OBJECTIVEThe aim of this study is to analyze the three-dimensional crystal structure of SMU.2055 protein, a putative acetyltransferase from the major caries pathogen Streptococcus mutans (S. mutans). The design and selection of the structure-based small molecule inhibitors are also studied.

METHODSThe three-dimensional crystal structure of SMU.2055 protein was obtained by structural genomics research methods of gene cloning and expression, protein purification with Ni²⁺-chelating affinity chromatography, crystal screening, and X-ray diffraction data collection. An inhibitor virtual model matching with its target protein structure was set up using computer-aided drug design methods, virtual screening and fine docking, and Libdock and Autodock procedures.

RESULTSThe crystal of SMU.2055 protein was obtained, and its three-dimensional crystal structure was analyzed. This crystal was diffracted to a resolution of 0.23 nm. It belongs to orthorhombic space group C222(1), with unit cell parameters of a = 9.20 nm, b = 9.46 nm, and c = 19.39 nm. The asymmetric unit contained four molecules, with a solvent content of 56.7%. Moreover, five small molecule compounds, whose structure matched with that of the target protein in high degree, were designed and selected.

CONCLUSIONProtein crystallography research of S. mutans SMU.2055 helps to understand the structures and functions of proteins from S. mutans at the atomic level. These five compounds may be considered as effective inhibitors to SMU.2055. The virtual model of small molecule inhibitors we built will lay a foundation to the anticaries research based on the crystal structure of proteins.

Bacterial Proteins ; chemistry ; Cloning, Molecular ; Crystallization ; Crystallography, X-Ray ; Dental Caries ; Humans ; Streptococcus mutans ; chemistry ; X-Ray Diffraction

Using chrysin as a leading compound, intermediate 5, 7-dihydroxy-6, 8-bis (hydroxymethyl) flavone (1) was synthesized by hydroxymethylation. The intermediate reacted with different alcohols to afford 5, 7-dihydroxy-6, 8-bis ( methoxymethyl) flavone (2), 6, 8-bis (ethoxymethyl) -5, 7dihydroxyflavone (3), 6, 8-bis-(butoxymethyl)-5, 7-dihydroxyflavone (4), 6, 8-bis (pentyloxymethyl) -5,7-dihydroxy flavone (5) and 6, 8-bis-(ethoxymethyl) -5-hydroxy-7-methoxyflavone (6). These compounds were characterized by IR, 1H NMR, 13C NMR and element analysis. The crystal structure of 6 was determined by X-ray crystal diffraction. The interaction of the derivatives with CT-DNA was studied by fluorescent spectroscopy. According to the Stern-Volmer equation, the quenching constants of the compounds 1 - 4 were measured, separately, they were K(q1) = 9.71 x 10(3) L x mol(-1), K(q2) = 2.25 x 10(4) L x mol(-1), K(q3) = 1.03 x 10(4) L x mol(-1) and K(q4) = 7.96 x 10(3) L x mol(-1). Compounds 1-4 showed higher binding affinity with DNA than chrysin did. The results provided the experimental basis for developing a more effective flavonoid and worthing further thoroughly study.
Animals ; Crystallography ; DNA ; metabolism ; Drug Interactions ; Flavones ; chemical synthesis ; chemistry ; Flavonoids ; chemical synthesis ; chemistry ; metabolism ; Magnetic Resonance Spectroscopy ; Molecular Structure ; X-Ray Diffraction

Transforming technology for semi-synthesized isocorydione from the natural product ofisocorydine was studied. The factors affecting on the reaction yield were investigated. UV spectrophotometry was used to indicate the semi-synthesized yield of isocorydione. The optimum reaction conditions were determined as following: reacting for 12 h in the solution of sodium dihydrogen phosphate at pH 10, the temperature was 25 degrees C and the ratio of isocorydine to Fremy's radical was 1 : 2. Under the optimum conditions, the yield could reach up to 50.0%. The molecular structure of isocorydione was elucidated by X-ray single-crystal diffraction analysis for the first time.
Antineoplastic Agents, Phytogenic ; chemical synthesis ; chemistry ; isolation & purification ; Aporphines ; chemical synthesis ; chemistry ; isolation & purification ; Crystallography, X-Ray ; Hydrogen-Ion Concentration ; Molecular Structure ; Nitroso Compounds ; Oxidation-Reduction ; Papaveraceae ; chemistry ; Plants, Medicinal ; chemistry ; Spectrophotometry, Ultraviolet ; Temperature ; X-Ray Diffraction

