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1

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

PubMed Central

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

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

2010-01-01

2

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

E-print Network

Solid-state NMR spectroscopy (ssNMR) is an extremely powerful technique for the analysis of pharmaceutical dosage forms. A major limitation of ssNMR is the number of samples that can be analyzed in a given period of time. ...

Nelson, Benjamin Nels

2011-12-31

3

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

SciTech Connect

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

Fernandez, Christian; Pruski, Marek

2011-06-08

4

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

5

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

6

Solid-state STRAFI NMR probe for material imaging of quadrupolar nuclei  

NASA Astrophysics Data System (ADS)

Stray field imaging (STRAFI) has provided an alternative imaging method to study solid materials that are typically difficult to obtain using conventional MRI methods. For small volume samples, image resolution is a challenge since extremely strong gradients are required to examine narrow slices. Here we present a STRAFI probe for imaging materials with quadrupolar nuclei. Experiments were performed on a 19.6 T magnet which has a fringe field gradient strength of 72 T/m, nearly 50 times stronger than commercial microimagers. We demonstrate the ability to acquire 7Li 1D profiles of liquid and solid state lithium phantoms with clearly resolved features in the micrometer scale and as a practical example a Li ion battery electrode material is also examined.

Tang, Joel A.; Zhong, Guiming; Dugar, Sneha; Kitchen, Jason A.; Yang, Yong; Fu, Riqiang

2012-12-01

7

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

NASA Astrophysics Data System (ADS)

Water plays an essential role in the structure and function of proteins, lipid membranes and other biological macromolecules. Solid-state NMR heteronuclear-detected 1H polarization transfer from water to biomolecules is a versatile approach for studying water-protein, water-membrane, and water-carbohydrate interactions in biology. We review radiofrequency pulse sequences for measuring water polarization transfer to biomolecules, the mechanisms of polarization transfer, and the application of this method to various biological systems. Three polarization transfer mechanisms, chemical exchange, spin diffusion and NOE, manifest themselves at different temperatures, magic-angle-spinning frequencies, and pulse irradiations. Chemical exchange is ubiquitous in all systems examined so far, and spin diffusion plays the key role in polarization transfer within the macromolecule. Tightly bound water molecules with long residence times are rare in proteins at ambient temperature. The water polarization-transfer technique has been used to study the hydration of microcrystalline proteins, lipid membranes, and plant cell wall polysaccharides, and to derive atomic-resolution details of the kinetics and mechanism of ion conduction in channels and pumps. Using this approach, we have measured the water polarization transfer to the transmembrane domain of the influenza M2 protein to obtain information on the structure of this tetrameric proton channel. At short mixing times, the polarization transfer rates are site-specific and depend on the pH, labile protons, sidechain conformation, as well as the radial position of the residues in this four-helix bundle. Despite the multiple dependences, the initial transfer rates reflect the periodic nature of the residue positions from the water-filled pore, thus this technique provides a way of gleaning secondary structure information, helix tilt angle, and the oligomeric structure of membrane proteins.

Williams, Jonathan K.; Hong, Mei

2014-10-01

8

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

PubMed

Water plays an essential role in the structure and function of proteins, lipid membranes and other biological macromolecules. Solid-state NMR heteronuclear-detected (1)H polarization transfer from water to biomolecules is a versatile approach for studying water-protein, water-membrane, and water-carbohydrate interactions in biology. We review radiofrequency pulse sequences for measuring water polarization transfer to biomolecules, the mechanisms of polarization transfer, and the application of this method to various biological systems. Three polarization transfer mechanisms, chemical exchange, spin diffusion and NOE, manifest themselves at different temperatures, magic-angle-spinning frequencies, and pulse irradiations. Chemical exchange is ubiquitous in all systems examined so far, and spin diffusion plays the key role in polarization transfer within the macromolecule. Tightly bound water molecules with long residence times are rare in proteins at ambient temperature. The water polarization-transfer technique has been used to study the hydration of microcrystalline proteins, lipid membranes, and plant cell wall polysaccharides, and to derive atomic-resolution details of the kinetics and mechanism of ion conduction in channels and pumps. Using this approach, we have measured the water polarization transfer to the transmembrane domain of the influenza M2 protein to obtain information on the structure of this tetrameric proton channel. At short mixing times, the polarization transfer rates are site-specific and depend on the pH, labile protons, sidechain conformation, as well as the radial position of the residues in this four-helix bundle. Despite the multiple dependences, the initial transfer rates reflect the periodic nature of the residue positions from the water-filled pore, thus this technique provides a way of gleaning secondary structure information, helix tilt angle, and the oligomeric structure of membrane proteins. PMID:25228502

Williams, Jonathan K; Hong, Mei

2014-10-01

9

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

10

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

PubMed Central

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

2013-01-01

11

Solid-state NMR and membrane proteins.  

PubMed

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

Opella, Stanley J

2015-04-01

12

Protein Structure from Solid-State NMR  

Microsoft Academic Search

\\u000a This article deals with mathematical questions arising from the determination of protein structure from data obtained by solid-state\\u000a nuclear magnetic resonance (NMR). Solid-state NMR holds the promise of revealing the structure of membrane proteins in a lipid\\u000a bilayer. The derivation of protein structure from NMR data has most often been done using proteins in liquid state, and the\\u000a mathematical analysis

John R. Quine; Timothy A. Cross

2003-01-01

13

REDOR solid-state NMR as a probe of the membrane locations of membrane-associated peptides and proteins.  

PubMed

Rotational-echo double-resonance (REDOR) solid-state NMR is applied to probe the membrane locations of specific residues of membrane proteins. Couplings are measured between protein (13)CO nuclei and membrane lipid or cholesterol (2)H and (31)P nuclei. Specific (13)CO labeling is used to enable unambiguous assignment and (2)H labeling covers a small region of the lipid or cholesterol molecule. The (13)CO-(31)P and (13)CO-(2)H REDOR respectively probe proximity to the membrane headgroup region and proximity to specific insertion depths within the membrane hydrocarbon core. One strength of the REDOR approach is use of chemically-native proteins and membrane components. The conventional REDOR pulse sequence with 100kHz (2)H ? pulses is robust with respect to the (2)H quadrupolar anisotropy. The (2)H T1's are comparable to the longer dephasing times (?'s) and this leads to exponential rather than sigmoidal REDOR buildups. The (13)CO-(2)H buildups are well-fitted to A×(1-e(-)(??)) where A and ? are fitting parameters that are correlated as the fraction of molecules (A) with effective (13)CO-(2)H coupling d=3?/2. The REDOR approach is applied to probe the membrane locations of the "fusion peptide" regions of the HIV gp41 and influenza virus hemagglutinin proteins which both catalyze joining of the viral and host cell membranes during initial infection of the cell. The HIV fusion peptide forms an intermolecular antiparallel ? sheet and the REDOR data support major deeply-inserted and minor shallowly-inserted molecular populations. A significant fraction of the influenza fusion peptide molecules form a tight hairpin with antiparallel N- and C-? helices and the REDOR data support a single peptide population with a deeply-inserted N-helix. The shared feature of deep insertion of the ? and ? fusion peptide structures may be relevant for fusion catalysis via the resultant local perturbation of the membrane bilayer. Future applications of the REDOR approach may include samples that contain cell membrane extracts and use of lower temperatures and dynamic nuclear polarization to reduce data acquisition times. PMID:25797012

Jia, Lihui; Liang, Shuang; Sackett, Kelly; Xie, Li; Ghosh, Ujjayini; Weliky, David P

2015-04-01

14

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

PubMed Central

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

2014-01-01

15

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

PubMed Central

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

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

2009-01-01

16

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

NASA Astrophysics Data System (ADS)

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

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

2009-11-01

17

Solid-State NMR Studies of Bone  

Microsoft Academic Search

Solid-state NMR studies on bone, bone mineral standards and collagen are reviewed. NMR spectroscopy was mostly applied to the bone mineral and confirmed that the structure resembles that of calcium carbonatoapatite of type B. Apatite in bone was found to be deficient in structural hydroxyl groups. Concentration and distribution of hydrogenphosphate and carbonate ions, and of water in apatite crystals

Waclaw Kolodziejski

18

Scalar operators in solid-state NMR  

SciTech Connect

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

Sun, Boqin

1991-11-01

19

Probing physical and chemical changes in cortical bone due to osteoporosis and type 2 diabetes by solid-state NMR  

NASA Astrophysics Data System (ADS)

Approximately 1.5 million fractures occur each year in the U.S. due to osteoporosis, which is characterized by decreased bone mineral density and deterioration of bone micro-architecture. On the other hand, type 2 diabetes also significantly increases fracture risks, despite having a normal or even higher bone mineral density. Solid-state NMR has been applied to bone tissues from normal and disease-inflicted mouse models to study structural and chemical dynamics as the disease progresses. Proton relaxation experiments were performed to measure water populations in the bone matrix and pores. Collagen-bound water has strong influence on bone resilience, while water content in the pores reveals amount and size of pores from micro- to millimeter range. Other biochemical and atomic-scale structural alterations in the mineral and organic phases and their interface were investigated by proton, phosphorus, and carbon NMR spectroscopy. Experiments were designed to individually detect different types of phosphorus environments: near the mineral surface, similar to hydroxyapatite, and deficient of hydrogens due to substitution of the hydroxyl group by other ions. A new method was also developed for accurate quantification of each phosphorus species.

Zhou, Donghua; Taylor, Amanda; Rendina, Beth; Smith, Brenda

2013-03-01

20

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

E-print Network

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

Bajaj, Vikram Singh

2007-01-01

21

Solid state NMR measurements of conformation and conformational  

E-print Network

Solid state NMR measurements of conformation and conformational distributions in the membrane Lansing, MI, USA The solid state NMR lineshape of a protein backbone carbonyl nucleus is a general conformation in the distri- bution. These types of solid state NMR methodologies have been applied

Weliky, David

22

Lithium Polymer Electrolytes and Solid State NMR  

NASA Technical Reports Server (NTRS)

Research is being done at the Glenn Research Center (GRC) developing new kinds of batteries that do not depend on a solution. Currently, batteries use liquid electrolytes containing lithium. Problems with the liquid electrolyte are (1) solvents used can leak out of the battery, so larger, more restrictive, packages have to be made, inhibiting the diversity of application and decreasing the power density; (2) the liquid is incompatible with the lithium metal anode, so alternative, less efficient, anodes are required. The Materials Department at GRC has been working to synthesize polymer electrolytes that can replace the liquid electrolytes. The advantages are that polymer electrolytes do not have the potential to leak so they can be used for a variety of tasks, small or large, including in the space rover or in space suits. The polymers generated by Dr. Mary Ann Meador's group are in the form of rod -coil structures. The rod aspect gives the polymer structural integrity, while the coil makes it flexible. Lithium ions are used in these polymers because of their high mobility. The coils have repeating units of oxygen which stabilize the positive lithium by donating electron density. This aids in the movement of the lithium within the polymer, which contributes to higher conductivity. In addition to conductivity testing, these polymers are characterized using DSC, TGA, FTIR, and solid state NMR. Solid state NMR is used in classifying materials that are not soluble in solvents, such as polymers. The NMR spins the sample at a magic angle (54.7') allowing the significant peaks to emerge. Although solid state NMR is a helpful technique in determining bonding, the process of preparing the sample and tuning it properly are intricate jobs that require patience; especially since each run takes about six hours. The NMR allows for the advancement of polymer synthesis by showing if the expected results were achieved. Using the NMR, in addition to looking at polymers, allows for participation on a variety of other projects, including aero-gels and carbon graphite mat en als. The goals of the polymer electrolyte research are to improve the physical properties of the polymers. This includes improving conductivity, durability, and expanding the temperature range over which it is effective. Currently, good conductivity is only present at high temperatures. My goals are to experiment with different arrangements of rods and coils to achieve these desirable properties. Some of my experiments include changing the number of repeat units in the polymer, the size of the diamines, and the types of coil. Analysis of these new polymers indicates improvement in some properties, such as lower glass transition temperature; however, they are not as flexible as desired. With further research we hope to produce polymers that encompass all of these properties to a high degree.

Berkeley, Emily R.

2004-01-01

23

PROTEIN STRUCTURAL ANALYSIS FROM SOLID STATE NMR DERIVED ORIENTATIONAL CONSTRAINTS  

E-print Network

of a molecule is solved using distance constraints, in solid state NMR, the structure is solved usingPROTEIN STRUCTURAL ANALYSIS FROM SOLID STATE NMR DERIVED ORIENTATIONAL CONSTRAINTS J. R. QUINE provides a great structural analysis problem. Several approaches to this problem have been made in the past

Aluffi, Paolo

24

Solid-State NMR Investigation of Block Copolymer Electrolyte Dynamics  

E-print Network

Solid-State NMR Investigation of Block Copolymer Electrolyte Dynamics D. J. Harris,*, T. J in solid polymer electrolytes. The electrolytic properties of lithium salt-doped poly(ethyl- ene oxide of block copolymers, we have studied these systems by solid-state nuclear magnetic resonance (NMR) line

Sadoway, Donald Robert

25

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

26

Structural studies of amyloid fibrils using solid-state NMR  

E-print Network

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

Caporini, Marc Anthony

2008-01-01

27

Global fold of human cannabinoid type 2 receptor probed by solid-state 13C-, 15N-MAS NMR and molecular dynamics simulations.  

PubMed

The global fold of human cannabinoid type 2 (CB2 ) receptor in the agonist-bound active state in lipid bilayers was investigated by solid-state (13)C- and (15)N magic-angle spinning (MAS) NMR, in combination with chemical-shift prediction from a structural model of the receptor obtained by microsecond-long molecular dynamics (MD) simulations. Uniformly (13)C- and (15)N-labeled CB2 receptor was expressed in milligram quantities by bacterial fermentation, purified, and functionally reconstituted into liposomes. (13)C MAS NMR spectra were recorded without sensitivity enhancement for direct comparison of C?, C?, and C=O bands of superimposed resonances with predictions from protein structures generated by MD. The experimental NMR spectra matched the calculated spectra reasonably well indicating agreement of the global fold of the protein between experiment and simulations. In particular, the (13) C chemical shift distribution of C? resonances was shown to be very sensitive to both the primary amino acid sequence and the secondary structure of CB2. Thus the shape of the C? band can be used as an indicator of CB2 global fold. The prediction from MD simulations indicated that upon receptor activation a rather limited number of amino acid residues, mainly located in the extracellular Loop 2 and the second half of intracellular Loop 3, change their chemical shifts significantly (? 1.5 ppm for carbons and ? 5.0 ppm for nitrogens). Simulated two-dimensional (13) C?(i)-(13)C=O(i) and (13)C=O(i)-(15)NH(i + 1) dipolar-interaction correlation spectra provide guidance for selective amino acid labeling and signal assignment schemes to study the molecular mechanism of activation of CB2 by solid-state MAS NMR. PMID:23999926

Kimura, Tomohiro; Vukoti, Krishna; Lynch, Diane L; Hurst, Dow P; Grossfield, Alan; Pitman, Michael C; Reggio, Patricia H; Yeliseev, Alexei A; Gawrisch, Klaus

2014-03-01

28

Functional groups identified by solid state 13C NMR spectroscopy  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

29

Probing the Transmembrane Structure and Topology of Microsomal Cytochrome-P450 by Solid-State NMR on Temperature-Resistant Bicelles  

PubMed Central

Though the importance of high-resolution structure and dynamics of membrane proteins has been well recognized, optimizing sample conditions to retain the native-like folding and function of membrane proteins for Nuclear Magnetic Resonance (NMR) or X-ray measurements has been a major challenge. While bicelles have been shown to stabilize the function of membrane proteins and are increasingly utilized as model membranes, the loss of their magnetic-alignment at low temperatures makes them unsuitable to study heat-sensitive membrane proteins like cytochrome-P450 and protein-protein complexes. In this study, we report temperature resistant bicelles that can magnetically-align for a broad range of temperatures and demonstrate their advantages in the structural studies of full-length microsomal cytochrome-P450 and cytochrome-b5 by solid-state NMR spectroscopy. Our results reveal that the N-terminal region of rabbit cytochromeP4502B4, that is usually cleaved off to obtain crystal structures, is helical and has a transmembrane orientation with ~17° tilt from the lipid bilayer normal. PMID:23989972

Yamamoto, Kazutoshi; Gildenberg, Melissa; Ahuja, Shivani; Im, Sang-Choul; Pearcy, Paige; Waskell, Lucy; Ramamoorthy, Ayyalusamy

2013-01-01

30

Probing the Transmembrane Structure and Topology of Microsomal Cytochrome-P450 by Solid-State NMR on Temperature-Resistant Bicelles  

NASA Astrophysics Data System (ADS)

Though the importance of high-resolution structure and dynamics of membrane proteins has been well recognized, optimizing sample conditions to retain the native-like folding and function of membrane proteins for Nuclear Magnetic Resonance (NMR) or X-ray measurements has been a major challenge. While bicelles have been shown to stabilize the function of membrane proteins and are increasingly utilized as model membranes, the loss of their magnetic-alignment at low temperatures makes them unsuitable to study heat-sensitive membrane proteins like cytochrome-P450 and protein-protein complexes. In this study, we report temperature resistant bicelles that can magnetically-align for a broad range of temperatures and demonstrate their advantages in the structural studies of full-length microsomal cytochrome-P450 and cytochrome-b5 by solid-state NMR spectroscopy. Our results reveal that the N-terminal region of rabbit cytochromeP4502B4, that is usually cleaved off to obtain crystal structures, is helical and has a transmembrane orientation with ~17° tilt from the lipid bilayer normal.

Yamamoto, Kazutoshi; Gildenberg, Melissa; Ahuja, Shivani; Im, Sang-Choul; Pearcy, Paige; Waskell, Lucy; Ramamoorthy, Ayyalusamy

2013-08-01

31

Solid State NMR and Protein-Protein Interactions in Membranes  

PubMed Central

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

Miao, Yimin; Cross, Timothy A.

2013-01-01

32

Solid-State NMR Spectroscopy for the Physical Chemistry Laboratory  

ERIC Educational Resources Information Center

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

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

2013-01-01

33

Broadband solid-state MAS NMR of paramagnetic systems.  

PubMed

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

Pell, Andrew J; Pintacuda, Guido

2015-02-01

34

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

35

X-ray and high resolution selenium-77 solid state NMR spectroscopy as complementary probes to structural studies of organophosphorus diselenides.  

PubMed

77Se high resolution solid state NMR spectroscopy was employed to study structural properties of bis(diisopropoxyphosphorothioyl) diselenide 1 and bis(dineopentoxyphosphorothioyl) diselenide 2. The principal elements Tii of 77Se effective dipolar/chemical shift tensor were calculated from spinning sideband intensities employing the WIN-MAS program. The values of anisotropy and asymmetry parameters reflect the distortion of the selenium environment. It was found that the T33 component mostly contributes to changes in the isotropic chemical shifts. 77Se CP/MAS experiments were used to decide the assignment of space group by counting the number of crystallographically unique selenium centers in the unit cell. Crystals of diselenide 1 are triclinic, space group P1 with a = 8.485(3) A, b = 8.508(1) A, c = 8.511(2) A, alpha = 98.835(15) degrees, beta = 111.653(24) degrees, gamma = 93.524(21) degrees, V = 559.5(3) A3, Dc = 1.544(2) g/cm3 and Z = 1. Refinement using 2222 reflections for 157 variables gives R = 0.037. Crystals of diselenide 2 are triclinic, space group P1 with a = 9.1418(8) A, b = 9.1465(8) A, c = 9.9200(9) A, alpha = 74.751(8) degrees, beta = 74.629(7) degrees, gamma = 82.216(7) degrees, V = 769.7(1) A3, Dc = 1.365(2) g/cm3 and Z = 1. Refinement using 3316 reflections for 297 variables gives R = 0.0272. PMID:9694390

Potrzebowski, M J; B?aszczyk, J; Majzner, W R; Wieczorek, M W; Baraniak, J; Stec, W J

1998-06-01

36

Solid-State Dipolar INADEQUATE NMR Spectroscopy with a Large Double-Quantum Spectral Width  

E-print Network

Solid-State Dipolar INADEQUATE NMR Spectroscopy with a Large Double-Quantum Spectral Width Mei Hong Academic Press Key Words: solid-state NMR; INADEQUATE; double-quan- tum; C7; dipolar recoupling. Recently, solid-state homonuclear double-quantum NMR spec- troscopy has been increasingly employed to obtain

Hong, Mei

37

SOLID-STATE 3'P NMR SPECTROSCOPY OF BACTERIOPHAGE MI3 AND  

E-print Network

SOLID-STATE 3'P NMR SPECTROSCOPY OF BACTERIOPHAGE MI3 AND TOBACCO MOSAIC VIRUS Pieter Magusin #12;#12;SOLID-STATE 31P NMR SPECTROSCOPY OF BACTERIOPHAGE MI3 AND TOBACCO MOSAIC VIRUS #12;Promotor: dr. T vakgroep Moleculaire Fysica #12;Pieter Magusin SOLID-STATE 31P NMR SPECTROSCOPY OF BACTERIOPHAGE MI3

Hemminga, Marcus A.

38

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

39

Solid-state NMR study of halogen-bonded adducts.  

PubMed

Nuclear magnetic resonance (NMR) spectroscopy offers unique insights into halogen bonds. NMR parameters such as chemical shifts, quadrupolar coupling constants, J coupling constants, and dipolar coupling constants are in principle sensitive to the formation and local structure of a halogen bond. Carrying out NMR experiments on halogen-bonded adducts in the solid state may provide several advantages over solution studies including (1) the absence of solvent which can interact with halogen bond donor sites and complicate spectral interpretation, (2) the lack of a need for single crystals or even long-range crystalline order, and (3) the potential to measure complete NMR interaction tensors rather than simply their isotropic values. In this chapter, we provide an overview of the NMR interactions and experiments which are relevant to the study of nuclei which are often found in halogen bonds (RX···Y) including (13)C, (35/37)Cl, (79/81)Br, (127)I, (77)Se, and (14/15)N. Experimental examples based on iodoperfluorobenzene halides, bis(trimethylammonium)alkane diiodide, and selenocyanate complexes, as well as haloanilinium halides, are discussed. Of particular interest is the sensitivity of the isotropic chemical shifts, the chemical shift tensor spans, and the halide nuclear electric quadrupolar coupling tensors to the halogen bond geometry in such compounds. Technical limitations associated with the NMR spectroscopy of covalently-bonded halogens are underlined. PMID:24760615

Bryce, David L; Viger-Gravel, Jasmine

2015-01-01

40

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

41

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. PMID:20676233

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

42

Solid-State NMR Studies of Chemically Lithiated CF.  

PubMed

Three types of fluorinated carbon, all in their original form and upon sequential chemical lithiations via n-butyllithium, were investigated by (13)C and (19)F solid-state NMR methods. The three starting CF(x) 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 CF(x). Differences were noted in the covalent F character among the starting compounds and in the details of LiF production among the lithiated samples. PMID:20676233

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

43

Solid-state NMR characterization of Mowry Formation shales  

SciTech Connect

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

Miknis, F.P.

1992-04-01

44

Solid-state NMR characterization of Mowry Formation shales  

SciTech Connect

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

Miknis, F.P.

1992-04-01

45

Recrystallized S-layer protein of a probiotic Propionibacterium: structural and nanomechanical changes upon temperature or pH shifts probed by solid-state NMR and AFM.  

PubMed

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

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

2015-01-13

46

Solid State NMR Studies of the Aluminum Hydride Phases  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

47

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

48

Molecular Structure of Humin and Melanoidin via Solid State NMR  

PubMed Central

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

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

2011-01-01

49

Solid-State NMR Determination of 13 CR Chemical Shift Anisotropies  

E-print Network

Solid-State NMR Determination of 13 CR Chemical Shift Anisotropies for the Identification: A solid-state nuclear magnetic resonance (NMR) method for the site-resolved identification of the secondary structure of solid peptides and proteins is presented. This technique exploits the correlation

Hong, Mei

50

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 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 sigma/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 ..pi.. bonding interactions. /sup 31/P and /sup 1/H MASS NMR were applied to the study of lyophilized rat tissue. The /sup 31/P spectra exhibit resonances from phospholipids, DNA, ATP and NAD. The MASS results were compared to chemical analysis data obtained by others and to calculated spectra based on MASS data of model compounds. The /sup 1/H MASS spectra of these tissue samples exhibited lines with widths less than 40 Hz, and were assigned to phospholipid protons. The intensity distribution of the /sup 1/H spectra supported this assignment. Motionally narrowed /sup 31/P and /sup 1/H resonances suggest that the phospholipids undergo varying degrees of motion with correlation times ranging from 0.5 ns to 2 ..mu..s. The degree of hydration of the DNA was also established. 100 refs.

Un, Sun

1987-10-01

51

Strategies for solid-state NMR investigations of supramolecular assemblies with large subunit sizes.  

PubMed

Solid-state NMR is a versatile tool to study structure and dynamics of insoluble and non-crystalline biopolymers. Supramolecular protein assemblies are formed by self-association of multiple copies of single small-sized proteins. Because of their high degree of local order, solid-state NMR spectra of such systems exhibit an unusually high level of resolution, rendering them an ideal target for solid-state NMR investigations. Recently, our group has solved the structure of one particular supramolecular assembly, the type-iii-secretion-system needle. The needle subunit comprises around 80 residues. Many interesting supramolecular assemblies with unknown structure have subunits larger in size, which requires development of tailored solid-state NMR strategies to address their structures. In this "Perspective" article, we provide a view on different approaches to enhance sensitivity and resolution in biological solid-state NMR with a focus on the possible application to supramolecular assemblies with large subunit sizes. PMID:25487122

Fricke, Pascal; Chevelkov, Veniamin; Shi, Chaowei; Lange, Adam

2015-04-01

52

Coherent and stochastic averaging in solid-state NMR  

NASA Astrophysics Data System (ADS)

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

Nevzorov, Alexander A.

2014-12-01

53

Solid-state NMR study of fluorinated steroids.  

PubMed

Solid-state {(1)H}(13)C cross-polarization/magic angle spinning (CP/MAS) NMR spectroscopy was performed to analyze two fluorinated steroids, i.e., betamethasone (BMS) and fludrocortisone acetate (FCA), that have fluorine attached to C9, as well as two non-fluorinated analogs, i.e., prednisolone (PRD) and hydrocortisone 21-acetate (HCA). The (13)C signals of BMS revealed multiplet patterns with splittings of 16-215Hz, indicating multiple ring conformations, whereas the (13)C signals of FCA, HCA, and PRD exhibited only singlet patterns, implying a unique conformation. In addition, BMS and FCA exhibited substantial deviation (>3.5ppm) in approximately half of the (13)C signals and significant deviation (>45ppm) in the (13)C9 signal compared to PRD and HCA, respectively. In this study, we demonstrate that fluorinated steroids, such as BMS and FCA, have steroidal ring conformation(s) that are distinct from non-fluorinated analogs, such as PRD and HCA. PMID:24316163

Yang, Kai-Jay; Lin, Su-Ching; Huang, Shing-Jong; Ching, Wei-Min; Hung, Chen-Hsiung; Tzou, Der-Lii M

2014-02-01

54

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

E-print Network

Solid-State 13C NMR of Liquid Crystalline Polyesters: Variations in Morphology, Alignment, the structures of these polyesters were examined by high-resolution solid-state 13C NMR. It was found that while

Frydman, Lucio

55

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

E-print Network

342 IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 46, NO. 1, JANUARY 2011 Palm NMR and 1-Chip NMR Nan in the palm of a hand, is the smallest NMR system ever built, and is 1200 lighter, 1200 smaller, yet 150 more, such as biomolecular sensing, medical imaging, and oil detection, to name a few. The benefits of NMR would be broadly

Ham, Donhee

56

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

PubMed

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

Jaroniec, Christopher P

2015-04-01

57

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

58

Arabidopsis thalianafrom Polarization Transfer Solid-State NMR  

SciTech Connect

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

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

2014-07-23

59

Solid-State NMR Analysis of Excipients and Drug-Excipient Interactions in the Amorphous State  

E-print Network

Solid-state NMR (SSNMR) experiments were used to investigate numerous aspects of pharmaceutically relevant amorphous materials, such as structure, molecular weight, water content, interactions with other molecules, and ...

Sperger, Diana

2010-08-27

60

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

E-print Network

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

Sparks, Donald L.

61

Methodology and applications of high resolution solid-state NMR to structure determination of proteins  

E-print Network

A number of methodological developments and applications of solid-state NMR for assignment and high resolution structure determination of microcrystalline proteins and amyloid fibrils are presented. Magic angle spinning ...

Lewandowski, Józef Romuald

2008-01-01

62

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

PubMed Central

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

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

2013-01-01

63

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

PubMed Central

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

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

2013-01-01

64

Insights into the structure and dynamics of measles virus nucleocapsids by 1H-detected solid-state NMR.  

PubMed

(1)H-detected solid-state nuclear magnetic resonance (NMR) experiments are recorded on both intact and trypsin-cleaved sedimented measles virus (MeV) nucleocapsids under ultra-fast magic-angle spinning. High-resolution (1)H,(15)N-fingerprints allow probing the degree of molecular order and flexibility of individual capsid proteins, providing an exciting atomic-scale complement to electro microscopy (EM) studies of the same systems. PMID:25140429

Barbet-Massin, Emeline; Felletti, Michele; Schneider, Robert; Jehle, Stefan; Communie, Guillaume; Martinez, Nicolas; Jensen, Malene Ringkjøbing; Ruigrok, Rob W H; Emsley, Lyndon; Lesage, Anne; Blackledge, Martin; Pintacuda, Guido

2014-08-19

65

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

66

Solid state NMR studies of covalent graphite fluorides (CF) n and (C 2F) n  

Microsoft Academic Search

Various covalent graphite fluorides were studied using solid state nuclear magnetic resonance (NMR). 19F magic angle spinning (MAS) NMR, 13C MAS NMR and 13C MAS NMR with 19F to 13C Cross Polarization (CP) allow both the presence of CF and CF2 groups and the carbon atoms hybridization, sp2 or sp3, to be determined. 19F spin–lattice relaxation time T1 of the

Jérôme Giraudet; Marc Dubois; Katia Guérin; André Hamwi; Francis Masin

2006-01-01

67

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

68

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

PubMed Central

NMR spectroscopy of helical membrane proteins has been very challenging on multiple fronts. The expression and purification of these proteins while maintaining functionality has consumed countless graduate student hours. Sample preparations have depended on whether solution or solid-state NMR spectroscopy was to be performed – neither have been easy. In recent years it has become increasingly apparent that membrane mimic environments influence the structural result. Indeed, in these recent years we have rediscovered that Nobel laureate, Christian Anfinsen, did not say that protein structure was exclusively dictated by the amino acid sequence, but rather by the sequence in a given environment (Anfinsen, 1973) [106]. The environment matters, molecular interactions with the membrane environment are significant and many examples of distorted, non-native membrane protein structures have recently been documented in the literature. However, solid-state NMR structures of helical membrane proteins in proteoliposomes and bilayers are proving to be native structures that permit a high resolution characterization of their functional states. Indeed, solid-state NMR is uniquely able to characterize helical membrane protein structures in lipid environments without detergents. Recent progress in expression, purification, reconstitution, sample preparation and in the solid-state NMR spectroscopy of both oriented samples and magic angle spinning samples has demonstrated that helical membrane protein structures can be achieved in a timely fashion. Indeed, this is a spectacular opportunity for the NMR community to have a major impact on biomedical research through the solid-state NMR spectroscopy of these proteins. PMID:24412099

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

2014-01-01

69

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

70

Efficient -Sheet Identification in Proteins by Solid-State NMR Spectroscopy  

E-print Network

Efficient -Sheet Identification in Proteins by Solid-State NMR Spectroscopy Daniel Huster, Satoru: An efficient two-dimensional magic-angle-spinning (MAS) NMR technique to selectively detect -sheet residues-helical and -sheet conformations give rise to distinctly different dipolar modulations. After one-half of a rotation

Hong, Mei

71

CHARACTERIZATION OF SOIL ORGANIC MATTER IN TROPICAL RICE SOILS BY ADVANCED SOLID-STATE NMR  

Technology Transfer Automated Retrieval System (TEKTRAN)

The chemical structures of soil organic matter in a continually submerged, triple-cropped lowland rice soil having large inputs of rice straw and an aerobic dryland rice soil were compared using advanced solid-state nuclear magnetic resonance (NMR) techniques. Quantitative 13C NMR shows that a humi...

72

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

73

Solid-State NMR Studies of Pharmaceutical Systems  

Microsoft Academic Search

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

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

2008-01-01

74

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

PubMed

This article reviews the application of solid-state ²H nuclear magnetic resonance (NMR) spectroscopy for investigating the deformation of lipid bilayers at the atomistic level. For liquid-crystalline membranes, the average structure is manifested by the segmental order parameters (SCD) of the lipids. Solid-state ²H NMR yields observables directly related to the stress field of the lipid bilayer. The extent to which lipid bilayers are deformed by osmotic pressure is integral to how lipid-protein interactions affect membrane functions. Calculations of the average area per lipid and related structural properties are pertinent to bilayer remodeling and molecular dynamics (MD) simulations of membranes. To establish structural quantities, such as area per lipid and volumetric bilayer thickness, a mean-torque analysis of ²H NMR order parameters is applied. Osmotic stress is introduced by adding polymer solutions or by gravimetric dehydration, which are thermodynamically equivalent. Solid-state NMR studies of lipids under osmotic stress probe membrane interactions involving collective bilayer undulations, order-director fluctuations, and lipid molecular protrusions. Removal of water yields a reduction of the mean area per lipid, with a corresponding increase in volumetric bilayer thickness, by up to 20% in the liquid-crystalline state. Hydrophobic mismatch can shift protein states involving mechanosensation, transport, and molecular recognition by G-protein-coupled receptors. Measurements of the order parameters versus osmotic pressure yield the elastic area compressibility modulus and the corresponding bilayer thickness at an atomistic level. Solid-state ²H NMR thus reveals how membrane deformation can affect protein conformational changes within the stress field of the lipid bilayer. PMID:24946141

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

2015-01-01

75

Solid-State NMR/NQR and First-Principles Study of Two Niobium Halide Cluster Compounds  

E-print Network

1 Solid-State NMR/NQR and First-Principles Study of Two Niobium Halide Cluster Compounds Berislav : 10.1016/j.ssnmr.2014.02.001 #12;2 Abstract Two hexanuclear niobium halide cluster compounds solid-state NMR/NQR techniques and PAW/GIPAW calculations. For niobium sites the NMR parameters were

Boyer, Edmond

76

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

PubMed Central

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

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

2013-01-01

77

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

78

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

PubMed

(13)C and (15)N solid-state nuclear magnetic resonance (NMR) spectra were recorded from albendazole (ABZ) and from ABZ:?-cyclodextrin, ABZ:methyl-?-cyclodextrin, ABZ:hydroxypropyl-?-cyclodextrin and ABZ:citrate-?-cyclodextrin, which were prepared by the spray-drying technique. ABZ signals were typical of a crystalline solid for the pure drug and of an amorphous compound obtained from ABZ:cyclodextrin samples. Relevant spectral differences were correlated with chemical interaction between ABZ and cyclodextrins. The number and type of complexes revealed a strong dependence on the cyclodextrin group substituent. Solid-state NMR data were consistent with the presence of stable inclusion complexes. PMID:25843843

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

2015-06-01

79

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

E-print Network

SOLID-STATE NMR STUDIES OF THE ADSORPTION OF ACETYLENE ON PLATINUM/ALUMINA CATALYSTS A Thesis by MARSHA JO LUPHER LAMBREGTS Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE December 1991 Major Subject: Chemistry SOLID-STATE NMR STUDIES OF THE ADSORPTION OF ACETYLENE ON PLATINUM/ALUMINA CATALYSTS A Thesis by MARSHA JO LUPHER LAMBREGTS Approved as to style and content by: ames F. Haw...

Lambregts, Marsha Jo Lupher

1991-01-01

80

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

SciTech Connect

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

Hagaman, Edward {Ed} W [ORNL; Chen, Banghao [ORNL; Jiao, Jian [ORNL; Parsons, Williams [Oak Ridge National Laboratory (ORNL)

2012-01-01

81

Proteorhodopsin: characterisation of 2D crystals by electron microscopy and solid state NMR.  

PubMed

Proteorhodopsin (PR) a recent addition to retinal type 1 protein family, is a bacterial homologue of archaeal bacteriorhodopsin. It was found to high abundance in gamma-proteobacteria in the photic zone of the oceans and has been shown to act as a photoactive proton pump. It is therefore involved in the utilisation of light energy for energy production within the cell. Based on data from biodiversity screens, hundreds of variants were discovered worldwide, which are spectrally tuned to the available light at different locations in the sea. Here, we present a characterisation of 2D crystals of the green variant of proteorhodopsin by electron microscopy and solid state NMR. 2D crystal formation with hexagonal protein packing was observed under a very wide range of conditions indicating that PR might be also closely packed under native conditions. A low-resolution 2D projection map reveals a ring-shaped oligomeric assembly of PR. The protein state was analysed by 15N MAS NMR on lysine, tryptophan and methionine labelled samples. The chemical shift of the protonated Schiff base was almost identical to non-crystalline preparations. All residues could be cross-polarised in non-frozen samples. Lee-Goldberg cross-polarisation has been used to probe protein backbone mobility. PMID:17964280

Shastri, Sarika; Vonck, Janet; Pfleger, Nicole; Haase, Winfried; Kuehlbrandt, Werner; Glaubitz, Clemens

2007-12-01

82

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

PubMed Central

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

Hu, Kan-Nian; Tycko, Robert

2010-01-01

83

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

84

Solid state NMR studies of materials for energy technology  

NASA Astrophysics Data System (ADS)

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

Nambukara Kodiweera Arachchilage, Chandana K.

85

Conformation of Poly(ethylene oxide)-Hydroxybenzene Molecular Complexes Studied by Solid-State NMR  

E-print Network

Conformation of Poly(ethylene oxide)-Hydroxybenzene Molecular Complexes Studied by Solid-State NMR February 16, 2000 ABSTRACT: The conformation of poly(ethylene oxide), PEO, in molecular complexes. Introduction Poly(ethylene oxide), PEO, is a relatively nonpolar polymer but contains ether oxygens

Hong, Mei

86

ANALYSIS OF POTENTIALLY MOBILE PHOSPHORUS IN ARABLE SOILS USING SOLID STATE NMR  

Technology Transfer Automated Retrieval System (TEKTRAN)

In many intensive agroecosystems continued inputs of phosphorus (P) over many years can significantly increase soil P concentrations and the risk of P losses to surface waters. This study used solid-state 31P nuclear magnetic resonance (NMR) spectroscopy (high power decoupled (HPDec)/ magic angle s...

87

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

E-print Network

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

Frydman, Lucio

88

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

89

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

E-print Network

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

Bluemel, Janet

90

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

E-print Network

-stimulated growth of plant cells (2). Auxin, the classical plant growth hormone, rapidly stim- ulates growth in part growth process, plants use expansins to induce wall stress relaxation, which creates the driving forceSensitivity-enhanced solid-state NMR detection of expansin's target in plant cell walls Tuo Wanga

Hong, Mei

91

A Multinuclear Solid-State NMR Analysis of Vitamin B12 in Its Different Polymorphic Forms  

E-print Network

A Multinuclear Solid-State NMR Analysis of Vitamin B12 in Its Different Polymorphic Forms Ales of cyanocobalamin (vitamin B12) polymorphs. These studies involved recrystallizing a series of samples under structures described by Hodgkin and co-workers in their seminal vitamin B12 crystallographic analyses. Most

Frydman, Lucio

92

1H and 13C Solid-state NMR of Gossypium barbadense (Pima) Cotton  

Technology Transfer Automated Retrieval System (TEKTRAN)

The interaction of water with cellulose and its influence on the nuclear spin dynamics in G. barbadense (Pima) cotton were investigated by 1H and 13C solid-state NMR techniques. 1H spin diffusion results from a Goldman-Shen experiment indicate that the water is multilayered. 1H MAS experiments pro...

