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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.

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

2010-01-01

2

Fast screening of solid electrolytes: a high throughput solid state NMR probe.  

PubMed

In this article we describe the construction of a high throughput solid state NMR probe for a fast and reliable determination of the NMR line width of a given nuclear species within a solid material. Since the NMR line width scales with the inverse of the mobility of the studied species and hence its ionic conductivity, this approach allows a fast screening of the material's promise as a solid electrolyte. The functionality of the approach is exemplified by the determination of the (7)Li-NMR line width of a set of 30 different liquid and solid Li-containing samples. PMID:23219977

Schiffmann, J G; Kopp, J; Geisler, G; Kröninger, J; van Wüllen, L

2013-02-01

3

Fast-recovery crossed-coil probe for low frequency solid-state NMR  

Microsoft Academic Search

A crossed-coil probe for solid-state NMR with a recovery time of 5 mu s at 10 MHz has been constructed. The transitory Q damping performed on the transmitting coil, together with a simultaneous grounding of the receiving coil, provides a significant reduction in the probe ringing-down time without degradation of the signal-to-noise ratio. Since no particular isolation between the two

G. Floridi; R. Lamanna; S. Cannistraro

1991-01-01

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.

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

2009-01-01

5

A low-E magic angle spinning probe for biological solid state NMR at 750 MHz  

NASA Astrophysics Data System (ADS)

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.

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

2009-04-01

6

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

PubMed Central

Flavins mediate a wide variety of different chemical reactions in biology. To learn how one cofactor can be made to execute different reactions in different enzymes, we are developing solid-state NMR (SSNMR) to probe the flavin electronic structure, via the 15N chemical shift tensor principal values (?ii). We find that SSNMR has superior responsiveness to H-bonds, compared to solution NMR. H-bonding to a model of the flavodoxin active site produced an increase of 10 ppm in the ?11 of N5 although none of the H-bonds directly engage N5, and solution NMR detected only a 4 ppm increase in the isotropic chemical shift (?iso). Moreover SSNMR responded differently to different H-bonding environments as H-bonding with water caused ?11 to decrease by 6 ppm whereas ?iso increased by less than 1 ppm. Our density functional theoretical (DFT) calculations reproduce the observations, validating the use of computed electronic structures to understand how H-bonds modulate the flavin’s reactivity.

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

2011-01-01

7

Cross polarization, radio frequency field homogeneity, and circuit balancing in high field solid state NMR probes  

Microsoft Academic Search

Homogeneous radio frequency (RF) fields are important for sensitivity and efficiency of magnetization transfer in solid state NMR experiments. If the fields are inhomogeneous the cross polarization (CP) experiment transfers magnetization in only a thin slice of sample rather than throughout the entire volume. Asymmetric patterns have been observed in plots of the CP signal versus RF field mismatch for

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

2004-01-01

8

A Simple Single-Coil Double Resonance NMR Probe for Solid State Studies.  

National Technical Information Service (NTIS)

A single coil (Solenoid), nuclear magnetic double resonance sample probe, suited for a wide variety of solid state studies, is described. It was designed to be used in double resonance experiments where it is necessary to generate intense rf magnetic fiel...

M. E. Stoll A. J. Vega R. W. Vaughan

1977-01-01

9

Simple single-coil double resonance NMR probe for solid state studies  

Microsoft Academic Search

A single-coil (solenoid), nuclear magnetic double resonance sample probe, suited for a wide variety of solid state studies, is described. It was designed to be used in double resonance experiments where it is necessary to generate intense rf magnetic fields (rotating components with amplitudes ?50 G) at two widely spaced frequencies and simultaneously to detect microvolt-level signals. Designs for operation

M. E. Stoll; A. J. Vega; R. W. Vaughan

1977-01-01

10

A simple single-coil double resonance NMR probe for solid state studies  

Microsoft Academic Search

A single coil (Solenoid), nuclear magnetic double resonance sample probe, suited for a wide variety of solid state studies, is described. It was designed to be used in double resonance experiments where it is necessary to generate intense rf magnetic fields (rotating components with amplitudes about 50 gauss) at two widely spaced frequencies and to simultaneously detect microvolt-level signals. Designs

M. E. Stoll; A. J. Vega; R. W. Vaughan

1977-01-01

11

Simple single-coil double resonance NMR probe for solid state studies  

Microsoft Academic Search

A single-coil (solenoid), nuclear magnetic double resonance sample probe, suited for a wide variety of solid state studies, is described. It was designed to be used in double resonance experiments where it is necessary to generate intense rf magnetic fields (rotating components with amplitudes ~50 G) at two widely spaced frequencies and simultaneously to detect microvolt-level signals. Designs for operation

M. E. Stoll; A. J. Vega; R. W. Vaughan

1977-01-01

12

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

Microsoft Academic Search

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

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

2007-01-01

13

Probing the nanostructure of bioerodible polyanhydrides with solid-state NMR  

NASA Astrophysics Data System (ADS)

Polyanhydrides are a class of bioerodible polymers with unique properties that make them ideal for drug delivery applications. One of the most interesting properties of these materials is the microphase separation that occurs in copolymers of certain compositions. Microphase separation of copolymers, when coupled with the disparity in degradation rates between two constituent monomers, results in interesting degradation and drug release phenomena that can be exploited to design controlled release devices with tailored release profiles. Solid-state NMR spectroscopy is used to identify the crystalline domains of copolymers of sebacic Acid (SA) and 1,6-bis(p-carboxyphenoxy)hexane (CPH). Proton spin diffusion experiments with carbon detection are used to discern length scales of phase separation in the amorphous regions of the polymer. The data indicate that when the copolymer composition exceeds 75constituent co-monomers, nanoscale domains of the minority component are present, and a weakly segregated block-like nanostructure is obtained. As the copolymer composition nears 50These observations are consistent with solution state NMR data that measure the number-average sequence of the polymer chains.

Kipper, Matt; Hou, Sheng-Shu; Schmidt-Rohr, Klaus; Narasimhan, Balaji

2003-03-01

14

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

15

Probing the structure of metal-substituted molecular sieves by solid-state NMR  

SciTech Connect

Paramagnetic metal ions exert large influences on the NMR spectra of neighboring nuclei. The authors are using these effects to probe metal sites in zeolites and AlPO{sub 4} molecular sieves. In particular, they are studying [Co]-AlPO{sub 4}-5 because similar cobalt substituted AlPO{sub 4} sieves are reported in the literature. They have extended that work to probe the titanium zeolite TS-1 by comparing spectra of normal TS-1 to samples where the titanium has been reduced to the paramagnetic Ti{sup 3+}. This promises to be a useful technique for determining framework substitution in many zeolite systems.

Labouriau, A.; Crawford, S.N.; Ott, K.; Earl, W.L.

1998-08-01

16

Probing the interaction of polyphenols with lipid bilayers by solid-state NMR spectroscopy.  

PubMed

Polyphenols are bioactive natural products that appear to act against a wide range of pathologies. Mechanisms of activity have not been established, but recent studies have suggested that some polyphenols bind to membranes. This study examined the interaction between lipid bilayers and three structurally diverse polyphenols. It was hypothesized that features of the polyphenols such as polarity, molecular size, molecular geometry, and number and arrangement of phenol hydroxyl groups would determine the tendency to interact with the bilayer. The examined compounds included a mixed polyphenol, (-)-epigallocatechin gallate (EGCg); a proanthocyanidin trimer comprising catechin-(4?8)-catechin-(4?8)-catechin (cat?; and a hydrolyzable tannin, 1,2,3,4,6-penta-O-galloyl-?-D-glucopyranose (PGG). These polyphenols were incorporated at different levels into ²H-labeled 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) multilamellar vesicles (MLVs). ³¹P and ²H solid-state NMR experiments were performed to determine the dynamics of the headgroup region and the hydrophobic acyl chain region of the lipid bilayer upon addition of polyphenols. The chemical shift anisotropy (CSA) width of the ³¹P NMR spectra decreased upon addition of polyphenols. Addition of PGG induces a dramatic reduction on the CSA width compared with the control lipid bilayer sample, whereas addition of cat? barely reduces the CSA width. The ²H quadupolar splitting of the lipids also decreased upon addition of polyphenols. At the same concentration, PGG substantially reduced the quadrupolar splitting, whereas cat? barely reduced it when compared with the control sample. From a calculation of the order parameters of the acyl chain region of the lipid bilayer, it was concluded that the hydrophobic part of the lipid bilayer was perturbed by PGG, whereas cat? did not cause large perturbations. The data suggest that the polarity of the polyphenols affects the interaction between tannins and membranes. The interactions may relate to the biological activities of polyphenols. PMID:21574575

Yu, Xueting; Chu, Shidong; Hagerman, Ann E; Lorigan, Gary A

2011-06-22

17

Low temperature probe for dynamic nuclear polarization and multiple-pulse solid-state NMR.  

PubMed

Here, we describe the design and performance characteristics of a low temperature probe for dynamic nuclear polarization (DNP) experiments, which is compatible with demanding multiple-pulse experiments. The competing goals of a high-Q microwave cavity to achieve large DNP enhancements and a high efficiency NMR circuit for multiple-pulse control lead to inevitable engineering tradeoffs. We have designed two probes-one with a single-resonance RF circuit and a horn-mirror cavity configuration for the microwaves and a second with a double-resonance RF circuit and a double-horn cavity configuration. The advantage of the design is that the sample is in vacuum, the RF circuits are locally tuned, and the microwave resonator has a large internal volume that is compatible with the use of RF and gradient coils. PMID:17524687

Cho, HyungJoon; Baugh, Jonathan; Ryan, Colm A; Cory, David G; Ramanathan, Chandrasekhar

2007-08-01

18

Low temperature probe for dynamic nuclear polarization and multiple-pulse solid-state NMR  

NASA Astrophysics Data System (ADS)

Here, we describe the design and performance characteristics of a low temperature probe for dynamic nuclear polarization (DNP) experiments, which is compatible with demanding multiple-pulse experiments. The competing goals of a high-Q microwave cavity to achieve large DNP enhancements and a high efficiency NMR circuit for multiple-pulse control lead to inevitable engineering tradeoffs. We have designed two probes—one with a single-resonance RF circuit and a horn-mirror cavity configuration for the microwaves and a second with a double-resonance RF circuit and a double-horn cavity configuration. The advantage of the design is that the sample is in vacuum, the RF circuits are locally tuned, and the microwave resonator has a large internal volume that is compatible with the use of RF and gradient coils.

Cho, HyungJoon; Baugh, Jonathan; Ryan, Colm A.; Cory, David G.; Ramanathan, Chandrasekhar

2007-08-01

19

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

NASA Astrophysics Data System (ADS)

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.

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

2007-10-01

20

Probing the molecular-level control of aluminosilicate dissolution: A sensitive solid-state NMR proxy for reactive surface area  

NASA Astrophysics Data System (ADS)

For two suites of volcanic aluminosilicate glasses, the accessible and reactive sites for covalent attachment of the fluorine-containing (3,3,3-trifluoropropyl)dimethylchlorosilane (TFS) probe molecule were measured by quantitative 19F nuclear magnetic resonance (NMR) spectroscopy. The first set of samples consists of six rhyolitic and dacitic glasses originating from volcanic activity in Iceland and one rhyolitic glass from the Bishop Tuff, CA. Due to differences in the reactive species present on the surfaces of these glasses, variations in the rate of acid-mediated dissolution (pH 4) for samples in this suite cannot be explained by variations in geometric or BET-measured surface area. In contrast, the rates scale directly with the surface density of TFS-reactive sites as measured by solid-state NMR. These data are consistent with the inference that the TFS-reactive M-OH species on the glass surface, which are known to be non-hydrogen-bonded Q 3 groups, represent loci accessible to and affected by proton-mediated dissolution. The second suite of samples, originating from a chronosequence in Kozushima, Japan, is comprised of four rhyolites that have been weathered for 1.1, 1.8, 26, and 52 ka. The number of TFS-reactive sites per gram increases with duration of weathering in the laboratory for the "Icelandic" samples and with duration of field weathering for both "Icelandic" and Japanese samples. One hypothesis is consistent with these and published modeling, laboratory, and field observations: over short timescales, dissolution is controlled by fast-dissolving sites, but over long timescales, dissolution is controlled by slower-dissolving sites, the surface density of which is proportional to the number of TFS-reactive Q 3 sites. These latter sites are not part of a hydrogen-bonded network on the surface of the glasses, and measurement of their surface site density allows predictions of trends in reactive surface area. The TFS treatment method, which is easily monitored by quantitative 19F solid-state NMR, therefore provides a chemically specific and quantifiable proxy to understand the nature of how sites on dissolving silicates control dissolution. Furthermore, 27Al NMR techniques are shown here to be useful in identifying clays on the glass surfaces, and these methods are therefore effective for quantifying concentrations of weathering impurities. Our interpretations offer a testable hypothesis for the mechanism of proton-promoted dissolution for low-iron aluminosilicate minerals and glasses and suggest that future investigations of reactive surfaces with high-sensitivity NMR techniques are warranted.

Washton, Nancy M.; Brantley, Susan L.; Mueller, Karl T.

2008-12-01

21

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.

2013-01-01

22

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.

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

2014-01-01

23

Reduction of RF-induced sample heating with a scroll coil resonator structure for solid-state NMR probes  

Microsoft Academic Search

Heating due to high power 1H decoupling limits the experimental lifetime of protein samples for solid-state NMR (SSNMR). Sample deterioration can be minimized by lowering the experimental salt concentration, temperature or decoupling fields; however, these approaches may compromise biological relevance and\\/or spectroscopic resolution and sensitivity. The desire to apply sophisticated multiple pulse experiments to proteins therefore motivates the development of

John A. Stringer; Charles E. Bronnimann; Charles G. Mullen; Donghua H. Zhou; Sara A. Stellfox; Ying Li; Evan H. Williams; Chad M. Rienstra

2005-01-01

24

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

Microsoft Academic Search

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

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

2009-01-01

25

Probing transient conformational States of proteins by solid-state r1? relaxation-dispersion NMR spectroscopy.  

PubMed

The function of proteins depends on their ability to sample a variety of states differing in structure and free energy. Deciphering how the various thermally accessible conformations are connected, and understanding their structures and relative energies is crucial in rationalizing protein function. Many biomolecular reactions take place within microseconds to milliseconds, and this timescale is therefore of central functional importance. Here we show that R1? relaxation dispersion experiments in magic-angle-spinning solid-state NMR spectroscopy make it possible to investigate the thermodynamics and kinetics of such exchange process, and gain insight into structural features of short-lived states. PMID:24644028

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

2014-04-22

26

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.

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

2009-01-01

27

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

28

Frontispiece: probing transient conformational States of proteins by solid-state r1? relaxation-dispersion NMR spectroscopy.  

PubMed

In their Communication on page?4312?ff., P. Schanda et?al. describe an NMR method used to probe conformational states of proteins. Information about the exchange kinetics, relative populations, and structures of the short-lived state can be obtained. PMID:24753203

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

2014-04-22

29

Solid-state MAS NMR detection of the oxidation center in TS1 zeolite by in situ probe reaction  

Microsoft Academic Search

In this paper, the oxidation of trimethylphosphine as an in situ probe reaction was performed to monitor the oxidation ability of different Ti species in TS-1 zeolite by 31P MAS NMR spectra, which found for the first time direct evidence about the oxidation center of TS-1 zeolite.

Jinqing Zhuang; Ding Ma; Zhimin Yan; Feng Deng; Xiumei Liu; Xiuwen Han; Xinhe Bao; X. Wu Liu; Xinwen Guo; Xiangsheng Wang

2004-01-01

30

Distortional binding of transition state analogs to human purine nucleoside phosphorylase probed by magic angle spinning solid-state NMR  

PubMed Central

Transition state analogs mimic the geometry and electronics of the transition state of enzymatic reactions. These molecules bind to the active site of the enzyme much tighter than substrate and are powerful noncovalent inhibitors. Immucillin-H (ImmH) and 4?-deaza-1?-aza-2?-deoxy-9-methylene Immucillin-H (DADMe-ImmH) are picomolar inhibitors of human purine nucleoside phosphorylase (hPNP). Although both molecules are electronically similar to the oxocarbenium-like dissociative hPNP transition state, DADMe-ImmH is more potent than ImmH. DADMe-ImmH captures more of the transition state binding energy by virtue of being a closer geometric match to the hPNP transition state than ImmH. A consequence of these similarities is that the active site of hPNP exerts greater distortional forces on ImmH than on DADMe-ImmH to “achieve” the hPNP transition state geometry. By using magic angle spinning solid-state NMR to investigate stable isotope-labeled ImmH and DADMe-ImmH, we have explored the difference in distortional binding of these two inhibitors to hPNP. High-precision determinations of internuclear distances from NMR recoupling techniques, rotational echo double resonance, and rotational resonance, have provided unprecedented atomistic insight into the geometric changes that occur upon binding of transition state analogs. We conclude that hPNP stabilizes conformations of these chemically distinct analogs having distances between the cation and leaving groups resembling those of the known transition state.

Vetticatt, Mathew J.; Itin, Boris; Evans, Gary B.; Schramm, Vern L.

2013-01-01

31

Solid-State NMR for Bacterial Biofilms  

PubMed Central

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

Reichhardt, Courtney; Cegelski, Lynette

2014-01-01

32

Mefenamic Acid Anti-Inflammatory Drug: Probing Its Polymorphs by Vibrational (IR and Raman) and Solid-State NMR Spectroscopies.  

PubMed

This work deals with the spectroscopic (supported by quantum chemistry calculations), structural, and morphological characterization of mefenamic acid (2-[(2,3-(dimethylphenyl)amino] benzoic acid) polymorphs, known as forms I and II. Polymorph I was obtained by recrystallization in ethanol, while form II was reached by heating form I up to 175 °C, to promote the solid phase transition. Experimental and theoretical vibrational band assignments were performed considering the presence of centrosymmetric dimers. Besides band shifts in the 3345-3310 cm(-1) range, important vibrational modes to distinguish the polymorphs are related to out-of-phase and in-phase N-H bending at 1582 (Raman)/1577 (IR) cm(-1) and 1575 (Raman)/1568 (IR) cm(-1) for forms I and II, respectively. In IR spectra, bands assigned to N-H bending out of plane are observed at 626 and 575 cm(-1) for polymorphs I and II, respectively. Solid-state (13)C NMR spectra pointed out distinct chemical shifts for the dimethylphenyl group: 135.8 to 127.6 ppm (carbon bonded to N) and 139.4 to 143.3 ppm (carbon bonded to methyl group) for forms I and II, respectively. PMID:24654805

Cunha, Vanessa R R; Izumi, Celly M S; Petersen, Philippe A D; Magalhães, Alviclér; Temperini, Marcia L A; Petrilli, Helena M; Constantino, Vera R L

2014-04-24

33

Probing Membrane Topology of the Antimicrobial Peptide Distinctin by Solid-State NMR Spectroscopy in Zwitterionic and Charged Lipid Bilayers  

PubMed Central

Distinctin is a 47-residue antimicrobial peptide, which interacts with negatively charged membranes and is active against Gram-positive and Gram-negative bacteria. Its primary sequence comprises two linear chains of 22 (chain 1) and 25 (chain 2) residues, linked by a disulfide bridge between Cys19 of chain 1 and Cys23 of chain 2. Unlike other antimicrobial peptides, distinctin in the absence of the lipid membrane has a well-defined three-dimensional structure, which protects it from protease degradation. Here, we used static solid-state NMR spectroscopy to study the topology of distinctin in lipid bilayers. We found that In mechanically aligned lipid bilayers (charged or zwitterionic) this heterodimeric peptide adopts an ordered conformation absorbed on the surface of the membrane, with the long helix (chain 2), approximately parallel to the lipid bilayer (?5° from the membrane plane) and the short helix (chain 1) forming a ?24° angle. Since at lipid-to-protein molar ratio of 50:1 the peptide does not disrupt the macroscopic alignment of either charged or zwitterionic lipid bilayers, it is possible that higher concentrations might be needed for the hypothesized pore formation, or alternatively, distinctin elicits its cell disruption action by other mechanisms.

Verardi, Raffaello; Traaseth, Nathaniel J.; Shi, Lei; Porcelli, Fernando; Monfregola, Luca; De Luca, Stefania; Amodeo, Pietro; Veglia, Gianluigi; Scaloni, Andrea

2010-01-01

34

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.

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

2009-01-01

35

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

NASA Astrophysics Data System (ADS)

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.

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

2009-09-01

36

Direct probing of sorbent-solvent interactions for amylose tris(3,5-dimethylphenylcarbamate) using infrared spectroscopy, X-ray diffraction, solid-state NMR, and DFT modeling.  

PubMed

The sorbent-solvent interactions for amylose tris(3, 5-dimethylphenylcarbamate) (ADMPC) with five commonly used solvents, hexane, methanol, ethanol, 2-propanol (IPA), and acetonitrile (ACN), are studied using attenuated total reflection infrared spectroscopy (ATR-IR) of thin sorbent films, X-ray diffraction (XRD) of thin films, (13)C cross polarization/magic angle spinning (CP/MAS) and MAS solid state NMR of polymer-coated silica beads (commercially termed "Chiralpak AD"), and DFT modeling. The ADMPC-polymer-coated silica beads are used commercially for analytical and preparative scale separations of chiral enantiomers. The polymer forms helical rods with intra- and inter-rod hydrogen bonds (H-bonds). There are various nm-sized cavities formed between the polymer side-chains and rods. The changes in the H-bonding states of the C=O and NH groups of the polymer upon absorption of each of the five solvents at 25 degrees C are determined with ATR-IR. The IR wavenumbers, the H-bonding interaction energies, and the H-bonding distances of the polymer side-chains with each of the solvent molecules are predicted using the DFT/B3LYP/6-311+g(d,p) level of theory. The changes in the polymer crystallinity upon absorption of each solvent are characterized with XRD. The changes in the polymer crystallinity and the H-bonding states of C=O groups are also probed with (13)C CP/MAS solid-state NMR. The changes in the polymer side-chain mobility are detected using (13)C MAS solid-state NMR. The H-bonding states of the polymer change upon absorption of each polar solvent and usually result in an increase in the polymer crystallinity and the side-chain mobility. The polymer rods are reorganized upon solvent absorption, and the distance between the rods increases with the increase in the solvent molecular size. These results have implications for understanding the role of the solvent in modifying the structure and behavior of the polymer sorbents. PMID:16854108

Kasat, Rahul B; Zvinevich, Yury; Hillhouse, Hugh W; Thomson, Kendall T; Wang, Nien-Hwa Linda; Franses, Elias I

2006-07-27

37

Probing the local structural environment of calcium by natural-abundance solid-state 43 Ca NMR  

NASA Astrophysics Data System (ADS)

New natural-abundance 43 Ca magic angle spinning (MAS) NMR data measured at high magnetic field ( 14.1 T ) is presented for a range of crystalline calcium-containing binary and ternary inorganic compounds. The combination of high field, moderate MAS (up to 4.5 kHz ), and large sample volume (a 9.5 mm diameter MAS rotor) means that a good signal-to-noise ratio can generally be obtained in a time ( ˜12 h ) that makes 43 Ca NMR a feasible approach for determining information about calcium siting in a wide range of materials of physical interest. This study greatly increases the number of 43 Ca NMR parameters determined for solid materials in the literature, extending reports to local nearest-neighbor coordinations to other than oxygen. These data show that the isotropic chemical shift range is >250 ppm and typically that the quadrupole interaction is <4 MHz . In ternary compounds where Ca is coordinated in the nearest-neighbor shell by only oxygen, the isotropic 43 Ca chemical shift correlates well to the mean Ca-O distance, consistent with the only previous study. In binary compounds the isotropic 43 Ca chemical shift does not appear to be correlated with the mean Ca-X bond length. The extension of natural-abundance 43 Ca MAS NMR studies to amorphous materials are reported by examining sol-gel prepared calcium silicate materials. The data show that in the initial amorphous mixture at lower temperatures (120 350°C) the calcium environment is more like that in the parent calcium nitrate than a silicate, and that further heat treatment causes very significant broadening of the calcium resonance. The implications of this observation for the use of natural-abundance 43 Ca MAS NMR structural studies of amorphous materials are examined.

Lin, Zhongjie; Smith, M. E.; Sowrey, F. E.; Newport, R. J.

2004-06-01

38

Probing the Na+ binding site in a calix[4]arene-guanosine conjugate dimer by solid-state 23Na NMR and quantum chemical calculation.  

PubMed

Using solid-state (23)Na NMR and quantum chemical calculations we have found that the Na(+) ion bound to a calix[4]arene-guanosine conjugate dimer resides slightly above the G-quartet plane and simultaneously coordinates to a water molecule in a square-pyramidal (penta-coordination) geometry. PMID:19360177

Wong, Alan; Kotch, Frank W; Kwan, Irene C M; Davis, Jeffery T; Wu, Gang

2009-04-28

39

Dynamics of guest molecules in PHTP inclusion compounds as probed by solid-state NMR and fluorescence spectroscopy.  

PubMed

Partially deuterated 1,4-distyrylbenzene () is included into the pseudohexagonal nanochannels of perhydrotriphenylene (PHTP). The overall and intramolecular mobility of is investigated over a wide temperature range by (13)C, (2)H NMR as well as fluorescence spectroscopy. Simulations of the (2)H NMR spectral shapes reveal an overall wobble motion of in the channels with an amplitude of about 4 degrees at T = 220 K and 10 degrees at T = 410 K. Above T = 320 K the wobble motion is superimposed by localized 180 degrees flips of the terminal phenyl rings with a frequency of 10(6) Hz at T = 340 K. The activation energies of both types of motions are around 40 kJ mol(-1) which imply a strong sterical hindrance by the surrounding PHTP channels. The experimental vibrational structure of the fluorescence excitation spectra of is analyzed in terms of small amplitude ring torsional motions, which provide information about the spatial constraints on by the surrounding PHTP host matrix. Combining the results from NMR and fluorescence spectroscopy as well as of time-dependent density functional calculations yields the complete potential surfaces of the phenyl ring torsions. These results, which suggest that intramolecular mobility of is only reduced but not completely suppressed by the matrix, are corroborated by MD simulations. Unrealistically high potential barriers for phenyl ring flips are obtained from MD simulations using rigid PHTP matrices which demonstrate the importance of large amplitude motions of the PHTP host lattice for the mobility of the guest molecules. PMID:19562129

Srinivasan, G; Villanueva-Garibay, J A; Müller, K; Oelkrug, D; Milian Medina, B; Beljonne, D; Cornil, J; Wykes, M; Viani, L; Gierschner, J; Martinez-Alvarez, R; Jazdzyk, M; Hanack, M; Egelhaaf, H-J

2009-07-01

40

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

41

CONFORMATIONAL FLEXIBILITY AND STRAND ARRANGEMENTS OF THE MEMBRANE-ASSOCIATED HIV FUSION PEPTIDE TRIMER PROBED BY SOLID-STATE NMR SPECTROSCOPY†  

PubMed Central

The human immunodeficiency virus (HIV) fusion peptide (HFP) is the N-terminal apolar region of the HIV gp41 fusion protein and interacts with target cell membranes and promotes membrane fusion. The free peptide catalyzes vesicle fusion at least to the lipid mixing stage and serves as a useful model fusion system. For gp41 constructs which lack the HFP, high-resolution structures show trimeric protein and suggest that at least three HFPs interact with the membrane with their C-termini in close proximity. In addition, previous studies have demonstrated that HFPs which are cross-linked at their C-termini to form trimers (HFPtr) catalyze fusion at a rate which is 15?40 times greater than non-cross-linked HFP. In the present study, the structure of membrane-associated HFPtr was probed with solid-state nuclear magnetic resonance (NMR) methods. Chemical shift and intramolecular 13CO-15N distance measurements show that the conformation of the Leu-7 to Phe-11 region of HFPtr has predominant helical conformation in membranes without cholesterol and ? strand conformation in membranes containing ?30 mol% cholesterol. Interstrand 13CO-13CO and 13CO-15N distance measurements were not consistent with an in-register parallel strand arrangement but were consistent with either: (1) parallel arrangement with adjacent strands two-residues out-of-register; or (2) antiparallel arrangement with adjacent strand crossing between Phe-8 and Leu-9. Arrangement (1) could support the rapid fusion rate of HFPtr because of placement of the apolar N-terminal regions of all strands on the same side of the oligomer while arrangement (2) could support the assembly of multiple fusion protein trimers.

Zheng, Zhaoxiong; Yang, Rong; Bodner, Michele L.; Weliky, David P.

2008-01-01

42

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

43

Solid State NMR Studies of Amyloid Fibril Structure  

PubMed Central

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 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

2011-01-01

44

Probing the structural disorder of basalts and slab-driven andesite melts: Insights from high-resolution solid-state NMR study  

NASA Astrophysics Data System (ADS)

Whereas the structure of multi-component silicate melts has strong implication for the properties of natural silicate melts and relevant magmatic processes in Earth's mantle and crust, little is known about their atomic structures due to lack of suitable experimental probes of multi-component amorphous oxides. Although most of the progress in melt structure has been made for relatively simple binary and ternary silicate glasses, recent advances in high-resolution solid-state NMR (nuclear magnetic resonance) unveil previously unknown structural details of multi-component silicate melts (Lee, S. K. and Sung, S., Chem. Geol., 2008, 256, 326; Lee et al., P. Natl. Acad. Sci. USA., 2011, 108, 6847; Park and Lee, Geochim. Cosmochim. Acta, 2012, 80, 125). In this study we report experimental results on the effects of composition. atomic structure of CaO-MgO-Al_{2} O_{3} -SiO_{2} (CMAS) glasses in diopside (CaMgSi_{2}O_{6}) and Ca-tschermakite (CaAl_{2}SiO_{6}) join and glass in the diopside-anorthite eutectic composition (Di_{64}An_{36})—model systems for basaltic melts—using solid-state NMR. We also report the first high-resolution experimental results on the atomic structure of CaO-MgO-Na_{2}O-Al_{2}O_{3}-SiO_{2} (CMNAS) glasses in diopside and jadeite (NaAlSi_{2}O_{6}) join, and glass in the natural phonolite composition (CaO: MgO: Na_{2}O: K_{2}O: Al_{2}O_{3}: SiO_{2}= 1.4: 8.0: 9.0: 3.8: 13: 64 mol%), a model system for slab driven andesite melts. The Al-27 3QMAS (triple quantum magic angle spinning) NMR spectra of CMAS glasses in diopside-Ca-tschermakite join show predominant ^{[4]}Al and a non-negligible fraction of ^{[5]}Al. Approximately 3.3% of ^{[5]}Al is observed for Di_{64}An_{36} glass. The Al-27 3QMAS NMR spectra of CMNAS glasses in diopside and jadeite join show mostly ^{[4]}Al and a non-negligible fraction of ^{[5]}Al (X_{Diopside}=0.75, the mole fraction of diopside content). While the C_{q} (quadrupolar coupling constant) of ^{[4]}Al for glasses in diopside-Ca-tschermakite join decreases, that of ^{[4]}Al in diopside-jadeite increases with increasing X_{Diopside}. The Al-27 3QMAS NMR spectrum of phonolite glass shows only ^{[4]}Al species. The C_{q} of ^{[4]}Al ( 4.6 MHz) in phonolite glass is smaller than that of Di_{64}An_{36} eutectic glass ( 6.0 MHz) indicating larger deviation from perfect tetrahedral symmetry around ^{[4]}Al in basaltic melt than that of natural andesitic melt. The fraction of ^{[5]}Al, the degree of configurational disorder, increases with increasing X_{Ca+Mg} (the fraction of high field strength cations, X_{Ca+Mg}=[Ca+Mg]/[Ca+Mg+Na]) and thus the average cation field strength of non- framework cations (the average value of cation field strength normalized by mole fraction of each cations). The fraction of ^{[5]}Al is negligible from X_{Ca+Mg} =0 to X_{Ca+Mg} =0.08, and then it abruptly increases from 1.6 % for X_{Ca+Mg}=0.11 to 3.5% for X_{Ca+Mg}=0.13. This result indicates that there is a threshold composition (X_{Ca+Mg} 0.1) of silicate glasses and melts for increasing fraction of ^{[5]}Al. The abrupt changes of the fraction of ^{[5]}Al multi-component silicate glasses and melts can provide insight into drastic changes of macroscopic properties (entropy, viscosity, diffusivity, etc.) with varying composition of melt (i.e., basalt and andesite melts in this study).

Park, S.; Lee, S.

2012-12-01

45

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

46

17O solid-state NMR as a sensitive probe of hydrogen bonding in crystalline and amorphous solid forms of diflunisal.  

PubMed

(17)O solid-state NMR (SSNMR) can provide insight into hydrogen bonding interactions in pharmaceutical polymorphs, cocrystals, and amorphous dispersions. When combined with straightforward (17)O synthetic labeling, the use of (17)O SSNMR allows for direct study of key interactions such as hydrogen bonding in these systems. In this work, novel applications of (17)O SSNMR are demonstrated in the analysis of a polymorph of diflunisal, a cocrystal of diflunisal with pyrazinamide, and amorphous dispersions of diflunisal in two polymers. The observation of the (17)O nucleus is shown to be a highly specific and useful alternative to more conventional studies of the (1)H, (13)C, and (19)F nuclei in these systems and offers unique insight into hydrogen bonding interactions. Quantum chemical calculations are used to assess the (17)O SSNMR measurements for the polymorph of diflunisal for which a crystal structure has been previously determined. Empirical hydrogen bonding trends are then examined in the cocrystal and amorphous solid forms using (17)O NMR parameters. A novel application of (1)H-(17)O cross-polarization heteronuclear correlation (CP-HETCOR) experiments is also demonstrated for the cocrystal and two dispersions. This experiment offers specific information about proton environments in proximity to the labeled oxygen sites. The use of (17)O SSNMR techniques extends the utility of SSNMR in applications to cocrystals and amorphous dispersions. PMID:23822557

Vogt, Frederick G; Yin, Hao; Forcino, Rachel G; Wu, Lianming

2013-09-01

47

Solid-state NMR as an analytical tool: quantitative aspects.  

PubMed

Analytical methods based on solid-state NMR are becoming increasingly popular. However, these flourishing activities bring up the issue of how accurately NMR can assess an analyte proportion in a solid sample. The use of a chemical intensity reference for this purpose is a natural but often unsuitable choice, due to sample stability or preciousness. We propose here a protocol to perform quantitative measurements in solid-state NMR, by calibration of the circuit response through a low-power pulse injected during the acquisition (the so-called ERETIC method). Although this method has been in use for some time in liquid-phase and in vivo NMR, we point out here some peculiarities and useful applications typical of solids. Namely, the temperature dependence of the signal intensity imposes care in the application to MAS experiments. PMID:16229992

Ziarelli, Fabio; Caldarelli, Stefano

2006-02-01

48

Location and orientation of adsorbed molecules in zeolites from solid-state REAPDOR NMR  

Microsoft Academic Search

The use of rotational echo adiabatic passage double resonance (REAPDOR) solid-state nuclear magnetic resonance (NMR) to determine the site location of an adsorbed polar molecule in a zeolite cage is presented. Nitrogen-15 labeled ammonia is used as a probe molecule to characterize the initial adsorption site in 3A zeolite molecular sieves. The relative position of the ammonia adsorption site in

Todd Michael Alam; Gregory P. Holland

2005-01-01

49

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

50

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

51

GFT projection NMR spectroscopy for proteins in the solid state  

PubMed Central

Recording of four-dimensional (4D) spectra for proteins in the solid state has opened new avenues to obtain virtually complete resonance assignments and three-dimensional (3D) structures of proteins. As in solution state NMR, the sampling of three indirect dimensions leads per se to long minimal measurement time. Furthermore, artifact suppression in solid state NMR relies primarily on radio-frequency pulse phase cycling. For an n-step phase cycle, the minimal measurement times of both 3D and 4D spectra are increased n times. To tackle the associated ‘sampling problem’ and to avoid sampling limited data acquisition, solid state G-Matrix Fourier Transform (SS GFT) projection NMR is introduced to rapidly acquire 3D and 4D spectral information. Specifically, (4,3)D (HA)CANCOCX and (3,2)D (HACA)NCOCX were implemented and recorded for the 6 kDa protein GB1 within about 10% of the time required for acquiring the conventional congeners with the same maximal evolution times and spectral widths in the indirect dimensions. Spectral analysis was complemented by comparative analysis of expected spectral congestion in conventional and GFT NMR experiments, demonstrating that high spectral resolution of the GFT NMR experiments enables one to efficiently obtain nearly complete resonance assignments even for large proteins.

Franks, W. Trent; Atreya, Hanudatta S.; Szyperski, Thomas

2011-01-01

52

(15)N 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 22ppm). 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 39.3ppm 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

53

Advances in solid-state NMR of cellulose.  

PubMed

Nuclear magnetic resonance (NMR) spectroscopy is a well-established analytical and enabling technology in biofuel research. Over the past few decades, lignocellulosic biomass and its conversion to supplement or displace non-renewable feedstocks has attracted increasing interest. The application of solid-state NMR spectroscopy has long been seen as an important tool in the study of cellulose and lignocellulose structure, biosynthesis, and deconstruction, especially considering the limited number of effective solvent systems and the significance of plant cell wall three-dimensional microstructure and component interaction to conversion yield and rate profiles. This article reviews common and recent applications of solid-state NMR spectroscopy methods that provide insight into the structural and dynamic processes of cellulose that control bulk properties and biofuel conversion. PMID:24590189

Foston, Marcus

2014-06-01

54

Solid-state NMR investigation of promoted silver catalysts  

SciTech Connect

The effects of cesium promoters on silver catalysts, supported by {gamma}-alumina, were studied by adsorbing mono- or dilabeled [{sup 13}C]ethylene onto the catalysts and performing low-temperature (70 K) solid-state {sup 13}C NMR measurements on the ethylene. Selective isotopic enrichment was used to investigate the electronic environment present in and around the ethylene molecule as a function of promoter concentration. Changes in the spectroscopic parameters describing the ethylene lineshapes were extracted using a nonlinear least-squares procedure. These parameters were then used to determine the structure of the ethylene molecule on the surface and to probe the changes induced by adding cesium promoters. Similarly, the state of cesium in the catalyst system was investigated by spin-echo double-resonance spectroscopy and scanning electron microscopy X-ray fluorescence methods. The results imply that the form of cesium is not that of an oxide but, in all probability, reflect those of a cation-anion pair.

Hughes, E.; Koons, J.M.; Wang, J. [Univ. of South Carolina, Columbia, SC (United States). Dept. of Chemistry and Biochemistry] [Univ. of South Carolina, Columbia, SC (United States). Dept. of Chemistry and Biochemistry; Ellis, P.D. [Pacific Northwest National Lab., Richland, WA (United States). Environmental Molecular Sciences Lab.] [Pacific Northwest National Lab., Richland, WA (United States). Environmental Molecular Sciences Lab.

1999-04-25

55

Probing the contacts of a low-affinity substrate with a membrane-embedded transport protein using 1H-13C cross-polarisation magic-angle spinning solid-state NMR.  

PubMed

Solid-state NMR combined with sample deuteration was used to probe the proximity of the low-affinity substrate D-glucose to its binding site within the Escherichia coli sugar transport protein GalP. Samples of E. coli inner membranes with amplified expression of GalP were incubated in D(2)O with D-[(13)C(6)]glucose and (13)C NMR signals from the substrate were assigned in two-dimensional dipolar-assisted rotational resonance (DARR) spectra. The signals were confirmed as representing D-glucose bound to GalP as the peaks were abolished after the substrate was displaced from the specific site with the inhibitor forskolin. The (13)C chemical shift values for D-[(13)C(6)]glucose in solution revealed some differences compared to those for ligand bound to GalP, the differences being most pronounced for positions C1 and C2, and especially for C1 in the ?-anomer. (13)C cross-polarization build-up was measured for C1 and C2 of D-[(13)C(6)]glucose and D-[(2)H(7), (13)C(6)]glucose in GalP membranes suspended in D(2)O. The build-up curves for the deuterated substrate reflect intermolecular (1)H-(13)C interactions between the protein and the fully deuterated substrate; the signal build-up suggests that the ?-anomer is situated closer to the protein binding site than is the ?-anomer, consistent with its relatively high signal intensities and more pronounced chemical shift changes in the 2D-correlation spectra. These results demonstrate the utility of solid-state NMR combined with sample deuteration for mapping the binding interface of low affinity ligands with membrane proteins. PMID:23173920

Patching, Simon G; Henderson, Peter J F; Sharples, David J; Middleton, David A

2013-03-01

56

Solid state thermostat has integral probe and circuitry  

NASA Technical Reports Server (NTRS)

Compact, reliable thermostat provides a temperature readout signal and a continuous temperature-control output for temperature monitoring by automatic checkout equipment or telemetry systems. It employs a solid state circuit in a housing rigidly attached to a thermistor probe.

