bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of progesterone heterocyclic derivatives of potential antimicrobial activity
Authors: Mohareb Rafat , Hana Hanaa 
Published: April 2008

Synthesis of progesterone heterocyclic derivatives of potential antimicrobial activityThe aim of this work was to synthesize steroidal heterocycles and to elucidate the potential role of these compounds as antimicrobial agents. The synthesis of steroidal heterocycles containing the pyrazole, isoxazole, thiazole, pyrane, pyridine, pyridazine, or benzopyrane ring attached to the pregnene nucleus is reported. Progesterone (1) reacts with dimethyl formamide dimethyl acetal to form enamine2. Heterocyclization of2with hydrazines, hydroxylamine, glycine, ethyl acetoacetate or cyanomethylene afforded novel steroidal heterocyclic derivatives. Thein vitroantimicrobial evaluation showed that all synthesized compounds show activity against the used strains of Gram positive bacteria and fungi.
New steroidal derivatives synthesized using 3β-hydroxyandrosten-17-one as starting material
Authors: Abd El-Latif Nehad , Abdulla Mohamed , Amr Abd 
Published: April 2008

New steroidal derivatives synthesized using 3β-hydroxyandrosten-17-one as starting materialIn this study, we synthesized some new substituted steroidal derivatives using 3β-hydroxyandrosten-17-one (dehydroepiandrosterone) as starting material. The synthesized steroidal derivatives1-11were evaluated for their androgenic-anabolic activities compared to testosterone as positive control. Details of the synthesis, spectroscopic data and toxicity (LD50) of synthesized compounds are reported.
Solid dispersion of meloxicam: Factorially designed dosage form for geriatric population
Authors: Pathak Deepa , Dahiya Sunita , Pathak Kamla 
Published: April 2008

Solid dispersion of meloxicam: Factorially designed dosage form for geriatric populationThe objective of the present work was to improve the dissolution properties of the poorly water-soluble drug meloxicam by preparing solid dispersions with hydroxyethyl cellulose (HEC), mannitol and polyethylene glycol (PEG) 4000 and to develop a dosage form for geriatric population. Differential scanning calorimetry, X-ray diffractometry, Fourier transform infrared spectroscopy and scanning electron microscopy were used to investigate the solid-state physical structure of the prepared solid dispersions. Higher invitrodissolution of solid dispersions was recorded compared to their corresponding physical mixtures and the pure drug. PEG 4000 in 1: 9 drug to carrier ratio exhibited the highest drug release (100.2%), followed by mannitol (98.2%) and HEC (89.5%) in the same ratio. Meloxicam-PEG 4000 solid dispersion was formulated into suspension and optimization was carried out by 23factorial design. Formulations containing higher levels of methyl cellulose and higher levels of either sodium citrate or Tween 80 exhibited the highest drug release.
Interactions between hydrology, burning and contrasting plant groups during the millennial‐scale development of sub‐montane wet heath
Authors: Ellis Christopher J. 
Published: April 2008

AbstractQuestion:How might contrasting plant groups interact to confer ecosystem stability during the development of a wet heath: i.e. in response to two major environmental drivers, past hydrologic change and burning?Location:Rannoch Moor, Scotland.Methods:Three peat cores were used to reconstruct vegetation change, surface moisture and burning phases, during wet heath development for a radiocarbon‐dated period from ca. 9500–1000 yr BP.Results:Statistical analysis of peat cores revealed significant relationships between burning phases and past periods of inferred surface dryness. Vegetation elements were related in the palaeoecological record to surface dryness (Ericaceae), wetness (Sphagnum, monocotyledons, and Racomitrium) and periods of burning (i.e. negative correlation of Racomitrium and monocotyledon remains with charcoal). However, correlations between plant groups could not be adequately explained by their equivalent direct response to hydrology and burning, and the effects of species interactions are invoked.Conclusions:The results indicate millennial‐scale stability of the wet heath ecosystem in response to past environmental change (i.e. hydrology and burning). This stability is conferred by interaction between a diversity of plant groups, enabling local shifts in vegetation composition in response to environmental drivers. This long‐term stability of the mire ecosystem forms a template against which present‐day threats (e.g. pollution, climate change) should be critically assessed.
Touch Study of Polymer Materials Surfaces — Description of Raspiness by a Correlation Approach Between Sensorial Analysis and Physical Measurements
Authors: Sabiri N. , Leblond L. , Villoutreix J. , Lavergne M. , Acétarin J.‐D. , Villoutreix G. 
Published: April 2008