93

Investigation of Moisture Interaction with Cellulose Using Solid-State NMR  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

94

NMR Studies of the Effect of Adsorbed Water on Polyelectrolyte Multilayer Films in the Solid State  

E-print Network

NMR Studies of the Effect of Adsorbed Water on Polyelectrolyte Multilayer Films in the Solid State of the adsorbed water and polymer components in polyelectrolyte multilayer (PEM) films and the bulk component and to the surface layer. 1. Introduction Polyelectrolyte multilayer films have received con

Barrett, Christopher

95

Z .Solid State Nuclear Magnetic Resonance 11 1998 139156 SQUID detected NMR and NQR  

E-print Network

Z .Solid State Nuclear Magnetic Resonance 11 1998 139­156 SQUID detected NMR and NQR Matthew P dc Superconducting QUantum Interference Device SQUID is a sensitive detector of magnetic flux to a thin film superconducting coil deposited on the SQUID to form a flux transformer. With this untuned

Augustine, Mathew P.

96

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

E-print Network

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

Bluemel, Janet

97

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

ERIC Educational Resources Information Center

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

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

2014-01-01

98

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

99

Synthesis, Enhanced Fusogenicity, and Solid State NMR Measurements of Cross-Linked HIV-1 Fusion Peptides  

E-print Network

Synthesis, Enhanced Fusogenicity, and Solid State NMR Measurements of Cross-Linked HIV-1 Fusion or trimers. C-terminal trimerization is their likely topology in the fusogenic form of the intact gp41 protein. The fusogenicity of the peptides was then measured in an intervesicle lipid mixing assay

Weliky, David

100

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

PubMed Central

We used solid-state NMR techniques to probe the interactions of cholesterol (Chol) with bovine brain sphingomyelin (SM) and for comparison of the interactions of Chol with dipalmitoylphosphatidylcholine (DPPC), which has a similar gel-to-liquid crystalline transition temperature. (1)H-, (31)P-, and (13)C-MASNMR yielded high-resolution spectra from multilamellar dispersions of unlabeled brain SM and Chol for analysis of chemical shifts and linewidths. In addition, (2)H-NMR spectra of oriented lipid membranes with specific deuterium labels gave information about membrane ordering and mobility. Chol disrupted the gel-phase of pure SM and increased acyl chain ordering in the liquid crystalline phase. As inferred from (13)C chemical shifts, the boundaries between the ordered and disordered liquid crystalline phases (L and L) were similar for SM and DPPC. The solubility limit of Chol in SM was ~50 mol %, the same value as previously reported for DPPC membranes. We found no evidence for specific H-bonding between Chol and the amide group of SM. The order parameters of a probe molecule, d31-sn1-DPPC, in SM were slightly higher than in DPPC for all carbons except the terminal groups at 30 mol % but were not significantly different at 5 and 60 mol % Chol. These studies show a general similarity with some subtle differences in the way Chol interacts with DPPC and SM. In the environment of a typical biomembrane, the higher proportion of saturated fatty acyl chains in SM compared to other phospholipids may be the most significant factor influencing interactions with Chol. PMID:12202372

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

2002-01-01

101

Spectral editing of two-dimensional magic-angle-spinning solid-state NMR spectra for protein resonance assignment  

E-print Network

ARTICLE Spectral editing of two-dimensional magic-angle-spinning solid-state NMR spectra % for the CH selection experiment, and are demon- strated on well-characterized model proteins GB1 Recent progress in magic-angle-spinning (MAS) solid-state NMR (SSNMR) spectroscopy has made it possible

Hong, Mei

102

Asymmetric Insertion of Membrane Proteins in Lipid Bilayers by Solid-State NMR Paramagnetic Relaxation Enhancement: A  

E-print Network

Asymmetric Insertion of Membrane Proteins in Lipid Bilayers by Solid-State NMR Paramagnetic@iastate.edu Abstract: A novel solid-state NMR technique for identifying the asymmetric insertion depths of membrane to a cell-penetrating peptide, penetratin, we found that at low peptide concentrations, penetratin

Hong, Mei

103

Broadband solid-state MAS NMR of paramagnetic systems  

E-print Network

paramagnetic benchmark material The chosen paramagnetic system to illustrate the various concepts and properties of the broadband NMR sequences is the olivine LiFe0.5Mn0.5PO4, which is a cathode ma- terial [40, 41], comprising TMO6 octahedra and PO4 tetrahedra... .5Mn0.5PO4. The olivine crystal structure is shown in (a) showing the TMO6 octahedra, PO4 tetrahedra, and one-dimensional channels occupied by Li. In (b) is shown the local structure of the P site, which is coordinating to five transition-metal ion...

Pell, Andrew J.; Pintacuda, Guido

2014-12-26

104

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

105

Can one and two-dimensional solid-state NMR fingerprint zeolite framework topology?  

PubMed

In this contribution, we have explored the potential and strength of one-dimensional (1D) (29)Si and two-dimensional (2D) (29)S-(29)Si and (29)Si-(17)O NMR as invariants of non-oriented graph for fingerprinting zeolite frameworks. 1D and 2D (29)Si NMR can indeed provide indications on the graph vertices, edges and allow the construction of the adjacency matrix, i.e. the set of connections between the graph vertices. From the structural data, hypothetical 1D (29)Si and 2D (29)Si-(29)Si NMR signatures for 193 of the zeolite frameworks reported in the Atlas of Zeolite Structures have been generated. Comparison between all signatures shows that thanks to the 1D (29)Si NMR data only, almost 20% of the known zeolite frameworks could be distinguished. Further NMR signatures were generated by taking into account 2D (29)Si-(29)Si and (29)Si-(17)O correlations. By sorting and comparison of all the NMR data, up to 80% of the listed zeolites could be unambiguously discriminated. This work indicates that (i) solid-state NMR data indeed represent a rather strong graph invariant for zeolite framework, (ii) despite their difficulties and costs (isotopic labeling is often required, the NMR measurements can be long), (29)Si and (17)O NMR measurements are worth being investigated in the frame of zeolites structure resolution. This approach could also be generalized to other zeolite-related materials containing NMR-measurable nuclides. PMID:25454465

Martineau, Charlotte; Vial, Sandrine; Barth, Dominique; Quessette, Franck; Taulelle, Francis

2015-02-01

106

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

107

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

108

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

SciTech Connect

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

Gao, A.; Heck, R.W.

2008-01-01

109

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

PubMed Central

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

2013-01-01

110

Solid state NMR and pair distribution function studies of silicon electrodes for lithium-ion batteries  

NASA Astrophysics Data System (ADS)

The universally used negative electrode material in a LIB is carbon, because of its moderate capacity (372 mAhg-1 for graphite), cyclability and high rate capability. However, new, low cost, safe electrode materials with higher capacities are still urgently required for both portable and transportation applications. Silicon anodes are particularly attractive alternatives to carbon with extremely high gravimetric energy densities (3572 mAhg-1). Compared to graphite, silicon has a massive volumetric capacity of 8322 mAhcm-3 (calculated based on the original volume of silicon) which is approximately ten times that graphite. At room temperature, upon electrochemical lithiation, silicon undergoes a crystalline to amorphous phase transition forming a lithiated amorphous silicide phase. Unfortunately, due to the amorphous nature of the lithiated silicides, it is not possible to monitor all the structural changes that occur during lithium insertion/removal with conventional methods such as diffraction. The short range order of the amorphous materials remains unknown, preventing attempts to optimize performance based on electrochemical-structure correlations. In this work, a combination of local structure probes, ex-situ 7Li nuclear magnetic resonance (NMR) studies and pair distribution function (PDF) analysis of X-ray data was applied to investigate the changes in short range order that occur during the initial charge and discharge cycles. The distinct electrochemical profiles observed subsequent to the 1 st discharge have been shown to be associated with the formation of distinct amorphous lithiated silicide structures. A (de)lithiation model consisting of four different mechanisms, each being valid for regions of the charge or discharge process is proposed to explain the hysteresis and the steps in the electrochemical profile observed during lithiation and delithiation of Si. A spontaneous reaction of the fully lithiated lithium silicide with the electrolyte is directly observed in the in situ NMR experiments; this mechanism results in self-discharge, and potentially capacity loss. The rate of this self-discharge process is much slower when CMC (carboxymethylcellulose) is used as the binder. Previous work has shown that the electrochemical performance of nanoparticulate crystalline silicon is different from the bulk. The lithiation and delithiation mechanisms of nano-Si for lithium ion batteries are studied by using ex-situ solid state MAS NMR and PDF analysis. The main differences vs. bulk lithiation and delithiation are identified by characterizing the amorphous phases formed.

Key, Baris

111

Preparation of protein nanocrystals and their characterization by solid state NMR  

NASA Astrophysics Data System (ADS)

Preparation of proteins in their crystalline state has been found to be important in producing stable therapeutic protein formulations, cross-linked enzyme crystals for application in industrial processes, generating novel porous media for separations, and of course in structure elucidation. Of these applications only X-ray crystallography requires large crystals, defined here as being crystals 100s of microns or greater in size. Smaller crystals have attractive attributes in many instances, and are just as useful in structure determination by solid state NMR (ssNMR) as are large crystals. In this paper we outline a simple set of procedures for preparing nanocrystalline protein samples for ssNMR or other applications and describe the characterization of their crystallinity by ssNMR and X-ray powder diffraction. The approach is demonstrated in application to five different proteins: ubiquitin, lysozyme, ribonuclease A, streptavidin, and cytochrome c. In all instances the nanocrystals produced are found to be highly crystalline as judged by natural abundance 13C ssNMR and optical and electron microscopy. We show for ubiquitin that nanocrystals prepared by rapid batch crystallization yield equivalent 13C ssNMR spectra to those of larger X-ray diffraction quality crystals. Single crystal and powder X-ray diffraction measurements are made to compare the degree of order present in polycrystalline, nanocrystalline, and lyophilized ubiquitin. Solid state 13C NMR is also used to show that ubiquitin nanocrystals are thermally robust, giving no indication of loss of local order after repeated temperature cycling between liquid nitrogen and room temperature. The methods developed are rapid and should scale well from the tenths of milligram to multi-gram scales, and as such should find wide utility in the preparation of protein nanocrystals for applications in catalysis, separations, and especially in sample preparation for structural studies using ssNMR.

Martin, Rachel W.; Zilm, Kurt W.

2003-11-01

112

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

113

Hydrogen-Bonding Interactions in T-2 Toxin Studied Using Solution and Solid-State NMR  

PubMed Central

The structure of T-2 toxin in the solid-state is limited to X-ray crystallographic studies, which lack sufficient resolution to provide direct evidence for hydrogen-bonding interactions. Furthermore, its solution-structure, despite extensive Nuclear Magnetic Resonance (NMR) studies, has provided little insight into its hydrogen-bonding behavior, thus far. Hydrogen-bonding interactions are often an important part of biological activity. In order to study these interactions, the structure of T-2 toxin was compared in both the solution- and solid-state using NMR Spectroscopy. It was determined that the solution- and solid-state structure differ dramatically, as indicated by differences in their carbon chemical shifts, these observations are further supported by solution proton spectral parameters and exchange behavior. The slow chemical exchange process and cross-relaxation dynamics with water observed between the hydroxyl hydrogen on C-3 and water supports the existence of a preferential hydrogen bonding interaction on the opposite side of the molecule from the epoxide ring, which is known to be essential for trichothecene toxicity. This result implies that these hydrogen-bonding interactions could play an important role in the biological function of T-2 toxin and posits towards a possible interaction for the trichothecene class of toxins and the ribosome. These findings clearly illustrate the importance of utilizing solid-state NMR for the study of biological compounds, and suggest that a more detailed study of this whole class of toxins, namely trichothecenes, should be pursued using this methodology. PMID:22069698

Chaudhary, Praveen; Shank, Roxanne A.; Montina, Tony; Goettel, James T.; Foroud, Nora A.; Hazendonk, Paul; Eudes, François

2011-01-01

114

Revealing molecular self-assembly and geometry of non-covalent halogen bonding by solid-state NMR spectroscopyw  

E-print Network

structures for which single crystal X-ray diffraction data are not available. Benzyl-di(4-iodobenzyl. This prompted us to use solid- state NMR spectroscopy. So far the formation of halogen- bonded complexes has

115

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

116

Solid state NMR imaging of irreducible water in reservoir cores for spatially resolved pore surface relaxation estimation.  

PubMed

The use of solid state NMR imaging in reservoir core applications has long been proposed. This paper describes the use of a simple, robust technique in the first such application. One- and two-dimensional images of the irreducible brine in a sandstone and carbonate reservoir core are demonstrated. The applicability of solid state NMR imaging to pore surface relaxation estimation is discussed. PMID:8170338

Attard, J J; McDonald, P J; Roberts, S P; Taylor, T

1994-01-01

117

Application and Reliability of Solid-State NMR in Environmental Sciences  

NASA Astrophysics Data System (ADS)

For the characterization of soil organic matter, a suite of analytical approaches are available. Chemical degradative methods involve an extraction scheme with which the soluble part of the mixture is isolated and analyzed by colorimetrical or chromatographic means. Macromolecular structures can be subjected to thermolytic or combined thermochemolytic degradation. Because secondary reactions (rearrangement, cracking, hydrogenation and polymerization) in a heterogeneous mixture cannot be excluded, it is obvious that conclusions regarding the original structure in the macromolecular phase have to be drawn with caution. A powerful alternative represents solid-state nuclear magnetic resonance (NMR) spectroscopy, allowing the examination of the bulk sample without major pre-treatment In environmental sciences, this technique mostly involves the isotope 13C to study the chemical composition of organic matter in soils, sediments or compost to study the temporal development of humic material or chemical alterations due to variation in environmental parameters. Due to its low sensibility solid-state 15N NMR studies on such samples are only found occasionally. The emphasis of solid-state NMR spectroscopy is not only to determine the gross chemical composition of the material under study via a chemical shift assignment but also a quantitative correlation between the different signal intensities and the relative contribution of the respective C or N types to the total organic C or N content. However, despite increasing popularity, this approach is still viewed as mysterious techniques, in particular with respect to quantification. Accordingly, the purpose of this review is to give a short overview on the possibilities and limitations of this technique in environmental science and in particular for the study of soil organic matter. In general, solid-state 13C NMR spectra of soil organic matter are obtained with the cross polarization magic angle spinning (CPMAS) technique. This technique increases the sensitivity of 13C by magnetization transfer from the 1H to the 13C spin system during a contact time tc. However, one has to bear in mind that some molecular properties may obscure quantification. Thus, for carbons with large C-H internuclear distances (bigger than four bonds, i.e in graphite structures) and for C in groups with high molecular mobility (i.e. gas) the proton-dipolar interactions are weakened and the polarization transfer may be incomplete. The observed intensity can also be affected by interactions of the protons with paramagnetic compounds. To circumvent this problem, the samples are often demineralized with hydrofluoric acid. Alternatively, the Bloch decay, a technique in which the 13C is directly excited is used. Here, on the other hand, one has to consider long relaxation times which may lead to saturation effects. Nevertheless, as it will be discussed within the presentation those quantification problems can be solved for most soil samples and then solid-state NMR spectroscopy represents a powerful tool for qualitative and quantitative analysis. Special techniques, such as dipolar dephasing or the proton spin relaxation editing can be used to extract additional information about chemical properties or mobility. A more detailed examination of the cross polarization behavior can be used to analyze the interaction of organic matter and paramagnetics but also for obtaining revealing properties on a molecular level. Applications involving isotopic labeling combined with both 13C and/or 15N NMR allows to follow the fate of a specific compound i.e. in a natural matrix and- if the enrichment is high enough - the use of 2D solid-state NMR techniques. In particular with respect to environmental chemistry, this combination of isotopic labeling with the use of corresponding NMR spectroscopy shows great potential for a better understanding of the kind of interaction between pollutants and natural organic matter.

Knicker, Heike

2010-05-01

118

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

119

Characterization of microbial poly (?- L-lysine) by FT-IR, Raman and solid state 13C NMR spectroscopies  

NASA Astrophysics Data System (ADS)

The molecular structure and conformation of microbial poly(?- L-lysine) (M-?-PL) produced by a variant of Streptomyces albulus were studied by means of FT-IR, FT-Raman and solid-state 13C NMR spectroscopies. Vibrational results indicate that M-?-PL assumes a ?-sheet conformation in the solid state. Solid state 13C NMR spectra of the crystalline and the amorphous components were observed separately and the degree of crystallinity was estimated to be 63%. A plausible conformation model was proposed.

Maeda, Shiro; Kunimoto, Ko-Ki; Sasaki, Chizuru; Kuwae, Akio; Hanai, Kazuhiko

2003-07-01

120

Solid-state NMR of the Yersinia pestis outer membrane protein Ail in lipid bilayer nanodiscs sedimented by ultracentrifugation.  

PubMed

Solid-state NMR studies of sedimented soluble proteins has been developed recently as an attractive approach for overcoming the size limitations of solution NMR spectroscopy while bypassing the need for sample crystallization or precipitation (Bertini et al. Proc Natl Acad Sci USA 108(26):10396-10399, 2011). Inspired by the potential benefits of this method, we have investigated the ability to sediment lipid bilayer nanodiscs reconstituted with a membrane protein. In this study, we show that nanodiscs containing the outer membrane protein Ail from Yersinia pestis can be sedimented for solid-state NMR structural studies, without the need for precipitation or lyophilization. Optimized preparations of Ail in phospholipid nanodiscs support both the structure and the fibronectin binding activity of the protein. The same sample can be used for solution NMR, solid-state NMR and activity assays, facilitating structure-activity correlation experiments across a wide range of timescales. PMID:25578899

Ding, Yi; Fujimoto, L Miya; Yao, Yong; Marassi, Francesca M

2015-04-01

121

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

122

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

123

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

SciTech Connect

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

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

2010-02-17

124

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

PubMed

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

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

2015-01-01

125

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

NASA Astrophysics Data System (ADS)

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

Filip, Xenia; Tripon, Carmen; Borodi, Gheorghe; Oprean, Lumini?a; Filip, Claudiu

2009-08-01

126

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

127

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

E-print Network

Orientation and Dynamics of an Antimicrobial Peptide in the Lipid Bilayer by Solid-State NMR of Microbiology, University of Iowa College of Medicine, Iowa City, Iowa 52242 USA ABSTRACT The orientation-spectrum bactericidal activity. 15 N NMR spectra of oriented ovispirin reconstituted into synthetic phospholipids show

Hong, Mei

128

A solid-state NMR investigation of the structure of mesoporous silica nanoparticle supported rhodium catalysts  

SciTech Connect

A detailed study of the chemical structure of mesoporous silica catalysts containing rhodium ligands and nanoparticles (RhP-MSN) was carried out by multi-dimensional solid-state NMR techniques. The degree of functionalization of the rhodium-phosphinosilyl complex to the surface of the RhP-MSN channels was determined by {sup 29}Si NMR experiments. The structural assignments of the rhodium-phosphinosilyl complex were unambiguously determined by employing the novel, indirectly detected heteronuclear correlation ({sup 13}C-{sup 1}H and {sup 31}P-{sup 1}H idHETCOR) techniques, which indicated that oxidation of the attached phosphinosilyl groups and detachment of Rh was enhanced upon syngas conversion.

Rapp, Jennifer; Huang, Yulin; Natella, Michael; Cai, Yang; Lin, Victor S.-Y.; Pruski, Marek

2009-01-04

129

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

NASA Astrophysics Data System (ADS)

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 C13 and N15 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

2009-04-01

130

Labeling strategies for 13C-detected aligned-sample solid-state NMR of proteins  

NASA Astrophysics Data System (ADS)

13C-detected solid-state NMR experiments have substantially higher sensitivity than the corresponding 15N-detected experiments on stationary, aligned samples of isotopically labeled proteins. Several methods for tailoring the isotopic labeling are described that result in spatially isolated 13C sites so that dipole-dipole couplings among the 13C are minimized, thus eliminating the need for homonuclear 13C- 13C decoupling in either indirect or direct dimensions of one- or multi-dimensional NMR experiments that employ 13C detection. The optimal percentage for random fractional 13C labeling is between 25% and 35%. Specifically labeled glycerol and glucose can be used at the carbon sources to tailor the isotopic labeling, and the choice depends on the resonances of interest for a particular study. For investigations of the protein backbone, growth of the bacteria on [2- 13C]-glucose-containing media was found to be most effective.

Filipp, Fabian V.; Sinha, Neeraj; Jairam, Lena; Bradley, Joel; Opella, Stanley J.

2009-12-01

131

Intergrowth and interfacial structure of biomimetic fluorapatite-gelatin nanocomposite: a solid-state NMR study.  

PubMed

The model system fluorapatite-gelatin allows mimicking the formation conditions on a lower level of complexity compared to natural dental and bone tissues. Here, we report on solid-state NMR investigations to examine the structure of fluorapatite-gelatin nanocomposites on a molecular level with particular focus on organic-inorganic interactions. Using (31)P, (19)F, and (1)H MAS NMR and heteronuclear correlations, we found the nanocomposite to consist of crystalline apatite-like regions (fluorapatite and hydroxyfluorapatite) in close contact with a more dissolved (amorphous) layer containing first motifs of the apatite crystal structure as well as the organic component. A scheme of the intergrowth region in the fluorapatite-gelatin nanocomposite, where mineral domains interact with organic matrix, is presented. PMID:24354406

Vyalikh, Anastasia; Simon, Paul; Rosseeva, Elena; Buder, Jana; Kniep, Rüdiger; Scheler, Ulrich

2014-01-23

132

Solid-state (17) o NMR spectroscopy of paramagnetic coordination compounds.  

PubMed

High-quality solid-state (17) O (I=5/2) NMR spectra can be successfully obtained for paramagnetic coordination compounds in which oxygen atoms are directly bonded to the paramagnetic metal centers. For complexes containing V(III) (S=1), Cu(II) (S=1/2), and Mn(III) (S=2) metal centers, the (17) O isotropic paramagnetic shifts were found to span a range of more than 10?000?ppm. In several cases, high-resolution (17) O NMR spectra were recorded under very fast magic-angle spinning (MAS) conditions at 21.1?T. Quantum-chemical computations using density functional theory (DFT) qualitatively reproduced the experimental (17) O hyperfine shift tensors. PMID:25694203

Kong, Xianqi; Terskikh, Victor V; Khade, Rahul L; Yang, Liu; Rorick, Amber; Zhang, Yong; He, Peng; Huang, Yining; Wu, Gang

2015-04-13

133

A solid-state 55Mn NMR spectroscopy and DFT investigation of manganese pentacarbonyl compounds  

SciTech Connect

Central transition 55Mn NMR spectra of several solid manganese pentacarbonyls acquired at magnetic field strengths of 11.75, 17.63, and 21.1 T are presented. The variety of distinct powder sample lineshapes obtained demonstrates the sensitivity of solid-state 55Mn NMR to the local bonding environment, including the presence of crystallographically unique Mn sites, and facilitates the extraction of the Mn chemical shift anisotropies, CSAs, and the nuclear quadrupolar parameters. The compounds investigated include molecules with approximate C4v symmetry, LMn(CO)5 (L ¼ Cl, Br, I, HgMn(CO)5, CH3) and several molecules of lower symmetry (L ¼ PhCH2, Ph3*nClnSn (n ¼ 1, 2, 3)). For these compounds, the Mn CSA values range from o100 ppm for Cl3SnMn(CO)5 to 1260 ppm for ClMn(CO)5. At 21.1 T the 55Mn NMR lineshapes are appreciably influenced by the Mn CSA despite the presence of significant 55Mn quadrupolar coupling constants that range from 8.0 MHz for Cl3SnMn(CO)5 to 35.0 MHz for CH3Mn(CO)5. The breadth of the solid-state 55Mn NMR spectra of the pentacarbonyl halides is dominated by the CSA at all three applied magnetic fields. DFT calculations of the Mn magnetic shielding tensors reproduce the experimental trends and the magnitude of the CSA is qualitatively rationalized using a molecular orbital, MO, interpretation based on Ramsey’s theory of magnetic shielding. In addition to the energy differences between symmetry-appropriate occupied and virtual MOs, the d-character of the Mn MOs is important for determining the paramagnetic shielding contribution to the principal components of the magnetic shielding tensor.

Feindel, Kirk W.; Ooms, Kristopher J.; Wasylishen, Roderick E.

2007-01-23

134

Peptide Conformation and Supramolecular Organization in Amylin Fibrils: Constraints from Solid State NMR  

PubMed Central

The 37-residue amylin peptide, also known as islet amyloid polypeptide, forms fibrils that are the main peptide or protein component of amyloid that develops in the pancreas of type 2 diabetes patients. Amylin also readily forms amyloid fibrils in vitro that are highly polymorphic under typical experimental conditions. We describe a protocol for the preparation of synthetic amylin fibrils that exhibit a single predominant morphology, which we call a striated ribbon, in electron microscope and atomic force microscope images. Solid state nuclear magnetic resonance (NMR) measurements on a series of isotopically labeled samples indicate a single molecular structure within the striated ribbons. We use scanning transmission electron microscopy and several types of one-dimensional and two-dimensional solid state NMR techniques to obtain constraints on the peptide conformation and supramolecular structure in these amylin fibrils, and derive molecular structural models that are consistent with the experimental data. The basic structural unit in amylin striated ribbons, which we call the protofilament, contains four-layers of parallel ?-sheets, formed by two symmetric layers of amylin molecules. The molecular structure of amylin protofilaments in striated ribbons closely resembles the protofilament in amyloid fibrils with similar morphology formed by the 40-residue ?-amyloid peptide that is associated with Alzheimer's disease. PMID:17979302

Luca, Sorin; Yau, Wai-Ming; Leapman, Richard; Tycko, Robert

2008-01-01

135

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

PubMed Central

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

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

1996-01-01

136

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

NASA Astrophysics Data System (ADS)

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

Johnson, Robert L.; Schmidt-Rohr, Klaus

2014-02-01

137

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

PubMed

Unilateral and solid-state nuclear magnetic resonance (NMR) analyses were performed on a parchment fragment of the Dead Sea Scroll (DSS). The analyzed sample belongs to the collection of non-inscribed and nontreated fragments of known archaeological provenance from the John Rylands University Library in Manchester. Therefore, it can be considered as original DSS material free from any contamination related to the post-discovery period. Considering the paramount significance of the DSS, noninvasive approaches and portable in situ nondestructive methods are of fundamental importance for the determination of composition, structure, and chemical-physical properties of the materials under study. NMR studies reveal low amounts of water content associated with very short proton relaxation times, T(1), indicating a high level of deterioration of collagen molecules within scroll fragments. In addition, (13)C cross-polarization magic-angle-spinning (CPMAS) NMR spectroscopy shows characteristic peaks of lipids whose presence we attribute to the production technology that did not involve liming. Extraction with chloroform led to the reduction of both lipid and protein signals in the (13)C CPMAS spectrum indicating probable involvement of lipids in parchment degradation processes. NMR absorption and relaxation measurements provide nondestructive, discriminative, and sensitive tools for studying the deterioration effects on the organization and properties of water and collagen within ancient manuscripts. PMID:21805064

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

2012-02-01

138

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

139

Topological, geometric, and chemical order in materials: insights from solid-state NMR.  

PubMed

Unlike the long-range order of ideal crystalline structures, local order is an intrinsic characteristic of real materials and often serves as the key to the tuning of their properties and their final applications. Although researchers can easily assess local ordering using two-dimensional imaging techniques with resolution that approaches the atomic level, the diagnosis, description, and qualification of local order in three dimensions is much more challenging. Solid-state nuclear magnetic resonance (NMR) and its panel of continually developing instruments and methods enable the local, atom-selective characterization of structures and assemblies ranging from the atomic to the nanometer length scales. By making use of the indirect J-coupling that distinguishes chemical bonds, researchers can use solid-state NMR to characterize a variety of materials, ranging from crystalline compounds to amorphous or glassy materials. In crystalline compounds showing some disorder, we describe and distinguish the contributions of topology, geometry, and local chemistry in ways that are consistent with X-ray diffraction and computational approaches. We give examples of materials featuring either chemical disorder in a topological order or topological disorder with local chemical order. For glasses, we show that we can separate geometric and chemical contributions to the local order by identifying structural motifs with a viewpoint that extends from the atomic scale up to the nanoscale. As identified by solid state NMR, the local structure of amorphous materials or glasses consists of well-identified structural entities up to at least the nanometer scale. Instead of speaking of disorder, we propose a new description for these structures as a continuous assembly of locally defined structures, an idea that draws on the concept of locally favored structures (LFS) introduced by Tanaka and coworkers. This idea provides a comprehensive picture of amorphous structures based on fluctuations of chemical composition and structure over different length scales. We hope that these local or molecular insights will allow researchers to consider key questions related to nucleation and crystallization, as well as chemically (spinodal decomposition) or density-driven (polyamorphism) phase separation, which could lead to future applications in a variety of materials. PMID:23883113

Massiot, Dominique; Messinger, Robert J; Cadars, Sylvian; Deschamps, Michaël; Montouillout, Valerie; Pellerin, Nadia; Veron, Emmanuel; Allix, Mathieu; Florian, Pierre; Fayon, Franck

2013-09-17

140

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

PubMed

Membrane composition is a key factor that regulates the destructive activity of antimicrobial peptides and the non-leaky permeation of cell penetrating peptides in vivo. Hence, the choice of model membrane is a crucial aspect in NMR studies and should reflect the biological situation as closely as possible. Here, we explore the structure and dynamics of the short multifunctional peptide BP100 using a multinuclear solid-state NMR approach. The membrane alignment and mobility of this 11 amino acid peptide was studied in various synthetic lipid bilayers with different net charge, fluidity, and thickness, as well as in native biomembranes harvested from prokaryotic and eukaryotic cells. (19)F-NMR provided the high sensitivity and lack of natural abundance background that are necessary to observe a labelled peptide even in protoplast membranes from Micrococcus luteus and in erythrocyte ghosts. Six selectively (19)F-labeled BP100 analogues gave remarkably similar spectra in all of the macroscopically oriented membrane systems, which were studied under quasi-native conditions of ambient temperature and full hydration. This similarity suggests that BP100 has the same surface-bound helical structure and high mobility in the different biomembranes and model membranes alike, independent of charge, thickness or cholesterol content of the system. (31)P-NMR spectra of the phospholipid components did not indicate any bilayer perturbation, so the formation of toroidal wormholes or micellarization can be excluded as a mechanism of its antimicrobial or cell penetrating action. However, (2)H-NMR analysis of the acyl chain order parameter profiles showed that BP100 leads to considerable membrane thinning and thereby local destabilization. PMID:25616492

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

2015-04-01

141

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

142

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

143

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

E-print Network

VARIABLE-TEMPERATURE SOLID-STATE NMR STUDIES OF IRON(II) AND IRON(III) COMPLEXES A Thesis by PATRICIA ARLENE SHEPARD Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE August 1989 Major Subject: Chemistry VARIABLE-TEMPERATURE SOLID-STATE NMR STUDIES OF IRON(II) AND IRON(III) COMPLEXES A Thesis by PATRICIA ARLENE SHEPARD Approved as to style and content by: g, ( James F. Haw (Chair...

Shepard, Patricia Arlene

1989-01-01

144

Structure and orientation of dynorphin bound to lipid bilayers by 13C solid-state NMR  

NASA Astrophysics Data System (ADS)

Secondary structure and orientation of dynorphin bound to dimyristoylphosphatidylcholine (DMPC) bilayer were investigated by solid-state 13C NMR spectroscopy. For this purpose, 13C NMR spectra of the site-specifically 13C-labeled dynorphin were measured in the membrane-bound state under static, magic angle spinning (MAS), and slow MAS conditions. In the static experiment, magnetically oriented vesicle system (MOVS) induced by dynorphin was successfully used to investigate the orientation of dynorphin bound to the lipid bilayers. It was found that dynorphin adopts an ?-helical structure in the N-terminus from Gly 2 to Leu 5 by analyses of the isotropic chemical shifts obtained from the MAS experiments. In contrast, it adopts disordered conformations from the center to the C-terminus and is located on the membrane surface. The static 13C NMR spectra indicated that MOVS-bound dynorphin was oriented to the magnetic field and rotated rapidly about the bilayer normal. Subsequently, we analyzed the 13C chemical shift tensors of carbonyl carbons in the peptide backbone by considering the rotational motion of the N-terminal ?-helix. It was revealed that the N-terminal ?-helix is inserted into the membrane with the tilt angle of 21° to the bilayer normal. This structure suggests a possibility that dynorphin interacts with the extracellular loop II of the ?-receptor through a helix-helix interaction.

Uezono, Takiko; Toraya, Shuichi; Obata, Maki; Nishimura, Katsuyuki; Tuzi, Satoru; Saitô, Hazime; Naito, Akira

2005-07-01

145

Paramagnetic shifts in solid-state NMR of proteins to elicit structural information.  

PubMed

The recent observation of pseudocontact shifts (pcs) in (13)C high-resolution solid-state NMR of paramagnetic proteins opens the way to their application as structural restraints. Here, by investigating a microcrystalline sample of cobalt(II)-substituted matrix metalloproteinase 12 [CoMMP-12 (159 AA, 17.5 kDa)], it is shown that a combined strategy of protein labeling and dilution of the paramagnetic species (i.e., (13)C-,(15)N-labeled CoMMP-12 diluted in unlabeled ZnMMP-12, and (13)C-,(15)N-labeled ZnMMP-12 diluted in unlabeled CoMMP-12) allows one to easily separate the pcs contributions originated from the protein internal metal (intramolecular pcs) from those due to the metals in neighboring proteins in the crystal lattice (intermolecular pcs) and that both can be used for structural purposes. It is demonstrated that intramolecular pcs are significant structural restraints helpful in increasing both precision and accuracy of the structure, which is a need in solid-state structural biology nowadays. Furthermore, intermolecular pcs provide unique information on positions and orientations of neighboring protein molecules in the solid phase. PMID:18988744

Balayssac, Stéphane; Bertini, Ivano; Bhaumik, Anusarka; Lelli, Moreno; Luchinat, Claudio

2008-11-11

146

Partial NMR assignments for uniformly (13C, 15N)-enriched BPTI in the solid state.  

PubMed

We demonstrate that high-resolution multidimensional solid state NMR methods can be used to correlate many backbone and side chain chemical shifts for hydrated micro-crystalline U-13C,15N Basic Pancreatic Trypsin Inhibitor (BPTI), using a field strength of 800 MHz for protons, magic angle sample spinning rates of 20 kHz and proton decoupling field strengths of 140 kHz. Results from two homonuclear transfer methods, radio frequency driven dipolar recoupling and spin diffusion, were compared. Typical 13C peak line widths are 0.5 ppm, resulting in Calpha-Cbeta and Calpha-CO regions that exhibit many resolved peaks. Two-dimensional carbon-carbon correlation spectra of BPTI have sufficient resolution to identify and correlate many of the spin systems associated with the amino acids. As a result, we have been able to assign a large number of the spin systems in this protein. The agreement between shifts measured in the solid state and those in solution is typically very good, although some shifts near the ion binding sites differ by at least 1.5 ppm. These studies were conducted with approximately 0.2 to 0.4 micromol of enriched material; the sensitivity of this method is apparently adequate for other biological systems as well. PMID:10805127

McDermott, A; Polenova, T; Bockmann, A; Zilm, K W; Paulson, E K; Martin, R W; Montelione, G T; Paulsen, E K

2000-03-01

147

Solid State NMR Investigations of Chain Dynamics and Network Order in Model Poly(dimethylsiloxane) Elastomers  

SciTech Connect

This work is at a relatively early stage, however it has been demonstrated that we can reliably probe basic network architectures using the MQ-NMR technique. The initial results are in good agreement with what is known from standard network theory and will serve as a basis for the study of progressively increasing structural complexity in Siloxane network systems.

Lewicki, J P; Mayer, B P; Wilson, T S; Chinn, S C; Maxwell, R S

2010-12-09

148

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

149

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

PubMed

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

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

2014-10-21

150

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. PMID:21456595

2011-01-01

151

NH-NH Vector Correlation in Peptides by Solid-State NMR  

NASA Astrophysics Data System (ADS)

We present a novel solid-state magic angle-spinning NMR method for measuring the NHi-NHi+1 projection angle ?i,i+1 in peptides. The experiment is applicable to uniformly 15N-labeled peptides and is demonstrated on the chemotactic tripeptide N-formyl-l-Met-l-Leu-l-Phe. The projection angle ?i,i+1 is directly related to the peptide backbone torsion angles ?i and ?i. The method utilizes the T-MREV recoupling scheme to restore 15N-1H interactions, and proton-mediated spin diffusion to establish 15N-15N correlations. T-MREV has recently been shown to increase the dynamic range of the 15N-1H recoupling by ?-encoding, and permits an accurate determination of the recoupled NH dipolar interaction. The results are interpreted in a quasi-analytical fashion that permits efficient extraction of the structural parameters.

Reif, B.; Hohwy, M.; Jaroniec, C. P.; Rienstra, C. M.; Griffin, R. G.

2000-07-01

152

De novo determination of peptide structure with solid-state magic-angle spinning NMR spectroscopy  

NASA Astrophysics Data System (ADS)

The three-dimensional structure of the chemotactic peptide N-formyl-L-Met-L-Leu-L-Phe-OH was determined by using solid-state NMR (SSNMR). The set of SSNMR data consisted of 16 13C-15N distances and 18 torsion angle constraints (on 10 angles), recorded from uniformly 13C,15N- and 15N-labeled samples. The peptide's structure was calculated by means of simulated annealing and a newly developed protocol that ensures that all of conformational space, consistent with the structural constraints, is searched completely. The result is a high-quality structure of a molecule that has thus far not been amenable to single-crystal diffraction studies. The extensions of the SSNMR techniques and computational methods to larger systems appear promising.

Rienstra, Chad M.; Tucker-Kellogg, Lisa; Jaroniec, Christopher P.; Hohwy, Morten; Reif, Bernd; McMahon, Michael T.; Tidor, Bruce; Lozano-Pérez, Tomás; Griffin, Robert G.

2002-08-01

153

Characterization of water dynamics in frozen soils by solid-state deuteron NMR.  

PubMed

The presence of unfrozen water in soils at sub-freezing temperatures is important for biogeochemical processes as well as for the genesis of landscapes and survival of life. While several mechanisms can lead to the existence of liquid water at sub-freezing temperatures, this work focuses on the dynamical (entropic) contribution stemming from motions of water molecules at water-soil or water-ice interfaces. We demonstrate the utility of solid-state (2)H NMR methods for characterization of water dynamics in soils on various time scales. Using a sample from McMurdo Dry Valleys, Antarctica, we show the existence of dynamics spanning a milliseconds to picoseconds time scale range. Computational modeling allows for a quantitative description of the dynamics, which involves models such as an exchange between bound and free water, and changes in effective viscosity of water in the soil matrix. PMID:22578873

Vugmeyster, Liliya; Do, Tien; Ostrovsky, Dmitry; Fu, Riqiang; Hagedorn, Birgit

2012-01-01

154

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

155

Restoring symmetry in two-dimensional solid-state NMR correlation spectra  

NASA Astrophysics Data System (ADS)

The intrinsic asymmetry of 2D solid-state homonuclear NMR correlation spectra that arises from a non-uniform preparation of the magnetization can be removed by equilibrating the magnetization in the initial stage of the experiments through dipolar recoupling induced by PARIS or PARISxy schemes. Both methods ensure magnetization exchange with modest radio-frequency amplitudes and permit one to create an initial state that restores the symmetry about the main diagonal of 2D spectra of uniformly labeled biomolecules. This improves the determination of structural and kinetic information. Both recoupling schemes may also be used to record nearly quantitative peak amplitudes in 1D cross-polarization magic-angle-spinning spectra.

Herbert-Pucheta, Jose-Enrique; Pelupessy, Philippe; Bodenhausen, Geoffrey; Tekely, Piotr

2012-06-01

156

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

PubMed

The effect of (1)H decoupling in magic-angle spinning solid-state NMR is studied under radiofrequency irradiation causing simultaneous nutations around a pair of orthogonal axes. Double-nutation with an arbitrary pair of nutation frequencies is implemented through modulation of the amplitude, phase, and frequency of the transmitting pulses. Similarity and difference of double-nutation decoupling and two-pulse phase-modulation decoupling schemes [A. E. Bennett, C. M. Rienstra, M. Auger, K. V. Lakshmi, and R. G. Griffin, J. Chem. Phys. 103, 6951-6958 (1995) and I. Scholz, P. Hodgkinson, B. H. Meier, and M. Ernst, J. Chem. Phys. 130, 114510 (2009)] are discussed. The structure of recoupling bands caused by interference of the (1)H spin nutation with sample spinning is studied by both experiments and numerical simulations. PMID:25494742

Takeda, Kazuyuki; Wakisaka, Asato; Takegoshi, K

2014-12-14

157

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

158

Solid State Nuclear Magnetic Resonance 29 (2006) 132141 A solid-state 13  

E-print Network

molecular probes [3­5]. In this contribution we employ an assortment of natural abundance solid-state NMR a liquid-crystalline solution serves as the basis for the Kevlars brand of commercial fibers [8­10]. PPTA

Frydman, Lucio

2006-01-01

159

Paramagnetic relaxation enhancement solid-state NMR studies of heterogeneous catalytic reaction over HY zeolite using natural abundance reactant.  

