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PubMed2001

Determination of indomethacin polymorphic contents by chemometric near-infrared spectroscopy and conventional powder X-ray diffractometry.

A chemoinfometric method for the quantitative determination of the crystal content of indomethacin (IMC) polymorphs, based on Fourier-transform near-infrared (FT-NIR) spectroscopy, was established. A direct comparison of the data with those collected using the conventional powder X-ray diffraction method was performed. Pure alpha and gamma forms of IMC were prepared using published methods. Powder X-ray diffraction profiles and NIR spectra were recorded for six kinds of standard material with various contents of the gamma form of IMC. Principal component regression (PCR) analyses were performed on the basis of the normalized NIR spectral sets of standard samples with known contents of the gamma form of IMC. A calibration equation was determined to minimize the root mean square error of the prediction. The predicted gamma form contents were reproducible and had a relatively small standard deviation. The values of the gamma form contents predicted by the two methods were in close agreement. The results indicated that NIR spectroscopy provides an accurate quantitative analysis of crystallinity in polymorphs compared with the results obtained by conventional powder X-ray diffractometry.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2000

Physicochemical characterization of a new crystal form and improvements in the pharmaceutical properties of the poorly water-soluble antiosteoporosis drug 3,9-bis(N,N-dimethylcarbamoy-loxy)-5H-benzofuro[3,2-c]quinoline-6-one (KCA-098) by solid dispersion with hydroxypropylcellulose.

The present study was undertaken to improve the oral absorption of KCA-098, an antiosteoporosis drug. In this study, the form 2 of KCA-098 was used as a desirable crystal form for pharmaceutical formation among three kinds of crystal forms, 1, 2, and 3. Solid dispersions of KCA-098 with hydroxypropylcellulose (HPC) or poly(vinylpyrrolidone) (PVP) were prepared by the solvent method. The physicopharmaceutical properties of the solid dispersions were characterized by powder x-ray diffraction, FTIR spectroscopy, and differential scanning calorimetry (DSC). The powder x-ray diffractograms suggest that KCA-098 in the HPC-SL solid dispersion existed in a partial crystalline state as a new crystal form that could be produced by recrystallization from the solvent. Dissolution from the solid dispersions was markedly enhanced in comparison with that of the drug alone. The dissolution enhancement was observed to be greater for the solid dispersion with HPC-SL than for that with PVP. The KCA-098/HPC-SL (1:2) solid dispersion capsule showed a 3.5-fold increase in the initial concentration and 2.5-fold increase in initial concentration of dissolved drug after 60 min, compared with the values for a physical mixture of KCA-098 (form 2)/lactose (1:2). The in vivo absorption of the drug was investigated after oral administration of KCA-098 or its solid dispersion. The area under the plasma concentration curve of KCA-098 after oral administration of the KCA-098/HPC-SL (1:2) solid dispersion capsule was three-fold greater than that for the drug itself.

Absorption↗
PubMed2006

A symmetrical indexing scheme for decagonal quasicrystals analogous to Miller-Bravais indexing of hexagonal crystals.

The problems of redundancy and superfluous indices in indexing the planes and axes in a decagonal quasicrystal are considered, using a scheme of five coplanar vectors in the quasiperiodic plane and one perpendicular vector. Of all the indexing schemes in use, this scheme offers the maximum advantage. An analogy is drawn to the hexagonal system using Miller-Bravais indices. Based on this, a symmetry-based indexing system for decagonal phases is devised that follows a simplified approximate zone law analogous to the exact zone law for the hexagonal case. The indices based on this scheme will be designated as ;Frank indices'. High-symmetry electron diffraction zone-axis patterns as well as powder X-ray diffraction patterns are indexed using Frank indices and compared with those of other indexing schemes.

Alloys↗
PubMed1993

Direct phase determination by entropy maximization and likelihood ranking: status report and perspectives.