AbstractTo the various criteria such as durability and comfort, always taken into account for the purchase of a vehicle, nowadays criteria of sensory size like smell and touch are to be added. We carried out this study on evaluation of touch and more particularly on touch of plastics surfaces as these materials are largely used in automobile cockpits (handles of door, seats, dashboards). The touch of these materials must first be evaluated in order to be controlled. It is the role of the panels of skilled experts, who use various tactile descriptors to characterize surfaces according to human sensitivity. The objective of this work is to undergo a statistical analysis of tactile data on the basis of precise criteria (repeatability, consistency, precision of analysis) in order to achieve a characteristic model of a given descriptor, selected for the tactile sensory analysis. In parallel, with the analysis of the panel data, we tried to characterize the surface of samples by instrumental physical measurements. A second part of this work will lead us, in the framework of the study of roughness, to try to establish a correlation between these measurements and the data obtained according to the protocol of the raspy descriptor of sensory analysis.
Influence of Laser‐Induced Topography Changes on the Activity of Catalyst Coatings as Examined by Infrared Thermography
Authors: Seyler Michael , Selzner Christian , Holzapfel Christian , Mücklich Frank , Maier Wilhelm F. 
Published: April 2008

AbstractA mixed metal oxide catalyst coating is subjected to laser irradiation by a Nd:YAG laser operating at 266 nm to induce local changes in surface topography. The coating is exposed to laser interference patterns as well as to direct laser irradiation without interference. Samples are characterized by means of White Light Interferometry and Scanning Electron Microscopy. Irradiation with interference patterns causes the formation of wave‐like surface patterns in micrometer scale whereas direct laser irradiation generates porosity with pore sizes in the range of 100nm. Emissivity‐corrected infrared thermography (ecIRT) is applied to analyze the effect of surface topography changes on the catalytic activity of coatings in parallel. The catalytic combustion of iso‐octane with different contents of oxygen in nitrogen is used as a test reaction for catalytic activity. Local temperature increase on the substrate is chosen as a measure for catalytic activity. For laser interference structured coating, the catalytic activity improves with increase in geometric surface area caused by the wave‐like pattern. For direct laser irradiation, the porosity created by the laser enhances catalytic activity with respect to the unstructured coating.
Fabrication of a Memory Chip by a Complete Self‐Assembly Process Using State‐of‐the‐Art Multilevel Cell (MLC) Technology
Authors: Bandyopadhyay Anirban , Miki Kazushi 
Published: April 2008

AbstractUsing a two bit molecular switch, an ultra‐dense memory chip has been built following a fully automated fabrication process. Well‐ordered templates are grown naturally using a well‐defined protocol of temperature variation. This template is so designed that molecules are adsorbed selectively only into particular sites whenever they are bombarded on the template through an e‐beam evaporator for a particular time. The technique is a generalized protocol that has been used to grow atomic‐scale templates by proper tuning of basic global parameters like temperature and evaporation time. Tuning of the basic template parameters is also demonstrated here, and has been used to scale down parameter values following the same route. Tuning the junction profile should allow selective adsorption of more complicated multi‐level switches in future. Therefore, a fairly simple technology has been established that addresses one of the most fundamental issues of continuous miniaturization, i.e., simultaneous automated growth of thousands of atomically precise single molecular devices.
Poly(vinyl alcohol) Rehydratable Photonic Crystal Sensor Materials
Authors: Muscatello Michelle M. Ward , Asher Sanford A. 
Published: April 2008

