of the huntingtin protein is directly located upstream of the protein’s polyglutamine tract, plays a decisive role in several important properties of this large protein and in the development of Huntington’s disease. This huntingtin 1–17 domain is on the one hand known to markedly increase polyglutamine aggregation rates and on the other hand has been shown to be involved in cellular membrane interactions. Here, we determined the high-resolution structure of huntingtin 1–17 in dodecyl phosphocholine micelles and the topology of its helical domain in oriented phosphatidylcholine bilayers. Using two-dimensional solution NMR spectroscopy the low-energy conformations of the polypeptide were identified in the presence of dodecyl phosphocholine detergent micelles. In a next step a set of four solid-state NMR angular restraints was obtained from huntingtin 1–17 labeled with 15N and 2H at selected sites. Of the micellar ensemble of helical conformations only a limited set agrees in quantitative detail with the solid-state angular restraints of huntingtin 1–17 obtained in supported planar lipid bilayers. Thereby, the solid-state NMR data were used to further refine the domain structure in phospholipid bilayers. At the same time its membrane topology was determined and different motional regimes of this membrane-associated domain were explored. The pronounced structural transitions of huntingtin 1–17 upon membrane-association result in a ?-helical conformation from K6 to F17, i.e., up to the very start of the polyglutamine tract. This amphipathic helix is aligned nearly parallel to the membrane surface (tilt angle ?77°) and is characterized by a hydrophobic ridge on one side and an alternation of cationic and anionic residues that run along the hydrophilic face of the helix. This arrangement facilitates electrostatic interactions between huntingtin 1–17 domains and possibly with the proximal polyglutamine tract. PMID:23931318

Michalek, Matthias; Salnikov, Evgeniy S.; Bechinger, Burkhard

2013-01-01

355

Alkaline earth chloride hydrates: chlorine quadrupolar and chemical shift tensors by solid-state NMR spectroscopy and plane wave pseudopotential calculations.  

PubMed

A series of alkaline earth chloride hydrates has been studied by solid-state (35/37)Cl NMR spectroscopy in order to characterize the chlorine electric field gradient (EFG) and chemical shift (CS) tensors and to relate these observables to the structure around the chloride ions. Chlorine-35/37 NMR spectra of solid powdered samples of pseudopolymorphs (hydrates) of magnesium chloride (MgCl(2).6H(2)O), calcium chloride (CaCl(2).2H(2)O), strontium chloride (SrCl(2), SrCl(2).2H(2)O, and SrCl(2).6H(2)O), and barium chloride (BaCl(2).2H(2)O) have been acquired under stationary and magic-angle spinning conditions in magnetic fields of 11.75 and 21.1 T. Powder X-ray diffraction was used as an additional tool to confirm the purity and identity of the samples. Chlorine-35 quadrupolar coupling constants (C(Q)) range from essentially zero in cubic anhydrous SrCl(2) to 4.26+/-0.03 MHz in calcium chloride dihydrate. CS tensor spans, Omega, are between 40 and 72 ppm, for example, Omega= 45+/-20 ppm for SrCl(2).6H(2)O. Plane wave-pseudopotential density functional theory, as implemented in the CASTEP program, was employed to model the extended solid lattices of these materials for the calculation of their chlorine EFG and nuclear magnetic shielding tensors, and allowed for the assignment of the two-site chlorine NMR spectra of barium chloride dihydrate. This work builds upon our current understanding of the relationship between chlorine NMR interaction tensors and the local molecular and electronic structure, and highlights the particular sensitivity of quadrupolar nucleus solid-state NMR spectroscopy to the differences between various pseudopolymorphic structures in the case of strontium chloride. PMID:17385204

Bryce, David L; Bultz, Elijah B

2007-01-01

356

Determination of Multiple ?-Torsion Angles in Proteins by Selective and Extensive 13C Labeling and Two-Dimensional Solid-State NMR  

NASA Astrophysics Data System (ADS)

We describe an approach to efficiently determine the backbone conformation of solid proteins that utilizes selective and extensive 13C labeling in conjunction with two-dimensional magic-angle-spinning NMR. The selective 13C labeling approach aims to reduce line broadening and other multispin complications encountered in solid-state NMR of uniformly labeled proteins while still enhancing the sensitivity of NMR spectra. It is achieved by using specifically labeled glucose or glycerol as the sole carbon source in the protein expression medium. For amino acids synthesized in the linear part of the biosynthetic pathways, [1- 13C]glucose preferentially labels the ends of the side chains, while [2- 13C]glycerol labels the C ? of these residues. Amino acids produced from the citric-acid cycle are labeled in a more complex manner. Information on the secondary structure of such a labeled protein was obtained by measuring multiple backbone torsion angles ? simultaneously, using an isotropic-anisotropic 2D correlation technique, the HNCH experiment. Initial experiments for resonance assignment of a selectively 13C labeled protein were performed using 15N- 13C 2D correlation spectroscopy. From the time dependence of the 15N- 13C dipolar coherence transfer, both intraresidue and interresidue connectivities can be observed, thus yielding partial sequential assignment. We demonstrate the selective 13C labeling and these 2D NMR experiments on a 8.5-kDa model protein, ubiquitin. This isotope-edited NMR approach is expected to facilitate the structure determination of proteins in the solid state.

Hong, Mei

1999-08-01

357

Crystal Structures and Vibrational and Solid-State (CPMAS) NMR Spectroscopy of Some Bis(triphenylphosphine)silver(I) Sulfate, Selenate and Phosphate Systems.  

SciTech Connect

The complexes [Ag2(PPh3)4EO4].2H2O(E=S, Se) (1,2), [Ag(PPh3)2HEO4].H2O (E=S, Se)(3,4) and [Ag9PPh3)2H2PO4].2EtOH (5) have been prepared and studied by X-ray crystallography and by infrared and solid-state 13C and 31 P cross-polarization, magic-angle-spinning (CPMAS) NMR spectroscopy.

Bowmaker, Graham A.; Hanna, John V.; Rickard, Clifton E.; Lipton, Andrew S.

2001-01-01

358

Solid-state Zn-67 NMR Spectroscopic Studies and ab initio Molecular Orbital Calculations on a Synthetic Analogue of Carbonic Anhydrase.  

SciTech Connect

The tris(pyrazolyl)hydroborato zinc complexes [TpBut,Me]ZnX (where X = Br, Cl, and OH) have been examined by low temperature solid-state 67Zn NMR spectroscopy. The value of the quadrupole coupling constant, Cq, for the zinc increased monotonically with the electronegativity of the bound substituent X, e.g. Br < Cl << OH. Calculations on the methylimidazole complex [(MeImH)3Zn(OH)]+ as a model for the active site of carbonic anhydrase indicate that the computed electric field gradient tensor is in good agreement with the experimental and calculated values for [TpBut,Me]ZnOH.

Lipton, Andrew S.; Bergquist, Catherine; Parkin, Gerard; Ellis, Paul D.

2003-04-02

359

Quantification of composition and domain sizes of industrial poly(phthalamide)/poly(dimethylsiloxane) block copolymers using different 1H solid state NMR methods.  

PubMed

We have applied several 1H solid state NMR techniques to obtain structural information on industrial silicone copolymers as thermoplastic elastomers that proved difficult to be analysed by conventional techniques. Static measurements were applied to achieve the separation between mobile and rigid parts. To get structural information fast magic angle spinning at 25 kHz in combination with a high field of 700 MHz was used. 1H spin diffusion was applied to determine the domain sizes of the micro phase-separated polymer components. PMID:12469811

Kretschmer, Axel; Drake, Robert; Neidhoefer, Michael; Wilhelm, Manfred

2002-01-01

360

Determining hydrogen-bond interactions in spider silk with 1H-13C HETCOR fast MAS solid-state NMR and DFT proton chemical shift calculations.  