1966-01-01

57

Quantitative solid-state NMR spectra of CO adsorbed from aqueous solution onto a commercial electrode  

SciTech Connect

In this communication we present quantitative, solid-state NMR spectra of CO adsorbed from solution onto a commercial Pt/C fuel cell electrode; the CO spectra are presented as a function of surface coverage, as modified by electrochemical oxidation of surface-bound CO. These data clearly portend the widespread application of quantitative solid-state NMR techniques for studies of practical electrochemical processes. In conclusion, we report quantitative {sup 13}C NMR spectra for CO adsorbed onto commercial Pt/C fuel cell electrodes. Each spectrum shown required approximately 14 h of instrument time to acquire; we are further optimizing both the NMR parameters and probe configuration for improved signal-to-noise ratios. The number and character of CO adsorption sites are clearly accessible via this approach; if used in conjunction with in situ potential control, the number of possible studies of potential-dependent processes appears to be vast. 6 refs., 2 figs.

Yahnke, M.S.; Rush, B.M.; Reimer, J.A.; Cairns, E.J. [Lawrence Berkeley National Lab., CA (United States)] [Lawrence Berkeley National Lab., CA (United States); [Univ. of California, Berkeley, CA (United States)

1996-12-04

58

Solid-State NMR Characterization of Gas Vesicle Structure  

Microsoft Academic Search

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

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

2010-01-01

59

Protein structure determination with paramagnetic solid-state NMR spectroscopy.  

PubMed

Many structures of the proteins and protein assemblies that play central roles in fundamental biological processes and disease pathogenesis are not readily accessible via the conventional techniques of single-crystal X-ray diffraction and solution-state nuclear magnetic resonance (NMR). On the other hand, many of these challenging biological systems are suitable targets for atomic-level structural and dynamic analysis by magic-angle spinning (MAS) solid-state NMR spectroscopy, a technique that has far less stringent limitations on the molecular size and crystalline state. Over the past decade, major advances in instrumentation and methodology have prompted rapid growth in the field of biological solid-state NMR. However, despite this progress, one challenge for the elucidation of three-dimensional (3D) protein structures via conventional MAS NMR methods is the relative lack of long-distance data. Specifically, extracting unambiguous interatomic distance restraints larger than ?5 Å from through-space magnetic dipole-dipole couplings among the protein (1)H, (13)C, and (15)N nuclei has proven to be a considerable challenge for researchers. It is possible to circumvent this problem by extending the structural studies to include several analogs of the protein of interest, intentionally modified to contain covalently attached paramagnetic tags at selected sites. In these paramagnetic proteins, the hyperfine couplings between the nuclei and unpaired electrons can manifest themselves in NMR spectra in the form of relaxation enhancements of the nuclear spins that depend on the electron-nucleus distance. These effects can be significant for nuclei located up to ?20 Å away from the paramagnetic center. In this Account, we discuss MAS NMR structural studies of nitroxide and EDTA-Cu(2+) labeled variants of a model 56 amino acid globular protein, B1 immunoglobulin-binding domain of protein G (GB1), in the microcrystalline solid phase. We used a set of six EDTA-Cu(2+)-tagged GB1 mutants to rapidly determine the global protein fold in a de novo fashion. Remarkably, these studies required quantitative measurements of only approximately four or five backbone amide (15)N longitudinal paramagnetic relaxation enhancements per residue, in the complete absence of the usual internuclear distance restraints. Importantly, this paramagnetic solid-state NMR methodology is general and can be directly applied to larger proteins and protein complexes for which a significant fraction of the signals can be assigned in standard 2D and 3D MAS NMR chemical shift correlation spectra. PMID:23464364

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

2013-09-17

60

Microcoils and microsamples in solid-state NMR.  

PubMed

Recent reports on microcoils are reviewed. The first part of the review includes a discussion of how the geometries of the sample and coil affect the NMR signal intensity. In addition to derivation of the well-known result that the signal intensity increases as the coil size decreases, the prediction that dilution of a small sample with magnetically inert matter leads to better sensitivity if a tiny coil is not available is given. The second part of the review focuses on the issues specific to solid-state NMR. They include realization of magic-angle spinning (MAS) using a microcoil and harnessing of such strong pulses that are feasible only with a microcoil. Two strategies for microcoil MAS, the piggyback method and magic-angle coil spinning (MACS), are reviewed. In addition, MAS of flat, disk-shaped samples is discussed in the context of solid-state NMR of small-volume samples. Strong RF irradiation, which has been exploited in wide-line spectral excitation, multiple-quantum MAS (MQMAS), and dipolar decoupling experiments, has been accompanied by new challenges regarding the Bloch-Siegert effect, the minimum time resolution of the spectrometer, and the time scale of pulse transient effects. For a possible solution to the latter problem, recent reports on active compensation of pulse transients are described. PMID:23083521

Takeda, Kazuyuki

2012-01-01

61

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

62

Solid-State NMR Studies of Chemically Lithiated CFx  

PubMed Central

Three types of fluorinated carbon, all in their original form and upon sequential chemical lithiations via n-butyllithium, were investigated by 13C and 19F solid-state NMR methods. The three starting CFx materials [where x = 1 (nominally)] were fiber based, graphite based, and petroleum coke based. The aim of the current study was to identify, at the atomic/molecular structural level, factors that might account for differences in electrochemical performance among the different kinds of CFx. Differences were noted in the covalent F character among the starting compounds and in the details of LiF production among the lithiated samples.

Leifer, N. D.; Johnson, V. S.; Ben-Ari, R.; Gan, H.; Lehnes, J. M.; Guo, R.; Lu, W.; Muffoletto, B. C.; Reddy, T.; Stallworth, P. E.; Greenbaum, S. G.

2010-01-01

63

Probing intermolecular hydrogen bonding in sibenadet hydrochloride polymorphs by high-resolution (1) H double-quantum solid-state NMR spectroscopy.  

PubMed

Molecular packing in two polymorphs of sibenadet hydrochloride (AR-C68397AA, Viozan™) is investigated using a combined experimental (1) H double-quantum (DQ) solid-state magic-angle spinning nuclear magnetic resonance and computational (gauge including projected augmented wave calculation of chemical shifts) approach. For Form I, NH-NH and NH-OH (1) H DQ peaks are observed corresponding to nearest distances of 2.62 and 2.87 Å, respectively, for the intermolecular hydrogen-bonding arrangement in the single-crystal X-ray diffraction structure. The same (1) H DQ peaks at the same (1) H chemical shifts are observed for Form II, for which there is no single-crystal diffraction structure, indicating the same intermolecular hydrogen-bonding arrangement of the benzothiazolone moieties as in Form I. (1) H DQ build-up (as a function of the DQ recoupling time) curves are presented for the resolved NH-NH and NH-OH DQ peaks for the two polymorphs. For Form I, the ratio of the maximum intensity for the NH-OH and NH-NH DQ peaks is in excellent agreement with the ratio of the summed squares of the H-H dipolar couplings, as determined using H-H distances from the crystal structure up to 4 Å. Small differences in the (1) H DQ build-up behaviour for the two polymorphs are attributed to differences in the longer-range NH-OH distances associated with different inter-layer arrangements. PMID:22359321

Bradley, Jonathan P; Pickard, Chris J; Burley, Jonathan C; Martin, Dave R; Hughes, Leslie P; Cosgrove, Stephen D; Brown, Steven P

2012-05-01

64

Solid-state NMR of flavins and flavoproteins.  

PubMed

Why apply solid-state NMR (SSNMR) to flavins and flavoproteins? NMR provides information on an atom-specific basis about chemical functionality, structure, proximity to other groups, and dynamics of the system. Thus, it has become indispensable to the study of chemicals, materials, catalysts, and biomolecules. It is no surprise then that NMR has a great deal to offer in the study of flavins and flavoenzymes. In general, their catalytic or electron-transfer activity resides essentially in the flavin, a molecule eminently accessible by NMR. However, the specific reactivity displayed depends on a host of subtle interactions whereby the protein biases and reshapes the flavin's propensities to activate it for one reaction while suppressing other aspects of this cofactor's prodigious repertoire (Massey et al., J Biol Chem 244:3999-4006, 1969; Müller, Z Naturforsch 27B:1023-1026, 1972; Joosten and van Berkel, Curr Opin Struct Biol 11:195-202, 2007). Thus, we are fascinated to learn about how the flavin cofactor of one enzyme is, and is not, like the flavin cofactor of another. In what follows, we describe how the capabilities of SSNMR can help and are beginning to bear fruit in this exciting endeavor. PMID:24764096

Miller, Anne-Frances

2014-01-01

65

Biophysical applications of solid state and tritium NMR  

SciTech Connect

Novel applications of Magic Angle Sample Spinning (MASS) and Tritium ({sup 3}H) NMR to the study of mammalian tissue and in vivo metabolism, respectively, are described. The solid state {sup 31} P MASS NMR spectra of sodium, magnesium and calcium complexes of adenosine triphosphate (ATP) were recorded. These spectra indicate that the terminal phosphate group of the sodium complex is protonated in contrast to the unprotonated divalent complexes. The inductive effects of the divalent counter ions are also discussed. To better understand the nature of the {sup 31}P chemical shift interaction, the chemical shift tensors of a large variety of phosphates and phosphate esters were measured. The magnitude of the {sigma}{sub 33}, the low field, elements of the {sup 31}P chemical shift tensors in these phosphates were linearly related to the longest P-O bonds and the {simga}{sub 11}, the high field, elements to the shortest bonds. Similar relationships were found when these tensor elements were plotted against bond angles. The implications of these observations are discussed in the context of phosphorus-oxygen d-p {kappa} bonding interactions. The metabolism of (1-{sup 3}h) glucose in human and rat erythrocytes was monitored by {sup 3}H NMR.

Un, S.

1987-01-01

66

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.

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

2011-01-01

67

Solid state NMR study of nanodiamond surface chemistry.  

PubMed

Solid state NMR measurements using 13C, 1H and 19F nuclei (MAS, CP-MAS) underline the surface chemistry of nanodiamonds from different synthesis (detonation, high pressure high temperature and shock compression). The comparison of the spin-lattice relaxation times T1 and physicochemical characterization (spin densities of dangling bonds, specific surface area and Raman and infrared spectroscopies) for the various samples, as synthesized, chemically purified and fluorinated allows the nature and the location of the various groups, mainly C-OH, C-H and C-F to be investigated. C-OH groups are located only on the surface whereas C-H and dangling bonds seem to be distributed in the whole volume. Fluorination was studied as a chemical treatment for purification and change of the hydrophobicity through the conversion of the C-OH groups into covalent C-F bonds. PMID:22119523

Dubois, Marc; Guérin, Katia; Batisse, Nicolas; Petit, Elodie; Hamwi, André; Komatsu, Naoki; Kharbache, Hayat; Pirotte, Pascal; Masin, Francis

2011-11-01

68

Solid-state NMR and functional studies on proteorhodopsin.  

PubMed

Proteins of the proteorhodopsin (PR) family are found abundantly in many marine bacteria in the photic zone of the oceans. They are colour-tuned to their environment. The green absorbing species has been shown to act as a light-driven proton pump and thus could form a potential source of energy. The pK(a) of the primary proton acceptor is close to the pH of seawater which could also indicate a regulatory role. Here, we review and summarize our own recent findings in the context of known data and present some new results. Proton transfer in vitro by PR is shown by a fluorescence assay which confirms a pH dependent vectoriality. Previously reported low diffracting 2D crystal preparations of PR are assessed for their use for solid-state NMR by two dimensional (13)C-(13)C DARR spectra. (15)N-(1)H HETCOR MAS NMR experiments show bound water in the vicinity of the protonated Schiff base which could play a role in proton transfer. The effect of highly conserved H75 onto the properties of the chromophore has been investigated by single site mutations. They do show a pronounced effect onto the optical absorption maximum and the pK(a) of the proton acceptor but have only a small effect onto the (15)N chemical shifts of the protonated Schiff base. PMID:19268651

Pfleger, Nicole; Wörner, Andreas C; Yang, Jun; Shastri, Sarika; Hellmich, Ute A; Aslimovska, Lubica; Maier, Melanie S M; Glaubitz, Clemens

2009-06-01

69

Location and orientation of adsorbed molecules in zeolites from solid-state REAPDOR NMR.  

PubMed

The use of rotational echo adiabatic passage double resonance (REAPDOR) solid-state nuclear magnetic resonance (NMR) to determine the site location of an adsorbed polar molecule in a zeolite cage is presented. Nitrogen-15 labeled ammonia is used as a probe molecule to characterize the initial adsorption site in 3A zeolite molecular sieves. The relative position of the ammonia adsorption site in the cage is determined by measuring the internuclear distance between the N on ammonia and both a Na cation site and an Al framework environment using 15N/23Na and 15N/27Al REAPDOR NMR experiments, respectively. The measured internuclear distances are similar to a specific ammonia adsorption site for the zeolite 4A ammonia sorption complex located using X-ray diffraction. Additional details regarding the ammonia hydrogen-bonding environment can be extracted from 1H/23Na and 1H/27Al REAPDOR NMR measurements. PMID:19787933

Holland, Gregory P; Alam, Todd M

2005-04-21

70

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

2014-04-01

71

Investigations of adsorption sites on oxide surfaces using solid-state NMR and TPD-IGC  

NASA Astrophysics Data System (ADS)

The number and chemical identity of reactive sites on surfaces of glass affects the processing, reliability, and lifetime of a number of important commercial products. Surface site densities, distributions, and structural identities are closely tied to the formation and processing of the glass surface, and exert a direct influence on strength and coating performance. The surface of a glass sample may vary markedly from the composition and chemistry of the bulk glass. We are taking a physicochemical approach to understanding adsorption sites on pristine multicomponent glass fibers surfaces, directly addressing the effect of processing on surface reactivity. This project aimed to understand the energy distributions of surface adsorption sites, the chemical/structural identity of those sites, and the relationship of these glasses to glass composition, thermal history, and in future work, surface coatings. We have studied the bulk and surface structure as well as the surface reactivity of the glass fibers with solid-state nuclear magnetic resonance (NMR) spectroscopy, inverse gas chromatography (IGC), and computational chemistry methods. These methods, solid-state NMR and IGC, typically require high surface area materials; however, by using probe molecules for NMR experiments or packing a column at high density for IGC measurements, lower surface area materials, such as glass fibers, can be investigated. The glasses used within this study were chosen as representative specimens of fibers with potentially different reactive sites on their surfaces. The two glass compositions were centered around a nominal E-glass, which contains very little alkali cations and mainly alkaline earth cations, and wool glass, which contains an abundance of alkali cations. The concentration of boron was varied from 0 to 8 mole % in both fiber compositions. Fibers were drawn from each composition at a variety of temperatures and draw speeds to provide a range of glass samples with varying diameters and thermal histories. The bulk structural features in both compositions of glass fibers were identified using high-resolution 29Si, 27Al, and 11B magic-angle spinning (MAS) NMR spectroscopic measurements. In multi-component glasses, the determination of silicon, aluminum, and boron distributions becomes difficult due to the competitive nature of the network-modifying oxides among the network-forming oxides. In pure silicates, 29Si MAS NMR can often resolve resonances arising from silicate tetrahedron having varying numbers of bridging oxygens. In aluminoborosilicate glasses, aluminum is present in four-, five-, and six- coordination with oxygen as neighbors. The speciation of the aluminum can be determined using 27Al MAS NMR. The fraction of tetrahedral boron species in the glass fibers were measured using 11B MAS NMR, which is typically used to study the short-range structure of borate containing glasses such as alkali borate, borosilicate, and aluminoborosilicate glasses. While solid-state NMR is a powerful tool for elucidating bonding environments and coordination changes in the glass structure, it cannot quantitatively probe low to moderate surface area samples due to insufficient spins. Chemical probes either physisorbed or chemisorbed to the fiber's surface can increase the surface selectivity of NMR for analysis of samples with low surface areas and provide information about the local molecular structure of the reactive surface site. Common chemical probe molecules contain NMR active nuclei such as 19F or may be enriched with 13C. A silyating agent, (3,3,3-trifluoropropyl)dimethylchlorosilane (TFS), reacts with reactive surface hydroxyls, which can be quantified by utilizing the NMR active nucleus (19F) contained in the probe molecule. The observed 19F MAS NMR peak area is integrated and compared against a standard of known fluorine spins (concentration), allowing the number of reactive hydroxyl sites to be quantified. IGC is a method used to study the surface properties of a material by examining the retention behavior of a probe molecule. The I

Golombeck, Rebecca A.

72

Precision and sensitivity optimization of quantitative measurements in solid state NMR  

NASA Astrophysics Data System (ADS)

This work presents a methodology for optimizing the precision, accuracy and sensitivity of quantitative solid state NMR measurements based on the external reference method. It is shown that the sample must be exclusively located within and completely span the coil region where the NMR response is directly proportional to the sample amount. We describe two methods to determine this "quantitative" coil volume, based on whether the probe is equipped or not with a gradient coil. In addition, to improve the sensitivity and the accuracy, an optimum rotor packing design is described, which allows the sample volume of the rotor to be matched to the quantitative coil volume. Experiments conducted on adamantane and NaCl, which are representative of a soft and hard material, respectively, show that one order of magnitude increase in experimental precision can be achieved with this methodology. Interestingly, the precision can be further improved by using the ERETIC™ method in order to compensate for most instrumental instabilities.

Ziarelli, Fabio; Viel, Stéphane; Sanchez, Stéphanie; Cross, David; Caldarelli, Stefano

2007-10-01

73

Precision and sensitivity optimization of quantitative measurements in solid state NMR.  

PubMed

This work presents a methodology for optimizing the precision, accuracy and sensitivity of quantitative solid state NMR measurements based on the external reference method. It is shown that the sample must be exclusively located within and completely span the coil region where the NMR response is directly proportional to the sample amount. We describe two methods to determine this "quantitative" coil volume, based on whether the probe is equipped or not with a gradient coil. In addition, to improve the sensitivity and the accuracy, an optimum rotor packing design is described, which allows the sample volume of the rotor to be matched to the quantitative coil volume. Experiments conducted on adamantane and NaCl, which are representative of a soft and hard material, respectively, show that one order of magnitude increase in experimental precision can be achieved with this methodology. Interestingly, the precision can be further improved by using the ERETIC method in order to compensate for most instrumental instabilities. PMID:17703975

Ziarelli, Fabio; Viel, Stéphane; Sanchez, Stéphanie; Cross, David; Caldarelli, Stefano

2007-10-01

74

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.; Washton, Nancy M.; Ryan, Joseph V.; Pantano, Carlo G.; Mueller, Karl T.

2013-06-01

75

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

Microsoft Academic Search

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

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

2003-01-01

76

Solid-state NMR studies of biomineralization peptides and proteins.  

PubMed

Nature has evolved sophisticated strategies for engineering hard tissues through the interaction of proteins, and ultimately cells, with inorganic mineral phases. This process, called biomineralization, is how living organisms transform inorganic materials such as hydroxyapatite, calcite, and silica into highly intricate and organized structures. The remarkable material properties of shell, bone, and teeth come from the activities of proteins that function at the organic-inorganic interface. A better understanding of the biomolecular mechanisms used to promote or retard the formation of mineral-based structures could provide important design principles for the development of calcification inhibitors and promoters in orthopedics, cardiology, urology, and dentistry. With the knowledge of the structural basis for control of hard tissue growth by proteins, scientists could potentially develop materials using biomimetic principles with applications in catalysis, biosensors, electronic devices, and chromatographic separations, to name a few. Additionally, biomineralization also has potential applications in electronics, catalysis, magnetism, sensory devices, and mechanical design. Where man-made hard materials require the use of extreme temperatures, high pressure, and pH, biological organisms can accomplish these feats at ambient temperature and at physiological pH. Despite the fact that many researchers want to identify and control the structure of proteins at material and biomineral interfaces, there is a decided lack of molecular-level structure information available for proteins at biomaterial interfaces in general. In particular, this holds for mammalian proteins that directly control calcification processes in hard tissue. The most fundamental questions regarding the secondary and tertiary structures of proteins adsorbed to material surfaces, how proteins catalyze the formation of biomineral composites, or how proteins interact at biomaterial interfaces remain unanswered. This is largely due to a lack of methods capable of providing high-resolution structural information for proteins adsorbed to material surfaces under physiologically relevant conditions. In this Account, we highlight recent work that is providing insight into the structure and crystal recognition mechanisms of a salivary protein model system, as well as the structure and interactions of a peptide that catalyzes the formation of biosilica composites. To develop a better understanding of the structure and interactions of proteins in biomaterials, we have used solid-state NMR techniques to determine the molecular structure and dynamics of proteins and peptides adsorbed onto inorganic crystal surfaces and embedded within biomineral composites. This work adds to the understanding of the structure and crystal recognition mechanisms of an acidic human salivary phosphoprotein, statherin. PMID:23932180

Roehrich, Adrienne; Drobny, Gary

2013-09-17

77

Isotope labeling for solution and solid-state NMR spectroscopy of membrane proteins.  

PubMed

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

2012-01-01

78

Solid-state NMR monitoring of a double bond isomerization in propene on ZnO  

NASA Astrophysics Data System (ADS)

Monitoring of the 13C-label scrambling from the position 3 to the position 1 in the 13C-labeled propene adsorbed on zinc oxide has been performed with 1H and 13C solid state NMR in situ. This allowed us to characterize the dynamics of a double bond shift reaction in adsorbed propene, and derive the kinetic parameters of this reaction, which were not earlier available without using solid state NMR and 13C-labeling of the olefin.

Gabrienko, Anton A.; Stepanov, Alexander G.

2014-06-01

79

Trends in solid-state NMR spectroscopy and their relevance for bioanalytics  

Microsoft Academic Search

Based on continuous methodical advances and developments, solid-state NMR spectroscopy has become a powerful tool for the\\u000a investigation of various materials, including polymers, glasses, zeolites, fullerenes, and many others. During the past decade,\\u000a solid-state NMR spectroscopy also found increasing interest for the study of biomolecules. For example, membrane proteins\\u000a reconstituted into lipid environments such as bilayers or vesicles, protein aggregates

Silvia Paasch; Eike Brunner

2010-01-01

80

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

PubMed

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

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

2014-02-01

81

Characterization of azobenzene polymer networks using in situ solid state NMR and temperature dependent photostriction  

NASA Astrophysics Data System (ADS)

Azobenzene liquid crystal polymer networks (azo-LCNs) undergo a complex light-driven molecular conformation change of the azobenzene chromophore which imparts a macroscopic shape change within a glassy polymer network. To better understand molecular conformational changes which underlie macroscopic polymer deformation, we have collected solid-state nuclear magnetic resonance (NMR) data on 19F fluorinated side-chain azo-LCNs using an in situ visible light (450-458 nm) LED light source. We illustrate measurable changes in 19F NMR lineshapes under light irradiation, indicating that conformational changes can be probed by NMR. The measured effects of light on NMR spectra are also found to be reversible upon removal of the light source. We further show that sample heating does not affect azobenzene isomerization through analysis of temperature-dependent magic-angle-spinning NMR lineshapes. These results illustrate a narrowing of the lineshapes, but no change in the NMR peak positions, indicating that heating from 30 and 60?° C affects molecular dynamics but does not change the azobenzene conformation. In addition to NMR data, benchtop photomechanical uni-axial measurements are taken over a temperature range from 23 to 60?° C. Samples with the fluorinated side-chain azo-LCNs are compared to samples composed only of non-fluorinated main-chain azo-LCN composition. Similar stress relaxation was observed in both compositions under high pre-stretch. The amount of stress relaxation was found to depend on the pre-stretch, the ambient temperature, and the polarization of light.

Worden, Matthew; Wang, Hongbo; Paravastu, Anant; Oates, William

2013-09-01

82

Low temperature solid-state NMR experiments of half-integer quadrupolar nuclides: caveats and data analysis  

Microsoft Academic Search

Solid-state NMR spectroscopy of half-integer quadrupolar nuclides has received a lot of interest recently with the advent of new methodologies and higher magnetic fields. We present here the extension of our previous low temperature method to an 18.8T system. This new probe entailed a total redesign including a cross coil and variable capacitors that are operational at cryogenic temperatures. The

Andrew S. Lipton; Robert W. Heck; Jesse A. Sears; Paul D. Ellis

2004-01-01

83

Optimized multiple quantum MAS lineshape simulations in solid state NMR  

NASA Astrophysics Data System (ADS)

The majority of nuclei available for study in solid state Nuclear Magnetic Resonance have half-integer spin I>1/2, with corresponding electric quadrupole moment. As such, they may couple with a surrounding electric field gradient. This effect introduces anisotropic line broadening to spectra, arising from distinct chemical species within polycrystalline solids. In Multiple Quantum Magic Angle Spinning (MQMAS) experiments, a second frequency dimension is created, devoid of quadrupolar anisotropy. As a result, the center of gravity of peaks in the high resolution dimension is a function of isotropic second order quadrupole and chemical shift alone. However, for complex materials, these parameters take on a stochastic nature due in turn to structural and chemical disorder. Lineshapes may still overlap in the isotropic dimension, complicating the task of assignment and interpretation. A distributed computational approach is presented here which permits simulation of the two-dimensional MQMAS spectrum, generated by random variates from model distributions of isotropic chemical and quadrupole shifts. Owing to the non-convex nature of the residual sum of squares (RSS) function between experimental and simulated spectra, simulated annealing is used to optimize the simulation parameters. In this manner, local chemical environments for disordered materials may be characterized, and via a re-sampling approach, error estimates for parameters produced. Program summaryProgram title: mqmasOPT Catalogue identifier: AEEC_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEEC_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 3650 No. of bytes in distributed program, including test data, etc.: 73 853 Distribution format: tar.gz Programming language: C, OCTAVE Computer: UNIX/Linux Operating system: UNIX/Linux Has the code been vectorised or parallelized?: Yes RAM: Example: (1597 powder angles) × (200 Samples) × (81 F2 frequency pts) × (31 F1 frequency points) = 3.5M, SMP AMD opteron Classification: 2.3 External routines: OCTAVE ( http://www.gnu.org/software/octave/), GNU Scientific Library ( http://www.gnu.org/software/gsl/), OPENMP ( http://openmp.org/wp/) Nature of problem: The optimal simulation and modeling of multiple quantum magic angle spinning NMR spectra, for general systems, especially those with mild to significant disorder. The approach outlined and implemented in C and OCTAVE also produces model parameter error estimates. Solution method: A model for each distinct chemical site is first proposed, for the individual contribution of crystallite orientations to the spectrum. This model is averaged over all powder angles [1], as well as the (stochastic) parameters; isotropic chemical shift and quadrupole coupling constant. The latter is accomplished via sampling from a bi-variate Gaussian distribution, using the Box-Muller algorithm to transform Sobol (quasi) random numbers [2]. A simulated annealing optimization is performed, and finally the non-linear jackknife [3] is applied in developing model parameter error estimates. Additional comments: The distribution contains a script, mqmasOpt.m, which runs in the OCTAVE language workspace. Running time: Example: (1597 powder angles) × (200 Samples) × (81 F2 frequency pts) × (31 F1 frequency points) = 58.35 seconds, SMP AMD opteron. References:S.K. Zaremba, Annali di Matematica Pura ed Applicata 73 (1966) 293. H. Niederreiter, Random Number Generation and Quasi-Monte Carlo Methods, SIAM, 1992. T. Fox, D. Hinkley, K. Larntz, Technometrics 22 (1980) 29.

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

2009-10-01

84

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

SciTech Connect

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

Rottstegge, J. [Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz (Germany); Arnold, M. [Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz (Germany); Herschke, L. [Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz (Germany); Glasser, G. [Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz (Germany); Wilhelm, M. [Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz (Germany); Spiess, H.W. [Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz (Germany)]. E-mail: spiess@mpip-mainz.mpg.de; Hergeth, W.D. [Wacker Polymer Systems GmbH and Co. KG, Johannes Hess Strasse 24, D-84483 Burghausen (Germany)

2005-12-15

85

On the acid-dealumination of USY zeolite: a solid state NMR investigation  

Microsoft Academic Search

The dealumination of USY (ultrastable Y) zeolites by nitric acid and oxalic acid treatment was systematically investigated by multinuclear solid-state NMR and MQ MAS NMR experiments. The results show that both acids are very effective in removing non-framework Al as well as framework Al but that aluminum is extracted from the lattice at a higher rate by oxalic acid even

Zhimin Yan; Ding Ma; Jianqin Zhuang; Xianchun Liu; Xiumei Liu; Xiuwen Hana; Xinhe Bao; Fuxiang Chang; Lei Xu; Zhongmin Liu

2003-01-01

86

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

87

Solid state NMR study of SEI formation in lithium ion batteries  

Microsoft Academic Search

Recently, rechargeable lithium ion batteries, which offer high energy density and long cycle life, are in great demand as power sources for our mobile electronic society. The formation of a solid electrolyte interphase (SEI) on the surface of electrodes in lithium ion batteries plays an essential role in their performance. This thesis presents solid state NMR and MAS NMR results

Dachun Zhao

2004-01-01

88

Precision and sensitivity optimization of quantitative measurements in solid state NMR  

Microsoft Academic Search

This work presents a methodology for optimizing the precision, accuracy and sensitivity of quantitative solid state NMR measurements based on the external reference method. It is shown that the sample must be exclusively located within and completely span the coil region where the NMR response is directly proportional to the sample amount. We describe two methods to determine this “quantitative”

Fabio Ziarelli; Stéphane Viel; Stéphanie Sanchez; David Cross; Stefano Caldarelli

2007-01-01

89

Location and orientation of adsorbed molecules in zeolites from solid-state REAPDOR NMR.  

SciTech Connect

The use of rotational echo adiabatic passage double resonance (REAPDOR) solid-state nuclear magnetic resonance (NMR) to determine the site location of an adsorbed polar molecule in a zeolite cage is presented. Nitrogen-15 labeled ammonia is used as a probe molecule to characterize the initial adsorption site in 3A zeolite molecular sieves. The relative position of the ammonia adsorption site in the cage is determined by measuring the internuclear distance between the N on ammonia and both a Na cation site and an Al framework environment using {sup 15}N/{sup 23}Na and {sup 15}N/{sup 27}Al REAPDOR NMR experiments, respectively. The measured internuclear distances are similar to a specific ammonia adsorption site for the zeolite 4A ammonia sorption complex located using X-ray diffraction. Additional details regarding the ammonia hydrogen-bonding environment can be extracted from {sup 1}H/{sup 23}Na and {sup 1}H/{sup 27}Al REAPDOR NMR measurements.

Alam, Todd Michael; Holland, Gregory P.

2005-01-01

90

[sup 13]C solid-state NMR study of ethylene oxidation over supported silver catalysts  

SciTech Connect

Solid-state NMR has been used to study the interaction of ethylene with oxygen in the absence of promoters and moderators over silica-supported silver catalysts. Experiments using nitrous oxide and oxygen as the oxidants have been carried out over Ag/SiO[sub 2] catalyst at temperature ranging from 298 to 613 K. Standard cross-polarization with magic angle spinning (CP/MAS), CP/MAS with dipolar dephasing, and single-pulse experiments have been applied to identify carbon-containing species that are formed on the surface of catalyst at various temperatures. Ethylene, acetic acid, carbon dioxide, ethane and an alkoxy species have been identified. Under the above experimental conditions, no ethylene oxide is detected by NMR. In pursuit of a better understanding of the chemistry taking place on the catalyst, silica-supported silver catalysts as well as pure silica were dosed with labeled ethylene, carbon dioxide and ethylene oxide. It was found that under conditions employed in this study, ethylene oxide reacts with both metal and silica support and thus cannot be observed as the reaction product. Ethylene oxide, however, has been observed after the saturation of silica surface with unlabeled ethylene oxide prior to ethylene oxidation. In conjunction with this project, the author has designed and constructed a multiport high vacuum glass apparatus which was used for sample preparation prior to the NMR experiments as well as chemisorption measurements and a single-coil double resonance probe.

Hosseini, S.

1992-01-01

91

Applications of high-resolution solid-state NMR spectroscopy in food science.  

PubMed

The principal applications of high-resolution solid-state NMR spectroscopy, in the field of food science, are reviewed, after a short general introduction, mainly focusing on the potential of these investigations, which are, today, routine tools for resolving technological problems. Selected examples of the applications in the field of food science of high-resolution solid-state NMR spectroscopy both in (13)C and in (1)H NMR particularly illustrative of the results obtainable are reported in some detail. PMID:18821771

Bertocchi, Fabio; Paci, Maurizio

2008-10-22

92

2D solid-state NMR analysis of inclusion in drug-cyclodextrin complexes.  

PubMed

The solubility of drug molecules can often be improved through preparation and delivery of cyclodextrin (CD) inclusion complexes. These drug-oligosaccharide complexes can be prepared in solution and converted to the solid state via methods such as lyophilization and spray-drying, or they can be prepared directly from solids by a variety of methods. The development of drug-CD complexes as solids allows for potential advantages in dosage form design, such as the preparation of layered formulations, and it also can yield improvements in chemical and physical stability. 2D solid-state NMR (SSNMR) methods provide a direct way to probe drug-CD interactions in solid complexes through dipolar interactions between nuclei within the drug and CD molecules. In this study, 2D heteronuclear and homonuclear correlation SSNMR experiments involving (1)H, (13)C, (19)F, and (31)P nuclei are used to demonstrate the inclusion of drug within the CD cavity in a variety of powder samples. To illustrate the general applicability of the SSNMR approach presented, examples are shown for the drugs diflunisal, adefovir dipivoxil, voriconazole, dexamethasone, and prednisolone in complexes with ?-CD, ?-CD, and sulfobutylether-substituted ?-CD. The quantitative analysis of included and free drug fractions in a solid drug-CD complex using SSNMR is also demonstrated. On the basis of these results, general approaches to the characterization of these materials using SSNMR are proposed. PMID:23009557

Vogt, Frederick G; Strohmeier, Mark

2012-11-01

93

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

94

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.

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

2012-01-01

95

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

PubMed

A simple procedure to effectively suppress background signals arising from various probe head components (e.g. stator, rotors, inserts) in solid state NMR is presented. Similarly to the ERETIC™ method, which uses an electronic signal as an internal standard for quantification, the proposed scheme is based on an electronically generated time-dependent signal that is injected into the receiver coil of the NMR probe head during signal acquisition. More specifically, the line shape, width and frequency of this electronic signal are determined by deconvoluting the background signal in the frequency domain. This deconvoluted signal is then converted into a time-dependent function through inverse Fourier Transform, which is used to generate the shaped pulse that is fed into the receiver coil during the acquisition of the Free Induction Decay. The power of the shaped pulse is adjusted to match the intensity of the background signal, and its phase is shifted by 180° with respect to the receiver reference phase. This so-called Electronic Mixing-Mediated Annihilation (EMMA) methodology is demonstrated here with a (13)C Single Pulse Magic Angle Spinning spectrum of an isotopically enriched (13)C histidine solid sample recorded under quantitative conditions. PMID:22578547

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

2012-05-01

96

Lithium NMR in Lithium-Carbon Solid State Compounds  

Microsoft Academic Search

\\u000a Historically, 7Li NMR started in 1946 with Li+ aqueous solutions whereas Li-alkyl where first studied in the early sixties. In spite of the importance of lithiated organic\\u000a compounds in organic synthesis and its high sensitivity, 7Li has not contributed so much to the development of NMR, like 1H, 13C, 17O and 15N because its predicted chemical shift range (5ppm) is

J. Conard; P. Lauginie

97

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

Microsoft Academic Search

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

Mads Bak; Jimmy T. Rasmussen; Niels Chr Nielsen

2000-01-01

98

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

99

Solid state (47,49)Ti, (87)Sr and (137)Ba NMR characterisation of mixed barium/strontium titanate perovskites.  

PubMed

Solid state (47,49)Ti, (137)Ba, (87)Sr NMR spectra have been recorded on BaxSrl-xTiO3 (0 solid state NMR shows great potential for characterising such systems since the quadrupolar parameters are very sensitive to any geometric deformation around the studied nucleus. (47,49)Ti NMR powder lineshapes appear strongly influenced by the presence of even a small amount of barium (or strontium) in the coordination second sphere of the probed titanium site: substitution of strontium by barium induces the broadening of the peaks, due to quadrupolar effects, while the isotropic chemical shift increases. (137)Ba NMR spectra exhibit a distribution of the quadrupolar interaction, that could be tentatively quantified, CQ increasing with the amount of strontium. Preliminary results were also obtained on (87)Sr NMR showing behaviour comparable to (137)Ba NMR, i.e. a broadening of the peaks due to an increasing quadrupolar interaction with the amount of barium distorting the environment of the strontium sites. PMID:15388178

Gervais, Christel; Veautier, Delphine; Smith, Mark E; Babonneau, Florence; Belleville, Philippe; Sanchez, Clément

2004-01-01

100

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

101

Solid-state 17O NMR in carbohydrates  

NASA Astrophysics Data System (ADS)

Solid-state 17O magic-angle spinning nuclear magnetic resonance measurements at 19.5 Tesla were performed on 17O-enriched methyl ?- D-galactopyranoside (4- 17O), methyl ?- D-glucopyranoside (2- 17O), methyl ?- D-glucopyranoside (4- 17O), methyl ?- D-glucopyranoside (6- 17O), and ?- D-glucopyranosyl (1 ? 6) ?- D-glucopyranoside (6- 17O). The 17O quadrupolar coupling constants and asymmetry parameters measured can be predicted with a model based entirely on the first-coordination sphere around oxygen. For the hydroxyl sites observed in the methyl glucosides, the quadrupolar coupling parameters are nearly identical, within 10% as predicted, given their nearly identical first-coordination sphere structures.

Sefzik, T. H.; Houseknecht, J. B.; Clark, T. M.; Prasad, S.; Lowary, T. L.; Gan, Z.; Grandinetti, P. J.

2007-02-01

102

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

PubMed

Membrane proteins catalyze reactions at the cell membrane and facilitate thetransport of molecules or signals across the membrane. Recently researchers have made great progress in understanding the structural biology of membrane proteins, mainly based on X-ray crystallography. In addition, the application of complementary spectroscopic techniques has allowed researchers to develop a functional understanding of these proteins. Solid-state NMR has become an indispensable tool for the structure-function analysis of insoluble proteins and protein complexes. It offers the possibility of investigating membrane proteins directly in their environment, which provides essential information about the intrinsic coupling of protein structure and functional dynamics within the lipid bilayer. However, to date, researchers have hardly explored the enzymology of mem-brane proteins. In this Account, we review the perspectives for investigating membrane-bound enzymes by solid-state NMR. Understanding enzyme mechanisms requires access to kinetic parameters, structural analysis of the catalytic center, knowledge of the 3D structure and methods to follow the structural dynamics of the enzyme during the catalytic cycle. In principle, solid-state NMR can address all of these issues. Researchers can characterize the enzyme kinetics by observing substrate turnover within the membrane or at the membrane interphase in a time-resolved fashion as shown for diacylglycerol kinase. Solid-state NMR has also provided a mechanistic understanding of soluble enzymes including triosephosphate isomerase (TIM) and different metal-binding proteins, which demonstrates a promising perspective also for membrane proteins. The increasing availability of high magnetic fields and the development of new experimental schemes and computational protocols have made it easier to determine 3D structure using solid-state NMR. Dynamic nuclear polarization, a key technique to boost sensitivity of solid-state NMR at low temperatures, can help with the analysis of thermally trapped catalytic intermediates, while methods to improve signal-to-noise per time unit enable the real-time measurement of kinetics of conformational changes during the catalytic cycle. PMID:23745719

Ullrich, Sandra J; Glaubitz, Clemens

2013-09-17

103

sup 13 C solid-state NMR study of ethylene oxidation over supported silver catalysts  

SciTech Connect

Solid-state NMR has been used to study the interaction of ethylene with oxygen in the absence of promoters and moderators over silica-supported silver catalysts. Experiments using nitrous oxide and oxygen as the oxidants have been carried out over Ag/SiO{sub 2} catalysts at temperature ranging from 298 to 613 K. Standard cross-polarization with magic angle spinning (CP/MAS), CP/MAS with dipolar dephasing, and single-pulse experiments have been applied to identify carbon containing species that are formed on the surface of catalyst at various temperatures. Ethylene, acetic acid, carbon dioxide, ethane and an alkoxy species have been identified. Under the above experimental conditions, no ethylene oxide is detected by NMR. In pursuit of a better understanding of the chemistry taking place on the catalyst, silica-supported silver catalysts as well as pure silica were dosed with labeled ethylene, carbon dioxide and ethylene oxide. It was found that under conditions employed in this study, ethylene oxide reacts with both metal and silica support and thus can not be observed as the reaction product. Ethylene oxide, however, has been observed after saturation of silica surface with unlabeled ethylene oxide prior to ethylene oxidation. A multiport high vacuum glass apparatus was developed along with a single-coil double resonance probe.

Hosseini, S.

