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H.j.m. De Groot - One of the best experts on this subject based on the ideXlab platform.
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^13C−^1H heteronuclear Dipolar Correlation studies of the hydrogen bonding of the quinones inRhodobacter sphaeroides R26 reaction centers
Applied Magnetic Resonance, 2007Co-Authors: B. J. Rossum, W. B. S. Liemt, P. Gast, J. Lugtenburg, H.j.m. De GrootAbstract:The photosynthetic reaction center (RC) of the photosynthetic bacterium Rhodobacter sphaeroides R26 contains two quinones, Q_A and Q_B. Solid-state heteronuclear (^1H−^13C) Dipolar Correlation spectroscopy has been used to study the binding of the quinones in the ground state for RCs reconstituted with l-^13C ubiquinone-10. Lee-Goldburg cross-polarization buildup curves are recorded to determine distances r _CH between the l-^13C carbon labels and the protons involved in the polarization transfer. The l-^13C of both Q_A and Q_B have intermolecular Correlations with protons that resonate downfield, in the region of hydrogen-bonding protons. The distances between the carbon labels and the correlated protons are short, 0.21±0.01 nm. Hence the nuclear magnetic resonance provides evidence for strong hydrogen-bonding interactions at the l-C=O of both Q_A and Q_B for RCs in the ground state. The environment of the l-^13C of the Q_B is structurally heterogeneous compared to that of the Q_A. The data can be reconciled with a strong H-bonding interaction of the l-C=O of Q_A with Ala M260 NH, and with complex hydrogen bonding involving NH of Ile-L224 and of Gly-L225, and possibly the Ser-L223 hydroxyl group of the l-C=O of the Q_B, in the proximal site.
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13c 1h heteronuclear Dipolar Correlation studies of the hydrogen bonding of the quinones inrhodobacter sphaeroides r26 reaction centers
Applied Magnetic Resonance, 2007Co-Authors: B J Van Rossum, J. Lugtenburg, P. Gast, W B S Van Liemt, H.j.m. De GrootAbstract:The photosynthetic reaction center (RC) of the photosynthetic bacteriumRhodobacter sphaeroides R26 contains two quinones, QA and QB. Solid-state heteronuclear (1H−13C) Dipolar Correlation spectroscopy has been used to study the binding of the quinones in the ground state for RCs reconstituted with l-13C ubiquinone-10. Lee-Goldburg cross-polarization buildup curves are recorded to determine distancesr CH between the l-13C carbon labels and the protons involved in the polarization transfer. The l-13C of both QA and QB have intermolecular Correlations with protons that resonate downfield, in the region of hydrogen-bonding protons. The distances between the carbon labels and the correlated protons are short, 0.21±0.01 nm. Hence the nuclear magnetic resonance provides evidence for strong hydrogen-bonding interactions at the l-C=O of both QA and QB for RCs in the ground state. The environment of the l-13C of the QB is structurally heterogeneous compared to that of the QA. The data can be reconciled with a strong H-bonding interaction of the l-C=O of QA with Ala M260 NH, and with complex hydrogen bonding involving NH of Ile-L224 and of Gly-L225, and possibly the Ser-L223 hydroxyl group of the l-C=O of the QB, in the proximal site.
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A refined model of the chlorosomal antennae of the green bacterium Chlorobium tepidum from proton chemical shift constraints obtained with high-field 2-D and 3-D MAS NMR Dipolar Correlation spectroscopy.
Biochemistry, 2001Co-Authors: B J Van Rossum, G.j. Boender, A. R. Holzwarth, Kurt Schaffner, Dorte Bjerre Steensgaard, Fokko M. Mulder, H.j.m. De GrootAbstract:Heteronuclear 2-D and 3-D magic-angle spinning NMR Dipolar Correlation spectroscopy was applied to determine solid-state 1H shifts for aggregated bacteriochlorophyll c (BChl c) in uniformly 13C-enriched light harvesting chlorosomes of the green photosynthetic bacterium Chlorobium tepidum. A complete assignment of 29 different observable resonances of the 61 protons of the aggregated BChl c in the intact chlorosomes is obtained. Aggregation shifts relative to monomeric BChl c in solution are detected for protons attached to rings I, II, and III/V and to their side chains. The 21-H3, 32-H3, and 31-H resonances are shifted upfield by −2.2, −1, and −3.3 ppm, respectively, relative to monomeric BChl c in solution. Although the resonances are inhomogeneously broadened and reveal considerable global structural heterogeneity, the 5-CH and the 7-Me responses are doubled, which provides evidence for the existence of at least two relatively well-defined structurally different arrangements. Ab initio quantum chemical...
