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Bučar DK, Day GM, Halasz I, Zhang GGZ, Sander JRG, Reid DG, MacGillivray LR, Duer MJ, Jones W. The curious case of (caffeine)·(benzoic acid): how heteronuclear seeding allowed the formation of an elusive cocrystal. Chem Sci 2013. [DOI: 10.1039/c3sc51419f] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Davies E, Duer MJ, Ashbrook SE, Griffin JM. Applications of NMR crystallography to problems in biomineralization: refinement of the crystal structure and 31P solid-state NMR spectral assignment of octacalcium phosphate. J Am Chem Soc 2012; 134:12508-15. [PMID: 22746195 DOI: 10.1021/ja3017544] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
By combining X-ray crystallography, first-principles density functional theory calculations, and solid-state nuclear magnetic resonance spectroscopy, we have refined the crystal structure of octacalcium phosphate (OCP), reassigned its (31)P NMR spectrum, and identified an extended hydrogen-bonding network that we propose is critical to the structural stability of OCP. Analogous water networks may be related to the critical role of the hydration state in determining the mechanical properties of bone, as OCP has long been proposed as a precursor phase in bone mineral formation. The approach that we have taken in this paper is broadly applicable to the characterization of crystalline materials in general, but particularly to those incorporating hydrogen that cannot be fully characterized using diffraction techniques.
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Reid DG, Shanahan CM, Duer MJ, Arroyo LG, Schoppet M, Brooks RA, Murray RC. Lipids in biocalcification: contrasts and similarities between intimal and medial vascular calcification and bone by NMR. J Lipid Res 2012; 53:1569-75. [PMID: 22651923 DOI: 10.1194/jlr.m026088] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pathomechanisms underlying vascular calcification biogenesis are still incompletely understood. Biomineral from human atherosclerotic intimal plaques; human, equine, and bovine medial vascular calcifications; and human and equine bone was released from collagenous organic matrix by sodium hydroxide/sodium hypochlorite digestion. Solid-state (13)C NMR of intimal plaque mineral shows signals from cholesterol/cholesteryl esters and fatty acids. In contrast, in mineral from pure medial calcifications and bone mineral, fatty acid signals predominate. Refluxing (chloroform/methanol) intimal plaque calcifications removes the cholesterylic but not the fatty acyl signals. The lipid composition of this refluxed mineral now closely resembles that of the medial and bone mineral, which is unchanged by reflux. Thus, intimal and medial vascular calcifications and bone mineral have in common a pool of occluded mineral-entrained fatty acyl-rich lipids. This population of fatty acid may contain methyl-branched fatty acids, possibly representing lipoprotein particle remnants. Cell signaling and mechanistic parallels between physiological (orthotopic) and pathological (ectopic) calcification are also reflected thus in the NMR spectroscopic fingerprints of mineral-associated and mineral-entrained lipids. Additionally the atherosclerotic plaque mineral alone shows a significant independent pool of cholesterylic lipids. Colocalization of mineral and lipid may be coincidental, but it could also reflect an essential mechanistic component of biomineralization.
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Reid DG, Mason MJ, Chan BKK, Duer MJ. Characterization of the phosphatic mineral of the barnacle Ibla cumingi at atomic level by solid-state nuclear magnetic resonance: comparison with other phosphatic biominerals. J R Soc Interface 2012; 9:1510-6. [PMID: 22298816 DOI: 10.1098/rsif.2011.0895] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Ibliform barnacles are among the few invertebrate animals harnessing calcium phosphate to construct hard tissue. The (31)P solid-state NMR (SSNMR) signal from the shell plates of Ibla cumingi (Iblidae) is broader than that of bone, and shifted by ca 1 ppm to low frequency. (1)H-(31)P heteronuclear correlation (HETCOR) experiments show a continuum of different phosphorus/phosphate atomic environments, close to hydrogen populations with resonance frequencies between ca 10 and 20 ppm. Associated (1)H and (31)P chemical shifts argue the coexistence of weakly (high (31)P frequency, low (1)H frequency) to more strongly (lower (31)P frequency, higher (1)H frequency) hydrogen-bonded hydrogen phosphate-like molecular/ionic species. There is no resolved signal from discrete OH(-) ions. (13)C SSNMR shows chitin, protein and other organic biomolecules but, unlike bone, there are no significant atomic scale organic matrix-mineral contacts. The poorly ordered hydrogen phosphate-like iblid mineral is strikingly different, structurally and compositionally, from both vertebrate bone mineral and the more crystalline fluoroapatite of the linguliform brachiopods. It probably represents a previously poorly characterized calcium phosphate biomineral, the evolution of which may have reflected either the chemical conditions of ancestral seas or the mechanical advantages of phosphatic biomineralization over a calcium carbonate equivalent.