PubMed

Paramagnetic relaxation enhancement solid-state NMR (PRE ssNMR) technique was used to investigate catalytic reaction over zeolite HY. After introducing paramagnetic Cu(II) ions into the zeolite, the enhancement of longitudinal relaxation rates of nearby nuclei, i.e.(29)Si of the framework and (13)C of the absorbents, was measured. It was demonstrated that the PRE ssNMR technique facilitated the fast acquisition of NMR signals to monitor the heterogeneous catalytic reaction (such as acetone to hydrocarbon) using natural abundance reactants. PMID:25616847

Zhou, Lei; Li, Shenhui; Su, Yongchao; Li, Bojie; Deng, Feng

2015-01-01

160

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

161

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

PubMed

The weathering of a specimen kaolinite clay was studied over the course of 369 d via solid-state 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and high-field 27Al MAS NMR. The chosen baseline solution conditions (0.05 mol kg-1 of Al, 2 mol kg-1 of Na+, 1 mol kg-1 of NO3-, 1 mol kg-1 of OH-, and pH approximately 13.8) approximate those of solutions leaking from waste tanks at the Hanford Site in Richland, WA. Nonradioactive Cs and Sr cations were added to this synthetic tank waste leachate (STWL) solution at concentrations of 10(-3), 10(-4), and 10(-5) molal (m) to represent their radionuclide counterparts. The transformations of silicon- and aluminum-containing solid phase species were monitored quantitatively by using NMR spectroscopy, with the resulting spectra directly reporting the influence of the initial Cs and Sr on formation and transformation of the neo-formed solids. At the lowest concentration of Cs and Sr employed (10(-5) m in each cation) peaks consistent with the formation of zeolite-like minerals were detected via 29Si and 27Al MAS NMR as early as 33 d. At concentrations of 10(-3) m in each cation, new silicon species are not detected until 93 d, although neophases containing four-coordinate aluminum were detectable at earlier reaction times via 27Al MAS NMR. At the highest magnetic field strengths employed in this NMR study, deconvolutions of resonances detected in the tetrahedral region of the 27Al MAS spectra yielded multiple components, indicating the existence of at least four new aluminum-containing phases. Two of these phases are identified as sodalite and cancrinite through comparison with diffuse-reflectance infrared (DRIFT) spectra and powder X-ray diffraction (XRD) results, while a third phase may correlate with a previously detected aluminum-rich chabazite phase. All measurable solid reaction products have been quantified via their 27Al MAS resonances acquired at high magnetic field strengths (17.6 T), and 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. PMID:16471594

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

2006-01-19

162

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

PubMed

The electrical conductivity of aluminium doped zinc oxide (AZO, ZnO:Al) materials depends on doping induced defects and grain structure. This study aims at relating macroscopic electrical conductivity of AZO nanoparticles with their atomic structure, which is non-trivial because the derived materials are heavily disordered and heterogeneous in nature. For this purpose we synthesized AZO nanoparticles with different doping levels and narrow size distribution by a microwave assisted polyol method followed by drying and a reductive treatment with forming gas. From these particles electrically conductive, optically transparent films were obtained by spin-coating. Characterization involved energy-dispersive X-ray analysis, wet chemical analysis, X-ray diffraction, electron microscopy and dynamic light scattering, which provided a basis for a detailed structural solid-state NMR study. A multinuclear ((27)Al, (13)C, (1)H) spectroscopic investigation required a number of 1D MAS NMR and 2D MAS NMR techniques (T(1)-measurements, (27)Al-MQMAS, (27)Al-(1)H 2D-PRESTO-III heteronuclear correlation spectroscopy), which were corroborated by quantum chemical calculations with an embedded cluster method (EEIM) at the DFT level. From the combined data we conclude that only a small part of the provided Al is incorporated into the ZnO structure by substitution of Zn. The related (27)Al NMR signal undergoes a Knight shift when the material is subjected to a reductive treatment with forming gas. At higher (formal) doping levels Al forms insulating (Al, H and C containing) side-phases, which cover the surface of the ZnO:Al particles and increase the sheet resistivity of spin-coated material. Moreover, calculated (27)Al quadrupole coupling constants serve as a spectroscopic fingerprint by which previously suggested point-defects can be identified and in their great majority be ruled out. PMID:22801707

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

2012-09-01

163

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

164

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

165

Structure and Transformation of Amorphous Calcium Carbonate: A Solid-State 43Ca NMR and Computational Molecular Dynamics Investigation  

SciTech Connect

Amorphous calcium carbonate (ACC) is a metastable precursor to crystalline CaCO{sub 3} phases that precipitates by aggregation of ion pairs and prenucleation clusters. We use {sup 43}Ca solid-state NMR spectroscopy to probe the local structure and transformation of ACC synthesized from seawater-like solutions with and without Mg{sup 2+} and computational molecular dynamics (MD) simulations to provide more detailed molecular-scale understanding of the ACC structure. The {sup 43}Ca NMR spectra of ACC collected immediately after synthesis consist of broad, featureless resonances with Gaussian line shapes (FWHH = 27.6 {+-} 1 ppm) that do not depend on Mg{sup 2+} or H{sub 2}O content. A correlation between {sup 43}Ca isotropic chemical shifts and mean Ca-O bond distances for crystalline hydrous and anhydrous calcium carbonate phases indicates indistinguishable maximum mean Ca-O bond lengths of {approx}2.45 {angstrom} for all our samples. This value is near the upper end of the published Ca-O bond distance range for biogenic and synthetic ACCs obtained by Ca-X-ray absorption spectroscopy. It is slightly smaller than the values from the structural model of Mgfree ACC by Goodwin et al. obtained from reverse Monte Carlo (RMC) modeling of X-ray scattering data and our own computational molecular dynamics (MD) simulation based on this model. An MD simulation starting with the atomic positions of the Goodwin et al. RMC model using the force field of Raiteri and Gale shows significant structural reorganization during the simulation and that the interconnected carbonate/water-rich channels in the Goodwin et al. model shrink in size over the 2 ns simulation time. The distribution of polyhedrally averaged Ca-O bond distances from the MD simulation is in good agreement with the {sup 43}Ca NMR peak shape, suggesting that local structural disorder dominates the experimental line width of ACC.

Singer, Jared W.; Yazaydin, A. O.; Kirkpatrick, Robert J.; Bowers, Geoffrey M.

2012-05-22

166

Interaction between Lipids and Antimicrobial Oligomers Studied by Solid-State NMR  

PubMed Central

Antimicrobial peptides and their synthetic analogues are well known to interact with the cell membrane, which has complex distributions of lipids. The phase behavior of DOPE/DOPG mixed lipids and the interaction between the lipids and several synthetic amphiphilic antimicrobial oligomers (AMOs) were studied by solid-state nuclear magnetic resonance (NMR). A phase diagram of the lipids over a broad window of water content was constructed. There are large areas in the phase diagram where multiple phases coexist, and the fraction of each phase at a given state is dependent on the sample’s preparation and thermal history. The comparable stability of the different phases implies that even slight changes in the lipid condition could result in substantial changes to the phase structure, which may be utilized by living organisms to achieve many membrane functions. Nuclear Overhauser spectroscopy (NOESY) and several other NMR experiments indicated that the AMO primarily resides in the head group region of the lipids and that DOPE, the negative intrinsic curvature lipid, does not selectively enrich in the inverted hexagonal phase. PMID:21612287

Hu, Weiguo; Som, Abhigyan; Tew, Gregory N.

2013-01-01

167

Optimizing oriented planar-supported lipid samples for solid-state protein NMR.  

PubMed

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

Rainey, Jan K; Sykes, Brian D

2005-10-01

168

Synthesis, structure, immobilization and solid-state NMR of new dppp-and tripod-type chelate linkers  

E-print Network

Synthesis, structure, immobilization and solid-state NMR of new dppp- and tripod-type chelate vulnerable to leaching [8,11]. This problem can for example be solved by using chelating linkers that prolong by X-ray structures, and immobilized on silica. The success of the immobilization was proved by 31 P

Bluemel, Janet

169

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

E-print Network

Conformational Changes of an Ion Channel Detected Through Water-Protein Interactions Using Solid conduction by M2 is known to involve water; however direct experimental evidence of M2-water interaction is scarce. Using 1 H spin diffusion solid-state NMR, we have now determined the water accessibility of the M

Hong, Mei

170

Solid-State NMR Spectroscopy of Human Immunodeficiency Virus Fusion Peptides Associated with Host-Cell-Like  

E-print Network

Solid-State NMR Spectroscopy of Human Immunodeficiency Virus Fusion Peptides Associated with Host-Cell-mail: weliky@chemistry.msu.edu Abstract: The human immunodeficiency virus (HIV) is "enveloped" by a membrane, and infection of a host cell begins with fusion between viral and target cell membranes. Fusion is catalyzed

Weliky, David

171

Solid-State NMR Investigations of Peptide-Lipid Interaction and Orientation of a -Sheet Antimicrobial Peptide, Protegrin  

E-print Network

Solid-State NMR Investigations of Peptide-Lipid Interaction and Orientation of a -Sheet Antimicrobial Peptide, Protegrin Satoru Yamaguchi, Teresa Hong,§ Alan Waring,§ Robert I. Lehrer,§ and Mei Hong peptide found in porcine leukocytes. The mechanism of action and the orientation of PG-1 in lipid bilayers

Hong, Mei

172

Use of CP\\/MAS solid-state NMR for the characterization of solvate molecules within estradiol crystal forms  

Microsoft Academic Search

To investigate the solvate molecules within estradiol crystal forms, four crystal forms of estradiol (EM, ET, EP and EC) were obtained by recrystallization from various organic solvents such as methanol, ethanol, isopropanol and acetone, and their physicochemical properties were characterized using XRD, TGA, DSC and solid-state NMR. The XRD patterns showed that the estradiol crystal forms were composed of high

Jeong-Sook Park; Hye Won Kang; Sung Jean Park; Chong-Kook Kim

2005-01-01

173

Methodological developments of solid-state NMR and their applications to structural and dynamic studies of microcrystalline  

E-print Network

the way to investigations of proteins in microcrystalline form and in amyloid fibers. It has become studies of microcrystalline proteins and amyloid peptides Recent progress in solid-state NMR has opened of proteins and amyloid peptides, based on promising methods that are currently under development in our group

174

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

E-print Network

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

Perera, Melanie Ingrid

2012-10-19

175

C Solid-State NMR Study of Polyelectrolyte Multilayers Rashida N. Smith, Linda Reven,* and Christopher J. Barrett*  

E-print Network

13 C Solid-State NMR Study of Polyelectrolyte Multilayers Rashida N. Smith, Linda Reven: Polyelectrolyte multilayers have been prepared by consecutively adsorbing poly(diallyldi- methylammonium chloride poly- electrolyte multilayer (PEM) films has attracted much interest in recent years, since the early

Barrett, Christopher

176

Solid-state NMR studies of the effects of pharmaceutical processing on relaxation dynamics and implications to solidstate drug stability  

E-print Network

Lubach, J.W., Sperger, D.M., Schieber, L.J., and Munson, E.J. The University of Kansas Department of Pharmaceutical Chemistry Solid-State NMR Studies of the Efects of Pharmaceutical Procesing on Relaxation Dynaics and Implications to Solid...

Lubach, J. W.; Sperger, D. M.; Schieber, L. J.; Munson, E. J.

2006-10-25

177

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

SciTech Connect

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

2013-08-29

178

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

SciTech Connect

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 [Ames Laboratory; Park, Yong Bum [Pennsylvania State University; Caporini, Marc A. [Bruker Biospin Corporation; Rosay, Melanie [Bruker Biospin Corporation; Zhong, Linghao [Pennsylvania State University; Cosgrove, Daniel J. [Pennsylvania State University; Hong, Mei [Ames Laboratory

2013-08-29

179

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

180

Solid-state {sup 13}C MAS NMR study of methanol-to-hydrocarbon chemistry over H-SAPO-34  

SciTech Connect

{sup 13}C solid-state MAS NMR was used to probe the chemistry of a number of species involved in the methanol-to-hydrocarbon process over H-SAPO-34 molecular sieve at both high (573 K) and low (473-563 K) temperature ranges and at very low conversion (<0.1%). Isobutane was the only hydrocarbon product observed at 473 and 573 K. Evidence for the operation of a stepwise methylation reaction via surface-bound species derives from, first, the treatment of several samples with different loadings of methanol at 523-563 K and, second, when either [{sup 13}C]methanol is coadsorbed with [{sup 12}C]ethene over the catalyst or [{sup 12}C]ethene is reacted with pre-[{sup 13}C]methylated SAPO-34. The hydrocarbon products in these experiments were mainly isobutane and isopentane as well as methane, ethene, and propane. Based on these experimental findings, a number of mechanistic approaches concerning the very first stages of the reaction are discussed. 56 refs., 13 figs., 3 tabs.

Salehirad, F.; Anderson, M.A. [UMIST, Manchester (United Kingdom)] [UMIST, Manchester (United Kingdom)

1996-12-01

181

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

182

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

183

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. PMID:18922715

Thurber, Kent R.; Tycko, Robert

2009-01-01

184

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

PubMed

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

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

2014-08-19

185

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

186

Fluorine-19 solid state NMR study of vinylidenefluoride polymers using selective relaxation filters.  

PubMed

Two fluoropolymers, poly(vinylidenefluoride) (PVDF) and a vinylidenefluoride telomer (VDFT), with molecular weights of 1 x 10(6) and 2 x 10(3) Da by GPC, respectively, have been analysed by 19F solid-state nuclear magnetic resonance (NMR) spectroscopy. Relaxation-filtered proton-decoupled magic-angle spinning (MAS) experiments, namely T1rho filter, dipolar filter (DF), direct-polarisation delayed acquisition (DPDA) and discrimination induced by variable-amplitude minipulses (DIVAM), allowed signals in the direct polarisation (DP) spectra of PVDF and the VDFT to be discussed in terms of rigid and mobile domains. Both samples showed signals, which were multi-componential, but they differ in the nature of the crystalline form present. Thus, the Vinylidenefluoride (VDF) telomer exhibited a crystalline component corresponding to beta PVDF, whereas the PVDF contained crystallites of the alpha form. Signals relating to end groups and reverse units, plus an anomalous signal displaying long-time transverse relaxation in the DPDA spectrum, were found for both polymers, though they showed diversity in chemical shift and content. Signals related to reverse units and/or end groups were seen between approximately -115 and approximately -117 ppm for both samples. High-speed MAS at higher magnetic field resulted in an increase in resolution so that signals previously attributed to single-phase characteristics are shown to indicate the possibility of several different mobilities. The results are debated with respect to molecular weight and relaxation parameters. PMID:16820283

Wormald, Philip; Ameduri, Bruno; Harris, Robin K; Hazendonk, Paul

2006-09-01

187

A structural model for Alzheimer's -amyloid fibrils based on experimental constraints from solid state NMR  

NASA Astrophysics Data System (ADS)

We present a structural model for amyloid fibrils formed by the 40-residue -amyloid peptide associated with Alzheimer's disease (A1-40), based on a set of experimental constraints from solid state NMR spectroscopy. The model additionally incorporates the cross- structural motif established by x-ray fiber diffraction and satisfies constraints on A1-40 fibril dimensions and mass-per-length determined from electron microscopy. Approximately the first 10 residues of A1-40 are structurally disordered in the fibrils. Residues 12-24 and 30-40 adopt -strand conformations and form parallel -sheets through intermolecular hydrogen bonding. Residues 25-29 contain a bend of the peptide backbone that brings the two -sheets in contact through sidechain-sidechain interactions. A single cross- unit is then a double-layered -sheet structure with a hydrophobic core and one hydrophobic face. The only charged sidechains in the core are those of D23 and K28, which form salt bridges. Fibrils with minimum mass-per-length and diameter consist of two cross- units with their hydrophobic faces juxtaposed.

Petkova, Aneta T.; Ishii, Yoshitaka; Balbach, John J.; Antzutkin, Oleg N.; Leapman, Richard D.; Delaglio, Frank; Tycko, Robert

2002-12-01

188

A solid state 13C-NMR study of kerogen degradation during black shale weathering  

NASA Astrophysics Data System (ADS)

Solid state 13C nuclear magnetic resonance (NMR) spectroscopy is used to examine kerogen composition in weathering profiles of the Monterey, Green River, Woodford, and New Albany formations. Techniques include cross polarization (CP) and Bloch decay (BD) spectral acquisition, dipolar dephasing (DD), spin counting, experiments to provide estimates of relaxation times (T 1?H and T 1H), and proton spin relaxation editing (PSRE). It is demonstrated that CP/MAS (cross polarization/magic angle spinning) spectra obtained on isolated kerogens provide reliable characterization of kerogen composition (compared with BD spectra and whole-rock samples). Highly aliphatic (polymethylenic) kerogens are not appreciably altered during weathering. Aromatic and/or branched aliphatic kerogens accumulate oxidation products and preferentially lose aliphatic relative to aromatic carbon during weathering. No relation is observed between T 1?H times and either kerogen composition or degree of weathering; T 1H times correlate with aromaticity. Two distinct components within kerogens are discerned by PSRE: one highly aliphatic (largely polymethylenic) component and one mixed aliphatic/aromatic component. During weathering, the highly aliphatic component remains largely unaltered, while the mixed component loses aliphatic carbon and accumulates carbonyl oxidation products. Thus it appears that kerogen weathering is dominated by two separate processes: Linear alkyl fragments are cleaved without oxidation, and aromatic/branched alkyl fragments are oxidized while attached to the kerogen macromolecule and then cleaved.

Petsch, S. T.; Smernik, R. J.; Eglinton, T. I.; Oades, J. M.

2001-06-01

189

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

190

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

NASA Astrophysics Data System (ADS)

Efficient acquisition of ultra-wideline solid-state NMR powder patterns is a continuing challenge. In particular, when the breadth of the powder pattern is much larger than the cross-polarization (CP) excitation bandwidth, transfer efficiencies suffer and experimental times are greatly increased. Presented herein is a CP pulse sequence with an excitation bandwidth that is up to ten times greater than that available from a conventional spin-locked CP pulse sequence. The pulse sequence, broadband adiabatic inversion CP (BRAIN-CP), makes use of the broad, uniformly large frequency profiles of chirped inversion pulses, to provide these same characteristics to the polarization transfer process. A detailed theoretical analysis is given, providing insight into the polarization transfer process involved in BRAIN-CP. Experiments on spin-1/2 nuclei including 119Sn, 199Hg and 195Pt nuclei are presented, and the large bandwidth improvements possible with BRAIN-CP are demonstrated. Furthermore, it is shown that BRAIN-CP can be combined with broadband frequency-swept versions of the Carr-Purcell-Meiboom-Gill experiment (for instance with WURST-CPMG, or WCPMG for brevity); the combined BRAIN-CP/WCPMG experiment then provides multiplicative signal enhancements of both CP and multiple-echo acquisition over a broad frequency region.

Harris, Kristopher J.; Lupulescu, Adonis; Lucier, Bryan E. G.; Frydman, Lucio; Schurko, Robert W.

2012-11-01

191

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

PubMed Central

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

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

2013-01-01

192

Solid state field-cycling NMR relaxometry: instrumental improvements and new applications.  

PubMed

The paper reviews recent progress in field cycling (FC) NMR instrumentation and its application to solid state physics. Special emphasis is put on our own work during the last 15years on instrumentation, theory and applications. As far as instrumentation is concerned we report on our development of two types of electronical FC relaxometers, a mechanical FC relaxometer and a combination of FC and one-dimensional microimaging. Progress has been achieved with respect to several parameters such as the accessible field and temperature range as well as the incorporation of sample spinning. Since an appropriate analysis of FC data requires a careful consideration of relaxation theory, we include a theory section discussing the most relevant aspects of relaxation in solids which are related to residual dipolar and quadrupolar interactions. The most important limitations of relaxation theory are also discussed. With improved instrumentation and with the help of relaxation theory we get access to interesting new applications such as ionic motion in solid electrolytes, structure determination in molecular crystals, ultraslow polymer dynamics and rotational resonance phenomena. PMID:25444698

Fujara, Franz; Kruk, Danuta; Privalov, Alexei F

2014-10-01

193

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

PubMed

Solid state NMR is the primary tool for studying the quantitative, site-specific structure, orientation, and dynamics of biomineralization proteins under biologically relevant conditions. Two calcium phosphate proteins, statherin (43 amino acids) and leucine rich amelogenin protein (LRAP; 59 amino acids), have been studied in depth and have different dynamic properties and 2D- and 3D-structural features. These differences make it difficult to extract design principles used in nature for building materials with properties such as high strength, unusual morphologies, or uncommon phases. Consequently, design principles needed for developing synthetic materials controlled by proteins are not clear. Many biomineralization proteins are much larger than statherin and LRAP, necessitating the study of larger biomineralization proteins. More recent studies of the significantly larger full-length amelogenin (180 residues) represent a significant step forward to ultimately investigate the full diversity of biomineralization proteins. Interactions of amino acids, a silaffin derived peptide, and the model LK peptide with silica are also being studied, along with qualitative studies of the organic matrices interacting with calcium carbonate. Dipolar recoupling techniques have formed the core of the quantitative studies, yet the need for isolated spin pairs makes this approach costly and time intensive. The use of multi-dimensional techniques to study biomineralization proteins is becoming more common, methodology which, despite its challenges with these difficult-to-study proteins, will continue to drive future advancements in this area. PMID:25466354

Shaw, Wendy J

2014-10-29

194

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

PubMed

The solid-state (13)C CP MAS NMR technique has the potential of monitoring the chemical composition in the solid state of an intact food sample. This property has been utilized to study mushrooms of different species (Pleurotus ostreatus, Pleurotus eryngii, Pleurotus pulmunarius, and Lentinula edodes), already characterized by chemical analyses for protein and dietary fiber components. Solid-state (13)C CP MAS NMR spectroscopy reveals a large difference in the ratio between the glucidic and the proteic resonances probably depending on the mushroom species. An accurate inspection by model compounds and suitable mixtures of proteins and saccharides gives a methodology to interpret these experimental data. A good correlation (R(2) = 0.93; R(2) = 0.81) has been obtained by comparing the NMR data with the results of the chemical analyses. The results suggest the possibility to perform a taxonomic study and/or a nutritional study on the basis of the ratio between protein and polysaccharide levels determined by NMR or chemical methodologies. PMID:11087506

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

2000-11-01

195

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

NASA Astrophysics Data System (ADS)

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

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

2003-03-01

196

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

PubMed

Two hexanuclear niobium halide cluster compounds with a [Nb6X12](2+) (X=Cl, Br) diamagnetic cluster core, have been studied by a combination of experimental solid-state NMR/NQR techniques and PAW/GIPAW calculations. For niobium sites the NMR parameters were determined by using variable Bo field static broadband NMR measurements and additional NQR measurements. It was found that they possess large positive chemical shifts, contrary to majority of niobium compounds studied so far by solid-state NMR, but in accordance with chemical shifts of (95)Mo nuclei in structurally related compounds containing [Mo6Br8](4+) cluster cores. Experimentally determined ?iso((93)Nb) values are in the range from 2,400 to 3,000 ppm. A detailed analysis of geometrical relations between computed electric field gradient (EFG) and chemical shift (CS) tensors with respect to structural features of cluster units was carried out. These tensors on niobium sites are almost axially symmetric with parallel orientation of the largest EFG and the smallest CS principal axes (Vzz and ?33) coinciding with the molecular four-fold axis of the [Nb6X12](2+) unit. Bridging halogen sites are characterized by large asymmetry of EFG and CS tensors, the largest EFG principal axis (Vzz) is perpendicular to the X-Nb bonds, while intermediate EFG principal axis (Vyy) and the largest CS principal axis (?11) are oriented in the radial direction with respect to the center of the cluster unit. For more symmetrical bromide compound the PAW predictions for EFG parameters are in better correspondence with the NMR/NQR measurements than in the less symmetrical chlorine compound. Theoretically predicted NMR parameters of bridging halogen sites were checked by (79/81)Br NQR and (35)Cl solid-state NMR measurements. PMID:24581866

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

2014-01-01

197

Homonuclear dipolar decoupling with very large scaling factors for high-resolution ultrafast magic angle spinning 1H solid-state NMR spectroscopy  

NASA Astrophysics Data System (ADS)

We present a new phase modulated radio-frequency pulse sequence for homonuclear dipolar decoupling in proton solid-state NMR spectroscopy, eDUMBO-PLUS-1, with a chemical shift scaling factor of 0.73. This sequence was determined by screening random sequences, and experimentally optimizing the best candidates directly on 1H NMR spectra with 60 kHz magic angle spinning. It yields efficient decoupling with linewidths as little as 150 Hz for 1.3 mm MAS probes on different spectrometers. Experiments and calculations support the hypothesis of a radio-frequency and MAS joint averaging regime, in which the large scaling factor contributes significantly to the overall performance of the decoupling sequence.

Salager, Elodie; Dumez, Jean-Nicolas; Stein, Robin S.; Steuernagel, Stefan; Lesage, Anne; Elena-Herrmann, Bénédicte; Emsley, Lyndon

2010-09-01

198

Silicon uptake and metabolism of the marine diatom Thalassiosira pseudonana: Solid-state 29Si NMR and fluorescence microscopic studies  

Microsoft Academic Search

Uptake and metabolism of silicon by diatoms are studied by the combined use of solid-state 29Si NMR spectroscopy and confocal laser fluorescence microscopy especially with respect to the presence and nature of an intracellular silicon-storage pool. Cells of the marine diatom Thalassiosira pseudonana were synchronized by silicon starvation and frozen without any freeze-drying or chemical treatment in order to analyze

C. Gröger; M. Sumper; E. Brunner

2008-01-01

199

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

Microsoft Academic Search

A major issue in the study of biosilicification processes is the harsh chemical conditions required for silica dissolution,\\u000a which often lead to denaturation of the associated bio-organic matter. In order to demonstrate the potential of solid state\\u000a NMR for investigating silicified materials of natural origin, this technique was applied to isotopically enriched Thalassiosira pseudonana diatom cells. 29Si, 1H,31P, 13C and

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

2008-01-01

200

Dynamic mechanical analysis (DMA), 13 c solid state nmr and micro-thermomechanical studies of historical parchment  

Microsoft Academic Search

DMA and solid state 13C NMR techniques were used to measure historical parchment samples within the framework of the project (MAP) Micro Analysis\\u000a of Parchment (EC contract No. SMT4-96-2101) in collaboration with the School of Conservation in Copenhagen. DMA was used in\\u000a both thermal scan and creep modes. Thermal scans provided information on the transitions associated with the collagen polymer.

M. Odlyha; N. S. Cohen; G. M. Foster; A. Aliev; E. Verdonck; D. Grandy

2003-01-01

201

Multiple acquisition of magic angle spinning solid-state NMR experiments using one receiver: Application to microcrystalline and membrane protein preparations.  

PubMed

Solid-state NMR spectroscopy of proteins is a notoriously low-throughput technique. Relatively low-sensitivity and poor resolution of protein samples require long acquisition times for multidimensional NMR experiments. To speed up data acquisition, we developed a family of experiments called Polarization Optimized Experiments (POE), in which we utilized the orphan spin operators that are discarded in classical multidimensional NMR experiments, recovering them to allow simultaneous acquisition of multiple 2D and 3D experiments, all while using conventional probes with spectrometers equipped with one receiver. POE allow the concatenation of multiple 2D or 3D pulse sequences into a single experiment, thus potentially combining all of the aforementioned advances, boosting the capability of ssNMR spectrometers at least two-fold without the addition of any hardware. In this perspective, we describe the first generation of POE, such as dual acquisition MAS (or DUMAS) methods, and then illustrate the evolution of these experiments into MEIOSIS, a method that enables the simultaneous acquisition of multiple 2D and 3D spectra. Using these new pulse schemes for the solid-state NMR investigation of biopolymers makes it possible to obtain sequential resonance assignments, as well as distance restraints, in about half the experimental time. While designed for acquisition of heteronuclei, these new experiments can be easily implemented for proton detection and coupled with other recent advancements, such as dynamic nuclear polarization (DNP), to improve signal to noise. Finally, we illustrate the application of these methods to microcrystalline protein preparations as well as single and multi-span membrane proteins reconstituted in lipid membranes. PMID:25797011

Gopinath, T; Veglia, Gianluigi

2015-04-01

202

Structure of the light-harvesting bacteriochlorophyll c assembly in chlorosomes from Chlorobium limicola determined by solid-state NMR  

PubMed Central

We have determined the atomic structure of the bacteriochlorophyll c (BChl c) assembly in a huge light-harvesting organelle, the chlorosome of green photosynthetic bacteria, by solid-state NMR. Previous electron microscopic and spectroscopic studies indicated that chlorosomes have a cylindrical architecture with a diameter of ?10 nm consisting of layered BChl molecules. Assembly structures in huge noncrystalline chlorosomes have been proposed based mainly on structure-dependent chemical shifts and a few distances acquired by solid-state NMR, but those studies did not provide a definite structure. Our approach is based on 13C dipolar spin-diffusion solid-state NMR of uniformly 13C-labeled chlorosomes under magic-angle spinning. Approximately 90 intermolecular CC distances were obtained by simultaneous assignment of distance correlations and structure optimization preceded by polarization-transfer matrix analysis. It was determined from the ?90 intermolecular distances that BChl c molecules form piggyback-dimer-based parallel layers. This finding rules out the well known monomer-based structures. A molecular model of the cylinder in the chlorosome was built by using this structure. It provided insights into the mechanisms of efficient light harvesting and excitation transfer to the reaction centers. This work constitutes an important advance in the structure determination of huge intact systems that cannot be crystallized. PMID:17215361

Egawa, Ayako; Fujiwara, Toshimichi; Mizoguchi, Tadashi; Kakitani, Yoshinori; Koyama, Yasushi; Akutsu, Hideo

2007-01-01

203

Cs 4P 2Se 10: A new compound discovered with the application of solid-state and high temperature NMR  

NASA Astrophysics Data System (ADS)

The new compound Cs 4P 2Se 10 was serendipitously produced in high purity during a high-temperature synthesis done in a nuclear magnetic resonance (NMR) spectrometer. 31P magic angle spinning (MAS) NMR of the products of the synthesis revealed that the dominant phosphorus-containing product had a chemical shift of -52.8 ppm that could not be assigned to any known compound. Deep reddish brown well-formed plate-like crystals were isolated from the NMR reaction ampoule and the structure was solved with X-ray diffraction. Cs 4P 2Se 10 has the triclinic space group P-1 with a=7.3587(11) Å, b=7.4546(11) Å, c=10.1420(15) Å, ?=85.938(2)°, ?=88.055(2)°, and ?=85.609(2)° and contains the [P 2Se 10] 4- anion. To our knowledge, this is the first compound containing this anion that is composed of two tetrahedral (PSe 4) units connected by a diselenide linkage. It was also possible to form a glass by quenching the melt in ice water, and Cs 4P 2Se 10 was recovered upon annealing. The static 31P NMR spectrum at 350 °C contained a single peak with a -35 ppm chemical shift and a ˜7 ppm peak width. This study highlights the potential of solid-state and high-temperature NMR for aiding discovery of new compounds and for probing the species that exist at high temperature.

Gave, Matthew A.; Canlas, Christian G.; Chung, In; Iyer, Ratnasabapathy G.; Kanatzidis, Mercouri G.; Weliky, David P.

2007-10-01

204

Solid state NMR study of [epsilon-13C]Lys-bacteriorhodopsin: Schiff base photoisomerization.  

PubMed Central

Previous solid state 13C-NMR studies of bacteriorhodopsin (bR) have inferred the C = N configuration of the retinal-lysine Schiff base linkage from the [14-13C]retinal chemical shift (1-3). Here we verify the interpretation of the [14-13C]-retinal data using the [epsilon-13C]lysine 216 resonance. The epsilon-Lys-216 chemical shifts in bR555 (48 ppm) and bR568 (53 ppm) are consistent with a C = N isomerization from syn in bR555 to anti in bR568. The M photointermediate was trapped at pH 10.0 and low temperatures by illumination of samples containing either 0.5 M guanidine-HCl or 0.1 M NaCl. In both preparations, the [epsilon-13C]Lys-216 resonance of M is 6 ppm downfield from that of bR568. This shift is attributed to deprotonation of the Schiff base nitrogen and is consistent with the idea that the M intermediate contains a C = N anti chromophore. M is the only intermediate trapped in the presence of 0.5 M guanidine-HCl, whereas a second species, X, is trapped in the presence of 0.1 M NaCl. The [epsilon-13C]Lys-216 resonance of X is coincident with the signal for bR568, indicating that X is either C = N anti and protonated or C = N syn and deprotonated. PMID:8369438

Farrar, M R; Lakshmi, K V; Smith, S O; Brown, R S; Raap, J; Lugtenburg, J; Griffin, R G; Herzfeld, J

1993-01-01

205

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

PubMed Central

Solid-state NMR spectroscopy has been used successfully for characterizing the structure and dynamics of membrane proteins as well as their interactions with other proteins in lipid bilayers. such an environment is often necessary for achieving native-like structures. sample preparation is the key to this success. Here we present a detailed description of a robust protocol that results in high-quality membrane protein samples for both magic-angle spinning and oriented-sample solid-state NMR. the procedure is demonstrated using two proteins: CrgA (two transmembrane helices) and rv1861 (three transmembrane helices), both from Mycobacterium tuberculosis. the success of this procedure relies on two points. First, for samples for both types of NMR experiment, the reconstitution of the protein from a detergent environment to an environment in which it is incorporated into liposomes results in ‘complete’ removal of detergent. second, for the oriented samples, proper dehydration followed by rehydration of the proteoliposomes is essential. By using this protocol, proteoliposome samples for magic-angle spinning NMR and uniformly aligned samples (orientational mosaicity of <1°) for oriented-sample NMR can be obtained within 10 d. PMID:24157546

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

2014-01-01

206

The contribution of solid-state NMR spectroscopy to understanding biomineralization: Atomic and molecular structure of bone.  

PubMed

Solid-state NMR spectroscopy has had a major impact on our understanding of the structure of mineralized tissues, in particular bone. Bone exemplifies the organic-inorganic composite structure inherent in mineralized tissues. The organic component of the extracellular matrix in bone is primarily composed of ordered fibrils of collagen triple-helical molecules, in which the inorganic component, calcium phosphate particles, composed of stacks of mineral platelets, are arranged around the fibrils. This perspective argues that key factors in our current structural model of bone mineral have come about through NMR spectroscopy and have yielded the primary information on how the mineral particles interface and bind with the underlying organic matrix. The structure of collagen within the organic matrix of bone or any other structural tissue has yet to be determined, but here too, this perspective shows there has been real progress made through application of solid-state NMR spectroscopy in conjunction with other techniques. In particular, NMR spectroscopy has highlighted the fact that even within these structural proteins, there is considerable dynamics, which suggests that one should be cautious when using inherently static structural models, such as those arising from X-ray diffraction analyses, to gain insight into molecular roles. It is clear that the NMR approach is still in its infancy in this area, and that we can expect many more developments in the future, particularly in understanding the molecular mechanisms of bone diseases and ageing. PMID:25797009

Duer, Melinda J

2015-04-01

207

Solid-state 27Al MRI and NMR thermometry for catalytic applications with conventional (liquids) MRI instrumentation and techniques.  

PubMed

Multidimensional images of Al2O3 pellets, cordierite monolith, glass tube, polycrystalline V2O5 and other materials have been detected by 27Al, 51V, and 23Na NMR imaging using techniques and instrumentation conventionally employed for imaging of liquids. These results demonstrate that, contrary to the widely accepted opinion, imaging of "rigid" solids does not necessarily require utilization of solid state NMR imaging approaches, pulse sequences and hardware even for quadrupolar nuclei which exhibit line widths in excess of 100 kHz, such as 51V in polycrystalline V2O5. It is further demonstrated that both 27Al NMR signal intensity and spin-lattice relaxation time decrease with increasing temperature and thus can potentially serve as temperature sensitive parameters for spatially resolved NMR thermometry. PMID:15949745

Koptyug, Igor V; Sagdeev, Dmitry R; Gerkema, Edo; Van As, Henk; Sagdeev, Renad Z

2005-07-01

208

Furanose Dynamics in the HhaI Methyltransferase Target DNA Studied by Solution and Solid State NMR Relaxation  

PubMed Central

Both solid state and solution NMR relaxation measurements are routinely used to quantify the internal dynamics of biomolecules, but in very few cases have these two techniques been applied to the same system and even fewer attempts have been made so far to describe the results obtained through these two methods through a common theoretical framework. We have previously collected both solution 13C and solid state 2H relaxation measurements for multiple nuclei within the furanose rings of several nucleotides of the DNA sequence recognized by HhaI methyltransferase. The data demonstrated that the furanose rings within the GCGC recognition sequence are very flexible, with the furanose rings of the cytidine which is the methylation target experiencing the most extensive motions. In order to interpret these experimental results quantitatively, we have developed a dynamic model of furanose rings based on the analysis of solid state 2H line shapes. The motions are modeled by treating bond reorientations as Brownian excursions within a restoring potential. By applying this model, we are able to reproduce the rates of 2H spin-lattice relaxation in the solid and 13C spin-lattice relaxation in solution using comparable restoring force constants and internal diffusion coefficients. As expected, the 13C relaxation rates in solution are less sensitive to motions that are slower than overall molecular tumbling than to the details of global molecular reorientation, but are somewhat more sensitive to motions in the immediate region of the Larmor frequency. Thus, we conclude that the local internal motions of this DNA oligomer in solution and in the hydrated solid state are virtually the same, and we validate an approach to the conjoint analysis of solution and solid state NMR relaxation and line shapes data, with wide applicability to many biophysical problems. PMID:18844399

Echodu, Dorothy; Goobes, Gil; Shajani, Zahra; Pederson, Kari; Meints, Gary; Varani, Gabriele; Drobny, Gary

2009-01-01

209

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

E-print Network

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

Aluas, Mihaela

210

Comprehensive solid-state NMR analysis reveals the effects of N-methylation on the molecular dynamics of glycine.  

PubMed

Molecular dynamics of metabolites are important for their interactions and functions. To understand the structural dependence of molecular dynamics for N-methylated glycines, we comprehensively measured the (13)C and (1)H spin-lattice relaxation times for sarcosine, N,N-dimethylglycine, betaine, and betaine hydrochloride over a temperature range of 178-460 K. We found that the reorientations of methyl groups were observed for all these molecules, whereas reorientations of whole trimethylamine groups were detected in betaines. While similar rotational properties were observed for methyl groups in N,N-dimethylglycine and those in betaine, three methyl groups in betaine hydrochloride had different motional properties (E(a) ? 20.5 kJ/mol, ?(0) ? 1.85 × 10(-13) s; E(a) ? 13.9 kJ/mol, ?(0) ? 2.1 × 10(-12) s; E(a) ? 15.8 kJ/mol, ?(0) ? 1.1 × 10(-12) s). N,N-Dimethylglycine showed a phase transition at 348.5 K with changed relaxation behavior for methyl groups showing distinct E(a) and ?(0) values. The DIPSHIFT experiments showed that CH(3) and CH(2) moieties in these molecules had dipolar-dephasing curves similar to these moieties in alanine and glycine. The activation energies for CH(3) rotations positively correlated with the number of substituted methyl groups. These findings provided useful information for the structural dependence of molecular dynamics for N-methylated glycines and demonstrated solid-state NMR as a useful tool for probing the structure-dynamics relationships. PMID:22142308

Huang, Jing; Jiang, Limiao; Ren, Pingping; Zhang, Limin; Tang, Huiru

2012-01-12

211

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

E-print Network

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

Mayrhofer, Rebecca Maria

2010-01-01

212

Probing chemical disorder in glasses using silicon-29 NMR spectral editing.  