A new multisolution phasing method based on entropy maximization and likelihood ranking, proposed for the specific purpose of extending probabilistic direct methods to the field of macromolecules, has been implemented in two different computer programs and applied to a wide variety of problems. The latter comprise the determination of small crystal structures from X-ray diffraction data obtained from single crystals or from powders, and from electron diffraction data partially phased by image processing of electron micrographs, the ab initio generation and ranking of phase sets for small proteins; and the improvement of poor quality phases for a larger protein at medium resolution under constraint of solvent flatness. These applications show that the primary goal of this new method - namely increasing the accuracy and sensitivity of probabilistic phase indications compared with conventional direct methods - has been achieved. The main components of the method are (1) a tree-directed search through a space of trial phase sets; (2) the saddle-point method for calculating joint probabilities of structure factors, using entropy maximization; (3) likelihood-based scores to rank trial phase sets and prune the search tree; (4) efficient schemes, based on error-correcting codes, for sampling trial phase sets; (5) a statistical analysis of the scores for automatically selecting reliable phase indications. They have been implemented to varying degrees of completeness in a computer program (BUSTER) and tested on two small structures as well as on the small protein crambin. The main obstructions to successful ab initio phasing in the latter case seem to reside in the accumulation of phase sampling errors and in the lack of a properly defined molecular envelope, both of which can be remedied within the methods proposed. A review of the Bayesian statistical theory encompassing all phasing procedures, proposed earlier as an extension of the initial theory, shows that the techniques now available in BUSTER bring closer a number of major enhancements of standard macromolecular phasing techniques, namely isomorphous replacement, molecular replacement, solvent flattening and non-crystallographic symmetry averaging. The gradual implementation of the successive stages of this 'Bayesian programme' should lead to an increasingly integrated, effective and dependable phasing procedure for macromolecular structure determination.

Journal Article↗
PubMed1991

Diacetylenic lipid microstructures: structural characterization by X-ray diffraction and comparison with the saturated phosphatidylcholine analogue.

Thermotropic and lyotropic mesomorphism in the polymerizable lecithin 1,2-ditricosa-10,12-diynoyl-sn-glycero-3-phosphocholine and its saturated analogue, 1,2-ditricosanoyl-sn-glycero-3-phosphocholine, has been investigated by wide- and low-angle X-ray diffraction of both powder and oriented samples and by differential scanning calorimetry. Previous studies have shown that the hydrated diacetylenic lipid forms novel microstructures (tubules and stacked bilayer sheets) in its low-temperature phase. The diffraction results indicate that at low temperatures fully hydrated tubules and sheets have an identical lamellar repeat size (d001 = 66.4 A) and crystalline-like packing of the acyl chains. Chain packing in the lamellar crystalline phase is hydration independent. A model for the polymerizable lecithin with (1) fully extended all-trans methylene segments, (2) a long-axis tilt of 32 degrees, and (3) minimal chain interdigitation seems most reasonable on energetic grounds, is consistent with the diffraction data (to 3.93-A resolution), and is likely to support facile polymerization. Above the chain "melting" transition the lamellar repeat of the polymerizable lipid increases to 74 A. The conformational similarity between tubules, sheets, and the dry powder is corroborated by calorimetry, which reveals a cooling exotherm at the same temperature where tubules form upon cooling hydrated sheets. The data suggest that although a high degree of conformational order is a pertinent feature of tubules, this character alone is not sufficient to account for tubule formation. The conformation of the corresponding saturated phosphatidylcholine appears to be similar to that of other saturated phosphatidylcholines in the lamellar gel phase. Furthermore, above the main transition temperature, the dry, saturated lipid shows evidence of a P delta phase (112 degrees C), whereas the diacetylenic lipid appears to exhibit a centered rectangular phase, R alpha (55 degrees C).

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2003

Structural diversity and polytypism of lead phenylphosphonates: BING-6 and BING-9.