Algorithms ; Carrier Proteins ; chemistry ; Crystallography, X-Ray ; Humans ; Magnetic Resonance Spectroscopy ; Molecular Dynamics Simulation ; Nuclear Proteins ; chemistry ; Principal Component Analysis ; Protein Structure, Tertiary ; Proteins ; chemistry ; Scattering, Small Angle ; X-Ray Diffraction ; methods

PURPOSE: The purpose of the present study was to evaluate the effect of thermocycling and mechanical loading on the biaxial flexural strength and the phase transformation of one Ce-TZP/Al2O3 and two Y-TZP core materials. MATERIALS AND METHODS: Thirty disc-shaped specimens were obtained from each material. The specimens were randomly divided into three groups (control, thermocycled, and mechanically loaded). Thermocycling was subjected in distilled water for 10000 cycles. Mechanical loading was subjected with 200 N loads at a frequency of 2 Hz for 100000 times. The mean biaxial flexural strength and phase transformation of the specimens were tested. The Weibull modulus, characteristic strength, 10%, 5% and 1% probabilities of failure were calculated using the biaxial flexural strength data. RESULTS: The characteristic strengths of Ce-TZP/Al2O3 specimens were significantly higher in all groups compared with the other tested materials (P<.001). Statistical results of X-ray diffraction showed that thermocycling and mechanical loading did not affect the monoclinic phase content of the materials. According to Raman spectroscopy results, at the same point and the same material, mechanical loading significantly affected the phase fraction of all materials (P<.05). CONCLUSION: It was concluded that thermocycling and mechanical loading did not show negative effect on the mean biaxial strength of the tested materials.
Spectrum Analysis, Raman ; Water ; X-Ray Diffraction

PURPOSE: This study investigated the influence of surface conditioning procedures and repeated firings on monoclinic content and strength of zirconia before cementation. MATERIALS AND METHODS: Sintered bar-shaped zirconia specimens were subjected to no surface treatment (control), air abrasion, or grinding (n=21). Their roughness was evaluated using a profilometer, and microscope analysis was performed on one specimen of each group. Then, 2 or 10 repeated firings (n=10) were executed, the monoclinic content of specimens was analyzed by X-ray diffraction, and a three-point flexural strength test was performed. Surface roughness values were compared using one-way analysis of variance (ANOVA) and Tukey honestly significant difference (HSD) tests, the monoclinic content values were tested using Kruskal-Wallis and Mann-Whitney U tests, and the flexural strength values were tested using two-way ANOVA and Tukey HSD tests (P=.05). Spearman's correlation test was performed to define relationships among measured parameters. RESULTS: Surface-treated specimens were rougher than untreated specimens and had a higher monoclinic content (P<.005), and the relationship between roughness and monoclinic content was significant (P<.000). Neither surface treatment nor firing significantly affected the flexural strength, but Weibull analysis showed that for the air-abraded samples the characteristic strength was significantly lower after the 10th firing than after the 2nd firing. CONCLUSION: After firing, a negligible amount of monoclinic content remained on the zirconia surfaces, and rougher surfaces had higher monoclinic contents than untreated surfaces. Multiple firings could be performed if necessary, but the fracture probability could increase after multiple firings for rougher surfaces.
Cementation ; Ceramics ; Fires* ; X-Ray Diffraction

OBJECTIVETo construct four different micro- and nano-phase titanium film models and investigate the characteristics of their surface micro-topography.

METHODSFour different titanium films were prepared on commercial titanium discs, by direct current magnetron sputtering, at ambient, 100, 250, 380 degrees C substrate temperature, respectively. Their surface topography and crystal sizes were investigated using atomic force microscope (AFM) and X-ray diffraction (XRD). The size of granule and surface roughness in different group was calculated and compared.

RESULTSAll samples were covered by a thin film consisting of dense round or ovaloid granules. The granules and crystals was growing as the substrate temperature increasing. The Ti substrate had greater effect on the surface topography of film compared with Si substrate. This kind of complex topography caused the surface roughness of Ti substrate group decreased as the granules growing.

CONCLUSIONIn our study, four different micro- and nano-phase titanium film models were constructed for our coming investigation of their topographical influence on biological reaction of proteins and cells. Basic data on surface features was obtained for next in vitro and in vivo experiment.