PubMed

Chemical disorder can be characterized in silicate glasses using spectral editing in (29)Si solid-state NMR. Resonances of the Q(n)(mX) (i.e. Si(OX)(m)(OSi)(n-m)) molecular motifs, which strongly overlap in the (29)Si solid-state NMR spectra of silicate glasses, can be separated and quantified using 2 to n-quantum filters in INADEQUATE-like experiments, without prior knowledge of assigned chemical shifts, offering a new probe for the microscopic origins of residual entropy in glassy materials. PMID:19652827

Hiet, Julien; Deschamps, Michaël; Pellerin, Nadia; Fayon, Franck; Massiot, Dominique

2009-08-28

213

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

USGS Publications Warehouse

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

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

2010-01-01

214

Flow-through lipid nanotube arrays for structure-function studies of membrane proteins by solid-state NMR spectroscopy.  

PubMed

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 175 nm wide and 60-mum-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 fully accessible to aqueous solutes. Thus, high hydration levels as well as pH and desirable ion and/or drug concentrations could be easily maintained and modified as desired in a series of experiments with the same sample. The method allows for membrane protein NMR experiments in a broad pH range that could be extended to as low as 1 and as high as 12 units for a period of up to a few hours and temperatures as high as 70 degrees C without losing the lipid alignment or bilayers from the nanopores. We demonstrate the utility of this method by a solid-state 19.6 T (17)O NMR study of reversible binding effects of mono- and divalent ions on the chemical shift properties of the Leu(10) carbonyl oxygen of transmembrane pore-forming peptide gramicidin A (gA). We further compare the (17)O shifts induced by binding metal ions to the binding of protons in the pH range from 1 to 12 and find a significant difference. This unexpected result points to a difference in mechanisms for ion and proton conduction by the gA pore. We believe that a large number of solid-state NMR-based studies, including structure-function, drug screening, proton exchange, pH, and other titration experiments, will benefit significantly from the method described here. PMID:16861277

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

2006-10-15

215

250 GHz CW Gyrotron Oscillator for Dynamic Nuclear Polarization in Biological Solid State NMR  

PubMed Central

In this paper, we describe a 250 GHz gyrotron oscillator, a critical component of an integrated system for magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments at 9T, corresponding to 380 MHz 1H frequency. The 250 GHz gyrotron is the first gyro-device designed with the goal of seamless integration with an NMR spectrometer for routine DNP-enhanced NMR spectroscopy and has operated under computer control for periods of up to 21 days with a 100% duty cycle. Following a brief historical review of the field, we present studies of the membrane protein bacteriorhodopsin (bR) using DNP-enhanced multidimensional NMR. These results include assignment of active site resonances in [U-13C,15N]-bR and demonstrate the utility of DNP for studies of membrane proteins. Next, we review the theory of gyro-devices from quantum mechanical and classical viewpoints and discuss the unique considerations that apply to gyrotron oscillators designed for DNP experiments. We then characterize the operation of the 250 GHz gyrotron in detail, including its long-term stability and controllability. We have measured the spectral purity of the gyrotron emission using both homodyne and heterodyne techniques. Radiation intensity patterns from the corrugated waveguide that delivers power to the NMR probe were measured using two new techniques to confirm pure mode content: a thermometric approach based on the temperature-dependent color of liquid crystalline media applied to a substrate and imaging with a pyroelectric camera. We next present a detailed study of the mode excitation characteristics of the gyrotron. Exploration of the operating characteristics of several fundamental modes reveals broadband continuous frequency tuning of up to 1.8 GHz as a function of the magnetic field alone, a feature that may be exploited in future tunable gyrotron designs. Oscillation of the 250 GHz gyrotron at the second harmonic of cyclotron resonance begins at extremely low beam currents (as low 12 mA) at frequencies between 320–365 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.

2009-01-01

216

Development and application of high-resolution solid- state NMR dipolar recovery techniques for spin-1/2 nuclei  

NASA Astrophysics Data System (ADS)

The use of magic angle spinning to obtain high resolution solid state spectra has been well documented. This resolution occurs by coherently averaging the chemical shift anisotropy and dipolar interactions to zero over the period of a full rotation. While this allows for higher resolution, the structural information is seemingly lost to the spectrometer eye. Thus, high resolution spectra and structural information appear to be mutually exlusive. Recently, the push in solid state NMR is the development of recoupling techniques which afford both high resolution and structural information. The following dissertation demonstrates the feasibility of implementing such experiments in solving real world problems, and is centered on devising a method to recover homonuclear dipolar interactions in the high resolution regime.

Joers, James M.

217

Separation of 47Ti and 49Ti Solid-State NMR Lineshapes by Static QCPMG Experiments at Multiple Fields  

SciTech Connect

Experimental procedures are proposed and demonstrated that separate the spectroscopic contribution from both 47Ti and 49Ti in solid-state nuclear magnetic resonance spectra. These take advantage of the different nuclear spin quantum numbers of these nuclei that lead to different ‘effective’ radiofrequency fields for the central transition nutation frequencies when these nuclei occur in sites with a significant electric field gradient. Numerical simulations and solid-state NMR experiments were performed on the TiO2 polymorphs anatase and rutile. For anatase the separation of the two isotopes at high field (21.1 T) facilitated accurate determination of both EFG- and CSA-interactions using the different scaling of the EFG-tensor for the two isotopes. Rutile, having a larger quadrupolar coupling constant (CQ) was examined by 49Ti selective experiments at different magnetic fields to obtain spectra with different scalings of the two anisotropic tensors. A small chemical shielding anisotropy (CSA) of -30 ppm was determined.

Larsen, Flemming H.; Farnan, Ian E.; Lipton, Andrew S.

2006-02-01

218

EPR and solid-state NMR studies of poly(dicarbon monofluoride) (C2F)n.  

PubMed

Poly(dicarbon monofluoride) (C2F)n was studied by electron paramagnetic resonance (EPR) and solid-state nuclear magnetic resonance (NMR). The effects of physisorbed oxygen on the EPR and NMR relaxation were underlined and extrapolated to poly(carbon monofluoride) (CF)n and semi-covalent graphite fluoride prepared at room temperature. Physisorbed oxygen molecules are shown to be an important mechanism of both electronic and nuclear relaxations, resulting in apparent spin-lattice relaxation time and line width during NMR and EPR measurements, respectively. The effect of paramagnetic centers on the 19F spin-lattice relaxation was underlined in accordance with the high electron spin density determined by EPR. 19F magic angle spinning (MAS) NMR, 13C MAS NMR, and 13C MAS NMR with 19F to 13C cross polarization (CP) underline the presence of two types of carbon atoms, both sp3 hybridized: some covalently bonded to fluorine and the others linked exclusively to carbon atoms. Finally, a C-F bond length of 0.138 +/- 0.002 nm has been determined thanks to the re-introduction of dipolar coupling using cross polarization. PMID:16800480

Dubois, Marc; Giraudet, Jérôme; Guérin, Katia; Hamwi, André; Fawal, Ziad; Pirotte, Pascal; Masin, Francis

2006-06-22

219

Bottom-up and top-down solid-state NMR approaches for bacterial biofilm matrix composition.  

PubMed

The genomics and proteomics revolutions have been enormously successful in providing crucial "parts lists" for biological systems. Yet, formidable challenges exist in generating complete descriptions of how the parts function and assemble into macromolecular complexes and whole-cell assemblies. Bacterial biofilms are complex multicellular bacterial communities protected by a slime-like extracellular matrix that confers protection to environmental stress and enhances resistance to antibiotics and host defenses. As a non-crystalline, insoluble, heterogeneous assembly, the biofilm extracellular matrix poses a challenge to compositional analysis by conventional methods. In this perspective, bottom-up and top-down solid-state NMR approaches are described for defining chemical composition in complex macrosystems. The "sum-of-the-parts" bottom-up approach was introduced to examine the amyloid-integrated biofilms formed by Escherichia coli and permitted the first determination of the composition of the intact extracellular matrix from a bacterial biofilm. An alternative top-down approach was developed to define composition in Vibrio cholerae biofilms and relied on an extensive panel of NMR measurements to tease out specific carbon pools from a single sample of the intact extracellular matrix. These two approaches are widely applicable to other heterogeneous assemblies. For bacterial biofilms, quantitative parameters of matrix composition are needed to understand how biofilms are assembled, to improve the development of biofilm inhibitors, and to dissect inhibitor modes of action. Solid-state NMR approaches will also be invaluable in obtaining parameters of matrix architecture. PMID:25797008

Cegelski, Lynette

2015-04-01

220

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

PubMed Central

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

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

2011-01-01

221

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

SciTech Connect

Phosphonate binding sites in guanidine and ammonium surface-functionalized silica xerogels were prepared via the molecular imprinting technique and characterized using solid state {sup 31}P MAS NMR. One-point, two-point, and non-specific host-guest interactions between phenylphosphonic acid (PPA) and the functionalized gels were distinguished by characteristic chemical shifts of the observed absorption peaks. Using solid state as well as solution phase NMR analyses, absorptions observed at 15.5 ppm and 6.5 ppm were identified as resulting from the 1:1 (one-point) and 2:1 (two-point) guanidine to phosphonate interactions, respectively. Similar absorptions were observed with the ammonium functionalized gels. By examining the host-guest interactions within the gels, the efficiency of the molecular imprinting procedure with regard to the functional monomer-to-template interaction could be readily assessed. Template removal followed by substrate adsorption studies conducted on the guanidine functionalized gels provided a method to evaluate the binding characteristics of the receptor sites to a phosphonate substrate. During these experiments, {sup 29}Si and {sup 31}P MAS NMR acted as diagnostic monitors to identify structural changes occurring in the gel matrix and at the receptor site from solvent mediated processes.

Sasaki, D.Y.; Alam, T.D.

2000-01-03

222

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

223

Cation ion specifically induces a conformational change in trans-dehydroandrosterone - A solid-state NMR study.  

PubMed

In this work, we demonstrated that calcium (Ca(+2)) is able to induce a conformational change in trans-dehydroandrosterone (DHEA). To this respect, solid-state NMR spectroscopy was applied to a series of DHEA molecules that were incubated with Ca(+2) under different concentrations. The high-resolution (13)C NMR spectra of the DHEA/Ca(+2) mixtures exhibited two distinct sets of signals; one was attributed to DHEA in the free form, and the second set was due to the DHEA/Ca(+2) complex. Based on chemical shift isotropy and anisotropy analyses, we postulated that Ca(+2) might have associated with the oxygen attached to C17 via a lone-pair of electrons, which induced a conformational change in DHEA. Apart from Ca(+2), we also incubated DHEA with magnesium (Mg(+2)) to determine whether Mg(+2) was able to interact with DHEA in a similar manner to Ca(+2). We found that Mg(+2) was able to induce a conformational change in DHEA deviated from that of Ca(+2). These solid-state NMR observations indicate that DHEA is able to interact with cations, such as Mg(+2) and Ca(+2), with specificity. PMID:25637678

Wang, Darong; Chen, Meiman; Chein, Rong-Jie; Ching, Wei-Min; Hung, Chen-Hsiung; Tzou, Der-Lii M

2015-04-01

224

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

225

Alginate monomer composition studied by solution- and solid-state NMR – A comparative chemometric study  

Microsoft Academic Search

The potential of using 1H high-resolution (HR) magic angle spinning (MAS) nuclear magnetic resonance (NMR) of alginates suspended in D2O or 13C cross-polarisation (CP) MAS NMR of alginate powders as an alternative method to the traditional 1H solution-state NMR method for the analysis of the alginate monomer composition (mannuronate (M)\\/guluronate (G) ratio) has been investigated. The MAS NMR experiments can

Tina Salomonsen; Henrik Max Jensen; Flemming Hofmann Larsen; Stefan Steuernagel; Søren Balling Engelsen

2009-01-01

226

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

E-print Network

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

Griffin, Robert G.

227

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. PMID:21134646

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

2010-01-01

228

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

PubMed Central

Solid-state (magic-angle spinning) NMR spectroscopy is a useful tool for obtaining structural information on bone organic and mineral components and synthetic model minerals at the atomic-level. Raman and 31P NMR spectral parameters were investigated in a series of synthetic B-type carbonated apatites (CAps). Inverse 31P NMR linewidth and inverse Raman PO43? ?1 bandwidth were both correlated with powder XRD c-axis crystallinity over the 0.3–10.3 wt% CO32? range investigated. Comparison with bone powder crystallinities showed agreement with values predicted by NMR and Raman calibration curves. Carbonate content was divided into two domains by the 31P NMR chemical shift frequency and the Raman phosphate ?1 band position. These parameters remain stable except for an abrupt transition at 6.5 wt% carbonate, a composition which corresponds to an average of one carbonate per unit cell. This near-binary distribution of spectroscopic properties was also found in AFM-measured particle sizes and Ca/P molar ratios by elemental analysis. We propose that this transition differentiates between two charge-balancing ion-loss mechanisms as measured by Ca/P ratios. These results define a criterion for spectroscopic characterization of B-type carbonate substitution in apatitic minerals. PMID:24273344

McElderry, John-David P.; Zhu, Peizhi; Mroue, Kamal H.; Xu, Jiadi; Pavan, Barbara; Fang, Ming; Zhao, Guisheng; McNerny, Erin; Kohn, David H.; Franceschi, Renny T.; Holl, Mark M. Banaszak; Tecklenburg, Mary M.J.; Ramamoorthy, Ayyalusamy; Morris, Michael D.

2013-01-01

229

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

PubMed Central

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 binding site, whereas the steroid group was more constrained, probably because of hydrogen bonding to residues around the K+-channel region. Crosspolarization magic-angle spinning NMR showed that chemical shifts of inhibitors 13C-labeled in the sugar group moved downfield by 0.5 ppm after binding to the digitalis site, suggesting that the sugar was close to aromatic side groups. A 19F, 13C- rotational-echo double-resonance NMR strategy was used to determine the structure of an inhibitor in the digitalis receptor site, and it showed that the ouabain derivatives adopt a conformation in which the sugar extends out of the plane of the steroid ring system. The combined structural and dynamic information favors a model for inhibition in which the ouabain analogues lie across the surface of the Na+/K+-ATPase ?-subunit with the sugar group facing away from the surface of the membrane but free to move into contact with one or more aromatic residues. PMID:11095733

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

2000-01-01

230

Solid-state 95Mo NMR of mixed-valence polyoxomolybdates (V, VI) with localized or delocalized d1 electrons  

NASA Astrophysics Data System (ADS)

We report solid-state 95Mo NMR of Mo, Mo and Mo species in mixed-valence polyoxomolybdates (V, VI) with localized or delocalized d electrons. Parameters about chemical shift and quadrupole interactions of 95Mo in diamagnetic crystals of [MeNH]6[HMo12VO(OH)12(MoO)4]·2HO(1) with localized electrons and [NMe]2[NH]8[(Mo6VIMoO)2]·8HO(2) with delocalized ones were obtained by simulation of magic-angle-spinning (MAS) 95Mo NMR spectra. The isotropic and anisotropic chemical shifts of sites of Mo in 1 and Mo in 2, respectively, exhibited absolute values quite larger than those of other Mo sites, which is examined by quantum chemical calculations.

Iijima, Takahiro; Yamase, Toshihiro; Tansho, Masataka; Shimizu, Tadashi; Nishimura, Katsuyuki

2010-03-01

231

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

232

Site-Specific Solid-State NMR Studies of "Trigger Factor" in Complex with the Large Ribosomal Subunit?50S.  

PubMed

Co-translational protein folding is not yet well understood despite the availability of high-resolution ribosome crystal structures. We present first solid-state NMR data on non-mobile regions of a prokaryotic ribosomal complex. Localized chemical shift perturbations and line broadening are observed for the backbone amide resonances corresponding to the regions in the trigger factor ribosome-binding domain that are involved in direct contact with the ribosome or undergo conformational changes upon ribosome binding. This large asymmetric protein complex (1.4?MDa) becomes accessible for NMR investigations by the combined use of proton detection and high MAS frequencies (60?kHz). The presented results open new perspectives for the understanding of the mechanism of large molecular machineries. PMID:25655173

Barbet-Massin, Emeline; Huang, Chih-Ting; Daebel, Venita; Hsu, Shang-Te Danny; Reif, Bernd

2015-03-27

233

A solid-state NMR study of hydrogen-bonding networks and ion dynamics in benzimidazole salts.  

PubMed

On the basis of our solid-state NMR characterization of dynamics in two model salts, we draw the analogy to the fuel cell membrane candidate, phosphoric acid-doped poly(benzimidazole), and conclude that phosphate anion dynamics contribute to long-range proton transport, whereas the mobility of the polymer itself is not a contributing factor. This is contrasted with emerging membrane candidates, which rely on fully covalently bonded acid donors and acceptors, and target high-temperature PEM fuel cell operation in the absence of liquid electrolyte. The hydrogen-bonding structures of benzimidazolium phosphate and benzimidazolium methane phosphonate are established using X-ray diffraction paired with solid-state 1H DQF NMR. By comparing the dynamics of the phosphate and methane phosphonate anions with the dynamics of imidazolium and benzimidazolium cations, the relative importance of these processes in proton transport is determined. The imidazolium cation is known to undergo two-site ring reorientation on the millisecond time scale. In contrast, it is shown here that the benzimidazolium rings are immobile in analogous salts, on a time scale extending into the tens of seconds. Therefore, we look to the phosphate anions and demonstrate that the time scale of tetrahedral reorientation is comparably fast (50 ms). Moreover, the 31P CODEX NMR data clearly indicate a four-site jump process. In contrast, the methane phosphonate undergoes a three-site jump on a slower time scale (75 ms). A mechanism for a zigzag pathway of proton transport through the phosphonate salt crystallites is developed based on the 31P CODEX and 1H variable-temperature MAS NMR data. PMID:17472368

Traer, Jason W; Britten, James F; Goward, Gillian R

2007-05-24

234

The effects of anticalcification treatments and hydration on the molecular dynamics of bovine pericardium collagen as revealed by 13C solid-state NMR.  

PubMed

This article describes a solid-state NMR (SSNMR) investigation of the influence of hydration and chemical cross-linking on the molecular dynamics of the constituents of the bovine pericardium (BP) tissues and its relation to the mechanical properties of the tissue. Samples of natural phenethylamine-diepoxide (DE)- and glutaraldehyde (GL)-fixed BP were investigated by (13)C cross-polarization SSNMR to probe the dynamics of the collagen, and the results were correlated to the mechanical properties of the tissues, probed by dynamical mechanical analysis. For samples of natural BP, the NMR results show that the higher the hydration level the more pronounced the molecular dynamics of the collagen backbone and sidechains, decreasing the tissue's elastic modulus. In contrast, in DE- and GL-treated samples, the collagen molecules are more rigid, and the hydration seems to be less effective in increasing the collagen molecular dynamics and reducing the mechanical strength of the samples. This is mostly attributed to the presence of cross-links between the collagen plates, which renders the collagen mobility less dependent on the water absorption in chemically treated samples. PMID:20641133

deAzevedo, E R; Ayrosa, A M I B; Faria, G C; Cervantes, H J; Huster, D; Bonagamba, T J; Pitombo, R N M; Rabbani, S R

2010-09-01

235

?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

236

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

237

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

SciTech Connect

Solid-state (magic-angle spinning) NMR spectroscopy is a useful tool for obtaining structural information on bone organic and mineral components and synthetic model minerals at the atomic-level. Raman and {sup 31}P NMR spectral parameters were investigated in a series of synthetic B-type carbonated apatites (CAps). Inverse {sup 31}P NMR linewidth and inverse Raman PO{sub 4}{sup 3?}?{sub 1} bandwidth were both correlated with powder XRD c-axis crystallinity over the 0.3–10.3 wt% CO{sub 3}{sup 2?} range investigated. Comparison with bone powder crystallinities showed agreement with values predicted by NMR and Raman calibration curves. Carbonate content was divided into two domains by the {sup 31}P NMR chemical shift frequency and the Raman phosphate ?{sub 1} band position. These parameters remain stable except for an abrupt transition at 6.5 wt% carbonate, a composition which corresponds to an average of one carbonate per unit cell. This near-binary distribution of spectroscopic properties was also found in AFM-measured particle sizes and Ca/P molar ratios by elemental analysis. We propose that this transition differentiates between two charge-balancing ion-loss mechanisms as measured by Ca/P ratios. These results define a criterion for spectroscopic characterization of B-type carbonate substitution in apatitic minerals. - Graphical abstract: Carbonated apatite shows an abrupt change in spectral (NMR, Raman) and morphological (AFM) properties at a composition of about one carbonate substitution per unit cell. Display Omitted - Highlights: • Crystallinity (XRD), particle size (AFM) of carbonated apatites and bone mineral. • Linear relationships among crystallinity, {sup 31}P NMR and Raman inverse bandwidths. • Low and high carbonated apatites use different charge-balancing ion-loss mechanism.

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

2013-10-15

238

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

PubMed Central

Background Organic light emitting devices (OLED) are becoming important and characterisation of them, in terms of structure, charge distribution, and intermolecular interactions, is important. Tris(8-hydroxyquinolinato)-aluminium(III), known as Alq3, an organomettalic complex has become a reference material of great importance in OLED. It is important to elucidate the structural details of Alq3 in its various isomeric and solvated forms. Solid-state nuclear magnetic resonance (NMR) is a useful tool for this which can also complement the information obtained with X-ray diffraction studies. Results We report here 27Al one-dimensional (1D) and two-dimensional (2D) multiple-quantum magic-angle spinning (MQMAS) NMR studies of the meridional (?-phase) and the facial (?-phase) isomeric forms of Alq3. Quadrupolar parameters are estimated from the 1D spectra under MAS and anisotropic slices of the 2D spectra and also calculated using DFT (density functional theory) quantum-chemical calculations. We have also studied solvated phase of Alq3 containing ethanol in its lattice. We show that both the XRD patterns and the quadrupolar parameters of the solvated phase are different from both the ?-phase and the ?-phase, although the fluorescence emission shows no substantial difference between the ?-phase and the solvated phase. Moreover, we have shown that after the removal of ethanol from the matrix the solvated Alq3 has similar XRD patterns and quadrupolar parameters to that of the ?-phase. Conclusion The 2D MQMAS experiments have shown that all the different modifications of Alq3 have 27Al in single unique crystallographic site. The quadrupolar parameters predicted using the DFT calculation under the isodensity polarisable continuum model resemble closely the experimentally obtained values. The solvated phase of Alq3 containing ethanol has structural difference from the ?-phase of Alq3 (containing meridional isomer) from the solid-state NMR studies. Solid-state NMR can hence be used as an effective complementary tool to XRD for characterisation and structural elucidation. PMID:19900275

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

2009-01-01

239

Detection of low-level PTFE contamination: An application of solid-state NMR to structure elucidation in the pharmaceutical industry.  

PubMed

We report a novel use of solid-state ¹?F nuclear magnetic resonance to detect and quantify polytetrafluoroethylene contamination from laboratory equipment, which due to low quantity (up to 1% w/w) and insolubility remained undetected by standard analytical techniques. Solid-state ¹?F NMR is shown to be highly sensitive to such fluoropolymers (detection limit 0.02% w/w), and is demonstrated as a useful analytical tool for structure elucidation of unknown solid materials. PMID:20880648

Pham, Tran N; Day, Caroline J; Edwards, Andrew J; Wood, Helen R; Lynch, Ian R; Watson, Simon A; Bretonnet, Anne-Sophie Z; Vogt, Frederick G

2011-01-25

240

Determination of Anion Ordering in Mixed Apatites via Multinuclear Solid-State NMR & X-ray Crystallography  

NASA Astrophysics Data System (ADS)

Subtle changes in crystallographic anion position in apatite sensu latu Ca5(PO4)3(F,OH,Cl) are known to affect greatly its macroscopic physical properties, such as acid resistivity and hardness. While the anion positions in endmember compositions are well described, there exist substantial gaps in our understanding of anion ordering in mixed binary and ternary compositions because of potential steric anion interactions and symmetry changes. X-ray diffraction analysis of these binary/ternary mixtures is well-suited to address the atomic positions and average occupancies of these anion sites for well-ordered systems. Multinuclear solid-state NMR methods complement XRD structure studies if there exist column ordering reversals or disorder in the atomic positions of the anions, as NMR is sensitive to the atomic arrangement within short distances of the nucleus (<4Å). Using these analytical techniques the anion ordering along the F-Cl solid-solution join is reported, and features an off-mirror fluorine site at (0,0,0.167). The migration of fluorine away from its end-member site within the {00l} mirror plane and subsequent migration of chlorine in the opposing direction results in acceptable F-Cl distances in the anion column. Exceptionally low H content in the anion channel was afforded via high-temperature (1200°C) solid-state reaction under vacuum. The speciation of H was determined by 1H{31P} REDOR experiments, from which the REDOR difference spectrum features a single resonance at ?H = 1.6 ppm which can be assigned to OH groups. The abundance of OH was confirmed by comparison of single-pulse (SP) 31P and cross-polarization 31P{1H} NMR (CP) spectral intensities to those of a crystalline synthetic hydroxylapatite, and showed that only 0.4 mol% of the 31P in the composition occurs in hydroxylapatite-like configurations.

Vaughn, J. S.; Phillips, B. L.; Hughes, J. M.; Nekvasil, H.; Ustunisik, G. K.; Lindsley, D. H.; Coraor, A. E.; McCubbin, F. M.; Woerner, W. R.

2013-12-01

241

Solid-state 2H NMR relaxation illuminates functional dynamics of retinal cofactor in membrane activation of rhodopsin  

PubMed Central

Rhodopsin is a canonical member of the family of G protein-coupled receptors, which transmit signals across cellular membranes and are linked to many drug interventions in humans. Here we show that solid-state 2H NMR relaxation allows investigation of light-induced changes in local ps–ns time scale motions of retinal bound to rhodopsin. Site-specific 2H labels were introduced into methyl groups of the retinal ligand that are essential to the activation process. We conducted solid-state 2H NMR relaxation (spin-lattice, T1Z, and quadrupolar-order, T1Q) experiments in the dark, Meta I, and Meta II states of the photoreceptor. Surprisingly, we find the retinylidene methyl groups exhibit site-specific differences in dynamics that change upon light excitation—even more striking, the C9-methyl group is a dynamical hotspot that corresponds to a crucial functional hotspot of rhodopsin. Following 11-cis to trans isomerization, the 2H NMR data suggest the ?-ionone ring remains in its hydrophobic binding pocket in all three states of the protein. We propose a multiscale activation mechanism with a complex energy landscape, whereby the photonic energy is directed against the E2 loop by the C13-methyl group, and toward helices H3 and H5 by the C5-methyl of the ?-ionone ring. Changes in retinal structure and dynamics initiate activating fluctuations of transmembrane helices H5 and H6 in the Meta I–Meta II equilibrium of rhodopsin. Our proposals challenge the Standard Model whereby a single light-activated receptor conformation yields the visual response—rather an ensemble of substates is present, due to the entropy gain produced by photolysis of the inhibitory retinal lock. PMID:21527723

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

2011-01-01

242

A comparative spectroscopic investigation of three pseudopolymorphs of testosterone using solid-state i.r. and high-resolution solid-state NMR  

NASA Astrophysics Data System (ADS)

Three pseudopolymorphic forms of testosterone have been examined by i.r. and CP/MAS NMR spectroscopies. The transmittance i.r. data clearly distinguish the forms. The NMR work also provides clear distinctions and shows crystallographic splittings for the ? form only, in accordance with the X-ray data. The NMR spectra are fully assigned. The effect of crystallisation procedure on the NMR spectra was explored. NMR can be used to quantitatively assess mixtures of the ? and ? forms.

Fletton, Richard A.; Harris, Robin K.; Kenwright, Alan M.; Lancaster, Robert W.; Packer, Kenneth J.; Sheppard, Norman

243

The solid state 13C-NMR and 19F-NMR spectra of some graphite fluorides  

Microsoft Academic Search

The solid state 13C nuclear magnetic resonance spectra of fluorinated graphites show two resonances, one of which is assigned to aromatic carbon and the other to aliphatic carbon. The resonances are very broad with the high-field resonance centered at about 35 ppm below tetramethylsilane (TMS) and a low-field resonance centered at about 160 ppm below tetramethylsilane. The high-field resonance is

Charles A. Wilkie; Gong-Yu Lin; Daniel T. Haworth

1979-01-01

244

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

E-print Network

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

Barnes, Alexander B. (Alexander Benjamin)

2011-01-01

245

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

E-print Network

or formulated active pharmaceutical ingredient (API). To overcome the major shortcomings of SSNMR, acquisition time and sensitivity, a two-sample probe was designed, developed, and tested. The probe allowed for two samples to be acquired simultaneously while...

Schieber, Loren

2010-01-22

246

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

247

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

248

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

PubMed

Humic acids (HAs) of four representative forest soils profiles from Central Spain (two with different vegetation - pine and oak - but same parent material - granitie, and two with same vegetation - holm oak - but different parent material - granite and limestone) were investigated by solid-state cross polarization with magic angle spinning (13)C nuclear magnetic resonance (NMR) spectroscopy. The objectives included the investigation of the impact of different forest properties on HA composition, assessing how the structural characteristics of the HA vary with soil depth, and evaluating the role of HA as surrogates for mapping the different forest soils signatures using structural data derived from (13)C NMR spectroscopy. On average, alkyl C is the dominant C constituent (38-48% of the total NMR peak area) in all HA samples, followed by aromatic (12-22%) and O-alkyl C (12-19%), and finally carboxyl C (7.0-10%). The NMR data also indicated that HA composition is likely to be differently affected by the soil physico-chemical properties and type of forest vegetation. The structural characteristics of the HA from soil under oak did not differ broadly downward in the profile, whereas soil HA under pine forest exhibits a somewhat higher recalcitrant nature as a consequence of a higher degree of decomposition. The soil HA from holm oak forests differed from the other two forest soils, exhibiting a progressive decomposition of the alkyl C structures with increasing depth, while the carbohydrate-like indicator (O-alkyl C) is apparently being protected from mineralization in the horizons below the ground level. Overall, these differences in soil HA NMR signatures are an important diagnostic tool for understanding the role of different soil environmental factors on the structural composition of HA from Mediterranean forest soils. PMID:23332874

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

2013-06-01

249

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

PubMed

Disordered sol-gel prepared calcium silicate biomaterials show significant, composition dependent ability to bond with bone. Bone bonding is attributed to rapid hydroxycarbonate apatite (HCA) formation on the glass surface after immersion in body fluid (or implantation). Atomic scale details of the development of the structure of (CaO)x(SiO2)1-x (x = 0.2, 0.3 and 0.5) under heat treatment and subsequent dissolution in simulated body fluid (SBF) are revealed through a multinuclear solid state NMR approach using one-dimensional (17)O, (29)Si, (31)P and (1)H. Central to this study is the combination of conventional static and magic angle spinning (MAS) and two-dimensional (2D) triple quantum (3Q) (17)O NMR experiments that can readily distinguish and quantify the bridging (BOs) and non-bridging (NBOs) oxygens in the silicate network. Although soluble calcium is present in the sol, the (17)O NMR results reveal that the sol-gel produced network structure is initially dominated by BOs after gelation, aging and drying (e.g. at 120 °C), indicating a nanoscale mixture of the calcium salt and a predominantly silicate network. Only once the calcium salt is decomposed at elevated temperatures do the Ca(2+) ions become available to break BO. Apatite forming ability in SBF depends strongly on the surface OH and calcium content. The presence of calcium aids HCA formation via promotion of surface hydration and the ready availability of Ca(2+) ions. (17)O NMR shows the rapid loss of NBOs charge balanced by calcium as it is leached into the SBF. The formation of nanocrystalline, partially ordered HCA can be detected via(31)P NMR. This data indicates the importance of achieving the right balance of BO/NBO for optimal biochemical response and network properties. PMID:25494341

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

2015-01-28

250

High-field 19.6 T 27Al solid-state MAS NMR of in vitro aluminated brain tissue  

NASA Astrophysics Data System (ADS)

The combination of 27Al high-field solid-state NMR (19.6 T) with rapid spinning speeds (17.8 kHz) is used to acquire 27Al NMR spectra of total RNA human brain temporal lobe tissues exposed to 0.10 mM Al 3+ (as AlCl 3) and of human retinal pigment epithelial cells (ARPE-19), grown in 0.10 mM AlCl 3. The spectra of these model systems show multiple Al 3+ binding sites, good signal/noise ratios and apparent chemical shift dispersions. A single broad peak (-3 to 11 ppm) is seen for the aluminated ARPE-19 cells, consistent with reported solution-state NMR chemical shifts of Al-transferrin. The aluminated brain tissue has a considerably different 27Al MAS NMR spectrum. In addition to the transferrin-type resonance, additional peaks are seen. Tentative assignments include: -9 to -3 ppm, octahedral AlO 6 (phosphate and water); 9 ppm, condensed AlO 6 units (Al-O-Al bridges); 24 ppm, tetrahedral AlO 3N and/or octahedral Al-carbonate; and 35 ppm, more N-substituted aluminum and /or tetrahedral AlO 4. Thus, brain tissue is susceptible to a broad range of coordination by aluminum. Furthermore, the moderate 27Al C Q values (all less than 10 MHz) suggest future NMR studies may be performed at 9.4 T and a spin rate of 20 kHz.

Bryant, Pamela L.; Lukiw, Walter J.; Gan, Zhehong; Hall, Randall W.; Butler, Leslie G.

2004-10-01

251

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

252

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

PubMed

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

Nieto, Carla I; Cabildo, Pilar; García, M Ángeles; Claramunt, Rosa M; Alkorta, Ibon; Elguero, José

2014-01-01

253

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

PubMed Central

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

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

2014-01-01

254

Electron localization of polyoxomolybdates with ?-Keggin structure studied by solid-state 95Mo NMR and DFT calculation.  

PubMed

We report electron localization of polyoxomolybdates with ?-Keggin structure investigated by solid-state (95)Mo NMR and DFT calculation. The polyoxomolybdates studied are the basic ?-Keggin crystals of [Me3NH]6[H2Mo12O28(OH)12{MoO3}4] · 2H2O (1), the crystals suggested to have a disordered {?-Mo12} core of [PMo12O36(OH)4{La(H2O)2.75Cl1.25}4]·27H2O (2), and the paramagnetic Keggin crystals of [H2Mo12O30(OH)10{Ni(H2O)3}4] · 14H2O (3). The spectra of (95)Mo static NMR of these samples were measured under moderate (9.4 and 11.7 T) and ultrahigh magnetic fields (21.8 T). From spectral simulation and quantum chemical calculation, the NMR parameters of the chemical shift and quadrupole interactions for (95)Mo were estimated. By the analysis based on the result for 1, it was found for 2 that although the {?-Mo12} core is disordered, the eight d(1) electrons in it are not completely localized on four Mo-Mo bonds. Furthermore, it was shown for 3 that the d(1) electrons are localized to make the Mo-Mo bonds, while the unpaired electrons are also almost localized on the paramagnetic Ni(II) ions. PMID:24650319

Iijima, Takahiro; Yamase, Toshihiro; Tansho, Masataka; Shimizu, Tadashi; Nishimura, Katsuyuki

2014-04-01

255

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

SciTech Connect

Highlights: • Model estimated the molecular C components well for most RO wastes. • Molecular nature of organic matter in RO wastes varied widely. • Molecular composition by NMR modelling preferable to extraction techniques. • Some model shortcomings in estimating molecular composition of biochars. • Waste molecular composition important for carbon/nutrient outcomes in soil. - Abstract: Using solid state {sup 13}C NMR data and elemental composition in a molecular mixing model, we estimated the molecular components of the organic matter in 16 recycled organic (RO) wastes representative of the major materials generated in the Sydney basin area. Close correspondence was found between the measured NMR signal intensities and those predicted by the model for all RO wastes except for poultry manure char. Molecular nature of the organic matter differed widely between the RO wastes. As a proportion of organic C, carbohydrate C ranged from 0.07 to 0.63, protein C from <0.01 to 0.66, lignin C from <0.01 to 0.31, aliphatic C from 0.09 to 0.73, carbonyl C from 0.02 to 0.23, and char C from 0 to 0.45. This method is considered preferable to techniques involving imprecise extraction methods for RO wastes. Molecular composition data has great potential as a predictor of RO waste soil carbon and nutrient outcomes.

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

2013-11-15

256

Visualising substrate-fingermark interactions: Solid-state NMR spectroscopy of amino acid reagent development on cellulose substrates.  

PubMed

Most spectroscopic studies of the reaction products formed by ninhydrin, 1,2-indanedione-zinc (Ind-Zn) and 1,8-diazafluoren-9-one (DFO) when reacted with amino acids or latent fingermarks on paper substrates are focused on visible absorption or luminescence spectroscopy. In addition, structural elucidation studies are typically limited to solution-based mass spectrometry or liquid nuclear magnetic resonance (NMR) spectroscopy, which does not provide an accurate representation of the fingermark development process on common paper substrates. The research presented in this article demonstrates that solid-state carbon-13 magic angle spinning NMR ((13)C-MAS-NMR) is a technique that can not only be utilised for structural studies of fingermark enhancement reagents, but is a promising technique for characterising the effect of paper chemistry on fingermark deposition and enhancement. The latter opens up a research area that has been under-explored to date but has the potential to improve our understanding of how fingermark secretions and enhancement reagents interact with paper substrates. PMID:25766739

Spindler, Xanthe; Shimmon, Ronald; Roux, Claude; Lennard, Chris

2015-05-01

257

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

258

On the problem of resonance assignments in solid state NMR of uniformly (15)N,(13)C-labeled proteins.  

PubMed

Determination of accurate resonance assignments from multidimensional chemical shift correlation spectra is one of the major problems in biomolecular solid state NMR, particularly for relative large proteins with less-than-ideal NMR linewidths. This article investigates the difficulty of resonance assignment, using a computational Monte Carlo/simulated annealing (MCSA) algorithm to search for assignments from artificial three-dimensional spectra that are constructed from the reported isotropic (15)N and (13)C chemical shifts of two proteins whose structures have been determined by solution NMR methods. The results demonstrate how assignment simulations can provide new insights into factors that affect the assignment process, which can then help guide the design of experimental strategies. Specifically, simulations are performed for the catalytic domain of SrtC (147 residues, primarily ?-sheet secondary structure) and the N-terminal domain of MLKL (166 residues, primarily ?-helical secondary structure). Assuming unambiguous residue-type assignments and four ideal three-dimensional data sets (NCACX, NCOCX, CONCA, and CANCA), uncertainties in chemical shifts must be less than 0.4ppm for assignments for SrtC to be unique, and less than 0.2ppm for MLKL. Eliminating CANCA data has no significant effect, but additionally eliminating CONCA data leads to more stringent requirements for chemical shift precision. Introducing moderate ambiguities in residue-type assignments does not have a significant effect. PMID:25797013

Tycko, Robert

2015-04-01

259

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

PubMed

Solid-state NMR (SSNMR) (1)H T1 and T1? relaxation times were used to evaluate the miscibility of amorphous solid dispersions of nifedipine (NIF) and polyvinylpyrrolidone (PVP) prepared by three different methods: melt quenching in the typical lab setting, spray drying and melt quenching in the NMR rotor while spinning. Of the five compositions prepared by melt quenching in the lab setting, the 95:5 and 90:10 NIF:PVP (w:w) amorphous solid dispersions were not miscible while 75:25, 60:40, and 50:50 NIF:PVP dispersions were miscible by the (1)H T1? measurements. The domain size of the miscible systems was estimated to be less than 4.5 nm. Amorphous solid dispersions with composition of 90:10 NIF:PVP prepared by spray drying and melt quenching in the NMR rotor showed miscibility by (1)H T1? values. Variable-temperature SSNMR (1)H T1? relaxation measurements revealed a change in relaxation time at approximately 20 °C below Tg, suggesting increased molecular mobility above that temperature. PMID:24256090

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

2014-01-01

260

Solid-state NMR studies of hydrogen bonding networks and proton transport pathways based on anion and cation dynamics.  

