Wet chemical syntheses of ultrafine multicomponent ceramic powders through gel to crystallite conversion

Coarse (BOn/2)-O-n+/xH(2)O (10

Bolaamphiphiles as carriers for siRNA delivery: From chemical syntheses to practical applications

In this study we have investigated a new class of cationic lipids - ``bolaamphiphiles'' or ``bolas'' - for their ability to efficiently deliver small interfering RNAs (siRNAs) to cancer cells. The bolas of this study consist of a hydrophobic chain with one or more positively charged head groups at each end. Recently, we reported that micelles of the bolas GLH-19 and GLH-20 (derived from vernonia oil) efficiently deliver siRNAs, while having relatively low toxicities in vitro and in vivo. Our previous studies validated that; bolaamphiphiles can be designed to vary the magnitude of siRNA shielding, its delivery, and its subsequent release. To further understand the structural features of bolas critical for siRNAs delivery, new structurally related bolas (GLH-58 and GLH-60) were designed and synthesized from jojoba oil. Both bolas have similar hydrophobic domains and contain either one, in GLH-58, or two, in GLH-60 positively charged head groups at each end of the hydrophobic core. We have computationally predicted and experimentally validated that GLH-58 formed more stable nano sized micelles than GLH-60 and performed significantly better in comparison to GLH-60 for siRNA delivery. GLH-58/siRNA complexes demonstrated better efficiency in silencing the expression of the GFP gene in human breast cancer cells at concentrations of 5 mu g/mL, well below the toxic dose. Moreover, delivery of multiple different siRNAs targeting the HIV genome demonstrated further inhibition of virus production. Published by Elsevier B.V.

A phenomenological model for the structure-composition relationship of the high Tc cuprates based on simple chemical principles

A simple phenomenological model for the relationship between structure and composition of the high Tc cuprates is presented. The model is based on two simple crystal chemistry principles: unit cell doping and charge balance within unit cells. These principles are inspired by key experimental observations of how the materials accommodate large deviations from stoichiometry. Consistent explanations for significant HTSC properties can be explained without any additional assumptions while retaining valuable insight for geometric interpretation. Combining these two chemical principles with a review of Crystal Field Theory (CFT) or Ligand Field Theory (LFT), it becomes clear that the two oxidation states in the conduction planes (typically d8 and d9) belong to the most strongly divergent d-levels as a function of deformation from regular octahedral coordination. This observation offers a link to a range of coupling effects relating vibrations and spin waves through application of Hund’s rules. An indication of this model’s capacity to predict physical properties for HTSC is provided and will be elaborated in subsequent publications. Simple criteria for the relationship between structure and composition in HTSC systems may guide chemical syntheses within new material systems.

Synthesis of Ba0.5Sr0.5(Ti0.80Sn0.20)O-3 prepared by the soft chemical method

Single-phase Ba0.5Sr0.5(Ti0.80Sn0.20)O-3 (BST:Sn) powders with perovskite structure were prepared by the soft chemical method. Infrared data indicates that the BST:Sn powder is carbonate free while Raman analysis has shown that the transversal (TO) and longitudinal (LO) optical modes tend to disappear with tin addition. The electron diffraction pattern of the BST:Sn powder showed an interplanar distance of 3.94 angstrom characteristic of the pseudo-cubic structure. (c) 2007 Elsevier B.V. All rights reserved.

Lanthanum doped BiFeO3 powders: Syntheses and characterization

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Magnetoelectric coefficient in strontium ruthenate buffered lanthanum modified bismuth ferrite thin films grown by chemical method

This paper focuses on the magnetoelectric coupling (ME) at room temperature in lanthanum modified bismuth ferrite thin film (BLFO) deposited on SrRuO 3-buffered Pt/TiO 2/SiO 2/Si(100) substrates by the soft chemical method. BLFO film was coherently grown at a temperature of 500 °C. The magnetoelectric coefficient measurement was performed to evidence magnetoelectric coupling behavior. Room temperature magnetic coercive field indicates that the film is magnetically soft. The maximum magnetoelectric coefficient in the longitudinal direction was close to 12 V/cmOe. Dielectric permittivity and dielectric loss demonstrated only slight dispersion with frequency due the less two-dimensional stress in the plane of the film. Polarization reversal was investigated by applying dc voltage through a conductive tip during the area scanning. We observed that various types of domain behavior such as 71 ° and 180° domain switching, and pinned domain formation occurred. Copyright © 2009 American Scientific Publishers All rights reserved.

