Influence of alumina air-abrasion for highly translucent partially stabilized zirconia on flexural strength, surface properties, and bond strength of resin cement

Abstract Objective This study aims to evaluate the influence of different air-abrasion pressures and subsequent heat treatment on the flexural strength, surface roughness, and crystallographic phases of highly translucent partially stabilized zirconia (Y-PSZ), and on the tensile bond strength of resin cement to Y-PSZ. Methodology Fully sintered zirconia specimens were ground with SiC paper (control) and/or air-abraded with 50 µm particles of alumina at 0.1, 0.15, 0.2, or 0.3 MPa or left as-sintered. After air-abrasion at 0.2 MPa (0.2AB), additional specimens were then heated to 1500°C, and held for one hour at this temperature (0.2AB+HT1h). Flexural strength and surface roughness were evaluated. Crystalline phase identification was also carried out using X-ray diffraction. Bonded zirconia specimens with self-adhesive resin cement were stored in distilled water at 37°C for 24 h, either with or without aging (thermal cycling 4-60°C/20000). Results were analyzed statistically by ANOVA and Tukey-Kramer tests. Results The flexural strength decreased with the increase in air-abrasion pressure, while in contrast, the surface roughness increased. The lowest flexural strength and the highest roughness value were found for the 0.2AB and 0.3AB groups, respectively. All groups contained cubic-, tetragonal ( t )-, and rhombohedral ( r )-ZrO2 phases with the exception of the as-sintered group. Upon increasing the air-abrasion pressure, the relative amount of the r -ZrO2 phase increased, with a significant amount of r -ZrO2 phase being detected for the 0.2AB and 0.3AB groups. The 0.2AB+HT1h group exhibited a similar flexural strength and t -ZrO2 phase content as the as-sintered group. However, the 0.2AB group showed a significantly higher tensile bond strength (p<0.05) than the 0.2AB+HT1h group before and after aging. Conclusion Micromechanical retention by alumina air-abrasion at 0.2 MPa, in combination with chemical bonding of a resin to highly translucent Y-PSZ using a MDP-containing resin cement may enable durable bonding.

Polybrominated diphenyl ethers with broad spectrum antibacterial activity from the Indonesian marine sponge Lamellodysidea herbacea

The marine sponge Lamellodysidea herbacea is one of the marine organisms containing unique organobromine molecules polybrominated diphenyl ethers (PBDEs) which have diverse biological activities. Compounds 1−4 have been successfully isolated and their structures were elucidated using nuclear magnetic resonance (NMR) spectroscopy, single-crystal x-ray diffraction, and comparison with data in literature. Compound 1, C12H6 O4 Br6 , was isolated in gram quantity (1.35 g) and elucidated as 2,3,4,5-tetrabromo-6-(3ʹ,5ʹ-dibromo-2ʹ-hydroxyphenoxy)phenol after NMR and X-ray analysis. Compound 1 takes a twist-like conformation with torsion angle ϕ1 = 27.7 (6)°; ϕ2 = 86.5 (5)°, while the angle of the ether bond is 117.5°. Compounds 2−4 were elucidated as 2,3,5-tribromo-6-(3ʹ,5ʹdibromo-2ʹ-hydroxyphenoxy)anisole, 2,3,5-tribromo-6-(3ʹ,5ʹ-dibromomethoxyphenoxy) phenol, 2,3,5-tribromo-6- (3ʹ,5ʹ-hydroxyphenoxy)phenol, respectively. Antibacterial evaluation of 1−4 on Gram-positive and Gram-negative pathogens showed that the potent activity was at 0.08 µg/disk, 12 ± 0 mm (Staphylococcus aureus ATCC 6538); 6.25 µg/disk, 10 ± 0 mm (Klebsiella pneumoniae); and 50 µg/disk, 12 ± 0 mm (ampicillin-resistant Escherichia coli). Compounds 1, 2, and 4 showed ichthyotoxicity (zebrafish embryos, Danio rerio) at a level of LC50 >10 µg/ml [dead, 48 hours postfertilization (hpf)]. This is the first report that compound 4 inhibits the growth of antibiotic-resistant bacteria.