PubMed

Two-dimensional (2D) (1)H-(13)C heteronuclear correlation (HETCOR) solid-state NMR spectra collected with fast magic angle spinning (MAS) are used in conjunction with density functional theory (DFT) proton chemical shift calculations to determine the hydrogen-bonding strength for ordered ?-sheet and disordered 310-helical structures in spider dragline silk. The hydrogen-bond strength is determined to be identical for both structures in spider silk with a 1.83-1.84 Å NH···OC hydrogen-bond distance. PMID:23774714

Holland, Gregory P; Mou, Qiushi; Yarger, Jeffery L

2013-07-28

361

Solid-state 13C NMR study of banana liquid crystals - 1: Two different alkyl tail-group packing environments in the B7 phase  

NASA Astrophysics Data System (ADS)

Solid-state 13C nuclear magnetic resonance (NMR) measurements were performed for the B7 phase of the banana-shaped molecule P-8-O-PIMB(NO 2). In this phase, NMR chemical shifts assigned to five methylene carbons on the alkyl tail appear as at least seven peaks, indicating that the two alkyl tails within a single molecule have different packing structures. Combined CP/MAS and PST/MAS measurements show that one of the alkyl tails has dense packing with low molecular mobility and the other has loose packing with high molecular mobility. Thus, it can be concluded that both the polar bent and molecular axes are tilted toward the layer in the B7 phase of P-8-O-PIMB(NO 2), exhibiting molecular leaning.

Kurosu, Hiromichi; Nakanishi, Saki; Kimura, Saori; Kang, Sungmin; Li, Xiaodong; Sone, Masato; Watanabe, Junji

2012-01-01

362

Effect of critical molecular weight of PEO in epoxy/EPO blends as characterized by advanced DSC and solid-state NMR  

NASA Astrophysics Data System (ADS)

The differential scanning calorimetry (DSC) and solid state NMR have been used to systematically study the length scale of the miscibility and local dynamics of the epoxy resin/poly(ethylene oxide) (ER/PEO) blends with different PEO molecular weight. By DSC, we found that the diffusion behavior of PEO with different Mw is an important factor in controlling these behaviors upon curing. We further employed two-dimensional 13C-1HPISEMA NMR experiment to elucidate the possible weak interaction and detailed local dynamics in ER/PEO blends. The CH2O group of PEO forms hydrogen bond with hydroxyl proton of cured-ER ether group, and its local dynamics frozen by such interaction. Our finding indicates that molecular weight (Mw) of PEO is a crucial factor in controlling the miscibility, chain dynamics and hydrogen bonding interaction in these blends.

Wang, Xiaoliang; Lu, Shoudong; Sun, Pingchuan; Xue, Gi

2013-03-01

363

Specific molecular structure changes and radical evolution during biomass-polyethylene terephthalate co-pyrolysis detected by (13)C and (1)H solid-state NMR.  

PubMed

Co-pyrolysis of biomass with polyethylene terephthalate (PET) was studied as a function of blend ratio and co-pyrolysis temperature by (13)C and (1)H solid-state nuclear magnetic resonance (NMR). The (13)C NMR spectra showed that upon heating to 400°C in presence of the biomass, the formation of crystallites in PET was completely suppressed and that at higher temperatures there was increased formation and growth of the polycyclic aromatic hydrocarbons (PAHs). This change in the PET degradation behaviour was attributed to the presence of radicals formed in char from biomass. The measurement of the (1)H-T1 relaxation enabled monitoring the changes in the concentrations of radicals formed, as a function of the blend ratios and the co-pyrolysis temperatures. It indicated that the increase in the radical concentrations correlated well with the increased degradation of the PET and growth of PAHs. PMID:25146317

Ko, Kwang-Hyun; Sahajwalla, Veena; Rawal, Aditya

2014-10-01

364

Time-dependent column performance of cholesterol-based stationary phases for HPLC by LC characterization and solid-state NMR spectroscopy.  

PubMed

Three different cholesterol-based stationary phases were investigated with respect to their time-dependent separation behavior. The examined stationary phases differ in the used spacer molecule and the synthesis route and were used under routine laboratory conditions over a period of two years. The chromatographic behavior of the three phases was determined by using a standard reference material in addition to a separation of a steroid mixture. The surface chemistry and the modification of these with the chemically bonded moiety were investigated with nuclear magnetic resonance (NMR) spectroscopy and elemental analysis. Through applying different techniques we determined changes in retention and selectivity; solid-state NMR spectra showed changes in the surface chemistry dependent on the synthesis route. Superior long-term stability was observed for the undecanoate-cholesterol (UDC-Chol) column in terms of hydrophobic retentiveness and selectivity. PMID:22761135

Yeman, Helen; Nicholson, Tim M; Friebolin, Volker; Steinhauser, Lisa; Matyska, Maria T; Pesek, Joseph J; Albert, Klaus

2012-07-01

365

Solid-state 13C NMR study of banana liquid crystals - 2: Alkyl tail-group packing environments in the hexagonal columnar phase  

NASA Astrophysics Data System (ADS)

Solid-state 13C nuclear magnetic resonance (NMR) measurements were performed in order to obtain the packing structure of alkyl tail in the hexagonal columnar phase of the banana-shaped N(1,7)-S16 molecule. In this phase, NMR chemical shifts assigned to the internal methylene carbons at an amorphous state appear as two peaks, indicating that the two alkyl tails are placed under two different chemical environments. From combined cross-polarization/magic-angle spinning and pulse saturation transfer/magical-angle spinning measurements, two alkyl tails were found to have the different mobility. Such two different environments are not unusual in conventional mesophases, but in the hexagonal columnar phase formed by cylindrical columns composed of enclosed smectic layers; one of the alkyl tails is located inside and the other is located outside the columnar structure.

Kurosu, Hiromichi; Endo, Yumi; Kimura, Saori; Hashimoto, Tomoko; Harada, Motoi; Lee, Eun-Woo; Sone, Masato; Watanabe, Junji; Kang, Sungmin

2013-05-01

366

Structural features of a bituminous coal and their changes during low-temperature oxidation and loss of volatiles investigated by advanced solid-state NMR spectroscopy  

USGS Publications Warehouse

Quantitative and advanced 13C solid-state NMR techniques were employed to investigate (i) the chemical structure of a high volatile bituminous coal, as well as (ii) chemical structural changes of this coal after evacuation of adsorbed gases, (iii) during oxidative air exposure at room temperature, and (iv) after oxidative heating in air at 75 ??C. The solid-state NMR techniques employed in this study included quantitative direct polarization/magic angle spinning (DP/MAS) at a high spinning speed of 14 kHz, cross polarization/total sideband suppression (CP/TOSS), dipolar dephasing, CH, CH2, and CHn selection, 13C chemical shift anisotropy (CSA) filtering, two-dimensional (2D) 1H-13C heteronuclear correlation NMR (HETCOR), and 2D HETCOR with 1H spin diffusion. With spectral editing techniques, we identified methyl CCH 3, rigid and mobile methylene CCH2C, methine CCH, quaternary Cq, aromatic CH, aromatic carbons bonded to alkyls, small-sized condensed aromatic moieties, and aromatic C-O groups. With direct polarization combined with spectral-editing techniques, we quantified 11 different types of functional groups. 1H-13C 2D HETCOR NMR experiments indicated spatial proximity of aromatic and alkyl moieties in cross-linked structures. The proton spin diffusion experiments indicated that the magnetization was not equilibrated at a 1H spin diffusion time of 5 ms. Therefore, the heterogeneity in spatial distribution of different functional groups should be above 2 nm. Recoupled C-H long-range dipolar dephasing showed that the fraction of large charcoal-like clusters of polycondensed aromatic rings was relatively small. The exposure of this coal to atmospheric oxygen at room temperature for 6 months did not result in obvious chemical structural changes of the coal, whereas heating at 75 ??C in air for 10 days led to oxidation of coal and generated some COO groups. Evacuation removed most volatiles and caused a significant reduction in aliphatic signals in its DP/MAS spectrum. DP/MAS, but not CP/MAS, allowed us to detect the changes during low-temperature oxidation and loss of volatiles. These results demonstrate the applicability of advanced solid-state NMR techniques in chemical characterization of coal. ?? 2010 American Chemical Society.

Mao, J.-D.; Schimmelmann, A.; Mastalerz, M.; Hatcher, P.G.; Li, Y.