AbstractWe developed a new photonic crystal hydrogel material based on the biocompatible polymer poly (vinyl alcohol) (PVA), which can be reversibly dehydrated and rehydrated, without the use of additional fillers, while retaining the diffraction and swelling properties of polymerized crystalline colloidal arrays (PCCA). This chemically modified PVA hydrogel photonic crystal efficiently diffracts light from the embedded crystalline colloidal array. This diffraction optically reports on volume changes occurring in the hydrogel by shifts in the wavelength of the diffracted light. We fabricated a pH sensor, which demonstrates a 350 nm wavelength shift between pH values of 3.3 and 8.5. We have also fabricated a Pb+2 sensor, in which pendant crown ether groups bind lead ions. Immobilization of the ions within the hydrogel increases the osmotic pressure due to the formation of a Donnan potential, swelling the hydrogel and shifting the observed diffraction in proportion to the concentration of bound ions. The sensing responses of rehydrated PVA pH and Pb+2 sensors were similar to that before drying. This reversibility of rehydration enables storage of these hydrogel photonic crystal sensors in the dry state, which makes them much more useful for commercial applications.
Mechanistic Inferences Derived from Competitive Catalytic Reactions: Pd(binap)‐Catalyzed Amination of Aryl Halides
Authors: Ferretti Antonio C. , Mathew Jinu S. , Ashworth Ian , Purdy Malcolm , Brennan Colin , Blackmond Donna G. 
Published: April 2008

AbstractHealthy competition: The Pd(binap)‐catalyzed amination of aryl halides demonstrates how the results from competitive reactions can be strikingly different from those obtained from study of the separate reactions. We show how the competitive network provides mechanistic information not accessible from study of the reactions separately.
Diastereoselective Synthesis of Trifluoromethylated γ‐Butyrolactones via N‐Heterocyclic Carbene‐Catalyzed Conjugated Umpolung of α,β‐Unsaturated Aldehydes
Authors: Hirano Keiichi , Piel Isabel , Glorius Frank 
Published: April 2008

AbstractThe N‐heterocyclic carbene‐catalyzed conjugate umpolung of differently substituted α,β‐unsaturated aldehydes is described. Coupling of these compounds with a variety of trifluoromethylated ketones results in the selective formation of fluorinated γ‐butyrolactones. Using thiazolium‐derived N‐heterocyclic carbenes, the unlike stereoisomers are formed predominantly, whereas the imidazol‐2‐ylidene IMes results in lower selectivities and the preferred formation of the like isomer.
Enantioselective Organocatalytic Epoxidation Driven by Electrochemically Generated Percarbonate and Persulfate
Authors: Page Philip C. Bulman , Marken Frank , Williamson Craig , Chan Yohan , Buckley Benjamin R. , Bethell Donald 
Published: April 2008

AbstractAn organocatalytic asymmetric epoxidation reaction using iminium salt catalysts is described, in which the stoichiometric persulfate oxidant is generated electrochemically. This system offers comparable ees to the use of commercially available persulfate. Electrochemically generated percarbonate ion is also a successful and novel oxidant system for use with iminium salts.
Bakterielle Acyltransferasen als Alternative für lipasekatalysierte Acylierungen zur Produktion von Oleochemikalien und Brennstoffen
Authors: Stöveken Tim , Steinbüchel Alexander 
Published: April 2008

AbstractBakterielle Acyltransferasen bilden eine neue Enzymklasse, als deren erstes Mitglied die WS/DGAT in Acinetobacter baylyi ADP1 identifiziert wurde. Ihre geringe Spezifität wurde für zahlreiche biotechnologische Anwendungen zur Lipidmodifizierung genutzt, ein Gebiet, auf dem bisher hauptsächlich Lipasen Verwendung finden. Beispiele sind die Biosynthesen von Jojoba‐ähnlichen Wachsestern und von Fettsäureethylestern. Darüber hinaus lassen sich mit diesen Enzymen Acylthioester synthetisieren. Acyltransferasen sind eine mögliche Alternative zu Lipasen. Mit ihnen können Acyloxoester und Acylthioester statt durch In‐vitro‐Katalyse im Enzymreaktor in vivo durch Ganzzellkatalyse hergestellt werden. In diesem Kurzaufsatz beleuchten wir die biotechnologische Verwendung der Acyltransferasen für die Produktion von modifizierten Lipiden, ausgehend von erneuerbaren Rohstoffen.
Bacterial Acyltransferases as an Alternative for Lipase‐Catalyzed Acylation for the Production of Oleochemicals and Fuels
Authors: Stöveken Tim , Steinbüchel Alexander 
Published: April 2008