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Chow WY, Taylor AM, Reid DG, Gallagher JA, Duer MJ. Collagen atomic scale molecular disorder in ochronotic cartilage from an alkaptonuria patient, observed by solid state NMR. J Inherit Metab Dis 2011; 34:1137-40. [PMID: 21735270 DOI: 10.1007/s10545-011-9373-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 06/16/2011] [Accepted: 06/21/2011] [Indexed: 10/18/2022]
Abstract
UNLABELLED In pilot studies of the usefulness of solid state nuclear magnetic resonance spectroscopy in characterizing chemical and molecular structural effects of alkaptonuria on connective tissue, we have obtained (13) C spectra from articular cartilage from an AKU patient. An apparently normal anatomical location yielded a cross polarization magic angle spinning spectrum resembling literature spectra and dominated by collagen and glycosaminoglycan signals. All spectral linewidths from strongly pigmented ochronotic cartilage however were considerably increased relative to the control indicating a marked increase in collagen molecular disorder. This disordering of cartilage structural protein parallels, at the atomic level, the disordering revealed at higher length scales by microscopy. We also demonstrate that the abnormal spectra from ochronotic cartilage fit with the abnormality in the structure of collagen fibres at the ultrastructural level, whereby large ochronotic deposits appear to alter the structure of the collagen fibre by invasion and cross linking. SUMMARY Increased signal linewidths in solid state NMR spectra of ochronotic articular cartilage from an AKU patient relative to linewidths in normal, control, cartilage reveals a marked decrease in collagen molecular order in the diseased tissue. This atomic level disordering parallels higher length scale disorder revealed by microscopic techniques.
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André V, Hardeman A, Halasz I, Stein RS, Jackson GJ, Reid DG, Duer MJ, Curfs C, Duarte MT, Friščić T. Mechanosynthesis of the metallodrug bismuth subsalicylate from Bi2O3 and structure of bismuth salicylate without auxiliary organic ligands. Angew Chem Int Ed Engl 2011; 50:7858-61. [PMID: 21739550 DOI: 10.1002/anie.201103171] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Revised: 05/24/2011] [Indexed: 11/09/2022]
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Reid DG, Jackson GJ, Duer MJ, Rodgers AL. Apatite in kidney stones is a molecular composite with glycosaminoglycans and proteins: evidence from nuclear magnetic resonance spectroscopy, and relevance to Randall's plaque, pathogenesis and prophylaxis. J Urol 2010; 185:725-30. [PMID: 21168873 DOI: 10.1016/j.juro.2010.09.075] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Indexed: 11/26/2022]
Abstract
PURPOSE We characterized the biomacromolecular composition of phosphatic urinary stones using solid state nuclear magnetic resonance spectroscopy. We identified possible parallels between the nature of the organic matrix-mineral interface in stones and that in other mineralized tissue using nuclear magnetic resonance spectroscopy rotational echo double resonance. MATERIALS AND METHODS We analyzed 28 phosphatic (apatite and mixed apatite-struvite) surgically removed stones by nuclear magnetic resonance spectroscopy using (31)P, (13)C and a 9.4 Tesla magnetic field. Ten samples had sufficient signal from biomacromolecular organic material to characterize the mineral/organic interface by (13)C{(31)P} rotational echo double resonance. RESULTS Biomacromolecular organic material was most abundant in phosphatic stones in which apatite predominated. Nuclear magnetic resonance spectroscopy detected variable proportions of protein, glycosaminoglycan, lipid and carbonate. Rotational echo double resonance revealed strong interaction between mineral and glycosaminoglycan molecules, and to a lesser extent protein molecules, on the sub-nm length scale, implying that glycosaminoglycan and protein are composited into or onto the mineral lattice by strong physicochemical interactions. Carbonate ions substituted into apatite crystal lattices also showed the expected strong (13)C{(31)P} rotational echo double resonance effects. Conversely when present, lipid, calcium oxalate hydrates and uric acid showed no rotational echo double resonance effects, proving that they exist as deposits or crystals distinct from phosphatic mineral/biomacromolecular composites. CONCLUSIONS The intimate coexistence of biomacromolecules, especially glycosaminoglycan, with apatite in phosphatic stones supports the notion that they may have a key role in stone pathogenesis. The underlying intermolecular relationships may reflect those governing the formation of Randall's plaque in nascent stones.