2010-01-01

367

Some studies on a solid state sulfur probe for coal gasification systems  

NASA Technical Reports Server (NTRS)

Measurements on the solid electrolyte cell (Ar + H(2) + H(2)S/CaS + CaF(2) + (Pt)//CaF(2)//(Pt) + CaF(2) + CaS/H(2) + H(2)+Ar) show that the emf of the cell is directly related to the difference in sulfur potentials established at the Ar + H(2) + H(2)S/electrode interfaces. The electrodes convert the sulfur potential gradient across the calcium fluoride electrolyte into an equivalent fluorine potential gradient. Response time of the probe varies from approximately 9 hr at 990 K to 2.5 hr at 1225 K. The conversion of calcium sulfide and/or calcium fluoride into calcium oxide is not a problem anticipated in commercial coal gasification systems. Suggestions are presented for improving the cell for such commercial applications.

Jacob, K. T.; Rao, D. B.; Nelson, H. G.

1977-01-01

368

A Technique for Increasing the Sensitivity of a Solid-State Fission Probe  

NASA Technical Reports Server (NTRS)

A small silicon p-n junction wafer, when coated with uranium 235, can be used as a compact fission probe for low power flux and power mapping. Because of the inverse relation between the magnitude of a neutron-induced fission pulse and the inherent capacitance of the detecting element (capacitance is proportional to area), the size, and hence the sensitivity, of the semiconductor detector has been limited. New developments in the field of semiconductor detectors have made it possible to fabricate large area detectors which are essentially free from the capacitance effect. However, preliminary results indicate that they are much more susceptible to radiation damage than the detectors described in this report and as such may not be suitable for flux mapping. increasing the sensitivity cannot be accomplished by simply fabricating a larger detector. It has been observed that by combining the silicon p-n junction wafers in a series configuration the capacitance effect can be bypassed, and a fission probe can be made with a resultant increase in sensitivity by a factor of ten while sustaining only a minor decrease in pulse height. Analysis further indicates that for n silicon wafers in series, if n(C(sub i)) + C(sub c)/C(sub b) less than 0.1 where C(sub i) and C(sub c) are the preamplifier input and cable capacitances, respectively, and C(sub b) is the junction capacitance of a single silicon wafer, there should be no substantial reduction in pulse height due to series circuitry.

Steinberg, Robert

1961-01-01

369

The application of solid-state NMR spectroscopy to study candesartan cilexetil (TCV-116) membrane interactions. Comparative study with the AT1R antagonist drug olmesartan.  

PubMed

??1 receptor (AT1R) antagonists exert their antihypertensive effects by preventing the vasoconstrictive hormone AngII to bind to the AT1 receptor. It has been proposed that these biological effects are mediated through a two-step mechanism reaction. In the first step, they are incorporated in the core of the lipid bilayers and in the second step they reach the active site of the receptor through lateral diffusion. In this model, drug/membrane interactions are key elements for the drugs achieving inhibition at the AT1 receptor. In this work, the interactions of the prodrug candesartan cilexetil (TCV-116) with lipid bilayers are studied at molecular detail. Solid-state (13)C-CP/MAS, 2D (1)H-(1)H NOESY NMR spectroscopy and in silico calculations are used. TCV-116 and olmesartan, another drug which acts as an AT1R antagonist are compared for their dynamic effects in lipid bilayers using solid-state (2)H-NMR. We find a similar localization of TCV-116 compared to other AT1 antagonists in the intermediate polar region. In addition, we can identify specific local interactions. These interactions may be associated in part with the discrete pharmacological profiles observed for different antagonists. PMID:24946142

Ntountaniotis, Dimitrios; Kellici, Tahsin; Tzakos, Andreas; Kolokotroni, Pinelopi; Tselios, Theodore; Becker-Baldus, Johanna; Glaubitz, Clemens; Lin, Sonyan; Makriyannis, Alexandros; Mavromoustakos, Thomas

2014-10-01

370

Association of 2-acylaminopyridines and benzoic acids. Steric and electronic substituent effect studied by XRD, solution and solid-state NMR and calculations  

NASA Astrophysics Data System (ADS)

Eight single crystal X-ray structures, solid-state NMR spectroscopic, and theoretical studies utilizing QTAIM methodology were used to characterize the 2-acyl (alkyl in acyl = methyl, ethyl, t-butyl, and 1-adamantyl) amino-6-R-pyridine/4-R?-benzoic acid (R,R? = H or Me) cocrystals. As expected among alkyl groups 1-adamantyl due to its bulkiness has the most significant effect on the relative positions of molecules in cocrystals. In addition, the subtle electronic and steric effects by the methyl substituents were observed. The theoretical calculations with full geometry optimizations are in agreement with the experimental findings (geometry, energy of hydrogen bonds). Based on the crystal structures and calculations it is concluded that p-methyl substituent in benzoic acid increase the hydrogen bond accepting ability of the CO oxygen and decreases the hydrogen bond donating ability of OH proton. The 15N solid-state (CP MAS) NMR chemical shifts prove that molecules in cocrystal are held together by hydrogen bonding. The biggest variation in the 15N chemical shift of acylamino nitrogen can be related with the size of the alkyl group in acyl moiety.

O?mia?owski, Borys; Kolehmainen, Erkki; Ejsmont, Krzysztof; Ikonen, Satu; Valkonen, Arto; Rissanen, Kari; Nonappa

2013-12-01

371

1D and 2D solid state NMR investigations of the framework structure of As-synthesized AlPO4-14.  

PubMed

The framework structure of As-synthesized AlPO4-14 has been investigated with a combination of different one-dimensional 27Al and 31P solid state NMR techniques and 27Al/31P double resonance methods. The results are found to be fully consistent with the assumed structural model. 27Al MAS and DOR experiments at three different magnetic field strengths together with simulations show the presence of two tetrahedral sites, one pentacoordinated and one octahedral aluminum site. The 27Al quadrupolar coupling constants and the 31P isotropic chemical shifts of the tetrahedral sites correlate well with tetrahedral shear-strain parameters and mean P-O-Al bond angles, respectively. These correlations allow one to assign all of the NMR resonances to specific T-sites in the proposed framework structure. The assignments are then further confirmed by the application of three different two-dimensional heteronuclear correlation methods (i.e., 27Al-->31P TEDOR, CP, and INEPT) which reveal the connectivities between AlOx and PO4 polyhedra. The two-dimensional INEPT experiment is applied here for the first time in the solid state. PMID:9477440

Fyfe, C A; Meyer zu Altenschildesche, H; Wong-Moon, K C; Grondey, H; Chezeau, J M

1997-12-01

372

Accurate measurements of 13C-13C distances in uniformly 13C-labeled proteins using multi-dimensional four-oscillating field solid-state NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Application of sets of 13C-13C internuclear distance restraints constitutes a typical key element in determining the structure of peptides and proteins by magic-angle-spinning solid-state NMR spectroscopy. Accurate measurements of the structurally highly important 13C-13C distances in uniformly 13C-labeled peptides and proteins, however, pose a big challenge due to the problem of dipolar truncation. Here, we present novel two-dimensional (2D) solid-state NMR experiments capable of extracting distances between carbonyl (13C') and aliphatic (13Caliphatic) spins with high accuracy. The method is based on an improved version of the four-oscillating field (FOLD) technique [L. A. Straasø, M. Bjerring, N. Khaneja, and N. C. Nielsen, J. Chem. Phys. 130, 225103 (2009)] which circumvents the problem of dipolar truncation, thereby offering a base for accurate extraction of internuclear distances in many-spin systems. The ability to extract reliable accurate distances is demonstrated using one- and two-dimensional variants of the FOLD experiment on uniformly 13C,15N-labeled-L-isoleucine. In a more challenging biological application, FOLD 2D experiments are used to determine a large number of 13C'-13Caliphatic distances in amyloid fibrils formed by the SNNFGAILSS fibrillating core of the human islet amyloid polypeptide with uniform 13C,15N-labeling on the FGAIL fragment.

Straasø, Lasse Arnt; Nielsen, Jakob Toudahl; Bjerring, Morten; Khaneja, Navin; Nielsen, Niels Chr.

2014-09-01

373

Revealing the fine details of functionalized silica surfaces by solid-state NMR and adsorption isotherm measurements: the case of fluorinated stationary phases for liquid chromatography.  

