Furthering the understanding of silicate-substitution in α-tricalcium phosphate: an X-ray diffraction, X-ray fluorescence and solid-state nuclear magnetic resonance study.

High-purity (SupT) and reagent-grade (ST), stoichiometric and silicate-containing α-tricalcium phosphate (α-TCP: ST0/SupT0 and Si-TCP x=0.10: ST10/SupT10) were prepared by solid-state reaction based on the substitution mechanism Ca3(PO4)(2-x)(SiO4)x. Samples were determined to be phase pure by X-ray diffraction (XRD), and Rietveld analysis performed on the XRD data confirmed inclusion of Si in the α-TCP structure as determined by increases in unit cell parameters; particularly marked increases in the b-axis and ß-angle were observed. X-ray fluorescence (XRF) confirmed the presence of expected levels of Si in Si-TCP compositions as well as significant levels of impurities (Mg, Al and Fe) present in all ST samples; SupT samples showed both expected levels of Si and a high degree of purity. Phosphorus ((31)P) magic-angle-spinning solid-state nuclear magnetic resonance (MAS NMR) measurements revealed that the high-purity reagents used in the synthesis of SupT0 can resolve the 12 expected peaks in the (31)P spectrum of α-TCP compared to the low-purity ST0 that showed significant spectral line broadening; line broadening was also observed with the inclusion of Si which is indicative of induced structural disorder. Silicon ((29)Si) MAS NMR was also performed on both Si-TCP samples which revealed Q(0) species of Si with additional Si Q(1)/Q(2) species that may indicate a potential charge-balancing mechanism involving the inclusion of disilicate groups; additional Q(4) Si species were also observed, but only for ST10. Heating and cooling rates were briefly investigated by (31)P MAS NMR which showed no significant line broadening other than that associated with the emergence of ß-TCP which was only realised with the reagent-grade sample ST0. This study provides an insight into the structural effects of Si-substitution in α-TCP and could provide a basis for understanding how substitution affects the physicochemical properties of the material.

Thermal stability and structure of cancellous bone mineral from the femoral head of patients with osteoarthritis or osteoporosis.

BACKGROUND: Cancellous bone from patients with osteoarthritis (OA) has been reported to be undermineralised and that from patients with osteoporosis (OP) is more liable to fracture. Changes in the mineral component might be implicated in these processes. OBJECTIVES: To investigate the thermal stability and the mineral structure of cancellous bone from femoral heads of patients with either OA or OP. METHODS: Powdered bone was prepared from femoral heads of patients with either OA or OP and a control group. Composition and thermal stability were determined using a thermogravimetric analyser coupled to a mass spectrometer. Unit cell dimensions and the crystallite size of the mineral were measured using x ray diffraction. RESULTS: Thermal stability of the bone matrix, or of the mineral phase alone, was little altered by disease, though OA bone contained less mineral than OP or control bone. In all three groups, x ray diffraction showed that the mineral unit cell dimensions and crystallite sizes were the same. The mean carbonate content in the mineral from all three groups was between 7.2 and 7.6% and is suggested to be located in both the A site (that is, substituting for hydroxyl groups), and the B site (that is, substituting for phosphate groups). CONCLUSIONS: These results confirm that there is a lower mass fraction of mineral in OA bone, and indicate that the nature of the mineral is not a factor in either disease process.

Effect of the proportion of organic material in bone on thermal decomposition of bone mineral: an investigation of a variety of bones from different species using thermogravimetric analysis coupled to mass spectrometry, high-temperature X-ray diffraction, and Fourier transform infrared spectroscopy.

Thermogravimetric analysis linked to mass spectrometry (TGA-MS) shows changes in mass and identifies gases evolved when a material is heated. Heating to 600 degrees C enabled samples of bone to be classified as having a high (cod clythrum, deer antler, and whale periotic fin bone) or a low (porpoise ear bone, whale tympanic bulla, and whale ear bone) proportion of organic material. At higher temperatures, the mineral phase of the bone decomposed. High temperature X-ray diffraction (HTXRD) showed that the main solids produced by decomposition of mineral (in air or argon at 800 degrees C to 1000 degrees C) were beta-tricalcium phosphate (TCP) and hydroxyapatite (HAP), in deer antler, and CaO and HAP, in whale tympanic bulla. In carbon dioxide, the decomposition was retarded, indicating that the changes observed in air and argon were a result of the loss of carbonate ions from the mineral. Fourier transform infrared (FTIR) spectroscopy of bones heated to different temperatures, showed that loss of carbon dioxide (as a result of decomposition of carbonate ions) was accompanied by the appearance of hydroxide ions. These results can be explained if the structure of bone mineral is represented by [Formula: see text] where V(Ca) and V(OH) correspond to vacancies on the calcium and hydroxide sites, respectively, and 2-x-y = 0.4. This general formula is consistent in describing both mature bone mineral (i.e., whale bone), with a high Ca/P molar ratio, lower HPO4(2-) content, and higher CO3(2-) content, and immature bone mineral (i.e., deer antler), with a low Ca/P ratio, higher HPO4(2-), and lower CO3(2-) content.