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Neary MT, Reid DG, Mason MJ, Friscic T, Duer MJ, Cusack M. Contrasts between organic participation in apatite biomineralization in brachiopod shell and vertebrate bone identified by nuclear magnetic resonance spectroscopy. J R Soc Interface 2010; 8:282-8. [PMID: 20610423 DOI: 10.1098/rsif.2010.0238] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Unusually for invertebrates, linguliform brachiopods employ calcium phosphate mineral in hard tissue formation, in common with the evolutionarily distant vertebrates. Using solid-state nuclear magnetic resonance spectroscopy (SSNMR) and X-ray powder diffraction, we compare the organic constitution, crystallinity and organic matrix-mineral interface of phosphatic brachiopod shells with those of vertebrate bone. In particular, the organic-mineral interfaces crucial for the stability and properties of biomineral were probed with SSNMR rotational echo double resonance (REDOR). Lingula anatina and Discinisca tenuis shell materials yield strikingly dissimilar SSNMR spectra, arguing for quite different organic constitutions. However, their fluoroapatite-like mineral is highly crystalline, unlike the poorly ordered hydroxyapatite of bone. Neither shell material shows (13)C{(31)P} REDOR effects, excluding strong physico-chemical interactions between mineral and organic matrix, unlike bone in which glycosaminoglycans and proteins are composited with mineral at sub-nanometre length scales. Differences between organic matrix of shell material from L. anatina and D. tenuis, and bone reflect evolutionary pressures from contrasting habitats and structural purposes. The absence of organic-mineral intermolecular associations in brachiopod shell argues that biomineralization follows different mechanistic pathways to bone; their details hold clues to the molecular structural evolution of phosphatic biominerals, and may provide insights into novel composite design.
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Ironside MS, Duer MJ, Reid DG, Byard S. Bisphosphonate protonation states, conformations, and dynamics on bone mineral probed by solid-state NMR without isotope enrichment. Eur J Pharm Biopharm 2010; 76:120-6. [PMID: 20554022 DOI: 10.1016/j.ejpb.2010.05.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2010] [Revised: 04/13/2010] [Accepted: 05/25/2010] [Indexed: 11/26/2022]
Abstract
Recognition of bone mineral by bisphosphonates is crucial to their targeting, efficacy, therapeutic and diagnostic applications, and pharmacokinetics. In a search for rapid and simple NMR approaches to assessing the bone recognition characteristics of bisphosphonates, we have studied alendronate, pamidronate, neridronate, zoledronate and tiludronate, in crystalline form and bound to the surface of pure bone mineral stripped of its organic matrix by a simple chemical process. (31)P NMR chemical shift anisotropies and asymmetries in the crystalline compounds cluster strongly into groupings corresponding to fully protonated, monoprotonated, and deprotonated phosphonate states. All the mineral-bound bisphosphonates cluster in the same anisotropy-asymmetry space as the deprotonated phosphonates. In (13)C{(31)P} rotational echo double resonance (REDOR) experiments, which are sensitive to carbon-phosphorus interatomic distances, the strongly mineral-bound alendronate displays very similar conformational and side chain dynamics to its crystalline state. Pamidronate and neridronate, with shorter and longer sidechains, respectively, and generally weaker mineral binding, display more dynamical sidechains in the mineral-bound state. The REDOR experiment provides a simple rationalization of bisphosphonate-mineral affinity in terms of molecular structure and dynamics, consistent with findings from much more labour- and time-intensive isotope labelling approaches.