PubMed

The structural and chromatographic characterization of two novel fluorinated mesoporous materials prepared by covalent reaction of 3-(pentafluorophenyl)propyldimethylchlorosilane and perfluorohexylethyltrichlorosilane with 2.5??m fully porous silica particles is reported. The adsorbents were characterized by solid state (29)Si, (13)C, and (19)F?NMR spectroscopy, low-temperature nitrogen adsorption, elemental analysis (C and F), and various chromatographic measurements, including the determination of adsorption isotherms. The structure and abundance of the different organic surface species, as well as the different silanol types, were determined. In particular, the degree of so-called horizontal polymerization, that is, Si-O-Si bridging parallel to the silica surface due to the reaction, under "quasi-dry" conditions, of trifunctional silanizing agents with the silica surface was quantified. Significant agreement was found between the information provided by solid-state NMR, elemental analysis, and excess isotherms regarding the amount of surface residual silanol groups, on the one hand, and the degree of surface functionalization, on the other. Finally, the kinetic performance of the fluorinated materials as separation media for applications in near-ultrahigh-performance liquid chromatography was evaluated. At reduced velocities of about 5.5 (ca. 600?bar backpressure at room temperature) with 3?mm diameter columns and toluene as test compound, reduced plate heights on the order of 2 were obtained on columns of both adsorbents. PMID:24890919

Ciogli, Alessia; Simone, Patrizia; Villani, Claudio; Gasparrini, Francesco; Laganà, Aldo; Capitani, Donatella; Marchetti, Nicola; Pasti, Luisa; Massi, Alessandro; Cavazzini, Alberto

2014-06-23

374

NMR probe for dynamic-angle spinning  

SciTech Connect

We describe the design of a probe for dynamic-angle spinning (DAS) NMR experiments, comprised of a spinning cylindrical sample holder whose axis may be reoriented rapidly between discrete directions within the bore of a superconducting magnet. This allows the refocusing of nuclear spin magnetization that evolves under anisotropic interactions such as chemical shift anisotropy and quadrupolar coupling, providing high resolution NMR spectra for quadrupolar nuclei in solid materials. The probe includes an axial air delivery system to bearing and drive jets which support and spin a rotor containing the sample. Axis reorientation is accomplished with a pulley attached to the probehead and coupled to a stepping motor outside of the magnet. The choice of motor and gear ratio is based on an analysis of the moments of inertia of the motor and load, the desired angular resolution, and simplicity of design. Control of angular accuracy and precision are discussed, as well as the efficiency of radiofrequency irradiation and detection. High resolution DAS spectra of oxygen-17 and aluminum-27 nuclei in polycrystalline minerals illustrate the experimental capabilities.

Mueller, K.T.; Chingas, G.C.; Pines, A. (Materials Sciences Division, Lawrence Berkeley Laboratory and Department of Chemistry, University of California, Berkeley, California 94720 (USA))

1991-06-01

375

Nanotube array method for studying lipid-induced conformational changes of a membrane protein by solid-state NMR.  

PubMed

Anodic aluminum oxide substrates with macroscopically aligned homogeneous nanopores of 80 nm in diameter enable two-dimensional, solid-state nuclear magnetic resonance studies of lipid-induced conformational changes of uniformly (15)N-labeled Pf1 coat protein in native-like bilayers. The Pf1 helix tilt angles in bilayers composed of two different lipids are not entirely governed by the membrane thickness but could be rationalized by hydrophobic interactions of lysines at the bilayer interface. The anodic aluminum oxide alignment method is applicable to a broader repertoire of lipids versus bicelle bilayer mimetics currently employed in solid-state nuclear magnetic resonance of oriented samples, thus allowing for elucidation of the role played by lipids in shaping membrane proteins. PMID:25564843

Marek, Antonin; Tang, Wenxing; Milikisiyants, Sergey; Nevzorov, Alexander A; Smirnov, Alex I

2015-01-01

376

NMR standard probe for precision measurement of the free proton NMR frequency  

SciTech Connect

The authors have designed and constructed a special NMR standard probe using a spehrical pure water sample to determine the free proton NMR frequency f{sub p} at high field and an accuracy of 0.04 ppm has been achieved. Since the proton gyromagnetic ratio {gamma}{sub p} is less well known ({approx}0.1 ppm), the free proton NMR frequency measured by the probe may serve as a calibration standard for the magnetic field B. The standard probe can be used at various magnetic field values without introducing any additional magnetic perturbations. The probe is designed in such a way that a cylindrical sample or a small NMR probe can be inserted to replace the 1 cm diameter spherical water sample for systematic studies. Other NMR probes can be calibrated easily against the standard probe using a calibration form. Results will be presented and discussed.

Fei, X.; Hughes, V.W.; Prigl, R.

1995-04-01

377

Tracing bacterial metabolism using multi-nuclear (1H, 2H, and 13C) Solid State NMR: Realizing an Idea Initiated by James Scott  

NASA Astrophysics Data System (ADS)

Approximately 6 years ago, while at the Geophysical Laboratory, James Scott became interested in the application of Solid State Nuclear Magnetic Resonance Spectroscopy to study bacterial metabolism. As often happens, other experiments intervened and the NMR experiments were not pursued. We have revisited Jame's question and find that using a multi-nuclear approach (1H, 2H, and 13C Solid State NMR) on laboratory cell culture has some distinct advantages. Our experiments involved batch cultures of E. coli (MG1655) harvested at stationary phase. In all experiments the growth medium consisted of MOPS medium for enterobacteria, where the substrate is glucose. In one set of experiments, 10 % of the water was D2O; in another 10 % of the glucose was per-deuterated. The control experiment used both water and glucose at natural isotopic abundance. A kill control of dead E. coli immersed in pure D2O for an extended period exhibited no deuterium incorporation. In both deuterium enriched experiments, considerable incorporation of deuterium into E. coli's biomolecular constituents was detected via 2H Solid State NMR. In the case of the D2O enriched experiment, 58 % of the incorporated deuterium is observed in a sharp peak at a frequency of 0.31 ppm, consistent with D incorporation in the cell membrane lipids, the remainder is observed in a broad peak at a higher frequency (centered at 5.4 ppm, but spanning out to beyond 10 ppm) that is consistent with D incorporation into predominantly DNA and RNA. In the case of the D-glucose experiments, 61 % of the deuterium is observed in a sharp resonance peak at 0.34 ppm, also consistent with D incorporation into membrane lipids, the remainder of the D is observed at a broad resonance peak centered at 4.3 ppm, consistent with D enrichment in glycogen. Deuterium abundance in the E. coli cells grown in 10 % D2O is nearly 2X greater than that grown with 10 % D-glucose. Very subtle differences are observed in both the 1H and 13C solid-state NMR experiments, most notably in the spectral region corresponding to glycogen H and C, respectively. Interestingly, whereas in both experiments the predominant site of incorporation was in the membrane lipids, the line width of the aliphatic-D resonance in the D2O enriched experiment is 67 % wider than that observed in the D-glucose enriched experiment. This difference could be due to greater residual 1H-2H dipolar coupling in membrane lipids synthesized with 10 % D2O due to D being incorporated during NADP(D) reduction of the fatty acid precursor during synthesis and the H-glucose being the source of carbon and hydrogen starting with acetyl-CoA. In the case of the D-glucose experiment, the narrower absorption line may be consistent with individual FA's being more homogeneously deuterated. Analysis of the membrane lipids is currently being performed via GCMS in order to gain potentially more insight to guide interpretation of the 2H solid state NMR spectra.

Cody, G.; Fogel, M. L.; Jin, K.; Griffen, P.; Steele, A.; Wang, Y.

2011-12-01

378

Brönsted and Lewis acidity of the BF3/gamma-Al2O3 alkylation catalyst as revealed by solid-state NMR spectroscopy and DFT quantum chemical calculations.  