1992-07-21

104

{sup 13}C solid-state NMR study of ethylene oxidation over supported silver catalysts  

SciTech Connect

Solid-state NMR has been used to study the interaction of ethylene with oxygen in the absence of promoters and moderators over silica-supported silver catalysts. Experiments using nitrous oxide and oxygen as the oxidants have been carried out over Ag/SiO{sub 2} catalysts at temperature ranging from 298 to 613 K. Standard cross-polarization with magic angle spinning (CP/MAS), CP/MAS with dipolar dephasing, and single-pulse experiments have been applied to identify carbon containing species that are formed on the surface of catalyst at various temperatures. Ethylene, acetic acid, carbon dioxide, ethane and an alkoxy species have been identified. Under the above experimental conditions, no ethylene oxide is detected by NMR. In pursuit of a better understanding of the chemistry taking place on the catalyst, silica-supported silver catalysts as well as pure silica were dosed with labeled ethylene, carbon dioxide and ethylene oxide. It was found that under conditions employed in this study, ethylene oxide reacts with both metal and silica support and thus can not be observed as the reaction product. Ethylene oxide, however, has been observed after saturation of silica surface with unlabeled ethylene oxide prior to ethylene oxidation. A multiport high vacuum glass apparatus was developed along with a single-coil double resonance probe.

Hosseini, S.

1992-07-21

105

Interactions of lipopolysaccharide with lipid membranes, raft models - a solid state NMR study.  

PubMed

Lipopolysaccharide (LPS) is a major component of the external leaflet of bacterial outer membranes, key pro-inflammatory factor and an important mediator of host-pathogen interactions. In host cells it activates the complement along with a pro-inflammatory response via a TLR4-mediated signalling cascade and shows preference for cholesterol-containing membranes. Here, we use solid state (13)C and (31)P MAS NMR to investigate the interactions of LPS from three bacterial species, Brucella melitensis, Klebsiella pneumoniae and Escherichia coli, with mixed lipid membranes, raft models. All endotoxin types are found to be pyrophosphorylated and Klebsiellar LPS is phosphonylated, as well. Carbon-13 MAS NMR indicates an increase in lipid order in the presence of LPS. Longitudinal (31)P relaxation, providing a direct probe of LPS molecular and segmental mobility, reveals a significant reduction in (31)P T1 times and lower molecular mobility in the presence of ternary lipid mixtures. Along with the ordering effect on membrane lipid, this suggests a preferential partitioning of LPS into ordered bilayer sphingomyelin/cholesterol-rich domains. We hypothesise that this is an important evolutionary drive for the selection of GPI-anchored raft-associated LPS-binding proteins as a first line of response to membrane-associated LPS. PMID:23567915

Ciesielski, Filip; Griffin, David C; Rittig, Michael; Moriyón, Ignacio; Bonev, Boyan B

2013-08-01

106

Efficient polarization transfer between spin-1/2 and 14N nuclei in solid-state MAS NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Polarization transfer between spin-1/2 nuclei and quadrupolar spin-1 nuclei such as 14N 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 14N 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 14N is replaced with 15N. The alternative strategy of using the abundant 14N spins calls for methods enabling efficient polarization transfer between 14N and its binding partners. This work demonstrates that the recently introduced RESPIRATIONCP transfer method can be optimized to achieve efficient 1H ?14N polarization transfer under magic angle spinning conditions. The method is demonstrated numerically and experimentally on powder samples of NH4NO3 and L-alanine.

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

2014-07-01

107

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.

Hu, Kan-Nian; Tycko, Robert

2010-01-01

108

Manifestations of nuclear anapole moments in solid-state NMR  

SciTech Connect

We suggest using insulating garnets doped by rare-earth ions for measurements of nuclear anapole moments. A parity violating shift of the NMR frequency arises due to the combined effect of the lattice crystal field and the anapole moment of the rare-earth nucleus. We show that there are two different observable effects related to frequency: (1) a shift of the NMR frequency in an external electric field applied to the solid; the value of the shift is about {delta}{nu}{sub 1}{approx}10{sup -5} Hz with E=10 kV/cm; (2) a splitting of the NMR line into two lines. The second effect is independent of the external electric field. The value of the splitting is about {delta}{nu}{sub 2}{approx}0.5 Hz and it depends on the orientation of the crystal with respect to magnetic field. Both estimates are presented for a magnetic field of about 10 T. We also discuss a radio frequency electric field and a static macroscopic magnetization caused by the nuclear anapole moment.

Mukhamedjanov, T.N.; Sushkov, O.P.; Cadogan, J.M. [School of Physics, University of New South Wales, Sydney 2052 (Australia)

2005-01-01

109

Natural abundance solid-state 67Zn NMR characterization of microporous zinc phosphites and zinc phosphates at ultrahigh magnetic field.  

PubMed

Zinc-phosphite and -phosphate based microporous materials are crystalline open framework materials with potential industrial applications. Although (31)P MAS NMR has been used for characterization of these materials, the local environments around zinc centres have never been directly probed by solid-state NMR due to the many unfavourable NMR characteristics of (67)Zn. In this work, we have characterized the local structure around the Zn centres in several representative microporous zinc phosphites and zinc phosphates by acquiring natural abundance (67)Zn solid-state NMR spectra at ultrahigh magnetic field of 21.1 T. The observed line-shapes are mainly determined by the second order quadrupolar interaction. The NMR tensor parameters were extracted from the spectra and are related to the local geometry around the Zn centre. Computational study of the electric field gradient (EFG) tensor at Zn was performed using hybrid density functional theory (DFT) calculations at B3LYP level of theory on model clusters. The calculations using Projector Augmented-Wave (PAW) method were also carried out with the CASTEP code wherever it was possible. The work has shown that it is possible to study Zn environments in porous materials which often have very low Zn concentration by natural abundance (67)Zn SSNMR at very high magnetic fields. PMID:21850324

Sutrisno, Andre; Liu, Li; Xu, Jun; Huang, Yining

2011-10-01

110

Structural Dynamics and Conformational Equilibria of SERCA Regulatory Proteins in Membranes by Solid-State NMR Restrained Simulations.  

PubMed

Solid-state NMR spectroscopy is emerging as a powerful approach to determine structure, topology, and conformational dynamics of membrane proteins at the atomic level. Conformational dynamics are often inferred and quantified from the motional averaging of the NMR parameters. However, the nature of these motions is difficult to envision based only on spectroscopic data. Here, we utilized restrained molecular dynamics simulations to probe the structural dynamics, topology and conformational transitions of regulatory membrane proteins of the calcium ATPase SERCA, namely sarcolipin and phospholamban, in explicit lipid bilayers. Specifically, we employed oriented solid-state NMR data, such as dipolar couplings and chemical shift anisotropy measured in lipid bicelles, to refine the conformational ensemble of these proteins in lipid membranes. The samplings accurately reproduced the orientations of transmembrane helices and showed a significant degree of convergence with all of the NMR parameters. Unlike the unrestrained simulations, the resulting sarcolipin structures are in agreement with distances and angles for hydrogen bonds in ideal helices. In the case of phospholamban, the restrained ensemble sampled the conformational interconversion between T (helical) and R (unfolded) states for the cytoplasmic region that could not be observed using standard structural refinements with the same experimental data set. This study underscores the importance of implementing NMR data in molecular dynamics protocols to better describe the conformational landscapes of membrane proteins embedded in realistic lipid membranes. PMID:24940774

De Simone, Alfonso; Mote, Kaustubh R; Veglia, Gianluigi

2014-06-17

111

ICMRBS founder’s medal 2006: Biological solid-state NMR, methods and applications  

Microsoft Academic Search

Solid-state NMR (ssNMR) provides increasing possibilities to study structure and dynamics of biomolecular systems. Our group\\u000a has been interested in developing ssNMR-based approaches that are applicable to biomolecules of increasing molecular size\\u000a and complexity without the need of specific isotope-labelling. Methodological aspects ranging from spectral assignments to\\u000a the indirect detection of proton–proton contacts in multi-dimensional ssNMR are discussed and applied

Marc Baldus

2007-01-01

112

Aging effects on vulcanized natural rubber studied by high resolution solid state 13C-NMR  

Microsoft Academic Search

The vulcanization chemistry, network formation and thermal oxidative aging effects of unfilled and carbon-black filled natural rubber vulcanized with organic peroxide, efficient vulcanization (EV) system and conventional sulfur system are studied by solid state 13C-NMR spectroscopy. Cis–trans isomerization and different sulfide structures are detected and identified through the chemical shift values of the extra NMR lines, which are observed in

J. Y Buzaré; G Silly; J Emery; G Boccaccio; E Rouault

2001-01-01

113

The stability of nanosized HZSM-5 zeolite: a high-resolution solid-state NMR study  

Microsoft Academic Search

The thermal and hydrothermal stabilities of HZSM-5 zeolites with crystal sizes less than 100 nm have been studied by multinuclear solid-state NMR, combined with BET and XRD. As evidenced by 27Al and 29Si MAS as well as their corresponding cross-polarization\\/MAS NMR investigations, the thermal stability of nanosized HZSM-5 is not so good as that of microsized HZSM-5. This is due

Weiping Zhang; Xiuwen Han; Xiumei Liu; Xinhe Bao

2001-01-01

114

Dynamic Structure of a Protein Hydrogel:  A Solid-State NMR Study  

Microsoft Academic Search

C and 15 N solid-state NMR spectroscopy has been used to study the dynamic structure of a genetically engineered multidomain protein hydrogel that contains two leucine-zipper domains and a central polyelectrolyte domain. 13 C NMR spectra show that on the microsecond time scale the central domain is isotropically mobile while the leucine-zipper domains are rigid. This supports the hypothesis that

D. A. Tirrell; M. Hong; W. A. Petka; T. P. Russell

2001-01-01

115

Solid-state NMR applied to photosynthetic light-harvesting complexes  

Microsoft Academic Search

This short review describes how solid-state NMR has provided a mechanistic and electronic picture of pigment–protein and pigment–pigment\\u000a interactions in photosynthetic antenna complexes. NMR results on purple bacterial antenna complexes show how the packing of\\u000a the protein and the pigments inside the light-harvesting oligomers induces mutual conformational stress. The protein scaffold\\u000a produces deformation and electrostatic polarization of the BChl macrocycles

Anjali Pandit; Huub J. M. de Groot

116

Coil Design for Large-Volume High B 1Homogeneity for Solid-State NMR Applications  

Microsoft Academic Search

The design of a solenoidal NMR coil with high-B1homogeneity for high-frequency solid-state NMR is described. The coil is made of thin ribbon of continuously variable width. The width is varied to minimize inhomogeneity in the axial direction. The field distribution throughout the entire volume of the sample was taken into account. The gap between turns is constant and kept small

A. F. Privalov; S. V. Dvinskikh; H.-M. Vieth

1996-01-01

117

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

118

Blends of polycaprolactone with polyvinylalcohol: a DSC, optical microscopy and solid state NMR study  

Microsoft Academic Search

Blend films of polycaprolactone (PCL) and polyvinylalcohol (PVAl) have been obtained by evaporation of a solution of both components in hexafluoroisopropanol. The miscibility of the polymers in the amorphous part of the blend has been studied by conventional methods (optical microscopy, DSC and FTIR) and by solid state NMR. Phase separation is observed in the melt. The absence of any

C. De Kesel; C. Lefèvre; J. B. Nagy; C. David

1999-01-01

119

sup 13C solid-state NMR study of ethylene oxidation over supported silver catalysts.  

National Technical Information Service (NTIS)

Solid-state NMR has been used to study the interaction of ethylene with oxygen in the absence of promoters and moderators over silica-supported silver catalysts. Experiments using nitrous oxide and oxygen as the oxidants have been carried out over Ag/SiO(...

S. Hosseini

1992-01-01

120

Resonator with reduced sample heating and increased homogeneity for solid-state NMR  

Microsoft Academic Search

In the application of solid-state NMR to many systems, the presence of radiofrequency (rf) electric fields inside classical solenoidal coils causes heating of lossy samples. In particular, this is critical for proteins in ionic buffers. Rf sample heating increases proportional to frequency which may result in the need to reduce the rf pulse power to prevent partial or total sample

Alexander Krahn; Uwe Priller; Lyndon Emsley; Frank Engelke

2008-01-01

121

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

PubMed

The molecular dynamics and structural organization of mouse epidermal keratin intermediate filaments (IF) have been studied via solid-state nuclear magnetic resonance (NMR) experiments performed on IF labeled both in vivo and in vitro with isotopically enriched amino acids. As a probe of the organization of the peripheral glycine-rich end domains of the IF, carbon-13 NMR experiments have been performed on subfilamentous forms (prekeratin) and on IF reassembled in vitro that had been labeled with either [1-13C]glycine or [2-13C]glycine, as more than 90% of the glycines of the keratins are located in the end domains. Although cross-labeling to seryl residues was observed, the proportion of serine located in the end domains is nearly the same as that for glycine. Measurements of carbon relaxation times, nuclear Overhauser enhancements, and signal intensities show that the motions of the peptide backbone in the end domains are effectively isotropic, with average correlation times distributed over the range of 0.2-20 ns. These results indicate that the end domains of IF are remarkably flexible and have little or no structural order. To probe the structural organization of the coiled-coil rod domains of the IF, separate samples of native keratin IF, raised in primary tissue culture, were labeled with L-[1-13C]leucine, L-[2H10]leucine, or L-[2,3,3-2H3]leucine, as greater than 90% of the leucyl residues of the keratin IF types studied are located in the coiled coils which form the central core of IF.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2460129

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

1988-07-26

122

Sum frequency generation and solid-state NMR study of the structure, orientation, and dynamics of polystyrene-adsorbed peptides  

PubMed Central

The power of combining sum frequency generation (SFG) vibrational spectroscopy and solid-state nuclear magnetic resonance (ssNMR) spectroscopy to quantify, with site specificity and atomic resolution, the orientation and dynamics of side chains in synthetic model peptides adsorbed onto polystyrene (PS) surfaces is demonstrated in this study. Although isotopic labeling has long been used in ssNMR studies to site-specifically probe the structure and dynamics of biomolecules, the potential of SFG to probe side chain orientation in isotopically labeled surface-adsorbed peptides and proteins remains largely unexplored. The 14 amino acid leucine-lysine peptide studied in this work is known to form an ?-helical secondary structure at liquid-solid interfaces. Selective, individual deuteration of the isopropyl group in each leucine residue was used to probe the orientation and dynamics of each individual leucine side chain of LK?14 adsorbed onto PS. The selective isotopic labeling methods allowed SFG analysis to determine the orientations of individual side chains in adsorbed peptides. Side chain dynamics were obtained by fitting the deuterium ssNMR line shape to specific motional models. Through the combined use of SFG and ssNMR, the dynamic trends observed for individual side chains by ssNMR have been correlated with side chain orientation relative to the PS surface as determined by SFG. This combination provides a more complete and quantitative picture of the structure, orientation, and dynamics of these surface-adsorbed peptides than could be obtained if either technique were used separately.

Weidner, Tobias; Breen, Nicholas F.; Li, Kun; Drobny, Gary P.; Castner, David G.

2010-01-01

123

NMR study of the solution-state dynamics and solid-state structure of tri-n-butyltin fluoride  

SciTech Connect

Dynamics and structure of tri-n-butyltin fluoride in n-hexane solutions were probed using (tin-119) nuclear magnetic resonance spin relaxation methodologies. Significant relaxation-induced polarization transfer effects were observed and exploited. The experimental observations indicate that the tri-n-butyl fluoride exists in a polymeric form in solution. For a 0.10% (w/w) solution at 25 [degree]C, NMR reveals significant orientational/exchange relaxation on both the microsecond and nanosecond time scales. Solution-state and solid-state parameters are compared and contrasted. 26 refs., 3 figs., 1 tab.

Kim, Y.W.; Labouriau, A.; Taylor, C.M.; Earl, W.L.; Werbelow, L.G. (Los Alamos National Lab., NM (United States))

1994-05-05

124

Studies of Molecular Dynamics by Solid State Deuterium NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

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

Zhao, Baiyi

125

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

126

Structure of a protein determined by solid-state magic-angle-spinning NMR spectroscopy  

NASA Astrophysics Data System (ADS)

The determination of a representative set of protein structures is a chief aim in structural genomics. Solid-state NMR may have a crucial role in structural investigations of those proteins that do not easily form crystals or are not accessible to solution NMR, such as amyloid systems or membrane proteins. Here we present a protein structure determined by solid-state magic-angle-spinning (MAS) NMR. Almost complete 13C and 15N resonance assignments for a micro-crystalline preparation of the ?-spectrin Src-homology 3 (SH3) domain formed the basis for the extraction of a set of distance restraints. These restraints were derived from proton-driven spin diffusion (PDSD) spectra of biosynthetically site-directed, labelled samples obtained from bacteria grown using [1,3-13C]glycerol or [2-13C]glycerol as carbon sources. This allowed the observation of long-range distance correlations up to ~7Å. The calculated global fold of the ?-spectrin SH3 domain is based on 286 inter-residue 13C-13C and six 15N-15N restraints, all self-consistently obtained by solid-state MAS NMR. This MAS NMR procedure should be widely applicable to small membrane proteins that can be expressed in bacteria.

Castellani, Federica; van Rossum, Barth; Diehl, Annette; Schubert, Mario; Rehbein, Kristina; Oschkinat, Hartmut

2002-11-01

127

Magnetically oriented dodecylphosphocholine bicelles for solid-state NMR structure analysis.  

PubMed

A mixture of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) with the short-chain detergent n-dodecylphosphocholine (DPC) is introduced here as a new membrane-mimetic bicelle system for solid-state NMR structure analysis of membrane proteins in oriented samples. Magnetically aligned DMPC/DPC bicelles are stable over a range of concentrations, with an optimum lipid ratio of q=3:1, and they can be flipped with lanthanide ions. The advantage of DMPC/DPC over established bicelle systems lies in the possibility to use one and the same detergent for purification and NMR analysis of the membrane protein, without any need for detergent exchange. Furthermore, the same batch of protein can be studied in both micelles and bicelles, using liquid-state and solid-state NMR, respectively. The applicability of the DMPC/DPC bicelles is demonstrated here with the (15)N-labeled transmembrane protein TatA. PMID:22274567

Nolandt, Olga V; Walther, Torsten H; Grage, Stephan L; Ulrich, Anne S

2012-05-01

128

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

129

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

PubMed

This article presents some of the solid-state NMR (SSNMR) techniques used in the pharmaceutical and biomedical research. Solid-state magic angle spinning (MAS) NMR provides structural information on powder amorphous solids for which single-crystal diffraction structures cannot be obtained. NMR is non-destructive; the powder sample may be used for further studies. Quantitative results can be obtained, although solid-state NMR spectra are not normally quantitative. As compared with other techniques, MAS NMR is insensitive and requires a significant amount of the powder sample (2-100mg) to fill the 1.3-7 mm ZrO2 rotor. This is its main drawback, since natural compounds isolated from plants, microorganisms or cell cultures are difficult to obtain in quantities higher than a few milligrams. Multinuclear MAS NMR routinely uses (1)H and (13)C nuclei, less frequently (15)N, (19)F, (31)P, (77)Se, (29)Si, (43)Ca or (23)Na. The article focuses on the pharmaceutical applications of SSNMR, the studies were aimed to control over manufacturing processes (e.g. crystallization and milling) investigation of chemical and physical stability of solid forms both as pure drug and in a formulated product. SSNMR is used in combination with some other analytical methods (DSC, XRD, FT-IR) and theoretical calculations of NMR parameters. Biologically active compounds, such as amino acids and small peptides, steroids and flavonoids were studied by SSNMR methods (part 4) providing valuable structural information. The SSNMR experiments performed on biopolymers and large natural products like proteins, cellulose and lipid layers are commented upon briefly in part 5. PMID:24173236

Paradowska, Katarzyna; Wawer, Iwona

2014-05-01

130

Computation of Orientational Averages in Solid-State NMR by Gaussian Spherical Quadrature  

NASA Astrophysics Data System (ADS)

We investigate Gaussian spherical quadrature as a method for calculating orientational averages in solid-state NMR. For the case of magic-angle-spinning sideband amplitudes of isolated spins-1/2, we demonstrate the superiority of Gaussian spherical quadrature over other orientational averaging methods. Depending on the shift anisotropy parameters and the desired accuracy, the computation speed is enhanced by a large factor (between two and many hundreds). In addition, a method for improving any present sampling scheme is devised. Such schemes are called SHREWD (Spherical Harmonic Reduction or Elimination by a Weighted Distribution). The role of orientational symmetry in solid-state NMR is explored. We also discuss the limitations of the Gaussian spherical quadrature methods.

Edén, Mattias; Levitt, Malcolm H.

1998-06-01

131

Structural investigation of e-beam cured epoxy resins through solid state NMR  

NASA Astrophysics Data System (ADS)

In this paper the network structure of e-beam cured DGEBF based epoxy resins is investigated. Two epoxy systems, having different reactivity and cured in different process conditions, were analyzed through solid state NMR spectroscopy. The analysis shows that the more reactive system has higher cross-linking density and higher uniformity of network distribution. Similar information were obtained, in a previous work, on the same systems through dynamic mechanical thermal analysis. It is worth noting that unlike DMTA tests, which interfere with the molecular structure of the analyzed material, due to the heating during the analysis itself, more reliable information, without any artefact, are obtained by solid state NMR, carried out at constant room temperature.

Alessi, Sabina; Spinella, Alberto; Caponetti, Eugenio; Dispenza, Clelia; Spadaro, Giuseppe

2012-09-01

132

Characterization of Sidegroup Packing in Methacrylates and Poly(Vinyl Acetate) by Solid-State NMR  

Microsoft Academic Search

The local packing of sidegroups in poly(vinyl acetate), PVAc, poly(ethyl methacrylate), PEMA, and poly(methyl methacrylate), PMMA, was studied by two-dimensional solid-state NMR experiments applied to ^13COO-labeled polymers. Relative sidegroup orientations were determined by double-quantum chemical-shift-anisotropy correlation, while intergroup distances were measured from dipolar splittings. The spectra of PEMA show that while sidegroups are not exactly parallel to each other, the

Douglas J. Harris; Tito J. Bonagamba; Klaus Schmidt-Rohr

2000-01-01

133

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

134

Computation of Orientational Averages in Solid-State NMR by Gaussian Spherical Quadrature  

Microsoft Academic Search

We investigate Gaussian spherical quadrature as a method for calculating orientational averages in solid-state NMR. For the case of magic-angle-spinning sideband amplitudes of isolated spins-1\\/2, we demonstrate the superiority of Gaussian spherical quadrature over other orientational averaging methods. Depending on the shift anisotropy parameters and the desired accuracy, the computation speed is enhanced by a large factor (between two and

Mattias Edén; Malcolm H. Levitt

1998-01-01

135

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

Microsoft Academic Search

Unilateral and solid-state nuclear magnetic resonance (NMR) analyses were performed on a parchment fragment of the Dead Sea\\u000a Scroll (DSS). The analyzed sample belongs to the collection of non-inscribed and nontreated fragments of known archaeological\\u000a provenance from the John Rylands University Library in Manchester. Therefore, it can be considered as original DSS material\\u000a free from any contamination related to the

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

136

Solid state 77Se NMR investigations on arsenic-selenium glasses and crystals  

Microsoft Academic Search

Some resolved solid state 77Se NMR spectra are presented in the AsxSe1?x glass family at ambient temperature. They exhibit three different kinds of Se environments. A comparison with the parent crystalline phases permits to assign the lines to Se-Se-Se, Se-Se-As and As-Se-As Se atom neighborhoods. The measurements of the relative intensities of the lines prove the validity of the intermediate

Bruno Bureau; Johann Troles; Marie LeFloch; Frédéric Smektala; Gilles Silly; Jacques Lucas

2003-01-01

137

Solid-state NMR: a powerful tool for characterization of metal-organic frameworks.  

PubMed

Metal-organic frameworks (MOFs) are a new type of porous materials with numerous current and potential applications in many areas including ion-exchange, catalysis, sensing, separation, molecular recognition, drug delivery and, in particular, gas storage. Solid-state NMR (SSNMR) has played a pivotal role in structural characterization and understanding of host-guest interactions in MOFs. This article provides an overview on application of SSNMR to MOF systems. PMID:23131545

Sutrisno, Andre; Huang, Yining

2013-02-01

138

Solid-state NMR conformational studies of a melittin-inhibitor complex  

Microsoft Academic Search

Melittin is a cytolytic peptide whose biological activity is lost upon binding to a six-residue peptide, Ac-IVIFDC-NH2, with which it forms a highly insoluble complex. As a result, the structural analysis of the interaction between the two peptides is difficult. Solid-state NMR spectroscopy was used to study the interaction between melittin and the peptide inhibitor. Location of the binding site

Y.-H. Lam; C. Morton; F. Separovic

2002-01-01

139

Analysis of RF heating and sample stability in aligned static solid-state NMR spectroscopy  

Microsoft Academic Search

Sample instability during solid-state NMR experiments frequently arises due to RF heating in aligned samples of hydrated lipid bilayers. A new, simple approach for estimating sample temperature is used to show that, at 9.4T, sample heating depends mostly on 1H decoupling power rather than on 15N irradiation in PISEMA experiments. Such heating for different sample preparations, including lipid composition, salt

Conggang Li; Yiming Mo; Jun Hu; Eduard Chekmenev; Changlin Tian; Fei Philip Gao; Riqiang Fu; Peter Gor’kov; William Brey; Timothy A. Cross

2006-01-01

140

Direct observation of zeolite a synthesis by in situ solid-state NMR  

SciTech Connect

This paper describes the use of in situ solid-state NMR and X-ray powder diffraction to study the real-time synthesis of zeolite. In particular {sup 27}Al and {sup 29}Si are used to monitor the growth in situ X-ray diffraction study was used to investigate the development of long range order of the material. Conclusions concerning the mechanism of the formation of zeolite A are proposed. 28 refs., 12 figs., 2 tabs.

Shi, J.; Anderson, M.W. [UMIST, Manchester (United Kingdom)] [UMIST, Manchester (United Kingdom); Carr, S.W. [Unilever Research, Merseyide (United Kingdom)] [Unilever Research, Merseyide (United Kingdom)

1996-02-01

141

Hydrolysis of Pyrophosphate in a Highly Calcareous Soil: A Solid-State Phosphorus31 NMR Study  

Microsoft Academic Search

PyrophosphateisthemainformofcondensedPinthefluidfertilizer ammonium polyphosphate (APP). When APP is applied to soil, pyro- phosphate is hydrolyzed to orthophosphate. Hydrolysis of pyrophos- phatewas investigated in a highly calcareous soil over 3 wk. Changes in P speciation were measured using solid-state 31 P nuclear magnetic resonance (NMR) spectroscopy for dried soil samples and ion chro- matography for NaOH extracts. Both techniques showed a decrease

T. M. McBeath; R. J. Smernik; E. Lombi; M. J. McLaughlin

142

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

143

Solid-state NMR evaluation of the silane structure on nanoporous silica fillers  

Microsoft Academic Search

Coupling agents play a critical role in the function of organic\\/inorganic composite materials. However, the structure of these compounds as they reside on the filler surface is not well understood. Solid-state CP-MAS 13C and Si FT-NMR were used to study the coupling of ?-methacryloxypropyltrimethoxysilane (MPS) on experimental nanoporous silica fillers following exposure to different coupling environments. The progressive consumption of

Jiazhong Luo; John Lannutti; Robert Seghi

2001-01-01

144

sup 13 C solid-state NMR study of ethylene oxidation over supported silver catalysts  

Microsoft Academic Search

Solid-state NMR has been used to study the interaction of ethylene with oxygen in the absence of promoters and moderators over silica-supported silver catalysts. Experiments using nitrous oxide and oxygen as the oxidants have been carried out over Ag\\/SiOâ catalysts at temperature ranging from 298 to 613 K. Standard cross-polarization with magic angle spinning (CP\\/MAS), CP\\/MAS with dipolar dephasing, and

Hosseini

1992-01-01

145

[sup 13]C solid-state NMR study of ethylene oxidation over supported silver catalysts  

Microsoft Academic Search

Solid-state NMR has been used to study the interaction of ethylene with oxygen in the absence of promoters and moderators over silica-supported silver catalysts. Experiments using nitrous oxide and oxygen as the oxidants have been carried out over Ag\\/SiO[sub 2] catalyst at temperature ranging from 298 to 613 K. Standard cross-polarization with magic angle spinning (CP\\/MAS), CP\\/MAS with dipolar dephasing,

Hosseini

1992-01-01

146

A (2)H solid-state NMR study of the effect of antimicrobial agents on intact Escherichia coli without mutating.  

PubMed

Solid-state nuclear magnetic resonance (NMR) is a useful tool to probe the organization and dynamics of phospholipids in bilayers. The interactions of molecules with membranes are usually studied with model systems; however, the complex composition of biological membranes motivates such investigations on intact cells. We have thus developed a protocol to deuterate membrane phospholipids in Escherichia coli without mutating to facilitate (2)H solid-state NMR studies on intact bacteria. By exploiting the natural lipid biosynthesis pathway and using perdeuterated palmitic acid, our results show that 76% deuteration of the phospholipid fatty acid chains was attained. To verify the responsiveness of these membrane-deuterated E. coli, the effect of known antimicrobial agents was studied. (2)H solid-state NMR spectra combined to spectral moment analysis support the insertion of the antibiotic polymyxin B lipid tail in the bacterial membrane. The use of membrane-deuterated bacteria was shown to be important in cases where antibiotic action of molecules relies on the interaction with lipopolysaccharides. This is the case of fullerenol nanoparticles which showed a different effect on intact cells when compared to dipalmitoylphosphatidylcholine/dipalmitoylphosphatidylglycerol membranes. Our results also suggest that membrane rigidification could play a role in the biocide activity of the detergent cetyltrimethyammonium chloride. Finally, the deuterated E. coli were used to verify the potential antibacterial effect of a marennine-like pigment produced by marine microalgae. We were able to detect a different perturbation of the bacteria membranes by intra- and extracellular forms of the pigment, thus providing valuable information on their action mechanism and suggesting structural differences. PMID:22989726

Tardy-Laporte, Catherine; Arnold, Alexandre A; Genard, Bertrand; Gastineau, Romain; Morançais, Michèle; Mouget, Jean-Luc; Tremblay, Réjean; Marcotte, Isabelle

2013-02-01

147

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

148

Solid-State NMR of a Large Membrane Protein by Paramagnetic Relaxation Enhancement  

PubMed Central

Membrane proteins play an important role in many biological functions. Solid-state NMR spectroscopy is uniquely suited for studying structure and dynamics of membrane proteins in a membranous environment. The major challenge to obtain high quality solid-state NMR spectra of membrane proteins is sensitivity, due to limited quantities of labeled high-molecular-weight proteins. Here we demonstrate the incorporation of paramagnetic metal (Cu2+) ions, through either EDTA or a chelator lipid, into membrane protein samples for rapid data collection under fast magic-angle spinning (MAS) and low power 1H decoupling. Spectral sensitivity of DsbB (20 kDa), an integral membrane protein, more than doubles in the same experimental time due to 1H T1 relaxation enhancement by Cu2+ ions, with DsbB native fold and active site intact. This technique can be implemented to acquire multidimensional solid-state NMR spectra for chemical shift assignments and structure elucidation of large membrane proteins with small sample quantities.

Tang, Ming; Berthold, Deborah A.; Rienstra, Chad M.

2011-01-01

149

Environmentally friendly flame retardants. A detailed solid-state NMR study of melamine orthophosphate.  

PubMed

We used solid-state NMR spectroscopy to gain detailed information about the proton positions, proximities and the hydrogen-bonding network in the environmentally friendly flame retardant melamine orthophosphate (MP). High-resolution proton one- and two-dimensional solid-state NMR spectra were obtained at high external magnetic field in combination with fast magic angle spinning of the sample. Furthermore, we recorded homo- and heteronuclear correlation spectra of types (15)N–(15)N, (1)H–(13)C, (1)H–(15)N and (1)H–(31)P. In addition, we determined the geometry of the NH and NH(2) groups in MP by (15)N–(1)H heteronuclear recoupling experiments.We were able to completely assign the different isotropic chemical shifts in MP. Furthermore, we could identify the protonation of the melamine and orthophosphate moieties. The experimental results are discussed in connection with the structural model obtained by powder X-ray diffraction together with a combined molecular modeling-Rietveld refinement approach (De Ridder et al. Helv. Chim. Acta 2004; 87: 1894). We show that the geometry of the NH2 groups can only be successfully estimated by solid-state NMR. PMID:18157843

Brinkmann, Andreas; Litvinov, Victor M; Kentgens, Arno P M

2007-12-01

150

Solid-state NMR (31)P paramagnetic relaxation enhancement membrane protein immersion depth measurements.  

PubMed

Paramagnetic relaxation enhancement (PRE) is a widely used approach for measuring long-range distance constraints in biomolecular solution NMR spectroscopy. In this paper, we show that (31)P PRE solid-state NMR spectroscopy can be utilized to determine the immersion depth of spin-labeled membrane peptides and proteins. Changes in the (31)P NMR PRE times coupled with modeling studies can be used to describe the spin-label position/amino acid within the lipid bilayer and the corresponding helical tilt. This method provides valuable insight on protein-lipid interactions and membrane protein structural topology. Solid-state (31)P NMR data on the 23 amino acid ?-helical nicotinic acetylcholine receptor nAChR M2? transmembrane domain model peptide followed predicted behavior of (31)P PRE rates of the phospholipid headgroup as the spin-label moves from the membrane surface toward the center of the membrane. Residue 11 showed the smallest changes in (31)P PRE (center of the membrane), while residue 22 shows the largest (31)P PRE change (near the membrane surface), when compared to the diamagnetic control M2? sample. This PRE SS-NMR technique can be used as a molecular ruler to measure membrane immersion depth. PMID:24689497

Maltsev, Sergey; Hudson, Stephen M; Sahu, Indra D; Liu, Lishan; Lorigan, Gary A

2014-04-24

151

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

152

Resonator with reduced sample heating and increased homogeneity for solid-state NMR  

NASA Astrophysics Data System (ADS)

In the application of solid-state NMR to many systems, the presence of radiofrequency (rf) electric fields inside classical solenoidal coils causes heating of lossy samples. In particular, this is critical for proteins in ionic buffers. Rf sample heating increases proportional to frequency which may result in the need to reduce the rf pulse power to prevent partial or total sample deterioration. In the present paper, we propose a multifrequency-tunable NMR resonator where the sample is electrically shielded from the NMR coil by a conductive sheet that increases the magneto-electric ratio. Expressions for the B1 efficiency as function of magnetic and electric filling factors are derived that allow a direct comparison of different resonators. Rf efficiency, homogeneity, signal-to-noise, and rf sample heating are compared. NMR spectra at 700 MHz on ethylene glycol, glycine, and a model protein were acquired to compare the resonators under realistic experimental conditions.

Krahn, Alexander; Priller, Uwe; Emsley, Lyndon; Engelke, Frank

2008-03-01

153

Resonator with reduced sample heating and increased homogeneity for solid-state NMR.  

PubMed

In the application of solid-state NMR to many systems, the presence of radiofrequency (rf) electric fields inside classical solenoidal coils causes heating of lossy samples. In particular, this is critical for proteins in ionic buffers. Rf sample heating increases proportional to frequency which may result in the need to reduce the rf pulse power to prevent partial or total sample deterioration. In the present paper, we propose a multifrequency-tunable NMR resonator where the sample is electrically shielded from the NMR coil by a conductive sheet that increases the magneto-electric ratio. Expressions for the B1 efficiency as function of magnetic and electric filling factors are derived that allow a direct comparison of different resonators. Rf efficiency, homogeneity, signal-to-noise, and rf sample heating are compared. NMR spectra at 700MHz on ethylene glycol, glycine, and a model protein were acquired to compare the resonators under realistic experimental conditions. PMID:18187352

Krahn, Alexander; Priller, Uwe; Emsley, Lyndon; Engelke, Frank

2008-03-01

154

Membrane Protein Structural Validation by Oriented Sample Solid-State NMR: Diacylglycerol Kinase.  

PubMed

The validation of protein structures through functional assays has been the norm for many years. Functional assays perform this validation for water-soluble proteins very well, but they need to be performed in the same environment as that used for the structural analysis. This is difficult for membrane proteins that are often structurally characterized in detergent environments, although functional assays for these proteins are most frequently performed in lipid bilayers. Because the structure of membrane proteins is known to be sensitive to the membrane mimetic environment, such functional assays are appropriate for validating the protein construct, but not the membrane protein structure. Here, we compare oriented sample solid-state NMR spectral data of diacylglycerol kinase previously published with predictions of such data from recent structures of this protein. A solution NMR structure of diacylglycerol kinase has been obtained in detergent micelles and three crystal structures have been obtained in a monoolein cubic phase. All of the structures are trimeric with each monomer having three transmembrane and one amphipathic helices. However, the solution NMR structure shows typical perturbations induced by a micelle environment that is reflected in the predicted solid-state NMR resonances from the structural coordinates. The crystal structures show few such perturbations, especially for the wild-type structure and especially for the monomers that do not have significant crystal contacts. For these monomers the predicted and observed data are nearly identical. The thermostabilized constructs do show more perturbations, especially the A41C mutation that introduces a hydrophilic residue into what would be the middle of the lipid bilayer inducing additional hydrogen bonding between trimers. These results demonstrate a general technique for validating membrane protein structures with minimal data obtained from membrane proteins in liquid crystalline lipid bilayers by oriented sample solid-state NMR. PMID:24739155

Murray, Dylan T; Li, Conggang; Gao, F Philip; Qin, Huajun; Cross, Timothy A

2014-04-15

155

Automated robust and accurate assignment of protein resonances for solid state NMR.  

PubMed

The process of resonance assignment represents a time-consuming and potentially error-prone bottleneck in structural studies of proteins by solid-state NMR (ssNMR). Software for the automation of this process is therefore of high interest. Procedures developed through the last decades for solution-state NMR are not directly applicable for ssNMR due to the inherently lower data quality caused by lower sensitivity and broader lines, leading to overlap between peaks. Recently, the first efforts towards procedures specifically aimed for ssNMR have been realized (Schmidt et al. in J Biomol NMR 56(3):243-254, 2013). Here we present a robust automatic method, which can accurately assign protein resonances using peak lists from a small set of simple 2D and 3D ssNMR experiments, applicable in cases with low sensitivity. The method is demonstrated on three uniformly (13)C, (15)N labeled biomolecules with different challenges on the assignments. In particular, for the immunoglobulin binding domain B1 of streptococcal protein G automatic assignment shows 100 % accuracy for the backbone resonances and 91.8 % when including all side chain carbons. It is demonstrated, by using a procedure for generating artificial spectra with increasing line widths, that our method, GAMES_ASSIGN can handle a significant amount of overlapping peaks in the assignment. The impact of including different ssNMR experiments is evaluated as well. PMID:24817190

Nielsen, Jakob Toudahl; Kulminskaya, Natalia; Bjerring, Morten; Nielsen, Niels Chr

2014-06-01

156

Orientational and motional narrowing of solid-state NMR lineshapes of uniaxially aligned membrane proteins.  

PubMed

A unified theory for the NMR line shapes of aligned membrane proteins arising from uniaxial disorder (mosaic spread) and global rotational diffusion about the director axis is presented. A superoperator formalism allows one to take into account the effects of continuous radiofrequency irradiation and frequency offsets in the presence of dynamics. A general method based on the Stochastic Liouville Equation makes it possible to bridge the static and dynamic limits in a single model. Simulations of solid-state NMR spectra are performed for a uniform ? helix by considering orientational disorder and diffusion of the helix as a whole relative to the alignment axis. The motional narrowing of the resonance lines is highly inhomogeneous and can be used as an additional angular restraint in structure calculations. Experimental solid-state NMR spectra of Pf1 coat protein support the conclusions of the theory for two limiting cases. The static disorder dominates the (15)N NMR spectra of Pf1 aligned on a phage, while fast uniaxial diffusion provides a line narrowing mechanism for the Pf1 protein reconstituted in magnetically aligned bicelles. PMID:22073926

Nevzorov, Alexander A

2011-12-29

157

Characterization of Substituted Phenol-Formaldehyde Resins Using Solid-State Carbon-13 NMR (Nuclear Magnetic Resonance).  

National Technical Information Service (NTIS)

Crosslinked substituted phenol-formaldehyde resins were synthesized from cashew nut shell liquid, 3-n-pentadecylphenol and phenol with formaldehyde. The resulting resins were crosslinked and then investigated using carbon-13 NMR in the solid state using c...

B. R. Sinha D. O'Connor F. D. Blum

1988-01-01

158

Characterization of Substituted Phenol-Formaldehyde Resins Using Solid-State Carbon-13 NMR (Nuclear Magnetic Resonance).  

National Technical Information Service (NTIS)

Crosslinked substituted phenol formaldehyde resins were synthesized from cashew nut shell liquid, 3-n-pentadecylphenol and phenol with formaldehyde. The resulting resins were crosslinked and then investigated using carbon-13 NMR in the solid state using c...

B. R. Sinha D. O'Connor F. D. Blum

1989-01-01

159

Orientation of Amphipathic Helical Peptides in Membrane Bilayers Determined by Solid-State NMR Spectroscopy. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

Solid-state NMR spectroscopy was used to determine the orientations of two amphipathic helical peptides associated with lipid bilayers. A single spectral parameter provides sufficient orientational information for these peptides, which are known, from oth...