Sheep lumbar intervertebral discs as models for human discs.

OBJECTIVE: To determine the water content, collagen content and collagen orientation angle in different regions of sheep lumbar discs. DESIGN: A laboratory study of sheep discs obtained from an abattoir. METHODS: A total of 21 sheep lumbar discs were obtained from three lumbar spines. Water content was determined by oven drying (60 degrees C) to constant mass. Collagen content was determined by hydroxyproline analysis. Fibre orientation angles were determined by X-ray diffraction. RESULTS: Water content increased from 74% of total tissue mass in the outer annulus, to 82% in the inner annulus, to 86% in the nucleus. Collagen content decreased from 30% of total tissue mass in the outer region to 20% in the inner region of the anterior and lateral annulus; it was 16% in the posterior annulus. The orientation angle of the collagen fibres decreased from 59 degrees in the outer region to 56 degrees in the inner region of the anterior and lateral annulus; it was 51 degrees in the posterior annulus. CONCLUSIONS: Sheep lumbar intervertebral discs provide a reasonable model for human lumbar intervertebral discs. RELEVANCE: Sheep lumbar discs have been used to investigate the effects of removing and replacing the nucleus. These studies indicate that removal of nucleus may lead to further disc degeneration and indicate the material properties required for an implant material. The relevance of these previous studies is increased if human and sheep lumbar discs have a similar composition and structure.

Hydrogen bonding in C-methylated nitroanilines: a room-temperature monoclinic polymorph of 4-methyl-3-nitroaniline with Z' = 2.

The title compound, C(7)H(8)N(2)O(2), is monoclinic (space group P2(1)/n) at 295 (2) K with Z' = 2. The two types of molecule form independent C(7) chains, and the structure is related to that of the low-temperature triclinic polymorph, where Z' = 4 in P1, by a simple displacive transformation.

Hydrogen bonding in nitroaniline analogues: a three-dimensional framework in 2-amino-6-nitro-1,3-benzothiazole.

In the title compound, C(7)H(5)N(3)O(2)S, the molecules are linked into a three-dimensional framework by a combination of a three-centre N-H...(O)(2) hydrogen bond, and two-centre N-H...N and C-H...O hydrogen bonds.

4-Iodo-2-methyl-5-nitroaniline exhibits neither strong hydrogen bonding nor intermolecular I...nitro interactions.

In the title compound, C(7)H(7)IN(2)O(2), the O atoms of the nitro group are disordered over two sets of sites and there is evidence that the intramolecular I...nitro interaction is repulsive. In the crystal structure, there are neither strong hydrogen bonds, nor intermolecular I...nitro interactions, nor aromatic pi-pi-stacking interactions.

Triclinic and orthorhombic polymorphs of 2-iodo-4-nitroaniline: interplay of hydrogen bonds, nitro...I interactions and aromatic pi-pi-stacking interactions.

In the triclinic polymorph of 2-iodo-4-nitroaniline, C(6)H(5)IN(2)O(2), space group P-1, the molecules are linked by paired N-H...O hydrogen bonds into C(8)[R(2)(2)(6)] chains of rings. These chains are linked into sheets by nitro...I interactions, and the sheets are pairwise linked by aromatic pi-pi-stacking interactions. In the orthorhombic polymorph, space group Pbca, the molecules are linked by single N-H...O hydrogen bonds into spiral C(8) chains; the chains are linked by nitro...O interactions into sheets, each of which is linked to its two immediate neighbours by aromatic pi-pi-stacking interactions, so producing a continuous three-dimensional structure.

Hydrogen-bonded chains in N-(2-nitrophenyl)phenylamine.