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Ultrahigh field MAS NMR Dipolar Correlation spectroscopy of the histidine residues in light-harvesting complex II from photosynthetic bacteria reveals partial internal charge transfer in the B850/His complex.
Journal of the American Chemical Society, 2001Co-Authors: J. M. Alia, Jan Raap, P. Gast, C. Soede-huijbregts, Marc Baldus, Johan Lugtenburg, H. J. Van Gorkom, Arnold J. Hoff, H.j.m. De GrootAbstract:Low-temperature 15N and 13C CP/MAS (cross-polarization/magic angle spinning) NMR has been used to analyze BChl-histidine interactions and the electronic structure of histidine residues in the light-harvesting complex II (LH2) of Rhodopseudomonas acidophila. The histidines were selectively labeled at both or one of the two nitrogen sites of the imidazole ring. The resonances of histidine nitrogens that are interacting with B850 BChl a have been assigned. Specific 15N labeling confirmed that it is the tau-nitrogen of histidines which is ligated to Mg2+ of B850 BChl molecules (beta-His30, alpha-His31). The pi-nitrogens of these Mg2+-bound histidines were found to be protonated and may be involved in hydrogen bond interactions. Comparison of the 2-D MAS NMR homonuclear (13C-13C) Dipolar Correlation spectrum of [13C6,15N3]-histidines in the LH2 complex with model systems in the solid state reveals two different classes of electronic structures from the histidines in the LH2. In terms of the 13C isotropic shifts, one corresponds to the neutral form of histidine and the other resembles a positively charged histidine species. 15N-13C double-CP/MAS NMR data provide evidence that the electronic structure of the histidines in the neutral BChl a/His complexes resembles the positive charge character form. While the Mg...15N isotropic shift confirms a partial positive charge transfer, its anisotropy is essentially of the lone pair type. This provides evidence that the hybridization structure corresponding to the neutral form of the imidazole is capable of "buffering" a significant amount of positive charge.
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Evidence from Solid State NMR Correlation Spectroscopy for two Interstack Arrangements in the Chlorosome Antenna System
Photosynthesis: Mechanisms and Effects, 1998Co-Authors: B J Van Rossum, Teodor Silviu Balaban, A. R. Holzwarth, Kurt Schaffner, Dorte Bjerre Steensgaard, B. Y. Van Duyl, H.j.m. De GrootAbstract:Solid state cross-polarization (CP) MAS NMR Dipolar Correlation spectroscopy is a rapidly growing technique that can provide structural information of systems that are inaccessible for X-ray diffraction techniques [1]. In particular, we have implemented Correlation spectroscopy to provide a concept for structure determination and to study the chromophore arrangement in antenna systems. Homonuclear (13C-13C) Dipolar Correlation spectroscopy was used to study the stacking of bacteriochlorophyll c (Bchl c) in uniformly 13C enriched [U-13C] intact chlorosomes from Chlorobium tepidum [2]. It was possible to arrive at a full assignment of the solid state NMR carbon chemical shifts, from which a model for the stack and interstack of Bchl c in the chlorosomes could be resolved [1-3].
Anthony Watts - One of the best experts on this subject based on the ideXlab platform.
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Assessing the effects of time and spatial averaging in ^15N chemical shift/^15N-^1H Dipolar Correlation solid state NMR experiments
Journal of Biomolecular NMR, 2003Co-Authors: Suzana K. Straus, Walter R.p. Scott, Anthony WattsAbstract:The effect of time and spatial averaging on ^15N chemical shift/^1H-^15N Dipolar Correlation spectra, i.e., PISEMA spectra, of α-helical membrane peptides and proteins is investigated. Three types of motion are considered: (a) Librational motion of the peptide planes in the α-helix; (b) rotation of the helix about its long axis; and (c) wobble of the helix about a nominal tilt angle. A 2ns molecular dynamics simulation of helix D of bacteriorhodopsin is used to determine the effect of librational motion on the spectral parameters. For the time averaging, the rotation and wobble of this same helix are modelled by assuming either Gaussian motion about the respective angles or a uniform distribution of a given width. For the spatial averaging, regions of possible ^15N chemical shift/^1H-^15N Dipolar splittings are computed for a distribution of rotations and/or tilt angles of the helix. The computed spectra show that under certain motional modes the ^15N chemical shift/^1H-^15N Dipolar pairs for each of the residues do not form patterns which mimic helical wheel patterns. As a result, the unambiguous identification of helix tilt and helix rotation without any resonance assignments or on the basis of a single assignment may be difficult.