We report the solvothermal synthesis and characterization of a series of layered lead phenylphosphonates. The crystals were suitable for single crystal X-ray diffraction data, and the two new structures we denote BING-6 [SUNY at Binghamton, Structure No. 6, Pb(PO(3)C(6)H(5)).0.25C(5)H(5)N, triclinic space group Ponemacr;, Z = 2, a = 7.0770(4) A, b = 9.3113(6) A, c = 14.6785(9) A, alpha = 80.456(1) degrees, beta = 78.023(1) degrees, gamma = 73.265(1)(o)] and BING-9 [Pb(PO(3)HC(6)H(5))(PO(3)HC(6)H(4)CH(3)), monoclinic space group C2/c, Z = 4, a = 32.663(8) A, b = 5.6220(13) A, c = 8.3307(19) A, beta = 101.419(4)(o)]. The third structure, a polytype of BING-9, was previously known only from powder X-ray diffraction methods and is denoted 3 [Pb(PO(3)HC(6)H(5))(2), monoclinic space group C2/c, Z = 4, a = 31.681(6) A, b = 5.5639(11) A, c = 8.2515(16) A, beta = 101.814(4)(o)]. All three structures possess Pb(II) and P centers connected by doubly and triply bridging oxygens. The phenyl groups cap and separate the charge-neutral layers. The phosphonates of BING-6 are nonprotonated, and the structure therefore has a Pb/P ratio of 1:1. Neutral, partially disordered pyridine solvent molecules also reside in the interlamellar space, increasing the layer to layer distance. BING-9 and 3 are polytypes and contain singly protonated phosphonates, for a Pb/P ratio of 1:2. Further characterization methods are discussed, including powder X-ray diffraction, in-situ variable temperature powder X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. Related work in the Ge, Sn, and Mn systems is also discussed. These low-dimensional materials may be useful intercalation compounds for ion-exchange or sensor applications.

Journal Article↗
PubMed1996

Effect of pulverization on dehydration behavior of crystals of GK-128, a serotonin3 receptor antagonist.

The effect of pulverization on the dehydration behavior of 2-[(2-methylimidazol-1-yl)methyl]benzo[i]thiochromen-1-one monohydrochloride hemihydrate (GK-128), a newly developed serotonin3 receptor antagonist, was studied using powder X-ray diffraction analysis, thermogravimetry (TG), and differential scanning calorimetry (DSC). The crystalline forms of GK-128 obtained by pulverizing with a jet mill and an agale mortar were each confirmed to be the same as that of intact GK-128, since the powder X-ray diffraction patterns of the two prepared samples were identical with that of intact GK-128. However, after pulverization by jet mill, the dehydration temperature of GK-128 was markedly lowered and the DSC endothermic peak due to dehydration disappeared. The activation energy for dehydration, calculated by the Ozawa method using TG data, decreased with decreasing particle size and/or crystallinity of GK-128 crystals, e.g., the activation energies for dehydration of intact and jet-milled GK-128 were 128.1 and 75.9 kj/mol, respectively. The results of comparison of powder X-ray diffraction patterns of pulverized GK-128 and intact GK-128 and of determination of the crystal structure of GK-128 suggested that water molecules could be removed easily along the c-axis of GK-128 crystals.

Calorimetry, Differential Scanning↗
PubMed2000

Crystal structure of the low-temperature phase of beta Cu1.75Se analysed by electron diffraction

The beta phase of Cu1.75Se has an anti-fluorite structure, where one in eight tetrahedral copper sites are vacant. Powder X-ray diffraction measurements on Cu1.75Se showed that the beta phase transformed to a two-phase mixture of (alpha + beta) at approximately 250 K, and then the beta phase changed to a new phase at approximately 180 K. Powder X-ray and electron diffraction measurements revealed that the low-temperature phase of the beta phase has a superstructure of (2alpha(fcc) x 2alpha(fcc) x 2alpha(fcc)) type, where alpha(fcc) is the lattice parameter of the original beta phase. The superstructure was interpreted to originate from the ordering copper vacancies. The new phase was referred to as the beta' phase.

Journal Article↗
PubMed2003

[Identification on Herba Hedyotidis by X-ray diffraction Fourier fingerprint pattern method].

OBJECTIVE: To establish a new identification and analysis method of Herba Hedyotidis. METHOD: Powder X-Ray diffraction fourier fingerprint pattern method. RESULT: Experiment and analysis were carried out on eight samples. The standard X-Ray diffraction fourier fingerprint pattern method and characteristic diffraction peaks of Herba Hedyotidis were obtained. CONCLUSION: This method can be used for the identification of Herba Hedyotidis.

Drug Contamination↗
PubMed1997

Direct bone formation on alumina bead composite.