Molecules of the title compound, C(12)H(10)N(2)O(2), are markedly non-planar. There is an intramolecular N-H...O hydrogen bond, and the molecules are linked into zigzag chains by a single C-H...O hydrogen bond. Comparisons are made with the supramolecular aggregation in isomeric amino-nitro derivatives, and in some N-methylnitroanilines.

Diphenyl(2-thioxo-1,3-dithiole-4,5-dithiolato-S,S')plumbane at 295 K and diphenyl(2-thioxo-1,3-dithiole-4,5-dithiolato-S,S')stannane at 150 K.

Molecules of diphenyl(2-thioxo-1,3-dithiole-4,5-dithiolato-S,S')plumbane, [Pb(C3S5)(C6H5)2], are linked into sheets via two intermolecular Pb...S(thione) interactions of 3.322 (4) and 3.827 (4) A; the Pb centre has a distorted octahedral geometry. In contrast, molecules of diphenyl(2-thioxo-1,3-dithiole-4,5-dithiolato-S,S')stannane, [Sn(C3S5)(C6H5)2], are linked into chains via a single intermolecular Sn--S(thione) interaction of 2.8174 (9) A; the Sn centre has a distorted trigonal-bipyramidal geometry.

A new polymorph, form C, of [1,2-bis(diphenylphosphino)ethane]-dichloronickel(II).

The title compound, [NiCl2(C26H24P2)], has arisen as a result of the unexpected reduction (hydrogenation) of the trans-1,2-bis(diphenylphosphino)ethene ligand. The hydrothermal reaction conditions have produced a third polymorphic form of the compound which has twofold symmetry, crystallizes in an enantiomer-selective manner and contains an unexpectedly short C-C (ethane) bond. Contacts of the form C-H...Cl are present, one involving alkyl and the other aryl hydrogen, with C.Cl distances of 3.556 (4) and 3.664 (6) A, respectively.

Solvated and solvent-free forms of N,N'-dithiodiphthalimide.

N,N'-Dithiodiphthalimide, C16H8N2O4S2, crystallizes from ethyl acetate with two independent molecules in the asymmetric unit, in which the N-S-S-N torsion angles are -83.59 (19) and 92.9 (2) degrees. The molecules are linked by C-H...O hydrogen bonds and aromatic pi-pi-stacking interactions into a three-dimensional framework. When crystallized from either dichloromethane or ethanol, solvates are formed in which the molecules of the title compound lie across twofold rotation axes in space group C2/c, with N-S-S-N torsion angles of 93.54 (7) and 96.14 (11) degrees. There are no hydrogen bonds in these solvates, but the molecules are linked by aromatic pi-pi-stacking interactions into chains, between which there are continuous channels. Disordered solvent molecules occupy these channels, which account for ca 20% of the unit-cell volume.

Soft C-H.O hydrogen bonds in methyl 2,4-dinitrobenzenesulfenate: sheets built from R22(10) and R66(42) rings.

Molecules of the title compound, C(7)H(6)N(2)O(5)S, are linked into sheets containing R(2)(2)(10) and R(6)(6)(42) rings by C-H.O hydrogen bonds [C.O 3.405 (3) and 3.511 (2) A; C-H.O 159 and 169 degrees ], in which both acceptors are in the same nitro group. Comparisons are made with the hydrogen bonding in other nitrobenzenesulfenate esters.

Hydrogen bonding in substituted nitroanilines: isolated nets in 1,3-diamino-4-nitrobenzene and continuously interwoven nets in 3,5-dinitroaniline.

Molecules of 1,3-diamino-4-nitrobenzene, C(6)H(7)N(3)O(2), are linked by N-H.O hydrogen bonds [N.O 2.964 (2) and 3.021 (2) A; N-H.O 155 and 149 degrees] into (4,4) nets. In 3,5-dinitroaniline, C(6)H(5)N(3)O(4), where Z' = 2, the molecules are linked by three N-H.O hydrogen bonds [N.O 3.344 (2)-3.433 (2) A and N-H.O 150-167 degrees] into deeply puckered nets, each of which is interwoven with its two immediate neighbours.

Hydrogen bonding in C-methylated nitroanilines: the three-dimensional framework structure of 2-methyl-4-nitroaniline.

Molecules of 2-methyl-4-nitroaniline, C(7)H(8)N(2)O(2), act as double donors and as double acceptors of N--H...O hydrogen bonds [N...O 3.117 (3) and 3.239 (3) A; N--H...O 169 and 136 degrees ]. The molecules are thereby linked into a three-dimensional framework.