PubMed

Proton dynamics in polymer electrolyte membranes are multifaceted processes, and the relative contributions of various mechanisms can be difficult to distinguish. Judicious choices of model systems can aid in understanding the critical steps. In this study, we characterize anion dynamics in a series of benzimidazole-alkyl phosphonate salts, and compare those dynamics to a membrane prototype, built on a decane backbone. The series of salts are characterized, using high resolution (1)H solid-state magic angle spinning (MAS) NMR, DQ MAS NMR, and (31)P centreband-only detection of exchange (CODEX) NMR spectroscopy, to determine the influence of the nature of the alkyl group on the rates and geometries of anion dynamics, and overall proton exchange processes. The alkyl group is shown to slow the correlation times for anion reorientation, when compared at ambient temperature. However, it is also apparent that the lowered lattice energy of the salt lowers the activation energy and allows good dynamics at intermediate temperatures in both the benzimidazolium ethylphosphonate and in the HBr adduct of 1,10-(1-H-imidazol-5-yl)decanephosphonic acid (Imi-d-Pa). PMID:18157806

Traer, Jason W; Goward, Gillian R

2007-12-01

261

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

262

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

NASA Astrophysics Data System (ADS)

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

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

1994-07-01

263

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

PubMed

Biofuels and biomaterials, produced from lignocellulosic feedstock, require facile access to cellulose and hemicellulose to be competitive with petroleum processing and sugar-based fermentation. Physical-chemical barriers resulting from lignin complicates the hydrolysis biomass into fermentable sugars. Thus, the amount of lignin within a substrate is critical in determining biomass processing. The application of (13)C cross-polarization, magic-angle spinning, and solid-state nuclear magnetic resonance for the direct quantification of lignin content in biomass is examined. Using a standard curve constructed from pristine lignin and cellulose, the lignin content of a biomass sample is accurately determined through direct measurement without chemical or enzymatic pre-treatment. PMID:25404762

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

2015-02-01

264

Solid-state NMR spectroscopy of membrane-associated myelin basic protein--conformation and dynamics of an immunodominant epitope.  

PubMed

Myelin basic protein (MBP) maintains the tight multilamellar compaction of the myelin sheath in the central nervous system through peripheral binding of adjacent lipid bilayers of oligodendrocytes. Myelin instability in multiple sclerosis (MS) is associated with the loss of positive charge in MBP as a result of posttranslational enzymatic deimination. A highly-conserved central membrane-binding fragment (murine N81-PVVHFFKNIVTPRTPPP-S99, identical to human N83-S101) represents a primary immunodominant epitope in MS. Previous low-resolution electron paramagnetic resonance measurements on the V83-T92 fragment, with Cys-mutations and spin-labeling that scanned the epitope, were consistent with it being a membrane-associated amphipathic alpha-helix. Pseudodeimination at several sites throughout the protein, all distal to the central segment, disrupted the alpha-helix at its amino-terminus and exposed it to proteases, representing a potential mechanism in the autoimmune pathogenesis of MS. Here, we have used magic-angle spinning solid-state NMR spectroscopy to characterize more precisely the molecular conformation and dynamics of this central immunodominant epitope of MBP in a lipid milieu, without Cys-substitution. Our solid-state NMR measurements have revealed that the alpha-helix present within the immunodominant epitope is shorter than originally modeled, and is independent of the pseudodeimination, highlighting the importance of the local hydrophobic effects in helix formation and stability. The main effect of pseudodeimination is to cause the cytoplasmic exposure of the fragment, potentially making it more accessible to proteolysis. These results are the first, to our knowledge, to provide atomic-level detail of a membrane-anchoring segment of MBP, and direct evidence of decreased MBP-membrane interaction after posttranslational modification. PMID:20713009

Ahmed, Mumdooh A M; Bamm, Vladimir V; Harauz, George; Ladizhansky, Vladimir

2010-08-01

265

Solid-State Deuterium NMR Spectroscopy of Membranes Michael F. Brown1  

E-print Network

are classified as smectic A lyotropic liquid crystals, and an illustration of the liquid-crystalline lamellar, e.g. polymers, glasses, protein precipitates, and mem- brane proteins. Rather than being mainly 2 H NMR studies of membrane proteins [11­15] and DNA fibers [16] have also been conducted

Brown, Michael F.

266

Solid-state NMR analysis of soil organic matter fractions from integrated physical-chemical extraction  

Technology Transfer Automated Retrieval System (TEKTRAN)

Fractions of soil organic matter (SOM) are usually extracted from soil by either physical (size, density) or chemical (e.g., base, acid) procedures. In this study we used 13C nuclear magnetic resonance (NMR) spectroscopy to chemically characterize the fractions that were obtained by an integrated pr...

267

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

Microsoft Academic Search

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.

Michal Wolniak; Michal Tomczyk; Jan Gudej; Iwona Wawer

2006-01-01

268

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

269

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

SciTech Connect

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

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

2014-08-28

270

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

Microsoft Academic Search

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

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

2000-01-01

271

ACCELERATED LIGHT-INDUCED AGING OF ?-, ?-, AND ?-C-ENRICHED CELL WALL-DEHYDROGENATION POLYMERS STUDIED WITH SOLID STATENMR SPECTROSCOPY  

Microsoft Academic Search

Light-induced aging of lignocellulosic materials has been studied with a new technique involving selectively ?-, ?-, and ?-C-enriched cell wall-dehydrogenation polymers (CW-DHPs) and solid stateNMR spectroscopy. The results from cross-polarization magic angle spinning (CP\\/MAS) C NMR experiments of unirradiated and irradiated CW-DHP have revealed mainly a decrease in the amount of end-groups of both coniferaldehyde and coniferyl alcohol type. The

Jim Parkås; Magnus Paulsson; D. L. VanderHart; Ulla Westermark

2002-01-01

272

Hyperpolarized NMR Probes for Biological Assays  

PubMed Central

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

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

2014-01-01

273

Variability of cork from Portuguese Quercus suber studied by solid-state (13)C-NMR and FTIR spectroscopies.  

PubMed

A new approach is presented for the study of the variability of Portuguese reproduction cork using solid-state (13)C-NMR spectroscopy and photoacoustic (PAS) FTIR (FTIR-PAS) spectroscopy combined with chemometrics. Cork samples were collected from 12 different geographical sites, and their (13)C-cross-polarization with magic angle spinning (CP/MAS) and FTIR spectra were registered. A large spectral variability among the cork samples was detected by principal component analysis and found to relate to the suberin and carbohydrate contents. This variability was independent of the sample geographical origin but significantly dependent on the cork quality, thus enabling the distinction of cork samples according to the latter property. The suberin content of the cork samples was predicted using multivariate regression models based on the (13)C-NMR and FTIR spectra of the samples as reported previously. Finally, the relationship between the variability of the (13)C-CP/MAS spectra with that of the FTIR-PAS spectra was studied by outer product analysis. This type of multivariate analysis enabled a clear correlation to be established between the peaks assigned to suberin and carbohydrate in the FTIR spectrum and those appearing in the (13)C-CP/MAS spectra. PMID:11745122

Lopes, M H; Barros, A S; Pascoal Neto, C; Rutledge, D; Delgadillo, I; Gil, A M

2001-01-01

274

Assessing the quantitative reliability of solid-state 13C NMR spectra of kerogens across a gradient of thermal maturity.  

PubMed

Five type II kerogens, shown by elemental analysis and Rock-Eval pyrolysis to represent a gradient of thermal maturity, were further characterized using a range of solid-state 13C NMR spectroscopic techniques. 13C cross polarization (CP) NMR spectra of the kerogens confirmed the well-established pattern of increasing aromaticity with increasing thermal maturity. Spin counting showed that CP observability was around 50% for the immature kerogens, and only 14-25% for the mature kerogens. Spin counting also showed that the direct polarization (DP) observabilities were >80% for all but one of the kerogens. Despite the large differences in observability between the two techniques, aromaticities derived from corresponding CP and DP spectra differed by only 1-15%. The RESTORE technique showed that the low CP observability of the immature kerogens was due mostly to rapid T(1rho)H relaxation, whereas both rapid T(1rho)H relaxation and slow polarization transfer contributed to the low CP observability of the mature kerogens. PMID:16310345

Smernik, Ronald J; Schwark, Lorenz; Schmidt, Michael W I

2006-06-01

275

Using Solid-state NMR to Monitor the Molecular Consequences of Cryptococcus neoformans Melanization with Different Catecholamine Precursors  

PubMed Central

Melanins are a class of natural pigments associated with a wide range of biological functions, including microbial virulence, energy transduction, and protection against solar radiation. Because of their insolubility and structural heterogeneity, solid-state nuclear magnetic resonance (NMR) spectroscopy provides an unprecedented means to define the molecular architecture of these enigmatic pigments. The requirement of obligatory catecholamines for melanization of the pathogenic fungus Cryptococcus neoformans also offers unique opportunities for investigating melanin development. In the current study, pigments produced with L-dopa, methyl-L-dopa, epinephrine, and norepinephrine precursors are compared structurally using 13C and 1H magic-angle spinning (MAS) NMR. Striking structural differences were observed for both aromatic and aliphatic molecular constituents of the mature fungal pigment assemblies, thus making it possible to redefine the molecular prerequisites for formation of the aromatic domains of insoluble indole-based biopolymers, to rationalize their distinctive physical characteristics, and to delineate the role of cellular constituents in assembly of the melanized macromolecules with polysaccharides and fatty acyl chain-containing moieties. By achieving an augmented understanding of the mechanisms of C. neoformans melanin biosynthesis and cellular assembly, such studies can guide future drug discovery efforts related to melanin-associated virulence, resistance to tumor therapy, and production of melanin mimetics under cell-free conditions. PMID:22765382

Chatterjee, Subhasish; Prados-Rosales, Rafael; Frases, Susana; Itin, Boris; Casadevall, Arturo; Stark, Ruth E.

2012-01-01

276

Direct observation of cell wall structure in living plant tissues by solid-state C NMR spectroscopy.  

PubMed

Solid-state (13)C nuclear magnetic resonance (NMR) spectra of the following intact plant tissues were recorded by the crosspolarization magic-angle spinning technique: celery (Apium graveolens L.) collenchyma; carob bean (Ceratonia siliqua L.), fenugreek (Trigonella foenum-graecum L.), and nasturtium (Tropaeolum majus L.) endosperm; and lupin (Lupinus polyphyllus Lindl.) seed cotyledons. All these tissues had thickened cell walls which allowed them to withstand the centrifugal forces of magic angle spinning and which, except in the case of lupin seeds, dominated the NMR spectra. The celery collenchyma cell walls gave spectra typical of dicot primary cell walls. The carob bean and fenugreek seed spectra were dominated by resonances from galactomannans, which showed little sign of crystalline order. Resonances from beta(1,4')-d galactan were visible in the lupin seed spectrum, but there was much interference from protein. The nasturtium seed spectrum was largely derived from a xyloglucan, in which the conformation of the glucan core chain appeared to be intermediate between the solution form and solid forms of cellulose. PMID:16667266

Jarvis, M C; Apperley, D C

1990-01-01

277

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

278

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

PubMed Central

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

2013-01-01

279

Chemical structures of swine-manure chars produced under different carbonization conditions investigated by advanced solid-state 13C nuclear magnetic resonance (NMR) spectroscopy  

Technology Transfer Automated Retrieval System (TEKTRAN)

Two types of swine manure chars, hydrothermally-produced hydrochar and slow-pyrolysis pyrochar, and their raw swine manure solid were characterized using advanced 13C solid-state nuclear magnetic resonance (NMR) spectroscopy. Compared with the parent raw swine manure, both hydrochars and pyrochar di...

280

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

PubMed

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

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

2002-06-01

281

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. PMID:24065828

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

2013-01-01

282

Probing porous media with gas diffusion NMR  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

283

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

PubMed

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

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

2015-03-01

284

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

285

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

286

Differences between lignin in unprocessed wood, milled wood, mutant wood, and extracted lignin detected by 13C solid-state NMR.  

PubMed

Solid-state 13C nuclear magnetic resonance (NMR) spectroscopy was applied to intact and isolated loblolly pine wood samples to identify potential structural changes induced by tree age, milling, lignin extraction, or naturally occurring mutations. Special attention was paid to ketone and aldehyde as well as nonpolar alkyl groups, which could be observed at low concentrations (<2 in 1000 C) using improved spinning-sideband suppression with gated decoupling. Carbonyl structures were present in intact wood, and there are more keto groups than aldehydes. Their concentrations increased from juvenile to mature wood and with milling time, whereas extraction did not alter the C=O fraction. Significant amounts of aldehyde and dihydroconiferyl alcohol residues were present in coniferyl aldehyde dehydrogenase-deficient wood, confirming solution-state NMR spectra of the corresponding lignin. These results demonstrate the utility of solid-state NMR as an assay for changes in the lignin structure of genetically modified plants. PMID:17177487

Mao, Jingdong; Holtman, Kevin M; Scott, Jay T; Kadla, John F; Schmidt-Rohr, Klaus

2006-12-27

287

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.

288

33S NMR cryogenic probe for taurine detection  

NASA Astrophysics Data System (ADS)

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

Hobo, Fumio; Takahashi, Masato; Maeda, Hideaki

2009-03-01

289

Solid state 1H NMR studies of cell wall materials of potatoes  

NASA Astrophysics Data System (ADS)

Cell wall materials from potatoes ( Solanum tuberosum) prepared by two different methods have been studied using NMR proton relaxation times. Spin lattice relaxation in both the rotating and laboratory frames as well as transverse relaxation have been measured over a range of temperatures and hydration levels. It was observed that the sample prepared using a DMSO extraction showed anomalous behaviour of spin lattice relaxation in the laboratory frame probably due to residual solvent in the sample. Spin lattice relaxation in the laboratory frame is the result of hydroxymethyl rotation and another unidentified high frequency motion. In the rotating frame relaxation is adequately explained by hydroxymethyl rotation alone. In neither experiment is methyl group rotation observed, calculation suggests that this is due to the low density of methyl groups in the sample. Non-freezing water in potato cell walls, ?-cellulose and pectin was found about 0.2, 0.04 and 0.18 g per gram dry matter, indicating preferable hydration of pectin compared to cellulose. The effects of hydration are most noticeable in the measurements that reflect low frequency motions, particularly transverse relaxation, where both second moments and the relative intensity of signals arising from immobile material are reduced by hydration.

Tang, Huiru; Belton, Peter S.; Ng, Annie; Waldron, Keith W.; Ryden, Peter

1999-04-01

290

A structural investigation of the alkali metal site distribution within bioactive glass using neutron diffraction and multinuclear solid state NMR.  

PubMed

The atomic-scale structure of Bioglass and the effect of substituting lithium for sodium within these glasses have been investigated using neutron diffraction and solid state magic angle spinning (MAS) NMR. Applying an effective isomorphic substitution difference function to the neutron diffraction data has enabled the Na-O and Li-O nearest-neighbour correlations to be isolated from the overlapping Ca-O, O-(P)-O and O-(Si)-O correlations. These results reveal that Na and Li behave in a similar manner within the glassy matrix and do not disrupt the short range order of the network former. Residual differences are attributed solely to the variation in ionic radius between the two species. Successful simplification of the 2 < r (Å) < 3 region via the difference method has enabled all the nearest neighbour correlations to be deconvolved. The diffraction data provides the first direct experimental evidence of split Na-O nearest-neighbour correlations in these melt quench bioactive glasses, and an analogous splitting of the Li-O correlations. The observed correlations are attributed to the metal ions bonded either to bridging or to non-bridging oxygen atoms. (23)Na triple quantum MAS (3QMAS) NMR data corroborates the split Na-O correlations. The structural sites present will be intimately related to the release properties of the glass system in physiological fluids such as plasma and saliva, and hence to the bioactivity of the material. Detailed structural knowledge is therefore a prerequisite for optimizing material design. PMID:22868255

Martin, Richard A; Twyman, Helen L; Rees, Gregory J; Smith, Jodie M; Barney, Emma R; Smith, Mark E; Hanna, John V; Newport, Robert J

2012-09-21

291

Investigation of drug-excipient interactions in lapatinib amorphous solid dispersions using solid-state NMR spectroscopy.  

PubMed

This study investigated the presence of specific drug-excipient interactions in amorphous solid dispersions of lapatinib (LB) and four commonly used pharmaceutical polymers, including Soluplus, polyvinylpyrrolidone vinyl acetate (PVPVA), hydroxypropylmethylcellulose acetate succinate (HPMCAS), and hydroxypropylmethylcellulose phthalate (HPMCP). Based on predicted pKa differences, LB was hypothesized to exhibit a specific ionic interaction with HPMCP, and possibly with HPMCAS, while Soluplus and PVPVA were studied as controls without ionizable functionality. Thermal studies showed a single glass transition (Tg) for each dispersion, in close agreement with predicted values for Soluplus, PVPVA, and HPMCAS systems. However, the Tg values of LB-HPMCP solid dispersions were markedly higher than predicted values, indicating a strong intermolecular interaction between LB and HPMCP. (15)N solid-state NMR provided direct spectroscopic evidence for protonation of LB (i.e., salt formation) within the HPMCP solid dispersions. (1)H T1 and (1)H T1? relaxation studies of the dispersions supported the ionic interaction hypothesis, and indicated multiple phases in the cases of excess drug or polymer. In addition, the dissolution and stability behavior of each system was examined. Both acidic polymers, HPMCAS and HPMCP, effectively inhibited the crystallization of LB on accelerated stability, likely owing to beneficial strong intermolecular hydrogen and/or specific ionic bonds with the acidic polymers. Soluplus and PVPVA showed poor physical properties on stability and subsequently poor crystallization inhibition. PMID:25585133

Song, Yang; Yang, Xinghao; Chen, Xin; Nie, Haichen; Byrn, Stephen; Lubach, Joseph W

2015-03-01

292

Characterization of Phosphate Sequestration by a Lanthanum Modified Bentonite Clay: A Solid-State NMR, EXAFS, and PXRD Study.  

PubMed

Phosphate (Pi) sequestration by a lanthanum (La) exchanged clay mineral (La-Bentonite), which is extensively used in chemical lake restoration, was investigated on the molecular level using a combination of (31)P and (139)La solid state NMR spectroscopy (SSNMR), extended X-ray absorption spectroscopy (EXAFS), powder X-ray diffraction (PXRD) and sorption studies. (31)P SSNMR show that all Pi was immobilized as rhabdophane (LaPO4·n H2O, n ? 3), which was further supported by (139)La SSNMR and EXAFS. However, PXRD results were ambiguous with respect to rhabdophane and monazite (LaPO4). Adsorption studies showed that at dissolved organic carbon (DOC) concentration above ca. 250 ?M the binding capacity was only 50% of the theoretical value or even less. No other La or Pi phases were detected by SSNMR and EXAFS indicating the effect of DOC is kinetic. Moreover, (31)P SSNMR showed that rhabdophane formed upon Pi sequestration is in close proximity to the clay matrix. PMID:25747941

Dithmer, Line; Lipton, Andrew S; Reitzel, Kasper; Warner, Terence E; Lundberg, Daniel; Nielsen, Ulla Gro

2015-04-01

293

Solid-state 19F MAS NMR study on the conformation and molecular mobility of poly(chlorotrifluoroethylene).  

PubMed

The temperature dependence of molecular mobility and conformational changes of poly(chlorotrifluoro- ethylene) (PCTFE) have been investigated by solid-state (19)F magic angle spinning (MAS) NMR spectroscopy. The pulse techniques of dipolar-filter and T(1rho)-filter allow selective observation of the amorphous and crystalline domains, respectively. The temperature dependence of T(1rho) (F) revealed that the segmental motion in the amorphous domain becomes vigorous above ca 80 degrees C, which is well above the glass transition (T(g)) temperature (52 degrees C) and more close to the beta-relaxation temperature (95 degrees C). On the other hand, vigorous molecular motions in the crystalline domain occur above 120 degrees C, which is much below the melting temperature (212 degrees C). This indicates that the polymer chains in the PCTFE crystallites are more mobile than those of typical semicrystalline fluoropolymers like poly(vinylidene fluoride) (PVDF), which can be associated with structural imperfections in the crystallites. In addition, the density functional theory (DFT) calculations of (19)F magnetic shielding suggest that the high-frequency shifts observed for the crystalline signals above 80 degrees C can be ascribed to the conformational change around meso diads toward more twisted and/or helical conformations in the main chain. PMID:17372960

Tatsuno, Hiroto; Aimi, Keitaro; Ando, Shinji

2007-05-01

294

Advanced solid-state NMR techniques for characterization of membrane protein structure and dynamics: Application to Anabaena Sensory Rhodopsin.  

PubMed

Studies of the structure, dynamics, and function of membrane proteins (MPs) have long been considered one of the main applications of solid-state NMR (SSNMR). Advances in instrumentation, and the plethora of new SSNMR methodologies developed over the past decade have resulted in a number of high-resolution structures and structural models of both bitopic and polytopic ?-helical MPs. The necessity to retain lipids in the sample, the high proportion of one type of secondary structure, differential dynamics, and the possibility of local disorder in the loop regions all create challenges for structure determination. In this Perspective article we describe our recent efforts directed at determining the structure and functional dynamics of Anabaena Sensory Rhodopsin, a heptahelical transmembrane (7TM) protein. We review some of the established and emerging methods which can be utilized for SSNMR-based structure determination, with a particular focus on those used for ASR, a bacterial protein which shares its 7TM architecture with G-protein coupled receptors. PMID:25637099

Ward, Meaghan E; Brown, Leonid S; Ladizhansky, Vladimir

2015-04-01

295

Integrating Solid-State NMR and Computational Modeling to Investigate the Structure and Dynamics of Membrane-Associated Ghrelin  

PubMed Central

The peptide hormone ghrelin activates the growth hormone secretagogue receptor 1a, also known as the ghrelin receptor. This 28-residue peptide is acylated at Ser3 and is the only peptide hormone in the human body that is lipid-modified by an octanoyl group. Little is known about the structure and dynamics of membrane-associated ghrelin. We carried out solid-state NMR studies of ghrelin in lipid vesicles, followed by computational modeling of the peptide using Rosetta. Isotropic chemical shift data of isotopically labeled ghrelin provide information about the peptide’s secondary structure. Spin diffusion experiments indicate that ghrelin binds to membranes via its lipidated Ser3. Further, Phe4, as well as electrostatics involving the peptide’s positively charged residues and lipid polar headgroups, contribute to the binding energy. Other than the lipid anchor, ghrelin is highly flexible and mobile at the membrane surface. This observation is supported by our predicted model ensemble, which is in good agreement with experimentally determined chemical shifts. In the final ensemble of models, residues 8–17 form an ?-helix, while residues 21–23 and 26–27 often adopt a polyproline II helical conformation. These helices appear to assist the peptide in forming an amphipathic conformation so that it can bind to the membrane. PMID:25803439

Els-Heindl, Sylvia; Chollet, Constance; Scheidt, Holger A.; Beck-Sickinger, Annette G.; Meiler, Jens; Huster, Daniel

2015-01-01

296

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

USGS Publications Warehouse

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

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

1996-01-01

297

Phosphate Ions in Bone: Identification of a Calcium–Organic Phosphate Complex by 31 P Solid-State NMR Spectroscopy at Early Stages of Mineralization  

Microsoft Academic Search

Previous 31P cross-polarization and differential cross-polarization magic angle spinning (CP\\/MAS and DCP\\/MAS) solid-state NMR spectroscopy studies of native bone and of the isolated crystals of the calcified matrix synthesized by osteoblasts in cell culture identified and characterized the major PO 4 -3 phosphate components of the mineral phase. The isotropic and anisotropic chemical shift parameters of the minor HPO 4

Y. Wu; J. L. Ackerman; E. S. Strawich; C. Rey; H.-M. Kim; M. J. Glimcher

2003-01-01

298

VARIATION IN THE STRUCTURE OF CONDUCTING POLYANILINE WITH AND WITHOUT THE PRESENCE OF TEMPLATE DURING ENZYMATIC POLYMERIZATION: A SOLID-STATE NMR STUDY  

Microsoft Academic Search

Polyanilines (PANI) were synthesized from peroxidase-catalyzed polymerization of aniline with and without the presence of a template in the aqueous buffer solution of pH 4.3. The template used was poly(vinylphosphonic acid) (PVP). Solid-state C and N CP\\/MAS NMR techniques were applied to characterize the structure of polyaniline in its self-doped conducting, dedoped base, and redoped conducting form of PANI. The

Sangrama K. Sahoo; Ramaswamy Nagarajan; Shuva Chakraborty; Lynne A. Samuelson; Jayant Kumar; Ashok L. Cholli

2002-01-01

299

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

SciTech Connect

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

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

2014-11-01

300

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

NASA Astrophysics Data System (ADS)

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

Gopinath, T.; Veglia, Gianluigi

2013-05-01

301

Fluid Mechanical Matching of H +ATP Synthase Subunit c-Ring with Lipid Membranes Revealed by 2H Solid-State NMR  

Microsoft Academic Search

The F1Fo-ATP synthase utilizes the transmembrane H+ gradient for the synthesis of ATP. Fo subunit c-ring plays a key role in transporting H+ through Fo in the membrane. We investigated the interactions of Escherichia coli subunit c with dimyristoylphosphatidylcholine (DMPC-d54) at lipid\\/protein ratios of 50:1 and 20:1 by means of 2H-solid-state NMR. In the liquid-crystalline state of DMPC, the 2H-NMR

Masatoshi Kobayashi; Andrey V. Struts; Toshimichi Fujiwara; Michael F. Brown; Hideo Akutsu

2008-01-01

302

Membrane structure and conformational changes of the antibiotic heterodimeric peptide distinctin by solid-state NMR spectroscopy  

PubMed Central

The heterodimeric antimicrobial peptide distinctin is composed of 2 linear peptide chains of 22- and 25-aa residues that are connected by a single intermolecular S-S bond. This heterodimer has been considered to be a unique example of a previously unrecorded class of bioactive peptides. Here the 2 distinctin chains were prepared by chemical peptide synthesis in quantitative amounts and labeled with 15N, as well as 15N and 2H, at selected residues, respectively, and the heterodimer was formed by oxidation. CD spectroscopy indicates a high content of helical secondary structures when associated with POPC/POPG 3:1 vesicles or in membrane-mimetic environments. The propensity for helix formation follows the order heterodimer >chain 2 >chain 1, suggesting that peptide-peptide and peptide-lipid interactions both help in stabilizing this secondary structure. In a subsequent step the peptides were reconstituted into oriented phospholipid bilayers and investigated by 2H and proton-decoupled 15N solid-state NMR spectroscopy. Whereas chain 2 stably inserts into the membrane at orientations close to perfectly parallel to the membrane surface in the presence or absence of chain 1, the latter adopts a more tilted alignment, which further increases in the heterodimer. The data suggest that membrane interactions result in considerable conformational rearrangements of the heterodimer. Therefore, chain 2 stably anchors the heterodimer in the membrane, whereas chain 1 interacts more loosely with the bilayer. These structural observations are consistent with the antimicrobial activities when the individual chains are compared to the dimer. PMID:19805350

Resende, Jarbas M.; Moraes, Cléria Mendonça; Munhoz, Victor H. O.; Aisenbrey, Christopher; Verly, Rodrigo M.; Bertani, Philippe; Cesar, Amary; Piló-Veloso, Dorila; Bechinger, Burkhard

2009-01-01

303

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

SciTech Connect

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

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

2004-02-01

304

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

PubMed Central

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

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

2014-01-01

305

High-yield expression and purification of isotopically labeled cytochrome P450 monooxygenases for solid-state NMR spectroscopy  

PubMed Central

Cytochrome P450 monooxygenases (P450s), which represent the major group of drug metabolizing enzymes in humans, also catalyze important synthetic and detoxicative reactions in insects, plants and many microbes. Flexibilities in their catalytic sites and membrane associations are thought to play central roles in substrate binding and catalytic specificity. To date, E. coli expression strategies for structural analysis of eukaryotic membrane-bound P450s by X-ray crystallography have necessitated full or partial removal of their N-terminal signal anchor domain (SAD) and, often, replacement of residues more peripherally associated with the membrane (such as the F-G loop region). Even with these modifications, investigations of P450 structural flexibility remain challenging with multiple single crystal conditions needed to identify spatial variations between substrate-free and different substrate-bound forms. To overcome these limitations, we have developed methods for the efficient expression of 13C- and 15N-labeled P450s and analysis of their structures by magic-angle spinning solid-state NMR (SSNMR) spectroscopy. In the presence of co-expressed GroEL and GroES chaperones, full-length (53 kDa) Arabidopsis 13C,15N-labeled CYP98A3 is expressed at yields of 2–4 mg per liter of minimal media without the necessity of generating side chain modifications or N-terminal deletions. Precipitated CYP98A3 generates high quality SSNMR spectra consistent with a homogeneous, folded protein. These data highlight the potential of these methodologies to contribute to the structural analysis of membrane-bound proteins. PMID:18005930

Rupasinghe, Sanjeewa G.; Duan, Hui; Frericks Schmidt, Heather L.; Berthold, Deborah A.; Rienstra, Chad M.; Schuler, Mary A.

2008-01-01

306

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

PubMed

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

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

2014-01-21

307

The Nature of Polymerization in Silicate Glasses and Melts: Solid State NMR, Modeling and Qauntum Chemicial Calculations.  

NASA Astrophysics Data System (ADS)

Silicate melts are among the dominant constituents of the upper mantle and crust. The full understanding of atomic scale disorder is essential to the macroscopic properties of the melts such as viscosity and configurational thermodynamic properties. Recently, we quantified the various aspects of the extent of disorder in ›r­’charge-balanced silicate glasses (non bridging (NBO)/T=0)›r­_ using solid state NMR and theoretical analysis, which allowed the degree of randomness of these systems to be determined in terms of the degree of Al-avoidance and degree of phase separations (Lee and Stebbins, Geochim. Cosmochim. Acta. 66, 303). Quantitative estimation of the framework connectivity and the atomic structures of depolymerized silicate melts (NBO/T>0), however, are still poorly known and framework cations and anions have often been assumed to be randomly distributed. Here, we explore the extent of disorder and the nature of polymerization in several binary and ternary silicate glasses with varying NBO/T using O-17 NMR at varying magnetic fields of 7.1, 9.4 and 14.1 T in conjunction with quantum chemical calculations. We also quantify the extent of intermixing among non-framework cations in mixed cation glasses, and calculate corresponding configurational thermodynamic properties. Non-random distribution among cations is clearly demonstrated from the relative populations of oxygen sites and the variation of distribution of structurally relevant NMR parameters with NBO/T from O-17 3QMAS NMR. The proportion of NBO (Na-O-Si) in Na2O-SiO2 glasses increases with NBO/T. Its chemical shift distribution decreases about 18 % from NBO/T of 0.7 to 2, suggesting a reduced configurational disorder around NBO with Na contents. Preferential interactions among framework cations are further manifested in peralkaline Ca- and Na- aluminosilicate glasses where depolymerization of networks selectively occurs at Si rather than Al tetrahedra, forming Na-O-Si or Ca-O-Si. The result is consistent with our quantum chemical calculations based on density functional theory where the silicate chain with Al-NBO has energy penalty of about 108 kJ/mol compared with the cluster with Ca-O-Si. The degree of Al avoidance (Q) among framework units in Na- aluminosilicate is larger than that in Ca-aluminosilicates, as recently observed for fully polymerized glasses. On the other hand, Q varies with NBO/T. The above results support the significant chemical order in silicate glasses that leads to considerable mixing among framework units. The degree of intermixing among non-framework cations in mixed-cation glasses has remained controversial. The population of each Na-NBO in Ca-Na and Ba-Na mixed cation silicate glasses is smaller than the prediction given from random distribution of these cations, and thus supports the preference for dissimilar pairs of cations, which could explain a decrease in diffusivity in these melts. In this study, we provide new insights into the structure of silicate glasses with varying NBO/T, highlighting more complete, atomic-level understanding on the dynamic processes in silicate magmas.

Lee, S.; Stebbins, J. F.; Mysen, B.; Cody, G. D.

2002-12-01

308

NMR-based structural modeling of graphite oxide using multidimensional 13C solid-state NMR and ab initio chemical shift calculations.  

PubMed

Chemically modified graphenes and other graphite-based materials have attracted growing interest for their unique potential as lightweight electronic and structural nanomaterials. It is an important challenge to construct structural models of noncrystalline graphite-based materials on the basis of NMR or other spectroscopic data. To address this challenge, a solid-state NMR (SSNMR)-based structural modeling approach is presented on graphite oxide (GO), which is a prominent precursor and interesting benchmark system of modified graphene. An experimental 2D (13)C double-quantum/single-quantum correlation SSNMR spectrum of (13)C-labeled GO was compared with spectra simulated for different structural models using ab initio geometry optimization and chemical shift calculations. The results show that the spectral features of the GO sample are best reproduced by a geometry-optimized structural model that is based on the Lerf-Klinowski model (Lerf, A. et al. Phys. Chem. B 1998, 102, 4477); this model is composed of interconnected sp(2), 1,2-epoxide, and COH carbons. This study also convincingly excludes the possibility of other previously proposed models, including the highly oxidized structures involving 1,3-epoxide carbons (Szabo, I. et al. Chem. Mater. 2006, 18, 2740). (13)C chemical shift anisotropy (CSA) patterns measured by a 2D (13)C CSA/isotropic shift correlation SSNMR were well reproduced by the chemical shift tensor obtained by the ab initio calculation for the former model. The approach presented here is likely to be applicable to other chemically modified graphenes and graphite-based systems. PMID:20359218

Casabianca, Leah B; Shaibat, Medhat A; Cai, Weiwei W; Park, Sungjin; Piner, Richard; Ruoff, Rodney S; Ishii, Yoshitaka

2010-04-28

309

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

PubMed

A massive interest has been generated lately by the improvement of solid-state magic-angle spinning (MAS) NMR methods for the study of a broad range of paramagnetic organic and inorganic materials. The open-shell cations at the origin of this paramagnetism can be metals, transition metals, or rare-earth elements. Actinide-bearing compounds and their 5f unpaired electrons remain elusive in this intensive research area due to their well-known high radiotoxicity. A dedicated effort enabling the handling of these highly radioactive materials now allows their analysis using high-resolution MAS NMR (>55 kHz). Here, the study of the local structure of a series of actinide dioxides, namely, ThO2, UO2, NpO2, PuO2, and AmO2, using solid-state (17)O MAS NMR is reported. An important increase of the spectral resolution is found due to the removal of the dipolar broadening proving the efficiency of this technique for structural analysis. The NMR parameters in these systems with numerous and unpaired 5f electrons were interpreted using an empirical approach. Single-ion model calculations were performed for the first time to determine the z component of electron spin on each of the actinide atoms, which is proportional to the shifts. A similar variation thereof was observed only for the heavier actinides of this study. PMID:24926812

Martel, Laura; Magnani, Nicola; Vigier, Jean-Francois; Boshoven, Jacobus; Selfslag, Chris; Farnan, Ian; Griveau, Jean-Christophe; Somers, Joseph; Fanghänel, Thomas

2014-07-01

310

Identification of lithium-sulfur battery discharge products through 6Li and 33S solid-state MAS and 7Li solution NMR spectroscopy  

NASA Astrophysics Data System (ADS)

6Li and 33S solid-state magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy was used to identify the discharge products in lithium-sulfur (Li-S) battery cathodes. Cathodes were stopped at different potentials throughout battery discharge and measured ex-situ to obtain chemical shifts and T2 relaxation rates of the products formed. The chemical shifts in the spectra of both 6Li and 33S NMR demonstrate that long-chain, soluble lithium polysulfide species formed at the beginning of discharge are indistinguishable from each other (similar chemical shifts), while short-chain, insoluble polysulfide species that form at the end of discharge (presumably Li2S2 and Li2S) have a different chemical shift, thus distinguishing them from the soluble long-chain products. T2 relaxation measurements of discharged cathodes were also performed which resulted in two groupings of T2 rates that follow a trend and support the previous conclusions that long-chain polysulfide species are converted to shorter chain species during discharge. Through the complementary techniques of 1-D 6Li and 33S solid-state MAS NMR spectroscopy, solution 7Li and 1H NMR spectroscopy, and T2 relaxation rate measurements, structural information about the discharge products of Li-S batteries is obtained.

Huff, Laura A.; Rapp, Jennifer L.; Baughman, Jessi A.; Rinaldi, Peter L.; Gewirth, Andrew A.

2015-01-01

311

INVESTIGATING THE EFFECT OF ENANTIOMERIC RATIO AND PREPARATION METHOD ON CRYSTALLINE FORMS OF PROLINE USING SOLID-STATE NMR SPECTROSCOPY  

E-print Network

Chiral molecules are prevalent among currently marketed pharmaceutical products, many of which are solid formulations. The solid-state form of a drug can have a dramatic effect on its solubility, dissolution rate (hence ...

Berendt, Robert Thomas

2010-08-26

312

31P Solid State NMR Studies of Metal Selenophosphates Containing [P2Se6]4-, [P4Se10]4-, [PSe4]3-, [P2Se7]4-, and [P2Se9]4-Ligands  

E-print Network

31P Solid State NMR Studies of Metal Selenophosphates Containing [P2Se6]4-, [P4Se10]4-, [PSe4]3-, [P2Se7]4-, and [P2Se9]4- Ligands Christian G. Canlas, Mercouri G. Kanatzidis, and David P. Weliky P solid-state nuclear magnetic resonance (NMR) spectra of 12 metal-containing selenophosphates have

Weliky, David

313

In situ solid state 11B MAS-NMR studies of the thermal decomposition of ammonia borane: mechanistic studies of the hydrogen release pathways from a solid state hydrogen storage material.  

PubMed

The mechanism of hydrogen release from solid state ammonia borane (AB) has been investigated via in situ solid state (11)B and (11)B{(1)H} MAS-NMR techniques in external fields of 7.1 T and 18.8 T at a decomposition temperature of 88 degrees C, well below the reported melting point. The decomposition of AB is well described by an induction, nucleation and growth mechanistic pathway. During the induction period, little hydrogen is released from AB; however, a new species identified as a mobile phase of AB is observed in the (11)B NMR spectra. Subsequent to induction, at reaction times when hydrogen is initially being released, three additional species are observed: the diammoniate of diborane (DADB), [(NH(3))(2)BH(2)](+)[BH(4)](-), and two BH(2)N(2) species believed to be the linear (NH(3)BH(2)NH(2)BH(3)) and cyclic dimer (NH(2)BH(2))(2) of aminoborane. At longer reaction times the sharper features are replaced by broad, structureless peaks of a complex polymeric aminoborane (PAB) containing both BH(2)N(2) and BHN(3) species. The following mechanistic model for the induction, nucleation and growth for AB decomposition leading to formation of hydrogen is proposed: (i) an induction period that yields a mobile phase of AB caused by disruption of the dihydrogen bonds; (ii) nucleation that yields reactive DADB from the mobile AB; and (iii) growth that includes a bimolecular reaction between DADB and AB to release the stored hydrogen. PMID:17415495

Stowe, Ashley C; Shaw, Wendy J; Linehan, John C; Schmid, Benjamin; Autrey, Tom

2007-04-21

314

In situ solid state B-11 MAS-NMR studies of the thermal decomposition of ammonia borane: mechanistic studies of the hydrogen release pathways from a solid state hydrogen storage material  

SciTech Connect

The mechanism of hydrogen release from solid state ammonia borane (AB) has been investigated via in situ solid state 11B{1H} MAS-NMR techniques in external fields of 7.06 T and 18.8 T at a decomposition temperature of 88 oC, well below the reported melting point. The decomposition of AB is well described by an induction, nucleation and growth mechanistic pathway. During the induction period, little hydrogen is released from AB; however, a new species identified as a mobile phase of AB is observed in the 11B NMR spectra. Subsequent to induction, at reaction times when hydrogen is initially being released, three additional species are observed: the diammoniate of diborane (DADB), [(NH3)2BH2]+[BH4]-, and two BH2N2 species believed to be the linear (NH3BH2NH2BH3) and cyclic dimer (NH2BH2)2 of aminoborane. At longer reaction times the sharper features are replaced by broad, structureless peaks of a complex polymeric aminoborane (PAB) containing both BH2N2 and BHN3 species. We propose the following mechanistic model for the induction, nucleation and growth for AB decomposition leading to formation of hydrogen: (1) an induction period that yields a mobile phase of AB caused by disruption of the dihydrogen bonds, (2) nucleation that yields reactive DADB from the mobile AB and (3) growth that includes a bimolecular reaction between DADB and AB to release the stored hydrogen. Support for this work by the U.S. Department of Energy, Office of Science, Basic Energy Sciences is gratefully acknowledged. A portion of the research described in this paper was performed in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the U.S. Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory.