PubMed

Multinuclear solid-state NMR techniques and DFT quantum chemical calculations were employed to investigate the detailed structure of acid sites on the BF3/gamma-Al2O3 alkylation catalyst. The NMR experiment results indicate that gaseous BF3 is able to react with the hydroxyl groups present on the surface of gamma-Al2O3, leading to the formation of new Brönsted and Lewis acid sites. The 1H/11B and 1H/27Al TRAPDOR (TRAnsfer of Population in DOuble Resonance) experiments suggest that the 3.7 ppm signal in 1H NMR spectra of the BF3/gamma-Al2O3 catalyst is due to a bridging B-OH-Al group that acts as a Brönsted acid site of the catalyst. On the other hand, a Lewis acid site on the surface of the catalysts, as revealed by 31P MAS and 31P/27Al TRAPDOR NMR of adsorbed trimethylphosphine, is associated with three-coordinate -OBF2 species. 13C NMR of adsorbed 2-13C-acetone indicates that the Brönsted acid strength of the catalyst is slightly stronger than that of zeolite HZSM-5 but still weaker than that of 100% H2SO4, which is in good agreement with theoretical prediction. In addition, DFT calculations also reveal the detailed structure of various acid sites formed on the BF3/gamma-Al2O3 catalyst and the interaction of probe molecules with these sites. PMID:16852633

Yang, Jun; Zheng, Anmin; Zhang, Mingjin; Luo, Qing; Yue, Yong; Ye, Chaohui; Lu, Xin; Deng, Feng

2005-07-14

379

Dynamic structure of pharaonis phoborhodopsin (sensory rhodopsin II) and complex with a cognate truncated transducer as revealed by site-directed 13C solid-state NMR.  

PubMed

We have recorded (13)C nuclear magnetic resonance (NMR) spectra of [3-(13)C]Ala, [1-(13)C]Val-labeled pharaonis phoborhodopsin (ppR or sensory rhodopsin II) incorporated into egg PC (phosphatidylcholine) bilayer, by means of site-directed high-resolution solid-state NMR techniques. Seven (13)C NMR signals from transmembrane alpha-helices were resolved for [3-(13)C]Ala-ppR at almost the same positions as those of bacteriorhodopsin (bR), except for the suppressed peaks in the loop regions in spite of the presence of at least three Ala residues. In contrast, (13)C NMR signals from the loops were visible from [1-(13)C]Val-ppR but their peak positions of the transmembrane alpha-helices are not always the same between ppR and bR. The motional frequency of the loop regions in ppR was estimated as 10(5) Hz in view of the suppressed peaks from [3-(13)C]Ala-ppR due to interference with proton decoupling frequency. We found that conformation and dynamics of ppR were appreciably altered by complex formation with a cognate truncated transducer pHtr II (1-159). In particular, the C-terminal alpha-helix protruding from the membrane surface is involved in the complex formation and subsequent fluctuation frequency is reduced by one order of magnitude. PMID:12586370

Arakawa, Tadashi; Shimono, Kazumi; Yamaguchi, Satoru; Tuzi, Satoru; Sudo, Yuki; Kamo, Naoki; Saitô, Hazime

2003-02-11

380

Solid-state ²°⁷Pb CP-MAS NMR of lead(II) compounds for the structural study of molecular routes to lead-based perovskite-phase materials  

Microsoft Academic Search

In this paper, the authors discuss the results of a study of the solid-state ²°⁷Pb NMR data for crystalline Pb(OâCCRâOH)â compounds, crystalline perovskite-phase PbMOâ (M = Ti, Zr), and an amorphous PbTiOâ precursor and proton T⁠relaxation times to investigate the potential of this technique to follow solid-state structural changes.

Alan D. Irwin; Clive D. Chandler; M. J. Hampden-Smith; R. Assink

1994-01-01

381

Solid-state {sup 207}Pb CP-MAS NMR of lead(II) compounds for the structural study of molecular routes to lead-based perovskite-phase materials  

SciTech Connect

In this paper, the authors discuss the results of a study of the solid-state {sup 207}Pb NMR data for crystalline Pb(O{sub 2}CCR{sub 2}OH){sub 2} compounds, crystalline perovskite-phase PbMO{sub 3} (M = Ti, Zr), and an amorphous PbTiO{sub 3} precursor and proton T{sub 1} relaxation times to investigate the potential of this technique to follow solid-state structural changes.

Irwin, A.D. [Butler Univ., Indianapolis, IN (United States); Chandler, C.D.; Hampden-Smith, M.J. [Univ. of New Mexico, Albuquerque, NM (United States); Assink, R. [Sandia National Lab., Albuquerque, NM (United States)

1994-03-16

382

Acidity of mesoporous MoO(x)/ZrO2 and WO(x)/ZrO2 materials: a combined solid-state NMR and theoretical calculation study.  

PubMed

The acidity of mesoporous MoO(x)/ZrO2 and WO(x)/ZrO2 materials was studied in detail by multinuclear solid-state NMR techniques as well as DFT quantum chemical calculations. The 1H MAS NMR experiments clearly revealed the presence of two different types of strong Brønsted acid sites on both MoO(x)/ZrO2 and WO(x)/ZrO2 mesoporous materials, which were able to prontonate adsorbed pyrine-d5 (resulting in 1H NMR signals at chemical shifts in the range 16-19 ppm) as well as adsorbed trimethylphosphine (giving rise to 31P NMR signal at ca. 0 ppm). The 13C NMR of adsorbed 2-(13)C-acetone indicated that the average Brønsted acid strength of the two mesoporous materials was stronger than that of zeolite HZSM-5 but still weaker than that of 100% H2SO4, which was in good agreement with theoretical predictions. The quantum chemical calculations revealed the detailed structures of the two distinct types of Brønsted acid sites formed on the mesoporous MoO(x)/ZrO2 and WO(x)/ZrO2. The existence of both monomer and oligomer Mo (or W) species containing a Mo-OH-Zr (or W-OH-Zr) bridging OH group was confirmed with the former having an acid strength close to zeolite HZSM-5, with the latter having an acid strength similar to sulfated zirconia. On the basis of our NMR experimental and theoretical calculation results, a possible mechanism was proposed for the formation of acid sites on these mesoporous materials. PMID:16771312

Xu, Jun; Zheng, Anmin; Yang, Jun; Su, Yongchao; Wang, Jiqing; Zeng, Danlin; Zhang, Mingjin; Ye, Chaohui; Deng, Feng

2006-06-01

383

The Diversity of the Liquid Ordered (Lo) Phase of Phosphatidylcholine/Cholesterol Membranes: A Variable Temperature Multinuclear Solid-State NMR and X-Ray Diffraction Study  

PubMed Central

To investigate the properties of a pure liquid ordered (Lo) phase in a model membrane system, a series of saturated phosphatidylcholines combined with cholesterol were examined by variable temperature multinuclear (1H, 2H, 13C, 31P) solid-state NMR spectroscopy and x-ray scattering. Compositions with cholesterol concentrations ?40 mol %, well within the Lo phase region, are shown to exhibit changes in properties as a function of temperature and cholesterol content. The 2H-NMR data of both cholesterol and phospholipids were used to more accurately map the Lo phase boundary. It has been established that the gel-Lo phase coexistence extends to 60 mol % cholesterol and a modified phase diagram is presented. Combined 1H-, 2H-, 13C-NMR, and x-ray scattering data indicate that there are large changes within the Lo phase region, in particular, 1H-magic angle spinning NMR and wide-angle x-ray scattering were used to examine the in-plane intermolecular spacing, which approaches that of a fluid L? phase at high temperature and high cholesterol concentrations. Although it is well known for cholesterol to broaden the gel-to-fluid transition temperature, we have observed, from the 13C magic angle spinning NMR data, that the glycerol region can still undergo a “melting”, though this is broadened with increasing cholesterol content and changes with phospholipid chain length. Also from 2H-NMR order parameter data it was observed that the effect of temperature on chain length became smaller with increasing cholesterol content. Finally, from the cholesterol order parameter, it has been previously suggested that it is possible to determine the degree to which cholesterol associates with different phospholipids. However, we have found that by taking into account the relative temperature above the phase boundary this relationship may not be correct. PMID:16537550

Clarke, James A.; Heron, Andrew J.; Seddon, John M.; Law, Robert V.