B. Bechinger Y. Kim L. E. Chirlian J. Gesell J. M. Neumann

1991-01-01

160

Investigating fatty acids inserted into magnetically aligned phospholipid bilayers using EPR and solid-state NMR spectroscopy  

NASA Astrophysics Data System (ADS)

This is the first time 2H solid-state NMR spectroscopy and spin-labeled EPR spectroscopy have been utilized to probe the structural orientation and dynamics of a stearic acid incorporated into magnetically aligned phospholipid bilayers or bicelles. The data gleaned from the two different techniques provide a more complete description of the bilayer membrane system. Both methods provided similar qualitative information on the phospholipid bilayer, high order, and low motion for the hydrocarbon segment close to the carboxyl groups of the stearic acid and less order and more rapid motion at the end towards the terminal methyl groups. However, the segmental order parameters differed markedly due to the different orientations that the nitroxide and C-D bond axes transform with the various stearic acid acyl chain conformations, and because of the difference in dynamic sensitivity between NMR and EPR over the timescales examined. 5-, 7-, 12-, and 16-doxylstearic acids spin-labels were used in the EPR experiments and stearic acid-d 35 was used in the solid-state NMR experiments. The influence of the addition of cholesterol and the variation of temperature on the fatty acid hydrocarbon chain ordering in the DMPC/DHPC phospholipid bilayers was also studied. Cholesterol increased the degree of ordering of the hydrocarbon chains. Conversely, as the temperature of the magnetically aligned phospholipid bilayers increased, the order parameters decreased due to the higher random motion of the acyl chain of the stearic acid. The results indicate that magnetically aligned phospholipid bilayers are an excellent model membrane system and can be used for both NMR and EPR studies.

Nusair, Nisreen A.; Tiburu, Elvis K.; Dave, Paresh C.; Lorigan, Gary A.

2004-06-01

161

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

SciTech Connect

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

Tang, Pei; Juang, Chilong; Harbison, G.S. (State Univ. of New York, Stony Brook (USA))

1990-07-06

162

Solid state structures of phenylpyruvates as studied by high resolution 13C NMR spectroscopy  

NASA Astrophysics Data System (ADS)

High resolution solid state 13C NMR measurements were made on phenylpyruvic acid and its sodium, lithium and calcium salts, using the total suppression of spinning side bands and the dipolar diphasing technique. The spectra of their 2- 13C enriched analogs were also recorded. The NMR data were discussed by reference to the solution spectra, and the following definitive evidence was obtained: the acid, the hydrated sodium and lithium salts and the dehydrated sodium salt take the enol, the diol and the keto form, respectively, but the hydrated calcium salt exists in the keto form. The 13C NMR signal of the gem-diol carbon was found to appear at 98 ppm. The calcium salt has two doublets at 166 and 134 ppm which originate from the carbons C(1) and C(4); this splitting suggests that the carboxylate group and/or the phenyl ring in the phenylpyruvate anion are oriented in two different ways.

Kuwae, Akio; Hanai, Kazuhiko; Oyama, Kaoru; Uchino, Masazumi; Lee, Ho-Hi

1993-01-01

163

Triple Resonance Solid State NMR Experiments with Reduced Dimensionality Evolution Periods  

NASA Astrophysics Data System (ADS)

Two solid state NMR triple resonance experiments which utilize the simultaneous incrementation of two chemical shift evolution periods to obtain a spectrum with reduced dimensionality are described. The CON CA experiment establishes the correlation of 13C i-1 to 13C? i and 15N i by simultaneously encoding the 13CO i-1 and 15N i chemical shifts. The CAN COCA experiment establishes the correlation 13Ca i and 15CO i to 13C? i-1 and 15N i-1 within a single experiment by simultaneous encoding of the 13C? i and 15N i chemical shifts. This experiment establishes sequential amino acid correlations in close analogy to the solution state HNCA experiment. Reduced dimensionality 2D experiments are a practical alternative to recording multiple 3D data sets for the purpose of obtaining sequence-specific resonance assignments of peptides and proteins in the solid state.

Astrof, Nathan S.; Lyon, Charles E.; Griffin, Robert G.

2001-10-01

164

Variable-temperature solid-state nuclear-magnetic-resonance probe for superconducting magnets operating in the range 3-350 K  

Microsoft Academic Search

A versatile, variable-temperature (3–350 K continuous), vacuum cold-finger, solid-state nuclear-magnetic-resonance (NMR) probe is described and its characteristics in several applications are discussed. The single-coil probe is specifically designed for use in superconducting magnets with bores as small as 2.5 in. and is suitable for both single- and double-resonance experiments. The tuning arrangement allows for multinuclear data acquisition without the necessity

Keith Carduner; Marco Villa; David White

1984-01-01

165

Sensitivity and resolution enhancement in solid-state NMR spectroscopy of bicelles  

NASA Astrophysics Data System (ADS)

Magnetically aligned bicelles are becoming attractive model membranes to investigate the structure, dynamics, geometry, and interaction of membrane-associated peptides and proteins using solution- and solid-state NMR experiments. Recent studies have shown that bicelles are more suitable than mechanically aligned bilayers for multidimensional solid-state NMR experiments. In this work, we describe experimental aspects of the natural abundance 13C and 14N NMR spectroscopy of DMPC/DHPC bicelles. In particular, approaches to enhance the sensitivity and resolution and to quantify radio-frequency heating effects are presented. Sensitivity of 13C detection using single pulse excitation, conventional cross-polarization (CP), ramp-CP, and NOE techniques are compared. Our results suggest that the proton decoupling efficiency of the FLOPSY pulse sequence is better than that of continuous wave decoupling, TPPM, SPINAL, and WALTZ sequences. A simple method of monitoring the water proton chemical shift is demonstrated for the measurement of sample temperature and calibration of the radio-frequency-induced heating in the sample. The possibility of using 14N experiments on bicelles is also discussed.

Dvinskikh, Sergey V.; Yamamoto, Kazutoshi; Dürr, Ulrich H. N.; Ramamoorthy, Ayyalusamy

2007-02-01

166

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

NASA Astrophysics Data System (ADS)

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

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

2006-04-01

167

Sensitivity and Resolution Enhancement in Solid-State NMR Spectroscopy of Bicelles  

PubMed Central

Magnetically aligned bicelles are becoming attractive model membranes to investigate the structure, dynamics, geometry, and interaction of membrane-associated peptides and proteins using solution- and solid-state NMR experiments. Recent studies have shown that bicelles are more suitable than mechanically aligned bilayers for multidimensional solid-state NMR experiments. In this work, we describe experimental aspects of the natural abundance 13C and 14N NMR spectroscopy of DMPC/DHPC bicelles. In particular, approaches to enhance the sensitivity and resolution and to quantify radio frequency heating effects are presented. Sensitivity of 13C detection using single pulse excitation, conventional cross-polarization (CP), ramp-CP, and NOE techniques are compared. Our results suggest that the proton decoupling efficiency of the FLOPSY pulse sequence is better than that of continuous wave decoupling, TPPM, SPINAL and WALTZ sequences. A simple method of monitoring the water proton chemical shift is demonstrated for the measurement of sample temperature and calibration of the radio-frequency-induced heating in the sample. The possibility of using 14N experiments on bicelles is also discussed.

Dvinskikh, Sergey V.; Yamamoto, Kazutoshi; Durr, Ulrich H. N.; Ramamoorthy, Ayyalusamy

2007-01-01

168

Experiments optimized for magic angle spinning and oriented sample solid-state NMR of proteins.  

PubMed

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

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

2013-10-17

169

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

170

Investigation of aggregated structures in organic light-emitting diodes: approach from solid-state NMR  

NASA Astrophysics Data System (ADS)

The conformations and aggregated structures, such as molecular orientations, of organic molecules in organic light-emitting diodes (OLEDs) are considered to be closely related to the performance of OLEDs. Therefore, their clarification is of great importance in understanding device performance; however, the structures have not been fully analyzed because the organic molecules in OLEDs are often in amorphous states, and conventional methods for structure analysis, such as diffraction methods, do not provide sufficient information. In this study, we have attempted the analysis of molecular orientations of OLED materials by solid-state NMR, which is useful for structure analysis even for amorphous solids.

Kaji, Hironori; Fukushima, Tatsuya; Fukuchi, Masashi; Komino, Takeshi; Adachi, Chihaya

2012-09-01

171

Indirectly detected heteronuclear correlation solid-state NMR spectroscopy of naturally abundant 15N nuclei.  

PubMed

Two-dimensional indirectly detected through-space and through-bond (1)H{(15)N} solid-state NMR experiments utilizing fast magic angle spinning (MAS) and homonuclear multipulse (1)H decoupling are evaluated. Remarkable efficiency of polarization transfer can be achieved at a MAS rate of 40 kHz by both cross-polarization and INEPT, which makes these methods applicable for routine characterizations of natural abundance solids. The first measurement of 2D (1)H{(15)N} HETCOR spectrum of natural abundance surface species is also reported. PMID:24287060

Althaus, Stacey M; Mao, Kanmi; Stringer, John A; Kobayashi, Takeshi; Pruski, Marek

2014-01-01

172

Two-dimensional correlation of solid state and liquid state NMR using a laser temperature jump  

NASA Astrophysics Data System (ADS)

Solid state nuclear magnetic resonance (NMR) spectra and the corresponding liquid state spectra have been interrelated through two-dimensional experiments with a fast temperature jump during the mixing time. This jump must, as a minimum requirement, be shorter than the relevant spin lattice relaxation times, and was implemented using a CO2 laser heater. As the first demonstration of this experiment we report a 2D H-1 solid-liquid spectrum of camphor. Suggested applications of future 2D temperature jump experiments include studies of reversible chemical reactions, reorientational dynamics, phase behavior, and magnetic and electrical properties.

Ferguson, David B.; Krawietz, Thomas R.; Haw, James F.

1994-10-01

173

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

Microsoft Academic Search

We demonstrate that short, medium and long-range constraints can be extracted from proton mediated, rare-spin detected correlation\\u000a solid-state NMR experiments for the microcrystalline 10.4 × 2 kDa dimeric model protein Crh. Magnetization build-up curves\\u000a from cross signals in NHHC and CHHC spectra deliver detailed information on side chain conformers and secondary structure\\u000a for interactions between spin pairs. A large number of medium and

Carole Gardiennet; Antoine Loquet; Manuel Etzkorn; Henrike Heise; Marc Baldus; Anja Böckmann

2008-01-01

174

Solid-state NMR characterization of the putative membrane anchor of TWD1 from Arabidopsis thaliana  

Microsoft Academic Search

Structure and membrane interaction of a 31 amino acid residue fragment of the membrane bound FKBP-like protein twisted dwarf\\u000a 1 (TWD1) from Arabidopsis thaliana was investigated by solid-state NMR spectroscopy. The studied peptide TWD1(335–365) contained the putative membrane anchor\\u000a of the protein (residues 339–357) that was previously predicted by sequence hydrophobicity analysis. The TWD1 peptide was\\u000a synthesized by standard solid

Holger A. Scheidt; Alexander Vogel; Andreas Eckhoff; Bernd W. Koenig; Daniel Huster

2007-01-01

175

Mechanisms of Peptide-Induced Pore Formation in Lipid Bilayers Investigated by Oriented 31P Solid-State NMR Spectroscopy  

PubMed Central

There is a considerable interest in understanding the function of antimicrobial peptides (AMPs), but the details of their mode of action is not fully understood. This motivates extensive efforts in determining structural and mechanistic parameters for AMP’s interaction with lipid membranes. In this study we show that oriented-sample 31P solid-state NMR spectroscopy can be used to probe the membrane perturbations and -disruption by AMPs. For two AMPs, alamethicin and novicidin, we observe that the majority of the lipids remain in a planar bilayer conformation but that a number of lipids are involved in the peptide anchoring. These lipids display reduced dynamics. Our study supports previous studies showing that alamethicin adopts a transmembrane arrangement without significant disturbance of the surrounding lipids, while novicidin forms toroidal pores at high concentrations leading to more extensive membrane disturbance.

Bertelsen, Kresten; Dorosz, Jerzy; Hansen, Sara Krogh; Nielsen, Niels Chr.; Vosegaard, Thomas

2012-01-01

176

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.

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

2009-01-01

177

Solid-state 51V NMR investigation of the intercalation of alkylamines into layered alpha-vanadyl phosphate.  

PubMed

The intercalation behavior of layered alpha-phase vanadyl phosphate, alpha-VOPO(4).2H(2)O (alpha-VP), with alkylamine was investigated by (51)V solid-state NMR in combination with powder XRD. The XRD results show that the amines form bimolecular layers upon intercalation. For the intercalation with short chain amines (propylamine, pentylamine, and hexylamine), the C-C chain of the amines is tilted with respect to the inorganic basal plane. The amines with a longer alkyl chain (dodecylamine and hexadecylamine) tend to adopt an orientation where the C-C chain direction is perpendicular to the VP layer. For the amine with eight carbon atoms (octylamine), the intercalation results in two coexisting phases with different chain orientations. (51)V solid-state NMR was used to directly probe the effect of intercalation on the metal center environments. Both (51)V magic-angle spinning and static spectra of alpha-VP intercalated with different amines were obtained at different magnetic fields, and they are sensitive to intercalation. The intercalation induces the (51)V isotropic chemical shift to move toward deshielded direction. (51)V chemical shielding parameters such as the span are sensitive to the orientation of the amine chain with respect to the VP basal plane. For the V centers interacting with the amines having a tilted orientation, the (51)V span gradually decreases with increasing alkyl chain length. However, the span of the (51)V atoms interacting with the amines perpendicular to the VP layer is larger and independent of the length of the alkyl chain. The (51)V NMR data indicate that for the alpha-VPs intercalated with long-chain amines, such as dodecylamine and hexadecylamine, the amines can assume both tilted and perpendicular orientations. PMID:20356027

Zhu, Jianfeng; Huang, Yining

2010-06-15

178

STRUCTURAL STUDIES OF BIOMATERIALS USING DOUBLE-QUANTUM SOLID-STATE NMR SPECTROSCOPY  

SciTech Connect

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-stateNMR(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, Gary P.; Long, J. R.; Karlsson, T.; Shaw, Wendy J.; Popham, Jennifer M.; Oyler, N.; Bower, Paula M.; Stringer, J.; Gregory, D.; Mehta, M.; Stayton, Patrick S.

2004-10-31

179

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

180

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

181

Natural abundance high-resolution solid state 2 H NMR spectroscopy  

NASA Astrophysics Data System (ADS)

We report for the first time an approach for natural abundance solid state 2H NMR spectroscopy involving magic angle sample spinning (MAS), high-power 1H decoupling (HPPD) and 1H- 2H cross polarization (CP). Taking tetrakis(trimethylsilyl)silane (TTMSS), adamantane, 1-chloroadamantane, hexamethylbenzene (HMB), 2,2-dimethyl-1,3-propanediol (DMPD) and 2-hydroxymethyl-2-methyl-1,3-propanediol (HMPD) as examples, it has been shown that the combination of HPPD and MAS can be applied readily to study rotator phase solids, allowing isotropic peaks arising from chemically inequivalent 2H nuclei to be resolved. For natural abundance samples of TTMSS and chloroadamantane, it has been shown that 2H CP/HPPD/MAS NMR experiments, involving polarization transfer from 1H to 2H, may provide considerable sensitivity enhancement in comparison with single pulse experiments.

Aliev, Abil E.; Harris, Kenneth D. M.; Apperley, David C.

1994-08-01

182

Natural abundance high-resolution solid state 2 H NMR spectroscopy  

NASA Astrophysics Data System (ADS)

We report for the first time an approach for natural abundance solid state 2 H NMR spectroscopy involving magic angle sample spinning (MAS), high-power 1 H decoupling (HPPD) and 1 H- 2 H cross polarization (CP). Taking tetrakis(trimethylsilyl)silane (TTMSS), adamantane, 1-chloroadamantane, hexamethylbenzene (HMB), 2,2-dimethyl-1,3-propanediol (DMPD) and 2-hydroxymethyl-2-methyl-1,3-propanediol (HMPD) as examples, it has been shown that the combination of HPPD and MAS can be applied readily to study rotator phase solids, allowing isotropic peaks arising from chemically inequivalent 2 H nuclei to be resolved. For natural abundance samples of TTMSS and chloroadamantane, it has been shown that 2 H CP/HPPD/MAS NMR experiments, involving polarization transfer from 1 H to 2 H, may provide considerable sensitivity enhancement in comparison with single pulse experiments.

Aliev, Abil E.; Harris, Kenneth D. M.; Apperley, David C.

1994-08-01

183

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

PubMed

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

Maly, Thorsten; Andreas, Loren B; Smith, Albert A; Griffin, Robert G

2010-06-14

184

Quantitative structural characterization of POSS and octavinyl-POSS nanocomposites by solid state NMR.  

PubMed

The ratio between two different (29)Si atoms in chloromethylphenyl isobutyl Polyhedral Oligomeric Silsesquioxane (POSS) was determined based on the quantitative cross polarization (QCP) (Shu et al., Chem. Phys. Lett. 462 (2008) 125) in solid-state NMR. For a (29)Si/(1)H spin system, cross polarization and depolarization together with the reciprocity relation were performed with optimized experimental conditions. It saves considerable experimental time compared to the (29)Si direct polarization experiment. The same method was further applied to octavinyl-POSS nanocomposites containing perfluoropolyether (PFPE) for deriving directly and accurately the average numbers of reacted vinyl groups, which may not be obtained by combining FTIR and solution (1)H NMR. In principle, the aforementioned method proves to be valuable in quantitative characterization of silicon related structures in bulk materials. PMID:22503875

Zhao, Huipeng; Shu, Jie; Chen, Qun; Zhang, Shanmin

2012-01-01

185

HCN polymers characterized by solid state NMR: Chains and sheets formed in the neat liquid  

PubMed Central

Hydrogen cyanide polymerizes readily under a variety of conditions and significant prebiotic roles have been suggested for these polymers due to the abundance of HCN in universe. However, the structures of HCN polymers have been more speculative than grounded in experimental data. Here we show that 13C and 15N solid state NMR spectra of polymers formed in neat HCN are inconsistent with the previously proposed structures and suggest instead that the polymers are formed by simple monomer addition, first in head-to-tail fashion to form linear, conjugated chains, and then laterally to form saturated two-dimensional networks. This interpretation of the NMR spectra finds support in other information about the polymerization of neat HCN, including the presence of free radicals. As expected from the literature, formation of the HCN tetramer, diaminomaleonitrile, is also observed, but only when the reaction is catalyzed exclusively by base and then in crystalline form.

Mamajanov, Irena; Herzfeld, Judith

2009-01-01

186

Chain Folding in Polymer Crystals Detected by Solid-state NMR  

NASA Astrophysics Data System (ADS)

Polymer crystallization induces transitions from random coils in the melt states to bilayer structures consisting of chain-folded crystals and disordered amorphous regions. Although the concept of chain folding is well recognized, there have been continuous debates about adjacent re-entry fractions of polymer chains crystallized at different physical conditions. To understand chain-folding structures in complex systems, spatial selectivity to access short-range polymer-polymer interactions is necessary. In this talk, we will propose a novel approach using solid-state NMR and selective isotope labeling for characterizing chain-folding of polymer chains. Spatial selectivity in double quantum NMR reveals adjacent re-entry fractions in the bulk crystals at different conditions.

Miyoshi, Toshikazu

2012-02-01

187

Solid state 13C NMR characterisation study on fourth generation Ziegler-Natta catalysts.  

PubMed

In this study, solid state (13)C NMR spectroscopy was utilised to characterize and identify the metal-ester coordination in active fourth generation (phthalate) Ziegler-Natta catalysts. It is known that different donors affect the active species in ZN catalysts. However, there is still limited data available of detailed molecular information how the donors and the active species are interplaying. One of the main goals of this work was to get better insight into the interactions of donor and active species. Based on the anisotropy tensor values (?(11), ?(22), ?(33)) from low magic-angle spinning (MAS) (13)C NMR spectra in combination with chemical shift anisotropy (CSA) calculations (?(aniso) and ?), both the coordinative metal (Mg/Ti) and the symmetry of this interaction between metal and the internal donor in the active catalyst (MgCl(2)/TiCl(4)/electron donor) system could be identified. PMID:22425229

Heikkinen, Harri; Liitiä, Tiina; Virkkunen, Ville; Leinonen, Timo; Helaja, Tuulamari; Denifl, Peter

2012-01-01

188

Probing access resistance of solid-state nanopores with a scanning-probe microscope tip.  

PubMed

An apparatus that integrates solid-state nanopore ionic current measurement with a scanning-probe microscope is developed. When a micrometer-scale scanning-probe tip is near a voltage-biased nanometer-scale pore (10–100 nm), the tip partially blocks the flow of ions to the pore and increases the pore access resistance. The apparatus records the current blockage caused by the probe tip and the location of the tip simultaneously. By measuring the current blockage map near a nanopore as a function of the tip position in 3D space in salt solution, the relative pore resistance increases due to the tip and ?R/R0 is estimated as a function of the tip location, nanopore geometry, and salt concentration. The amplitude of ?R/R0 also depends on the ratio of the pore length to its radius as Ohm's law predicts. When the tip is very close to the pore surface, ?10 nm, experiments show that ?R/R0 depends on salt concentration as predicted by the Poisson and Nernst–Planck equations. Furthermore, the measurements show that ?R/R0 goes to zero when the tip is about five times the pore diameter away from the center of the pore entrance. The results in this work not only demonstrate a way to probe the access resistance of nanopores experimentally; they also provide a way to locate the nanopore in salt solution, and open the door to future nanopore experiments for detecting single biomolecules attached to a probe tip. PMID:22287084

Hyun, Changbae; Rollings, Ryan; Li, Jiali

2012-02-01

189

Probing Access Resistance of Solid-state Nanopores with a Scanning Probe Microscope Tip.  

PubMed

An apparatus that integrates solid-state nanopore ionic current measurement with a Scanning Probe Microscope has been developed. When a micrometer-scale scanning probe tip is near a voltage biased nanometer-scale pore (10-100 nm), the tip partially blocks the flow of ions to the pore and increases the pore access resistance. The apparatus records the current blockage caused by the probe tip and the location of the tip simultaneously. By measuring the current blockage map near a nanopore as a function of the tip position in 3D space in salt solution, we estimate the relative pore resistance increase due to the tip, ?R/R(0), as a function of the tip location, nanopore geometry, and salt concentration. The amplitude of ?R/R(0) also depends on the ratio of the pore length to its radius as Ohm's law predicts. When the tip is very close to the pore surface, ~10 nm, our experiments show that ?R/R(0) depends on salt concentration as predicted by the Poisson and Nernst-Planck equations. Furthermore, our measurements show that ?R/R(0) goes to zero when the tip is about five times the pore diameter away from the center of the pore entrance. The results in this work not only demonstrate a way to probe the access resistance of nanopores experimentally, they also provide a way to locate the nanopore in salt solution, and open the door to future nanopore experiments for detecting single biomolecules attached to a probe tip. PMID:22393313

Hyun, Changbae; Rollings, Ryan; Li, Jiali

2012-02-01

190

Probing Access Resistance of Solid-state Nanopores with a Scanning Probe Microscope Tip  

PubMed Central

An apparatus that integrates solid-state nanopore ionic current measurement with a Scanning Probe Microscope has been developed. When a micrometer-scale scanning probe tip is near a voltage biased nanometer-scale pore (10–100 nm), the tip partially blocks the flow of ions to the pore and increases the pore access resistance. The apparatus records the current blockage caused by the probe tip and the location of the tip simultaneously. By measuring the current blockage map near a nanopore as a function of the tip position in 3D space in salt solution, we estimate the relative pore resistance increase due to the tip, ?R/R0, as a function of the tip location, nanopore geometry, and salt concentration. The amplitude of ?R/R0 also depends on the ratio of the pore length to its radius as Ohm’s law predicts. When the tip is very close to the pore surface, ~10 nm, our experiments show that ?R/R0 depends on salt concentration as predicted by the Poisson and Nernst-Planck equations. Furthermore, our measurements show that ?R/R0 goes to zero when the tip is about five times the pore diameter away from the center of the pore entrance. The results in this work not only demonstrate a way to probe the access resistance of nanopores experimentally, they also provide a way to locate the nanopore in salt solution, and open the door to future nanopore experiments for detecting single biomolecules attached to a probe tip.

Hyun, Changbae; Rollings, Ryan

2012-01-01

191

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

NASA Astrophysics Data System (ADS)

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

Baldock, J. A.; Sanderman, J.

2011-12-01

192

Dynamic nuclear polarization-enhanced solid-state NMR spectroscopy of GNNQQNY nanocrystals and amyloid fibrils.  

PubMed

Dynamic nuclear polarization (DNP) utilizes the inherently larger polarization of electrons to enhance the sensitivity of conventional solid-state NMR experiments at low temperature. Recent advances in instrumentation development and sample preparation have transformed this field and have opened up new opportunities for its application to biological systems. Here, we present DNP-enhanced (13)C-(13)C and (15)N-(13)C correlation experiments on GNNQQNY nanocrystals and amyloid fibrils acquired at 9.4 T and 100 K and demonstrate that DNP can be used to obtain assignments and site-specific structural information very efficiently. We investigate the influence of temperature on the resolution, molecular conformation, structural integrity and dynamics in these two systems. In addition, we assess the low-temperature performance of two commonly used solid-state NMR experiments, proton-driven spin diffusion (PDSD) and transferred echo double resonance (TEDOR), and discuss their potential as tools for measurement of structurally relevant distances at low temperature in combination with DNP. PMID:20454733

Debelouchina, Galia T; Bayro, Marvin J; van der Wel, Patrick C A; Caporini, Marc A; Barnes, Alexander B; Rosay, Melanie; Maas, Werner E; Griffin, Robert G

2010-06-14

193

3-Methylglutaric acid as a 13C solid-state NMR standard.  

PubMed

The calibration of a solid-state NMR spectrometer requires setting the magic angle, setting the reference and decoupler frequencies, ensuring that the magnetic field is homogeneous across the sample volume, optimizing the signal-to-noise ratio, determining the pi/2 pulse durations, and optimizing the Hartman-Hahn matching condition. Each task has one or more widely accepted standards, such as potassium bromide for setting the magic angle, adamantane for optimizing magnet homogeneity, and hexamethylbenzene or glycine for measuring the signal-to-noise ratio. We show that all of these tasks can be performed using 3-methylglutaric acid (MGA). In the case of high-powered decoupling, the CH(2) and CH carbon peaks of MGA provide an opportunity to evaluate the decoupling in a manner that is superior to any of the commonly used standard compounds. Thus, MGA can be used as a single solid-state NMR standard compound to perform all calibration steps except for magnet shimming. PMID:16887343

Barich, Dewey H; Gorman, Eric M; Zell, Mark T; Munson, Eric J

2006-10-01

194

Broadband Heteronuclear Solid-State NMR Experiments by Exponentially Modulated Dipolar Recoupling without Decoupling  

PubMed Central

We present a novel solid-state NMR method for heteronuclear dipolar recoupling without decoupling. The method, which introduces the concept of exponentially modulated rf fields, provides efficient broadband recoupling with large flexibility with respect to hetero- or homonuclear applications, sample spinning frequency, and operation without the need for high-power 1H decoupling. For previous methods, the latter has been a severe source of sample heating which may cause detoriation of costly samples. The so-called EXPonentially mOdulated Recoupling Technique (EXPORT) is described analytically and numerically, and demonstrated experimentally by 1D 13C spectra and 2D 13C-15N correlation spectra of 13C,15N-labeled samples of GB1, ubiquitin, and fibrils of the SNNFGAILSS fragment of amylin. Through its flexible operation, robustness, and strong performance, it is anticipated that EXPORT will find immediate application for both hetero- and homonuclear dipolar recoupling in solid-state NMR of 13C,15N-labeled proteins and compounds of relevance in chemistry.

Nielsen, Anders B.; Straas?, Lasse A.; Nieuwkoop, Andrew J.; Rienstra, Chad M.; Bjerring, Morten; Nielsen, Niels Chr.

2010-01-01

195

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

NASA Astrophysics Data System (ADS)

The acquisition and different appearances observed for wide bandwidth solid-state MAS NMR spectra of low-? nuclei, using 14N as an illustrative nucleus and employing two different commercial spectrometers (Varian, 14.1 T and Bruker, 19.6 T), 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 14.1 T) in several exploratory wide bandwidth 14N MAS NMR studies of inorganic nitrates and amino acids. These spectra have now been compared/evaluated with fully analyzed 14N MAS spectra correspondingly acquired at 19.6 T 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.

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

2011-08-01

196

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

Kameda, Tsunenori

2004-01-01

197

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

PubMed

A simple new method is presented that yields quantitative solid-state magic-angle spinning (MAS) (13)C NMR spectra of organic materials with good signal-to-noise ratios. It achieves long (>10ms) cross polarization (CP) from (1)H 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 (1)H 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 (1)H 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 (13)C 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. PMID:24374751

Johnson, Robert L; Schmidt-Rohr, Klaus

2014-02-01

198

Molecular-level characterization of probucol nanocrystal in water by in situ solid-state NMR spectroscopy.  

PubMed

The molecular state of colloidal probucol nanoparticles with additives was evaluated by (13)C in situ solid-state NMR spectroscopy. The nanoparticles were obtained by dispersing a ternary co-ground mixture of probucol/polyvinylpyrrolidon (PVP)/sodium dodecyl sulfate (SDS) in water. Their mean particle size was found to be approximately 150 nm by dynamic light scattering and cryogenic-scanning electron microscopy measurements. The results of the (13)C in situ solid-state NMR spectroscopy showed that probucol existed in the crystalline state (form I) in water. (13)C liquid-state NMR results indicated that PVP and SDS interacted with probucol in water. Their broad signals suggested that the surface interaction of the probucol nanocrystal with PVP and SDS stabilized the suspension. In addition, a freeze-dried sample of the suspension was studied by (13)C solid-state NMR and powder X-ray diffraction experiments, which confirmed the presence of the probucol nanocrystals. The combination of the in situ solid-state, solid-state, and liquid-state NMR measurement results provided molecular-level insights about the role of intermolecular interactions in the design of nanoformulations. PMID:22138607

Zhang, Junying; Higashi, Kenjirou; Limwikrant, Waree; Moribe, Kunikazu; Yamamoto, Keiji

2012-02-28

199

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

200

Solid-state NMR spectroscopic study of phosphate sorption mechanisms on aluminum (Hydr)oxides.  

PubMed

Sorption reactions occurring at mineral/water interfaces are of fundamental importance in controlling the sequestration and bioavailability of nutrients and pollutants in aqueous environments. To advance the understanding of sorption reactions, development of new methodology is required. In this study, we applied novel (31)P solid-state nuclear magnetic resonance (NMR) spectroscopy to investigate the mechanism of phosphate sorption on aluminum hydroxides under different environmental conditions, including pH (4-10), concentration (0.1-10 mM), ionic strength (0.001-0.5 M), and reaction time (15 min-22 days). Under these conditions, the NMR results suggest formation of bidentate binuclear inner-sphere surface complexes was the dominant mechanism. However, it was found that surface wetting caused a small difference. A small amount (<3%) of monodentate mononuclear inner-sphere surface complexes was observed in addition to the majority of bidentate binuclear surface complexes on a wet paste sample prepared at pH 5, which was analyzed in situ by a double-resonance NMR technique, namely, (31)P{(27)Al} rotational echo adiabatic passage double resonance (REAPDOR). Additionally, we found that adsorbents can substantially impact phosphate sorption not only on the macroscopic sorption capacity but also on their (31)P NMR spectra. Very similar NMR peaks were observed for phosphate sorbed to gibbsite and bayerite, whereas the spectra for phosphate adsorbed to boehmite, corundum, and ?-alumina were significantly different. All of these measurements reveal that NMR spectroscopy is a useful analytical tool for studying phosphorus chemistry at environmental interfaces. PMID:23837616

Li, Wei; Feng, Xionghan; Yan, Yupeng; Sparks, Donald L; Phillips, Brian L

2013-08-01

201

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

202

Structure and Ionic Interactions of Organic–Inorganic Composite Polymer Electrolytes Studied by Solid-State NMR and Raman Spectroscopy  

Microsoft Academic Search

Solid-state NMR studies of composite polymer electrolytes are reported. The materials consist of polyethylene oxide and an organic–inorganic composite, together with a lithium salt, and are candidates for electrolytes in solid-state lithium ion batteries. Silicon and aluminum MAS and multiple quantum MAS are used to characterize the network character of the organic–inorganic composite, and spin diffusion measurements are used to

Chan Gyu Joo; Lyudmila M Bronstein; Robert L Karlinsey; Josef W Zwanziger

2002-01-01

203

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

204

The rehydration of metakaolinite to kaolinite: Evidence from solid-state NMR and cognate techniques  

NASA Astrophysics Data System (ADS)

We have studied the process of rehydroxylation of metakaolinite to kaolinite by 27Al and 29Si MAS NMR in tandem with Fourier transform infrared spectroscopy, powder X-ray diffraction, thermogravimetric analysis, specific surface area measurement, atomic absorption spectrophotometry, and electron microscopy. The efficiency of the process strongly depends on temperature. The reaction is initiated at the edges of metakaolinite particles and is followed by diffusion of the water into their bulk. Regions of the metakaolinite structure, which locally retain the symmetry of kaolinite, act as nuclei for the reconstitution of kaolinite particles. The latter grow perpendicular to the c? axis and their edges are parallel to those of metakaolinite, showing that rehydroxylation is a topotactic solid-state process. 27Al and 29Si MAS NMR reveal that metakaolinite is an ill-defined mixture of amorphous silica and alumina, and can be transformed into kaolinite by a correct choice of experimental conditions. NMR also shows that: (i) the 5-coordinated Al occupancy decreases with the reaction time faster than that of 4-coordinated Al, which supports the view that 5-coordinated Al in metakaolinite acts as a structural defect; and (ii) the 001 and 002 XRD reflections of kaolinite are only observed when the 5-coordinated 27Al signal is faint. Further studies on the synthesis of kaolin (and indeed other clay minerals) are needed to assess the role of 5-coordinated Al in the process.

Rocha, João; Adams, John M.; Klinowski, Jacek

1990-12-01

205

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

SciTech Connect

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

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

2011-02-17

206

Three Structural Roles for Water in Bone Observed by Solid-State NMR  

PubMed Central

Hydrogen-bearing species in the bone mineral environment were investigated using solid-state NMR spectroscopy of powdered bone, deproteinated bone, and B-type carbonated apatite. Using magic-angle spinning and cross-polarization techniques three types of structurally-bound water were observed in these materials. Two of these water types occupy vacancies within the apatitic mineral crystal in synthetic carbonated apatite and deproteinated bone and serve to stabilize these defect-containing crystals. The third water was observed at the mineral surface in unmodified bone but not in deproteinated bone, suggesting a role for this water in mediating mineral-organic matrix interactions. Direct evidence of monohydrogen phosphate in a 1H NMR spectrum of unmodified bone is presented for the first time. We obtained clear evidence for the presence of hydroxide ion in deproteinated bone by 1H MAS NMR. A 1H-31P heteronuclear correlation experiment provided unambiguous evidence for hydroxide ion in unmodified bone as well. Hydroxide ion in both unmodified and deproteinated bone mineral was found to participate in hydrogen bonding with neighboring water molecules and ions. In unmodified bone mineral hydroxide ion was found, through a 1H-31P heteronuclear correlation experiment, to be confined to a small portion of the mineral crystal, probably the internal portion.

Wilson, Erin E.; Awonusi, Ayorinde; Morris, Michael D.; Kohn, David H.; Tecklenburg, Mary M. J.; Beck, Larry W.

2006-01-01

207

Solid-state NMR characterisation of the thermal transformation of a Hungarian white illite.  

PubMed

(1)H, (27)Al, (29)Si and (39)K solid-state NMR are reported from a Hungarian illite 2:1 clay for samples heated up 1600 degrees C. This single-phase sample has a small amount of aluminium substitution in the silica layer and very low iron-content ( approximately 0.4wt%). Thermal analysis shows several events that can be related to features in the NMR spectra, and hence changes in the atomic scale structure. As dehydroxylation occurs there is increasing AlO(4) and AlO(5)-contents. The silica and gibbsite layers become increasingly separated as the dehydroxylation progresses. Between 900 and 1000 degrees C the silica layer forms a potassium aluminosilicate glass. The gibbsite-layer forms spinel/gamma-Al(2)O(3) and some aluminium-rich mullite. Then on heating to 1600 degrees C changes in the (29)Si and (27)Al MAS NMR spectra are consistent with the aluminosilicate glass increasing its aluminium-content, the amount of mullite increasing probably with its silicon-content also increasing, and some alpha-Al(2)O(3) forming. PMID:15899582

Carroll, D L; Kemp, T F; Bastow, T J; Smith, M E

2005-07-01

208

Solid state NMR study of sodium thiocyanate/poly(ethylene oxide) electrolytes.  

PubMed

1H-, 13C-, 23Na-solid state NMR measurements have been used to characterise the morphology and the dynamics of several NaSCN-PEO mixtures. Selective 13C-MAS experiments allowed to determine the composition of the (PEO)nNaSCN samples in terms of the different phases present, as well as the real stoichiometry of the crystalline complex. 1H- and 13C-spin-lattice relaxation times provided estimates of the dimensions of the different domains and gave information on the dynamics of the polymer chains. 23Na-MAS spectra and 2D nutation experiments allowed to individuate the presence of different environments for the sodium cations on the basis of their quadrupolar interactions. PMID:9373903

Bartolotta, A; Forte, C; Geppi, M; Minniti, D; Visalli, G

1997-08-01

209

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

NASA Astrophysics Data System (ADS)

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

Wolniak, Micha?; Tomczyk, Micha?; Gudej, Jan; Wawer, Iwona

2006-12-01

210

Solid-State NMR Characterization of Autofluorescent Fibrils Formed by the Elastin-Derived Peptide GVGVAGVG  

PubMed Central

The characterization of the molecular structure and physical properties of self-assembling peptides is an important aspect of optimizing their utility as scaffolds for biomaterials and other applications. Here we report the formation of autofluorescent fibrils by an octapeptide (GVGVAGVG) derived via a single amino acid substitution in one of the hydrophobic repeat elements of human elastin. This is the shortest and most well-defined peptide so far reported to exhibit intrinsic fluorescence in the absence of a discrete fluorophore. Structural characterization by FTIR and solid-state NMR reveals a predominantly ?-sheet conformation for the peptide in the fibrils, which are likely assembled in an amyloid-like cross-? structure. Investigation of dynamics and the effects of hydration on the peptide are consistent with a rigid, water excluded structure, which has implications for the likely mechanism of intrinsic fibril fluorescence.

2011-01-01

211

Solid-state NMR spectroscopy provides atomic-level insights into the dehydration of cartilage.  

PubMed

An atomic-level insight into the functioning of articular cartilage would be useful to develop prevention strategies and therapies for joint diseases such as osteoarthritis. However, the composition and structure of cartilage and their relationship to its unique mechanical properties are quite complex and pose tremendous challenges to most biophysical techniques. In this study, we present an investigation of the structure and dynamics of polymeric molecules of articular cartilage using time-resolved solid-state NMR spectroscopy during dehydration. Full-thickness cartilage explants were used in magic-angle spinning experiments to monitor the structural changes of rigid and mobile carbons. Our results reveal that the dehydration reduced the mobility of collagen amino acid residues and carbon sugar ring structures in glycosaminoglycans but had no effect on the trans-Xaa-Pro conformation. Equally interestingly, our results demonstrate that the dehydration effects are reversible, and the molecular structure and mobility are restored upon rehydration. PMID:21786810

Xu, Jiadi; Zhu, Peizhi; Morris, Michael D; Ramamoorthy, Ayyalusamy

2011-08-25

212

Solid-State NMR Spectroscopy Provides Atomic-level Insights Into the Dehydration of Cartilage  

PubMed Central

An atomic-level insight into the functioning of articular cartilage would be useful to develop prevention strategies and therapies for joint diseases such as osteoarthritis. However, the composition and structure of cartilage, and their relationship to its unique mechanical properties are quite complex and pose tremendous challenges to most biophysical techniques. In this study, we present an investigation of the structure and dynamics of polymeric molecules of articular cartilage using time-resolved solid-state NMR spectroscopy during dehydration. Full-thickness cartilage explants were used in magic-angle spinning experiments to monitor the structural changes of rigid and mobile carbons. Our results reveal that the dehydration reduced the mobility of collagen amino acid residues and carbon sugar ring structures in glycosaminoglycans but had no effect on the trans-Xaa-Pro conformation. Equally interestingly, our results demonstrate that the dehydration effects are reversible, and the molecular structure and mobility are restored upon rehydration.

Xu, Jiadi; Zhu, Peizhi; Morris, Michael D.; Ramamoorthy, Ayyalusamy

2011-01-01

213

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.

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

2012-01-01

214

A comparison of NCO and NCA transfer methods for biological solid-state NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Three different techniques (adiabatic passage Hartman-Hahn cross-polarization, optimal control designed pulses, and EXPORT) are compared for transferring 15N magnetization to 13C in solid-state NMR experiments under magic-angle-spinning conditions. We demonstrate that, in comparison to adiabatic passage Hartman-Hahn cross-polarization, optimal control transfer pulses achieve similar or better transfer efficiencies for uniformly- 13C, 15N labeled samples and are generally superior for samples with non-uniform labeling schemes (such as 1,3- and 2- 13C glycerol labeling). In addition, the optimal control pulses typically use substantially lower average RF field strengths and are more robust with respect to experimental variation and RF inhomogeneity. Consequently, they are better suited for demanding samples.