Low-temperature synthesis of nanosized bismuth ferrite by the soft chemical method

This paper describes research on a simple low-temperature synthesis route to prepare bismuth ferrite nanopowders by the polymeric precursor method using bismuth and iron nitrates. BiFeO 3 (BFO) nanopowders were characterized by means of X-ray diffraction analyses, (XRD), Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy (Raman), thermogravimnetric analyses (TG-DTA), ultra-violet/vis (UV/Vis) and field emission scanning electron microscopy (FE-SEM). XRD patterns confirmed that a pure perovskite BiFeO 3 structure with a rhombohedral distorted perovskite structure was obtained by heating at 850 °C for 4 hours. Typical FT-IR spectra for BFO powders revealed the formation of a perovskite structure at high temperatures due to a metal-oxygen bond while Raman modes indicated oxygen octahedral tilts induced by structural distortion. A homogeneous size distribution of BFO powders obtained at 850 °C for 4 hours was verified by FE-SEM analyses. © 2012 Elsevier Ltd and Techna Group S.r.l.

Syntheses of bismuth titanate templates obtained by the molten salt method

Bismuth titanate templates (Bi4Ti3O12) were synthesized by the molten salt method in Na2SO4 and K2SO4 fluxes, using an amorphous Bi4Ti 3O12 precursor and a mechanically mixed Bi 2O3+TiO2 mixture as the starting materials. The templates were characterized by means of X-Ray Diffraction, FT-IR, FT-Raman, FEG-SEM and TEM. The templates are free of secondary phases and present orthorhombic structure with orientation in the c-plane. FT-IR suggests no traces of sulfate groups revealing that the molten salt synthesis was beneficial for elimination of inorganic species and for the arrangement of individual nanocrystals into ordered lattices. FEG-SEM analyses of BIT templates revealed that most of the grains were homogeneous with a length of 3.1 μm and a width of 0.3 μm and had plate-like morphology. TEM investigations show that the c-axis of the perovskite units is parallel to the thickness direction of the grains and no liquid-phase was formed during BIT phase formation. © 2013 Elsevier Ltd and Techna Group S.r.l.

Stepwise engineering of a Pichia pastoris D-amino acid oxidase whole cell catalyst

Trigonopsis variabilis D-amino acid oxidase (TvDAO) is a well characterized enzyme used for cephalosporin C conversion on industrial scale. However, the demands on the enzyme with respect to activity, operational stability and costs also vary with the field of application. Processes that use the soluble enzyme suffer from fast inactivation of TvDAO while immobilized oxidase preparations raise issues related to expensive carriers and catalyst efficiency. Therefore, oxidase preparations that are more robust and active than those currently available would enable a much broader range of economically viable applications of this enzyme in fine chemical syntheses. A multi-step engineering approach was chosen here to develop a robust and highly active Pichia pastoris TvDAO whole-cell biocatalyst. As compared to the native T. variabilis host, a more than seven-fold enhancement of the intracellular level of oxidase activity was achieved in P. pastoris through expression optimization by codon redesign as well as efficient subcellular targeting of the enzyme to peroxisomes. Multi copy integration further doubled expression and the specific activity of the whole cell catalyst. From a multicopy production strain, about 1.3 x 103 U/g wet cell weight (wcw) were derived by standard induction conditions feeding pure methanol. A fed-batch cultivation protocol using a mixture of methanol and glycerol in the induction phase attenuated the apparent toxicity of the recombinant oxidase to yield final biomass concentrations in the bioreactor of >or= 200 g/L compared to only 117 g/L using the standard methanol feed. Permeabilization of P. pastoris using 10% isopropanol yielded a whole-cell enzyme preparation that showed 49% of the total available intracellular oxidase activity and was notably stabilized (by three times compared to a widely used TvDAO expressing Escherichia coli strain) under conditions of D-methionine conversion using vigorous aeration. Stepwise optimization using a multi-level engineering approach has delivered a new P. pastoris whole cell TvDAO biocatalyst showing substantially enhanced specific activity and stability under operational conditions as compared to previously reported preparations of the enzyme. The production of the oxidase through fed-batch bioreactor culture and subsequent cell permeabilization is high-yielding and efficient. Therefore this P. pastoris catalyst has been evaluated for industrial purposes.