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assessing the effects of time and spatial averaging in 15n chemical shift 15n 1h Dipolar Correlation solid state nmr experiments
Journal of Biomolecular NMR, 2003Co-Authors: Suzana K. Straus, Walter R.p. Scott, Anthony WattsAbstract:The effect of time and spatial averaging on 15 N chemical shift/ 1 H- 15 N Dipolar Correlation spectra, i.e., PISEMA spectra, of α-helical membrane peptides and proteins is investigated. Three types of motion are considered: (a) Librational motion of the peptide planes in the α-helix; (b) rotation of the helix about its long axis; and (c) wobble of the helix about a nominal tilt angle. A 2ns molecular dynamics simulation of helix D of bacteriorhodopsin is used to determine the effect of librational motion on the spectral parameters. For the time averaging, the rotation and wobble of this same helix are modelled by assuming either Gaussian motion about the respective angles or a uniform distribution of a given width. For the spatial averaging, regions of possible 15 N chemical shift/ 1 H- 15 N Dipolar splittings are computed for a distribution of rotations and/or tilt angles of the helix. The computed spectra show that under certain motional modes the 15 N chemical shift/ 1 H- 15 N Dipolar pairs for each of the residues do not form patterns which mimic helical wheel patterns. As a result, the unambiguous identification of helix tilt and helix rotation without any resonance assignments or on the basis of a single assignment may be difficult. Abbreviations: r.m.s. – root mean square; CSA – chemical shift anisotropy; D – Dipolar coupling; CS/D – 15 N chemical shift/ 15 N- 1 H Dipolar coupling; MD – molecular dynamics; d.o.f. degrees of freedom; PISA – polarisation index of the slant angle; PISEMA – polarisation inversion with spin exchange at the magic angle; c.o.m. – centre of mass.
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Assessing the effects of time and spatial averaging in 15N chemical shift/15N-1H Dipolar Correlation solid state NMR experiments.
Journal of Biomolecular NMR, 2003Co-Authors: Suzana K. Straus, Walter R.p. Scott, Anthony WattsAbstract:The effect of time and spatial averaging on 15 N chemical shift/ 1 H- 15 N Dipolar Correlation spectra, i.e., PISEMA spectra, of α-helical membrane peptides and proteins is investigated. Three types of motion are considered: (a) Librational motion of the peptide planes in the α-helix; (b) rotation of the helix about its long axis; and (c) wobble of the helix about a nominal tilt angle. A 2ns molecular dynamics simulation of helix D of bacteriorhodopsin is used to determine the effect of librational motion on the spectral parameters. For the time averaging, the rotation and wobble of this same helix are modelled by assuming either Gaussian motion about the respective angles or a uniform distribution of a given width. For the spatial averaging, regions of possible 15 N chemical shift/ 1 H- 15 N Dipolar splittings are computed for a distribution of rotations and/or tilt angles of the helix. The computed spectra show that under certain motional modes the 15 N chemical shift/ 1 H- 15 N Dipolar pairs for each of the residues do not form patterns which mimic helical wheel patterns. As a result, the unambiguous identification of helix tilt and helix rotation without any resonance assignments or on the basis of a single assignment may be difficult. Abbreviations: r.m.s. – root mean square; CSA – chemical shift anisotropy; D – Dipolar coupling; CS/D – 15 N chemical shift/ 15 N- 1 H Dipolar coupling; MD – molecular dynamics; d.o.f. degrees of freedom; PISA – polarisation index of the slant angle; PISEMA – polarisation inversion with spin exchange at the magic angle; c.o.m. – centre of mass.