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Štrukil V, Fábián L, Reid DG, Duer MJ, Jackson GJ, Eckert-Maksić M, Friščić T. Towards an environmentally-friendly laboratory: dimensionality and reactivity in the mechanosynthesis of metal–organic compounds. Chem Commun (Camb) 2010; 46:9191-3. [DOI: 10.1039/c0cc03822a] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Laurencin D, Wong A, Chrzanowski W, Knowles JC, Qiu D, Pickup DM, Newport RJ, Gan Z, Duer MJ, Smith ME. Probing the calcium and sodium local environment in bones and teeth using multinuclear solid state NMR and X-ray absorption spectroscopy. Phys Chem Chem Phys 2010; 12:1081-91. [DOI: 10.1039/b915708e] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Duer MJ, Friscić T, Murray RC, Reid DG, Wise ER. The mineral phase of calcified cartilage: its molecular structure and interface with the organic matrix. Biophys J 2009; 96:3372-8. [PMID: 19383480 DOI: 10.1016/j.bpj.2008.12.3954] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2008] [Revised: 11/19/2008] [Accepted: 12/15/2008] [Indexed: 10/20/2022] Open
Abstract
We have studied the atomic level structure of mineralized articular cartilage with heteronuclear solid-state NMR, our aims being to identify the inorganic species present at the surfaces of the mineral crystals which may interact with the surrounding organic matrix and to determine which components of the organic matrix are most closely involved with the mineral crystals. One-dimensional (1)H and (31)P and two-dimensional (1)H-(31)P heteronuclear correlation NMR experiments show that the mineral component is very similar to that in bone with regard to its surface structure. (13)C{(31)P} rotational echo double resonance experiments identify the organic molecules at the mineral surface as glycosaminoglycans, which concurs with our recent finding in bone. There is also evidence of gamma-carboxyglutamic acid residues interacting with the mineral. However, other matrix components appear more distant from the mineral compared with bone. This may be due to a larger hydration layer on the mineral crystal surfaces in calcified cartilage.
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Ironside MS, Reid DG, Duer MJ. Correlating sideband patterns with powder patterns for accurate determination of chemical shift parameters in solid-state NMR. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2008; 46:913-917. [PMID: 18666220 DOI: 10.1002/mrc.2262] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Powder patterns and sideband patterns have different strengths when it comes to using them to determine chemical shift parameters. Here, we show that chemical shift parameters can be determined with high accuracy by analysing the correlation pattern from a 2D experiment which correlates a powder pattern in the indirect dimension with a sideband pattern in the direct dimension. The chemical shift parameters so determined have greater accuracy than those obtained by analysing a sideband or powder pattern alone, for the same signal-to-noise ratio. This method can be applied for both resolved correlation patterns and to cases where two components share similar isotropic chemical shifts. The methodology is demonstrated in this paper, both theoretically and experimentally, on the (31)P signals of the bis-phosphonate drug, pamidronate.
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Duer MJ, Friscić T, Proudfoot D, Reid DG, Schoppet M, Shanahan CM, Skepper JN, Wise ER. Mineral surface in calcified plaque is like that of bone: further evidence for regulated mineralization. Arterioscler Thromb Vasc Biol 2008; 28:2030-4. [PMID: 18703777 DOI: 10.1161/atvbaha.108.172387] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
OBJECTIVE Cell biological studies demonstrate remarkable similarities between mineralization processes in bone and vasculature, but knowledge of the components acting to initiate mineralization in atherosclerosis is limited. The molecular level microenvironment at the organic-inorganic interface holds a record of the mechanisms controlling mineral nucleation. This study was undertaken to compare the poorly understood interface in mineralized plaque with that of bone, which is considerably better characterized. METHODS AND RESULTS Solid state nuclear magnetic resonance (SSNMR) spectroscopy provides powerful tools for studying the organic-inorganic interface in calcium phosphate biominerals. The rotational echo double resonance (REDOR) technique, applied to calcified human plaque, shows that this interface predominantly comprises sugars, most likely glycosaminoglycans (GAGs). In this respect, and in the pattern of secondary effects seen to protein (mainly collagen), calcified plaque strongly resembles bone. CONCLUSIONS The similarity between biomineral formed under highly controlled (bone) and pathological (plaque) conditions suggests that the control mechanisms are more similar than previously thought, and may be adaptive. It is strong further evidence for regulation of plaque mineralization by osteo/chondrocytic vascular smooth muscle cells.
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Best SM, Duer MJ, Reid DG, Wise ER, Zou S. Towards a model of the mineral-organic interface in bone: NMR of the structure of synthetic glycosaminoglycan- and polyaspartate-calcium phosphate composites. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2008; 46:323-329. [PMID: 18306171 DOI: 10.1002/mrc.2168] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We have synthesised three materials-chondroitin sulphate (ChS, a commercial product derived from shark cartilage and predominantly chondroitin-6-sulphate (Ch-6-S)) bound to pre-formed hydroxyapatite (HA, Ca(10)(PO(4))(6)(OH)(2)), HA formed in the presence of ChS and poly-Asp bound to pre-formed HA-to generate models for the mineral-organic interface in bone. The three materials have been investigated by (13)C cross polarisation magic-angle spinning (CPMAS) NMR, (13)C{(31)P} rotational echo double resonance (REDOR) and powder x-ray diffraction (XRD) in order to verify their composition and to determine the nature of their binding to HA. Our results show that for HA formed in the presence of Ch-6-S, all carbon atoms in the Ch-6-S having contact with mineral phosphate. We propose that HA in this case forms all around the Ch-6-S polymer rather than along one face of it as is more commonly supposed in cases of templating by organic molecules. However, Ch-6-S binding to pre-formed HA probably occurs via a surface layer of water on the mineral rather than to the mineral directly. In contrast, poly-Asp binds closely to the pre-formed HA surface and so is clearly able to displace at least some of the surface-bound water.