Antimicrobial Peptides with Potential for Biofilm Eradication: Synthesis and Structure Activity Relationship Studies of Battacin Peptides

We report on the first chemical syntheses and structureactivity analyses of the cyclic lipopeptide battacin which revealed that conjugation of a shorter fatty acid, 4-methyl-hexanoic acid, and linearization of the peptide sequence improves antibacterial activity and reduces hemolysis of mouse blood cells. This surprising finding of higher potency in linear lipopeptides than their cyclic counterparts is economically beneficial. This novel lipopeptide was membrane lytic and exhibited antibiofilm activity against Pseudomonas aeruginosa, Staphylococcus aureus, and, for the first time, Pseudomonas syringe pv. actinidiae. The peptide was unstructured in aqueous buffer and dimyristoylphosphatidylcholine-polymerized diacetylene vesicles, with 12% helicity induced in 50% v/v of trifluoroethanol. Our results indicate that a well-defined secondary structure is not essential for the observed antibacterial activity of this novel lipopeptide. A truncated pentapeptide conjugated to 4-methyl hexanoic acid, having similar potency against Gram negative and Gram positive pathogens was identified through alanine scanning.

滇金足草、凋缨菊和长喙吴萸的化学成分研究

本论文对滇金足草（Goldfussia yunnanensis）、凋缨菊（Camchaya loloana）和长喙吴萸（Evodia vestia）的化学成分进行了研究，通过色谱分离得到40个化合物。主要基于波谱数据鉴定了它们的结构，其中10个为新化合物。 1．从滇金足草地上枝叶的95%乙醇提取物中共分离鉴定了16个化合物：泽漆内酯A（1）、18-羟基泽漆内酯A（2）、18-氧代泽漆内酯A（3）、18-羟基-3-O-β-D-吡喃葡萄糖-泽漆内酯A（4）、3-O-β-D-吡喃葡萄糖-泽漆内酯A（5）、3-O-β-D-吡喃半乳糖-泽漆内酯A（6）、6-E-肉桂酰哈巴俄苷（7）、E-哈巴俄苷（8）、5，6-异亚丙二氧基哈巴俄苷（9）、β-谷甾醇（10）、β-胡萝卜苷（11）、齐墩果酸（12）、肉桂酸（13）、麦角固醇（14）、硬脂酸（15）和丁二酸（16）。其中2-7为新化合物。5，6-异亚丙二氧基哈巴俄苷（9）以人工产物形式得到。 2．从凋缨菊地上枝叶的95%乙醇提取物中分离并鉴定了13个化合物：凋缨菊内酯A~C (17-19)、1β-乙酰基凋缨菊内酯C(20)、b-谷甾醇（10）、β-胡萝卜苷（11）、羽扇豆醇（21）、桦木醇（22）、桦木酸（23）、芥子醇（24）、紫丁香苷（25）、咖啡酸（26）和熊果酸（27）。其中化合物17-20为桉叶烷内酯类新化合物。化合物17、18、20对细胞株HepG2的GI50依次为7.80、7.08、4.99 µg/mL。 3．从长喙吴萸（E. vestia）地上枝叶的95%乙醇提取物中分离并鉴定了13个化合物：佛手内酯（28）、花椒毒素（29）、异茴芹内酯（30）、七叶内酯（31）、东莨宕素（32）、瑞香素（33）、异紫花前胡内酯(34)、茵芋碱（35）、山刈碱（36）、白鲜碱（37）、黄柏酮（38）、柠檬苦素（39）和对羟基苯甲醛（40）。 4．综述了1990—2007年期间从菊科植物中发现的桉叶烷-12，6内酯的化学结构、生物活性、生物转化及化学合成方面的研究进展。 Phytochemical investigation on Goldfussia yunnanensis, Camchaya loloana, and Evodia vestia, led to the isolation of 40 compounds, 10 of which were new ones. 1. Six new compounds were isolation from 95% ethanolic extract of the aerial parts of G. yunnanensis, and identified as 18-hydroxyhelioscopinolide A (2), 18-oxohelioscopinolide A (3), 18-hydroxy-3-O-β-D-glucopyranosylhelioscopinolide A (4), 3-O-β-D-glucopyranosylhelioscopinolide A (5),3-O-β-D-Galactopyranosyl helioscopinolide A (6), 6-O-trans-cinnamoyl E-harpagoside (7). The known compounds isolated were helioscopinolide A (1), E-harpagoside A (8), 5,6-isopropylidene E-harpagoside A (9), β-sitosterol (10), β-daucosterol (11), oleanolic acid (12), cinnamic acid (13), ergosterol (14), stearic acid (15) and succinic acid (16). Compound 9 was an artifact. 2. Four new compounds, loloanolides A – C (17 - 19) and 1β-acetoxy-loloanolide C (20), were isolation from 95% ethanolic extract of the aerial parts of C. loloana. The known ones were β-sitosterol (10), β-daucosterol (11), lupeol (21), betulin (22), betulinic acid (23), sinapyl (24), syringin (25), caffeic acid (26) and ursolic acid (27). The GI50 values of compounds 17, 18 and 20 to HepG2 cell line were 7.80, 7.08 and 4.99 µg/mL, respectively. 3. Thirteen were isolated from 95% ethanolic extract of the aerial parts of E. vestia for the first time. They were determined to be bergapten (28), xanthotoxin (29), isopimpinellin (30), esculetin (31), scopoletin (32), daphnetin (33), marmesin (34), skimmianine (35), confusameline (36), dictamine (37), obacunone (38), limonin (39) and p-hydroxy phenyl aldehyde (40). 4. The structures, biological activities, biotransformation and chemical syntheses of eudesmane-12, 6-olides from the Asteraceae during 1990-2007 were reviewed.