Loening, Nikolaus M.; Bjerring, Morten; Nielsen, Niels Chr.; Oschkinat, Hartmut

2012-01-01

215

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

216

Natural-Abundance 43Ca Solid-State NMR Spectroscopy of Bone  

PubMed Central

Structural information about the coordination environment of calcium present in bone is highly valuable in understanding the role of calcium in bone formation, biomineralization, and bone diseases like osteoporosis. While a high-resolution structural study on bone has been considered to be extremely challenging, NMR studies on model compounds and bone minerals have provided valuable insights into the structure of bone. Particularly, the recent demonstration of 43Ca solid-state NMR experiments on model compounds is an important advance in this field. However, application of 43Ca NMR is hampered due to the low natural-abundance and poor sensitivity of 43Ca. In this study, we report the first demonstration of natural-abundance 43Ca magic angle spinning (MAS) NMR experiments on bone, using powdered bovine cortical bone samples. 43Ca NMR spectra of bovine cortical bone are analyzed by comparing to the natural-abundance 43Ca NMR spectra of model compounds including hydroxyapatite and carbonated apatite. While 43Ca NMR spectra of hydroxyapatite and carbonated apatite are very similar, they significantly differ from that of cortical bone. Raman spectroscopy shows that the calcium environment in bone is more similar to carbonated apatite than hydroxyapatite. A close analysis of 43Ca NMR spectra reveals that the chemical shift frequencies of cortical bone and 10% carbonated apatite are similar but the quadrupole coupling constant of cortical bone is larger than that measured for model compounds. In addition, our results suggest that an increase in the carbonate concentration decreases the observed 43Ca chemical shift frequency. A comparison of experimentally obtained 43Ca MAS spectra with simulations reveal a 3:4 mole ratio of Ca-I:Ca-II sites in carbonated apatite and a 2.3:3 mole ratio for hydroxyapatite. 2D triple-quantum 43Ca MAS experiments performed on a mixture of carbonated apatite and the bone protein osteocalcin reveal the presence of protein-bound and free calcium sites, which is in agreement with a model developed from X-ray crystal structure of the protein.

Xu, Jiadi; Zhu, Peizhi; Gan, Zhehong; Sahar, Nadder; Tecklenburg, Mary; Morris, Michael D.; Kohn, David H.; Ramamoorthy, Ayyalusamy

2010-01-01

217

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

SciTech Connect

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

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

2006-01-19

218

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

SciTech Connect

This thesis describes application and development of advanced solid-state nuclear magnetic resonance techniques for complex materials, in particular organic-inorganic nanocomposites and thermoelectric tellurides. The apatite-collagen interface, essential for understanding the biomineralization process in bone and engineering the interface for controlled bio-mimetic synthesis and optimized mechanical properties, is buried within the nanocomposite of bone. We used multinuclear solid-state NMR to study the composition and structure of the interface. Citrate has been identified as the main organic molecule strongly bound to the apatite surface with a density of 1/(2 nm){sup 2}, covering 1/6 of the total surface area in bovine bone. Citrate provides more carboxylate groups, one of the key functional groups found to affect apatite nucleation and growth, than all the non-collagenous proteins all together in bone; thus we propose that citrate stabilizes apatite crystals at a very small thickness of {approx}3 nm (4 unit cells) to increase bone fracture tolerance. The hypothesis has been confirmed in vitro by adding citrate in the bio-mimetic synthesis of polymerhydroxyapatite nanocomposites. The results have shown that the size of hydroxyapatite nanocrystals decreases as increasing citrate concentration. With citrate concentrations comparable to that in body fluids, similar-sized nanocrystals as in bone have been produced. Besides the dimensions of the apatite crystals, the composition of bone also affects its biofunctional and macroscopic mechanical properties; therefore, our team also extended its effort to enhance the inorganic portion in our bio-mimetic synthesis from originally 15 wt% to current 50 wt% compared to 65 wt% in bovine bone, by using Lysine-Leucine hydroxyapatite nucleating diblock co-polypeptide, which forms a gel at very low concentration. In this thesis, various advanced solid state NMR techniques have been employed to characterize nanocomposites. Meanwhile, we have developed new methods to achieve broadband high resolution NMR and improve the accuracy of inter-nuclear distance measurements involving quadrupolar spins. Broadband high resolution NMR of spin-1/2 nuclei has been accomplished by the adaptation of the magic angle turning (MAT) method to fast magic angle spinning, termed fast MAT, by solving technical problems such as off resonance effects. Fast MAT separates chemical shift anisotropy and isotropic chemical shifts over a spectral range of {approx}1.8 {gamma}B{sub 1} without significant distortions. Fast MAT {sup 125}Te NMR has been applied to study technologically important telluride materials with spectra spreading up to 190 kHz. The signal-to-noise ratio of the spectra is significantly improved by using echo-matched Gaussian filtering in offline data processing. The accuracy of the measured distances between spin-1/2 and quadrupolar nuclei with methods such as SPIDER and REAPDOR has been improved by compensating for the fast longitudinal quadrupolar relaxation on the sub-millisecond with a modified S{sub 0} pulse sequence. Also, the T1Q effect on the spin coherence and its spinning speed dependency has been explored and documented with analytical and numerical simulations as well as experimental measurements.

Hu, Yanyan

2011-02-07

219

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

220

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

221

Analysis of amorphous solid dispersions using 2D solid-state NMR and (1)H T(1) relaxation measurements.  

PubMed

Solid-state NMR (SSNMR) can provide detailed structural information about amorphous solid dispersions of pharmaceutical small molecules. In this study, the ability of SSNMR experiments based on dipolar correlation, spin diffusion, and relaxation measurements to characterize the structure of solid dispersions is explored. Observation of spin diffusion effects using the 2D (1)H-(13)C cross-polarization heteronuclear correlation (CP-HETCOR) experiment is shown to be a useful probe of association between the amorphous drug and polymer that is capable of directly proving glass solution formation. Dispersions of acetaminophen and indomethacin in different polymers are examined using this approach, as well as (1)H double-quantum correlation experiments to probe additional structural features. (1)H-(19)F CP-HETCOR serves a similar role for fluorinated drug molecules such as diflunisal in dispersions, providing a rapid means to prove the formation of a glass solution. Phase separation is detected using (13)C, (19)F, and (23)Na-detected (1)H T(1) experiments in crystalline and amorphous solid dispersions that contain small domains. (1)H T(1) measurements of amorphous nanosuspensions of trehalose and dextran illustrate the ability of SSNMR to detect domain size effects in dispersions that are not glass solutions via spin diffusion effects. Two previously unreported amorphous solid dispersions involving up to three components and containing voriconazole and telithromycin are analyzed using these experiments to demonstrate the general applicability of the approach. PMID:20681586

Pham, Tran N; Watson, Simon A; Edwards, Andrew J; Chavda, Manisha; Clawson, Jacalyn S; Strohmeier, Mark; Vogt, Frederick G

2010-10-01

222

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

SciTech Connect

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

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

2012-03-21

223

Trading sensitivity for information: Carr-Purcell-Meiboom-Gill acquisition in solid-state NMR  

NASA Astrophysics Data System (ADS)

The Carr-Purcell-Meiboom-Gill (CPMG) experiment has gained popularity in solid-state NMR as a method for enhancing sensitivity for anisotropically broadened spectra of both spin 1/2 and half integer quadrupolar nuclei. Most commonly, the train of CPMG echoes is Fourier transformed directly, which causes the NMR powder pattern to break up into a series of sidebands, sometimes called ``spikelets.'' Larger sensitivity enhancements are observed as the delay between the ? pulses is shortened. As the duration between the ? pulses is shortened, however, the echoes become truncated and information about the nuclear spin interactions is lost. We explored the relationship between enhanced sensitivity and loss of information as a function of the product ? 2?, where ? is the span of the anisotropic lineshape and 2? is the ? pulse spacing. For a lineshape dominated by the nuclear shielding anisotropy, we found that the minimum uncertainty in the tensor values is obtained using ? 2? values in the range ? 2?~12-1+6 and ? 2?~9-3+3 for ?s=0 and ?s=1, respectively. For an anisotropic second-order quadrupolar central transition lineshape under magic-angle spinning (MAS), the optimum range of ? 2?~9-2+3 was found. Additionally, we show how the Two-dimensional One Pulse (TOP) like processing approach can be used to eliminate the cumbersome sideband pattern lineshape and recover a more familiar lineshape that is easily analyzed with conventional lineshape simulation algorithms.

Dey, Krishna K.; Ash, Jason T.; Trease, Nicole M.; Grandinetti, Philip J.

2010-08-01

224

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

225

Solid-State NMR Evidence for ?-Hairpin Structure within MAX8 Designer Peptide Nanofibers  

PubMed Central

MAX8, a designer peptide known to undergo self-assembly following changes in temperature, pH, and ionic strength, has demonstrated usefulness for tissue engineering and drug delivery. It is hypothesized that the self-assembled MAX8 nanofiber structure consists of closed ?-hairpins aligned into antiparallel ?-sheets. Here, we report evidence from solid-state NMR spectroscopy that supports the presence of the hypothesized ?-hairpin conformation within the nanofiber structure. Specifically, our 13C-13C two-dimensional exchange data indicate spatial proximity between V3 and K17, and 13C-13C dipolar coupling measurements reveal proximity between the V3 and V18 backbone carbonyls. Moreover, isotopic dilution of labeled MAX8 nanofibers did not result in a loss of the 13C-13C dipolar couplings, showing that these couplings are primarily intramolecular. NMR spectra also indicate the existence of a minor conformation, which is discussed in terms of previously hypothesized nanofiber physical cross-linking and possible nanofiber polymorphism.

Leonard, Sarah R.; Cormier, Ashley R.; Pang, Xiaodong; Zimmerman, Maxwell I.; Zhou, Huan-Xiang; Paravastu, Anant K.

2013-01-01

226

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

PubMed

Solid-state proton nuclear magnetic resonance (NMR) measurements are performed successfully on polymer blend thin films through the use of synthetic mica as a substrate. When used as a substrate, synthetic fluorophlogopite mica with its proton-free, diamagnetic character, allows for adequate measurement sensitivity while minimally perturbing the proton thin-film spectra, especially relative to more commonly available natural micas. Specifically, we use multiple-pulse techniques in the presence of magic-angle spinning to measure the degree of mixing in two different polymer blend thin films, polystyrene/poly(xylylene ether) and poly(1-methyladamantyl methacrylate) (PMAdMA)/triphenylsulfonium perfluorobutanesulfonate (TPS-PFBS), spin-coated onto mica substrates. Our earlier studies had focused on bulk systems where NMR signals are stronger, but may not be representative of thin films of the same systems that are relevant to many applications such as photoresist formulations in the electronics industry. The superiority of synthetic over natural paramagnetic mica is demonstrated by the maintenance of resolution and spinning sideband intensities (relative to bulk samples) for the synthetic mica samples. In contrast, degraded resolution and large spinning sidebands are shown to typify spectra of the natural mica samples. This approach can be applied to many other proton measurements of solid thin films, thereby greatly extending the types of systems to be investigated. Magnetic susceptibility measurements are also reported for all micas used. PMID:19751986

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

2009-11-01

227

X-ray diffraction and solid-state NMR studies of a germanium binuclear complex.  

PubMed

A compound formulated as (C4H12N2)[Ge2(pmida)2(OH)2] x 4 H2O (where pmida(4-) = N-(phosphonomethyl)iminodiacetate and C4H12N2(2+) = piperazinedium cation), containing the anionic [Ge2(pmida)2(OH)2]2- complex, has been synthesised by the hydrothermal approach and its structure determined by single-crystal X-ray diffraction analysis. Several high-resolution solid-state magic-angle spinning (MAS) NMR techniques, in particular two-dimensional 1H-X(13C,31P) heteronuclear correlation (HETCOR) and 1H-1H homonuclear correlation (HOMCOR) experiments incorporating a frequency-switched Lee-Goldburg (FS-LG) decoupling scheme, have been employed for the first time in such a material. Using these tools in tandem affords an excellent general approach to study the structure of other inorganic-organic hybrids. We assigned the NMR resonances with the help of C...H and P...H internuclear distances obtained through systematic statistical analyses of the crystallographic data. The compound was further characterised by powder X-ray diffraction techniques, IR and Raman spectroscopy, and by elemental and thermal analyses (thermogravimetric analysis and differential scanning calorimetry). PMID:16189839

Mafra, Luís; Paz, Filipe A Almeida; Shi, Fa-Nian; Rocha, João; Trindade, Tito; Fernandez, Christian; Makal, Anna; Wozniak, Krzysztof; Klinowski, Jacek

2005-12-23

228

Solid state 13C and 2H NMR investigations of paramagnetic [Ni(II)(acac)2L2] complexes.  

PubMed

Nine structurally related paramagnetic acetylacetonato nickel(II) complexes: [Ni(acac)2] and trans-[Ni(acac)2(X)2]nH/D2O, X = H2O, D2O, NH3, MeOH, PMePh2, PMe2Ph, or [dppe]1/2, n = 0 or 1, dppe = 1,2-bis(diphenylphosphino)ethane, as well as cis-[Ni(F6-acac)2(D2O)2], F6-acac = hexafluoroacetylonato, have been characterized by solid state (13)C MAS NMR spectroscopy. (2)H MAS NMR was used to probe the local hydrogen bonding network in [Ni(acac)2(D2O)2]D2O and cis-[Ni(F6-acac)2(D2O)2]. The complexes serve to benchmark the paramagnetic shift, which can be associated with the resonances of atoms of the coordinated ligands. The methine (CH) and methyl (CH3) have characteristic combinations of the isotropic shift (?) and anisotropy parameters (d, ?). The size of the anisotropy (d), which is the sum of the chemical shift anisotropy (CSA) and the paramagnetic electron-nuclei dipolar coupling, is much more descriptive than the isotropic shift. Moreover, the CSA is found to constitute up to one-third of the total anisotropy and should be taken into consideration when (13)C anisotropies are used for structure determination of paramagnetic materials. The (13)C MAS NMR spectra of trans-[Ni(acac)2(PMe2Ph)2], trans-[Ni(acac)2(PMePh2)2], and the noncrystallographically characterized trans-[Ni(acac)2(dppe)]n were assigned using these correlations. The complexes with L = H2O, D2O, NH3, and MeOH can be prepared by a series of solid state desorption and sorption reactions. Crystal structures for trans-[Ni(acac)2(NH3)2] and trans-[Ni(acac)2(PMePh2)2] are reported. PMID:24325293

Lennartson, Anders; Christensen, Lene Ulrikke; McKenzie, Christine J; Nielsen, Ulla Gro

2014-01-01

229

Cation Modulation of Bicelle Size and Magnetic Alignment as Revealed by Solid-State NMR and Electron Microscopy  

Microsoft Academic Search

The influence of salts (KCl, NaCl, CaCl2, and MgCl2) on bicelles (bilayered micelles) made of dimyristoylphosphatidylcholine (DMPC, molar fraction X=78%) and dicaproylphosphatidylcholine (DCPC) was investigated by solid-state 31P- and 2H NMR as well as by freeze-fracture electron microscopy. Sizes were determined from 2H- and 31P NMR on the basis of a model that incorporated a planar bilayer and a (half-torus)

Alexandre Arnold; Thomas Labrot; Reiko Oda; Erick J. Dufourc

2002-01-01

230

Solid-state 13C NMR spectroscopy studies of xylans in the cell wall of Palmaria palmata (L. Kuntze, Rhodophyta)  

Microsoft Academic Search

The chemical structure and interactions of the cell wall polysaccharides from the red edible seaweed Palmaria palmata were studied by liquid-like magic-angle-spinning (MAS) and cross-polarization MAS (CPMAS) solid-state 13C NMR spectroscopy. The liquid-like MAS and CPMAS 13C NMR spectra of the rehydrated algal powder revealed the presence of ?-(1?4)\\/?-(1?3)-linked d-xylan with chemical shifts close to those observed in the solution

Marc Lahaye; Corinne Rondeau-Mouro; Estelle Deniaud; Alain Buléon

2003-01-01

231

Solid-State NMR Investigation of the Selective Perturbation of Lipid Bilayers by the Cyclic Antimicrobial Peptide RTD1 †  

Microsoft Academic Search

RTD-1 is a cyclic ‚-hairpin antimicrobial peptide isolated from rhesus macaque leukocytes. Using 31P, 2H, 13C, and 15N solid-state NMR, we investigated the interaction of RTD-1 with lipid bilayers of different compositions. 31P and 2H NMR of uniaxially oriented membranes provided valuable information about how RTD-1 affects the static and dynamic disorder of the bilayer. Toward phosphatidylcholine (PC) bilayers, RTD-1

Jarrod J. Buffy; Melissa J. McCormick; Sungsool Wi; Alan Waring; Robert I. Lehrer; Mei Hong

2004-01-01

232

Solid-state NMR characterization of a controlled-pore glass and of the effects of electron irradiation  

Microsoft Academic Search

Controlled-pore glasses (CPGs) are silica-based materials which provide an adequate model system for a better understanding of the radiation chemistry of glasses, especially under nanoscopic confinement. This paper presents a characterization of a nanoporous CPG before and after electron irradiation using multinuclear solid-state magnetic resonance (NMR). 1H MAS NMR has been used for studying the surface proton sites and it

F. Brunet; T. Charpentier; S. Le Caër; J.-P. Renault

2008-01-01

233

Dual acquisition magic-angle spinning solid-state NMR-spectroscopy: simultaneous acquisition of multidimensional spectra of biomacromolecules.  

PubMed

Fast data collection: a general method for dual data acquisition of multidimensional magic-angle spinning solid-state NMR experiments is presented. The method uses a simultaneous Hartmann-Hahn cross-polarization from (1)H to (13)C and (15)N nuclei and exploits the long-living (15)N polarization for parallel acquisition of two multidimensional experiments. PMID:22311700

Gopinath, T; Veglia, Gianluigi

2012-03-12

234

Solid-state MAS NMR studies on the hydrothermal stability of the zeolite catalysts for residual oil selective catalytic cracking  

Microsoft Academic Search

By using the solid-state MAS NMR technique, the hydrothermal stabilities (under 100% steam at 1073 K) of HZSM-5 zeolites modified by lanthanum and phosphorus have been studied. They are excellent zeolite catalysts for residual oil selective catalytic cracking (RSCC) processes. It was indicated that the introduction of phosphorus to the zeolite via impregnation with orthophosphoric acid led to dealumination as

Jianqin Zhuang; Ding Ma; Gang Yang; Zhimin Yan; Xiumei Liu; Xianchun Liu; Xiuwen Han; Xinhe Bao; Peng Xie; Zhongmin Liu

2004-01-01

235

Solid state (sup 31)P NMR study of phosphonate binding sites in guanidine-functionalized, molecular imprinted silica xerogels.  

National Technical Information Service (NTIS)

Phosphonate binding sites in guanidine and ammonium surface-functionalized silica xerogels were prepared via the molecular imprinting technique and characterized using solid state (sup 31)P MAS NMR. One-point, two-point, and non-specific host-guest intera...

D. Y. Sasaki T. D. Alam

2000-01-01

236

Dynamic nuclear polarization experiments at 14.1 T for solid-state NMR.  

PubMed

Instrumentation for high-field dynamic nuclear polarization (DNP) at 14.1 T was developed to enhance the nuclear polarization for NMR of solids. The gyrotron generated 394.5 GHz submillimeter (sub-mm) wave with a power of 40 W in the second harmonic TE(0,6) mode. The sub-mm wave with a power of 0.5-3 W was transmitted to the sample in a low-temperature DNP-NMR probe with a smooth-wall circular waveguide system. The (1)H polarization enhancement factor of up to about 10 was observed for a (13)C-labeled compound with nitroxyl biradical TOTAPOL. The DNP enhancement was confirmed by the static magnetic field dependence of the NMR signal amplitude at 90 K. Improvements of the high-field DNP experiments are discussed. PMID:20518128

Matsuki, Yoh; Takahashi, Hiroki; Ueda, Keisuke; Idehara, Toshitaka; Ogawa, Isamu; Toda, Mitsuru; Akutsu, Hideo; Fujiwara, Toshimichi

2010-06-14

237

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

PubMed Central

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

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

2013-01-01

238

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

PubMed

Structure determination of protein binding to noncrystalline macromolecular assemblies such as plant cell walls (CWs) poses a significant structural biology challenge. CWs are loosened during growth by expansin proteins, which weaken the noncovalent network formed by cellulose, hemicellulose, and pectins, but the CW target of expansins has remained elusive because of the minute amount of the protein required for activity and the complex nature of the CW. Using solid-state NMR spectroscopy, combined with sensitivity-enhancing dynamic nuclear polarization (DNP) and differential isotopic labeling of expansin and polysaccharides, we have now determined the functional binding target of expansin in the Arabidopsis thaliana CW. By transferring the electron polarization of a biradical dopant to the nuclei, DNP allowed selective detection of (13)C spin diffusion from trace concentrations of (13)C, (15)N-labeled expansin in the CW to nearby polysaccharides. From the spin diffusion data of wild-type and mutant expansins, we conclude that to loosen the CW, expansin binds highly specific cellulose domains enriched in xyloglucan, whereas more abundant binding to pectins is unrelated to activity. Molecular dynamics simulations indicate short (13)C-(13)C distances of 4-6 Å between a hydrophobic surface of the cellulose microfibril and an aromatic motif on the expansin surface, consistent with the observed NMR signals. DNP-enhanced 2D (13)C correlation spectra further reveal that the expansin-bound cellulose has altered conformation and is enriched in xyloglucan, thus providing unique insight into the mechanism of CW loosening. DNP-enhanced NMR provides a powerful, generalizable approach for investigating protein binding to complex macromolecular targets. PMID:24065828

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

2013-10-01

239

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

240

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

241

Solid-state 13C NMR study of na-cellulose complexes.  

PubMed

The interaction of microcrystalline cellulose from cotton and aqueous sodium hydroxide was investigated by 13C NMR solid-state spectroscopy as a function of temperature and sodium hydroxide concentration. When the concentration of NaOH was increased, the initial cellulose spectrum was replaced successively by that of Na-cellulose I followed by that of Na-cellulose II. In Na-cellulose I, each carbon atom occurred as a singlet, thus implying that one glucosyl moiety was the independent magnetic residue in the structure of this allomorph. In addition, the occurrence of the C6 near 62 ppm is an indication of a gt conformation for the hydroxymethyl group of Na-cellulose I. In Na-cellulose II, the analysis of the resonances of C1 and C6 points toward a structure based on a cellotriosyl moiety as the independent magnetic residue, in agreement with the established X-ray analysis that has shown that for this allomorph, the fiber repeat was also that of a cellotriosyl residue. For Na-cellulose II, the occurrence of the C6 in the 60 ppm region indicates an overall gg conformation for the hydroxymethyl groups. A comparison of the spectra recorded at 268 K and at room temperature confirms the stronger interaction of NaOH with cellulose when the temperature is lowered. In the Q region, corresponding to NaOH concentrations of around 9% and temperatures below 277 K, most of the sample was dissolved and no specific solid-state 13C NMR spectrum could be recorded, except for that of a small fraction of undissolved cellulose I. The same experiment run on a wood pulp sample leads to a new spectrum, with spectral characteristics different from those of Na-cellulose I and Na-cellulose II. This new spectrum is assigned to the Q phase, which appears to result from topological constraints that are present in whole wood pulp fibers but not in microcrystalline cellulose. A spectrum recorded for samples in the Na-cellulose III conditions resembled that of Na-cellulose II but of lower resolution. Similarly, a spectrum of a sample of Na-cellulose IV was identical to that of hydrated cellulose II. These observations have allowed us to propose a simplified phase diagram of the cellulose/NaOH system in terms of temperature and NaOH concentration. This diagram, which is simpler than the one deduced from X-ray analysis, consists of only four different regions partially overlapping. PMID:17661517

Porro, Fabrizio; Bédué, Olivier; Chanzy, Henri; Heux, Laurent

2007-08-01

242

Solid-state NMR and IRMS characterization of smouldered peat from ombrotrophic cores  

NASA Astrophysics Data System (ADS)

Smouldering fires are slow, low temperature, flameless and the most persistent form of combustion of organic matter (OM) in porous form. Although smouldering fires of peatlands represent a large perturbation of the atmospheric chemistry, to date, most studies on smouldering focused on ignition, carbon (C) losses or emissions, whereas the literature still lacks understanding of the OM evolution following these events. The potential to track OM changes able to serve as new proxies for the identification of past fire events along peat cores is extremely important, especially considering that bogs are often used as natural archives of paleoenvironmental changes. In the present work we show preliminary results about solid-state Nuclear Magnetic Resonance (NMR) and Isotope-Ratio Mass Spectroscopy (IRMS) characterization of peat OM along three Sphagnum peat columns (26 cm deep) having different initial moisture contents (MC): 50% MC, 100% MC, and 200% MC. The 15N spectrum of fresh peat (FP) used as control shows, as expected, only an amide signal, which is in agreement with the 13C NMR spectrum where mainly signals of carbohydrates and alkyl C can be observed. Further signals can be observed in the aromatic region, most probably due to lignin derivatives. Following the smouldering event, selected peat samples from both the 50% and 100% MC series show, as expected, signals supporting the occurrence of fire. In detail, the 15N-signals between -200 and -250 ppm are typical for pyrrole or indole type N. This is in accordance with the 13C NMR spectra showing considerable intensity in the aromatic region, most likely from char residues. Isotopic signatures (i.e., ?13C and ?15N) show a very interesting behaviour. In detail, ?13C seems to be slightly affected by smouldering, although the information about vegetational changes are preserved, whereas the ?15N shows a trend positively correlated with the relative N enrichment observed in smouldered peat samples, as also supported by 15N NMR. While further research is in progress to find reliable proxies allowing reconstruction of ancient smouldering events along peat profiles, our data provide an additional important insight towards assessing palaeoenvironmental conditions and highlighting that smouldering fires may have been overlooked as the cause of molecular and chemical variations observed in peat cores. The present research was financed by the Italian PRIN program 2009 (2009NBHPWR - Project title: "Chemical and biomolecular indicators for reconstructing environmental changes in natural archives")

Zaccone, Claudio; Rein, Guillermo; Gioacchini, Paola; Knicker, Heike; Ciavatta, Claudio; Miano, Teodoro M.

2013-04-01

243

Evidence from Solid-State NMR for Nonhelical Conformations in the Transmembrane Domain of the Amyloid Precursor Protein  

PubMed Central

The amyloid precursor protein (APP) is subject to proteolytic processing by ?-secretase within neuronal membranes, leading to Alzheimer's disease-associated ?-amyloid peptide production by cleavage near the midpoint of the single transmembrane (TM) segment of APP. Conformational properties of the TM segment may affect its susceptibility to ?-secretase cleavage, but these properties have not been established definitively, especially in bilayer membranes with physiologically relevant lipid compositions. In this article, we report an investigation of the APP-TM conformation, using 13C chemical shifts obtained with two-dimensional solid-state NMR spectroscopy as site-specific conformational probes. We find that the APP-TM conformation is not a simple ?-helix, particularly at 37°C in multilamellar vesicles with compositions that mimic the composition of neuronal cell membranes. Instead, we observe a mixture of helical and nonhelical conformations at the N- and C-termini and in the vicinity of the ?-cleavage site. Conformational plasticity of the TM segment of APP may be an important factor in the ?-secretase cleavage mechanism.

Lu, Jun-Xia; Yau, Wai-Ming; Tycko, Robert

2011-01-01

244

Solid-state NMR and XANES studies of lithium and silver silicate gels synthesized by the sol–gel route  

Microsoft Academic Search

The objective of this study is to understand the effect of low temperature sol–gel synthesis on the microstructural properties of lithium [xLi2O–(1?x)SiO2; x=0.1–0.8 in steps of 0.1] and silver [xAg2O–(1?x)SiO2; x=0.1–0.8 in steps of 0.1] silicate xerogels via solid state nuclear magnetic resonance (NMR) and X-ray absorption near edge structure (XANES) techniques. The Li silicate xerogels were analyzed with solid-state

A. A. Mrse; P. L. Bryant; F. J. Hormes; L. G. Butler; N. Satyanarayana; B. Rambabu

2003-01-01

245

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

246

Solid-state NMR studies of ion dynamics in proton-conducting polymers and composites  

NASA Astrophysics Data System (ADS)

High resolution solid state 1H NMR is used to investigate proton mobility of Nafion, Sulfonated Polyether Ether Ketones(S-PEEK) and their composites, which provides better understanding of their proton conductivities. Proton exchange between sulfonic acid groups and water was observed in these materials. The proton mobility is dependent on both the temperature and the water content. Variable temperature experiments were used to determine the activation energy for proton transportation which generally increases with decrease in hydration level. The preparation of Nafion/SiO2 composites can cause large difference in proton diffusion coefficients and proton conductivities in dried states. This indicates that the amount of dopants needs to be optimized to minimize the blocking of proton diffusion pathways by dopant particles. Detailed information on the control of surface hydroxyl groups in Nafion/SiO2 is obtained through the combination of 29Si and 1H NMR. Although hydrated Nafion/ZrP composites show reduced proton activation energy, they present lower proton conductivity at 35 °C than unmodified Nafion. For composites dried at 160 °C, both the conversion of monohydrogen phosphate into pyrophosphate and the protonation of monohydrogen phosphate have been observed, which could be one of reasons for the decreased proton conductivity after rehydration. Under high humidification, a single or multiple sulfonic acid proton environments was observed in S-PEEKs, which explains the small proton conductivity difference between some of S-PEEKs. However, the observed conductivity difference for S-PEEKs cast from different solvents was attributed to distinct mobilities of polymer chains. In the crosslinked S-PEEK, not all the crosslinkers of ethylene glycol are fully crosslinked. Proton exchange between residual sulfonic acid and hydroxyls of the crosslinker was observed, which is the primary reason that the crosslinked S-PEEK, with very low residual degree of sulfonation (13 %), still shows proton conductivity comparable to those of S-PEEKs.

Ye, Gang

247

Solid-state {sup 109}Ag NMR characterization of silver dispersed on oxide supports  

SciTech Connect

Magic angle spinning {sup 109}Ag solid-state NMR spectroscopy, transmission electron microscopy, X-ray diffraction, and gas adsorption measurements were used to characterize Ag particles supported on SiO{sub 2}, {eta}-Al{sub 2}O{sub 3}, and zeolite A. The samples were prepared either by a standard incipient wetness technique or by ion exchange followed by drying and reduction in H{sub 2}. {sup 109}Ag NMR spectroscopy was used to follow the state of the silver throughout the preparation process. {sup 109}Ag spectra were obtained for metallic Ag and for pure powder samples of AgNO{sub 3} and AgCl as well as for Ag{sup +} in solution; however, no resonances were observed for powder samples of Ag{sub 2}O and Ag{sub 2}O{sub 2}. Prior to drying, chemical shifts were found to be close to those of aqueous AgNO{sub 3} solutions ({approximately}O ppm), and after drying at 373 K, the chemical shift moved upfield to approach that of bulk AgNO{sub 3}. After reduction, single Knight-shifted metallic resonance at +5252{plus_minus} 10 ppm was observed for all samples which contained Ag particles larger than 50 nm in diameter. Low-loading, well-dispersed samples with smaller Ag particles yielded no observable {sup 109}Ag resonance. It is proposed that the absence of an observable {sup 109}Ag signal in the latter samples is due to a surface boundary effect on conduction electrons, common to other metal conductors, which broadens the signal. The adsorption of O{sub 2}, Cl{sub 2}, and HCl on the surface of the large Ag crystallites had no effect on the {sup 109}Ag spectrum. 33 refs., 10 figs., 2 tabs.

Plischke, J.K.; Benesi, A.J.; Vannice, M.A. [Pennsylvania State Univ., University Park, PA (United States)

1992-04-30

248

Biomolecular solid state NMR with magic-angle spinning at 25 K  

PubMed Central

A magic-angle spinning (MAS) probe has been constructed which allows the sample to be cooled with helium, while the MAS bearing and drive gases are nitrogen. The sample can be cooled to 25 K using roughly 3 liters/hour of liquid helium, while the 4 mm diameter rotor spins at 6.7 kHz with good stability (±5 Hz) for many hours. Proton decoupling fields up to at least 130 kHz can be applied. This helium-cooled MAS probe enables a variety of one-dimensional and two-dimensional NMR experiments on biomolecular solids and other materials at low temperatures, with signal-to-noise proportional to 1/T. We show examples of low-temperature 13C NMR data for two biomolecular samples, namely the peptide A?14–23 in the form of amyloid fibrils and the protein HP35 in frozen glycerol/water solution. Issues related to temperature calibration, spin-lattice relaxation at low temperatures, paramagnetic doping of frozen solutions, and 13C MAS NMR linewidths are discussed.

Thurber, Kent R.; Tycko, Robert

2009-01-01

249

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

250

A (-)-menthyl bonded silica phase for chiral separations:? synthesis and solid state NMR characterization.  

PubMed

A new (-)-menthyl bonded silica phase has been prepared by hydrosilation of a hydride silica intermediate. The hydride silica intermediate was synthesized by the reaction of a monoalkoxysilane (CH(3))(2)SiH(OEt) with silica gel, yielding a relatively high surface coverage (4.4 ?mol/m(2)) of SiH groups. This intermediate was then used successfully in the preparation of a monomeric (-)-menthyl bonded silica phase. The bonded phase produced has been used for the chromatographic separation of enantiomers in a reversed phase mode (chiral separations). Solid state (13)C and (29)Si CP-MAS NMR spectroscopy and DRIFT spectroscopy provides valuable information on the structure of the different surface species formed on silica after modification. The surface coverage of the hydride silica intermediate and of the final bonded silica phase produced are also determined. It is found that this modification procedure can exclusively produce a monomeric coverage of SiH groups on the silica surface and can further produce a final monomeric bonded organic silica phase for the separation of enantiomers. PMID:21639299

Lynch, B; Glennon, J D; Tröltzsch, C; Menyes, U; Pursch, M; Albert, K

1997-05-01

251

Flexibility of molecular films as determined by deuterium solid state NMR  

NASA Astrophysics Data System (ADS)

A new technique is proposed for the measurement of the bilayer bending modulus kappa, in the lamellar phase L{?} of lyotropic systems. It resides in the measurement of quadrupolar splittings by deuterium solid state NMR. By separating the different motional contributions accounting for the reorientation of the C-D bond with respect to the magnetic field, we have calculated within a simple Gaussian theory the effect of thermal fluctuations of the film upon the recorded quadrupolar splitting. This has been applied to the study of the effects of membrane composition on the mean bending modulus kappa in ternary and pseudo ternary systems of water-(salt)-sodium dodecyl sulfate-alcohol. It is found that kappa is sensitive both to the amount of alcohol in the membrane and to the alcohol chain length, with typical values increasing between 1.3 k_B T and 13.0 k_B T from bexanol to decanol systems. Our results allow to attribute the reduction in kappa obtained by replacing surfactant by alcohol to the thinning of the membrane and to the increase of the area occupied by the surfactant at the interface.

Auguste, F.; Barois, P.; Fredon, L.; Clin, B.; Dufourc, E. J.; Bellocq, A. M.

1994-12-01

252

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

253

Solid-state NMR studies of metal-free SOD1 fibrillar structures.  

PubMed

Copper-zinc superoxide dismutase 1 (SOD1) is present in the protein aggregates deposited in motor neurons of amyotrophic lateral sclerosis (ALS) patients. ALS is a neurodegenerative disease that can be either sporadic (ca. 90%) or familial (fALS). The most widely studied forms of fALS are caused by mutations in the sequence of SOD1. Ex mortuo SOD1 aggregates are usually found to be amorphous. In vitro SOD1, in its immature reduced and apo state, forms fibrillar aggregates. Previous literature data have suggested that a monomeric SOD1 construct, lacking loops IV and VII, (apoSOD?IV-VII), shares the same fibrillization properties of apoSOD1, both proteins having the common structural feature of the central ?-barrel. In this work, we show that structural information can be obtained at a site-specific level from solid-state NMR. The residues that are sequentially assignable are found to be located at the putative nucleation site for fibrillar species formation in apoSOD, as detected by other experimental techniques. PMID:24719206

Banci, Lucia; Blaževitš, Olga; Cantini, Francesca; Danielsson, Jens; Lang, Lisa; Luchinat, Claudio; Mao, Jiafei; Oliveberg, Mikael; Ravera, Enrico

2014-06-01

254

High-resolution solid-state NMR structure of alanyl-prolyl-glycine.  

PubMed

We present a de novo high-resolution structure of the peptide Alanyl-Prolyl-Glycine using a combination of sensitive solid-state NMR techniques that each yield precise structural constraints. High-quality (13)C-(13)C distance constraints are extracted by fitting rotational resonance width (R(2)W) experiments using Multimode Multipole Floquet Theory and experimental chemical shift anisotropy (CSA) orientations. In this strategy, a structure is first calculated using DANTE-REDOR and torsion angle measurements and the resulting relative CSA orientations are used as an input parameter in the (13)C-(13)C distance calculations. Finally, a refined structure is calculated using all the constraints. We investigate the effect of different structural constraints on structure quality, as determined by comparison to the crystal structure and also self-consistency of the calculated structures. Inclusion of all or subsets of these constraints into CNS calculations resulted in high-quality structures (0.02A backbone RMSD using all 11 constraints). PMID:19596601

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

2009-09-01

255

Characterization of tautomeric forms of ranitidine hydrochloride: thermal analysis, solid-state NMR, X-ray  

NASA Astrophysics Data System (ADS)

The molecular structure of ranitidine hydrochloride (RAN-HCl) has an important influence on the growth of individual crystals and consequently the physical properties such as bulk solid density. This paper suggests that the correct structure of the nitroethenediamine moiety in the Form 2 RAN-HCl is a mixture of enamine and nitronic acid tautomers. Thermal analysis showed that the difference between the two forms is configurational rather than conformational. It also showed explosive type of degradation at the melting point of both forms. Solid-state NMR studies suggest that Form 2 contains molecular disorder whereas Form 1 may be more ordered. A single crystal X-ray study confirms the disorder in Form 2 but a similar study on Form 1 could not be performed and its suspected order can only be inferred. It was found that significant amounts of strongly polar solvents such as methanol and water would favour the production of Form 2; while anhydrous less polar or non-polar solvents will result in the production of Form 1. Chloride ion acts as the bridge between the individual molecules of RAN-HCl in the crystal structure of Form 2.

Mirmehrabi, M.; Rohani, S.; Murthy, K. S. K.; Radatus, B.

2004-01-01

256

Solid-state NMR structure determination of whole anchoring threads from the blue mussel Mytilus edulis.  

PubMed

The molecular structure of the blue mussel Mytilus edulis whole anchoring threads was studied by two-dimensional (13)C solid-state NMR on fully labeled fibers. This unique material proves to be well ordered at a molecular level despite its heterogeneous composition as evidenced by the narrow measured linewidths below 1.5 ppm. The spectra are dominated by residues in collagen environments, as determined from chemical shift analysis, and a complete two-dimensional assignment (including minor amino acids) was possible. The best agreement between predicted and experimental backbone chemical shifts was obtained for collagen helices with torsion angles (-75°, +150°). The abundant glycine and alanine residues can be resolved in up to five different structural environments. Alanine peaks could be assigned to collagen triple-helices, ?-sheets (parallel and antiparallel), ?-turns, and unordered structures. The use of ATR-FTIR microscopy confirmed the presence of these structural environments and enabled their location in the core of the thread (collagen helices and antiparallel ?-sheets) or its cuticle (unordered structures). The approach should enable characterization at the molecular level of a wide range of byssus macroscopic properties. PMID:23163352

Arnold, Alexandre A; Byette, Frédéric; Séguin-Heine, Marc-Olivier; Leblanc, André; Sleno, Lekha; Tremblay, Réjean; Pellerin, Christian; Marcotte, Isabelle

2013-01-14

257

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.

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

2010-01-01

258

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

NASA Astrophysics Data System (ADS)

We present a de novo high-resolution structure of the peptide Alanyl-Prolyl-Glycine using a combination of sensitive solid-state NMR techniques that each yield precise structural constraints. High-quality 13C- 13C distance constraints are extracted by fitting rotational resonance width (R 2W) experiments using Multimode Multipole Floquet Theory and experimental chemical shift anisotropy (CSA) orientations. In this strategy, a structure is first calculated using DANTE-REDOR and torsion angle measurements and the resulting relative CSA orientations are used as an input parameter in the 13C- 13C distance calculations. Finally, a refined structure is calculated using all the constraints. We investigate the effect of different structural constraints on structure quality, as determined by comparison to the crystal structure and also self-consistency of the calculated structures. Inclusion of all or subsets of these constraints into CNS calculations resulted in high-quality structures (0.02 Å backbone RMSD using all 11 constraints).