We have developed a composite (designated ABC), consisting of alumina bead powder as an inorganic filler and bisphenol-alpha-glycidyl methacrylate (Bis-GMA)-based resin as an organic matrix, which allows direct bone formation on its surface in vivo. Alumina bead powder was manufactured by fusing crushed alpha-alumina powder and quenching it. The beads took spherical form 3 microns in average size. According to powder X-ray diffraction and Fourier transform infrared spectroscopy, the alumina bead powder was composed of amorphous and delta-crystal phases of alumina in its main crystal structure. Fused-quenched silica glass-filled composite (SGC) was used as a control. The proportion of filler added to the composites was 70% w/w. Mechanical testing of the ABC indicated that it would be strong enough for use under weight-bearing conditions. No apatite formation was detected on the surfaces of either composite after soaking in simulated body fluid for 28 days in vitro. Histological examination of rat tibiae for up to 8 weeks revealed that ABC bonded to bone directly via a layer of calcium, phosphorus, and alumina with no interposed soft-tissue layer. Moreover, the amount of bone directly apposed to the ABC surface increased with time, whereas with SGC there was poor direct bone formation even at 8 weeks. The precise mechanism of direct bone formation on ABC is as yet unknown but it is possible that changes in the crystallinity of alumina, which is known to be highly biocompatible, contribute to its excellent osteoconductivity in vivo. Although bioactive materials such as Bioglass or apatite and wollastonite-containing glass-ceramic have previously been reported to form bone-like apatite on their surfaces under acellular conditions via simple chemical reactions, ABC does not have such characteristics, and presenting favorable conditions for osteoconduction and tissue calcification may lead to direct bone formation on its surface in vivo.

Aluminum Oxide↗
PubMed1996

Synthesis and Crystal Structures of Two Novel Anionic Aluminophosphates: A One-Dimensional Chain, UT-7 ([Al(3)P(5)O(20)H](5-)[C(7)H(13)NH(3)(+)](5)), and a Layer Containing Two Cyclic Amines, UT-8 ([Al(3)P(4)O(16)](3-)[C(4)H(7)NH(3)(+)](2)[C(5)H(10)NH(2)(+)]).

UT-7 and UT-8 (University of Toronto, structure numbers 7 and 8) are two novel aluminophosphate materials prepared under non-aqueous conditions. Their structures, extended in one and two dimensions, respectively, have been solved by single-crystal X-ray diffraction and characterized by a variety of methods including powder X-ray diffraction (PXRD), insitu high-temperature PXRD, thermogravimetric analysis (TGA), energy dispersive X-ray analysis (EDX), and scanning electron microscopy (SEM). UT-7 ([Al(3)P(5)O(20)H](5)(-)[C(7)H(13)NH(3)(+)](5), triclinic space group P&onemacr;, Z = 2, a = 10.118(3) Å, b = 15.691(4) Å, c = 18.117(3) Å, alpha = 72.91(2) degrees, beta = 85.18(2) degrees, gamma = 79.49(2) degrees ) is built of polymeric one-dimensional chain units, hydrogen-bonded into anionic layers that are charge-compensated by interlamellar cycloheptylammonium cations. UT-7 is isostructural to our previously discovered UT-3 chain structure, isolated in the analogous cyclopentylamine system. UT-8 ([Al(3)P(4)O(16)](3-)[C(4)H(7)NH(3)(+)](2)[C(5)H(10)NH(2)(+)], monoclinic space group P2(1), Z = 2, a = 8.993(4) Å, b = 14.884(8) Å, c = 9.799(9) Å, beta = 103.52(3) degrees ) is a two-dimensional net isostructural to several previously reported [Al(3)P(4)O(16)](3)(-) layers. The interlayer region of UT-8 is occupied by two different cyclic organic amine species, namely piperidinium and cyclobutylammonium. To our knowledge, this is the first report of the crystal structure of an aluminophosphate material containing cyclobutylammonium or a mixture of cyclic amines. Interestingly, UT-7 is observed to thermally transform in the solid state to an as yet unknown layered material that can be independently synthesized in a similar synthetic system. In the same way as UT-3 transforms to the UT-4 layered phase, we believe UT-7 transforms to a layered material by means of a chain to layer transformation.