Simultaneous synthesis of gold nanoparticles and conducting poly(3,4-ethylenedioxythiophene) towards optoelectronic nanocomposites

In this paper, a new method for obtaining poly(3,4-ethylenedioxythiophene) (PEDOT/PSS)/gold nanocomposites is described. In a first step, PEDOT/PSS gold nanoparticle aqueous dispersions were obtained by simultaneous chemical synthesis of PEDOT and gold nanoparticles in the presence of PSS that acts as a stabilizer. In a second step, these PEDOT/PSS gold nanoparticle dispersions were used to formulate nanocomposites by mixing the initial dispersion with commercially available PEDOT/PSS aqueous dispersion. Nanocomposite thin films, obtained by casting these dispersions, present an intimate contact between the inorganic and organic components

Intense photoluminescence emission at room temperature in calcium copper titanate powders

A study was undertaken about the structural and photoluminescent properties at room temperature of CaCu3Ti4O12 (CCTO) powders synthesized by a soft chemical method and heat treated between 300 and 800 °C. The decomposition of precursor powder was followed by thermogravimetric analysis (TG-DTA), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman) and photoluminescence (PL) measurements. XRD analyses revealed that the powders annealed at 800 °C are becoming ordered and crystallize in the cubic structure. The most intense PL emission was obtained for the sample calcined at 700 °C, which is not highly disordered (300-500 °C) and neither completely ordered (800 °C). From the spectrum it is clearly visible that the lowest wavelength peak is placed around 480 nm and the highest wavelength peak at about 590 nm. The UV/vis absorption spectroscopy measurements showed the presence of intermediate energy levels in the band gap of structurally disordered powders. © 2012 Elsevier Ltd and Techna Group S.r.l.

Effect of soaking time on the photoluminescence properties of cerium oxide nanoparticles

The structural and photoluminescence properties at room temperature of CeO2 nanoparticles synthesized by a microwave-assisted hydrothermal method (MAH) under different soaking times on KOH mineralizer added to a cerium ammonium nitrate aqueous solution were undertaken. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman) and photoluminescence (PL) measurements were employed. XRD revealed that the nanoparticles are free of secondary phases and crystallize in the cubic structure. The UV/vis absorption spectroscopy suggested the presence of intermediate energy levels in the band gap of structurally ordered powders. The most intense PL emission was obtained for nanoparticles which represent a lower particle size. © 2013 Elsevier Ltd and Techna Group S.r.l.

Photoluminescence properties of praseodymium doped cerium oxide nanoparticles

The structural and photoluminescent properties at room temperature of CeO2 nanoparticles synthesized by a Microwave-Assisted Hydrothermal Method (MAH) under different praseodymium contents was undertaken. X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), UV-vis Spectroscopy (UV-vis), Fourier Transform Raman (FT-Raman) and Photoluminescence (PL) measurements were employed. XRD revealed that the nanoparticles are free of secondary phases and crystallize in the cubic structure while FT-Raman revealed a typical scattering mode of fluorite type. The UV/vis absorption spectroscopy suggested the presence of intermediate energy levels in the band gap of structurally ordered powders. The most intense PL emission was obtained for nanoparticles which represent a lower particle size. © 2013 Elsevier Ltd and Techna Group S.r.l.