Rational design of GRK2 inhibitors for the treatment of heart failure / 中国药理学与毒理学杂志

G protein-coupled receptors (GPCRs) convert extracellular stimuli in the form of hormones, odorants and light into profound changes in cell homeostasis. Their timely desensitization is critical for cells to rapidly respond to changes in their environment and to avoid damage from sustained signaling. Seven GPCR kinases (GRKs) phosphorylate and regulate the activity of most of the ~800 GPCRs in the human genome. Although GRKs normally play an adaptive role, in conditions such as chronic heart failure they are overexpressed and linked to disease progression. GRK2 and GRK5 have thus become important targets for the treatment of heart failure and pathological cardiac hypertrophy, respectively. Our lab has determined atomic structures representing all three vertebrate GRK subfamilies, and is now in the midst of a campaign to develop selective inhibitors of these enzymes using structure-based rational design. We have identified the FDA approved drug paroxetine as a selective GRK2 inhibitor, determined the crystal structure of the GRK2·paroxetine complex and, in collaboration with the Koch lab, showed that the drug improves contractility in myocytes and, most impressively, recovery in post-myocardial infarcted mice. Since then, we have identified additional chemical scaffolds that exhibit even higher potency and/or selectivity for GRK5. Using a ″hybrid″ inhibitor design approach we have generated GRK selective chemical probes that exhibit improved potency and stability and are able to increase inotropy and dampen the hypertrophic response in cardiomyocytes and small animal models. Structural analysis has revealed the molecular basis for selectivity and potency in many of these compounds, allowing for the design of future generations of GRK chemical probes.

Studies on sesquiterpene lactones from Carpesium faberi / 中国中药杂志

By using various chromatographic techniques,18 sesquiterpene lactones were isolated from the acetone extract of Carpesium faberi. Their structures were identified on the basis of comprehensive spectroscopic data, involving 2 carabrane sesquiterpenoids [carabrone(1), 4R-carabrol(2)], 3 eudesmane sesquiterpenoids [granilin(3), 3-epi-isotelekin(4), 1α-hydroxypinatifidin(5)], 8 guaiane sesquiterpenoids [4β,10α-dihydroxy-5α(H)-1,11(13)-guaidien-8α,12-olide(6), 8-epi-helenium lactone(7), 4-epi-isoinuviscolide(8), 9β,10β-epoxy-4α-hydroxy-1β-H,11α-H-guaian-8α,12-olide(9), 4α,10α-dihydroxy-1β(H),5β(H)-guaian-11-(13)-en-8α,12-olide(10), 4α-hydroxy-9β,10β-epoxy-11β-H,5α-H-guaian-11(13)-en-8α,12-olide(11), 4α-hydroxy-1β,5α,11α-H-guaian-9(10)-en-8α,12-olide(12), inuviscolide(13)], 1 pseudoguaiane sesquiterpenoid [(+)-confertin(14)], 3 germacrane sesquiterpenoids [madolin B(15), carabrolactone A(16),11(13)-dehydroivaxillin(17)], 1 xanthane sesquiterpenoid [tomentosin(18)]. Furthermore, the absolute configuration of 1 was confirmed by Cu-Kα X-ray crystallographic analysis,and the R-configuration of the chiral center at C-4 in 2 was established by the modified Mosher's method.The compounds 2-5, 7 and 9-15 were isolated from this plant for the first time, and compounds 4-5, 7, and 12-15 were isolated from this genus for the first time.In addition, the neurotrophic activity of compounds 1-3, 6 and 17 were evaluated by morphological observation and statistical analysis of cells differentiation, using rat pheochromocytoma(PC12)cells as a model system. However, all compounds were inactive.

In Silico Inhibitory Activity against Caspase 3 by Zinc (II) Coordinated Complexes.