Journal Article↗
PubMed2004

Measurement of coherent x-ray scatter form factors for amorphous materials using diffractometers.

The feasibility of measuring the coherent x-ray scatter form factors of amorphous materials using powder diffractometers has been assessed. A five-step procedure was developed: (i) Low-angle background, consisting of a portion of the incident x-ray beam that passes directly to the detector, is measured using a specially designed replacement for the sample holder which absorbs most of the photons that otherwise would scatter off the sample holder cavity. (ii) Angle-dependent effects including monochromator efficiency and projected beam area are characterized by extracting the incoherent signal from the diffraction pattern of powdered graphite. The incoherent signal divided by the calculated incoherent cross section gives a correction factor as a function of scattering angle theta. (iii) Diffraction patterns are measured for the samples for theta = 2 degrees -150 degrees. (iv) The scattering data are corrected for background and then for angle-dependent effects. (v) The data are normalized to calculated free atom form factors at high theta, and the coherent form factor extracted. The method was implemented on two diffractometers at different energies (Co Kalpha and Cu Kalpha), and the results compared for water and plastics. Over the range 0.117 < x < 5.39 nm(-1), where x = lambda(-1) sin(theta/2), the average form factor ratio for water was 0.93. Systematic errors are difficult to eliminate. While this x-ray powder diffractometer technique suffices for a survey measurement of the form factor of a material, its accuracy is probably insufficient for detailed studies.

Algorithms↗
PubMed2003

Direct structure determination of a multicomponent molecular crystal prepared by a solid-state grinding procedure.

A three-component molecular cocrystal material has been prepared by a solvent-free route involving mechanical grinding of the pure phases of the individual components. This material is not accessible from conventional solution-state crystallization procedures. Due to the fact that the grinding procedure intrinsically leads to a microcrystalline powder sample, the use of powder X-ray diffraction data is essential for structure determination. This work emphasizes the scope and utility of ab initio structure solution directly from powder X-ray diffraction data for carrying out structural characterization of new materials prepared via the solid-state grinding route, leading to the opportunity to establish structure-property relationships for such materials.

Journal Article↗
PubMed2001

Naproxen particle design using porous starch.

Naproxen (Nap) was embedded in porous starch by preferential grinding, and we examined the physicochemical properties of these particles, including pore diameter, pore volume, and dissolution of naproxen. Porous starch (PS) particles made by preferential grinding with a Mechanofusion system had a higher content of naproxen than those made using the Mechanomill as determined using a mercury porosimeter. Neither sample showed any significant changes in crystallization state of naproxen in particles as determined by powder X-ray diffraction and differential scanning calorimetry (DSC). No interactions occurred between naproxen and porous starch due to preferential grinding as determined by powder X-ray diffraction and DSC. The dissolution rate of drug from particles prepared by preferential grinding was faster than that from physical mixtures.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2005

A solid-state NMR method for solution of zeolite crystal structures.

Since zeolites are notoriously difficult to prepare as large single crystals, structure determination usually relies on powder X-ray diffraction (XRD). However, structure solution (i.e., deriving an initial structural model) directly from powder XRD data is often very difficult due to the diffraction phase problem and the high degree of overlap between the individual reflections, particularly for materials with the structural complexity of most zeolites. Here, we report a method for structure determination of zeolite crystal structures that combines powder XRD and nuclear magnetic resonance (NMR) spectroscopy in which the crucial step of structure solution is achieved using solid-state (29)Si double-quantum dipolar recoupling NMR, which probes the distance-dependent dipolar interactions between naturally abundant (29)Si nuclei in the zeolite framework. For two purely siliceous zeolite blind test samples, we demonstrate that the NMR data can be combined with the unit cell parameters and space group to solve structural models that refine successfully against the powder XRD data.

Journal Article↗
PubMed2006

Particle design using a 4-fluid-nozzle spray-drying technique for sustained release of acetaminophen.