Stowe, Ashley C.; Shaw, Wendy J.; Linehan, John C.; Schmid, Benjamin; Autrey, Thomas

2007-02-20

315

Quantitation of aliphatic suberin in Quercus suber L. cork by FTIR spectroscopy and solid-state (13)C-NMR spectroscopy.  

PubMed

This work determined that the percentage of suberin in cork may be found by solid-state (13)C cross polarization/magic angle spinning (CP/MAS) NMR spectroscopy and by FTIR with photoacoustic detection (FTIR-PAS) spectroscopy. A linear relationship is found between the suberin content measured through CP/MAS spectral areas and that measured gravimetrically. Furthermore, application of a partial least squares (PLS1) regression model to the NMR and gravimetric data sets clearly correlates the two sets, enabling suberin quantification with 90% precision. Suberin quantitation by FTIR-PAS spectroscopy is also achieved by a PLS1 regression model, giving 90% accurate estimates of the percentage of suberin in cork. Therefore, (13)C-CP/MAS NMR and FTIR-PAS proved to be useful and accurate noninvasive techniques to quantify suberin in cork, thus avoiding the traditional time consuming and destructive chemical methods. PMID:11054654

Lopes, M H; Neto, C P; Barros, A S; Rutledge, D; Delgadillo, I; Gil, A M

2000-01-01

316

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

E-print Network

. The Gaussian beam is reflected by curved mirrors inside the DNP-MAS-NMR probe to be incident at the sample larger electronic magnetic moments to nuclei, which opens the possibility for NMR signals to be increased gyrotron is used as the microwave source for this magnetic field strength and 284 MHz 1 H DNP

Watts, Anthony

317

Determination of Structural Topology of a Membrane Protein in Lipid -Bilayers using Polarization Optimized Experiments (POE) for Static and MAS Solid State NMR Spectroscopy  

PubMed Central

The low sensitivity inherent to both the static and magic angle spinning techniques of solid-state NMR (ssNMR) spectroscopy has thus far limited the routine application of multidimensional experiments to determine the structure of membrane proteins in lipid bilayers. Here, we demonstrate the advantage of using a recently developed class of experiments, polarization optimized experiments (POE), for both static and MAS spectroscopy to achieve higher sensitivity and substantial time-savings for 2D and 3D experiments. We used sarcolipin, a single pass membrane protein, reconstituted in oriented bicelles (for oriented ssNMR) and multilamellar vesicles (for MAS ssNMR) as a benchmark. The restraints derived by these experiments are then combined into a hybrid energy function to allow simultaneous determination of structure and topology. The resulting structural ensemble converged to a helical conformation with a backbone RMSD ? 0.44 Å, a tilt angle of 24° ± 1°, and an azimuthal angle of 55° ± 6°. This work represents a crucial first step toward obtaining high-resolution structures of large membrane proteins using combined multidimensional O-ssNMR and MAS-ssNMR. PMID:23963722

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

2013-01-01

318

Study of host-guest interactions in benzodiazacoronands by means of solid state NMR spectroscopy, X-ray diffraction and quantum mechanical computations.  

PubMed

In this work we present solid state data for five host-guest complexes formed by N-(4,19-dioxo-2,8,15,21-tetraoxa-5,18-diazatricyclohexacosa-1(25),9(14),10,12,22(26),23-hexaen-26-yl)-benzamide (1) belonging to the group of benzodiazacoronands, achiral compounds for which chiral crystals were found (J. Kalisiak and J. Jurczak, Cryst. Growth Des., 2006, 6, 20). The X-ray structure was resolved for four of them. It was found that 1 crystallizes in P2(1)/c, P1 and P2(1)/n achiral space groups. Differentiation of molecular packing and the presence of guest molecules within the crystal lattice were analyzed with solid state NMR. An attempt was made to correlate changes in (13)C ?(ii) and (15)N ?(ii) chemical shift tensor values, obtained from analysis of spinning sidebands of 1D and 2D (2D PASS) NMR spectra, with changes in the strength of hydrogen bonding. Quantum mechanical DFT GIAO calculations of NMR shielding parameters carried out on structures with coordinates taken from XRD were employed for signals assignment and verification of structural constraints. PMID:21384038

Nowicka, Katarzyna; Bujacz, Anna; Paluch, Piotr; Sobczuk, Adam; Jeziorna, Agata; Ciesielski, W?odzimierz; Bujacz, Grzegorz D; Jurczak, Janusz; Potrzebowski, Marek J

2011-04-14

319

Nanoscale spatial resolution probes for scanning thermal microscopy of solid state materials  

NASA Astrophysics Data System (ADS)

Scanning thermal microscopy (SThM) uses micromachined thermal sensors integrated in a force sensing cantilever with a nanoscale tip that can be highly useful for exploration of thermal management of nanoscale semiconductor devices as well as mapping of surface and subsurface properties of related materials. Whereas SThM is capable to image externally generated heat with nanoscale resolution, its ability to map and measure thermal conductivity of materials has been mainly limited to polymers or similar materials possessing low thermal conductivity in the range from 0.1 to 1 W m-1 K-1, with lateral resolution on the order of 1 ?m. In this paper, we use linked experimental and theoretical approaches to analyse thermal performance and sensitivity of the micromachined SThM probes in order to expand their applicability to a broader range of nanostructures from polymers to semiconductors and metals. We develop physical models of interlinked thermal and electrical phenomena in these probes and their interaction with the sample on the mesoscopic length scale of few tens of nm and then validate these models using experimental measurements of the real probes, which provided the basis for analysing SThM performance in exploration of nanostructures. Our study then highlights critical features of these probes, namely, the geometrical location of the thermal sensor with respect to the probe apex, thermal conductance of the probe to the support base, heat conduction to the surrounding gas, and the thermal conductivity of tip material adjacent to the apex. It furthermore allows us to propose a novel design of the SThM probe that incorporates a multiwall carbon nanotube or similar high thermal conductivity graphene sheet material with longitudinal dimensions on micrometre length scale positioned near the probe apex that can provide contact areas with the sample on the order of few tens of nm. The new sensor is predicted to provide greatly improved spatial resolution to thermal properties of nanostructures as well as to expand the sensitivity of the SThM probe to materials with heat conductivity values up to 100-1000 W m-1 K-1.

Tovee, P.; Pumarol, M.; Zeze, D.; Kjoller, Kevin; Kolosov, O.

2012-12-01

320

The core of Ure2p prion fibrils is formed by the N-terminal segment in a parallel cross-? structure: Evidence from solid state NMR  

PubMed Central

Intracellular fibril formation by Ure2p produces the non-Mendelian genetic element [URE3] in S. cerevisiae, making Ure2p a prion protein. We show that solid state NMR spectra of full-length Ure2p fibrils, seeded with infectious prions from a specific [URE3] strain and labeled with uniformly 15N,13C-enriched Ile, include strong, sharp signals from Ile residues in the globular C-terminal domain (CTD), with both helical and non-helical 13C chemical shifts. Treatment with proteinase K (PK) eliminates these CTD signals, leaving only non-helical signals from the Gln- and Asn-rich N-terminal segment, which are also observed in solid state NMR spectra of Ile-labeled fibrils formed by residues 1-89 of Ure2p. Thus, the N-terminal segment, or “prion domain” (PD), forms the fibril core, while CTD units are located outside the core. We additionally show that, after PK treatment, Ile-labeled Ure2p fibrils formed without prion seeding exhibit a broader set of solid state NMR signals than do the prion-seeded fibrils, consistent with the idea that structural variations within the PD core account for prion strains. Measurements of 13C-13C magnetic dipole-dipole couplings among 13C-labeled Ile carbonyl sites in full-length Ure2p fibrils support an in-register parallel ?-sheet structure for the PD core of Ure2p fibrils. Finally, we show that a model in which CTD units are attached rigidly to the parallel ?-sheet core is consistent with steric constraints. PMID:21497604

Kryndushkin, Dmitry S.; Wickner, Reed B.; Tycko, Robert

2011-01-01

321

Site discrimination in the crystalline borophosphate Na5B2P3O13 using advanced solid-state NMR techniques.  

PubMed

A comprehensive solid-state NMR investigation on crystalline Na(5)B(2)P(3)O(13) is presented. Triple-quantum magic angle spinning (TQMAS) and rotational echo double resonance (REDOR) studies are used for accurate determinations of the (11)B, (23)Na and (31)P interaction parameters. Based on these results and complementary quantum mechanical calculations, plausible site assignments can be derived. Generally, the results show that detailed, quantitative information about structures in borophosphate compounds can be obtained by investigating both the local site environments characterized by chemical shift and quadrupolar interaction parameters and the correlated dipolar interactions to atoms in the second coordination sphere. PMID:17959362

Strojek, Wenzel; Fehse, Constanze Miriam; Eckert, Hellmut; Ewald, Bastian; Kniep, Rüdiger

2007-11-01

322

Effect of critical molecular weight of PEO in epoxy/EPO blends as characterized by advanced DSC and solid-state NMR  

NASA Astrophysics Data System (ADS)

The differential scanning calorimetry (DSC) and solid state NMR have been used to systematically study the length scale of the miscibility and local dynamics of the epoxy resin/poly(ethylene oxide) (ER/PEO) blends with different PEO molecular weight. By DSC, we found that the diffusion behavior of PEO with different Mw is an important factor in controlling these behaviors upon curing. We further employed two-dimensional 13C-1HPISEMA NMR experiment to elucidate the possible weak interaction and detailed local dynamics in ER/PEO blends. The CH2O group of PEO forms hydrogen bond with hydroxyl proton of cured-ER ether group, and its local dynamics frozen by such interaction. Our finding indicates that molecular weight (Mw) of PEO is a crucial factor in controlling the miscibility, chain dynamics and hydrogen bonding interaction in these blends.

Wang, Xiaoliang; Lu, Shoudong; Sun, Pingchuan; Xue, Gi

2013-03-01

323

Solid-state [sup 13]C NMR studies of ionic surfactants adsorbed on C-18 and C-8 silicas: Implications for micellar liquid chromatography  

SciTech Connect

Solid-state [sup 13]C NMR spectroscopy techniques, including cross polarization (CP), magic angle spinning (MAS), and high-power proton decoupling, have been used to study the interactions of two ionic surfactants with octadecylsilica (C-18) and octylsilica (C-8) HPLC stationary phases. The two surfactants, cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), are commonly used in micellar reversed-phase liquid chromatography (RPLC). Variable contact time CP/MAS [sup 13] C NMR data suggest that differences in selectivity between SDS and CTAB micellar RPLC are due to the differing nature of the SDS and CTAB-bonded phase association. For CTAB the association leads to a more hydrophobic bulk stationary phase, whereas SDS adsorption results in the formation of an anionic, hydrophilic surface layer. These results suggest that proper matching of surfactant monomer and bonded stationary phase is critical to ensure selective separations in micellar RPLC.

Lavine, B.K.; Hendayana, S.; Han, J.H.; Tetreault, J. (Clarkson Univ., Potsdam, NY (United States). Dept. of Chemistry); Cooper, W.T. III; He, Y. (Florida State Univ., Tallahassee, FL (United States). Dept. of Chemistry)

1994-07-01

324

Structural features of a bituminous coal and their changes during low-temperature oxidation and loss of volatiles investigated by advanced solid-state NMR spectroscopy  

USGS Publications Warehouse

Quantitative and advanced 13C solid-state NMR techniques were employed to investigate (i) the chemical structure of a high volatile bituminous coal, as well as (ii) chemical structural changes of this coal after evacuation of adsorbed gases, (iii) during oxidative air exposure at room temperature, and (iv) after oxidative heating in air at 75 ??C. The solid-state NMR techniques employed in this study included quantitative direct polarization/magic angle spinning (DP/MAS) at a high spinning speed of 14 kHz, cross polarization/total sideband suppression (CP/TOSS), dipolar dephasing, CH, CH2, and CHn selection, 13C chemical shift anisotropy (CSA) filtering, two-dimensional (2D) 1H-13C heteronuclear correlation NMR (HETCOR), and 2D HETCOR with 1H spin diffusion. With spectral editing techniques, we identified methyl CCH 3, rigid and mobile methylene CCH2C, methine CCH, quaternary Cq, aromatic CH, aromatic carbons bonded to alkyls, small-sized condensed aromatic moieties, and aromatic C-O groups. With direct polarization combined with spectral-editing techniques, we quantified 11 different types of functional groups. 1H-13C 2D HETCOR NMR experiments indicated spatial proximity of aromatic and alkyl moieties in cross-linked structures. The proton spin diffusion experiments indicated that the magnetization was not equilibrated at a 1H spin diffusion time of 5 ms. Therefore, the heterogeneity in spatial distribution of different functional groups should be above 2 nm. Recoupled C-H long-range dipolar dephasing showed that the fraction of large charcoal-like clusters of polycondensed aromatic rings was relatively small. The exposure of this coal to atmospheric oxygen at room temperature for 6 months did not result in obvious chemical structural changes of the coal, whereas heating at 75 ??C in air for 10 days led to oxidation of coal and generated some COO groups. Evacuation removed most volatiles and caused a significant reduction in aliphatic signals in its DP/MAS spectrum. DP/MAS, but not CP/MAS, allowed us to detect the changes during low-temperature oxidation and loss of volatiles. These results demonstrate the applicability of advanced solid-state NMR techniques in chemical characterization of coal. ?? 2010 American Chemical Society.

Mao, J.-D.; Schimmelmann, A.; Mastalerz, M.; Hatcher, P.G.; Li, Y.

2010-01-01

325

Energy and density measurements of sloshing ions in tandem-mirror-experiment upgrade using solid-state probe techniques  

SciTech Connect

The energy and flux of charge-exchange neutrals from the sloshing ions in the endplug of tandem-mirror-experiment upgrade were measured using solid-state probes. An average energy of the sloshing ions of 6 keV was inferred from the depth profile of deuterium implanted in a silicon sample exposed to the charge-exchange neutrals. A bounce-averaged Fokker--Planck code was used to calculate the sloshing-ion energy distribution. The calculated depth profile of deuterium in the silicon sample resulting from this energy distribution is in good agreement with the measured profile. Carbon resistance probes were used to measure the charge-exchange flux from which the central chord sloshing-ion line density was inferred. The line density of particles with energies>2 keV was deduced to account for 60% of the total plasma line density in the endplug. By folding the sloshing-ion line density into the diamagnetic loop data, it was shown that the 1/e radial extent of the sloshing ions remained relatively constant from shot to shot at 14 cm.

Hsu, W.L.; Bastasz, R.; Wampler, W.R.; Rensink, M.E.; Allen, S.L.; Grubb, D.P.; Simonen, T.C.

1985-07-01

326

51V solid-state NMR and density functional theory studies of vanadium environments in V(V)O2 dipicolinic acid complexes  

NASA Astrophysics Data System (ADS)

V51 solid-state NMR and density functional theory (DFT) investigations are reported for a series of pentacoordinate dioxovanadium(V)-dipicolinate [V(V )O2-dipicolinate] and heptacoordinate aquahydroxylamidooxovanadium(V)-dipicolinate [V(V)O-dipicolinate] complexes. These compounds are of interest because of their potency as phosphatase inhibitors as well as their insulin enhancing properties and potential for the treatment of diabetes. Experimental solid-state NMR results show that the electric field gradient tensors in the V(V )O2-dipicolinate derivatives are affected significantly by substitution on the dipicolinate ring and range from 5.8to8.3MHz. The chemical shift anisotropies show less dramatic variations with respect to the ligand changes and range between -550 and -600ppm. To gain insights on the origins of the NMR parameters, DFT calculations were conducted for an extensive series of the V(V )O2- and V(V)O-dipicolinate complexes. To assess the level of theory required for the accurate calculation of the V51 NMR parameters, different functionals, basis sets, and structural models were explored in the DFT study. It is shown that the original x-ray crystallographic geometries, including all counterions and solvation water molecules within 5Å of the vanadium, lead to the most accurate results. The choice of the functional and the basis set at a high level of theory has a relatively minor impact on the outcome of the chemical shift anisotropy calculations; however, the use of large basis sets is necessary for accurate calculations of the quadrupole coupling constants for several compounds of the V(V )O2 series. These studies demonstrate that even though the vanadium compounds under investigations exhibit distorted trigonal bipyramidal coordination geometry, they have a "perfect" trigonal bipyramidal electronic environment. This observation could potentially explain why vanadate and vanadium(V) adducts are often recognized as potent transition state analogs.

Bolte, Stephanie E.; Ooms, Kristopher J.; Polenova, Tatyana; Baruah, Bharat; Crans, Debbie C.; Smee, Jason J.

2008-02-01

327

A sup 95 Mo solid-state NMR study of hydrodesulfurization catalysts. 1. Formation of fresh HDS catalyst precursors by adsorption of polyoxomolybdates onto. gamma. -alumina  

SciTech Connect

The solid-state {sup 95}Mo NMR of oxomolybdates and polyoxomolybdates adsorbed to {gamma}-alumina was utilized to characterize the molybdenum species present at circa monolayer coverages of molybdenum. This represents the first attempt at using solid-state NMR to look directly at the molybdenum species on the surface of 'fresh' hydrodesulfurization catalyst precursors. The selectively excited central {plus minus}1/2 transition line shapes were obtained, by the solid-echo technique, for several polyoxomolybdates, which are considered model compounds of the surface molybdena species, as well as for the uncalcined and calcined catalysts at various loadings. The spectra were obtained for static and magic angle spinning samples. Static sample spectra of the catalysts reveal inhomogeneously broadened lines owing to a range of surface species being present. Magic and angle spinning spectra show the presence of four possible species on the surface of the uncalcined catalysts and two possible species present on the surface of calcined catalysts. Spikelet echo spectra identified static adsorbed species (speculated to be predominantly adsorbed tetrahedral/octahedral molybdena, and perhaps Al{sub 2}(MoO{sub 4}){sub 3}), and a dynamic species (speculated to be disordered, surface-interactive tetrahedral and octahedral molybdates), in the uncalcined catalyst samples. Upon calcination the line widths of the static and MAS spectra are increased, indicating a polymerization of the surface species to form a MoO{sub 3}-like phase. 67 refs.

Edwards, J.C.; Adams, R.D.; Ellis, P.D. (Univ. of South Carolina, Columbia (United States))

1990-11-07

328

The application of solid-state NMR spectroscopy to study candesartan cilexetil (TCV-116) membrane interactions. Comparative study with the AT1R antagonist drug olmesartan.  

PubMed

??1 receptor (AT1R) antagonists exert their antihypertensive effects by preventing the vasoconstrictive hormone AngII to bind to the AT1 receptor. It has been proposed that these biological effects are mediated through a two-step mechanism reaction. In the first step, they are incorporated in the core of the lipid bilayers and in the second step they reach the active site of the receptor through lateral diffusion. In this model, drug/membrane interactions are key elements for the drugs achieving inhibition at the AT1 receptor. In this work, the interactions of the prodrug candesartan cilexetil (TCV-116) with lipid bilayers are studied at molecular detail. Solid-state (13)C-CP/MAS, 2D (1)H-(1)H NOESY NMR spectroscopy and in silico calculations are used. TCV-116 and olmesartan, another drug which acts as an AT1R antagonist are compared for their dynamic effects in lipid bilayers using solid-state (2)H-NMR. We find a similar localization of TCV-116 compared to other AT1 antagonists in the intermediate polar region. In addition, we can identify specific local interactions. These interactions may be associated in part with the discrete pharmacological profiles observed for different antagonists. PMID:24946142

Ntountaniotis, Dimitrios; Kellici, Tahsin; Tzakos, Andreas; Kolokotroni, Pinelopi; Tselios, Theodore; Becker-Baldus, Johanna; Glaubitz, Clemens; Lin, Sonyan; Makriyannis, Alexandros; Mavromoustakos, Thomas

2014-10-01

329

Solid-state acid-base interactions in complexes of heterocyclic bases with dicarboxylic acids: crystallography, hydrogen bond analysis, and 15N NMR spectroscopy.  

PubMed

A cancer candidate, compound 1, is a weak base with two heterocyclic basic nitrogens and five hydrogen-bonding functional groups, and is sparingly soluble in water rendering it unsuitable for pharmaceutical development. The crystalline acid-base pairs of 1, collectively termed solid acid-base complexes, provide significant increases in the solubility and bioavailability compared to the free base, 1. Three dicarboxylic acid-base complexes, sesquisuccinate 2, dimalonate 3, and dimaleate 4, show the most favorable physicochemical profiles and are studied in greater detail. The structural analyses of the three complexes using crystal structure and solid-state NMR reveal that the proton-transfer behavior in these organic acid-base complexes vary successively correlating with Delta pKa. As a result, 2 is a neutral complex, 3 is a mixed ionic and zwitterionic complex and 4 is an ionic salt. The addition of the acidic components leads to maximized hydrogen bond interactions forming extended three-dimensional networks. Although structurally similar, the packing arrangements of the three complexes are considerably different due to the presence of multiple functional groups and the flexible backbone of 1. The findings in this study provide insight into the structural characteristics of complexes involving heterocyclic bases and carboxylic acids, and demonstrate that X-ray crystallography and 15N solid-state NMR are truly complementary in elucidating hydrogen bonding interactions and the degree of proton transfer of these complexes. PMID:16787084

Li, Z Jane; Abramov, Yuriy; Bordner, Jon; Leonard, Jason; Medek, Ales; Trask, Andrew V

2006-06-28

330

Induced Secondary Structure and Polymorphism in an Intrinsically Disordered Structural Linker of the CNS: Solid-State NMR and FTIR Spectroscopy of Myelin Basic Protein Bound to Actin  

PubMed Central

Abstract The 18.5 kDa isoform of myelin basic protein (MBP) is a peripheral membrane protein that maintains the structural integrity of the myelin sheath of the central nervous system by conjoining the cytoplasmic leaflets of oligodendrocytes and by linking the myelin membrane to the underlying cytoskeleton whose assembly it strongly promotes. It is a multifunctional, intrinsically disordered protein that behaves primarily as a structural stabilizer, but with elements of a transient or induced secondary structure that represent binding sites for calmodulin or SH3-domain-containing proteins, inter alia. In this study we used solid-state NMR (SSNMR) and Fourier transform infrared (FTIR) spectroscopy to study the conformation of 18.5 kDa MBP in association with actin microfilaments and bundles. FTIR spectroscopy of fully 13C,15N-labeled MBP complexed with unlabeled F-actin showed induced folding of both protein partners, viz., some increase in ?-sheet content in actin, and increases in both ?-helix and ?-sheet content in MBP, albeit with considerable extended structure remaining. Solid-state NMR spectroscopy revealed that MBP in MBP-actin assemblies is structurally heterogeneous but gains ordered secondary structure elements (both ?-helical and ?-sheet), particularly in the terminal fragments and in a central immunodominant epitope. The overall conformational polymorphism of MBP is consistent with its in vivo roles as both a linker (membranes and cytoskeleton) and a putative signaling hub. PMID:19134474

Ahmed, Mumdooh A.M.; Bamm, Vladimir V.; Shi, Lichi; Steiner-Mosonyi, Marta; Dawson, John F.; Brown, Leonid; Harauz, George; Ladizhansky, Vladimir

2009-01-01

331

Induced secondary structure and polymorphism in an intrinsically disordered structural linker of the CNS: solid-state NMR and FTIR spectroscopy of myelin basic protein bound to actin.  

PubMed

The 18.5 kDa isoform of myelin basic protein (MBP) is a peripheral membrane protein that maintains the structural integrity of the myelin sheath of the central nervous system by conjoining the cytoplasmic leaflets of oligodendrocytes and by linking the myelin membrane to the underlying cytoskeleton whose assembly it strongly promotes. It is a multifunctional, intrinsically disordered protein that behaves primarily as a structural stabilizer, but with elements of a transient or induced secondary structure that represent binding sites for calmodulin or SH3-domain-containing proteins, inter alia. In this study we used solid-state NMR (SSNMR) and Fourier transform infrared (FTIR) spectroscopy to study the conformation of 18.5 kDa MBP in association with actin microfilaments and bundles. FTIR spectroscopy of fully (13)C,(15)N-labeled MBP complexed with unlabeled F-actin showed induced folding of both protein partners, viz., some increase in beta-sheet content in actin, and increases in both alpha-helix and beta-sheet content in MBP, albeit with considerable extended structure remaining. Solid-state NMR spectroscopy revealed that MBP in MBP-actin assemblies is structurally heterogeneous but gains ordered secondary structure elements (both alpha-helical and beta-sheet), particularly in the terminal fragments and in a central immunodominant epitope. The overall conformational polymorphism of MBP is consistent with its in vivo roles as both a linker (membranes and cytoskeleton) and a putative signaling hub. PMID:19134474

Ahmed, Mumdooh A M; Bamm, Vladimir V; Shi, Lichi; Steiner-Mosonyi, Marta; Dawson, John F; Brown, Leonid; Harauz, George; Ladizhansky, Vladimir

2009-01-01

332

Tracing bacterial metabolism using multi-nuclear (1H, 2H, and 13C) Solid State NMR: Realizing an Idea Initiated by James Scott  

NASA Astrophysics Data System (ADS)

Approximately 6 years ago, while at the Geophysical Laboratory, James Scott became interested in the application of Solid State Nuclear Magnetic Resonance Spectroscopy to study bacterial metabolism. As often happens, other experiments intervened and the NMR experiments were not pursued. We have revisited Jame's question and find that using a multi-nuclear approach (1H, 2H, and 13C Solid State NMR) on laboratory cell culture has some distinct advantages. Our experiments involved batch cultures of E. coli (MG1655) harvested at stationary phase. In all experiments the growth medium consisted of MOPS medium for enterobacteria, where the substrate is glucose. In one set of experiments, 10 % of the water was D2O; in another 10 % of the glucose was per-deuterated. The control experiment used both water and glucose at natural isotopic abundance. A kill control of dead E. coli immersed in pure D2O for an extended period exhibited no deuterium incorporation. In both deuterium enriched experiments, considerable incorporation of deuterium into E. coli's biomolecular constituents was detected via 2H Solid State NMR. In the case of the D2O enriched experiment, 58 % of the incorporated deuterium is observed in a sharp peak at a frequency of 0.31 ppm, consistent with D incorporation in the cell membrane lipids, the remainder is observed in a broad peak at a higher frequency (centered at 5.4 ppm, but spanning out to beyond 10 ppm) that is consistent with D incorporation into predominantly DNA and RNA. In the case of the D-glucose experiments, 61 % of the deuterium is observed in a sharp resonance peak at 0.34 ppm, also consistent with D incorporation into membrane lipids, the remainder of the D is observed at a broad resonance peak centered at 4.3 ppm, consistent with D enrichment in glycogen. Deuterium abundance in the E. coli cells grown in 10 % D2O is nearly 2X greater than that grown with 10 % D-glucose. Very subtle differences are observed in both the 1H and 13C solid-state NMR experiments, most notably in the spectral region corresponding to glycogen H and C, respectively. Interestingly, whereas in both experiments the predominant site of incorporation was in the membrane lipids, the line width of the aliphatic-D resonance in the D2O enriched experiment is 67 % wider than that observed in the D-glucose enriched experiment. This difference could be due to greater residual 1H-2H dipolar coupling in membrane lipids synthesized with 10 % D2O due to D being incorporated during NADP(D) reduction of the fatty acid precursor during synthesis and the H-glucose being the source of carbon and hydrogen starting with acetyl-CoA. In the case of the D-glucose experiment, the narrower absorption line may be consistent with individual FA's being more homogeneously deuterated. Analysis of the membrane lipids is currently being performed via GCMS in order to gain potentially more insight to guide interpretation of the 2H solid state NMR spectra.

Cody, G.; Fogel, M. L.; Jin, K.; Griffen, P.; Steele, A.; Wang, Y.

2011-12-01

333

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

NASA Technical Reports Server (NTRS)

Measurements on the solid electrolyte cell (Ar + H(2) + H(2)S/CaS + CaF(2) + (Pt)//CaF(2)//(Pt) + CaF(2) + CaS/H(2) + H(2)+Ar) show that the emf of the cell is directly related to the difference in sulfur potentials established at the Ar + H(2) + H(2)S/electrode interfaces. The electrodes convert the sulfur potential gradient across the calcium fluoride electrolyte into an equivalent fluorine potential gradient. Response time of the probe varies from approximately 9 hr at 990 K to 2.5 hr at 1225 K. The conversion of calcium sulfide and/or calcium fluoride into calcium oxide is not a problem anticipated in commercial coal gasification systems. Suggestions are presented for improving the cell for such commercial applications.

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

1977-01-01

334

Electron Spin Resonance Spectroscopy via Relaxation of Solid-State Spin Probes at the Nanoscale  

E-print Network

Electron Spin Resonance (ESR) describes a suite of techniques for characterising electronic systems, with applications in physics, materials science, chemistry, and biology. However, the requirement for large electron spin ensembles in conventional ESR techniques limits their spatial resolution. Here we present a method for measuring the ESR spectrum of nanoscale electronic environments by measuring the relaxation time ($T_1$) of an optically addressed single-spin probe as it is systematically tuned into resonance with the target electronic system. As a proof of concept we extract the spectral distribution for the P1 electronic spin bath in diamond using an ensemble of nitrogen-vacancy centres, and demonstrate excellent agreement with theoretical expectations. As the response of each NV spin in this experiment is dominated by a single P1 spin at a mean distance of 2.7\\,nm, the extension of this all-optical technique to the single NV case will enable nanoscale ESR spectroscopy of atomic and molecular spin systems.

L. T. Hall; P. Kehayias; D. A. Simpson; A. Jarmola; A. Stacey; D. Budker; L. C. L. Hollenberg

2015-03-03

335

Solid state NMR spectroscopy study of molecular motion in cyclomaltoheptaose ( ?-cyclodextrin) crosslinked with epichlorohydrin 1 Paper presented at the IXth European Carbohydrate Symposium, Utrecht, The Netherlands, 6–11 July 1997; abstr. E-27, p. 465. 1  

Microsoft Academic Search

Dry and hydrated insoluble cyclomaltoheptaose (?-cyclodextrin, ?-CD) polymers have been investigated by solid state 13C NMR spectroscopy techniques such as cross polarization\\/magic angle spinning with dipolar decoupling (CP\\/MAS), magic angle spinning both with (DD-MAS) and without (MAS) dipolar decoupling and CP\\/MAS dipolar dephasing (dd-CP\\/MAS) to allow the assignment of the main 13C signals. In the solid state, the presence of

Grégorio Crini; Cesare Cosentino; Sabrina Bertini; Annamaria Naggi; Giangiacomo Torri; Carmen Vecchi; Ludovic Janus; Michel Morcellet

1998-01-01

336

Solid-state (185/187)Re NMR and GIPAW DFT study of perrhenates and Re2(CO)10: chemical shift anisotropy, NMR crystallography, and a metal-metal bond.  

PubMed

Advances in solid-state nuclear magnetic resonance (SSNMR) methods, such as dynamic nuclear polarization (DNP), intricate pulse sequences, and increased applied magnetic fields, allow for the study of systems which even very recently would be impractical. However, SSNMR methods using certain quadrupolar probe nuclei (i.e., I > 1/2), such as (185/187)Re remain far from fully developed due to the exceedingly strong interaction between the quadrupole moment of these nuclei and local electric field gradients (EFGs). We present a detailed high-field (B0 = 21.1 T) experimental SSNMR study on several perrhenates (KReO4, AgReO4, Ca(ReO4)2·2H2O), as well as ReO3 and Re2(CO)10. We propose solid ReO3 as a new rhenium SSNMR chemical shift standard due to its reproducible and sharp (185/187)Re NMR resonances. We show that for KReO4, previously poorly understood high-order quadrupole-induced effects (HOQIE) on the satellite transitions can be used to measure the EFG tensor asymmetry (i.e., ?Q) to nearly an order-of-magnitude greater precision than competing SSNMR and nuclear quadrupole resonance (NQR) approaches. Samples of AgReO4 and Ca(ReO4)2·2H2O enable us to comment on the effects of counter-ions and hydration upon Re(vii) chemical shifts. Calcium-43 and (185/187)Re NMR tensor parameters allow us to conclude that two proposed crystal structures for Ca(ReO4)2·2H2O, which would be considered as distinct, are in fact the same structure. Study of Re2(CO)10 provides insights into the effects of Re-Re bonding on the rhenium NMR tensor parameters and rhenium oxidation state on the Re chemical shift value. As overtone NQR experiments allowed us to precisely measure the (185/187)Re EFG tensor of Re2(CO)10, we were able to measure rhenium chemical shift anisotropy (CSA) for the first time in a powdered sample. Experimental observations are supported by gauge-including projector augmented-wave (GIPAW) density functional theory (DFT) calculations, with NMR tensor calculations also provided for NH4ReO4, NaReO4 and RbReO4. These calculations are able to reproduce many of the experimental trends in rhenium ?iso values and EFG tensor magnitudes. Using KReO4 as a prototypical perrhenate-containing system, we establish a correlation between the tetrahedral shear strain parameter (|?|) and the nuclear electric quadrupolar coupling constant (CQ), which enables the refinement of the structure of ND4ReO4. Shortcomings in traditional DFT approaches, even when including relativistic effects via the zeroth-order regular approximation (ZORA), for calculating rhenium NMR tensor parameters are identified for Re2(CO)10. PMID:25790263

Widdifield, Cory M; Perras, Frédéric A; Bryce, David L

2015-04-01

337

Local environments and dynamics of hydrogen atoms in protonated forms of ion-exchangeable layered perovskites estimated by solid-state {sup 1}H NMR  

SciTech Connect

The local environments and dynamics of hydrogen atoms in five samples of protonated forms of ion-exchangeable layered perovskites, Dion-Jacobson-type H[LaNb{sub 2}O{sub 7}] and H[LaTa{sub 2}O{sub 7}], Ruddlesden-Popper-type H{sub 2}[SrTa{sub 2}O{sub 7}] and H{sub 2}[La{sub 2}Ti{sub 3}O{sub 10}], and H{sub 1.8}[(Sr{sub 0.8}Bi{sub 0.2})Ta{sub 2}O{sub 7}] derived from an Aurivillius phase, Bi{sub 2}Sr{sub 2}Ta{sub 2}O{sub 9}, have been investigated by solid-state {sup 1}H nuclear magnetic resonance spectroscopy (NMR). Solid-state {sup 1}H NMR with a magic-angle spinning technique conducted at room temperature reveals that the mean electron densities around the {sup 1}H nuclei in these protonated forms are relatively low, and that they decrease in the following order: H{sub 1.8}[(Sr{sub 0.8}Bi{sub 0.2})Ta{sub 2}O{sub 7}]>H[LaNb{sub 2}O{sub 7}]>H{sub 2}[SrTa{sub 2}O{sub 7}]>H[LaTa{sub 2}O{sub 7}]>H{sub =} 2[La{sub 2}Ti{sub 3}O{sub 10}]. The temperature-dependent solid-state {sup 1}H broad-line NMR spectra measured at 140-400 K reveal a decrease in the signal width for all of these five samples upon heating due to motional narrowing. The NMR spectra of H[LaNb{sub 2}O{sub 7}] and H[LaTa{sub 2}O{sub 7}] are different from the other three protonated forms due to the weaker dipole-dipole interactions at low temperatures and lower mobility of the hydrogen atoms at high temperatures. - Graphical abstract: Solid-state {sup 1}H MAS NMR spectra of protonated forms of ion-exchangeable layered perovskites: (a) H[LaNb{sub 2}O{sub 7}]; (b) H[LaTa{sub 2}O{sub 7}]; (c) H{sub 1.8}[(Sr{sub 0.8}Bi{sub 0.2})Ta{sub 2}O{sub 7}]; (d) H{sub 2}[SrTa{sub 2}O{sub 7}]; and (e) H{sub 2}[La{sub 2}Ti{sub 3}O{sub 10}]. The spinning side bands are marked with asterisks.

Tani, Shinsuke [Department of Applied Chemistry, School of Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555 (Japan); Komori, Yoshihiko [Research Institute of Instrumentation Frontier, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan); Hayashi, Shigenobu [Research Institute of Instrumentation Frontier, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan); Sugahara, Yoshiyuki [Department of Applied Chemistry, School of Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555 (Japan)]. E-mail: ys6546@waseda.jp

2006-11-15

338

YPdSn and YPd{sub 2}Sn: Structure, {sup 89}Y solid state NMR and {sup 119}Sn Moessbauer spectroscopy  

SciTech Connect

The stannides YPdSn and YPd{sub 2}Sn were synthesized by high-frequency melting of the elements in sealed tantalum tubes. Both structures were refined on the basis of single crystal X-ray diffractometer data: TiNiSi type, Pnma, a=715.4(1), b=458.8(1), c=789.1(1) pm, wR2=0.0461, 510 F{sup 2} values, 20 variables for YPdSn and MnCu{sub 2}Al type, Fm3 Macron m, a=671.44(8), wR2=0.0740, 55 F{sup 2} values, 5 parameters for YPd{sub 2}Sn. The yttrium atoms in the new stannide YPdSn are coordinated by two tilted Pd{sub 3}Sn{sub 3} hexagons (ordered AlB{sub 2} superstructure). In the Heusler phase YPd{sub 2}Sn each yttrium atom has octahedral tin coordination and additionally eight palladium neighbors. The cubic site symmetry of yttrium is reflected in the {sup 119}Sn Moessbauer spectrum which shows no quadrupole splitting. In contrast, YPdSn shows a single signal at {delta}=1.82(1) mm/s subjected to quadrupole splitting of {Delta}E{sub Q}=0.93(1) mm/s. Both compounds have been characterized by high-resolution {sup 89}Y solid state NMR spectroscopy, which indicates the presence of strong Knight shifts. The spectrum of YPd{sub 2}Sn is characterized by an unusually large linewidth, suggesting the presence of a Knight shift distribution reflecting local disordering effects. The range of {sup 89}Y Knight shifts of several binary and ternary intermetallic yttrium compounds is briefly discussed. - Graphical abstract: YPdSn and YPd{sub 2}Sn: Structure, {sup 89}Y solid state NMR and {sup 119}Sn Moessbauer spectroscopy. Highlights: Black-Right-Pointing-Pointer Synthesis and structure of ternary stannides YPdSn and YPd{sub 2}Sn. Black-Right-Pointing-Pointer {sup 119}Sn Moessbauer spectroscopic investigation of YPdSn and YPd{sub 2}Sn. Black-Right-Pointing-Pointer {sup 89}Y solid state NMR of intermetallics.

Hoeting, Christoph [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster, Corrensstrasse 30, D-48149 Muenster (Germany); Eckert, Hellmut [Institut fuer Physikalische Chemie, Universitaet Muenster, Corrensstrasse 30, D-48149 Muenster (Germany); Langer, Thorsten; Schellenberg, Inga [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster, Corrensstrasse 30, D-48149 Muenster (Germany); Poettgen, Rainer, E-mail: pottgen@uni-muenster.de [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster, Corrensstrasse 30, D-48149 Muenster (Germany)

2012-06-15

339

Impact of oxidized phospholipids on the structural and dynamic organization of phospholipid membranes: a combined DSC and solid state NMR study.  