Hartmut Oschkinat - One of the best experts on this subject based on the ideXlab platform.
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Determination of solid-state NMR structures of proteins by means of three-dimensional 15N-13C-13C Dipolar Correlation spectroscopy and chemical shift analysis.
Biochemistry, 2003Co-Authors: Federica Castellani, Barth-jan Van Rossum, Annette Diehl, Kristina Rehbein, Hartmut OschkinatAbstract:In this paper, a three-dimensional (3D) NMR-based approach for the determination of the fold of moderately sized proteins by solid-state magic-angle spinning (MAS) NMR is presented and applied to the α-spectrin SH3 domain. This methodology includes the measurement of multiple 13C−13C distance restraints on biosynthetically site-directed 13C-enriched samples, obtained by growing bacteria on [2-13C]glycerol and [1,3-13C]glycerol. 3D 15N−13C−13C Dipolar Correlation experiments were applied to resolve overlap of signals, in particular in the region where backbone carbon−carbon Correlations of the Cα−Cα, CO−CO, Cα−CO, and CO−Cα type appear. Additional restraints for confining the structure were obtained from φ and ψ backbone torsion angles of 29 residues derived from Cα, Cβ, CO, NH, and Hα chemical shifts. Using both distance and angular restraints, a refined structure was calculated with a backbone root-mean-square deviation of 0.7 A with respect to the average structure.
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A 3-D Structural Model of Solid Self-Assembled Chlorophyll a/H2O from Multispin Labeling and MAS NMR 2-D Dipolar Correlation Spectroscopy in High Magnetic Field
Journal of Magnetic Resonance, 2002Co-Authors: Barth Van Rossum, Jan Raap, Hartmut Oschkinat, Els A. M. Schulten, Huub J. M. De GrootAbstract:Abstract Magic angle spinning (MAS) NMR with Lee–Goldburg cross-polarization (LG-CP) is used to promote long-range heteronuclear transfer of magnetization and to constrain a structural model for uniformly labeled chlorophyll a/H2O. An effective maximum transfer range dmax can be determined experimentally from the detection of a gradually decreasing series of intramolecular Correlations with the 13C along the molecular skeleton. To probe intermolecular contacts, dmax can be set to ∼4.2 A by choosing an LG-CP contact time of 2 ms. Long-range 1H–13C Correlations are used in conjunction with carbon and proton aggregation shifts to establish the stacking of the chlorophyll a (Chl a) molecules. First, high-field (14.1 T) 2-D MAS NMR homonuclear (13C–13C) Dipolar Correlation spectra provide a complete assignment of the carbon chemical shifts. Second, proton chemical shifts are obtained from 1H–13C heteronuclear Dipolar Correlation spectroscopy in high magnetic field. The shift constraints and long-range 1H–13C intermolecular Correlations reveal a 2-D stacking homologous to the molecular arrangement in crystalline solid ethyl-chlorophyllide a. A doubling of a small subset of the carbon resonances, in the 7-methyl region of the molecule, provides evidence for two marginally different well-defined molecular environments. Evidence is found for the presence of neutral structural water molecules forming a hydrogen-bonded network to stabilize Chl a sheets. In line with the microcrystalline order observed for the rings, the long T1's, and absence of conformational shifts for the 13C in the phytyl tails, it is proposed that the Chl a form a rigid 3-D space-filling structure. Probably the only way this can be realized with the sheets is by forming bilayers with interpenetration of elongated tails. Such a 3-D space-filling organization of the aggregated Chl a from MAS NMR would match existing models inferred from electron microscopy and low-resolution X-ray powder diffraction, while a micellar model based on neutron diffraction and antiparallel stacking observed in solution can be discarded.