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

2009-09-01

259

Structure and dynamics of DNA and RNA oligonucleotides as studied using solution and solid state NMR. [NMR (nuclear magnetic resonance)  

SciTech Connect

NMR experiments reveal that the base H8/H6 and H1[prime] protons of RNA have T[sub 1] relaxation times that are distinctly longer than those of DNA. NMR and circular dichroism experiments indicate that the segments of RNA maintain their A-form geometry even in the interior of DNA-RNA-DNA chimeric duplexes, suggesting that the relaxation times are correlated with the type of helix topology. Results from solid state [sup 2]H NMR experiments on the purine C-8 deuterium-labeled 12 base pair RNA duplex [r(CG*CG*A*A*UUGG*CG*)][sub 2] were compared with results obtained by other investigators on the 12 base pair DNA duplex [d(CG*CG*A*A*TTCG*CG*)][sub 2]. The motional amplitudes of DNA and RNA purines are similar at 0%-88% RH and their internal rates of motion are different at 0%-80% RH. The assumption that dodecameric oligonucleotides (12-mers) tumble isotropically in solution is often used when calculating proton-proton distances from NOE data. The authors have undertaken the task of testing the isotropic assumption using experimental NMR data. The authors have calculated the structure of [d(GCGTTTAAACGC)][sub 2] using both the isotropic assumption and the assumption that the duplex tumbles anisotropically in solution like a perfect cylinder. The resulting structures from both approaches are virtually indistinguishable. The isotropic assumption is valid for oligonucleotides 12 base pairs and shorter. The solution structure of the 12 base pair hybrid chimeric duplex [r(gcg)d(TATATACGC)][sub 2] has been solved using NMR techniques combined with distance geometry and NOE back-calculation methods. The structure is characterized by a dramatic bend of 52[degrees] in the helix axis. The location of the bend is not at the RNA-DNA step but occurs between the first and second residues of the DNA segment. The center of the DNA TATATA segment has a remarkably narrow minor groove that becomes very wide in the hybrid portions of the duplex.

Wang, A.C.C.

1992-01-01

260

Conformational Changes of an Ion Channel Detected Through Water-Protein Interactions Using Solid-State NMR Spectroscopy  

PubMed Central

The influenza A virus M2 protein is a pH-gated and amantadine-inhibited proton channel important for the virus life cycle. Proton conduction by M2 is known to involve water, however direct experimental evidence of M2-water interaction is scarce. Using 1H spin diffusion solid-state NMR, we have now determined the water accessibility of the M2 transmembrane domain (M2-TM) in virus-envelope-mimetic lipid membranes and its changes with environment. Site-specific water-protein magnetization transfer indicates that, in the absence of amantadine, the initial spin diffusion rate mainly depends on the radial position of the residues from the pore: pore-lining residues along the helix have similarly high water accessibilities compared to lipid-facing residues. Upon drug binding, the spin diffusion rates become much slower for Gly34 in the middle of the helix than for the N-terminal residues, indicating that amantadine is bound to the pore lumen between Gly34 and Val27. Water-protein spin diffusion buildup curves indicate that spin diffusion is the fastest in the low-pH open state, slower in the high-pH closed state, and the slowest in the high-pH amantadine-bound state. Simulations of the buildup curves using a 3D lattice model yielded quantitative values of the water-accessible surface area and its changes by pH and drug binding. These data provide direct experimental evidence of the pH-induced change of the pore size and the drug-induced dehydration of the pore. This study demonstrates the capability of 1H spin diffusion NMR for elucidating water interactions with ion channels, water pores, and proton pumps, and for probing membrane protein conformational changes that involve significant changes of water-accessible surface areas.

Luo, Wenbin; Hong, Mei

2010-01-01

261

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

PubMed Central

Sphingomyelin is a lipid that is abundant in the nervous systems of mammals, where it is associated with putative microdomains in cellular membranes and undergoes alterations due to aging or neurodegeneration. We investigated the effect of varying the concentration of cholesterol in binary and ternary mixtures with N-palmitoylsphingomyelin (PSM) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) using deuterium nuclear magnetic resonance (2H NMR) spectroscopy in both macroscopically aligned and unoriented multilamellar dispersions. In our experiments, we used PSM and POPC perdeuterated on the N-acyl and sn-1 acyl chains, respectively. By measuring solid-state 2H NMR spectra of the two lipids separately in mixtures with the same compositions as a function of cholesterol mole fraction and temperature, we obtained clear evidence for the coexistence of two liquid-crystalline domains in distinct regions of the phase diagram. According to our analysis of the first moments M1 and the observed 2H NMR spectra, one of the domains appears to be a liquid-ordered phase. We applied a mean-torque potential model as an additional tool to calculate the average hydrocarbon thickness, the area per lipid, and structural parameters such as chain extension and thermal expansion coefficient in order to further define the two coexisting phases. Our data imply that phase separation takes place in raftlike ternary PSM/POPC/cholesterol mixtures over a broad temperature range but vanishes at cholesterol concentrations equal to or greater than a mole fraction of 0.33. Cholesterol interacts preferentially with sphingomyelin only at smaller mole fractions, above which a homogeneous liquid-ordered phase is present. The reasons for these phase separation phenomena seem to be differences in the effects of cholesterol on the configurational order of the palmitoyl chains in PSM-d31 and POPC-d31 and a difference in the affinity of cholesterol for sphingomyelin observed at low temperatures. Hydrophobic matching explains the occurrence of raftlike domains in cellular membranes at intermediate cholesterol concentrations but not saturating amounts of cholesterol.

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

2009-01-01

262

Raftlike mixtures of sphingomyelin and cholesterol investigated by solid-state 2H NMR spectroscopy.  

PubMed

Sphingomyelin is a lipid that is abundant in the nervous systems of mammals, where it is associated with putative microdomains in cellular membranes and undergoes alterations due to aging or neurodegeneration. We investigated the effect of varying the concentration of cholesterol in binary and ternary mixtures with N-palmitoylsphingomyelin (PSM) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) using deuterium nuclear magnetic resonance ((2)H NMR) spectroscopy in both macroscopically aligned and unoriented multilamellar dispersions. In our experiments, we used PSM and POPC perdeuterated on the N-acyl and sn-1 acyl chains, respectively. By measuring solid-state (2)H NMR spectra of the two lipids separately in mixtures with the same compositions as a function of cholesterol mole fraction and temperature, we obtained clear evidence for the coexistence of two liquid-crystalline domains in distinct regions of the phase diagram. According to our analysis of the first moments M1 and the observed (2)H NMR spectra, one of the domains appears to be a liquid-ordered phase. We applied a mean-torque potential model as an additional tool to calculate the average hydrocarbon thickness, the area per lipid, and structural parameters such as chain extension and thermal expansion coefficient in order to further define the two coexisting phases. Our data imply that phase separation takes place in raftlike ternary PSM/POPC/cholesterol mixtures over a broad temperature range but vanishes at cholesterol concentrations equal to or greater than a mole fraction of 0.33. Cholesterol interacts preferentially with sphingomyelin only at smaller mole fractions, above which a homogeneous liquid-ordered phase is present. The reasons for these phase separation phenomena seem to be differences in the effects of cholesterol on the configurational order of the palmitoyl chains in PSM-d31 and POPC-d31 and a difference in the affinity of cholesterol for sphingomyelin observed at low temperatures. Hydrophobic matching explains the occurrence of raftlike domains in cellular membranes at intermediate cholesterol concentrations but not saturating amounts of cholesterol. PMID:18839945

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

2008-11-01

263

AssignFit: A program for simultaneous assignment and structure refinement from solid-state NMR spectra  

NASA Astrophysics Data System (ADS)

AssignFit is a computer program developed within the XPLOR-NIH package for the assignment of dipolar coupling (DC) and chemical shift anisotropy (CSA) restraints derived from the solid-state NMR spectra of protein samples with uniaxial order. The method is based on minimizing the difference between experimentally observed solid-state NMR spectra and the frequencies back calculated from a structural model. Starting with a structural model and a set of DC and CSA restraints grouped only by amino acid type, as would be obtained by selective isotopic labeling, AssignFit generates all of the possible assignment permutations and calculates the corresponding atomic coordinates oriented in the alignment frame, together with the associated set of NMR frequencies, which are then compared with the experimental data for best fit. Incorporation of AssignFit in a simulated annealing refinement cycle provides an approach for simultaneous assignment and structure refinement (SASR) of proteins from solid-state NMR orientation restraints. The methods are demonstrated with data from two integral membrane proteins, one ?-helical and one ?-barrel, embedded in phospholipid bilayer membranes.

Tian, Ye; Schwieters, Charles D.; Opella, Stanley J.; Marassi, Francesca M.

2012-01-01

264

Solid-state NMR investigations of peptide-lipid interactions of the transmembrane domain of a plant-derived protein, Hcf106.  

PubMed

The chloroplast twin arginine translocation system transports highly folded precursor proteins across the thylakoid using the protonmotive force as its only energy source. Hcf106 and another thylakoid protein, cpTatC compose the precursor receptor complex. Hcf106 is predicted to contain a single amino terminal transmembrane domain (TMD) followed by a Pro-Gly hinge, an amphipathic ?-helix, and a loosely structured carboxyl terminus. Hcf106 has been shown biochemically to insert spontaneously into thylakoid membranes; however, how this occurs is not understood. To investigate how Hcf106 inserts itself into the membrane unassisted, solid-state NMR spectroscopy was used to investigate the membrane activity of the TMD. A synthetic peptide of the Hcf106 TMD was incorporated into multilamellar vesicles made of 100% 1-palmitoyl-2-oleoyl-sn-glycero-phosphocholine (POPC) or 85%:15% ratio with monogalactosyl diacylglycerol (POPC/MGDG) to probe peptide-lipid interaction. Solid-state (31)P NMR and (2)H NMR spectroscopic techniques were used to reveal peptide perturbations of the phospholipid membranes. Changes in spectral lineshape, chemical shift anisotropy width, (31)P T1 relaxation time and SCD order parameters demonstrated that the Hcf106 TMD peptide interacted with the phospholipids. Furthermore, the comparison between POPC and POPC/MGDG multilamellar vesicles indicated that lipid bilayer composition affected the peptide-lipid interaction with the peptide interacting preferentially with vesicles that more closely mimic the thylakoid. PMID:24075840

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

2013-01-01

265

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 2400 to 3000ppm. 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

266

NMR crystallography of 2-acylamino-6-[1 H]-pyridones: Solid-state NMR, GIPAW computational, and single crystal X-ray diffraction studies  

Microsoft Academic Search

2-Acylamino-6-[1H]-pyridones [acyl=RCO, where R=methyl (1), ethyl (2), iso-propyl (3), tert-butyl (4), and 1-adamantyl (5)] have been synthesized and characterized by NMR spectroscopy. From three congeners, 2, 3 and 5, also single crystal X-ray structures have been solved. For these derivatives GIPAW calculations acts as a “bridge” between solid-state NMR data and calculated chemical shifts based on X-ray determined geometry. In

Borys O?mia?owski; Erkki Kolehmainen; Satu Ikonen; Kari Ahonen; Miika Löfman

267

Characterization of the glass-to-vitroceramic transition in yttrium aluminum borate laser glasses using solid state NMR.  

PubMed

The crystallization of laser glasses in the system (Y(2)O(3))(0.2){((Al(2)O(3))(x))(B(2)O(3))(0.8-x)} (0.15 ? x ? 0.40) doped with 0.5 mol% of ytterbium oxide has been investigated by x-ray powder diffraction, and various solid state NMR techniques. The crystallization process has been analyzed in a quantitative fashion by high-resolution solid state (11)B, (27)Al, and (89)Y NMR spectroscopy as well as (11)B{(27)Al} and (27)Al{(11)B} rotational echo double resonance (REDOR) experiments. The homogeneous glasses undergo major phase segregation processes resulting in crystalline Al(5)BO(9) (historically denoted as Al(18)B(4)O(33)), YBO(3), crystalline YAl(3)(BO(3))(4), residual glassy B(2)O(3), and an additional yet not identified crystalline phase ("X-phase"). PMID:22244244

Deters, Heinz; Eckert, Hellmut

2012-02-01

268

Structure and ionic interactions of organic-inorganic composite polymer electrolytes studied by solid-state NMR and Raman spectroscopy.  

PubMed

Solid-state NMR studies of composite polymer electrolytes are reported. The materials consist of polyethylene oxide and an organic inorganic composite, together with a lithium salt, and are candidates for electrolytes in solid-state lithium ion batteries. Silicon and aluminum MAS and multiple quantum MAS are used to characterize the network character of the organic-inorganic composite, and spin diffusion measurements are used to determine the nanostructure of the polymer/composite blending. Multiple quantum spin counting is used to measure the ion aggregation. The NMR results are supported by Raman spectra, calorimetry, and impedance spectroscopy. From these experiments it is concluded that the composite suppresses polymer crystallization without suppressing its local mobility, and also suppresses the tendency for the ions to aggregate. This polymer composite thus appears very promising for application in lithium ion batteries. PMID:12469813

Joo, Chan Gyu; Bronstein, Lyudmila M; Karlinsey, Robert L; Zwanziger, Josef W

2002-01-01

269

Solid-State NMR Investigation of the Depth of Insertion of Protegrin-1 in Lipid Bilayers Using Paramagnetic Mn 2+  

Microsoft Academic Search

The depth of insertion of an antimicrobial peptide, protegrin-1 (PG-1), in lipid bilayers is investigated using solid-state NMR. Paramagnetic Mn2+ ions bind to the surface of lipid bilayers and induce distance-dependent dipolar relaxation of nuclear spins. By comparing the signal dephasing of the peptide with that of the lipids, whose segmental depths of insertion are known, we determined the depths

Jarrod J. Buffy; Teresa Hong; Satoru Yamaguchi; Alan J. Waring; Robert I. Lehrer; Mei Hong

2003-01-01

270

Solid state NMR spectroscopy investigation of the molecular structure of epoxy based materials cured in different conditions  

NASA Astrophysics Data System (ADS)

In this work two epoxy resin model systems, whose monomers are typically used in structural composites, were thermally cured in different cure conditions in order to obtain different cross-linking densities. Their molecular structures were investigated through solid state NMR spectroscopy in order to correlate them to the cure process conditions used and the results were discussed in the light of the dynamical mechanical thermal analysis (DMTA) performed.

Alessi, S.; Spinella, A.; Caponetti, E.; Sabatino, Maria Antonietta; Spadaro, G.

2012-07-01

271

Protein-induced bonding perturbation of the rhodopsin chromophore detected by double-quantum solid-state NMR  

Microsoft Academic Search

We have obtained carbon-carbon bond length data for the functional retinylidene chromophore of rhodopsin, with a spatial resolution of 3 pm. The very high resolution was obtained by performing double-quantum solid-state NMR on a set of noncrystalline isotopically labelled bovine rhodopsin samples. We detected localized perturbations of the carbon-carbon bond lengths of the retinylidene chromophore. The observations are consistent with

Marina Carravetta; Xin Zhao; Ole G. Johannessen; Wai Cheu Lai; Michiel A. Verhoeven; Petra H. M. Bovee-Geurts; Peter J. E. Verdegem; Suzanne Kiihne; Henrik Luthman; Huub J. M. de Groot; W. J. de Grip; Johan Lugtenburg; Malcolm H. Levitt

2004-01-01

272

Structural investigations of tungsten silver phosphate glasses by solid state NMR, vibrational and X-ray absorption near edge spectroscopies  

Microsoft Academic Search

Glasses were prepared in the pseudo-binary system (1?x)AgPO3–xWO3 (0?×?0.6mol%). The structural evolution of the vitreous network was studied as a function of composition by thermal analysis, Fourier Transform Infrared spectroscopy (FTIR), Raman scattering, high resolution 31P solid state NMR and XANES at the W-L1 absorption edge. For compositions with x ranging from 0 to 0.5 a pronounced increase in the

Silvia H. Santagneli; Gaël Poirier; Matthias T. Rinke; Sidney J. L. Ribeiro; Younes Messaddeq; Hellmut Eckert

2011-01-01

273

Solid-state NMR studies of methanol-to-aromatics reaction over silver exchanged HZSM-5 zeolite  

Microsoft Academic Search

Solid-state NMR spectroscopy was used to study the conversion of methanol to aromatics (MTA) over silver exchanged HZSM-5 zeolites. It is the silver oxide rather than silver cation that plays a crucial role for the MTA reaction. The aromatic products (mainly toluene and benzene) are formed at the expense of the small alkanes (mainly propane and isobutane). AgZSM-5 zeolite calcined

Danlin Zeng; Jun Yang; Jiqing Wang; Jun Xu; Yongxia Yang; Chaohui Ye; Feng Deng

2007-01-01

274

Aspects of the chemical structure of soil organic materials as revealed by solid-state13C NMR spectroscopy  

Microsoft Academic Search

Solid-state cross-polarisation\\/magic-angle-spinning3C nuclear magnetic resonance (CP\\/MAS13C NMR) spectroscopy was used to characterise semi-quantitatively the organic materials contained in particle size and density fractions isolated from five different mineral soils: two Mollisols, two Oxisols and an Andosol. The acquired spectra were analysed to determine the relative proportion of carboxyl, aromatic, O-alkyl and alkyl carbon contained in each fraction. Although similar types

J. A. Baldock; J. M. Oades; A. G. Waters; X. Peng; A. M. Vassallo; M. A. Wilson

1992-01-01

275

Quantitative determination of lead in mixtures of lead(II) halidesusing solid-state 207pb nmr spectroscopy  

SciTech Connect

A multi-spectrum technique for facile, quantitativedetermination of lead in solid materials using solid-state 207Pb NMR thatavoids the major problem of uniform excitation across a wide spectralrange has been demonstrated. The method can be employed without chemicalseparation or other chemical manipulations and without any prior samplepreparation, resulting in a non-destructive analysis, and producingresults that are in agreement with gravimetric analyses of mixed samplesof the lead halides.

Glatfelter, Alicia; Stephenson, Nicole; Bai, Shi; Dybowski,Cecil; Perry, Dale L.

2006-11-01

276

Flow-Through Lipid Nanotube Arrays for Structure-Function Studies of Membrane Proteins by Solid-State NMR Spectroscopy  

Microsoft Academic Search

A novel method for studying membrane proteins in a native lipid bilayer environment by solid-state NMR spectroscopy is described and tested. Anodic aluminum oxide (AAO) substrates with flow-through 175nm wide and 60-?m-long nanopores were employed to form macroscopically aligned peptide-containing lipid bilayers that are fluid and highly hydrated. We demonstrate that the surfaces of both leaflets of such bilayers are

Eduard Y. Chekmenev; Peter L. Gor’kov; Timothy A. Cross; Ali M. Alaouie; Alex I. Smirnov

2006-01-01

277

Determination of rifampicin location in cholesterol-lipid liposomes by 2H and 31P Solid-State NMR  

Microsoft Academic Search

Liposome encapsulated rifampicin (RIF), a first line anti-tuberculosis agent, was prepared using the chloroform film method. Cryo-transmission electron microscopy of the Hposome showed a mixture of unilamellar and multilamellar vesicles with a size of 200-300 nm. The results correlated with those obtained from dynamic light scattering. Deuterated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (d-POPC) was used to prepare liposomes for solid-state nuclear magnetic resonance (SS-NMR).

N. Changsan; F. Separovic; T. Srichana

2008-01-01

278

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

Microsoft Academic Search

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

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

2003-01-01

279

Conformation of Azobenzene?Modified Poly(??L?Glutamate) (AZOPLGA) in Thin Films: Solid State NMR Studies  

Microsoft Academic Search

The conformations of azobenzene?modified poly(??L?glutamate)s (AZOPLGA) with a different degree of functionalization were examined by solid state C NMR. The polymer main chain conformations in AZOPLGA powders (precipitated from reaction system) changes from ??helix to ??sheet when the degree of functionalization increases from 12% to 56%. In addition, the solvent used for fabricating films plays an important role in organizing

Xiaodong Wu; Suizhou Yang; Lynne A. Samuelson; Ashok L. Cholli; Jayant Kumar

2004-01-01

280

The Structure and Thermal Transformations of Allophanes Studied by 29Si and 27Al High Resolution Solid-State NMR  

Microsoft Academic Search

Examination of two volcanic and two precipitated allophanes by solid-state NMR, thermal analysis and X-ray powder diffraction shows three of the samples to contain structural features similar to both tubular imogolite and defect layer-lattice aluminosilicates such as kaolinite. The fourth allophane, a precipitated sample from New Zealand, had no imogolite-like features and contained tetrahedral as well as octahedral aluminum. The

K. J. D. MacKenzie; M. E. BOWDEN; R. H. MEINHOLD

1991-01-01

281

Characterizing slight structural disorder in solids by combined solid-state NMR and first principles calculations.  

PubMed

A general approach for structural interpretation of local disorder in partially ordered solids is proposed, combining high-resolution two-dimensional (2D) nuclear magnetic resonance (NMR) and first principles calculations. We show that small chemical shift variations of the order of a ppm can be interpreted in detailed structural terms with advanced density functional theory methods. Focusing on a model system of bisphosphinoamine, we demonstrate that the existence and the spatial range of small amplitude disorder can be probed using quantitative statistical analyses of 2D NMR line shapes obtained from through-space correlation experiments collected using variable mixing times. We show how low-energy vibration modes calculated from first principles can be conveniently used not as a cause of disorder but, instead, to generate a basis set of physically plausible local distortions to describe candidate static distributions of local geometries. Calculations of (31)P NMR isotropic chemical shifts are then used for the first time to simulate 2D correlation lineshapes associated with these distortions, which permit their evaluation as a potential source of disorder by comparison to experimental 2D cross-peaks between phosphorus sites. This new type of structural constraints allows the identification of changes in the bonding geometry that most likely contribute to the local structural disorder. We thus identify at least one type of structural deformation that is compatible with the experimental 2D NMR data and is also within the order of magnitude of the "thermal ellipsoids" associated with the uncertainties on the atomic positions of the X-ray diffraction structure. PMID:19133744

Cadars, Sylvian; Lesage, Anne; Pickard, Chris J; Sautet, Philippe; Emsley, Lyndon

2009-02-01

282

Dynamics of benzimidazole ethylphosphonate: a solid-state NMR study of anhydrous composite proton-conducting electrolytes.  

PubMed

Imidazole phosphate and phosphonate solid acids model the hydrogen-bonding networks and dynamics of the anhydrous electrolyte candidate for proton exchange membrane fuel cells. Solid-state NMR reveals that phosphate and phosphonate anion dynamics dominate the rate of long-range proton transport, and that the presence of a membrane host facilitates proton mobility, as evidenced by a decreased correlation time of the composites (80 ± 15 ms) relative to the pristine salt (101 ± 5 ms). Benzimidazole ethylphosphonate (Bi-ePA) is chosen as a model salt to investigate the membrane system. The hydrogen-bonding structure of Bi-ePA is established using X-ray diffraction coupled with solid-state (1)H-(1)H DQC NMR. The anion dynamics has been determined using solid-state (31)P CODEX NMR. By comparing the dynamics of ethylphosphonate groups in pristine salt and membrane-salt composites, it is clear that the rotation process involves three-site exchange. Through data interpretation, a stretched exponential function is introduced with the stretching exponent, ?, ranging 0 < ? ? 1. The (31)P CODEX data for pristine salt are fitted with single exponential decay where ? = 1; however, the data for the membrane-salt composites are fitted with stretched exponential functions, where ? has a constant value of 0.5. This ? value suggests a non-Gaussian distribution of the dynamic systems in the composite sample, which is introduced by the membrane host. PMID:24056920

Yan, Z Blossom; De Almeida, Nicole E; Traer, Jason W; Goward, Gillian R

2013-11-01

283

Heteronuclear X-Y double-resonance solid-state NMR: Techniques for structural characterization of inorganic materials  

NASA Astrophysics Data System (ADS)

Since the introduction of the Magic Angle Spinning (MAS) technique, solid state NMR has become an increasingly important tool in the characterization of inorganic materials. Solid state NMR experiments, however, can be very time consuming due to the low sensitivities and/or low natural abundances for many of the NMR active nuclei. Furthermore, under MAS conditions, interactions arising from the dipolar coupling are averaged to zero and any dipolar information lost. The goal of this research is to develop and apply double resonance NMR techniques which (1) may increase the sensitivity of many NMR active nuclei and (2) may preserve the resolution achieved by MAS while re-introducing the dipolar coupling information. Because of the dependence on the internuclear distance, r, the heteronuclear dipole coupling can be exploited to obtain information on local environments, internuclear distances, and to aid in spectral editing and phase identification. This study focuses on the double resonance techniques: Cross Polarization with Magic Angle Spinning (CPMAS), Heteronuclear Double Quantum Filtering (HDQF), Spin Echo Double Resonance (SEDOR), and Rotational Echo DOuble Resonance (REDOR). These techniques may be used to examine a wide variety of systems. The application of these techniques to the following systems will be demonstrated: (1) Semiconductor alloys in the CdSiAssb{2-x}Psb{x} system; (2) Crystalline and amorphous ternary Al-P-Se system; (3) Crystalline and amorphous borosilicates; (4) Zirconium phosphate substituted with vanadium.

Hudalla, Christopher John

284

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.

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

2014-01-01

285

Molecular characterization and quantification using state of the art solid-state adiabatic TOBSY NMR in burn trauma  

PubMed Central

We describe a novel solid-state nuclear magnetic resonance (NMR) method that maximizes the advantages of high-resolution magic-angle-spinning (HRMAS), relative conventional liquid-state NMR approaches, when applied to intact biopsies of skeletal muscle specimens collected from burn trauma patients. This novel method, termed optimized adiabatic TOtal through Bond correlation SpectroscopY (TOBSY) solid-state NMR pulse sequence for two-dimensional (2D)1H-1H homonuclear scalar-coupling longitudinal isotropic mixing, was demonstrated to provide a 40–60% improvement in signal-to-noise ratio (SNR) relative to its liquid-state analogue TOCSY (TOtal Correlation SpectroscopY). Using 1-and 2-dimensional HRMAS NMR experiments, we identified several metabolites in burned tissues. Quantification of metabolites in burned tissues showed increased levels of lipid compounds, intracellular metabolites (e.g., taurine and phosphocreatine) and substantially decreased water-soluble metabolites (e.g., glutathione, carnosine, glucose, glutamine/glutamate and alanine). These findings demonstrate that HRMAS NMR Spectroscopy using TOBSY is a feasible technique that reveals new insights into the pathophysiology of burn trauma. Moreover, this method has applications that facilitate the development of novel therapeutic strategies.

RIGHI, VALERIA; ANDRONESI, OVIDIU; MINTZOPOULOS, DIONYSSIOS; TZIKA, A. ARIA

2009-01-01

286

Raman Spectroscopy and Solid State NMR Characterization of Carbonates and Metal-Oxide Clusters  

NASA Astrophysics Data System (ADS)

Presented here is data showing the utility of combining Raman spectroscopy and solid-state Nuclear Magnetic Resonance. These techniques were combined to study local structure of carbonate minerals and metal oxides.

Moore, J. K.; Hammann, B. A.; Surface, J. A.; Ma, Z. L.; Hayes, S. E.

2014-06-01

287

Solid-State 2H NMR Shows Equivalence of Dehydration and Osmotic Pressures in Lipid Membrane Deformation  

PubMed Central

Lipid bilayers represent a fascinating class of biomaterials whose properties are altered by changes in pressure or temperature. Functions of cellular membranes can be affected by nonspecific lipid-protein interactions that depend on bilayer material properties. Here we address the changes in lipid bilayer structure induced by external pressure. Solid-state 2H NMR spectroscopy of phospholipid bilayers under osmotic stress allows structural fluctuations and deformation of membranes to be investigated. We highlight the results from NMR experiments utilizing pressure-based force techniques that control membrane structure and tension. Our 2H NMR results using both dehydration pressure (low water activity) and osmotic pressure (poly(ethylene glycol) as osmolyte) show that the segmental order parameters (SCD) of DMPC approach very large values of ?0.35 in the liquid-crystalline state. The two stresses are thermodynamically equivalent, because the change in chemical potential when transferring water from the interlamellar space to the bulk water phase corresponds to the induced pressure. This theoretical equivalence is experimentally revealed by considering the solid-state 2H NMR spectrometer as a virtual osmometer. Moreover, we extend this approach to include the correspondence between osmotic pressure and hydrostatic pressure. Our results establish the magnitude of the pressures that lead to significant bilayer deformation including changes in area per lipid and volumetric bilayer thickness. We find that appreciable bilayer structural changes occur with osmotic pressures in the range of 10?100 atm or lower. This research demonstrates the applicability of solid-state 2H NMR spectroscopy together with bilayer stress techniques for investigating the mechanism of pressure sensitivity of membrane proteins.

Mallikarjunaiah, K.J.; Leftin, Avigdor; Kinnun, Jacob J.; Justice, Matthew J.; Rogozea, Adriana L.; Petrache, Horia I.; Brown, Michael F.

2011-01-01

288

Insight into the Binding of Antifreeze Proteins to Ice Surfaces via 13C Spin Lattice Relaxation Solid-State NMR  

PubMed Central

The primary sequences of type I antifreeze proteins (AFPs) are Ala rich and contain three 11-residue repeat units beginning with threonine residues. Their secondary structures consist of ?-helices. Previous activity study of side-chain mutated AFPs suggests that the ice-binding side of type I AFPs comprises the Thr side chains and the conserved i + 4 and i + 8 Ala residues, where i indicates the positions of the Thrs. To find structural evidence for the AFP's ice-binding side, a variable-temperature dependent 13C spin lattice relaxation solid-state NMR experiment was carried out for two Ala side chain 13C labeled HPLC6 isoforms of the type I AFPs each frozen in H2O and D2O, respectively. The first one was labeled on the equivalent 17th and 21st Ala side chains (i + 4, 8), and the second one on the equivalent 8th, 19th, and 30th Ala side chains (i + 6). The two kinds of labels are on the opposite sides of the ?-helical AFP. A model of Ala methyl group rotation/three-site rotational jump combined with water molecular reorientation was tested to probe the interactions of the methyl groups with the proximate water molecules. Analysis of the T1 data shows that there could be 10 water molecules closely capping an i + 4 or an i + 8 methyl group within the range of van der Waals interaction, whereas the surrounding water molecules to the i + 6 methyl groups could be looser. This study suggests that the side of the ?-helical AFP comprising the i + 4 and i + 8 Ala methyl groups could interact with the ice surface in the ice/water interface.

Mao, Yougang; Ba, Yong

2006-01-01

289

Insight into the binding of antifreeze proteins to ice surfaces via 13C spin lattice relaxation solid-state NMR.  

PubMed

The primary sequences of type I antifreeze proteins (AFPs) are Ala rich and contain three 11-residue repeat units beginning with threonine residues. Their secondary structures consist of alpha-helices. Previous activity study of side-chain mutated AFPs suggests that the ice-binding side of type I AFPs comprises the Thr side chains and the conserved i + 4 and i + 8 Ala residues, where i indicates the positions of the Thrs. To find structural evidence for the AFP's ice-binding side, a variable-temperature dependent (13)C spin lattice relaxation solid-state NMR experiment was carried out for two Ala side chain (13)C labeled HPLC6 isoforms of the type I AFPs each frozen in H(2)O and D(2)O, respectively. The first one was labeled on the equivalent 17th and 21st Ala side chains (i + 4, 8), and the second one on the equivalent 8th, 19th, and 30th Ala side chains (i + 6). The two kinds of labels are on the opposite sides of the alpha-helical AFP. A model of Ala methyl group rotation/three-site rotational jump combined with water molecular reorientation was tested to probe the interactions of the methyl groups with the proximate water molecules. Analysis of the T(1) data shows that there could be 10 water molecules closely capping an i + 4 or an i + 8 methyl group within the range of van der Waals interaction, whereas the surrounding water molecules to the i + 6 methyl groups could be looser. This study suggests that the side of the alpha-helical AFP comprising the i + 4 and i + 8 Ala methyl groups could interact with the ice surface in the ice/water interface. PMID:16648161

Mao, Yougang; Ba, Yong

2006-08-01

290

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

291

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

NASA Astrophysics Data System (ADS)

In this paper, we describe a 250 GHz gyrotron oscillator, a critical component of an integrated system for magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments at 9 T, corresponding to 380 MHz 1H frequency. The 250 GHz gyrotron is the first gyro-device designed with the goal of seamless integration with an NMR spectrometer for routine DNP enhanced NMR spectroscopy and has operated under computer control for periods of up to 21 days with a 100% duty cycle. Following a brief historical review of the field, we present studies of the membrane protein bacteriorhodopsin (bR) using DNP enhanced multidimensional NMR. These results include assignment of active site resonances in [U- 13C, 15N]-bR and demonstrate the utility of DNP for studies of membrane proteins. Next, we review the theory of gyro-devices from quantum mechanical and classical viewpoints and discuss the unique considerations that apply to gyrotron oscillators designed for DNP experiments. We then characterize the operation of the 250 GHz gyrotron in detail, including its long-term stability and controllability. We have measured the spectral purity of the gyrotron emission using both homodyne and heterodyne techniques. Radiation intensity patterns from the corrugated waveguide that delivers power to the NMR probe were measured using two new techniques to confirm pure mode content: a thermometric approach based on the temperature-dependent color of liquid crystalline media applied to a substrate and imaging with a pyroelectric camera. We next present a detailed study of the mode excitation characteristics of the gyrotron. Exploration of the operating characteristics of several fundamental modes reveals broadband continuous frequency tuning of up to 1.8 GHz as a function of the magnetic field alone, a feature that may be exploited in future tunable gyrotron designs. Oscillation of the 250 GHz gyrotron at the second harmonic of cyclotron resonance begins at extremely low beam currents (as 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.

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

292

From molecular complexes to complex metallic nanostructures--2H solid-state NMR studies of ruthenium-containing hydrogenation catalysts.  

PubMed

In the last years, the combination of (2)H solid-state NMR techniques with quantum-chemical calculations has evolved into a powerful spectroscopic tool for the characterization of the state of hydrogen on the surfaces of heterogeneous catalysts. In the present minireview, a brief summary of this development is given, in which investigations of the structure and dynamics of hydrogen in molecular complexes, clusters and nanoparticle systems are presented, aimed to understand the reaction mechanisms on the surface of hydrogenation catalysts. The surface state of deuterium/hydrogen is analyzed employing a combination of variable-temperature (2)H static and magic-angle spinning (MAS) solid-state NMR techniques, in which the dominant quadrupolar interactions of deuterium give information on the binding situation and local symmetry of deuterium/hydrogen on molecular species. Using a correlation database from molecular complexes and clusters, the possibility to distinguish between terminal Ru-D, bridged Ru2-D, three-fold Ru3-D, and interstitial Ru6-D is demonstrated. Combining these results with quantum-chemical density functional theory (DFT) calculations allows the interpretation of (2)H solid-state data of complex "real world" nanostructures, which yielded new insights into reaction pathways at the molecular level. PMID:23658058

Gutmann, Torsten; del Rosal, Iker; Chaudret, Bruno; Poteau, Romuald; Limbach, Hans-Heinrich; Buntkowsky, Gerd

2013-09-16

293

Solid-state 23Na and 7Li NMR investigations of sodium- and lithium-reduced mesoporous titanium oxides.  

PubMed

Mesoporous titanium oxide synthesized using a dodecylamine template was treated with 0.2, 0.6, and 1.0 equiv of Li- or Na-naphthalene. The composite materials were characterized by nitrogen adsorption, powder X-ray diffraction, X-ray photoelectron spectroscopy, elemental analysis, thermogravimetric analysis, and solid-state 23Na and 7Li NMR spectroscopy. In all cases the wormhole mesoporosity was retained as evidenced by BET surface areas from 400 to 700 m(2)/g, Horvath-Kawazoe pore sizes in the 20 Angstroms range, and a lack of hysteresis in the nitrogen adsorption isotherms. Variable-temperature conductivity studies show that the Li-reduced materials are semiconductors, with conductivity values 3 orders of magnitude higher than those of the Na-reduced materials. Electrochemical measurements demonstrate reversible intercalation/deintercalation of Li+ ions into pristine mesoporous Ti oxides with good cycling capacity. Solid-state 23Na NMR reveals two distinct Na environments: one corresponding to sodium ions in the mesoporous channels and the other corresponding to sodium ions intercalated into the metal framework. 23Na NMR spectra also indicate that the relative population of the framework site increases with increased reduction levels. Solid-state 7Li NMR spectra display a single broad resonance, which increases in breadth with increased reduction levels, though individual resonances inferring the presence of channel and framework Li species are not resolved. Comparisons of the lithium chemical shifts with published values suggests an "anatase-like structure" with no long-range order in the least-reduced samples but a "lithium titanate-like structure" with no long-range order in the higher reduced materials. PMID:16472000

Lo, Andy Y H; Schurko, Robert W; Vettraino, Melissa; Skadtchenko, Boris O; Trudeau, Michel; Antonelli, David M

2006-02-20

294

A high-resolution sup 13 C solid-state NMR study of meso-tetraphenylporphyrin and its zinc(II) complex  

SciTech Connect

High-resolution {sup 13}C solid-state NMR spectra of meso-tetraphenylporphyrin (TPP) and its zinc(II) complex (ZnTPP) are assigned by reference to low-temperature solution NMR results and using {sup 1}H- {sup 13}C cross-polarization magic-angle-spinning (CP/MAS). The splittings of the signals from pyrrole carbons in TPP are attributed to kinetic solid-state states involved in the migration of the central hydrogen atom.

Rocha, J.; Kolodziejski, W.; Klinowski, J. (Univ. of Cambridge (United Kingdom)); Cavaleiro, J.A.S. (Univ. of Aveiro (Portugal))

1992-01-01

295

Morphology and side-chain dynamics in hydrated hard ?-keratin fibres by 1H solid-state NMR  

NASA Astrophysics Data System (ADS)

The effect of hydration on phase composition, aminoacids side-chain dynamics, and domain thickness of hard ?-keratin was investigated by 1H solid-state NMR. Decomposition of wide-line 1H NMR spectra was used to determine the phase composition and to obtain information on molecular motion. Proton spin-diffusion NMR experiments using a double-quantum dipolar filter were used to estimate the rigid domain sizes for the hydrated Caucasian hair fibres. The relative domain sizes were obtained from the solution of spin-diffusion equation for cylindrical morphologies in the initial-rate approximation by a novel approach. A qualitative model describing the morphological and molecular dynamics changes induced by hydration was developed.

Melian, Claudiu; Demco, Dan E.; Istrate, Monica; Balaceanu, Andreea; Moldovan, Dumitrita; Fechete, Radu; Popescu, Crisan; Möller, Martin

2009-10-01

296

Ultra-high resolution in MAS solid-state NMR of perdeuterated proteins: Implications for structure and dynamics  

NASA Astrophysics Data System (ADS)

High resolution proton spectra are obtained in MAS solid-state NMR in case samples are prepared using perdeuterated protein and D2O in the recrystallization buffer. Deuteration reduces drastically 1H, 1H dipolar interactions and allows to obtain amide proton line widths on the order of 20 Hz. Similarly, high-resolution proton spectra of aliphatic groups can be obtained if specifically labeled precursors for biosynthesis of methyl containing side chains are used, or if limited amounts of H2O in the bacterial growth medium is employed. This review summarizes recent spectroscopic developments to access structure and dynamics of biomacromolecules in the solid-state, and shows a number of applications to amyloid fibrils and membrane proteins.

Reif, Bernd

2012-03-01

297

Solid-state 129Xe and 131Xe NMR study of the perxenate anion XeO(6)4-.  

PubMed

Results of the first solid-state 131Xe NMR study of xenon-containing compounds are presented. The two NMR-active isotopes of xenon, 129Xe (I=1/2) and 131Xe (I=3/2), are exploited to characterize the xenon magnetic shielding and quadrupolar interactions for two sodium perxenate salts, Na4XeO6.xH2O (x=0, 2), at an applied magnetic field strength of 11.75 T. Solid-state 129/131Xe NMR line shapes indicate that the local xenon environment in anhydrous Na4XeO6 adopts octahedral symmetry, but upon hydration, the XeO6(4-) anion becomes noticeably distorted from octahedral symmetry. For stationary, anhydrous samples of Na4XeO6, the heteronuclear 129/131Xe-23Na dipolar interaction is the principal contributor to the breadth of the 129/131Xe NMR lines. For stationary and slow magic-angle-spinning samples of Na4XeO(6).2H2O, the anisotropic xenon shielding interaction dominates the 129Xe NMR line shape, whereas the 131Xe NMR line shape is completely dominated by the nuclear quadrupolar interaction. The xenon shielding tensor is approximately axially symmetric, with a skew of -0.7+/-0.3, an isotropic xenon chemical shift of -725.6+/-1.0 ppm, and a span of 95+/-5 ppm. The 131Xe quadrupolar coupling constant, 10.8+/-0.5 MHz, is large for a nucleus at a site of approximate Oh symmetry, and the quadrupolar asymmetry parameter indicates a lack of axial symmetry. This study demonstrates the extreme sensitivity of the 131Xe nuclear quadrupolar interaction to changes in the local xenon environment. PMID:17385852

Forgeron, Michelle A M; Wasylishen, Roderick E; Gerken, Michael; Schrobilgen, Gary J

2007-04-30

298

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

NASA Astrophysics Data System (ADS)

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 CH 3, CH 2, 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.