PubMed

Membranes undergo severe changes under oxidative stress conditions due to the creation of oxidized phospholipid (OxPL) species, which possess molecular properties quite different from their parental lipid components. These OxPLs play crucial roles in various pathological disorders and their occurrence is involved in the onset of intrinsic apoptosis, a fundamental pathway in programmed mammalian cell death. However, the molecular mechanisms by which these lipids can exert their apoptotic action via their host membranes (e.g., altering membrane protein function) are poorly understood. Therefore, we studied the impact of OxPLs on the organization and biophysical properties of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) based lipid membranes by differential scanning calorimetry (DSC) and solid state nuclear magnetic resonance (NMR) spectroscopy. Incorporation of defined OxPLs with either a carboxyl group (1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine (PazePC)) or aldehyde (1-palmitoyl-(9'oxononanoyl)-sn-glycero-3-phosphocholine (PoxnoPC)) at their truncated sn-2-chain ends enabled us to reveal OxPL species-dependent differences. The calorimetric studies revealed significant effects of OxPLs on the thermotropic phase behavior of DMPC bilayers, especially at elevated levels where PazePC induced more pronounced effects than PoxnoPC. Temperature-dependent changes in the solid state 31P NMR spectra, which provided information of the lipid headgroup region in these mixed membrane systems, reflected this complex phase behavior. In the temperature region between 293 K (onset of the Lalpha-phase) and 298 K, two overlapping NMR spectra were visible which reflect the co-existence of two liquid-crystalline lamellar phases with presumably one reflecting OxPL-poor domains and the other OxPL-rich domains. Deconvolution of the DSC profiles also revealed these two partially overlapping thermal events. In addition, a third thermal, non-NMR-visible, event occurred at low temperatures, which can most likely be associated to a solid-phase mixing/demixing process of the OxPL-containing membranes. The observed phase transitions were moved to higher temperatures in the presence of heavy water due its condensing effect, where additional wideline 2H-NMR studies revealed a complex hydration pattern in the presence of OxPLs. PMID:23805755

Wallgren, Marcus; Beranova, Lenka; Pham, Quoc Dat; Linh, Khanh; Lidman, Martin; Procek, Jan; Cyprych, Konrad; Kinnunen, Paavo K J; Hof, Martin; Gröbner, Gerhard

2013-01-01

340

Molecular level investigations of phosphate sorption on corundum (?-Al2O3) by 31P solid state NMR, ATR-FTIR and quantum chemical calculation  

NASA Astrophysics Data System (ADS)

Phosphate sorption at the corundum (?-Al2O3)/water interface was investigated as a function of phosphate concentration (0.1-1 mM) and pH (3-11) by 31P solid state NMR spectroscopy, ATR-FTIR, and quantum chemical calculation. The 31P NMR spectra indicate that under these experimental conditions phosphate adsorbs onto corundum mainly as inner-sphere complexes that yield a peak at ?P = -2.8 ppm with full width at half maximum (FWHM) of 9.2 ppm, with a small amount aluminum phosphate surface precipitates as suggested by an NMR signal observed from ?P = -12 to -20 ppm. We employed 31P{27Al} rotational echo adiabatic passage double resonance (REAPDOR) to further analyze the phosphate adsorption samples prepared at pH 5 and 9 in order to determine the phosphate/Al coordination. To aid interpretation of the NMR data, a series of bidentate and monodentate structural models of phosphate adsorbed on corundum (0 0 1) and (0 1 2) surfaces were calculated using density function theory (DFT). By comparing the experimental REAPDOR curves and those simulated from these models, we can assign the dominant peaks to bidentate binuclear surface complexes. Formation of bidentate binuclear surface complexes is supported by the ATR/FTIR spectra combined with DFT calculation, which further suggests a mixture of non-protonated bidentate and mono-protonated bidentate surface complexes on the corundum surface at pH 5. At pH 9, both NMR and ATR/FTIR indicate the formation of bidentate surface complexes on corundum surface.

Li, Wei; Pierre-Louis, Andro-Marc; Kwon, Kideok D.; Kubicki, James D.; Strongin, Daniel R.; Phillips, Brian L.

2013-04-01

341

Solid state 13C NMR analysis of shales and coals from Laramide Basins. Final report, March 1, 1995--March 31, 1996  

SciTech Connect

This Western Research Institute (WRI) jointly sponsored research (JSR) project augmented and complemented research conducted by the University of Wyoming Institute For Energy Research for the Gas Research Institute. The project, {open_quotes}A New Innovative Exploitation Strategy for Gas Accumulations Within Pressure Compartments,{close_quotes} was a continuation of a project funded by the GRI Pressure Compartmentalization Program that began in 1990. That project, {open_quotes}Analysis of Pressure Chambers and Seals in the Powder River Basin, Wyoming and Montana,{close_quotes} characterized a new class of hydrocarbon traps, the discovery of which can provide an impetus to revitalize the domestic petroleum industry. In support of the UW Institute For Energy Research`s program on pressure compartmentalization, solid-state {sup 13}C NMR measurements were made on sets of shales and coals from different Laramide basins in North America. NMR measurements were made on samples taken from different formations and depths of burial in the Alberta, Bighorn, Denver, San Juan, Washakie, and Wind River basins. The carbon aromaticity determined by NMR was shown to increase with depth of burial and increased maturation. In general, the NMR data were in agreement with other maturational indicators, such as vitrinite reflectance, illite/smectite ratio, and production indices. NMR measurements were also obtained on residues from hydrous pyrolysis experiments on Almond and Lance Formation coals from the Washakie Basin. These data were used in conjunction with mass and elemental balance data to obtain information about the extent of carbon aromatization that occurs during artificial maturation. The data indicated that 41 and 50% of the original aliphatic carbon in the Almond and Lance coals, respectively, aromatized during hydrous pyrolysis.

Miknis, F.P.; Jiao, Z.S.; Zhao, Hanqing; Surdam, R.C.

1998-12-31

342

?-Sheet Nanocrystalline Domains Formed from Phosphorylated Serine-Rich Motifs in Caddisfly Larval Silk: A Solid State NMR and XRD Study  

PubMed Central

Adhesive silks spun by aquatic caddisfly (order Trichoptera) larvae are used to build both intricate protective shelters and food harvesting nets underwater. In this study, we use 13C and 31P solid-state Nuclear Magnetic Resonance (NMR) and Wide Angle X-ray Diffraction (WAXD) as tools to elucidate molecular protein structure of caddisfly larval silk from the species Hesperophylax consimilis. Caddisfly larval silk is a fibroin protein based biopolymer containing mostly repetitive amino acid motifs. NMR and X-ray results provide strong supporting evidence for a structural model in which phosphorylated serine repeats (pSX)4 complex with divalent cations Ca2+ and Mg2+ to form rigid nanocrystalline ?-sheet structures in caddisfly silk. 13C NMR data suggests that both phosphorylated serine and neighboring valine residues exist in a ?-sheet secondary structure conformation while glycine and leucine residues common in GGX repeats likely reside in random coil conformations. Additionally, 31P chemical shift anisotropy (CSA) analysis indicates that the phosphates on phosphoserine residues are doubly ionized, and are charge-stabilized by divalent cations. Positively charged arginine side chains also likely play a role in charge stabilization. Finally, WAXD results finds that the silk is at least 7–8% crystalline, with ?-sheet inter-plane spacings of 3.7 and 4.5 Å. PMID:23452243

Addison, J. Bennett; Ashton, Nicholas N.; Weber, Warner S.; Stewart, Russell J.; Holland, Gregory P.; Yarger, Jeffery L.

2013-01-01

343

Perturbation of nuclear spin polarizations in solid state NMR of nitroxide-doped samples by magic-angle spinning without microwaves  

SciTech Connect

We report solid state {sup 13}C and {sup 1}H nuclear magnetic resonance (NMR) experiments with magic-angle spinning (MAS) on frozen solutions containing nitroxide-based paramagnetic dopants that indicate significant perturbations of nuclear spin polarizations without microwave irradiation. At temperatures near 25 K, {sup 1}H and cross-polarized {sup 13}C NMR signals from {sup 15}N,{sup 13}C-labeled L-alanine in trinitroxide-doped glycerol/water are reduced by factors as large as six compared to signals from samples without nitroxide doping. Without MAS or at temperatures near 100 K, differences between signals with and without nitroxide doping are much smaller. We attribute most of the reduction of NMR signals under MAS near 25 K to nuclear spin depolarization through the cross-effect dynamic nuclear polarization mechanism, in which three-spin flips drive nuclear polarizations toward equilibrium with spin polarization differences between electron pairs. When T{sub 1e} is sufficiently long relative to the MAS rotation period, the distribution of electron spin polarization across the nitroxide electron paramagnetic resonance lineshape can be very different from the corresponding distribution in a static sample at thermal equilibrium, leading to the observed effects. We describe three-spin and 3000-spin calculations that qualitatively reproduce the experimental observations.

Thurber, Kent R., E-mail: thurberk@niddk.nih.gov; Tycko, Robert [Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520 (United States)] [Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520 (United States)

2014-05-14

344

Solid-state sup 95 Mo NMR study of (aryldiazenido)- and (organohydrazido)polyoxomolybdates. Investigation of model compounds of catalytic molybdenum environments  

SciTech Connect

The {sup 95}Mo static powder and magic angle spinning NMR spectra of the central {plus minus} 1/2 transition of a number of (aryldiazenido)polyoxomolybdates, (organohydrazido)polyoxomolybdates, and unsubstituted polyoxomolybdates were obtained. The spectra clearly demonstrated the existence of octahedral and tetrahedral sites within these compounds by the contrast between the respective line widths and the dependence under MAS conditions of the resonances from these sites. Variation of ligand coordination was also seen to yield a visible chemical shift to the octahedral molybdenum sites in selected complexes. An interactive graphics curve-fitting program was used to estimate the quadrupolar coupling constants, asymmetry parameters of the electric field gradients, the three principal elements of the shielding tensor, and the Euler angles relating the quadrupole and chemical shielding principal axis systems for the molybdenum sites from the static powder spectra. Assignments of the line shape components was made to the different molybdenum sites present in these species. The method of assignment, based on degree of distortion at the site, was vindicated by MO calculations carried out on a simple (MoO{sub 6}){sup 6{minus}} model species. The effectiveness of the {sup 95}Mo NMR technique to obtain these data from Mo(VI) compounds was thus demonstrated and has laid a foundation from which future solid-state {sup 95}Mo NMR studies of biological and catalytic molybdenum systems can benefit by comparison of the results obtained with those obtained for these model compounds.

Edwards, J.C.; Ellis, P.D. (Univ. of South Carolina, Columbia (USA)); Zubieta, J.; Shaikh, S.N.; Chen, Quin; Bank, S. (State Univ. of New York, Albany (USA))

1990-09-05

345

High-resolution structure of the Shigella type-III secretion needle by solid-state NMR and cryo-electron microscopy.  

PubMed

We introduce a general hybrid approach for determining the structures of supramolecular assemblies. Cryo-electron microscopy (cryo-EM) data define the overall envelope of the assembly and rigid-body orientation of the subunits while solid-state nuclear magnetic resonance (ssNMR) chemical shifts and distance constraints define the local secondary structure, protein fold and inter-subunit interactions. Finally, Rosetta structure calculations provide a general framework to integrate the different sources of structural information. Combining a 7.7-Å cryo-EM density map and 996 ssNMR distance constraints, the structure of the type-III secretion system needle of Shigella flexneri is determined to a precision of 0.4?Å. The calculated structures are cross-validated using an independent data set of 691 ssNMR constraints and scanning transmission electron microscopy measurements. The hybrid model resolves the conformation of the non-conserved N terminus, which occupies a protrusion in the cryo-EM density, and reveals conserved pore residues forming a continuous pattern of electrostatic interactions, thereby suggesting a mechanism for effector protein translocation. PMID:25264107

Demers, Jean-Philippe; Habenstein, Birgit; Loquet, Antoine; Kumar Vasa, Suresh; Giller, Karin; Becker, Stefan; Baker, David; Lange, Adam; Sgourakis, Nikolaos G

2014-01-01

346

Sensitivity enhancement in natural-abundance solid-state 33S MAS NMR spectroscopy employing adiabatic inversion pulses to the satellite transitions  

NASA Astrophysics Data System (ADS)

The WURST (wideband uniform rate smooth truncation) and hyperbolic secant (HS) pulse elements have each been employed as pairs of inversion pulses to induce population transfer (PT) between the four energy levels in natural abundance solid-state 33S (spin I = 3/2) MAS NMR, thereby leading to a significant gain in intensity for the central transition (CT). The pair of inversion pulses are applied to the satellite transitions for a series of inorganic sulfates, the sulfate ions in the two cementitious materials ettringite and thaumasite, and the two tetrathiometallates (NH 4) 2WS 4 and (NH 4) 2MoS 4. These materials all exhibit 33S quadrupole coupling constants ( CQ) in the range 0.1-1.0 MHz, with precise CQ values being determined from analysis of the PT enhanced 33S MAS NMR spectra. The enhancement factors for the WURST and HS elements are quite similar and are all in the range 1.74-2.25 for the studied samples, in excellent agreement with earlier reports on HS enhancement factors (1.6-2.4) observed for other spin I = 3/2 nuclei with similar CQ values (0.3-1.2 MHz). Thus, a time saving in instrument time by a factor up to five has been achieved in natural abundance 33S MAS NMR, a time saving which is extremely welcome for this important low-? nucleus.

Hansen, Michael Ryan; Brorson, Michael; Bildsøe, Henrik; Skibsted, Jørgen; Jakobsen, Hans J.

2008-02-01

347

Sensitivity enhancement in natural-abundance solid-state 33S MAS NMR spectroscopy employing adiabatic inversion pulses to the satellite transitions.  

PubMed

The WURST (wideband uniform rate smooth truncation) and hyperbolic secant (HS) pulse elements have each been employed as pairs of inversion pulses to induce population transfer (PT) between the four energy levels in natural abundance solid-state (33)S (spin I=3/2) MAS NMR, thereby leading to a significant gain in intensity for the central transition (CT). The pair of inversion pulses are applied to the satellite transitions for a series of inorganic sulfates, the sulfate ions in the two cementitious materials ettringite and thaumasite, and the two tetrathiometallates (NH(4))(2)WS(4) and (NH(4))(2)MoS(4). These materials all exhibit (33)S quadrupole coupling constants (C(Q)) in the range 0.1-1.0 MHz, with precise C(Q) values being determined from analysis of the PT enhanced (33)S MAS NMR spectra. The enhancement factors for the WURST and HS elements are quite similar and are all in the range 1.74-2.25 for the studied samples, in excellent agreement with earlier reports on HS enhancement factors (1.6-2.4) observed for other spin I=3/2 nuclei with similar C(Q) values (0.3-1.2 MHz). Thus, a time saving in instrument time by a factor up to five has been achieved in natural abundance (33)S MAS NMR, a time saving which is extremely welcome for this important low-gamma nucleus. PMID:18082436

Hansen, Michael Ryan; Brorson, Michael; Bildsøe, Henrik; Skibsted, Jørgen; Jakobsen, Hans J

2008-02-01

348

Interaction between histidine and Zn(II) metal ions over a wide pH as revealed by solid-state NMR spectroscopy and DFT calculations.  

PubMed

The interactions between histidine and metal species play essential roles in a wide range of important biological processes including enzymes catalysis and signal transduction. In this work, solid-state NMR techniques were employed to determine the interaction between histidine and Zn(II) from pH 3.5 to 14. 2D homo- and heteronuclear correlation NMR experiments were utilized to extract the (1)H, (13)C, and (15)N chemical shifts in various histidine-Zn(II) binding complexes. Several histidine-Zn(II) binding models were proposed on the basis of experimental results as well as DFT theoretical calculations. No direct interaction could be found between biprotonated histidine and Zn(II) at acidic pH. At pH 7.5, one zinc ion could be hexa-coordinated with two histidine molecules on C', N? and deprotonated N?1 sites. As the pH increases to 11-14, both of the N?1 and N?2 sites could be deprotonated as acceptors to be bound to either Zn(II) or water. All of these findings give a comprehensive set of benchmark values for NMR parameters and structural geometries in variable histidine-Zn(II) binding complexes over a wide pH range and might provide insights into the structure-property relationship of histidine-metal complexes in biological metalloproteins. PMID:23841698

Zhou, Lei; Li, Shenhui; Su, Yongchao; Yi, Xianfeng; Zheng, Anmin; Deng, Feng

2013-08-01

349

High-resolution structure of the Shigella type-III secretion needle by solid-state NMR and cryo-electron microscopy  

NASA Astrophysics Data System (ADS)

We introduce a general hybrid approach for determining the structures of supramolecular assemblies. Cryo-electron microscopy (cryo-EM) data define the overall envelope of the assembly and rigid-body orientation of the subunits while solid-state nuclear magnetic resonance (ssNMR) chemical shifts and distance constraints define the local secondary structure, protein fold and inter-subunit interactions. Finally, Rosetta structure calculations provide a general framework to integrate the different sources of structural information. Combining a 7.7-Å cryo-EM density map and 996 ssNMR distance constraints, the structure of the type-III secretion system needle of Shigella flexneri is determined to a precision of 0.4?Å. The calculated structures are cross-validated using an independent data set of 691 ssNMR constraints and scanning transmission electron microscopy measurements. The hybrid model resolves the conformation of the non-conserved N terminus, which occupies a protrusion in the cryo-EM density, and reveals conserved pore residues forming a continuous pattern of electrostatic interactions, thereby suggesting a mechanism for effector protein translocation.

Demers, Jean-Philippe; Habenstein, Birgit; Loquet, Antoine; Kumar Vasa, Suresh; Giller, Karin; Becker, Stefan; Baker, David; Lange, Adam; Sgourakis, Nikolaos G.

2014-09-01

350

Perturbation of nuclear spin polarizations in solid state NMR of nitroxide-doped samples by magic-angle spinning without microwaves.  

PubMed

We report solid state (13)C and (1)H nuclear magnetic resonance (NMR) experiments with magic-angle spinning (MAS) on frozen solutions containing nitroxide-based paramagnetic dopants that indicate significant perturbations of nuclear spin polarizations without microwave irradiation. At temperatures near 25 K, (1)H and cross-polarized (13)C NMR signals from (15)N,(13)C-labeled L-alanine in trinitroxide-doped glycerol/water are reduced by factors as large as six compared to signals from samples without nitroxide doping. Without MAS or at temperatures near 100 K, differences between signals with and without nitroxide doping are much smaller. We attribute most of the reduction of NMR signals under MAS near 25 K to nuclear spin depolarization through the cross-effect dynamic nuclear polarization mechanism, in which three-spin flips drive nuclear polarizations toward equilibrium with spin polarization differences between electron pairs. When T1e is sufficiently long relative to the MAS rotation period, the distribution of electron spin polarization across the nitroxide electron paramagnetic resonance lineshape can be very different from the corresponding distribution in a static sample at thermal equilibrium, leading to the observed effects. We describe three-spin and 3000-spin calculations that qualitatively reproduce the experimental observations. PMID:24832263

Thurber, Kent R; Tycko, Robert

2014-05-14

351

The use of 6Li{7Li}-REDOR NMR spectroscopy to compare the ionic conductivities of solid-state lithium ion electrolytes.  

PubMed

Garnet-like solid-state electrolyte materials for lithium ion batteries are promising replacements for the currently-used liquid electrolytes. This work compares the temperature dependent Li(+) ion hopping rate in Li6BaLa2M2O12 (M = Ta, Nb) using solid-state (6)Li{(7)Li}-REDOR NMR. The slope of the (6)Li{(7)Li}-REDOR curve is highly temperature dependent in these two phases, and a comparison of the changes of the REDOR slopes as a function of temperature has been used to evaluate the Li(+) ion dynamics. Our results indicate that the Nb phase has a higher overall ionic conductivity in the range of 247 K to 350 K, as well as a higher activation energy for lithium ion hopping than the Ta counterpart. For appropriate relative timescales of the dipolar couplings and ion transport processes, this is shown to be a facile method to compare ion dynamics among similar structures. PMID:24363013

Spencer, T L; Plagos, N W; Brouwer, D H; Goward, G R

2014-02-14

352

Proton chemical shift anisotropy measurements of hydrogen-bonded functional groups by fast magic-angle spinning solid-state NMR  

E-print Network

between the principal elements of 15 N, 13 C and 31 P chemical shift tensors and the strength of hydrogenProton chemical shift anisotropy measurements of hydrogen-bonded functional groups by fast magic-state NMR spectroscopy for probing 1 H chemical shift anisotropy of hydrogen-bonded species has been

353

NMR Crystallography of Enzyme Active Sites: Probing Chemically-Detailed, Three-Dimensional Structure in Tryptophan Synthase  

PubMed Central

Conspectus NMR crystallography – the synergistic combination of X-ray diffraction, solid-state NMR spectroscopy, and computational chemistry – offers unprecedented insight into three-dimensional, chemically-detailed structure. From its initial role in refining diffraction data of organic and inorganic solids, NMR crystallography is now being developed for application to active sites in biomolecules, where it reveals chemically-rich detail concerning the interactions between enzyme site residues and the reacting substrate that is not achievable when X-ray, NMR, or computational methodologies are applied in isolation. For example, typical X-ray crystal structures (1.5 to 2.5 Å resolution) of enzyme-bound intermediates identify possible hydrogen-bonding interactions between site residues and substrate, but do not directly identify the protonation state of either. Solid-state NMR can provide chemical shifts for selected atoms of enzyme-substrate complexes, but without a larger structural framework in which to interpret them, only empirical correlations with local chemical structure are possible. Ab initio calculations and molecular mechanics can build models for enzymatic processes, but rely on chemical details that must be specified. Together, however, X-ray diffraction, solid-state NMR spectroscopy, and computational chemistry can provide consistent and testable models for structure and function of enzyme active sites: X-ray crystallography provides a coarse framework upon which models of the active site can be developed using computational chemistry; these models can be distinguished by comparison of their calculated NMR chemical shifts with the results of solid-state NMR spectroscopy experiments. Conceptually, each technique is a puzzle piece offering a generous view of the big picture. Only when correctly pieced together, however, can they reveal the big picture at highest resolution. In this Account, we detail our first steps in the development of NMR crystallography for application to enzyme catalysis. We begin with a brief introduction to NMR crystallography and then define the process that we have employed to probe the active site in the ?-subunit of tryptophan synthase with unprecedented atomic-level resolution. This approach has resulted in a novel structural hypothesis for the protonation state of the quinonoid intermediate in tryptophan synthase and its surprising role in directing the next step in the catalysis of L-Trp formation. PMID:23537227

Dunn, Michael F.

2013-01-01

354

Resolution and measurement of heteronuclear dipolar couplings of a noncrystalline protein immobilized in a biological supramolecular assembly by proton-detected MAS solid-state NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Two-dimensional 15N chemical shift/1H chemical shift and three-dimensional 1H-15N dipolar coupling/15N chemical shift/1H chemical shift MAS solid-state NMR correlation spectra of the filamentous bacteriophage Pf1 major coat protein show single-site resolution in noncrystalline, intact-phage preparations. The high sensitivity and resolution result from 1H detection at 600 MHz under 50 kHz magic angle spinning using ?0.5 mg of perdeuterated and uniformly 15N-labeled protein in which the exchangeable amide sites are partially or completely back-exchanged (reprotonated). Notably, the heteronuclear 1H-15N dipolar coupling frequency dimension is shown to select among 15N resonances, which will be useful in structural studies of larger proteins where the resonances exhibit a high degree of overlap in multidimensional chemical shift correlation spectra.

Park, Sang Ho; Yang, Chen; Opella, Stanley J.; Mueller, Leonard J.

2013-12-01

355

Enhanced sensitivity in high-resolution 1H solid-state NMR spectroscopy with DUMBO dipolar decoupling under ultra-fast MAS  

NASA Astrophysics Data System (ADS)

The solid-state NMR 1H homonuclear decoupling sequences in the DUMBO family are shown to be effective at ultra-fast MAS rates of up to 65 kHz. The sequences are applied to model compounds glycine and [2- 13C]- L-alanine as well as the dipeptide ?- L-Asp- L-Ala in windowed and continuous phase-modulated versions. They are shown to achieve especially impressive resolution when implemented in a 2D constant-time experiment. At 65 kHz MAS, 1H resolution using homonuclear decoupling is similar to that obtained at lower MAS rates, but peak intensity, and therefore spectral sensitivity, is improved by a factor of 5 over homonuclear-decoupled spectra at 10 kHz MAS.

Salager, Elodie; Stein, Robin S.; Steuernagel, Stefan; Lesage, Anne; Elena, Bénédicte; Emsley, Lyndon

2009-02-01

356

The investigation of membrane binding by amphibian peptide agonists of CCK2R using (31)P and (2)H solid-state NMR.  

PubMed

It has been proposed that some neuropeptides may be anchored to the cell membranes prior to attaching to the adjacent active sites of transmembrane receptors. The three amphibian skin neuropeptides signiferin 1 [RLCIPYIIPC(OH)] (smooth muscle active and immunomodulator), riparin 1.1 [[RLCIPVIFPC(OH)] (immunomodulator) and rothein 1 [SVSNIPESIGF(OH)] (immunomodulator) act via CCK2 transmembrane receptors. A combination of (31)P and (2)H solid state NMR studies of each of these three peptides in eukaryotic phospholipid models at 25°C shows that rothein 1 does not interact with the membrane at all. In contrast, both of the cyclic disulfides signiferin 1 and riparin 1.1 interact with phospholipid head groups and partially penetrate into the upper leaflet of the model bilayer, but to different extents. These interactions are not sufficiently effective to cause disruption of the lipid bilayer since the peptides are not antimicrobial, anticancer, antifungal nor active against enveloped viruses. PMID:24582625

Sherman, Patrick J; Separovic, Frances; Bowie, John H

2014-05-01

357

{sup 29}Si solid state NMR investigation of pozzolanic reaction occurring in lime-treated Ca-bentonite  

SciTech Connect

Lime is widely used as additive to improve the mechanical properties of natural soil used in earthworks. However, the physico-chemical mechanisms involved are yet not well understood. In order to develop and optimize this treatment method, a better understanding of the interaction between lime and the minerals of the soils, in particular clay minerals, is required. In this study, Ca-bentonite was treated with 2, 5 and 10 wt.% of lime during 1 to 98 days. Modifications in the Si local environment were then monitored by solid state nuclear magnetic resonance to investigate the pozzolanic reaction. All the soil mineral phases contribute to the release of Si and to the pozzolanic reaction, with a rapid and total consumption of Si-polymorph and an exacerbated dissolution of montmorillonite. Mechanism of C-S-H formation, function of the Ca content in the system, was found to match the sorosilicate-tobermorite model described in cement systems.

Pomakhina, Elena [Institut des Materiaux Jean Rouxel (IMN), Universite de Nantes, CNRS, 2 rue de la Houssiniere, BP 32229, 44322 Nantes Cedex 3 (France); Deneele, Dimitri, E-mail: dimitri.deneele@ifsttar.fr [Institut des Materiaux Jean Rouxel (IMN), Universite de Nantes, CNRS, 2 rue de la Houssiniere, BP 32229, 44322 Nantes Cedex 3 (France); UNAM, IFSTTAR, Institut Francais des Sciences et des Technologies des Transports, de l'Amenagement et des Reseaux, BP 4129, route de Bouaye, 44332 Bouguenais (France); Gaillot, Anne-Claire; Paris, Michael; Ouvrard, Guy [Institut des Materiaux Jean Rouxel (IMN), Universite de Nantes, CNRS, 2 rue de la Houssiniere, BP 32229, 44322 Nantes Cedex 3 (France)

2012-04-15

358

Solid-state 13C NMR studies of a large fossil gymnosperm from the Yallourn Open Cut, Latrobe Valley, Australia  

USGS Publications Warehouse

A series of samples taken from the cross section of a 3-m-diameter fossilized gymnospermous log (Araucariaceae) in the Yallourn Seam of the Australian brown coals was examined by solid state 13C nuclear magnetic resonance to delineate chemical changes related to the combined processes of peatification and coalification. The results show that cellulosic materials were degraded and lost on the periphery of the log, however, the degree of such degradation in the central core is substantially less. The lignin is uniformly altered by coalification reactions to a macromolecular substance displaying decreased aryl ether linkages but significantly greater amounts of carbon linkages compared to modern lignin. Changes in the methoxyl carbon contents of lignin in cross section reveal demethylation reactions, but these do not appear to be related to degree of carbon linking. Both the degredation of cellulosic materials and demethylation of lignin appear to be early diagenetic processes occurring during peatification independently of the coalification reactions. ?? 1989.

Bates, A.L.; Hatcher, P.G.

1989-01-01

359

Ultrafast MAS solid-state NMR permits extensive 13C and 1H detection in paramagnetic metalloproteins.  

PubMed

We show here that by combining tailored approaches based on ultrafast (60 kHz) MAS on the Co(II)-replaced catalytic domain of matrix metalloproteinase 12 (CoMMP-12) we can observe and assign, in a highly paramagnetic protein in the solid state, (13)C and even (1)H resonances from the residues coordinating the metal center. In addition, by exploiting the enhanced relaxation caused by the paramagnetic center, and the low power irradiation enabled by the fast MAS, this can be achieved in remarkably short times and at very high field (21.2 T), with only less than 1 mg of sample. Furthermore, using the known crystal structure of the compound, we are able to distinguish and measure pseudocontact (PCS) contributions to the shifts up to the coordinating ligands and to unveil structural information. PMID:20356036

Bertini, Ivano; Emsley, Lyndon; Lelli, Moreno; Luchinat, Claudio; Mao, Jiafei; Pintacuda, Guido

2010-04-28

360

Diazole-based powdered cocrystal featuring a helical hydrogen-bonded network: Structure determination from PXRD, solid-state NMR and computer modeling.  

PubMed

We present the structure of a new equimolar 1:1 cocrystal formed by 3,5-dimethyl-1H-pyrazole (dmpz) and 4,5-dimethyl-1H-imidazole (dmim), determined by means of powder X-ray diffraction data combined with solid-state NMR that provided insight into topological details of hydrogen bonding connectivities and weak interactions such as CH···? contacts. The use of various 1D/2D (13)C, (15)N and (1)H high-resolution solid-state NMR techniques provided structural insight on local length scales revealing internuclear proximities and relative orientations between the dmim and dmpz molecular building blocks of the studied cocrystal. Molecular modeling and DFT calculations were also employed to generate meaningful structures. DFT refinement was able to decrease the figure of merit R(F(2)) from ~11% (PXRD only) to 5.4%. An attempt was made to rationalize the role of NH···N and CH···? contacts in stabilizing the reported cocrystal. For this purpose four imidazole derivatives with distinct placement of methyl substituents were reacted with dmpz to understand the effect of methylation in blocking or enabling certain intermolecular contacts. Only one imidazole derivative (dmim) was able to incorporate into the dmpz trimeric motif thus resulting in a cocrystal, which contains both hydrophobic (methyl groups) and hydrophilic components that self-assemble to form an atypical 1D network of helicoidal hydrogen bonded pattern, featuring structural similarities with alpha-helix arrangements in proteins. The 1:1 dmpz···dmim compound I is the first example of a cocrystal formed by two different azoles. PMID:25604487

Sardo, Mariana; Santos, Sérgio M; Babaryk, Artem A; López, Concepción; Alkorta, Ibon; Elguero, José; Claramunt, Rosa M; Mafra, Luís

2015-02-01

361

Proton-detected 2D radio frequency driven recoupling solid-state NMR studies on micelle-associated cytochrome-b(5).  

PubMed

Solid-state NMR spectroscopy is increasingly used in the high-resolution structural studies of membrane-associated proteins and peptides. Most such studies necessitate isotopically labeled ((13)C, (15)N and (2)H) proteins/peptides, which is a limiting factor for some of the exciting membrane-bound proteins and aggregating peptides. In this study, we report the use of a proton-based slow magic angle spinning (MAS) solid-state NMR experiment that exploits the unaveraged (1)H-(1)H dipolar couplings from a membrane-bound protein. We have shown that the difference in the buildup rates of cross-peak intensities against the mixing time - obtained from 2D (1)H-(1)H radio frequency-driven recoupling (RFDR) and nuclear Overhauser effect spectroscopy (NOESY) experiments on a 16.7-kDa micelle-associated full-length rabbit cytochrome-b5 (cytb5) - can provide insights into protein dynamics and could be useful to measure (1)H-(1)H dipolar couplings. The experimental buildup curves compare well with theoretical simulations and are used to extract relaxation parameters. Our results show that due to fast exchange of amide protons with water in the soluble heme-containing domain of cyb5, coherent (1)H-(1)H dipolar interactions are averaged out for these protons while alpha and side chain protons show residual dipolar couplings that can be obtained from (1)H-(1)H RFDR experiments. The appearance of resonances with distinct chemical shift values in (1)H-(1)H RFDR spectra enabled the identification of residues (mostly from the transmembrane region) of cytb5 that interact with micelles. PMID:24657390

Pandey, Manoj Kumar; Vivekanandan, Subramanian; Yamamoto, Kazutoshi; Im, Sangchoul; Waskell, Lucy; Ramamoorthy, Ayyalusamy

2014-05-01

362

Probe for high resolution NMR with sample reorientation  

DOEpatents

An improved NMR probe and method are described which substantially improve the resolution of NMR measurements made on powdered or amorphous or otherwise orientationally disordered samples. The apparatus mechanically varies the orientation of the sample such that the time average of two or more sets of spherical harmonic functions are zero.

Pines, Alexander (Berkeley, CA); Samoson, Ago (Tallinn, SU)

1990-01-01

363

Probe for high resolution NMR with sample reorientation  

DOEpatents

An improved NMR probe and method are described which substantially improve the resolution of NMR measurements made on powdered or amorphous or otherwise orientationally disordered samples. The apparatus mechanically varies the orientation of the sample such that the time average of two or more sets of spherical harmonic functions are zero. 8 figs.

Pines, A.; Samoson, A.

1990-02-06

364

Probing helical hydrophobic binding sites in branched starch polysaccharides using NMR spectroscopy.  

PubMed

Branched starch polysaccharides are capable of binding multiple hydrophobic guests, but their exploitation as multivalent hosts and in functional materials is limited by their structural complexity and diversity. Linear ?(1-4)-linked glucose oligosaccharides are known to bind hydrophobic guests inside left-handed single helices in solution and the solid state. Here, we describe the development of an amphiphilic probe that binds to linear ?(1-4)-linked glucose oligosaccharides and undergoes a conformational switch upon complexation, which gives rise to dramatic changes in the (1)H NMR spectrum of the probe. We use this probe to explore hydrophobic binding sites in the branched starch polysaccharides amylopectin and ?-limit dextrin. Diffusion-ordered (DOSY), nuclear Overhauser effect (NOESY) and chemical shift perturbation (HSQC) NMR experiments are utilised to provide evidence that, in aqueous solution, branched polysaccharides bind hydrophobic guests in well-defined helical binding sites, similar to those reported for complexation by linear oligosaccharides. By examining the binding affinity of the probe to systematically enzymatically degraded polysaccharides, we deduce that the binding sites for hydrophobic guests can be located on internal as well as external branches and that proximal ?(1-6)-linked branch points weaken but do not prevent complexation. PMID:24123516

Beeren, Sophie R; Meier, Sebastian; Hindsgaul, Ole

2013-11-25

365

NMR crystallography for structural characterization of oxovanadium(v) complexes: deriving coordination geometry and detecting weakly coordinated ligands at atomic resolution in the solid state.  

PubMed

NMR crystallography is an emerging method for atomic-resolution structural analysis of ubiquitous vanadium(V) sites in inorganic and bioinorganic complexes as well as vanadium-containing proteins. NMR crystallography allows for characterization of vanadium(V) containing solids, based on the simultaneous measurement of (51)V-(15)N internuclear distances and anisotropic spin interactions, described by (13)C, (15)N, and (51)V chemical shift anisotropy and (51)V electric field gradient tensors. We show that the experimental (51)V, (13)C, and (15)N NMR parameters are essential for inferring correct coordination numbers and deriving correct geometries in density functional theory (DFT) calculations, particularly in the absence of single-crystal X-ray structures. We first validate this approach on a structurally known vanadium(V) complex, ((15)N-salicylideneglycinate)-(benzhydroxamate)oxovanadium(V), VO(15)NGlySalbz. We then apply this approach to derive the three-dimensional structure of (methoxo)((15)N-salicylidene-glycinato)oxovanadium(V) with solvated methanol, [VO((15)NGlySal)(OCH3)]·(CH3OH). This is a representative complex with potentially variable coordination geometry depending on the solvation level of the solid. The solid material containing molecules of CH3OH, formally expressed as [VO((15)NGlySal)(OCH3)]·(CH3OH), is found to have one molecule of CH3OH weakly coordinated to the vanadium. The material is therefore best described as [VO((15)NGlySal)(OCH3)(CH3OH)] as deduced by the combination of multinuclear solid-state NMR experiments and DFT calculations. The approach reported here can be used for structural analysis of systems that are not amenable to single-crystal X-ray diffraction characterization and which can contain weakly associated solvents. PMID:25590382

Li, Mingyue; Yehl, Jenna; Hou, Guangjin; Chatterjee, Pabitra B; Goldbourt, Amir; Crans, Debbie C; Polenova, Tatyana

2015-02-16

366

Solid-State NMR Investigation of the Membrane-Disrupting Mechanism of Antimicrobial Peptides MSI-78 and MSI-594 Derived from Magainin 2 and Melittin  

PubMed Central

The mechanism of membrane interaction of two amphipathic antimicrobial peptides, MSI-78 and MSI-594, derived from magainin-2 and melittin, is presented. Both the peptides show excellent antimicrobial activity. The 8-anilinonaphthalene-1-sulfonic acid uptake experiment using Escherichia coli cells suggests that the outer membrane permeabilization is mainly due to electrostatic interactions. The interaction of MSI-78 and MSI-594 with lipid membranes was studied using 31P and 2H solid-state NMR, circular dichroism, and differential scanning calorimetry techniques. The binding of MSI-78 and MSI-594 to the lipid membrane is associated with a random coil to ?-helix structural transition. MSI-78 and MSI-594 also induce the release of entrapped dye from POPC/POPG (3:1) vesicles. Measurement of the phase-transition temperature of peptide-DiPoPE dispersions shows that both MSI-78 and MSI-594 repress the lamellar-to-inverted hexagonal phase transition by inducing positive curvature strain. 15N NMR data suggest that both the peptides are oriented nearly perpendicular to the bilayer normal, which infers that the peptides most likely do not function via a barrel-stave mechanism of membrane-disruption. Data obtained from 31P NMR measurements using peptide-incorporated POPC and POPG oriented lamellar bilayers show a disorder in the orientation of lipids up to a peptide/lipid ratio of 1:20, and the formation of nonbilayer structures at peptide/lipid ratio >1:8. 2H-NMR experiments with selectively deuterated lipids reveal peptide-induced disorder in the methylene units of the lipid acyl chains. These results are discussed in light of lipid-peptide interactions leading to the disruption of membrane via either a carpet or a toroidal-type mechanism. PMID:16603496

Ramamoorthy, Ayyalusamy; Thennarasu, Sathiah; Lee, Dong-Kuk; Tan, Anmin; Maloy, Lee

2006-01-01

367

Electronic Structure, Chemical Bonding, and Solid-State NMR Spectroscopy of the Digallides of Ca, Sr, and Ba  

Microsoft Academic Search

Combined application of 69,71 Ga NMR spectroscopy and quan- tum mechanical calculations reveals the chemical bonding in the digallides of Ca, Sr, and Ba. An analysis of the electron localization function (ELF) shows honeycomb-like 63 nets of the Ga atoms as the most prominent struc- tural features in SrGa2 and BaGa2 .F or CaGa2 a description of a 3+1-coordi- nated

Frank Haarmann; Katrin Koch; Daniel Grner; Walter Schnelle; Oliver Pecher; Raul Cardoso-Gil; Horst Borrmann; Helge Rosner; Yuri Grin

2009-01-01

368

Solid-state [sup 1]H MAS NMR characterization of [gamma]-alumina and modified [gamma]-aluminas  

SciTech Connect

[gamma]-alumina is used extensively as a catalyst support material. [sup 1]H single pulse MAS and CPMG T[sub 2]/CSA-filter NMR experiments have been performed in order to characterize the hydroxyl structure of [gamma]-alumina, as well as fluoride- and phosphate-modified [gamma]-alumina materials. The authors have shown that problems associated with the strong homonuclear dipole-dipole interactions between protons of neighboring OH groups can be overcome by isotopic dilution of the alumina surface protons by deuterium exchange. Partially deuterated [gamma]-alumina yields resonances at around -0.3, 0.3, 1.5, 2.4, 4.0, 5.0, 6.5, 7.1, and 7.8 ppm. CPMG T[sub 2]/CSA-filter NMR experiments performed on alumina calcined at 700[degrees]C show that five different types of hydroxyl groups are present. CPMG T[sub 2]/CSA-filter NMR of deuterated F/Al[sub 2]O[sub 3] produces a resonance at 11.5 ppm in addition to a range of resonances between -0.2 and 7 ppm. NMR data for calcined P/Al[sub 2]O[sub 3] and P-Mo(12)/Al[sub 2]O[sub 3] (wt% P = 0.0-10.0) show that polymeric orthophosphates produce a resonance at 3.4 ppm, while the monomeric orthophosphate species gives rise to a resonance at 1.2 ppm. 41 refs., 6 figs.