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backbone and side chain 13c and 15n signal assignments of the α spectrin sh3 domain by magic angle spinning solid state nmr at 17 6 tesla
ChemBioChem, 2001Co-Authors: Jutta Pauli, Marc Baldus, Huub J. M. De Groot, Barth Van Rossum, Hartmut OschkinatAbstract:The backbone and side-chain 13C and 15N signals of a solid 62-residue (u-13C,15N)-labelled protein containing the α-spectrin SH3 domain were assigned by two-dimensional (2D) magic angle spinning (MAS) 15N–13C and 13C–13C Dipolar Correlation spectroscopy at 17.6 T. The side-chain signal sets of the individual amino acids were identified by 2D 13C–13C proton-driven spin diffusion and Dipolar recoupling experiments. Correlations to the respective backbone nitrogen signals were established by 2D NCACX (CX=any carbon atom) experiments, which contain a proton–nitrogen and a nitrogen–carbon cross-polarisation step followed by a carbon–carbon homonuclear transfer unit. Interresidue Correlations leading to sequence-specific assignments were obtained from 2D NCOCX experiments. The assignment is nearly complete for the SH3 domain residues 7–61, while the signals of the N- and C-terminal residues 1–6 and 62, respectively, outside the domain boundaries are not detected in our MAS spectra. The resolution observed in these spectra raises expectations that receptor-bound protein ligands and slightly larger proteins (up to 20 kDa) can be readily assigned in the near future by using three-dimensional versions of the applied or analogous techniques.
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MAS NMR Dipolar Correlation Spectroscopy of Partially Deuterated13C- Labelled Chlorophyll a
Photosynthesis: Mechanisms and Effects, 1998Co-Authors: Els A. M. Schulten, Jan Raap, B J Van Rossum, Hartmut Oschkinat, J. Ashurst, H.j.m. De GrootAbstract:Chlorophyll (Fig. 1) is a major constituent of photosynthetic complexes. 1H MAS NMR can provide important information about the electronic and spatial structure of chlorophyll in photosynthetic studies. However, the observation of the 1H response in solid-type samples is difficult. The proton resolution in solid state NMR is usually insufficient for direct observation, due the combination of strong homonuclear couplings between protons and a small chemical shift dispersion. To circumvent this problem, 2D and 3D heteronuclear spectroscopy has been applied, and the signals from up to ~ 50 protons in a moderately sized multispin cluster have been assigned [1, 21. In these assignment studies, a high field wideline separation (WISE) and a combination of high field and homonuclear frequency-switched Lee-Goldburg (FSLG) 1H decoupling were applied to resolve the proton response. Here we investigate if additional resolution improvement can be obtained by a suppression of 1H homonuclear Dipolar couplings by dilution of the protons with deuterons. It can be stated a priori that dilution has the disadvantage that the overall 1H response is weakened, which will inevitably affect the range of the 1H MAS NMR. The dilution increases the transverse relaxation time and blocks the spin diffusion. Despite of the reduction of the sensitivity, it is important to asses the effect of 2H dilution in high magnetic field, with and without FSLG decoupling. We have chosen to use a moderate dilution level of 75% 2H, reducing the 1H signal strength by a factor of four.
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mas nmr Dipolar Correlation spectroscopy of partially deuterated 13c labelled chlorophyll a
1998Co-Authors: Els A. M. Schulten, Jan Raap, B J Van Rossum, Hartmut Oschkinat, J. Ashurst, H.j.m. De GrootAbstract:Chlorophyll (Fig. 1) is a major constituent of photosynthetic complexes. 1H MAS NMR can provide important information about the electronic and spatial structure of chlorophyll in photosynthetic studies. However, the observation of the 1H response in solid-type samples is difficult. The proton resolution in solid state NMR is usually insufficient for direct observation, due the combination of strong homonuclear couplings between protons and a small chemical shift dispersion. To circumvent this problem, 2D and 3D heteronuclear spectroscopy has been applied, and the signals from up to ~ 50 protons in a moderately sized multispin cluster have been assigned [1, 21. In these assignment studies, a high field wideline separation (WISE) and a combination of high field and homonuclear frequency-switched Lee-Goldburg (FSLG) 1H decoupling were applied to resolve the proton response. Here we investigate if additional resolution improvement can be obtained by a suppression of 1H homonuclear Dipolar couplings by dilution of the protons with deuterons. It can be stated a priori that dilution has the disadvantage that the overall 1H response is weakened, which will inevitably affect the range of the 1H MAS NMR. The dilution increases the transverse relaxation time and blocks the spin diffusion. Despite of the reduction of the sensitivity, it is important to asses the effect of 2H dilution in high magnetic field, with and without FSLG decoupling. We have chosen to use a moderate dilution level of 75% 2H, reducing the 1H signal strength by a factor of four.