Mao, Jingdong; Fang, Xiaowen; Lan, Yeqing; Schimmelmann, Arndt; Mastalerz, Maria; Xu, Ling; Schmidt-Rohr, Klaus

2010-04-01

299

Hydration-optimized oriented phospholipid bilayer samples for solid-state NMR structural studies of membrane proteins  

Microsoft Academic Search

The preparation of oriented, hydration-optimized lipid bilayer samples, for NMR structure determination of membrane proteins, is described. The samples consist of planar phospholipid bilayers, containing membrane proteins, that are oriented on single pairs of glass slides, and are placed in the coil of the NMR probe with the bilayer plane perpendicular to the direction of the magnetic field. Lipid bilayers

Francesca M. Marassi; Kevin J. Crowell

2003-01-01

300

Protonation, Tautomerization, and Rotameric Structure of Histidine: A Comprehensive Study by Magic-Angle-Spinning Solid-State NMR  

PubMed Central

Histidine structure and chemistry lie at the heart of many enzyme active sites, ion channels, and metalloproteins. While solid-state NMR spectroscopy has been used to study histidine chemical shifts, the full pH dependence of the complete panel of 15N, 13C, and 1H chemical shifts and the sensitivity of these chemical shifts to tautomeric structure have not been reported. Here we use magic-angle-spinning solid-state NMR spectroscopy to determine the 15N, 13C, and 1H chemical shifts of histidine from pH 4.5 to 11. Two-dimensional homonuclear and heteronuclear correlation spectra indicate that these chemical shifts depend sensitively on the protonation state and tautomeric structure. The chemical shifts of the rare ? tautomer were observed for the first time, at the most basic pH used. Intra- and intermolecular hydrogen bonding between the imidazole nitrogens and the histidine backbone or water was detected, and N–H bond length measurements indicated the strength of the hydrogen bond. We also demonstrate the accurate measurement of the histidine side-chain torsion angles ?1 and ?2 through backbone–side chain 13C–15N distances; the resulting torsion angles were within 4° of the crystal structure values. These results provide a comprehensive set of benchmark values for NMR parameters of histidine over a wide pH range and should facilitate the study of functionally important histidines in proteins.

Li, Shenhui; Hong, Mei

2014-01-01

301

Conformational analysis of steroid hormone molecules in the lipid environment--a solid-state NMR approach.  

PubMed

Solid-state (1)H/(13)C cross-polarization/magic angle spinning (CP/MAS) NMR spectroscopy has been applied to two steroid compounds: dehydroepiandrosterone (DHEA) and spironolactone (SPI), to analyze their conformations at the atomic level. In the absence of lipid, the high-resolution (13)C CP/MAS NMR signals of DHEA and SPI in a powder form reveal multiple patterns, with splittings of 30-160 Hz, indicating the existence of multiple conformations. In the mimic lipid environment formed by mixing 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-diheptanoyl-sn-glycero-3-phosphocholine (DHPC) in a molar ratio 3:1, the resulting DHEA and SPI spectra revealed mostly singlet patterns, suggesting that these steroids undergo a conformational change leading to a specific conformation in the lipid environment. Evidence from chemical shift isotropy and anisotropy analysis indicates that DHEA might adopt conformations subtly different from that seen in solution and in the powder form. In conclusion, we demonstrate by solid-state NMR that the structures of DHEA and SPI may adopt slightly different conformations in different chemical environments. PMID:21335019

Shih, Ping-Chen; Li, Guo-Chian; Yang, Kai-Jay; Chen, Wenlung; Tzou, Der-Lii M

2011-05-01

302

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.

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

2000-01-01

303

3D DUMAS: Simultaneous Acquisition of Three-Dimensional Magic Angle Spinning Solid-State NMR Experiments of Proteins  

PubMed Central

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

2012-01-01

304

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

PubMed

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 (13)C, (15)N labeled proteins. These new experiments exploit the simultaneous cross-polarization (SIM-CP) from (1)H to (13)C and (15)N to acquire two 3D experiments simultaneously. This is made possible by bidirectional polarization transfer between (13)C and (15)N and the long living (15)N 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-(13)C,(15)N ubiquitin. The DUMAS approach is general and applicable to many 3D experiments, nearly doubling the performance of NMR spectrometers. PMID:22698806

Gopinath, T; Veglia, Gianluigi

2012-07-01

305

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

306

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

307

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

Microsoft Academic Search

This paper details a way to produce azurin with an effi ciency over 10 times greater than previously described and demonstrates the fi rst solid state nuclear magnetic resonance spectrum of 65 Cu(I) in a metalloprotein. A synthetic gene for azurin based upon the DNA sequence from Pseudomonas aeruginosa including the periplasmic targeting sequence was subcloned into a T7 overexpression

AMY GAO; ROBERT W. HECK

308

Destabilization of cationic lipid vesicles by an anionic hydrophobically modified poly( N-isopropylacrylamide) copolymer: a solid-state 31P NMR and 2H NMR study  

Microsoft Academic Search

The effect of binding PNIPAM–Py–Gly, a copolymer of N-isopropylacrylamide, N-[4-(1-pyrenyl)butyl]-N-n-octadecylacrylamide and N-glycydyl-acrylamide, on membrane stability in cationic multilamellar vesicles (MLVs) was examined using solid-state phosphorus (31P) and deuterium (2H) nuclear magnetic resonance (NMR) spectroscopy. For MLVs of composition n-octadecyldiethylene oxide (ODEO)+cholesterol (CHOL)+1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)+dimethyldioctadecylammonium bromide (DODAB) (molar ratios 75:10.5:10.5:4), PNIPAM–Py–Gly induced a complete conversion from a bilayer-type 31P NMR spectrum to

Carla M. Franzin; Peter M. Macdonald; Alla Polozova; Françoise M. Winnik

1998-01-01

309

Supramolecular Structure of Membrane-Associated Polypeptides by Combining Solid-State NMR and Molecular Dynamics Simulations  

PubMed Central

Elemental biological functions such as molecular signal transduction are determined by the dynamic interplay between polypeptides and the membrane environment. Determining such supramolecular arrangements poses a significant challenge for classical structural biology methods. We introduce an iterative approach that combines magic-angle spinning solid-state NMR spectroscopy and atomistic molecular dynamics simulations for the determination of the structure and topology of membrane-bound systems with a resolution and level of accuracy difficult to obtain by either method alone. Our study focuses on the Shaker B ball peptide that is representative for rapid N-type inactivating domains of voltage-gated K+ channels, associated with negatively charged lipid bilayers.

Weingarth, Markus; Ader, Christian; Melquiond, Adrien J.S.; Nand, Deepak; Pongs, Olaf; Becker, Stefan; Bonvin, Alexandre M.J.J.; Baldus, Marc

2012-01-01

310

Proton Clouds to Measure Long-Range Contacts between Nonexchangeable Side Chain Protons in Solid-State NMR.  

PubMed

We show that selective labeling of proteins with protonated amino acids embedded in a perdeuterated matrix, dubbed 'proton clouds', provides general access to long-range contacts between nonexchangeable side chain protons in proton-detected solid-state NMR, which is important to study protein tertiary structure. Proton-cloud labeling significantly improves spectral resolution by simultaneously reducing proton line width and spectral crowding despite a high local proton density in clouds. The approach is amenable to almost all canonical amino acids. Our method is demonstrated on ubiquitin and the ?-barrel membrane protein BamA. PMID:24467345

Sinnige, Tessa; Daniëls, Mark; Baldus, Marc; Weingarth, Markus

2014-03-26

311

Local structure of hydroxy peroxy apatite: A combined XRD, FT-IR, Raman, SEM, and solid-state NMR study  

NASA Astrophysics Data System (ADS)

The synthesized hydroxyapatite (HAp) and hydroxy peroxy apatite are studied using various techniques, such as X-ray powder diffraction, FT-IR and Raman spectroscopy, scanning electron microscopy, and solid-state NMR spectroscopy. The experimental data suggest that hydroxy peroxy apatite contains a small amount of hydration of partially dehydroxylated hydroxyapatite phase and calcium hydroxide. The incorporation of peroxide ions into the lattice of HAp causes perturbations of the hydrogen environments and slight changes in its crystal morphology. The distance between H in some structural OH- and adjacent O along the c-axis becomes longer instead of forming a hydrogen bond after the incorporation of peroxide ions.

Yu, Huaguang; Zhang, Hailu; Wang, Xiaomin; Gu, Zhongwei; Li, Xudong; Deng, Feng

2007-10-01

312

Dipolar Assisted Assignment Protocol (DAAP) for MAS solid-state NMR of rotationally aligned membrane proteins in phospholipid bilayers  

NASA Astrophysics Data System (ADS)

A method for making resonance assignments in magic angle spinning solid-state NMR spectra of membrane proteins that utilizes the range of heteronuclear dipolar coupling frequencies in combination with conventional chemical shift based assignment methods is demonstrated. The Dipolar Assisted Assignment Protocol (DAAP) takes advantage of the rotational alignment of the membrane proteins in liquid crystalline phospholipid bilayers. Improved resolution is obtained by combining the magnetically inequivalent heteronuclear dipolar frequencies with isotropic chemical shift frequencies. Spectra with both dipolar and chemical shift frequency axes assist with resonance assignments. DAAP can be readily extended to three- and four-dimensional experiments and to include both backbone and side chain sites in proteins.

Das, Bibhuti B.; Zhang, Hua; Opella, Stanley J.

2014-05-01

313

Structure analysis of membrane-reconstituted subunit c -ring of E. coli H + ATP synthase by solid-state NMR  

Microsoft Academic Search

The subunit c-ring of H+-ATP synthase (Fo\\u000a c-ring) plays an essential role in the proton translocation across a membrane driven by the electrochemical potential. To understand\\u000a its structure and function, we have carried out solid-state NMR analysis under magic-angle sample spinning. The uniformly\\u000a [13C, 15N]-labeled Fo\\u000a c from E. coli (EFo\\u000a c) was reconstituted into lipid membranes as oligomers. Its

Yasuto Todokoro; Masatoshi Kobayashi; Takeshi Sato; Toru Kawakami; Ikuko Yumen; Saburo Aimoto; Toshimichi Fujiwara; Hideo Akutsu

2010-01-01

314

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

315

Applications of the Bloch–Siegert Shift in Solid-State Proton-Dipolar-Decoupled 19F MAS NMR  

Microsoft Academic Search

In solid-state proton-dipolar-decoupled19F MAS NMR spectroscopy,19F chemical-shift data need to be corrected for the Bloch–Siegert shift. Assigning the single sharp19F resonance of 2-fluoroadamantane to its proton-coupled19F shift of ?174.4 ppm results in chemical-shift referencing that is independent of the amplitude of the proton-decoupling field. The Bloch–Siegert shift is also a useful tool to characterize the amplitude and homogeneity of the

Stephanie A. Vierkötter

1996-01-01

316

Toward a structure determination method for biomineral-associated protein using combined solid-state NMR and computational structure prediction  

PubMed Central

Summary Protein-biomineral interactions are paramount to materials production in biology, including the mineral phase of hard tissue. Unfortunately, the structure of biomineral-associated proteins cannot be determined by X-ray crystallography or solution NMR. Here we report a method for determining the structure of biomineral-associated proteins. The method combines solid-state NMR (ssNMR) and ssNMR-biased computational structure prediction. In addition, the algorithm is able to identify lattice geometries most compatible with ssNMR constraints, representing a quantitative, novel method for investigating crystal-face binding specificity. We use this new method to determine most of the structure of human salivary statherin interacting with the mineral phase of tooth enamel. Computation and experiment converge on an ensemble of related structures and identify preferential binding at three crystal surfaces. The work represents a significant advance toward determining structure of biomineral-adsorbed protein using experimentally biased structure prediction. This method is generally applicable to proteins that can be chemically synthesized.

Masica, David L.; Ash, Jason T.; Ndao, Moise; Drobny, Gary P.; Gray, Jeffrey J

2010-01-01

317

Variable-temperature, solid-state NMR studies of bonded liquid crystal stationary phases for HPLC  

Microsoft Academic Search

Summary  The spin-spin relaxation time measured from the line width (T\\u000a 2*) is used to study bonded phase dynamics of two liquid crystal materials in the solid state as a function of temperature.\\u000a The motion of these two bonded phases is much more restricted than either C-18 or butyl phenyl bonded to the same substrate.\\u000a Plots ofT\\u000a 2* vs. 1\\/T indicate

Joseph J. Pesek; M. T. Matyska; E. J. Williamser; R. Tam

1995-01-01

318

Synthesis and Solid-State NMR Structural Characterization of 13C-Labeled Graphite Oxide  

Microsoft Academic Search

The detailed chemical structure of graphite oxide (GO), a layered material prepared from graphite almost 150 years ago and a precursor to chemically modified graphenes, has not been previously resolved because of the pseudo-random chemical functionalization of each layer, as well as variations in exact composition. Carbon-13 (13C) solid-state nuclear magnetic resonance (SSNMR) spectra of GO for natural abundance 13C

Weiwei Cai; Richard D. Piner; Frank J. Stadermann; Sungjin Park; Medhat A. Shaibat; Yoshitaka Ishii; Dongxing Yang; Aruna Velamakanni; Sung Jin An; Meryl Stoller; Jinho An; Dongmin Chen; Rodney S. Ruoff

2008-01-01

319

Electrochemical and solid state NMR characterization of composite PEO-based polymer electrolytes  

Microsoft Academic Search

A comprehensive matrix of composite poly(ethyleneoxide) (PEO)-based solid-state electrolytes was developed in order to systematically study a number of variables and their impact upon the electrochemical properties of the resulting materials. The different parameters studied in the fabrication of these materials include: (i) the lithium electrolyte salt type, (ii) the ether oxygen to lithium ratio, (iii) the molecular weight of

I. W. Cheung; K. B. Chin; E. R. Greene; M. C. Smart; S. Abbrent; S. G. Greenbaum; G. K. S. Prakash; S. Surampudi

2003-01-01

320

Structural Evolution and Li Dynamics in Nanophase Li3PS4 by Solid-State and Pulsed Field Gradient NMR  

SciTech Connect

The ceramic lithium ion conductor -Li3PS4 has a disordered and nanoporous structure that leads to an enhancement in ionic conductivity by some three orders of magnitude compared to the crystalline phase. The phase is prepared by thermal treatment of an inorganic-organic complex based on Li3PS4 and THF. Multinuclear (1H, 6,7Li, 31P) solid state NMR spectroscopy is used to characterize the structural phase evolution of the starting material at various steps in the thermal treatment. The phase formed after high temperature treatment is recognized as spectroscopically distinct from the bulk -Li3PS4 compound. Also formed is an amorphous lithium thiophosphate phase that is metastable as verified by annealing over an extended period. Lithium ion self-diffusion coefficients are measurable by standard pulsed gradient NMR methods at 100oC and with values consistent with the high ionic conductivity previously reported for this material.

Gobet, Mallory [Hunter College of the City University of New York] [Hunter College of the City University of New York; Greenbaum, Steve [Hunter College of the City University of New York] [Hunter College of the City University of New York; Sahu, Gayatri [ORNL] [ORNL; Liang, Chengdu [ORNL] [ORNL

2014-01-01

321

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

322

Grid-free powder averages: On the applications of the Fokker-Planck equation to solid state NMR  

NASA Astrophysics Data System (ADS)

We demonstrate that Fokker-Planck equations in which spatial coordinates are treated on the same conceptual level as spin coordinates yield a convenient formalism for treating magic angle spinning NMR experiments. In particular, time dependence disappears from the background Hamiltonian (sample spinning is treated as an interaction), spherical quadrature grids are avoided completely (coordinate distributions are a part of the formalism) and relaxation theory with any linear diffusion operator is easily adopted from the Stochastic Liouville Equation theory. The proposed formalism contains Floquet theory as a special case. The elimination of the spherical averaging grid comes at the cost of increased matrix dimensions, but we show that this can be mitigated by the use of state space restriction and tensor train techniques. It is also demonstrated that low correlation order basis sets apparently give accurate answers in powder-averaged MAS simulations, meaning that polynomially scaling simulation algorithms do exist for a large class of solid state NMR experiments.

Edwards, Luke J.; Savostyanov, D. V.; Nevzorov, A. A.; Concistrè, M.; Pileio, G.; Kuprov, Ilya

2013-10-01

323

Grid-free powder averages: on the applications of the Fokker-Planck equation to solid state NMR.  

PubMed

We demonstrate that Fokker-Planck equations in which spatial coordinates are treated on the same conceptual level as spin coordinates yield a convenient formalism for treating magic angle spinning NMR experiments. In particular, time dependence disappears from the background Hamiltonian (sample spinning is treated as an interaction), spherical quadrature grids are avoided completely (coordinate distributions are a part of the formalism) and relaxation theory with any linear diffusion operator is easily adopted from the Stochastic Liouville Equation theory. The proposed formalism contains Floquet theory as a special case. The elimination of the spherical averaging grid comes at the cost of increased matrix dimensions, but we show that this can be mitigated by the use of state space restriction and tensor train techniques. It is also demonstrated that low correlation order basis sets apparently give accurate answers in powder-averaged MAS simulations, meaning that polynomially scaling simulation algorithms do exist for a large class of solid state NMR experiments. PMID:23942141

Edwards, Luke J; Savostyanov, D V; Nevzorov, A A; Concistrè, M; Pileio, G; Kuprov, Ilya

2013-10-01

324

Determination of the charge on carbon in a bridging methylene iron dimer with solid-state deuterium NMR spectroscopy  

SciTech Connect

The chemistry of bridging methylene metal dimers and the value of the /sup 13/C NMR chemical shifts have been interpreted as due to a partial negative charge on the carbon atom. PES yields a C/sub 1s/ binding energy indicative of -0.5 e charge. However, for (..mu..-CH/sub 2/)(MnCp(CO)/sub 2/)/sub 2/, a high-resolution x-ray diffraction electron density map shows no excess charge buildup. The authors are attempting to resolve the dilemma by using solid-state deuterium NMR techniques. In the results for cis-(..mu..-C/sup 2/H/sub 2/)(..sigma..-CO)(FeCp/sup d/(CO))/sub 2/ (Cp/sup d/ and 5% deuteriated cyclopentadienyl) presented here, the authors find no evidence for an excess negative charge on the bridging methylene carbon atom.

Altbach, M.I.; Hiyama, Y.; Gerson, D.J.; Butler, L.G.

1987-09-02

325

?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

326

Comparison of sorption domains in molecular weight fractions of a soil humic acid using solid-state 19F NMR.  

PubMed

Humic acid was fractionated into eight different molecular size components using ultrafiltration. Solid-state CPMAS 13C NMR demonstrated that fractions larger than 100,000 Daltons were primarily aliphatic in character, while fractions smaller than 30,000 Daltons were predominantly aromatic in character. Solid-state 19F NMR examination of the sorptive uptake of hexafluorobenzene (HFB) by HA and each of the fractions gave spectroscopic evidence for the existence of at least three sorption sites in the smaller molecular size fractions, while two predominant sorption sites could be established in the larger molecular size fractions. Sorbed HFB displayed higher mobility in the smaller, more aromatic fractions while HFB in the larger, more aliphatic fractions displayed lower mobility. The relative mobilities of HFB in each sorption domain suggest that the rigid domain may be composed of aliphatic carbon rather than aromatic carbon moieties. In larger size fractions, this domain may be the result of rigid, glassy regions composed of aliphatic molecules or side chains. PMID:12875386

Khalaf, M; Kohl, Scott D; Klumpp, E; Rice, James A; Tombácz, E

2003-07-01

327

Solid state NMR studies of oligourea foldamers: interaction of 15N-labelled amphiphilic helices with oriented lipid membranes.  

PubMed

Synthetic oligomers that are derived from natural polypeptide sequences, albeit with unnatural building blocks, have attracted considerable interest in mimicking bioactive peptides and proteins. Many of those compounds adopt stable folds in aqueous environments that resemble protein structural elements. Here we have chemically prepared aliphatic oligoureas and labeled them at selected positions with (15)N for structural investigations using solid-state NMR spectroscopy. In the first step, the main tensor elements and the molecular alignment of the (15)N chemical shift tensor were analyzed. This was possible by using a two-dimensional heteronuclear chemical shift/dipolar coupling correlation experiment on a model compound that represents the chemical, and thereby also the chemical shift characteristics, of the urea bond. In the next step (15)N labeled versions of an amphipathic oligourea, that exert potent antimicrobial activities and that adopt stable helical structures in aqueous environments, were prepared. These compounds were reconstituted into oriented phospholipid bilayers and the (15)N chemical shift and (1)H-(15)N dipolar couplings of two labeled sites were determined by solid-state NMR spectroscopy. The data are indicative of an alignment of this helix parallel to the membrane surface in excellent agreement with the amphipathic character of the foldamer and consistent with previous models explaining the antimicrobial activities of ?-peptides. PMID:22218372

Aisenbrey, Christopher; Pendem, Nagendar; Guichard, Gilles; Bechinger, Burkhard

2012-02-21

328

The binding site of sodium in the gramicidin A channel: comparison of molecular dynamics with solid-state NMR data.  

PubMed Central

The location of the main binding site for sodium in the gramicidin A (GA) channel was investigated with molecular dynamics simulations, using an atomic model of the channel embedded in a fully hydrated dimyristoyl phosphatidycholine (DMPC) bilayer. Twenty-four separate simulations in which a sodium was restrained at different locations along the channel axis were generated. The results are compared with carbonyl 13C chemical shift anisotropy solid-state NMR experimental data previously obtained with oriented GA:DMPC samples. Predictions are made for other solid-state NMR properties that could be observed experimentally. The combined information from experiment and simulation strongly suggests that the main binding sites for sodium are near the channel's mouth, approximately 9.2 A from the center of the dimer channel. The 13C chemical shift anisotropy of Leu10 is the most affected by the presence of a sodium ion in the binding site. In the binding site, the sodium ion is lying off-axis, making contact with two carbonyl oxygens and two single-file water molecules. The main channel ligand is provided by the carbonyl group of the Leu10-Trp11 peptide linkage, which exhibits the largest deviation from the ion-free channel structure. Transient contacts with the carbonyl group of Val8 and Trp15 are also present. The influence of the tryptophan side chains on the channel conductance is examined based on the current information about the binding site. Images FIGURE 1 FIGURE 7

Woolf, T B; Roux, B

1997-01-01

329

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

330

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

331

Preparation of uniformly (13)C,(15)N-labeled recombinant human amylin for solid-state NMR investigation.  

PubMed

A number of diseases are caused by the formation of amyloid fibrils. Detailed understanding of structural features of amyloid fibers is of great importance for our understanding of disease progression and design of agents for diagnostics or potential prevention of protein aggregation. In lack of 3D crystal ordering, solid-state NMR forms the most suited method to determine the structures of the fibrils with atomic resolution. To exploit this potential, large amounts of isotopic-labeled protein need to be obtained through recombinant protein expression. However, expression and purification of amyloidogenic proteins in large amounts remains challenging due to their aggregation potential, toxicity for cells and difficult purification. In this work, we report a method for the production of large amounts of uniformly labeled (13)C,(15)N-human amylin, being one of the most amyloidogenic peptides known. This method utilizes inclusion bodies-directed expression and cheap chemical cleavage with cyanogen bromide in order to minimize the cost of the procedure compared to the use of less efficient proteolytic enzymes. We demonstrate the formation of amylin fibrils in vitro characterized using biophysical methods and electron microscopy, show toxicity towards human cells, and demonstrate that produced material may form the basis for structure determination using solid-state NMR. PMID:24751876

Kosicka, Iga; Kristensen, Torsten; Bjerring, Morten; Thomsen, Karen; Scavenius, Carsten; Enghild, Jan J; Nielsen, Niels Chr

2014-07-01

332

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

Microsoft Academic Search

In this paper, we describe a 250 GHz gyrotron oscillator, a critical component of an integrated system for magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments at 9 T, corresponding to 380 MHz 1H frequency. The 250 GHz gyrotron is the first gyro-device designed with the goal of seamless integration with an NMR spectrometer for routine DNP enhanced NMR

Vikram S. Bajaj; Melissa K. Hornstein; Kenneth E. Kreischer; Jagadishwar R. Sirigiri; Paul P. Woskov; Melody L. Mak-Jurkauskas; Judith Herzfeld; Richard J. Temkin; Robert G. Griffin

2007-01-01

333

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

Microsoft Academic Search

In this paper, we describe a 250 {GHz} gyrotron oscillator, a critical component of an integrated system for magic angle spinning {(MAS)} dynamic nuclear polarization {(DNP)} experiments at 9 T, corresponding to 380 {MHz} {1H} frequency. The 250 {GHz} gyrotron is the first gyro-device designed with the goal of seamless integration with an {NMR} spectrometer for routine {DNP} enhanced {NMR}

Vikram S. Bajaj; Melissa K. Hornstein; Kenneth E. Kreischer; Jagadishwar R. Sirigiri; Paul P. Woskov; Melody L. Mak-Jurkauskas; Judith Herzfeld; Richard J. Temkin; Robert G. Griffin

2007-01-01

334

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.

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

2009-01-01

335

Solid-state and multidimensional solution-state NMR of solid phase extracted and ultrafiltered riverine dissolved organic matter.  

PubMed

In this study we used multidimensional solution-state NMR to elucidate the differences in the chemical composition of solid phase extracted and ultrafiltered DOM isolates. DOM was isolated from water sampled from an oligotrophic river, the River Tagliamento (Italy). The recovery of total DOM was up to 42% with both isolation techniques. In addition to 1- and 2-D solution-state NMR, we also applied 1-D solid-state 13C NMR spectroscopy for DOM characterization. 13C NMR spectroscopy only produced broad overlapping resonances, thus allowing a bulk characterization of DOM composition. However, it demonstrated that the bulk chemical composition of the two DOM fractions exhibited minor spatial-temporal changes. The 2-D experiments (TOCSY, HMQC) showed that the solid phase extracted hydrophobic DOM contained predominantly aliphatic esters, ethers, and hydroxyl groups, whereas the ultrafiltered DOM was comprised partially of peptides/protein, with further evidence for a small amount of aliphatic/fatty acid material. Sugars were present in both DOM fractions. The results show the two isolation techniques selected for different suites of compounds within the bulk DOM pool. PMID:12875396

Kaiser, Edith; Simpson, Andre J; Dria, Karl J; Sulzberger, Barbara; Hatcher, Patrick G

2003-07-01

336

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.

Bardiaux, Benjamin; Favier, Adrien; Etzkorn, Manuel; Baldus, Marc; Bockmann, Anja; Nilges, Michael; Malliavin, Therese E

2010-01-01

337

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

PubMed

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 TE(13) fundamental mode of the FU CW VII gyrotron is used as the microwave source for this magnetic field strength and 284 MHz (1)H DNP-NMR. The spectrometer is designed for use with microwave frequencies up to 395 GHz (the TE(16) second-harmonic mode of the gyrotron) for DNP at 14.1T (600 MHz (1)H 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 (1)H and double channel HX mode for 284 MHz (1)H, with MAS sample temperatures ?85 K. Initial data at 6.7 T and ~1 W pulsed microwave power are presented with (13)C enhancements of 60 for a frozen urea solution ((1)H-(13)C CP), 16 for bacteriorhodopsin in purple membrane ((1)H-(13)C CP) and 22 for (15)N in a frozen glycine solution ((1)H-(15)N 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. PMID:22218011

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

338

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

339

Observation of a low-temperature, dynamically driven structural transition in a polypeptide by solid-state NMR spectroscopy.  

PubMed

At reduced temperatures, proteins and other biomolecules are generally found to exhibit dynamic as well as structural transitions. This includes a so-called protein glass transition that is universally observed in systems cooled between 200 and 230 K, and which is generally attributed to interactions between hydrating solvent molecules and protein side chains. However, there is also experimental and theoretical evidence for a low-temperature transition in the intrinsic dynamics of the protein itself, absent any solvent. Here, we use low-temperature solid-state NMR to examine site-specific fluctuations in atomic structure and dynamics in the absence of solvents. In particular, we employ magic angle spinning NMR to examine a structural phase transition associated with dynamic processes in a solvent-free polypeptide, N-f-MLF-OH, lattice at temperatures as low as 90 K. This transition is characterized by the appearance of an extra set of lines in 1D (15)N spectra as well as additional cross peaks in 2D (13)C-(13)C and (13)C-(15)N spectra. Interestingly, the gradual, temperature-dependent appearance of the new spectral component is not accompanied by the line broadening typical of dynamic transitions. A direct comparison between the spectra of N-f-MLF-OH and the analog N-f-MLF-OMe, which does not display this transition, indicates a correlation of the structural transition to the temperature dependent motion of the aromatic phenylalanine side chain. Several quantitative solid state NMR experiments were employed to provide site-specific measurements of structural and motional features of the observed transition. PMID:19067520

Bajaj, Vikram S; van der Wel, Patrick C A; Griffin, Robert G

2009-01-14

340

Observation of a Low-Temperature, Dynamically Driven, Structural Transition in a Polypeptide by Solid State NMR Spectroscopy  

PubMed Central

At reduced temperatures, proteins and other biomolecules are generally found to exhibit dynamic as well as structural transitions. This includes a so-called protein glass transition that is universally observed in systems cooled between 200–230K, and which is generally attributed to interactions between hydrating solvent molecules and protein side chains. However, there is also experimental and theoretical evidence for a low-temperature transition in the intrinsic dynamics of the protein itself, absent any solvent. Here, we use low-temperature solid state NMR to examine site specific fluctuations in atomic structure and dynamics in the absence of solvents. In particular, we employ magic angle spinning NMR to examine a structural phase transition associated with dynamic processes in a solvent-free polypeptide, N-f-MLF-OH, lattice at temperatures as low as 90K. This transition is characterized by the appearance of an extra set of lines in 1D 15N spectra as well as additional cross peaks in 2D 13C-13C and 13C-15N spectra. Interestingly, the gradual, temperature-dependent appearance of the new spectral component is not accompanied by the line broadening typical of dynamic transitions. A direct comparison between the spectra of N-f-MLF-OH and the analog N-f-MLF-OMe, which does not display this transition, indicates a correlation of the structural transition to the temperature dependent motion of the aromatic phenylalanine side chain. Several quantitative solid state NMR experiments were employed to provide site-specific measurements of structural and motional features of the observed transition.

Bajaj, Vikram S.; van der Wel, Patrick C.A.; Griffin, Robert G.

2009-01-01

341

Exploring electrolyte organization in supercapacitor electrodes with solid-state NMR  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

342

Solid-state NMR and computational studies of tetratolyl urea calix[4]arene inclusion compounds.  

PubMed

Solid-state guest dynamics of tetratolyl tetraurea calix[4]arene tetrapentylether dimeric capsules filled with different types of aromatic guests such as benzene-d6, fluorobenzene-d5 and 1,4-difluorobenzene were studied. Upon inclusion, all guest moieties revealed complexation-induced shifts varying from 2.8 ppm to 5.1 ppm. All guest molecules were shown to undergo distinct motions, ranging from mere C6-rotations of benzene-d6 to (ill-defined) 180 degrees phenyl flips of fluorobenzene-d5. In all cases, dynamic heterogeneities were identified based on 2H lineshape deconvolution. In addition, by combination of both a computed nucleus independent chemical shift (NICS) map and explicit 19F and 2H ab initio DFT chemical shift calculations, the preferred orientation of the guest molecules within the host was derived. PMID:19812845

Moon, Chulsoon; Brunklaus, Gunther; Sebastiani, Daniel; Rudzevich, Yuliya; Böhmer, Volker; Spiess, Hans Wolfgang

2009-10-28

343

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

PubMed

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 (1)H T1 values were calculated from data collected by (1)H spin-inversion recovery method detected in natural-abundance (13)C cross-polarization magic angle spinning (CPMAS) NMR experiments. Our results reveal that the (1)H T1 values can be successfully reduced by a factor of 3.5 using as low as 10mM Gd-DTPA without reducing the spectral resolution and thus enabling faster data acquisition of the (13)C CPMAS spectra. These results obtained from (13)C-detected CPMAS experiments were further confirmed using (1)H-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. PMID:24881032

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

2014-07-01

344

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

345

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

NASA Astrophysics Data System (ADS)

We describe the synthesis of new nitroxide-based biradical, triradical, and tetraradical compounds and the evaluation of their performance as paramagnetic dopants in dynamic nuclear polarization (DNP) experiments in solid state nuclear magnetic resonance (NMR) spectroscopy with magic-angle spinning (MAS). Under our experimental conditions, which include temperatures in the 25-30 K range, a 9.4 T magnetic field, MAS frequencies of 6.2-6.8 kHz, and microwave irradiation at 264.0 GHz from a 800 mW extended interaction oscillator source, the most effective compounds are triradicals that are related to the previously-described compound DOTOPA-TEMPO (see Thurber et al., 2010), but have improved solubility in glycerol/water solvent near neutral pH. Using these compounds at 30 mM total nitroxide concentration, we observe DNP enhancement factors of 92-128 for cross-polarized 13C NMR signals from 15N,13C-labeled melittin in partially protonated glycerol/water, and build-up times of 2.6-3.8 s for 1H spin polarizations. Net sensitivity enhancements with biradical and tetraradical dopants, taking into account absolute 13C NMR signal amplitudes and build-up times, are approximately 2-4 times lower than with the best triradicals.

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

2014-07-01

346

Solid-State NMR, Crystallographic, and Computational Investigation of Bisphosphonates and Farnesyl Diphosphate Synthase-Bisphosphonate Complexes  

SciTech Connect

Bisphosphonates are a class of molecules in widespread use in treating bone resorption diseases and are also of interest as immunomodulators and anti-infectives. They function by inhibiting the enzyme farnesyl diphosphate synthase (FPPS), but the details of how these molecules bind are not fully understood. Here, we report the results of a solid-state {sup 13}C, {sup 15}N, and {sup 31}P magic-angle sample spinning (MAS) NMR and quantum chemical investigation of several bisphosphonates, both as pure compounds and when bound to FPPS, to provide information about side-chain and phosphonate backbone protonation states when bound to the enzyme. We then used computational docking methods (with the charges assigned by NMR) to predict how several bisphosphonates bind to FPPS. Finally, we used X-ray crystallography to determine the structures of two potent bisphosphonate inhibitors, finding good agreement with the computational results, opening up the possibility of using the combination of NMR, quantum chemistry and molecular docking to facilitate the design of other, novel prenytransferase inhibitors.

Mao,J.; Mukherjee, S.; Zhang, Y.; Cao, R.; Sanders, J.; Song, Y.; Zhang, Y.; Meints, G.; Gao, Y.; et al.

2006-01-01

347

Structure and alignment of the membrane-associated antimicrobial peptide arenicin by oriented solid-state NMR spectroscopy.  

PubMed

The antimicrobial arenicin peptides are cationic amphipathic sequences that strongly interact with membranes. Through a cystine ring closure a cyclic ?-sheet structure is formed in aqueous solution, which persists when interacting with model membranes. In order to investigate the conformation, interactions, dynamics, and topology of their bilayer-associated states, arenicin 1 and 2 were prepared by chemical solid-phase peptide synthesis or by bacterial overexpression, labeled selectively or uniformly with (15)N, reconstituted into oriented membranes, and investigated by proton-decoupled (31)P and (15)N solid-state NMR spectroscopy. Whereas the (31)P NMR spectra indicate that the peptide induces orientational disorder at the level of the phospholipid head groups, the (15)N chemical shift spectra agree well with a regular ?-sheet conformation such as the one observed in micellar environments. In contrast, the data do not fit the twisted ?-sheet structure found in aqueous buffer. Furthermore, the chemical shift distribution is indicative of considerable conformational and/or topological heterogeneity when at the same time the (15)N NMR spectra exclude alignments of the peptide where the ?-sheet lies side ways on the membrane surface. The ensemble of experimental constraints, the amphipathic character of the peptide, and in particular the distribution of the six arginine residues are in agreement with a boatlike dimer structure, similar or related to the one observed in micellar solution, that floats on the membrane surface with the possibility to oligomerize into higher order structures and/or to insert in a transmembrane fashion. PMID:21456583

Salnikov, Evgeniy S; Aisenbrey, Christopher; Balandin, Sergey V; Zhmak, Maxim N; Ovchinnikova, Tatiana V; Bechinger, Burkhard

2011-05-10

348

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 25-30K range, a 9.4T magnetic field, MAS frequencies of 6.2-6.8kHz, and microwave irradiation at 264.0GHz from a 800mW 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 30mM 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

349

Unlocking the molecular structure of fungal melanin using 13C biosynthetic labeling and solid-state NMR.  

PubMed

Melanins are enigmatic pigments found in all biological kingdoms that are associated with a variety of functions, including microbial virulence. Despite being ubiquitous in nature, melanin pigments have long resisted atomic-level structural examination because of their insolubility and amorphous organization. Cryptococcus neoformans is a human pathogenic fungus that melanizes only when provided with exogenous substrate, thus offering a unique system for exploring questions related to melanin structure at the molecular level. We have exploited the requirement for exogenous substrate in melanin synthesis as well as the capabilities of high-resolution solid-state nuclear magnetic resonance (NMR) to establish the predominantly aliphatic composition of l-dopa melanin and to introduce (13)C labels that permit the identification of proximal carbons in the developing biopolymer. By swelling solid melanin samples in organic solvents and using two-dimensional heteronuclear NMR in conjunction with magic-angle spinning, we have identified chemical bonding patterns typical of alkane, alkene, alcohol, ketone, ester, and indole functional groups. These findings demonstrate the feasibility of a novel approach to determining the structure of melanin using metabolic labeling and NMR spectroscopy. PMID:12846559

Tian, Shiying; Garcia-Rivera, Javier; Yan, Bin; Casadevall, Arturo; Stark, Ruth E

2003-07-15

350

Solid-state NMR analysis of the {beta}-strand orientation of the protofibrils of amyloid {beta}-protein  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer The supramolecular structure of A{beta}42 protofibrils was analyzed by solid-state NMR. Black-Right-Pointing-Pointer The Ala-21 residue in the A{beta}42 protofibrils is included in a slightly disordered {beta}-strand. Black-Right-Pointing-Pointer The A{beta}42 protofibrils do not form intermolecular in-register parallel {beta}-sheets. -- Abstract: Alzheimer's disease (AD) is caused by abnormal deposition (fibrillation) of a 42-residue amyloid {beta}-protein (A{beta}42) in the brain. During the process of fibrillation, the A{beta}42 takes the form of protofibrils with strong neurotoxicity, and is thus believed to play a crucial role in the pathogenesis of AD. To elucidate the supramolecular structure of the A{beta}42 protofibrils, the intermolecular proximity of the Ala-21 residues in the A{beta}42 protofibrils was analyzed by {sup 13}C-{sup 13}C rotational resonance experiments in the solid state. Unlike the A{beta}42 fibrils, an intermolecular {sup 13}C-{sup 13}C correlation was not found in the A{beta}42 protofibrils. This result suggests that the {beta}-strands of the A{beta}42 protofibrils are not in an in-register parallel orientation. A{beta}42 monomers would assemble to form protofibrils with the {beta}-strand conformation, then transform into fibrils by forming intermolecular parallel {beta}-sheets.

Doi, Takashi [Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)] [Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); Masuda, Yuichi, E-mail: masuda@mail.pharm.tohoku.ac.jp [Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan) [Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578 (Japan); Irie, Kazuhiro [Graduate School of Agriculture, Kyoto University, Kyoto 606-8502 (Japan)] [Graduate School of Agriculture, Kyoto University, Kyoto 606-8502 (Japan); Akagi, Ken-ichi; Monobe, Youko; Imazawa, Takayoshi [Section of Laboratory Equipment, Division of Biomedical Research, National Institute of Biomedical Innovation, Osaka 567-0085 (Japan)] [Section of Laboratory Equipment, Division of Biomedical Research, National Institute of Biomedical Innovation, Osaka 567-0085 (Japan); Takegoshi, K. [Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)] [Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)

2012-11-30

351

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

352

Structure of Oxide Glasses under Compression and Confinement: Insights from High-resolution Solid-state NMR and Non-resonant Inelastic X-ray Scattering  

NASA Astrophysics Data System (ADS)

The atomic and nano-scale structure of non-crystalline oxides with varying degree of confinement and compression (pressure) are essential to understand the atomic origins of thermo-mechanical properties and kinetic stability of these materials in the earth's surfaces and interiors. Despite this importance, the effect of confinement and pressure on the nature of bonding in the non-crystalline oxides have remained one of the challenging problems in mineral physics and condensed matter physics due to lack of suitable experimental probes. Advances in element-specific experimental probes, such as non-resonant inelastic x-ray scattering (NRIXS) and high resolution solid-state NMR combined with the first principle calculations have revealed structural details of bonding transitions of amorphous oxides under compression and confinement (e.g. Lee, Rev. Min. Geochem. 2013 accepted; Phys. Rev. Letts, 2013 accepted; Proc. Nat. Aca. Sci. 2011, 108, 6847; Kim and Lee, Geochim. Cosmochim Acta. In press; Yi and Lee, Am Min 2012, 97, 897). Here, we present the key recent progress by NRIXS and NMR into the pressure and confinement-induced bonding transitions in non-crystalline oxides. Theoretical calculation of K-edge NRIXS spectrum took into consideration crystallographically-distinct sites and revealed that the edge features systematically shift to higher energy with increasing degree of densification in atomic arrangement in the polymorphs (from enstatite, perovskite, to post-perovskite). On the basis of these results, multi-nuclear (B, O, Li, Ca), multi-edge (K-, L-, and M-) XRS studies of diverse low z-oxide glasses indicated the pressure-induced increases in the fraction of triply coordinated oxygen above 20 GPa and showed evidence for the topologically driven densification in multi-component basaltic glasses. Finally, we report the first high-resolution solid-state NMR results for the amorphous oxides under confinement where the degree of structural disorder tends to decrease with increasing degree of confinement. These results allow us to microscopically confine the geochemical processes involving interactions between melts and fluids.