DeCanio, E.C.; Edwards, J.C. (Texaco Research and Development Department, Beacon, NY (United States)); Bruno, J.W. (Wesleyan Univ., Middletown, CT (United States))

1994-07-01

369

Triphenylsilyl perchlorate revisited: /sup 29/Si and /sup 35/Cl NMR spectroscopy and x-ray crystallography showing covalent nature in both solution and the solid state. Difficulties in observing long-lived silyl cations in the condensed state  

SciTech Connect

/sup 29/Si and /sup 35/Cl NMR spectroscopic and X-ray crystallographic study of triphenylsilyl perchlorate shows it to be a covalent perchloryl ester in both solution and the solid state. The results are in accord with earlier studies notably those of Wannagat but contrast the recent claim by Lambert etal. (J. Am. Chem. Soc. 1986, 108, 2482) for NMR observation of long-lived ionic triphenylsilyl perchlorate.

Prakash, G.K.S.; Keyaniyan, S.; Aniszfeld, R.; Heiliger, L.; Olah, G.A.; Stevens, R.C.; Choi, H.K.; Bau, R.

1987-08-19

370

Solid-state 13C NMR studies of dissolved organic matter in pore waters from different depositional environments  

USGS Publications Warehouse

Dissolved organic matter (DOM) in pore waters from sediments of a number of different depositional environments was isolated by ultrafiltration using membranes with a nominal molecular weight cutoff of 500. This > 500 molecular weight DOM represents 70-98% of the total DOM in these pore waters. We determined the gross chemical structure of this material using both solid-state 13C nuclear magnetic resonance spectroscopy and elemental analysis. Our results show that the DOM in these pore waters appears to exist as two major types: one type dominated by carbohydrates and paraffinic structures and the second dominated by paraffinic and aromatic structures. We suggest that the dominance of one or the other structural type of DOM in the pore water depends on the relative oxidizing/reducing nature of the sediments as well as the source of the detrital organic matter. Under dominantly anaerobic conditions carbohydrates in the sediments are degraded by bacteria and accumulate in the pore water as DOM. However, little or no degradation of lignin occurs under these conditions. In contrast, sediments thought to be predominantly aerobic in character have DOM with diminished carbohydrate and enhanced aromatic character. The aromatic structures in the DOM from these sediments are thought to arise from the degradation of lignin. The large amounts of paraffinic structures in both types of DOM may be due to the degradation of unidentified paraffinic materials in algal or bacterial remains. ?? 1987.

Orem, W.H.; Hatcher, P.G.

1987-01-01

371

Solid-state NMR characterization of high-loading solid solutions of API and excipients formed by electrospinning.  

PubMed

A major focus area in improving pharmaceutical manufacturing is decreasing powder-handling steps such as milling, granulation, and blending. One approach to go directly from active pharmaceutical ingredients (API) and excipients in solution to a formulated drug product is to use electrospinning to make solid formulations of API in a polymer. Because of the rapid evaporation rate in electrospinning, the process usually results in a well-mixed solid dispersion of drugs in the polymer. In this study, solid-state nuclear magnetic resonance is used to examine phase separation in formulations of aliskiren (SPP) and indomethacin (IND) with polyvinylpyrrolidone (PVP) prepared by electrospinning and hot-melt extrusion. It was found that 1:1 SPP-PVP, 1:1 IND-PVP, and 4:1 SPP-PVP formulations prepared by electrospinning are homogeneous solid solutions down to a 2-11 nm length scale, whereas a 4:1 SPP-PVP formulation prepared by hot-melt extrusion exhibits phase separation with domain sizes of 20-100 nm or larger. PMID:22213488

Brettmann, Blair; Bell, Erin; Myerson, Allan; Trout, Bernhardt

2012-04-01

372

Solid-state NMR study of the post-fluorination of (C2.5F)n fluorine-GIC.  

PubMed

The conversion of (C2.5F)n fluorine-graphite intercalation compounds (GIC) into covalent graphite fluoride during a post-treatment in pure F2 gas is studied by solid-state NMR. First, a careful characterization of the starting material is performed; in particular, for the first time for fluorinated carbons, two-dimensional 19F--> 13C cross-polarization wide-line separation (CP-WISE) experiments were carried out. This completes the classical NMR data such as 19F and 13C chemical shifts, quantitative 13C solid echo, and C-F bond length measurements, which were estimated by dipolar recoupling using inverse CP MAS. The data of the raw (C2.5F)n and of the samples post-fluorinated at 350, 450, and 550 degrees C were compared to investigate the C-F bonding as a function of the treatment temperature. The C-F bonding is discussed taking into account a hyperconjugation of the C-F bonds with neighboring unfluorinated carbon atoms. PMID:18052273

Giraudet, Jérôme; Dubois, Marc; Guérin, Katia; Delabarre, Céline; Hamwi, André; Masin, Francis

2007-12-27

373

Characterization of Mg2+ Binding to the DNA Repair Protein Apurinic/Apyrimidic Endonuclease 1 (APE1) via Solid-State 25Mg NMR Spectroscopy  

PubMed Central

Apurinic/apyrimidinic endonuclease 1 (APE1), a member of the divalent cation-dependent phosphoesterase superfamily of proteins that retain the conserved four-layered ?/?-sandwich structural core, is an essential protein that functions as part of base excision repair to remove mutagenic and cytotoxic abasic sites from DNA. Using low temperature solid-state 25Mg NMR spectroscopy and various mutants of APE1, we demonstrate that Mg2+ binds to APE1 and a functional APE1-substrate DNA complex with an overall stoichiometry with respect to Mg2+ of one per mole of APE1 as predicted by the X-ray work of Tainer and coworkers. However, the NMR spectra show that the single Mg2+ site is disordered. We discuss the probable reasons for the disorder at the Mg2+ binding site. The most likely source of this disorder is arrangement of the protein ligands about the Mg2+ (cis and trans isomers). The existence of these isomers reinforces the notion of the plasticity of the metal binding site within APE1. PMID:18576638

Lipton, A. S.; Heck, R. W.; Primak, S.; McNeill, D. R.; Wilson, D. M.; Ellis, P. D.

2008-01-01

374

Alignment of druglike compounds in lipid bilayers analyzed by solid-state (19)F-NMR and molecular dynamics, based on dipolar couplings of adjacent CF3 groups.  

PubMed

Solid-state (19)F-NMR spectroscopy is frequently used to analyze the structure and dynamics of lipophilic drugs and peptides embedded in biomembranes. The homonuclear dipolar couplings of trifluoromethyl (CF3) labels can provide valuable parameters such as orientational constraints and/or distances. To characterize the complex dipolar patterns of multiple (19)F spin interactions, three different model compounds carrying two CF3 groups in meta-position on a phenyl ring were incorporated in macroscopically aligned DMPC bilayers. The dipolar patterns obtained with the CPMG (Carr-Purcell-Meiboom-Gill) multipulse sequence were analyzed to yield simultaneously the intra-CF3 and intergroup dipolar coupling values. The fluorine-fluorine distances were predicted by a density functional calculation, and the alignment of the labeled molecular segment could be determined from these distances and the dipolar coupling values. The different compounds were found to align in the lipid bilayer according to their amphiphilic properties, though with a weak anisotropic preference that is typical of solutes in liquid crystals. The residual dipolar couplings were used to calculate Saupe order parameters. For the least complex molecule, (CF3)2-BA, an orientational probability function for the solute in the lipid matrix could be derived. The overall description of how (CF3)2-BA is embedded in the bilayer was independently assessed by molecular dynamics simulations, and compared in structural and dynamical terms with the results of the NMR experiments. PMID:22439912

Dürr, Ulrich H N; Afonin, Sergii; Hoff, Barbara; de Luca, Giuseppina; Emsley, James W; Ulrich, Anne S

2012-04-26

375

Solid state {sup 31}P/{sup 27}Al and {sup 31}P/{sup 23}Na MAS NMR dipolar dephasing investigations of connectivity in sodium aluminophosphate glasses  

SciTech Connect

Solid state {sup 31}P/{sup 27}Al and {sup 31}P/{sup 23}Na MAS NMR dipolar dephasing experiments have been used to investigate the spatial distribution of aluminum and sodium cations with respect to the phosphate backbone for a series of sodium aluminophosphate glasses, xAl{sub 2}O{sub 3}{center_dot}50Na{sub 2}O{center_dot}(50{minus}x)P{sub 2}O{sub 5} (0{le} x {le} 17.5). From the {sup 31}P/{sup 27}Al and {sup 31}P/{sup 23}Na connectivity data gathered, information about the medium range order in these glasses is obtained. The expanded connectivity data allows for better identification and interpretation of the new resonances observed in the {sup 31}P MAS NMR spectra with the addition of alumina. The results of the dipolar dephasing experiments show that the sodium-phosphate distribution remains relatively unchanged for the glass series, and that the addition of aluminum occurs primarily through the depolymerization of the phosphate tetrahedral backbone.

LANG,DAVID P.; ALAM,TODD M.; BENCOE,DENISE N.

2000-05-01

376

The influence of water on the nanomechanical behavior of the plant biopolyester cutin as studied by AFM and solid-state NMR.  

PubMed Central

Atomic force microscopy and solid-state nuclear magnetic resonance have been used to investigate the effect of water absorption on the nanoscale elastic properties of the biopolyester, cutin, isolated from tomato fruit cuticle. Changes in the humidity and temperature at which fruits are grown or stored can affect the plant surface (cuticle) and modify its susceptibility to pathogenic attack by altering the cuticle's rheological properties. In this work, atomic force microscopy measurements of the surface mechanical properties of isolated plant cutin have been made as a first step to probing the impact of water uptake from the environment on surface flexibility. A dramatic decrease in surface elastic modulus (from approximately 32 to approximately 6 MPa) accompanies increases in water content as small as 2 wt %. Complementary solid-state nuclear magnetic resonance measurements reveal enhanced local mobility of the acyl chain segments with increasing water content, even at molecular sites remote from the covalent cross-links that are likely to play a crucial role in cutin's elastic properties. PMID:11053149

Round, A N; Yan, B; Dang, S; Estephan, R; Stark, R E; Batteas, J D

2000-01-01

377

Real-time observation of polymer network formation by liquid- and solid-state NMR revealing multistage reaction kinetics.  

PubMed

The reaction rate for the end-cross-linking process of vinyl-terminated poly(dimethylsiloxane) by a cross-linker with four Si-H functionalities in the presence of solvent was studied by (1)H liquid-state NMR in dependence of the reaction temperature. The properties of the resulting polymer networks, i.e., the gel-point and the formation of the elastically effective network, were monitored in situ during the reaction by single-evolution-time (1)H double-quantum (SET-DQ) low-field NMR. It was found that the cross-linking kinetics shows no uniform reaction order for the conversions of the functional groups before the topological gelation threshold of the polymer network. The two NMR methods are combined to investigate the formation of the elastically effective network in dependence of the conversion of the functional groups of the precursor polymers and the cross-linker. The high chemical and time resolution of the experiments enabled an in-depth analysis of the reaction kinetics, allowing us to conclude on a multistage model for PDMS network formation by hydrosilylation-based end-linking in the presence of solvent. We found that the nonuniform network formation kinetics originates from a dependence of the apparent reaction rate on the number of the Si-H groups of the cross-linker that have already reacted during the progress of the reaction. The fastest overall reaction rate is observed in a range until each cross-linker has reacted once on average, and a uniform apparent overall reaction order of unity with respect to cross-linker concentration is only found at a later stage, when multiply reacted cross-linker molecules with similar reactivity dominate. PMID:22650309

Kovermann, Michael; Saalwächter, Kay; Chassé, Walter

2012-06-28

378

Electronic structure, chemical bonding, and solid-state NMR spectroscopy of the digallides of Ca, Sr, and Ba.  

PubMed

Combined application of (69,71)Ga NMR spectroscopy and quantum mechanical calculations reveals the chemical bonding in the digallides of Ca, Sr, and Ba. An analysis of the electron localization function (ELF) shows honeycomb-like 6(3) nets of the Ga atoms as the most prominent structural features in SrGa(2) and BaGa(2). For CaGa(2) a description of a 3+1-coordinated Ga atom is revealed by the ELF and by an analysis of interatomic distances. The NMR spectroscopic signal shift is mainly due to the Knight shift and is almost equal for the investigated digallides, whereas the anisotropy of the signal shift decreases with the radius of the alkaline-earth metals. Calculated and observed values of the electric field gradient (EFG) are in good agreement for CaGa(2) and BaGa(2) but differ by about 21 % for SrGa(2) indicating structural instability. Better agreement is achieved by considering a puckering of the Ga layers. For BaGa(2) an instability of the structure is indicated by a peak in the density of states at the Fermi level, which is shifted to lower energies when taking puckering of the Ga layers into account. Both structural modifications are confirmed by crystallographic information. The Fermi velocity of the electrons is strongly anisotropic and is largest in the (001) plane of the crystal structure. This results in an alignment of the crystallites with the [001] axis perpendicular to the magnetic field as observed in (69,71)Ga NMR spectroscopy and magnetic susceptibility experiments. The electron transport is predominantly mediated by the Ga-Ga p(x)- and p(y)-like electrons in the (001) plane. The specific heat capacity of BaGa(2) was determined and indicated the absence of phase transitions between 1.8 and 320 K. PMID:19123208

Haarmann, Frank; Koch, Katrin; Grüner, Daniel; Schnelle, Walter; Pecher, Oliver; Cardoso-Gil, Raul; Borrmann, Horst; Rosner, Helge; Grin, Yuri

2009-01-01

379

Structure and dynamics of the lipid modifications of a transmembrane ?-helical peptide determined by ²H solid-state NMR spectroscopy.  

PubMed

The fusion of biological membranes is mediated by integral membrane proteins with ?-helical transmembrane segments. Additionally, those proteins are often modified by the covalent attachment of hydrocarbon chains. Previously, a series of de novo designed ?-helical peptides with mixed Leu/Val sequences was presented, mimicking fusiogenically active transmembrane segments in model membranes (Hofmann et al., Proc. Natl. Acad. Sci. USA 101 (2004) 14776-14781). From this series, we have investigated the peptide LV16 (KKKW LVLV LVLV LVLV LVLV KKK), which was synthesized featuring either a free N-terminus or a saturated N-acylation of 2, 8, 12, or 16 carbons. We used ²H and ³¹P NMR spectroscopy to investigate the structure and dynamics of those peptide lipid modifications in POPC and DLPC bilayers and compared them to the hydrocarbon chains of the surrounding membrane. Except for the C2 chain, all peptide acyl chains were found to insert well into the membrane. This can be explained by the high local lipid concentrations the N-terminal lipid chains experience. Further, the insertion of these peptides did not influence the membrane structure and dynamics as seen from the ²H and ³¹P NMR data. In spite of the fact that the longer acyl chains insert into the membrane, they do not adapt their lengths to the thickness of the bilayer. Even the C16 lipid chain on the peptide, which could match the length of the POPC palmitoyl chain, exhibited lower order parameters in the upper chain, which get closer and finally reach similar values in the lower chain region. ²H NMR square law plots reveal motions of slightly larger amplitudes for the peptide lipid chains compared to the surrounding phospholipids. In spite of the significantly different chain lengths of the acylations, the fraction of gauche defects in the inserted chains is constant. PMID:21192915

Penk, Anja; Müller, Matthias; Scheidt, Holger A; Langosch, Dieter; Huster, Daniel

2011-03-01

380

State of water in hybrid sulfonated poly(ether ether ketone) - silica membranes by 1H solid-state NMR  

NASA Astrophysics Data System (ADS)

The state of water in fully hydrated sulfonated poly(ether ether ketone) - silica hybrid proton exchange membranes were characterized in terms of the exchange rate between bound and free water, the water dynamics in each phase, and the relative water populations by 1H ODESSA and transverse magnetization relaxation NMR. The exchange rate, the amount of bound water, and the reorientation of free water molecules increase in the presence of silica particles. The dynamics of bound water was described by the Lévy statistics with a Cauchy propagator. The proton exchange membranes performances could be improved by addition of small concentrations of silica in the range of 5-10 wt.%.

Baias, Maria; Demco, Dan E.; Blümich, Bernhard; Möller, Martin

2009-04-01

381

Proton exchange in hybrid sulfonated poly(ether ether ketone) silica membranes by 1H solid-state NMR  

NASA Astrophysics Data System (ADS)

Enthalpy of activation for proton exchange processes in fully hydrated hybrid sulfonated poly(ether ether ketone)-silica (SPEEK/SiO 2) membranes were measured from the 1H NMR spectra under magic angle sample spinning (MAS). For the first time Eyring function is used for this purpose. Two exchange processes between different water pools were detected. The isotropic chemical shift of the 1H spectrum allows us to obtain information about the normalized enthalpy of activation characterizing the water exchange. These results show that the proton exchange membranes performances could be improved by addition of small concentrations of silica in the range of 5-10 wt.%.

Baias, Maria; Demco, Dan E.; Colicchio, Irene; Blümich, Bernhard; Möller, Martin

2008-05-01

382

Use of solid-state 13C NMR in structural studies of humic acids and humin from Holocene sediments  

USGS Publications Warehouse

13C NMR spectra of solid humic substances in Holocene sediments have been obtained using cross polarization with magic-angle sample spinning techniques. The results demonstrate that this technique holds great promise for structural characterizations of complex macromolecular substances such as humin and humic acids. Quantifiable distinctions can be made between structural features of aquatic and terrestrial humic substances. The aliphatic carbons of the humic substances are dominant components suggestive of input from lipid-like materials. An interesting resemblance is also noted between terrestrial humic acid and humin spectra. ?? 1980.

Hatcher, P.G.; VanderHart, D.L.; Earl, W.L.

1980-01-01

383

Determination of the Average Aromatic Cluster Size of Fossil Fuels by Solid-State NMR at High Magnetic Field  

SciTech Connect

We show that the average aromatic cluster size in complex carbonaceous materials can be accurately determined using fast magic-angle spinning (MAS) NMR at a high magnetic field. To accurately quantify the nonprotonated aromatic carbon, we edited the 13C spectra using the recently reported MAS-synchronized spin–echo, which alleviated the problem of rotational recoupling of 1H-13C dipolar interactions associated with traditional dipolar dephasing experiments. The dependability of this approach was demonstrated on selected Argonne Premium coal standards, for which full sets of basic structural parameters were determined with high accuracy.

Mao, Kanmi [ExxonMobile Research and Engineering Co.; Kennedy, Gordon J. [ExxonMobile Research and Engineering Co.; Althaus, Stacey M. [Ames Laboratory; Pruski, Marek [Ames Laboratory

2013-01-07

384

Ionic Pathways in Li13Si4 investigated by (6)Li and (7)Li solid state NMR experiments.  

PubMed

Local environments and dynamics of lithium ions in the binary lithium silicide Li13Si4 have been studied by (6)Li MAS-NMR, (7)Li spin-lattice relaxation time and site-resolved (7)Li 2D exchange NMR measurements as a function of mixing time. Variable temperature experiments result in distinct differences in activation energies characterizing the transfer rates between the different lithium sites. Based on this information, a comprehensive picture of the preferred ionic transfer pathways in this silicide has been developed. With respect to local mobility, the results of the present study suggests the ordering Li6/Li7>Li5>Li1>Li4 >Li2/Li3. Mobility within the z=0.5 plane is distinctly higher than within the z=0 plane, and the ionic transfer between the planes is most facile via Li1/Li5 exchange. The lithium ionic mobility can be rationalized on the basis of the type of the coordinating silicide anions and the lithium-lithium distances within the structure. Lithium ions strongly interacting with the isolated Si(4-) anions have distinctly lower mobility than those the coordination of which is dominated by Si2(6-) dumbbells. PMID:25524128

Dupke, Sven; Langer, Thorsten; Winter, Florian; Pöttgen, Rainer; Winter, Martin; Eckert, Hellmut

2015-02-01

385

Development of Solid State NMR Methods for the Structural Characterization of Membrane Proteins: Applications to Understand Multiple Sclerosis  

SciTech Connect

Multiple sclerosis (MS) is a relapsing-remitting disorder of the central nervous system that results in the loss of the myelin sheaths insulating nerve fibers (axons). Strong evidence suggests that MS is an autoimmune disease mediated by T-cell and antibody responses against myelin antigens. Myelin oligodendrocyte glycoprotein (MOG) is a 26 kD to 28 kD an integral membrane protein of the central nervous system implicated as a target for autoaggressive antibodies in MS. To date, the conformation of MOG in association with the myelin membrane is unknown and the exact nature of the interactions between this protein and disease-inducing immune responses have not been determined. Since membrane associated proteins are typically characterized by decreased correlation times, solution state NMR methodologies are often impracticable. Membrane proteins are also often difficult to crystallize for X-ray diffraction studies, Consequently, there is an urgent need to develop new structure characterization tools for this important class of biomolecules. The research described here overviews the initial stages of our effort to develop an integrated, NMR based approach to structural studies of MOG over the many structural domains it is postulated to posses. The structural knowledge gained about this important MS antigen in its native environment will contribute significantly to our understanding of its function in vivo. This project will also aid in the development of therapeutics to inhibit the antigedantibody interaction and thus prevent demyelination in MS patients.

Cosman, M; Tran, A T; Ulloa, J; Maxwell, R S

2003-03-04

386

Characterizing Surface Acidic Sites in Mesoporous-Silica-Supported Tungsten Oxide Catalysts Using Solid State NMR and Quantum Chemistry Calculations  

SciTech Connect

The acidic sites in dispersed tungsten oxide supported on SBA-15 mesoporous silica were investigated using a combination of pyridine titration, both fast-, and slow-MAS {sup 15}N NMR, static {sup 2}H NMR, and quantum chemistry calculations. It is found that the bridged acidic -OH groups in surface adsorbed tungsten dimers (i.e., W-OH-W) are the Broensted acid sites. The unusually strong acidity of these Broensted acid sites is confirmed by quantum chemistry calculations. In contrast, terminal W-OH sites are very stable and only weakly acidic as are terminal Si-OH sites. Furthermore, molecular interactions between pyridine molecules and the dimer Broensted and terminal W-OH sites for dispersed tungsten oxide species is strong. This results in restricted molecular motion for the interacting pyridine molecules even at room temperature, i.e., a reorientation mainly about the molecular 2-fold axis. This restricted reorientation makes it possible to estimate the relative ratio of the Broensted (tungsten dimer) to the weakly acidic terminal W-OH sites in the catalyst using the slow-MAS {sup 1}H-{sup 15}N CP PASS method.

Hu, Jian Z.; Kwak, Ja Hun; Wang, Yong; Hu, Mary Y.; Turcu, Romulus VF; Peden, Charles HF

2011-10-18

387

4 Kelvin Cryogenic Probe for 500 MHz NMR  

NASA Astrophysics Data System (ADS)

This paper describes the development of a 4 K cryogenic probe for 500 MHz Nuclear Magnetic Resonance (NMR) analyses. As thermal noise is proportional to the square root of the RF coil temperature, sensitivity of a 4 K probe is expected to be double that of conventional 25 K probes. The 4 K probe apparatus consists of a closed-cycle cooling system, a 5 m long helium transfer line and the NMR probe itself. The cooling system produces cold helium mist with a Gifford-McMahon/Joule-Thomson (GM/JT) cryocooler. The helium mist traverses the transfer line and then cools the RF coil. An acceptable power input of 3.6 W for the NMR pulse sequence was demonstrated, which was more than the time-averaged heat input, 2 W, generated by a multi-dimensional NMR pulse sequence. The basic NMR sensitivity of the cryogenic probe remains insufficient at present, but increasing B1xy (the field component in the xy plane generated by unit current of the RF coil) and decreasing the noise temperature of the preamplifier are promising approaches for achieving higher sensitivity in the future.

Yoshimoto, F.; Takahashi, M.; Horiuchi, T.; Hobo, F.; Inoue, K.; Miki, T.; Hamada, M.; Okamura, T.; Yokoyama, S.; Maeda, H.

2006-04-01

388

Characterization of Dispersed Heteropoly Acid on Mesoporous Zeolite Using Solid-State P-31 NMR Spin-Lattice Relaxation  

SciTech Connect

Dispersion and quantitative characterization of supported catalysts is a grand challenge in catalytic science. In this paper, heteropoly acid H3PW12O40 (HPA) is dispersed on mesoporous zeolite silicalite-1 derived from hydrothermal synthesis using carbon black nanoparticle templates, and the catalytic activity is studied for 1-butene isomerization. The HPAs supported on conventional zeolite and on mesoporous zeolite exhibit very different activities and thus provide good model systems to investigate the structure dependence of the catalytic properties. The HPA on mesoporous silicalite-1 shows enhanced catalytic activity for 1-butene isomerization, while HPA on conventional silicalite-1 exhibits low activity. To elucidate the structural difference, supported HPA catalysts are characterized using a variety of techniques, including 31P magic angle spinning nuclear magnetic resonance, and are shown to contain a range of species on both mesoporous and conventional zeolites. However, contrary to studies reported in the literature, conventional NMR techniques and chemical shifts alone do not provide sufficient information to distinguish the dispersed and aggregated surface species. The dispersed phase and the nondispersed phase can only be unambiguously and quantitatively characterized using spin-lattice relaxation NMR techniques. The HPA supported on mesoporous zeolite contains a fast relaxation component related to the dispersed catalyst, giving a much higher activity, while the HPA supported on conventional zeolite has essentially only the slow relaxation component with very low activity. The results obtained from this work demonstrate that the combination of spinning sideband fitting and spin-lattice relaxation techniques can provide detailed structural information on not only the Keggin structure for HPA but also the degree of dispersion on the support.

Zhu, Kake; Hu, Jian Z.; She, Xiaoyan; Liu, Jun; Nie, Zimin; Wang, Yong; Peden, Charles HF; Kwak, Ja Hun

2009-09-01

389

Structure in solid state of 3,3?-diindolylmethane derivatives, potent cytotoxic agents against human tumor cells, followed X-ray diffraction and 13C CP/MAS NMR analyses  

NASA Astrophysics Data System (ADS)

The 5,5'-disubstituted-3,3'-diindolylmethanes 1, 2 have been prepared and their structure was analyzed by X-ray and NMR techniques. The X-ray diffraction studies revealed interesting C-H⋯ ? intermolecular interactions which may play role in characterization of their biological features. In 1H and 13C NMR spectra in solution and in 13C CPMAS NMR spectra in solid state only a single pattern of signals was observed. Both compounds reduce the growth of MCF7 (breast), NCI-H460 (lung), and SF-268 (NCS) cells dramatically.

Maciejewska, Dorota; Wolska, Irena; Niemyjska, Maria; ?ero, Pawe?

2005-10-01

390

A Mo-95 and C-13 Solid-state NMR and Relativistic DFT Investigation of Mesitylenetricarbonylmolybdenum(0) -a Typical Transition Metal Piano-stool Complex  

SciTech Connect

The chemical shift (CS) and electric field gradient (EFG) tensors in the piano-stool compound mesitylenetricarbonylmolybdenum(0), 1, have been investigated via {sup 95}Mo and {sup 13}C solid-state magic-angle spinning (MAS) NMR as well as relativistic zeroth-order regular approximation density functional theory (ZORA-DFT) calculations. Molybdenum-95 (I = 5/2) MAS NMR spectra acquired at 18.8 T are dominated by the anisotropic chemical shift interaction ({Omega} = 775 {+-} 30 ppm) rather than the 2nd-order quadrupolar interaction (C{sub Q} = -0.96 {+-} 0.15 MHz), an unusual situation for a quadrupolar nucleus. ZORA-DFT calculations of the {sup 95}Mo EFG and CS tensors are in agreement with the experimental data. Mixing of appropriate occupied and virtual d-orbital dominated MOs in the region of the HOMO-LUMO gap are shown to be responsible for the large chemical shift anisotropy. The small, but non-negligible, {sup 95}Mo quadrupolar interaction is discussed in terms of the geometry about Mo. Carbon-13 CPMAS spectra acquired at 4.7 T demonstrate the crystallographic and magnetic nonequivalence of the twelve {sup 13}C nuclei in 1, despite the chemical equivalence of some of these nuclei in isotropic solutions. The principal components of the carbon CS tensors are determined via a Herzfeld-Berger analysis, and indicate that motion of the mesitylene ring is slow compared to a rate which would influence the carbon CS tensors (i.e. tens of {micro}s). ZORA-DFT calculations reproduce the experimental carbon CS tensors accurately. Oxygen-17 EFG and CS tensors for 1 are also calculated and discussed in terms of existing experimental data for related molybdenum carbonyl compounds. This work provides an example of the information available from combined multi-field solid-state multinuclear magnetic resonance and computational investigations of transition metal compounds, in particular the direct study of quadrupolar transition metal nuclei with relatively small magnetic moments.

Bryce, David L.; Wasylishen, Roderick E.

2002-06-21

391

A high-pressure NMR probe for aqueous geochemistry.  

PubMed

A non-magnetic piston-cylinder pressure cell is presented for solution-state NMR spectroscopy at geochemical pressures. The probe has been calibrated up to 20?kbar using in?situ ruby fluorescence and allows for the measurement of pressure dependencies of a wide variety of NMR-active nuclei with as little as 10??L of sample in a microcoil. Initial (11)B?NMR spectroscopy of the H3BO3-catechol equilibria reveals a large pressure-driven exchange rate and a negative pressure-dependent activation volume, reflecting increased solvation and electrostriction upon boron-catecholate formation. The inexpensive probe design doubles the current pressure range available for solution NMR spectroscopy and is particularly important to advance the field of aqueous geochemistry. PMID:24989120

Pautler, Brent G; Colla, Christopher A; Johnson, Rene L; Klavins, Peter; Harley, Stephen J; Ohlin, C André; Sverjensky, Dimitri A; Walton, Jeffrey H; Casey, William H

2014-09-01

392

Characterization of Peptidoglycan in Fem-deletion Mutants of Methicillin-resistant Staphylococcus aureus by Solid-State NMR  

PubMed Central

Compositional analysis of the peptidoglycan (PG) of a wild-type methicilin-resistant Staphylococcus aureus and its fem-deletion mutants has been performed on whole cells and cell walls using stable-isotope labeling and rotational-echo double-resonance NMR. The labels included [1-13C, 15N]glycine and L-[?-15N]lysine (for a direct measure of the number of glycyl residues in the bridging segment), [1-13C]glycine and L-[?-15N]lysine (concentration of bridge-links), and D-[1-13C]alanine and [15N]glycine (concentrations of cross-links and wall teichoic acids). The bridging segment length changed from 5.0 glycyl residues (wild-type strain) to 2.5±0.1 (FemB) with modest changes in cross-link and bridge-link concentrations. This accurate in situ measurement for the FemB mutant indicates a heterogeneous PG-structure with 25% monoglycyl- and 75% triglycyl-bridges. When the bridging segment was reduced to a single (1.0±0.1) glycyl residue (FemA), cross-linking decreased by more than 20%, resulting in a high concentration of open N-terminus glycyl segments. PMID:19309106

Sharif, Shasad; Kim, Sung Joon; Labischinski, Harald; Schaefer, Jacob

2009-01-01

393

Solid state NMR spectroscopy in the evaluation of the conformational changes of humic substances as affected by thermal variations  

NASA Astrophysics Data System (ADS)

Soil organic matter (SOM) is an ubiquitous, complex material which is produced by the degradation of plant tissues and animal bodies. It is the major indicator of soil quality since it is directly involved in the maintenance of soil fertility, prevention of erosion and desert encroachment and provision of suitable environment for biological activity. Organic matter is an important driving force in environmental global change as it acts as both a source and sink of atmospheric carbon. However, SOM is subjected to rapid changes due to environmental transformations such as massive deforestations, fires, intensive land uses, temperature increases and so on. In the present work, a characterization of humic substances was done in order to obtain information about the transformation occurring to SOM as affected by temperature increases. For the first time variable temperature cross polarization magic angle spinning (CPMAS) 13C NMR spectroscopy was applied in combination with thermal analyses (TG and DSC) on environmentally relevant soil organic matter. The results show that the conformational changes occurring in humic substances as temperature is raised can be associated to melting of alkyl components connected with sublimation of some organic compounds. The simultaneous application of solid phase micro extraction GC-MS also allowed the identification of the components which were released by sublimation processes.

de Pasquale, C.; Berns, A. E.; Kucerik, J.; Conte, P.; Alonzo, G.

2009-04-01

394

Single bead detection with an NMR microcapillary probe  

NASA Astrophysics Data System (ADS)

We have developed a nuclear magnetic resonance (NMR) microcapillary probe for the detection of single magnetic microbeads. The geometry of the probe has been optimized so that the signal from the background water has a similar magnitude compared to the signal from the dephased water nearby a single magnetic bead within the probe detector coil. In addition, the RF field of the coil must be uniform within the effective range of the magnetic bead. Three different RF probes were tested in a 7 T (300 MHz) pulsed NMR spectrometer with sample volumes ranging from 5 nL down to 1 nL. The 1 nL probe had a single-shot signal-to-noise ratio (SNR) for pure water of 27 and a volume resolution that exhibits a 600-fold improvement over a conventional (5 mm tube) NMR probe with a sample volume of 18 ?L. This allowed for the detection of a 1 ?m magnetite/polystyrene bead (m = 2 × 10-14 A m2) with an estimated experimental SNR of 30. Simulations of the NMR spectra for the different coil geometries and positions of the bead within the coil were developed that include the B0 shift near a single bead, the inhomogeneity of the coils, the local coil sensitivity, the skin effect of the coil conductor, and quantitated estimates of the proximity effect between coil windings.

Nakashima, Yoshihiro; Boss, Michael; Russek, Stephen E.; Moreland, John

2012-11-01

395

Probing surface interactions by combining NMR cryoporometry and NMR relaxometry  

NASA Astrophysics Data System (ADS)

To further expand on the understanding of surface interactions at the liquid/solid interface on pore walls, the nuclear magnetic resonance (NMR) techniques of cryoporometry and relaxometry have been combined. The combination of these techniques allows variations in NMR relaxation parameters from pore surface to volume ratio changes and from surface interaction changes to be distinguished. By studying a range of sol-gel silicas from two different sources, it was noted that the relaxation time measurements were not consistent with the pore diameters determined by cryoporometry and N2 gas adsorption. Instead distinctly different relaxivity constants were determined for each absorbate in each of the two brands of silica. It was clear that the relaxation times were modified by more than just the pore geometry. Independent experiments on the two brands of silica suggested that the relaxometry results were heavily influenced by the concentration of paramagnetic relaxation centres in the silica gels. The strength of surface interaction, and hence surface affinity, was seen to depend on the liquid in the pores. Using this difference in surface affinities, binary mixtures of alkanes placed in sol-gel silicas were separated via preferential absorption and their components identified using cryoporometry, whereas the components could not be distinguished in the bulk liquid.

Mitchell, J.; Stark, S. C.; Strange, J. H.

2005-06-01

396

Control of the pump cycle in bacteriorhodopsin: mechanisms elucidated by solid-state NMR of the D85N mutant.  

PubMed Central

By varying the pH, the D85N mutant of bacteriorhodopsin provides models for several photocycle intermediates of the wild-type protein in which D85 is protonated. At pH 10.8, NMR spectra of [zeta-(15)N]lys-, [12-(13)C]retinal-, and [14,15-(13)C]retinal-labeled D85N samples indicate a deprotonated, 13-cis,15-anti chromophore. On the other hand, at neutral pH, the NMR spectra of D85N show a mixture of protonated Schiff base species similar to that seen in the wild-type protein at low pH, and more complex than the two-state mixture of 13-cis,15-syn, and all-trans isomers found in the dark-adapted wild-type protein. These results lead to several conclusions. First, the reversible titration of order in the D85N chromophore indicates that electrostatic interactions have a major influence on events in the active site. More specifically, whereas a straight chromophore is preferred when the Schiff base and residue 85 are oppositely charged, a bent chromophore is found when both the Schiff base and residue 85 are electrically neutral, even in the dark. Thus a "bent" binding pocket is formed without photoisomerization of the chromophore. On the other hand, when photoisomerization from the straight all-trans,15-anti configuration to the bent 13-cis,15-anti does occur, reciprocal thermodynamic linkage dictates that neutralization of the SB and D85 (by proton transfer from the former to the latter) will result. Second, the similarity between the chromophore chemical shifts in D85N at alkaline pH and those found previously in the M(n) intermediate of the wild-type protein indicate that the latter has a thoroughly relaxed chromophore like the subsequent N intermediate. By comparison, indications of L-like distortion are found for the chromophore of the M(o) state. Thus, chromophore strain is released in the M(o)-->M(n) transition, probably coincident with, and perhaps instrumental to, the change in the connectivity of the Schiff base from the extracellular side of the membrane to the cytoplasmic side. Because the nitrogen chemical shifts of the Schiff base indicate interaction with a hydrogen-bond donor in both M states, it is possible that a water molecule travels with the Schiff base as it switches connectivity. If so, the protein is acting as an inward-driven hydroxyl pump (analogous to halorhodopsin) rather than an outward-driven proton pump. Third, the presence of a significant C [double bond] N syn component in D85N at neutral pH suggests that rapid deprotonation of D85 is necessary at the end of the wild-type photocycle to avoid the generation of nonfunctional C [double bond] N syn species. PMID:11806941

Hatcher, Mary E; Hu, Jingui G; Belenky, Marina; Verdegem, Peter; Lugtenburg, Johan; Griffin, Robert G; Herzfeld, Judith

2002-01-01

397

Solid state {sup 1}H and {sup 13}C NMR structural investigation of a poly(ethylene oxide) hydrogel  

SciTech Connect

A cross-linked poly (ethylene oxide)/polyurethane hydrogel cross-linked with 1,2,6 hexane-triol and designated PEG4050/1HT [measured M{sup n} of 4050 for poly (ethylene oxide) glycol (PEG) and a mole ratio of 1:1 for the PEG to the 1,2,6 hexane-triol] has been characterized by high resolution {sup 1}H and {sup 13}C NMR. {sup 1}H thermal (T{sub 1}) and rotating frame (T{sub 1{rho}}) and {sup 13}CT{sub 1} relaxation times were determined for the powdered dry and swollen hydrogel with the standard variants of the cross-polarization pulse sequence which was used in conjunction with magic-angle spinning (MAS). The rotating frame relaxation measurements confirmed that crystalline and amorphous regions were present in the dry hydrogel but showed unabiguously that the crystalline regions are confined to the poly (ethylene oxide) chains, Upon hydration, there is a decrease in the cross polarization efficiency from the enhanced mobility by the poly (ethylene oxide) chains are affected to a much greater extent that the urethane and hexane segments, the characteristic time constant, T{sub CH} increasing by more than order of magnitude compared to no more than a factor of two for the latter. Clearly, the hydration involves hydrogen bonding between the water and principally the oxygens in the poly (ethylene oxide) chains. The {sup 1}H MAS spectra of the dry and hydrated samples confirmed that considerable averaging of the dipolar interactions occurs on hydration to give a well-resolved spectrum.

Badiger, M.V.; Graham, N.B.; Law, R.V.; Snape, C.E. [Univ. of Strathclyde, Glasgow (United Kingdom)

1993-12-31

398

Structure and Dynamics of the Myristoyl Lipid Modification of Src Peptides Determined by 2H Solid-State NMR Spectroscopy  

PubMed Central

Lipid modifications of proteins are widespread in nature and play an important role in numerous biological processes. The nonreceptor tyrosine kinase Src is equipped with an N-terminal myristoyl chain and a cluster of basic amino acids for the stable membrane association of the protein. We used 2H NMR spectroscopy to investigate the structure and dynamics of the myristoyl chain of myr-Src(2–19), and compare them with the hydrocarbon chains of the surrounding phospholipids in bilayers of varying surface potentials and chain lengths. The myristoyl chain of Src was well inserted in all bilayers investigated. In zwitterionic 1,2-dimyristoyl-sn-glycero-3-phosphocholine membranes, the myristoyl chain of Src was significantly longer and appears “stiffer” than the phospholipid chains. This can be explained by an equilibrium between the attraction attributable to the insertion of the myristoyl chain and the Born repulsion. In a 1,2-dimyristoyl-sn-glycero-3-phosphocholine/1,2-dimyristoyl-sn-glycero-3-[phospho-L-serine] membrane, where attractive electrostatic interactions come into play, the differences between the peptide and the phospholipid chain lengths were attenuated, and the molecular dynamics of all lipid chains were similar. In a much thicker 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/1,2-dipalmitoyl-sn-glycero-3-[phospho-L-serine]/cholesterol membrane, the length of the myristoyl chain of Src was elongated nearly to its maximum, and the order parameters of the Src chain were comparable to those of the surrounding membrane. PMID:19413971

Scheidt, Holger A.; Huster, Daniel

2009-01-01