Suzana K. Straus - One of the best experts on this subject based on the ideXlab platform.
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Assessing the effects of time and spatial averaging in ^15N chemical shift/^15N-^1H Dipolar Correlation solid state NMR experiments
Journal of Biomolecular NMR, 2003Co-Authors: Suzana K. Straus, Walter R.p. Scott, Anthony WattsAbstract:The effect of time and spatial averaging on ^15N chemical shift/^1H-^15N Dipolar Correlation spectra, i.e., PISEMA spectra, of α-helical membrane peptides and proteins is investigated. Three types of motion are considered: (a) Librational motion of the peptide planes in the α-helix; (b) rotation of the helix about its long axis; and (c) wobble of the helix about a nominal tilt angle. A 2ns molecular dynamics simulation of helix D of bacteriorhodopsin is used to determine the effect of librational motion on the spectral parameters. For the time averaging, the rotation and wobble of this same helix are modelled by assuming either Gaussian motion about the respective angles or a uniform distribution of a given width. For the spatial averaging, regions of possible ^15N chemical shift/^1H-^15N Dipolar splittings are computed for a distribution of rotations and/or tilt angles of the helix. The computed spectra show that under certain motional modes the ^15N chemical shift/^1H-^15N Dipolar pairs for each of the residues do not form patterns which mimic helical wheel patterns. As a result, the unambiguous identification of helix tilt and helix rotation without any resonance assignments or on the basis of a single assignment may be difficult.
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assessing the effects of time and spatial averaging in 15n chemical shift 15n 1h Dipolar Correlation solid state nmr experiments
Journal of Biomolecular NMR, 2003Co-Authors: Suzana K. Straus, Walter R.p. Scott, Anthony WattsAbstract:The effect of time and spatial averaging on 15 N chemical shift/ 1 H- 15 N Dipolar Correlation spectra, i.e., PISEMA spectra, of α-helical membrane peptides and proteins is investigated. Three types of motion are considered: (a) Librational motion of the peptide planes in the α-helix; (b) rotation of the helix about its long axis; and (c) wobble of the helix about a nominal tilt angle. A 2ns molecular dynamics simulation of helix D of bacteriorhodopsin is used to determine the effect of librational motion on the spectral parameters. For the time averaging, the rotation and wobble of this same helix are modelled by assuming either Gaussian motion about the respective angles or a uniform distribution of a given width. For the spatial averaging, regions of possible 15 N chemical shift/ 1 H- 15 N Dipolar splittings are computed for a distribution of rotations and/or tilt angles of the helix. The computed spectra show that under certain motional modes the 15 N chemical shift/ 1 H- 15 N Dipolar pairs for each of the residues do not form patterns which mimic helical wheel patterns. As a result, the unambiguous identification of helix tilt and helix rotation without any resonance assignments or on the basis of a single assignment may be difficult. Abbreviations: r.m.s. – root mean square; CSA – chemical shift anisotropy; D – Dipolar coupling; CS/D – 15 N chemical shift/ 15 N- 1 H Dipolar coupling; MD – molecular dynamics; d.o.f. degrees of freedom; PISA – polarisation index of the slant angle; PISEMA – polarisation inversion with spin exchange at the magic angle; c.o.m. – centre of mass.
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Assessing the effects of time and spatial averaging in 15N chemical shift/15N-1H Dipolar Correlation solid state NMR experiments.
Journal of Biomolecular NMR, 2003Co-Authors: Suzana K. Straus, Walter R.p. Scott, Anthony WattsAbstract:The effect of time and spatial averaging on 15 N chemical shift/ 1 H- 15 N Dipolar Correlation spectra, i.e., PISEMA spectra, of α-helical membrane peptides and proteins is investigated. Three types of motion are considered: (a) Librational motion of the peptide planes in the α-helix; (b) rotation of the helix about its long axis; and (c) wobble of the helix about a nominal tilt angle. A 2ns molecular dynamics simulation of helix D of bacteriorhodopsin is used to determine the effect of librational motion on the spectral parameters. For the time averaging, the rotation and wobble of this same helix are modelled by assuming either Gaussian motion about the respective angles or a uniform distribution of a given width. For the spatial averaging, regions of possible 15 N chemical shift/ 1 H- 15 N Dipolar splittings are computed for a distribution of rotations and/or tilt angles of the helix. The computed spectra show that under certain motional modes the 15 N chemical shift/ 1 H- 15 N Dipolar pairs for each of the residues do not form patterns which mimic helical wheel patterns. As a result, the unambiguous identification of helix tilt and helix rotation without any resonance assignments or on the basis of a single assignment may be difficult. Abbreviations: r.m.s. – root mean square; CSA – chemical shift anisotropy; D – Dipolar coupling; CS/D – 15 N chemical shift/ 15 N- 1 H Dipolar coupling; MD – molecular dynamics; d.o.f. degrees of freedom; PISA – polarisation index of the slant angle; PISEMA – polarisation inversion with spin exchange at the magic angle; c.o.m. – centre of mass.