2006-01-01

384

Solid-State NMR Enhanced by Dynamic Nuclear Polarization as a novel Tool for Ribosome Structural Biology  

E-print Network

half of the NMR rotor for easy removal after centrifugation. The rotor holder is screwed into the 'core and limit imbalances during ultracentrifugation. The core chambers in the SW-28 / SW32 and Ti-45 designs

385

Solid state NMR of a molecular self-assembly: multinuclear approach to the cyanuric acid-melamine system.  

PubMed

[see structure]. Trinuclear MAS NMR, involving naturally abundant (13C, 15N) and easily deuterated (2H) nuclei, is shown to offer newer opportunities to study molecular self-assembly in noncrystalline supramolecular systems. PMID:11405745

Damodaran, K; Sanjayan, G J; Rajamohanan, P R; Ganapathy, S; Ganesh, K N

2001-06-14

386

YPdSn and YPd{sub 2}Sn: Structure, {sup 89}Y solid state NMR and {sup 119}Sn Moessbauer spectroscopy  

SciTech Connect

The stannides YPdSn and YPd{sub 2}Sn were synthesized by high-frequency melting of the elements in sealed tantalum tubes. Both structures were refined on the basis of single crystal X-ray diffractometer data: TiNiSi type, Pnma, a=715.4(1), b=458.8(1), c=789.1(1) pm, wR2=0.0461, 510 F{sup 2} values, 20 variables for YPdSn and MnCu{sub 2}Al type, Fm3 Macron m, a=671.44(8), wR2=0.0740, 55 F{sup 2} values, 5 parameters for YPd{sub 2}Sn. The yttrium atoms in the new stannide YPdSn are coordinated by two tilted Pd{sub 3}Sn{sub 3} hexagons (ordered AlB{sub 2} superstructure). In the Heusler phase YPd{sub 2}Sn each yttrium atom has octahedral tin coordination and additionally eight palladium neighbors. The cubic site symmetry of yttrium is reflected in the {sup 119}Sn Moessbauer spectrum which shows no quadrupole splitting. In contrast, YPdSn shows a single signal at {delta}=1.82(1) mm/s subjected to quadrupole splitting of {Delta}E{sub Q}=0.93(1) mm/s. Both compounds have been characterized by high-resolution {sup 89}Y solid state NMR spectroscopy, which indicates the presence of strong Knight shifts. The spectrum of YPd{sub 2}Sn is characterized by an unusually large linewidth, suggesting the presence of a Knight shift distribution reflecting local disordering effects. The range of {sup 89}Y Knight shifts of several binary and ternary intermetallic yttrium compounds is briefly discussed. - Graphical abstract: YPdSn and YPd{sub 2}Sn: Structure, {sup 89}Y solid state NMR and {sup 119}Sn Moessbauer spectroscopy. Highlights: Black-Right-Pointing-Pointer Synthesis and structure of ternary stannides YPdSn and YPd{sub 2}Sn. Black-Right-Pointing-Pointer {sup 119}Sn Moessbauer spectroscopic investigation of YPdSn and YPd{sub 2}Sn. Black-Right-Pointing-Pointer {sup 89}Y solid state NMR of intermetallics.

Hoeting, Christoph [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster, Corrensstrasse 30, D-48149 Muenster (Germany); Eckert, Hellmut [Institut fuer Physikalische Chemie, Universitaet Muenster, Corrensstrasse 30, D-48149 Muenster (Germany); Langer, Thorsten; Schellenberg, Inga [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster, Corrensstrasse 30, D-48149 Muenster (Germany); Poettgen, Rainer, E-mail: pottgen@uni-muenster.de [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster, Corrensstrasse 30, D-48149 Muenster (Germany)

2012-06-15

387

Molecular level investigations of phosphate sorption on corundum (?-Al2O3) by 31P solid state NMR, ATR-FTIR and quantum chemical calculation  

NASA Astrophysics Data System (ADS)

Phosphate sorption at the corundum (?-Al2O3)/water interface was investigated as a function of phosphate concentration (0.1-1 mM) and pH (3-11) by 31P solid state NMR spectroscopy, ATR-FTIR, and quantum chemical calculation. The 31P NMR spectra indicate that under these experimental conditions phosphate adsorbs onto corundum mainly as inner-sphere complexes that yield a peak at ?P = -2.8 ppm with full width at half maximum (FWHM) of 9.2 ppm, with a small amount aluminum phosphate surface precipitates as suggested by an NMR signal observed from ?P = -12 to -20 ppm. We employed 31P{27Al} rotational echo adiabatic passage double resonance (REAPDOR) to further analyze the phosphate adsorption samples prepared at pH 5 and 9 in order to determine the phosphate/Al coordination. To aid interpretation of the NMR data, a series of bidentate and monodentate structural models of phosphate adsorbed on corundum (0 0 1) and (0 1 2) surfaces were calculated using density function theory (DFT). By comparing the experimental REAPDOR curves and those simulated from these models, we can assign the dominant peaks to bidentate binuclear surface complexes. Formation of bidentate binuclear surface complexes is supported by the ATR/FTIR spectra combined with DFT calculation, which further suggests a mixture of non-protonated bidentate and mono-protonated bidentate surface complexes on the corundum surface at pH 5. At pH 9, both NMR and ATR/FTIR indicate the formation of bidentate surface complexes on corundum surface.

Li, Wei; Pierre-Louis, Andro-Marc; Kwon, Kideok D.; Kubicki, James D.; Strongin, Daniel R.; Phillips, Brian L.

2013-04-01

388

Solid state 13C NMR analysis of shales and coals from Laramide Basins. Final report, March 1, 1995--March 31, 1996  

SciTech Connect

This Western Research Institute (WRI) jointly sponsored research (JSR) project augmented and complemented research conducted by the University of Wyoming Institute For Energy Research for the Gas Research Institute. The project, {open_quotes}A New Innovative Exploitation Strategy for Gas Accumulations Within Pressure Compartments,{close_quotes} was a continuation of a project funded by the GRI Pressure Compartmentalization Program that began in 1990. That project, {open_quotes}Analysis of Pressure Chambers and Seals in the Powder River Basin, Wyoming and Montana,{close_quotes} characterized a new class of hydrocarbon traps, the discovery of which can provide an impetus to revitalize the domestic petroleum industry. In support of the UW Institute For Energy Research`s program on pressure compartmentalization, solid-state {sup 13}C NMR measurements were made on sets of shales and coals from different Laramide basins in North America. NMR measurements were made on samples taken from different formations and depths of burial in the Alberta, Bighorn, Denver, San Juan, Washakie, and Wind River basins. The carbon aromaticity determined by NMR was shown to increase with depth of burial and increased maturation. In general, the NMR data were in agreement with other maturational indicators, such as vitrinite reflectance, illite/smectite ratio, and production indices. NMR measurements were also obtained on residues from hydrous pyrolysis experiments on Almond and Lance Formation coals from the Washakie Basin. These data were used in conjunction with mass and elemental balance data to obtain information about the extent of carbon aromatization that occurs during artificial maturation. The data indicated that 41 and 50% of the original aliphatic carbon in the Almond and Lance coals, respectively, aromatized during hydrous pyrolysis.

Miknis, F.P.; Jiao, Z.S.; Zhao, Hanqing; Surdam, R.C.