Aims: The presented research paper is aimed to prevalence of apoptosis for the first time by using in silico molecular docking and simulation using caspase-3 zymogen and zinc-coordinated compounds. Antioxidant activities of the coordinated complexes were compared to the positive controls (BHT and ascorbic acid). Study design: Molecular docking analysis was performed by using Autodock 4.2, setting at 150x140x110 Gridbox, center at -57.616, 31.092, 88.666 with 0.375 Å spacing. Their antioxidant activity was tested by FRAP and DPPH assay. Place and Duration of Study: Department of Chemistry and department of molecular medicine, Faculty of Medicine, University of Malaya laboratories between January 2014 – July 2014 Methodology: Compounds derived from zinc(II) ion give rise to coordination complexes exhibited CHN, NMR (1H & 13C) and FT-IR spectra consistent with the proposed structures. Based on the x-ray crystal structure, one of the derivatives is a mononuclear square-pyramidal metal complex, with τ value of 0.35. The molecular docking simulation formed between compounds and caspase 3 showed the ligands bind to the active-site gorge well positioned in the active-site gorge. Results: The residues that have been involved in this protein-ligand interaction docked well by using Autodock 4.2, setting at 150x140x110 Gridbox, center at -57.616, 31.092, 88.666 with 0.375 Å spacing in the hydrophobic pocket. Their antioxidant activity tested revealed their FRAP assay values of 531.11±0.021 and 1886.11±0.008 higher than value of 187.3±2.6 shown by BHT used as standard. The compounds showed IC50 values 21.50±0.009 and 14.80±0.002 lower than ascorbic acid with an IC50 value of 2.26±0.001 μg/mL. Conclusion: Synthesized zinc(II) complexes have been confirmed to inhibit the activity of caspase 3 both in silico and in vitro and were tested for antioxidant activity by both FRAP and DPPH methods.

Crystal structure of Vibrio cholerae HutX protein / 第二军医大学学报

Objective To obtain purified Vibrio cholerae HutX and its diffraction data. Methods Protein HutX was obtained by gene cloning and protein expression, purified by nickcl sepharose affinity chromatography, anion exchange chromatography (source Q), and molecular sieve chromatography (Superdex 200), and identified by Western blotting analysis. Then the obtained protein was subjected to crystallization condition screening and hanging drop optimization. The obtained crystal structure was analyzed by X-ray diffraction method. Results Western blotting analysis indirectly indicated that the obtained protein was HutX protein. Then the HutX crystal and its diffraction data were obtained in the present study. Conclusion The findings of the present study pave a way for future research on the crystal structure and function of HutX protein and its role in heme utilization of Vibrio cholerae.

A model for the reaction mechanism of the transglutaminase 3 enzyme

Transglutaminase enzymes (TGases) catalyze the calcium dependent formation of an isopeptide bond between protein-bound glutamine and lysine substrates. Previously we have shown that activated TGase 3 acquires two additional calcium ions at site two and three. The calcium ion at site three results in the opening of a channel. At this site, the channel opening and closing could modulate, depending on which metal is bound. Here we propose that the front of the channel could be used by the two substrates for enzyme reaction. We propose that the glutamine substrate is directed from Trp236 into the enzyme, shown by molecular docking. Then a lysine substrate approaches the opened active site to engage Trp327, leading to formation of the isopeptide bond. Further, direct comparisons of the structures of TGase 3 with other TGases have allowed us to identify several residues that might potentially be involved in generic and specific recognition of the glutamine and lysine substrates.

Spatial organization of catalase proteins.

The three-dimensional structure of the heme-containing fungal catalase from Penicillium vitale (m.m. 2,80,000) has been studied by X-ray analysis at 2·0 A resolution. The molecule is tetramer, each subunit contains 670 aminoacid residues identified to construct “X-ray” primary structure. The subunit is built of three compact domains and their connections. The first domain of about 350 residues contains a β-barrel flanked by helices, the second domain of 70 residues is formed by four helices and the third one is composed of 150 residues and is topologically similar to flavodoxin. The active site including heme is deeply buried near the β-barrel. A comparison of the structure of catalase from Penicillium vitale with that of beef liver catalase revealed very close structural homology of the first and the second domain, but the third domain is entirely absent in beef liver catalase. A catalase from thermophillic bacteria Thermus thermophilus (m.m. 2,10,000) has been first isolated, crystallized and studied by X-ray analysis. Crystals are cubic, space group is P213, a = 133·4 Å. The molecule is a hexamer with trigonal symmetry 32. The electron density map at 3 Å resolution made it possible to trace the polypeptide chain. The main structural motif is formed by four near parallel helices. There is no heme in Thermus thermophilus catalase, the active site is between the four helices and contains two manganese ions.