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Friscić T, Fábián L, Burley JC, Reid DG, Duer MJ, Jones W. Exploring the relationship between cocrystal stability and symmetry: is Wallach's rule applicable to multi-component solids? Chem Commun (Camb) 2008:1644-6. [PMID: 18368151 DOI: 10.1039/b717532a] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Comparison of structure and hydration stability of pairs of chiral and racemic binary cocrystals indicates that the racemic solid is more stable than the chiral one; we illustrate that this difference might arise from intermolecular (crystal packing) factors in one case, while intramolecular (molecular conformation) factors are more significant in the other.
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Ironside MS, Stein RS, Duer MJ. Using chemical shift anisotropy to resolve isotropic signals in solid-state NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2007; 188:49-55. [PMID: 17606395 DOI: 10.1016/j.jmr.2007.06.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2007] [Revised: 06/06/2007] [Accepted: 06/07/2007] [Indexed: 05/16/2023]
Abstract
A key problem in solid-state NMR is resolving overlapping isotropic signals. We present here a two-dimensional method which can enable sites with the same isotropic chemical shift to be distinguished according to their chemical shift anisotropy and asymmetry. The method involves correlating sideband spectra at different effective spinning rates using CSA-amplification pulse sequences. The resulting two-dimensional correlation pattern allows very accurate determination of the chemical shift principal values in addition to the recovery of parameters for two overlapping patterns which allows the resolution of overlapping signals.
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Burley JC, Duer MJ, Stein RS, Vrcelj RM. Enforcing Ostwald's rule of stages: Isolation of paracetamol forms III and II. Eur J Pharm Sci 2007; 31:271-6. [PMID: 17561383 DOI: 10.1016/j.ejps.2007.04.002] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2006] [Revised: 04/05/2007] [Accepted: 04/11/2007] [Indexed: 11/25/2022]
Abstract
We have been able to isolate and study the polymorphic form III of paracetamol using a specially designed methodology. Our work represents the first report of a reproducible, reliable route to form III. This has been an outstanding problem for over quarter of a century. Our method may be applicable to the isolation of metastable polymorphs of other compounds.
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Duer MJ, García F, Goodman JM, Hehn JP, Kowenicki RA, Naseri V, McPartlin M, Stead ML, Stein R, Wright DS. Structural, Solid-State NMR and Theoretical Studies of the Inverse-Coordination of Lithium Chloride Using Group 13 Phosphide Hosts. Chemistry 2007; 13:1251-60. [PMID: 17086573 DOI: 10.1002/chem.200600781] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The reaction of MeAlCl2 with 'PhPLi2' in THF gives [{MeAl(PPh)3Li(4).3 THF}4(mu4-Cl)]-Li+ (1). The GaIII and InIII analogues, [{MeE(PPh)3Li(4).3 THF}4(mu4-Cl)]-Li+(THF)3 (E=Ga (2), In (3)), are obtained by the in situ reactions of MeECl2 with PhPLi2 in THF. For all of the complexes, the cage anions have an unusual cubic arrangement that is similar to a zeolite, and contain large voids (ca. 17 A). The location of the Li+ counterions in 1-3 and their coordination environment appears to subtly reflect variations in packing and lattice energy. Whereas in 1 highly mobile, loosely coordinated Li+ counterions are present, 2 and 3 contain less mobile THF-solvated counterions within the cavities. X-ray crystallographic and solid-state NMR studies are reported on 1-3, together with model DFT calculations on the selectivity of halide coordination.