1998-12-31

389

Fluid Mechanical Matching of H+-ATP Synthase Subunit c-Ring with Lipid Membranes Revealed by 2H Solid-State NMR  

PubMed Central

The F1Fo-ATP synthase utilizes the transmembrane H+ gradient for the synthesis of ATP. Fo subunit c-ring plays a key role in transporting H+ through Fo in the membrane. We investigated the interactions of Escherichia coli subunit c with dimyristoylphosphatidylcholine (DMPC-d54) at lipid/protein ratios of 50:1 and 20:1 by means of 2H-solid-state NMR. In the liquid-crystalline state of DMPC, the 2H-NMR moment values and the order parameter (SCD) profile were little affected by the presence of subunit c, suggesting that the bilayer thickness in the liquid-crystalline state is matched to the transmembrane hydrophobic surface of subunit c. On the other hand, hydrophobic mismatch of subunit c with the lipid bilayer was observed in the gel state of DMPC. Moreover, the viscoelasticity represented by a square-law function of the 2H-NMR relaxation was also little influenced by subunit c in the fluid phase, in contrast with flexible nonionic detergents or rigid additives. Thus, the hydrophobic matching of the lipid bilayer to subunit c involves at least two factors, the hydrophobic length and the fluid mechanical property. These findings may be important for the torque generation in the rotary catalytic mechanism of the F1Fo-ATPse molecular motor. PMID:18310246

Kobayashi, Masatoshi; Struts, Andrey V.; Fujiwara, Toshimichi; Brown, Michael F.; Akutsu, Hideo

2008-01-01

390

Perturbation of nuclear spin polarizations in solid state NMR of nitroxide-doped samples by magic-angle spinning without microwaves  

SciTech Connect

We report solid state {sup 13}C and {sup 1}H nuclear magnetic resonance (NMR) experiments with magic-angle spinning (MAS) on frozen solutions containing nitroxide-based paramagnetic dopants that indicate significant perturbations of nuclear spin polarizations without microwave irradiation. At temperatures near 25 K, {sup 1}H and cross-polarized {sup 13}C NMR signals from {sup 15}N,{sup 13}C-labeled L-alanine in trinitroxide-doped glycerol/water are reduced by factors as large as six compared to signals from samples without nitroxide doping. Without MAS or at temperatures near 100 K, differences between signals with and without nitroxide doping are much smaller. We attribute most of the reduction of NMR signals under MAS near 25 K to nuclear spin depolarization through the cross-effect dynamic nuclear polarization mechanism, in which three-spin flips drive nuclear polarizations toward equilibrium with spin polarization differences between electron pairs. When T{sub 1e} is sufficiently long relative to the MAS rotation period, the distribution of electron spin polarization across the nitroxide electron paramagnetic resonance lineshape can be very different from the corresponding distribution in a static sample at thermal equilibrium, leading to the observed effects. We describe three-spin and 3000-spin calculations that qualitatively reproduce the experimental observations.

Thurber, Kent R., E-mail: thurberk@niddk.nih.gov; Tycko, Robert [Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520 (United States)] [Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520 (United States)

2014-05-14

391

Solid-state 13C NMR investigations of cyclophanes: [2.2]paracyclophane and 1,8-dioxa[8](2,7)pyrenophane.  

PubMed

Solid-state NMR (ssNMR) and ab initio quantum mechanical calculations are used in order to understand and to better characterize the molecular conformation and properties of [2.2]paracyclophane and 1,8-dioxa[8](2,7)pyrenophane. Both molecules are cyclophanes, consisting of an aromatic ring assembly and a cyclic aliphatic chain connected to both ends of the aromatic portion. The aliphatic chain causes curvature in the six-membered aromatic ring structures. This led us to examine how the ring strain due to curvature affects the chemical shifts. Using X-ray structures of both [2.2]paracyclophane and 1,8-dioxa[8](2,7)pyrenophane as our starting model, we calculate the chemical shielding tensors and compare these data with those collected from the (13)C ssNMR FIREMAT experiment. We define curvature of [2.2]paracyclophane and 1,8-dioxa[8](2,7)pyrenophane using the ?-orbital axis vector (POAV) pyramidalization angle (?(p)). PMID:22480194

Halling, Merrill D; Unikela, Kiran Sagar; Bodwell, Graham J; Grant, David M; Pugmire, Ronald J

2012-05-31

392

?-Sheet Nanocrystalline Domains Formed from Phosphorylated Serine-Rich Motifs in Caddisfly Larval Silk: A Solid State NMR and XRD Study  

PubMed Central

Adhesive silks spun by aquatic caddisfly (order Trichoptera) larvae are used to build both intricate protective shelters and food harvesting nets underwater. In this study, we use 13C and 31P solid-state Nuclear Magnetic Resonance (NMR) and Wide Angle X-ray Diffraction (WAXD) as tools to elucidate molecular protein structure of caddisfly larval silk from the species Hesperophylax consimilis. Caddisfly larval silk is a fibroin protein based biopolymer containing mostly repetitive amino acid motifs. NMR and X-ray results provide strong supporting evidence for a structural model in which phosphorylated serine repeats (pSX)4 complex with divalent cations Ca2+ and Mg2+ to form rigid nanocrystalline ?-sheet structures in caddisfly silk. 13C NMR data suggests that both phosphorylated serine and neighboring valine residues exist in a ?-sheet secondary structure conformation while glycine and leucine residues common in GGX repeats likely reside in random coil conformations. Additionally, 31P chemical shift anisotropy (CSA) analysis indicates that the phosphates on phosphoserine residues are doubly ionized, and are charge-stabilized by divalent cations. Positively charged arginine side chains also likely play a role in charge stabilization. Finally, WAXD results finds that the silk is at least 7–8% crystalline, with ?-sheet inter-plane spacings of 3.7 and 4.5 Å. PMID:23452243

Addison, J. Bennett; Ashton, Nicholas N.; Weber, Warner S.; Stewart, Russell J.; Holland, Gregory P.; Yarger, Jeffery L.

2013-01-01

393

Interaction of the neuropeptide met-enkephalin with zwitterionic and negatively charged bicelles as viewed by 31P and 2H solid-state NMR.  

PubMed

The interaction of the neuropeptide methionine-enkephalin (Menk) with bicelles was investigated by solid-state NMR. Bicelles composed of dimyristoylphosphatidylcholine (DMPC) and dicaproylphosphatidylcholine (DCPC) were modified to investigate the effect of the lipid headgroup and electrostatic charges on the association with Menk. A total of 10 mol % of DMPC was replaced by zwitterionic phosphatidylethanolamine (DMPE), anionic phosphatidylglycerol (DMPG), or phosphatidylserine (DMPS). The preparation of DMPE-doped bicelles (Bic/PE) is reported for the first time. The (31)P and (2)H NMR results revealed changes in the lipid dynamics when Menk interacts with the bicellar systems. (2)H NMR experiments showed a disordering effect of Menk on the lipid chains in all the bicelles except Bic/PG, whereas the study of the choline headgroups indicated a decreased order of the lipids only in Bic/PE and Bic/PG. Our results suggest that the insertion depth of Menk into bicelles is modulated by their composition, more specifically by the balance between hydrophobic and electrostatic interactions. Menk would be buried at the lipid polar/apolar interface, the depth of penetration into the hydrophobic membrane core following the scaling Bic > Bic/PE > Bic/PS at the slightly acidic pH used in this study. The peptide would not insert into the bilayer core of Bic/PG and would rather remain at the surface. PMID:12829487

Marcotte, Isabelle; Dufourc, Erick J; Ouellet, Marise; Auger, Michèle

2003-07-01

394

High-resolution structure of the Shigella type-III secretion needle by solid-state NMR and cryo-electron microscopy.  

PubMed

We introduce a general hybrid approach for determining the structures of supramolecular assemblies. Cryo-electron microscopy (cryo-EM) data define the overall envelope of the assembly and rigid-body orientation of the subunits while solid-state nuclear magnetic resonance (ssNMR) chemical shifts and distance constraints define the local secondary structure, protein fold and inter-subunit interactions. Finally, Rosetta structure calculations provide a general framework to integrate the different sources of structural information. Combining a 7.7-Å cryo-EM density map and 996 ssNMR distance constraints, the structure of the type-III secretion system needle of Shigella flexneri is determined to a precision of 0.4?Å. The calculated structures are cross-validated using an independent data set of 691 ssNMR constraints and scanning transmission electron microscopy measurements. The hybrid model resolves the conformation of the non-conserved N terminus, which occupies a protrusion in the cryo-EM density, and reveals conserved pore residues forming a continuous pattern of electrostatic interactions, thereby suggesting a mechanism for effector protein translocation. PMID:25264107

Demers, Jean-Philippe; Habenstein, Birgit; Loquet, Antoine; Kumar Vasa, Suresh; Giller, Karin; Becker, Stefan; Baker, David; Lange, Adam; Sgourakis, Nikolaos G

2014-01-01

395

Interaction between histidine and Zn(II) metal ions over a wide pH as revealed by solid-state NMR spectroscopy and DFT calculations.  