We prepared matrix particles of acetaminophen (Act) with chitosan (Cht) as a carrier using a newly developed 4-fluid-nozzle spray dryer. Cht dissolves in acid solutions and forms a gel, but it does not dissolve in alkaline solutions. Therefore, we tested the preparation of controlled release matrix particles using the characteristics of this carrier. Act and Cht mixtures in prescribed ratios were dissolved in an acid solution. We evaluated the matrix particles by preparing a solid dispersion using a 4-fluid-nozzle spray dryer. Observation of the particle morphology by scanning electron microscopy (SEM) revealed that the particles from the spray drying process had atomized to several microns, and that they had become spherical. We investigated the physicochemical properties of the matrix particles by powder X-ray diffraction, differential scanning calorimetry, and dissolution rate analyses with a view to clarifying the effects of crystallinity on the dissolution rate. The powder X-ray diffraction peaks and the heat of the Act fusion in the spray-dried samples decreased with the increase of the carrier content, indicating that the drug was amorphous. These results indicate that the system formed a solid dispersion. Furthermore, we investigated the interaction between the drug and carrier using FT-IR analysis. The FT-IR spectroscopy for the Act solid dispersions suggested that the Act carboxyl group and the Cht amino group formed a hydrogen bond. In addition, the measurement results of the 13C CP/MAS solid-state NMR, indicated that a hydrogen bond had been formed between the Act carbonyl group and the Cht amino group. In the Act-Cht system, the 4-fluid-nozzle spray-dried preparation with a mixing ratio of 1 : 5 obtained a sustained release preparation in all pH test solutions.

Acetaminophen↗
PubMed1999

The single-crystal structure of the organic superconductor betaCO-(BEDT-TTF)2I3 from a powder grain.

Synchrotron radiation diffraction data have been collected at 200 K on a microscopic single crystal (dimensions 12 x 10 x 2 µm) of the title compound, where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene, C(10)H(8)S(8). The quality of the diffraction data allowed a full structure refinement and enabled the determination of structural details such as the conformations of the ethylene groups as well as the occupancy of the triiodide sites. The compound was found to be slightly iodine-deficient and better described as beta(CO)-(BEDT-TTF)(2)I(3-x) [x = 0.014 (3)]. One of the ethylene groups of the BEDT-TTF cation is disordered at this temperature and exists in two distinct conformations with occupancies which are identical within the standard uncertainty.

Journal Article↗
PubMed2005

The protective effect of lactose on lyophilization of CNK-20402.

The goal of this research was to assess the feasibility of using lyophilization to stabilize an exploratory compound, CNK-20402, with a minimal amount of impurity (CNK-20193) formation. A mixed-level full factorial experimental design was used to screen excipients of glycine, mannitol, lactose monohydrate, and povidone K-12. Cryostage microscopy, powder x-ray diffraction, Karl Fischer titration, HPLC, and water vapor sorption were used to assess the formulations' physicochemical properties and stability. Initial physical characterization from powder x-ray diffraction revealed that the mannitol- and glycine-containing formulations were crystalline with the patterns of the pure excipient, whereas the remaining formulations were amorphous in structure. Chemically, the formulations stored at 50 degrees C for 1 month had 2.36%, 1.05%, 0.81%, 0.79%, and 0.49% CNK-20193 for glycine, mannitol, drug alone, povidone K-12, and lactose formulations, respectively. The formulations containing drug-mannitol, drug alone, and drug-lactose were selected for accelerated stability study based on statistical analysis. Recovery of CNK-20193 in these formulations was 1.22%, 1.00%, and 0.55%, respectively, when stored at 40 degrees C/75% relative humidity storage conditions for 3 months. Water vapor sorption analysis revealed weight gains of over 7%, 21%, and 24% for the mannitol, lactose, and drug alone formulations, respectively. Testing formulations with different concentrations of lactose by water vapor sorption indicated that CNK-20402 concentrations as low as 10% (wt/wt) could inhibit the recrystallization of lactose. The lactose-containing formulation exhibited the best stability among the formulations tested. The protective mechanism of lactose on the CNK-20402, based on water vapor sorption studies, is believed to be a result of (1) the drug-lactose interaction, and (2) competition between lactose and drug for the residual water in the formulation.

Chemistry, Pharmaceutical↗