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Duer MJ, García F, Kowenicki RA, Naseri V, McPartlin M, Stead ML, Stein RS, Wright DS. Inverse coordination of an ionic lattice by a metal host. Angew Chem Int Ed Engl 2006; 44:5729-33. [PMID: 16078283 DOI: 10.1002/anie.200501198] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Orr RM, Duer MJ. Decoupling residual dipolar coupling between 13C and14N spin pairs in CPMAS NMR. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2006; 30:130-4. [PMID: 16889945 DOI: 10.1016/j.ssnmr.2006.06.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2006] [Revised: 06/13/2006] [Accepted: 06/23/2006] [Indexed: 05/11/2023]
Abstract
Decoupling of the residual dipolar coupling between (13)C and(14)N nuclei is investigated experimentally in a triple resonance experiment. It is shown that pulsed decoupling can be used to give enhanced sensitivity and reduced line widths and the technique is illustrated using short peptides.
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Mason MJ, Lucas SJ, Wise ER, Stein RS, Duer MJ. Ossicular density in golden moles (Chrysochloridae). J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2006; 192:1349-57. [PMID: 16944164 DOI: 10.1007/s00359-006-0163-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2006] [Revised: 08/02/2006] [Accepted: 08/06/2006] [Indexed: 11/25/2022]
Abstract
The densities of middle ear ossicles of golden moles (family Chrysochloridae, order Afrosoricida) were measured using the buoyancy method. The internal structure of the malleus was examined by high-resolution computed tomography, and solid-state NMR was used to determine relative phosphorus content. The malleus density of the desert golden mole Eremitalpa granti (2.44 g/cm3) was found to be higher than that reported in the literature for any other terrestrial mammal, whereas the ossicles of other golden mole species are not unusually dense. The increased density in Eremitalpa mallei is apparently related both to a relative paucity of internal vascularization and to a high level of mineralization. This high density is expected to augment inertial bone conduction, used for the detection of seismic vibrations, while limiting the skull modifications needed to accommodate the disproportionately large malleus. The mallei of the two subspecies of E. granti, E. g. granti and E. g. namibensis, were found to differ considerably from one another in both size and shape.
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Orr RM, Duer MJ. Recoupling of chemical-shift anisotropy powder patterns in MAS NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2006; 181:1-8. [PMID: 16574445 DOI: 10.1016/j.jmr.2006.03.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2006] [Revised: 03/10/2006] [Accepted: 03/10/2006] [Indexed: 05/08/2023]
Abstract
A comparison of three different implementations of the chemical-shift recoupling experiment of Tycko et al. [R. Tycko, G. Dabbagh, P.A. Mirau, Determination of chemical-shift-anisotropy lineshapes in a two-dimensional magic-angle-spinning NMR experiment, J. Magn. Reson. 85 (1989) 265-274] is presented. The methods seek to reduce the effects of artefacts resulting from pulse imperfections and residual C-H dipolar coupling in organic solids. An optimised and constant time implementation are shown to give well-defined and artefact free powder pattern lineshapes in the indirectly observed dimension for both sp2 and sp3 carbon sites. Experimental setup is no more demanding than for the original experiment, and can be implemented using standard commercial hardware.
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Orr RM, Duer MJ. Applications of the CSA-amplified PASS experiment. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2006; 30:1-8. [PMID: 16406513 DOI: 10.1016/j.ssnmr.2005.12.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2005] [Revised: 11/28/2005] [Indexed: 05/06/2023]
Abstract
The recently reported CSA-amplified PASS experiment correlates the spinning sidebands at the true spinning frequency omega(r) with the spinning sidebands that would be obtained at the effective spinning frequency omega(r)/N, where N is termed the scaling factor. The experiment is useful for the measurement of small chemical shift anisotropies, for which slow magic-angle spinning frequencies, required to measure several spinning sidebands, can be unstable. We have experimentally evaluated the reliability of this experiment for this application. In particular we have demonstrated that large scaling factors of the order of N=27 may be used, whilst still obtaining accurate chemical shift sideband intensities at the effective spinning frequency from the F(1) projection. Moreover, the sideband intensities are accurately obtained even in the presence of significant pulse imperfections. A second application of the CSA-amplified PASS experiment is the measurement of the chemical shift anisotropy of sites that experience homonuclear dipolar coupling, as may be found in uniformly labelled biological molecules, or for nuclei with a high natural abundance. The effects of homonuclear dipolar coupling on CSA-amplified PASS spectra has been investigated by numerical simulations and are demonstrated using uniformly (13)C enriched l-histidine monohydrochloride monohydrate.
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Duer MJ, García F, Kowenicki RA, Naseri V, McPartlin M, Stead ML, Stein RS, Wright DS. Inverse Coordination of an Ionic Lattice by a Metal Host. Angew Chem Int Ed Engl 2005. [DOI: 10.1002/ange.200501198] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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