Ingo Schnell - One of the best experts on this subject based on the ideXlab platform.
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^2H Chemical-shift resolution and Dipolar^2H-^1H,^2H-^15N Correlations in solid-state MAS NMR spectroscopy for structure determination and distance measurements in hydrogen-bonded systems
Central European Journal of Chemistry, 2005Co-Authors: Martin Schulz-dobrick, Ingo SchnellAbstract:In solid-state NMR, deuteron (^2H) spectroscopy can be performed in full analogy to^1H spectroscopy, including^2H chemical-shift resolution and^2H-X Dipolar Correlation schemes, when the NMR experiments are conducted in a “rotor-synchronized” fashion under fast magic-angle spinning. Here, 2H-X NMR experiments of this type, including^2H-^15N and^2H-^1H chemical-shift Correlations and distance measurements, are introduced and demonstrated on cytosine monohydrate, whose acidic protons can readily be replaced by deuterons by recrystallization from D_2O. In this way,^2H NMR spectroscopy provides information complementary to^1H NMR data, which is particularly useful for studying hydrogen bonds in supra- or biomolecular systems.
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2h chemical shift resolution and Dipolar2h 1h 2h 15n Correlations in solid state mas nmr spectroscopy for structure determination and distance measurements in hydrogen bonded systems
Central European Journal of Chemistry, 2005Co-Authors: Martin Schulzdobrick, Ingo SchnellAbstract:In solid-state NMR, deuteron (2H) spectroscopy can be performed in full analogy to1H spectroscopy, including2H chemical-shift resolution and2H-X Dipolar Correlation schemes, when the NMR experiments are conducted in a “rotor-synchronized” fashion under fast magic-angle spinning. Here, 2H-X NMR experiments of this type, including2H-15N and2H-1H chemical-shift Correlations and distance measurements, are introduced and demonstrated on cytosine monohydrate, whose acidic protons can readily be replaced by deuterons by recrystallization from D2O. In this way,2H NMR spectroscopy provides information complementary to1H NMR data, which is particularly useful for studying hydrogen bonds in supra- or biomolecular systems.
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redor based heteronuclear Dipolar Correlation experiments in multi spin systems rotor encoding directing and multiple distance and angle determination
Solid State Nuclear Magnetic Resonance, 2002Co-Authors: Kay Saalwächter, Ingo SchnellAbstract:Abstract We review a variety of recently developed 1 H–X heteronuclear recoupling techniques, which rely only on the homonuclear decoupling efficiency of very-fast magic-angle spinning. All these techniques, which are based on the simple rotational-echo, double-resonance (REDOR) approach for heteronuclear recoupling, are presented in a common context. Advantages and possibilities with respect to the complementary application of conventionally X and 1 H-inversely detected variants are discussed in relation to the separability and analysis of multiple couplings. We present an improved and more sensitive approach to the determination of 1 H–X Dipolar couplings by spinning-sideband analysis, termed REREDOR, which is applicable to XH n groups in rigid and mobile systems and bears some similarity to more elaborate separated local-field methods. The estimation of medium-range 1 H–X distances by analyzing signal intensities in two-dimensional REDOR Correlation spectra in a model-free way is also discussed. More specifically, we demonstrate the possibility of combined distance and angle determination in H–X–H or X–H–X three-spin systems by asymmetric recoupling schemes and spinning-sideband analysis. Finally, an 1 H–X Correlation experiment is introduced which accomplishes high sensitivity by inverse 1 H) detection and is therefore applicable to samples with 15 N in natural abundance.