PubMed

The interactions between histidine and metal species play essential roles in a wide range of important biological processes including enzymes catalysis and signal transduction. In this work, solid-state NMR techniques were employed to determine the interaction between histidine and Zn(II) from pH 3.5 to 14. 2D homo- and heteronuclear correlation NMR experiments were utilized to extract the (1)H, (13)C, and (15)N chemical shifts in various histidine-Zn(II) binding complexes. Several histidine-Zn(II) binding models were proposed on the basis of experimental results as well as DFT theoretical calculations. No direct interaction could be found between biprotonated histidine and Zn(II) at acidic pH. At pH 7.5, one zinc ion could be hexa-coordinated with two histidine molecules on C', N? and deprotonated N?1 sites. As the pH increases to 11-14, both of the N?1 and N?2 sites could be deprotonated as acceptors to be bound to either Zn(II) or water. All of these findings give a comprehensive set of benchmark values for NMR parameters and structural geometries in variable histidine-Zn(II) binding complexes over a wide pH range and might provide insights into the structure-property relationship of histidine-metal complexes in biological metalloproteins. PMID:23841698

Zhou, Lei; Li, Shenhui; Su, Yongchao; Yi, Xianfeng; Zheng, Anmin; Deng, Feng

2013-08-01

396

High-resolution structure of the Shigella type-III secretion needle by solid-state NMR and cryo-electron microscopy  

NASA Astrophysics Data System (ADS)

We introduce a general hybrid approach for determining the structures of supramolecular assemblies. Cryo-electron microscopy (cryo-EM) data define the overall envelope of the assembly and rigid-body orientation of the subunits while solid-state nuclear magnetic resonance (ssNMR) chemical shifts and distance constraints define the local secondary structure, protein fold and inter-subunit interactions. Finally, Rosetta structure calculations provide a general framework to integrate the different sources of structural information. Combining a 7.7-Å cryo-EM density map and 996 ssNMR distance constraints, the structure of the type-III secretion system needle of Shigella flexneri is determined to a precision of 0.4?Å. The calculated structures are cross-validated using an independent data set of 691 ssNMR constraints and scanning transmission electron microscopy measurements. The hybrid model resolves the conformation of the non-conserved N terminus, which occupies a protrusion in the cryo-EM density, and reveals conserved pore residues forming a continuous pattern of electrostatic interactions, thereby suggesting a mechanism for effector protein translocation.

Demers, Jean-Philippe; Habenstein, Birgit; Loquet, Antoine; Kumar Vasa, Suresh; Giller, Karin; Becker, Stefan; Baker, David; Lange, Adam; Sgourakis, Nikolaos G.

2014-09-01

397

Interaction of the Neuropeptide Met-Enkephalin with Zwitterionic and Negatively Charged Bicelles as Viewed by 31P and 2H Solid-State NMR  

PubMed Central

The interaction of the neuropeptide methionine-enkephalin (Menk) with bicelles was investigated by solid-state NMR. Bicelles composed of dimyristoylphosphatidylcholine (DMPC) and dicaproylphosphatidylcholine (DCPC) were modified to investigate the effect of the lipid headgroup and electrostatic charges on the association with Menk. A total of 10 mol % of DMPC was replaced by zwitterionic phosphatidylethanolamine (DMPE), anionic phosphatidylglycerol (DMPG), or phosphatidylserine (DMPS). The preparation of DMPE-doped bicelles (Bic/PE) is reported for the first time. The 31P and 2H NMR results revealed changes in the lipid dynamics when Menk interacts with the bicellar systems. 2H NMR experiments showed a disordering effect of Menk on the lipid chains in all the bicelles except Bic/PG, whereas the study of the choline headgroups indicated a decreased order of the lipids only in Bic/PE and Bic/PG. Our results suggest that the insertion depth of Menk into bicelles is modulated by their composition, more specifically by the balance between hydrophobic and electrostatic interactions. Menk would be buried at the lipid polar/apolar interface, the depth of penetration into the hydrophobic membrane core following the scaling Bic > Bic/PE > Bic/PS at the slightly acidic pH used in this study. The peptide would not insert into the bilayer core of Bic/PG and would rather remain at the surface. PMID:12829487

Marcotte, Isabelle; Dufourc, Erick J.; Ouellet, Marise; Auger, Michèle

2003-01-01

398

Solid-state NMR study of various mono- and divalent cation forms of the natural zeolite natrolite.  

PubMed

Here we present the one-dimensional (29)Si and (27)Al MAS NMR and two-dimensional (27)Al MQMAS and DQF-STMAS NMR spectra of the monovalent (Na(+), K(+), Rb(+), Cs(+) and NH4(+)) and divalent (Ca(2+), Sr(2+) and Ba(2+)) cation forms of the natural zeolite natrolite (framework type NAT) with complete Si-Al ordering over the crystallographically distinct tetrahedral sites and with the same hydration state (hydrated, partially dehydrated or fully dehydrated). In the case of monovalent cation-exchanged natrolites, the differences in their crystal symmetry evidenced by (29)Si MAS NMR were found to be in good agreement with those determined by crystallographic analyses. However, (27)Al DQF-STMAS NMR spectroscopy shows the presence of two distinct Al sites in dehydrated K-NAT, Rb-NAT and NH4-NAT, suggesting that their actual crystal symmetry is lower than the reported one (i.e., orthorhombic Fdd2). The MAS NMR results also show that the space group of hydrated Ca-NAT is lower than that (monoclinic F1d1) of hydrated scolecite, the natural calcium counterpart of natrolite, which is also the case with hydrated Sr-NAT and Ba-NAT. We believe that the unexpected diversity in the crystal symmetry of natrolite caused by exchange of various mono- and divalent ions, as well as by dehydration, may be inherently due to the high framework flexibility of this natural zeolite. PMID:23588621

Park, Min Bum; Vicente, Aurélie; Fernandez, Christian; Hong, Suk Bong

2013-05-28

399

The investigation of membrane binding by amphibian peptide agonists of CCK2R using (31)P and (2)H solid-state NMR.  

PubMed

It has been proposed that some neuropeptides may be anchored to the cell membranes prior to attaching to the adjacent active sites of transmembrane receptors. The three amphibian skin neuropeptides signiferin 1 [RLCIPYIIPC(OH)] (smooth muscle active and immunomodulator), riparin 1.1 [[RLCIPVIFPC(OH)] (immunomodulator) and rothein 1 [SVSNIPESIGF(OH)] (immunomodulator) act via CCK2 transmembrane receptors. A combination of (31)P and (2)H solid state NMR studies of each of these three peptides in eukaryotic phospholipid models at 25°C shows that rothein 1 does not interact with the membrane at all. In contrast, both of the cyclic disulfides signiferin 1 and riparin 1.1 interact with phospholipid head groups and partially penetrate into the upper leaflet of the model bilayer, but to different extents. These interactions are not sufficiently effective to cause disruption of the lipid bilayer since the peptides are not antimicrobial, anticancer, antifungal nor active against enveloped viruses. PMID:24582625

Sherman, Patrick J; Separovic, Frances; Bowie, John H

2014-05-01

400

Design and characterization of a calixarene inclusion compound for calibration of long-range carbon-fluorine distance measurements by solid-state NMR  

PubMed Central

An inexpensive, easily synthesized calixarene:fluorotoluene host:guest inclusion complex has been designed for optimization and calibration of solid-state NMR measurements of carbon-fluorine distances using Rotational Echo DOuble Resonance (REDOR). Complexation of the fluorotoluene with the calixarene host separates the molecules such that simple two-spin behavior is observed for one site with a 4.08 Å carbon-fluorine distance. Fluorotoluene dynamics within the calixarene matrix causes motional averaging of the dipolar couplings that make it possible to easily optimize REDOR experiments and test their accuracy for relatively long distance measurements (> 6.6 Å). This provides a new tool for accurate REDOR measurements of long carbon-fluorine distances, which have important applications in the characterization of fluorine-containing drugs, proteins, and polymers. PMID:20822943

Fowler, Daniel J.; Khalifah, Peter G.; Thompson, Lynmarie K.

2010-01-01