Surface Properties ; Titanium ; X-Ray Diffraction

BACKGROUNDFrozen or dried corneal grafts are commonly used for stromal transplantation such as lamellar keratoplasty (full or partial thickness), keratophakia, epikeratophakia. Structural properties are important for the final optical results of these surgeries but the effects of freezing/thawing and drying/rehydration on the properties of the stroma are known little compared with the corneal endothelium, mainly because of lack of non-invasive technique to evaluate the stromal structure. This study aimed to investigate the swelling and structural properties of the bovine corneal stroma following freezing or drying by X-ray diffraction which was a non-invasive technique and could give ultra-structural information in hydrated tissues.

METHODSBovine corneas were either frozen at -40 degrees C or dried to constant weight in a dessicator over silica gel. Swelling was carried out by placing the corneas into dialysis tubing and equilibrating them against various concentrations of polyethylene glycol (PEG) to obtain a range of tissue hydrations. This method minimises the loss of soluble tissue components during the swelling process. Synchrotron X-ray diffraction was used to measure the average intermolecular spacing, the interfibrillar spacing and the fibril diameter as a function of hydration. Changes in light scattering were detected using a microdensitometer.

RESULTSFreezing and thawing of the cornea caused an increase in light scattering by 63.9% at tissue hydration (H) = 3.4, and by 50.0% at H = 4.9. Repeated freezing and thawing causes further increased by 38.9% at the second time and another 36.0% at the third time (P < 0.05). There was a tendency for both the frozen and the dried corneas to lose some swelling ability, achieving hydrations respectively of 10% and 18% below those of fresh corneas at 0 PEG. There were no changes in the fibril diameters, interfibrillar or intermolecular spacings as measured by X-ray diffraction in the equilibrated fresh, pre-frozen and pre-dried corneas.

CONCLUSIONSThe increase in light scattering and the loss of swelling ability after freezing and thawing probably results from structural changes following the close association of the collagen molecules and fibrils whilst the tissue is in the dry or frozen state. Some unknown changes in the extracellular matrix between the collagen fibrils may also play a role in the light scattering. The equilibration technique may improve the quality of rehydrated corneal graft or lenticules used for corneal surgeries.

Animals ; Cattle ; Cornea ; chemistry ; Desiccation ; Freezing ; X-Ray Diffraction

The technique of liquisolid compress is a new technique developed in 1990s, which was considered to be the most promising technique to improve the dissolution of water-insoluble drugs. In this article, tanshinone II(A) and the extracts of the ester-solubility fractions were chosen as the model drugs to evaluate the effects of the liquisolid technique for enhancement of dissolution properties of tanshinone II(A). Several liquisolid tablets (LS) formulations containing different dosage of drugs and various liquid vehicle were pre-pared and for all the formulations, microcrystalline cellulose and silica were chosen as the carrier and coating materials to evaluate their flow properties, such as angle of repose, Carr's compressibility index and Hausner's ratio. The interaction between drug and excipients in prepared LS compacts were studied by differential scanning calorimetry(DSC) and X-ray powder diffraction (XRPD). The dissolution curves of tanshinone II(A) from liquisolid compacts were investigated to determine the technique's effect in improving the dissolution of tanshinone II(A) and its impacting factors. According to the results, the dissolution increased with the rise in the dissolution of the liquid-phase solvent. The R-value and drug dosage can significantly affect the drug release, but with less impact on active fractions. This indicated that liquisolid technique is a promising alternative for improvement of dissolution property of water-soluble drugs, and can make a synergistic effect with other ester-soluble constituents and bettern improve the release of tanshinone II(A). Therefore, the technique of liquisolid compress will have a better development prospect in traditional Chinese medicines.
Calorimetry, Differential Scanning ; Diterpenes, Abietane ; chemistry ; Solubility ; X-Ray Diffraction

The aim of this paper is to clarify the mineral origin of traditional Chinese medicine (TCM) Yangqishi and Yinqishi and guide identification of the both, by X-ray diffraction (XRD) Fourier patterns. Morphological identification and conventional physical and chemical analysis wee used to identify 22 batches of Yangqishi and Yinqishi. It used XRD Fourier patterns which has been collected from sample powders to analyze phase composition. It has been found experimentally that the mineral origin of Yinqishi is Talc schist and the mineral origin of Yangqishi is tremolite and actinolite. The results also showed that the method using XRD can get not only an accurate but also rapid identification of Yangqishi and Yinqishi. There are many differences in medicinal properties, efficacy, indications and composition of Yangqishi and Yinqishi, so be careful not to mix them up.
Asbestos, Amphibole ; chemistry ; Drugs, Chinese Herbal ; chemistry ; X-Ray Diffraction