Lee, S.

2013-12-01

353

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

PubMed

Linear peptide antibiotics have been isolated from amphibians, insects and humans and used as templates to design cheaper and more potent analogues for medical applications. Peptides such as cecropins or magainins are < or = 40 amino acids in length. Many of them have been prepared by solid-phase peptide synthesis with isotopic labels incorporated at selected sites. Structural analysis by solid-state NMR spectroscopy and other biophysical techniques indicates that these peptide antibiotics strongly interact with lipid membranes. In bilayer environments they exhibit amphipathic alpha-helical conformations and alignments of the helix axis parallel to the membrane surface. This contrasts the transmembrane orientations observed for alamethicin or gramicidin A. Models that have been proposed to explain the antibiotic and pore-forming activities of membrane-associated peptides, as well as other experimental results, include transmembrane helical bundles, wormholes, carpets, detergent-like effects or the in-plane diffusion of peptide-induced bilayer instabilities. PMID:10590307

Bechinger, B

1999-12-15

354

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

355

Solid-state NMR ¹³C and ¹?N resonance assignments of a seven-transmembrane helical protein Anabaena Sensory Rhodopsin.  

PubMed

Anabaena Sensory Rhodopsin (ASR) is a unique microbial rhodopsin that displays photocromism, interacts with soluble transducer, and may be involved in gene regulation. Here we report nearly complete spectroscopic (13)C and (15)N assignments of ASR reconstituted in lipids, obtained using two- and three-dimensional magic angle spinning solid state NMR spectroscopy on alternately (13)C labeled samples. The obtained chemical shifts are used to characterize the protein backbone conformation. They suggest that lipid-reconstituted ASR has a fold generally similar to that seen in earlier X-ray studies, but with a number of important differences. SSNMR detects double conformations for a number of residues on the cytoplasmic side. PMID:22983928

Wang, Shenlin; Shi, Lichi; Okitsu, Takashi; Wada, Akimori; Brown, Leonid S; Ladizhansky, Vladimir

2013-10-01

356

Solid-state proton NMR of paramagnetic metal complexes: DANTE spin echoes for selective excitation in inhomogeneously broadened lines  

NASA Astrophysics Data System (ADS)

The paramagnetic complex bis(oxazolinylphenyl)amine-Fe(III)Cl2 is investigated by means of solid-state proton NMR at 18.8 T (800 MHz) using magic-angle spinning at 65 kHz. Spin echoes that are excited and refocused by combs of rotor-synchronized pulses in the manner of 'Delays Alternating with Nutation for Tailored Excitation' (DANTE) allow one to characterize different chemical environments that severely overlap in conventional MAS spectra. Such sequences combine two apparently contradictory features: an overall bandwidth exceeding several MHz, and very selective irradiation of a few kHz within inhomogeneously broadened sidebands. The experimental hyperfine interactions correlate well with DFT calculations.

Carnevale, Diego; Perez Linde, A. J.; Bauer, Gerald; Bodenhausen, Geoffrey

2013-08-01

357

Solid-state 13C NMR spectroscopy studies of xylans in the cell wall of Palmaria palmata (L. Kuntze, Rhodophyta).  

PubMed

The chemical structure and interactions of the cell wall polysaccharides from the red edible seaweed Palmaria palmata were studied by liquid-like magic-angle-spinning (MAS) and cross-polarization MAS (CPMAS) solid-state 13C NMR spectroscopy. The liquid-like MAS and CPMAS 13C NMR spectra of the rehydrated algal powder revealed the presence of beta-(1-->4)/beta-(1-->3)-linked D-xylan with chemical shifts close to those observed in the solution 13C NMR spectrum of the polysaccharide. Observation of mix-linked xylan in the liquid-like MAS 13C NMR spectrum indicated that part of this cell wall polysaccharide is loosely held in the alga. The CPMAS NMR spectrum of the dry algal powder alcohol insoluble residue (AIR) showed broad peaks most of which corresponded to the mix-linked xylan. Hydration of AIR induced a marked increase in the signal resolution also in the CPMAS NMR spectra together with a shift of the C-3 and C-4 signals of the (1-->3)- and (1-->4)-linked xylose, respectively. Such modifications were present in the spectrum of hydrated (1-->3)-linked xylan from the green seaweed Caulerpa taxifolia and absent in that of (1-->4)-linked xylan from P. palmata. This result emphasizes the important role of (1-->3) linkages on the mix-linked xylan hydration-induced conformational rearrangement. The mix-linked xylan signals were observed in the CPMAS NMR spectrum of hydrated residues obtained after extensive extractions by NaOH or strong chaotropic solutions indicating strong hydrogen bonds or covalent linkages. T(1 rho) relaxations were measured close or above 10 ms for the mix-linked xylan in the dry and hydrated state in AIR and indicated that the overall xylan chains likely remain rigid. Rehydration of the mix-linked xylan lead to a decrease in the motion of protons bounded to the C-1 and C-4 carbons of the (1-->4)-linked xylose supporting the re-organization of the xylan chains under hydration involving junction-zones held by hydrogen bonds between adjacent (1-->4)-linked xylose blocks. The CPMAS NMR spectrum of both dry and rehydrated residues obtained after NaOH and HCl extractions demonstrated the presence of cellulose and (1-->4)-linked xylans. The structures of the different polysaccharides are discussed in relation to their interactions and putative functions on the cell wall mechanical properties in P. palmata. PMID:12860427

Lahaye, Marc; Rondeau-Mouro, Corinne; Deniaud, Estelle; Buléon, Alain

2003-07-22

358

Solid State NMR Methods for Coal Science. Progress Report, September 15, 1983-December 31, 1983.  

National Technical Information Service (NTIS)

Several novel NMR spectroscopic techniques are being developed for application to coal science. Multiple pulse decoupling techniques are being developed to allow high resolution scalar coupled exp 13 C CP-MAS spectra of coals to be obtained. This method w...

K. W. Zilm

1984-01-01

359

Hydration and plasticization effects in cellulose acetate: a solid-state NMR study  

Microsoft Academic Search

The conjoint effects of water and diethyl phthalate (DEP) plasticizer on molecular motion in cellulose acetate (CA) have been examined. 1H, 13C and cross polarization NMR data reveal a number of interesting features. As in other hydrated polymers, there are different types of water ranging from tightly bound to bulk-like water in CA. Both tightly and loosely bound water can

Christopher M. Keely; Xiaoqing Zhang; Vincent J. McBrierty

1995-01-01

360

Helium-cooling and -spinning dynamic nuclear polarization for sensitivity-enhanced solid-state NMR at 14 T and 30 K.  

PubMed

We describe a (1)H polarization enhancement via dynamic nuclear polarization (DNP) at very low sample temperature T?30 K under magic-angle spinning (MAS) conditions for sensitivity-enhanced solid-state NMR measurement. Experiments were conducted at a high external field strength of 14.1 T. For MAS DNP experiments at T<90 K, a new probe system using cold helium gas for both sample-cooling and -spinning was developed. The novel system can sustain a low sample temperature between 30 and 90K for a period of time >10 h under MAS at ?(R)?3 kHz with liquid He consumption of ?6 L/h. As a microwave source, we employed a high-power, continuously frequency-tunable gyrotron. At T?34 K, (1)H DNP enhancement factors of 47 and 23 were observed with and without MAS, respectively. On the basis of these observations, a discussion on the total NMR sensitivity that takes into account the effect of sample temperature and external field strength used in DNP experiments is presented. It was determined that the use of low sample temperature and high external field is generally rewarding for the total sensitivity, in spite of the slower polarization buildup at lower temperature and lower DNP efficiency at higher field. These findings highlight the potential of the current continuous-wave DNP technique also at very high field conditions suitable to analyze large and complex systems, such as biological macromolecules. PMID:23079589

Matsuki, Yoh; Ueda, Keisuke; Idehara, Toshitaka; Ikeda, Ryosuke; Ogawa, Isamu; Nakamura, Shinji; Toda, Mitsuru; Anai, Takahiro; Fujiwara, Toshimichi

2012-12-01

361

Helium-cooling and -spinning dynamic nuclear polarization for sensitivity-enhanced solid-state NMR at 14 T and 30 K  

NASA Astrophysics Data System (ADS)

We describe a 1H polarization enhancement via dynamic nuclear polarization (DNP) at very low sample temperature T ? 30 K under magic-angle spinning (MAS) conditions for sensitivity-enhanced solid-state NMR measurement. Experiments were conducted at a high external field strength of 14.1 T. For MAS DNP experiments at T ? 90 K, a new probe system using cold helium gas for both sample-cooling and -spinning was developed. The novel system can sustain a low sample temperature between 30 and 90 K for a period of time >10 h under MAS at ?R ? 3 kHz with liquid He consumption of ?6 L/h. As a microwave source, we employed a high-power, continuously frequency-tunable gyrotron. At T ? 34 K, 1H DNP enhancement factors of 47 and 23 were observed with and without MAS, respectively. On the basis of these observations, a discussion on the total NMR sensitivity that takes into account the effect of sample temperature and external field strength used in DNP experiments is presented. It was determined that the use of low sample temperature and high external field is generally rewarding for the total sensitivity, in spite of the slower polarization buildup at lower temperature and lower DNP efficiency at higher field. These findings highlight the potential of the current continuous-wave DNP technique also at very high field conditions suitable to analyze large and complex systems, such as biological macromolecules.

Matsuki, Yoh; Ueda, Keisuke; Idehara, Toshitaka; Ikeda, Ryosuke; Ogawa, Isamu; Nakamura, Shinji; Toda, Mitsuru; Anai, Takahiro; Fujiwara, Toshimichi

2012-12-01

362

A multinuclear 1H, 13C and 11B solid-state MAS NMR study of 16- and 18-electron organometallic ruthenium and osmium carborane complexes.  

PubMed

The first (1)H, (13)C, (31)P and (11)B solid state MAS NMR studies of electron-deficient carborane-containing ruthenium and osmium complexes [Ru/Os(p-cym)(1,2-dicarba-closo-dodecaborane-1,2-dithiolate)] are reported. The MAS NMR data from these 16-electron complexes are compared to those of free carborane-ligand and an 18-electron triphenylphosphine ruthenium adduct, and reveal clear spectral differences between 16- and 18-electron organometallic carborane systems in the solid state. PMID:24554004

Barry, Nicolas P E; Kemp, Thomas F; Sadler, Peter J; Hanna, John V

2014-04-01

363

Planar microcoil-based microfluidic NMR probes  

Microsoft Academic Search

Microfabricated small-volume NMR probes consisting of electroplated planar microcoils integrated on a glass substrate with etched microfluidic channels are fabricated and tested. 1H NMR spectra are acquired at 300MHz with three different probes having observed sample volumes of respectively 30, 120, and 470nL. The achieved sensitivity enables acquisition of an 1H spectrum of 160?g sucrose in D2O, corresponding to a

C. Massin; F. Vincent; A. Homsy; K. Ehrmann; G. Boero; P.-A Besse; A. Daridon; E. Verpoorte; N. F de Rooij; R. S Popovic

2003-01-01

364

Cation substitution in ?-tricalcium phosphate investigated using multi-nuclear, solid-state NMR  

NASA Astrophysics Data System (ADS)

The substitution of aluminium, gallium and sodium cations into ?-tricalcium phosphate (?-TCP; Ca3(PO4)2) has been investigated, and the Ca sites involved successfully determined, using a combination of 1D 31P, 27Al, 71Ga, 23Na and 43Ca (natural abundance) NMR and 2D 27Al{31P}, 71Ga{31P} and 23Na{31P} rotary-resonance-recoupled heteronuclear multiple-quantum correlation (R3-HMQC) NMR. Over the compositional range studied, substitution of Ca2+ by Al3+ or Ga3+ was observed only on the Ca(5) site, whilst substitution by Na+ was confined to the Ca(4) site. Some AlPO4 or GaPO4 second phase was observed at the highest doping levels in the Al3+ and Ga3+ substituted samples.

Grigg, Andrew T.; Mee, Martin; Mallinson, Phillip M.; Fong, Shirley K.; Gan, Zhehong; Dupree, Ray; Holland, Diane

2014-04-01

365

Exp 13 C-NMR Tracer to Probe Coalification.  

National Technical Information Service (NTIS)

Solid-state NMR tracer experiments of synthetically prepared ( exp 13 C)lignins coalified under simulated geological conditions have illuminated a general chemical scheme for coalification. The labeling studies provide the first direct evidence for the co...

R. E. Botto R. Hayatsu R. G. Scott R. L. McBeth R. E. Winans

1985-01-01

366

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.

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

2012-01-01

367

Selective measurements of long-range homonuclear J-couplings in solid-state NMR  

NASA Astrophysics Data System (ADS)

We demonstrate here that the principle of frequency-selective spin-echoes can be extended to the measurements of long-range homonuclear scalar J-couplings in the solid-state. Singly or doubly frequency-selective pulses were used to generate either a J-modulated experiment (S) or a reference experiment (S0). The combination of these two distinct experiments provides experimental data that, in favorable cases, are insensitive to incoherent relaxation effects, and which can be used to estimate long-range homonuclear J-couplings in multiple spin-systems. The concept is illustrated in the case of a uniformly 13C and 15N labeled sample of L-histidine, where the absolute value of homonuclear J-couplings between two spins separated by one, two or three covalent bonds are measured. Moreover, we show that a 2J(15N-C-15N) coupling as small as 0.9 Hz can be precisely measured with the method presented here.

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

2013-06-01

368

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

369

Solid-state NMR study of metastable immiscibility in alkali borosilicate glasses  

Microsoft Academic Search

In several series of lithium, sodium, and potassium borosilicate glasses whose compositions traverse known regions of liquid–liquid phase separation, we have applied triple-quantum magic-angle spinning (3QMAS) 11B and 17O NMR to obtain high-resolution information about short-range structure and connections among various network structural units, and their variation with composition and thermal history. Oxygen-17 3QMAS spectra reveal changes in connectivities between

Lin-Shu Du; Jonathan F Stebbins

2003-01-01

370

Advanced solid-state NMR characterization of marine dissolved organic matter isolated using the coupled reverse osmosis/electrodialysis method.  

PubMed

Advanced (13)C solid-state techniques were employed to investigate the major structural characteristics of two surface-seawater dissolved organic matter (DOM) samples isolated using the novel coupled reverse osmosis/electrodialysis method. The NMR techniques included quantitative (13)C direct polarization/magic angle spinning (DP/MAS) and DP/MAS with recoupled dipolar dephasing, (13)C cross-polarization/total sideband suppression (CP/TOSS), (13)C chemical shift anisotropy filter, CH, CH(2), and CH(n) selection, two-dimensional (1)H-(13)C heteronuclear correlation NMR (2D HETCOR), 2D HETCOR combined with dipolar dephasing, and (15)N cross-polarization/magic angle spinning (CP/MAS). The two samples (Coastal and Marine DOM) were collected at the mouth of the Ogeechee River and in the Gulf Stream, respectively. The NMR results indicated that they were structurally distinct. Coastal DOM contained significantly more aromatic and carbonyl carbons whereas Marine DOM was markedly enriched in alkoxy carbon (e.g., carbohydrate-like moieties). Both samples contained significant amide N, but Coastal DOM had nitrogen bonded to aromatic carbons. Our dipolar-dephased spectra indicated that a large fraction of alkoxy carbons were not protonated. For Coastal DOM, our NMR results were consistent with the presence of the major structural units of (1) carbohydrate-like moieties, (2) lignin residues, (3) peptides or amino sugars, and (4) COO-bonded alkyls. For Marine DOM, they were (1) carbohydrate-like moieties, (2) peptides or amino sugars, and (3) COO-bonded alkyls. In addition, both samples contained significant amounts of nonpolar alkyl groups. The potential sources of the major structural units of DOM were discussed in detail. Nonprotonated O-alkyl carbon content was proposed as a possible index of humification. PMID:22553962

Mao, Jingdong; Kong, Xueqian; Schmidt-Rohr, Klaus; Pignatello, Joseph J; Perdue, E Michael

2012-06-01

371

Probing spin density and local structure in the Prussian blue analogues CsCd[Fe/Co(CN)6]·0.5H2O and Cd3[Fe/Co(CN)6]2·15H2O with solid-state MAS NMR spectroscopy.  

PubMed

Magic-angle spinning (MAS) NMR spectroscopy is used to study the local structure and spin delocalisation in Prussian blue analogues (PBAs). We selected two common archetypes of PBAs (A(I)M(II)[M(III)(CN)(6)]·xH(2)O and M(II)(3)[M(III)(CN)(6)](2)·xH(2)O, in which A(I) is an alkali ion, and M(II) and M(III) are transition-metal ions) that exhibit similar cubic frameworks but different microscopic structures. Whereas the first type of PBA contains interstitial alkali ions and does not exhibit any [M(III)(CN)(6)](3-) vacancies, the second type of PBA exhibits [M(III)(CN)(6)](3-) vacancies, but does not contain inserted alkali ions. In this study, we selected Cd(II) as a divalent metal in order to use the (113)Cd nuclei (I=1/2) as a probe of the local structure. Here, we present a complete MAS NMR study on two series of PBAs of the formulas Cd(II)(3)[Fe(III)(x)Co(III)(1-x)(CN)(6)](2)·15H(2)O with x=0 (1), 0.25 (2), 0.5 (3), 0.75 (4) and 1 (5), and CsCd(II)[Fe(III)(x)Co(III)(1-x)(CN)(6)]·0.5H(2)O with x=0 (6), 0.25 (7), 0.5 (8), 0.75 (9) and 1 (10). Interestingly, the presence of Fe(III) magnetic centres in the vicinity of the cadmium sites has a magnifying-glass effect on the NMR spectrum: it induces a striking signal spread such that the resolution is notably improved compared to that achieved for the diamagnetic PBAs. By doping the sample with varying amounts of diamagnetic Co(III) and comparing the NMR spectra of both types of PBAs, we have been able to give a view of the structure which is complementary to that usually obtained from X-ray diffraction studies. In particular, this study has shown that the vacancies are not randomly distributed in the mesoporous PBAs. Moreover the cadmium chemical shift, which is a measure of the hyperfine coupling, allows the estimation of the spin density on the cadmium nucleus, and consequently, the elucidation of the spin delocalisation mechanism in these compounds along with its dependency on structural parameters. PMID:21882267

Flambard, Alexandrine; Köhler, Frank H; Lescouëzec, Rodrigue; Revel, Bertrand

2011-10-01

372

Solid-state 13C NMR study of cholesteric liquid crystals.  

PubMed

We investigated the structural behavior of cholesteric liquid crystals of 4-(hexyloxy)-4'-cyanobiphenyl (6OCB) in an 11.7 T magnetic field by solid-state (13)C nuclear magnetic resonance. Five 6OCB cholesteric liquid crystal systems were prepared with 4-methoxyphenyl 3,4-O-isopropylidene-2,6-bis-O-(4-methylbenzoyl)-?-d-galactopyranoside (CR), in which 6OCB was doped with 0.51, 1.00, 2.34, 5.60, and 6.47 mol % CR, giving products with helical twisting powers (HTPs) of 0.28, 0.54, 1.27, 3.05, and 3.52 ?m(-1), respectively. Analyses of the alignment-induced shifts showed that the liquid crystals directors in pure 6OCB and 6OCB doped with 0.51 and 1.00 mol % CR become aligned with the 11.7 T magnetic field direction. However, 6OCB doped with 2.34, 5.60, and 6.47 mol % CR retained their cholesteric structures when the magnetic field was applied. The critical HTP value for resisting realignment by magnetic field was estimated to be approximately 1.27 ?m(-1). A biaxiality of the phase was partially considered during spectral simulations, although the molecular shape of 6OCB can be defined as cylinderical when it is rotating rapidly. Our current understanding is that the order parameters in the cholesteric structures are not uniform; i.e., the molecular directors already aligned almost perpendicular to the magnetic field are significantly perturbed by the external field. PMID:24188010

Yamada, Kazuhiko; Marumo, Kazuhiro; Kang, Sungmin; Deguchi, Kenzo; Nakai, Toshihito; Shimizu, Tadashi; Watanabe, Junji

2013-12-19

373

Mechanistic insight into formation and changes of nanoparticles in MgF2 sols evidenced by liquid and solid state NMR.  

PubMed

The fluorolytic sol-gel reaction of magnesium methoxide with HF in methanol was studied by (19)F, (1)H and (13)C liquid and solid state NMR. In (19)F NMR five different species were identified, three of which belong to magnesium fluoride nanoparticles, i.e. NMR gave access to local structures of solid particles in suspensions. The long-term evolution of (19)F signals was followed and along with (19)F MAS NMR experiments of sols rotating at 13 kHz mechanistic insights into the ageing processes were obtained. PMID:22214975

Karg, M; Scholz, G; König, R; Kemnitz, E

2012-02-28

374

Molecular dynamics from 2H Quadrupolar Carr-Purcell-Meiboom-Gill solid-state NMR spectroscopy  

NASA Astrophysics Data System (ADS)

The 2H quadrupolar Carr-Purcell-Meiboom-Gill (QCPMG) NMR experiment is proposed as a convenient method to obtain detailed information about molecular dynamics in solids. Compared to the quadrupolar-echo (QE) experiment QCPMG offers two advantages. First, a sensitivity enhancement by about an order of magnitude is achieved by splitting the QE spectrum into spin-echo sidebands. Second, the lineshape of the individual sidebands provides detailed information about the molecular dynamics and increases the dynamic range by two orders of magnitude. The 2H QCPMG method is demonstrated experimentally and numerically using the two-fold flip process in dimethyl sulfone.

Larsen, Flemming H.; Jakobsen, Hans J.; Ellis, Paul D.; Nielsen, Niels Chr.

1998-08-01

375

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

376

13C solid state NMR investigation of structural relaxation of the polymer backbone in poly (ethylmethacrylate).  

PubMed

Geometry and time scale of structural relaxation of poly(n-alkylmethacrylates) above the glass transition is studied by temperature dependent one- and two-dimensional 13C-NMR spectroscopy. The geometry of the isotropization of the polymer backbone as deduced from detailed analysis of spectral line shapes is identified as random angular jumps. Analysis of echo decays confirms that at a given temperature this isotropization can adequately be described with a single correlation time. The results are discussed in terms of conformational memory and local structure recently identified in these polymeric glasses. PMID:15589734

Wind, Michael; Brombacher, Lothar; Heuer, Andreas; Graf, Robert; Spiess, Hans Wolfgang

2005-01-01

377

Solid state NMR chemical shift assignment and conformational analysis of a cellulose binding protein facilitated by optimized glycerol enrichment.  

PubMed

Magic-angle spinning solid-state NMR has been applied to study CBM3b-Cbh9A (CBM3b), a cellulose binding module protein belonging to family 3b. It is a 146-residue protein having a unique nine-stranded ?-sandwich fold, in which 35 % of the structure is in a ?-sheet conformation and the remainder of the protein is composed of loops and unstructured regions. Yet, the protein can be crystalized and it forms elongated needles. Close to complete chemical shift assignment of the protein was obtained by combining two- and three-dimensional experiments using a fully labeled sample and a glycerol-labeled sample. The use of an optimized protocol for glycerol-based sparse labeling reduces sample preparation costs and facilitates the assignment of the large number of aromatic signals in this protein. Conformational analysis shows good correlation between the NMR-predicted secondary structure and the reported X-ray crystal structure, in particular in the structured regions. Residues which show high B-factor values are situated mainly in unstructured regions, and are missing in our spectra indicating conformational flexibility rather than heterogeneity. Interestingly, long-range contacts, which could be clearly detected for tyrosine residues, could not be observed for aromatic phenylalanine residues pointing into the hydrophobic core, suggesting possible high ring mobility. These studies will allow us to further investigate the cellulose-bound form of CBM proteins. PMID:24824437

Ivanir, Hadar; Goldbourt, Amir

2014-07-01

378

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

PubMed

Using solid state (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. PMID:23896223

Eldridge, S M; Chen, C R; Xu, Z H; Nelson, P N; Boyd, S E; Meszaros, I; Chan, K Y

2013-11-01

379

Solid-State NMR Reveals the Hydrophobic-Core Location of Poly(amidoamine) Dendrimers in Biomembranes  

PubMed Central

Poly(amidoamine) (PAMAM) dendrimer nanobiotechnology shows great promise in targeted drug delivery and gene therapy. Because of the involvement of cell membrane lipids with the pharmacological activity of dendrimer nanomedicines, the interactions between dendrimers and lipids are of particular relevance to the pharmaceutical applications of dendrimers. In this study, solid-state NMR was used to obtain a molecular image of the complex of generation 5 PAMAM dendrimer with the lipid bilayer. Using 1H radio frequency driven dipolar recoupling (RFDR) and 1H magic angle spinning (MAS) nuclear Overhauser effect spectroscopy (NOESY) techniques, we show that dendrimers are thermodynamically stable when inserted into zwitterionic lipid bilayers. 14N and 31P NMR experiments on static samples and measurements of the mobility of C–H bonds using a 2D proton detected local field protocol under MAS corroborate these results. The localization of dendrimers in the hydrophobic core of lipid bilayers restricts the motion of bilayer lipid tails, with the smaller G5 dendrimer having more of an effect than the larger G7 dendrimer. Fragmentation of the membrane does not occur at low dendrimer concentrations in zwitterionic membranes. Because these results show that the amphipathic dendrimer molecule can be stably incorporated in the interior of the bilayer (as opposed to electrostatic binding at the surface), they are expected to be useful in the design of dendrimer-based nanobiotechnologies.

Smith, Pieter E. S.; Brender, Jeffrey R.; Durr, Ulrich H. N.; Xu, Jiadi; Mullen, Douglas G.; Banaszak Holl, Mark M.; Ramamoorthy, Ayyalusamy

2010-01-01

380

Color-discriminating retinal configurations of sensory rhodopsin?i by photo-irradiation solid-state NMR spectroscopy.  

PubMed

SRI (sensory rhodopsin?I) can discriminate multiple colors for the attractant and repellent phototaxis. Studies aimed at revealing the color-dependent mechanism show that SRI is a challenging system not only in photobiology but also in photochemistry. During the photoreaction of SRI, an M-intermediate (attractant) transforms into a P-intermediate (repellent) by absorbing blue light. Consequently, SRI then cycles back to the G-state. The photoreactions were monitored with the (13) C?NMR signals of [20-(13) C]retnal-SrSRI using in?situ photo-irradiation solid-state NMR spectroscopy. The M-intermediate was trapped at -40?°C by illumination at 520?nm. It was transformed into the P-intermediate by subsequent illumination at 365?nm. These results reveal that the G-state could be directly transformed to the P-intermediate by illumination at 365?nm. Thus, the stationary trapped M- and P-intermediates are responsible for positive and negative phototaxis, respectively. PMID:24846351

Yomoda, Hiroki; Makino, Yoshiteru; Tomonaga, Yuya; Hidaka, Tetsurou; Kawamura, Izuru; Okitsu, Takashi; Wada, Akimori; Sudo, Yuki; Naito, Akira

2014-07-01

381

Random Telegraph Signal: a local probe for single point defect studies in solid-state devices  

Microsoft Academic Search

This paper provides an overview on Random Telegraph Signals (RTSs) in solid-state devices and more in particular in scaled silicon MOSFETs. It tries to answer the following questions: what is an RTS? How does it behave as a function of the operation conditions (temperature, bias)? And what can we learn from it? It will be shown that when properly analysed,

E. Simoen; C. Claeys

2002-01-01

382

Solid-state /sup 15/N NMR of oriented lipid bilayer bound gramicidin A'  

SciTech Connect

Highly oriented samples of lipid and gramicidin A' (8:1 molar ratio) have been prepared with the samples extensively hydrated (approximately 70% water v/w). These preparations have been shown to be completely in a bilayer phase with a transition temperature of 28/sup 0/C, and evidence is presented indicating that the gramicidin is in the channel conformation. An estimate of the disorder in the alignment of the bilayers parallel with the glass plates used to align the bilayers can be made from the asymmetry of the nuclear magnetic resonances (NMR). Such an analysis indicates a maximal range of disorder of +-3/sup 0/. Uniformly /sup 15/N-labeled gramicidin has been biosynthesized by Bacillus brevis grown in a media containing /sup 15/N-labeled Escherichia coli cells as the only nitrogen source. When prepared with labeled gramicidin, the oriented samples result in high-resolution /sup 15/N NMR spectra showing 12 resonances for the 20 nitrogen sites of the polypeptide. The frequency of the three major multiple resonance peaks has been interpreted to yield the approximate orientation of the N-H bonds in the peptide linkages with respect to the magnetic field. The bond orientations are only partially consistent with the extant structural models of gramicidin.

Nicholson, L.K.; Moll, F.; Mixon, T.E.; LoGrasso, P.V.; Lay, J.C.; Cross, T.A.

1987-10-20

383

Destabilization of cationic lipid vesicles by an anionic hydrophobically modified poly(N-isopropylacrylamide) copolymer: a solid-state 31P NMR and 2H NMR study.  

PubMed

The effect of binding PNIPAM-Py-Gly, a copolymer of N-isopropylacrylamide, N-[4-(1-pyrenyl)butyl]-N-n-octadecylacrylamide and N-glycydyl-acrylamide, on membrane stability in cationic multilamellar vesicles (MLVs) was examined using solid-state phosphorus (31P) and deuterium (2H) nuclear magnetic resonance (NMR) spectroscopy. For MLVs of composition n-octadecyldiethylene oxide (ODEO)+cholesterol (CHOL)+1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)+dimethyldioctadecylammonium bromide (DODAB) (molar ratios 75:10.5:10.5:4), PNIPAM-Py-Gly induced a complete conversion from a bilayer-type 31P NMR spectrum to one characteristic of lipids undergoing isotropic motional averaging, indicating the existence of regions of high local membrane curvature. This response was sustained even at elevated temperatures. For MLVs of composition POPC+1,2-dioleoyloxy-3-(trimethylammonio)-propane (DOTAP), only at high levels of DOTAP and ionic strength did PNIPAM-Py-Gly induce even a partial conversion to an isotropic-type 31P NMR spectrum. At lower pH this effect was diminished. Raising the temperature eliminated the isotropic 31P NMR spectral component, and this effect was not reversible upon returning to room temperature. 2H NMR spectroscopy of headgroup-deuterated DOTAP and POPC confirmed the 31P NMR results, but did not provide specific surface electrostatic information. We conclude that the binding of PNIPAM-Py-Gly to phospholipid-based vesicles is dominated by electrostatic attraction between cationic lipids and the polymer's glycine residues. At high binding levels, the polymer assumes a collapsed conformation at the surface, resulting in regions of high local curvature of the lipid assembly. For ODEO-based liposomes, these effects are magnified by the additional contribution of hydrogen bonding to the strength of polymer binding. PMID:9858737

Franzin, C M; Macdonald, P M; Polozova, A; Winnik, F M

1998-12-01

384

Three-dimensional solid-state NMR spectroscopy of a peptide oriented in membrane bilayers  

Microsoft Academic Search

A three-dimensional 1H chemical shift\\/1H-15N dipolar coupling\\/15N chemical shift correlation spectrum was obtained on a sample of specifically 15N-labeled magainin peptides oriented in lipid bilayers between glass plates in a flat-coil probe. The spectrum showed complete resolution of the resonances from two labeled amide sites in all three dimensions. The three orientationally dependent frequencies associated with each resonance enabled the

A. Ramamoorthy; F. M. Marassi; M. Zasloff; S. J. Opella

1995-01-01

385

Quadrupolar Metal Nuclides in Bioinorganic Chemistry: Solid-State NMR Studies  

SciTech Connect

Metal ions play an important role in bioinorganic chemistry, however, following their respective chemistries is often complicated because several relevant metal ions (such as V5+, Cu1+, Zn2+, and Mg2+) are not always amenable to conventional UV/Vis or EPR spectroscopy. Rather, what we know of these metal sites has come from the characterization of the various compounds and proteins via x-ray crystallographic methods or from using surrogate metal probes for conventional spectroscopy

Lipton, Andrew S.; Ellis, Paul D.; Polenova, Tatyana E.

2009-09-16

386

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

NASA Astrophysics Data System (ADS)

The changes caused by heat treatment of gibbsite powder at 300-1473 K were studied using the X-ray diffraction (XRD), X-ray photoemission (XPS) spectra and 27Al magic angle spinning nuclear magnetic resonance spectroscopy (27Al MAS NMR). XRD analysis indicates that the transformation sequence involves the formation of ?-Al2O3 as an intermediate phase between ?- and ?-Al2O3. The crystallite size of ?-Al2O3 is as small as 10 nm. XPS analysis indicates that the ratio of aluminium atoms to oxygen atoms in ?-Al2O3 and ?-Al2O3 increases, whereas the expected ratio is observed in ?-Al2O3. The percentage of AlO4 units in the transition aluminas follows the same behaviour as the ratio of Al/O.

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

2014-07-01

387

Narrowing of the exciton lines using WAHUHA method of solid state NMR spectroscopy  

NASA Astrophysics Data System (ADS)

A method for allocating of two thermodynamic reservoirs which are not related to each other in high density exciton gas in semiconductors using the Schwinger representation for the projection operators of the effective spin (pseudospin) of the excitons is proposed. It is shown that the method of narrowing the NMR resonance lines in solids under the influence of a sequence of four electromagnetic pulses of the WAHUHA type can be applied for the line narrowing of the recombination emission and absorption of light by excitons in optical spectroscopy. We found out that, in contrast to the averaging to zero of the magnetic dipole-dipole interaction between nuclei, the exciton-exciton interaction is averaged only partially. This analysis for the excitons can be extended to other quasiparticles of boson type, i.e. biexcitons, polaritons and magnons, in solids.

Geru, I. I.

2011-10-01

388

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

389

Structure and multinuclear solid-state NMR of a highly birefringent lead-gold cyanide coordination polymer.  

PubMed

The coordination polymer Pb(H2O)[Au(CN)2]2 (1) was synthesized by the reaction of KAu(CN)2 and Pb(NO3)2. The structure contains 1-D chains of lead(II)-OH2 linked via Au(CN)2(-) moieties, generating a 2-D slab; weak aurophilic interactions of 3.506(2) and 3.4885(5) A occur within and between slabs. The geometry about each lead(II) is bicapped trigonal prismatic, having six N-bound cyanides at the prism vertices and waters at two of the faces. Dehydration at 175 degrees C yields microcrystalline Pb[Au(CN)2]2 (2), which, along with 1, was examined by 13C, 15N, 1H, and 207Pb solid-state NMR methods. Two 15N resonances are assigned to the mu2-bridging and hydrogen-bonding cyanides in 1. Upon dehydration, the 207Pb NMR spectrum becomes axially symmetric and yields a reduced shielding span, indicating higher site symmetry, while the 13C and 15N spectra reveal a single cyanide. Although no single-crystal X-ray structure of 2 could be obtained, a structure is proposed on the basis of the NMR and X-ray powder data, consisting of a lead(II) center in a distorted square-prismatic environment, with cyanides present at each corner. The birefringence of single crystals of 1 is found to be 7.0 x 10(-2) at room temperature. This value is large compared to that of most optical materials and can be attributed to the anisotropy of the 2-D slabs of 1, with all CN bonds aligned in the same direction by the polarizable lead(II) center. PMID:16536539

Katz, Michael J; Aguiar, Pedro M; Batchelor, Raymond J; Bokov, Alexei A; Ye, Zuo-Guang; Kroeker, Scott; Leznoff, Daniel B

2006-03-22

390

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

PubMed

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 approximately 1 A, 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 A (1.52 +/- 0.12 A for all heavy atoms), which improved to 0.49 +/- 0.05 A (1.19 +/- 0.07 A) 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 A bbRMSD (1.06 +/- 0.07 A); relative to the structure with distances alone, most of the improvement remained (bbRMSD 0.64 +/- 0.09 A; 1.29 +/- 0.07 A) 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

2008-03-25

391

NMR study of the solution-state dynamics and solid-state structure of tri-n-butyltin fluoride  

Microsoft Academic Search

Dynamics and structure of tri-n-butyltin fluoride in n-hexane solutions were probed using (tin-119) nuclear magnetic resonance spin relaxation methodologies. Significant relaxation-induced polarization transfer effects were observed and exploited. The experimental observations indicate that the tri-n-butyl fluoride exists in a polymeric form in solution. For a 0.10% (w\\/w) solution at 25 [degree]C, NMR reveals significant orientational\\/exchange relaxation on both the microsecond

Y. W. Kim; A. Labouriau; C. M. Taylor; William L. Earl; L. G. Werbelow

1994-01-01

392

Exploration of structure and function in biomolecules through solid-state NMR and computational methods  

NASA Astrophysics Data System (ADS)

Solid-State Nuclear Magnetic Resonance (SSNMR) spectroscopy and quantum mechanical calculations are powerful analysis tools. Leveraged independently, each method yields important nuclear and molecular information. Used in concert, SSNMR and computational techniques provide complementary data about the structure of solids. These methods are particularly useful in characterizing the structures of microcrystalline organic compounds and revealing mechanisms of biological activity. Such applications may possess special relevance in analysis of pharmaceutical products; 90% of all pharmaceuticals are marketed as solids and bioactivity is strongly linked with molecular conformation. Accordingly, this dissertation employs both SSNMR and quantum mechanical computation to study three bioactive molecules: citrinin, two forms of Atrasentan (Abt-627), and paclitaxel (Taxol RTM). First, a computational study is utilized to determine the mechanism for unusual antioxidant activity in citrinin. Here, molecular geometries and bond dissociation enthalpies (BDE) of the citrinin O--H groups are calculated from first principles (ab initio). The total molecular Hamiltonian is determined by approximating the individual contributors to energy including electronic energy and contributions from modes of molecular vibration. This study of citrinin clearly identifies specific reaction sites in the active form, establishing the central role of intramolecular hydrogen bonding in this activity. Notably, it is discovered that citrinin itself is not the active species. Instead, a pair of hydrated Michael addition products of citrinin act as radical scavengers via O--H bond dissociation. Next, two separate compounds of the anticancer drug Abt-627 (form I and form II) are examined via SSNMR. The three principal values of the 13C diagonalized chemical shift tensor are acquired through the high resolution 2D experiment, FIREMAT. Isotropic chemical shift assignments are made utilizing both dipolar dephasing experiments and 1H-- 13C heteronuclear correlation (HETCOR) experiments. A comparison of spectral data confirms the presence of two molecules in the asymmetric unit for form II (Z'=2) and regions of conformational variation between the two forms are posited. Structural rigidity is found throughout both forms and extends into the alkyl groups at the amine with similarties between form I and form II in this moiety. Likely regions of motion are found around the bond axes formed by C1--C5 in form I. This motion is also observed in one of the two molecules of form II. Tensor differences between the two forms at the tetrahydro-pyrrole center indicate that conformational variation between form I and form II exists in the dihedral angles formed by the atoms C14--C13--C3--C2, O--C12--C2--C1, C10--C5--C1--N1 and C21--C20--N1--C4. Finally, SSNMR is applied in conjunction with quantum mechanical calculations in the analysis of a novel polymorph of the anticancer drug paclitaxel. The three dimensional structure of paclitaxel is established through a combination of SSNMR tensor (13C & 15N) and 1H--13C HETCOR data. With two molecules in the asymmetric unit (Z'=2), this represents the first conformational characterization with Z'>1 established solely by SSNMR. Semi-empirical models are constructed and fitted to experimental data by adjusting the conformation of the paclitaxel models and selecting those conformers which minimize the difference between predicted and measured tensors. This computational grid search exhausively samples the conformation of paclitaxel, utilizing more than 600 independent models. HETCOR data at thirteen key positions provide shift assignment to the asymmetric unit for each comparison. The two distinct molecules of the asymmetric unit possess nearly identical baccatin III moieties with matching conformations of the C10 acetyl moiety. Additionally, both are found to exhibit an extended conformation of the phenylisoserine sidechain at the C13 position. Notable differences between the two forms are centered around the rotation axes of O--C13,

Heider, Elizabeth M.

393

Energy transformations early in the bacteriorhodopsin photocycle revealed by DNP-enhanced solid-state NMR  

PubMed Central

By exploiting dynamic nuclear polarization (DNP) at 90 K, we observe the first NMR spectrum of the K intermediate in the ion-motive photocycle of bact