AbstractBacterial acyltransferases are a new class of enzymes, and the first member was identified as WS/DGAT in Acinetobacter baylyi ADP1. Their unspecificity have been used in several biotechnological applications for lipid modification, a field that has been dominated by the use of lipases. Examples are the biosynthesis of jojoba‐like wax esters and fatty‐acid ethyl esters. In addition, these enzymes are also capable of synthesizing acylthioesters. Acyloxoesters and acylthioesters can thus be produced in vivo by whole‐cell fermentations rather than in vitro in an enzyme reactor. In this Minireview, we focus on the biotechnological utilization of acyltransferases for the production of modified lipids from renewable resources.
A Ruthenium Bridge in Fullerene–Ferrocene Arrays: Synthesis of [Ru(C60Me5)R(CO)2] (R=C6H4Fc, C≡CFc) and Their Charge‐Transfer Properties
Authors: Matsuo Yutaka , Matsuo Keiko , Nanao Takeshi , Marczak Renata , Gayathri S. Shankara , Guldi Dirk M. , Nakamura Eiichi 
Published: April 2008

AbstractNew fullerene–ferrocene arrays, [Ru(C60Me5)(C4H6Fc)(CO)2] (Fc=ferrocenyl) and [Ru(C60Me5)(CCFc)(CO)2], in which the ruthenium complex functions as a conjugative bridge, were synthesized by the reaction of [Ru(C60Me5)Cl(CO)2] with FcC6H4MgBr and FcCCLi, respectively. These compounds were investigated by electrochemical measurement, single‐crystal X‐ray structural analysis, and photophysical measurement. Upon photoirradiation, the former compound was converted rapidly into the corresponding triplet state in toluene (τsinglet=21 ps), whereas the charge‐separated state was predominant in THF (τsinglet=10.5 ps; τCS=355 ps). The latter compound, on the other hand, formed the charge‐separated state in both toluene and THF (τsinglet=3.0 ps; τCS=152 ps). Thus, the structural difference between the phenylene and acetylene bridges in 1 and 2, respectively, was found to change the outcome of the photophysical processes.
Tailored Control and Optimisation of the Number of Phosphonic Acid Termini on Phosphorus‐Containing Dendrimers for the Ex‐Vivo Activation of Human Monocytes
Authors: Rolland Olivier , Griffe Laurent , Poupot Mary , Maraval Alexandrine , Ouali Armelle , Coppel Yannick , Fournié Jean‐Jacques , Bacquet Gérard , Turrin Cédric‐Olivier , Caminade Anne‐Marie , Majoral Jean‐Pierre , Poupot Rémy 
Published: April 2008

AbstractThe syntheses of a series of phosphonic acid‐capped dendrimers is described. This collection is based on a unique set of dendritic structural parameters—cyclo(triphosphazene) core, benzylhydrazone branches and phosphonic acid surface—and was designed to study the influence of phosphonate (phosphonic acid) surface loading towards the activation of human monocytes ex vivo. Starting from the versatile hexachloro‐cyclo(triphosphazene) N3P3Cl6, six first‐generation dendrimers were obtained, bearing one to six full branches, that lead to 4, 8, 12, 16, 20 and 24 phosphonate termini, respectively. The surface loading was also explored at the limit of dense packing by means of a first‐generation dendrimer having a cyclo(tetraphosphazene) core and bearing 32 termini, and with a first‐generation dendrimer based on a AB2/CD5 growing pattern and bearing 60 termini. Human monocyte activation by these dendrimers confirms the requirement of the whole dendritic structure for bioactivity and identifies the dendrimer bearing four branches, thus 16 phosphonate termini, as the most bioactive.
Estimating the Temperature Dependence of Peptide Folding Entropies and Free Enthalpies from Total Energies in Molecular Dynamics Simulations
Authors: Boned Ricard , van Gunsteren Wilfred F. , Daura Xavier 
Published: April 2008

AbstractThe temperature dependence of thermodynamic quantities, such as heat capacity, entropy and free enthalpy, may be obtained by using well‐known equations that relate these quantities to the enthalpy of the molecular system of interest at a range of temperatures. In turn, the enthalpy of a molecular system can be estimated from molecular dynamics simulations of an appropriate model. To demonstrate this, we have investigated the temperature dependence of the enthalpy, heat capacity, entropy and free enthalpy of a system that consists of a β‐heptapeptide in methanol and have used the statistical mechanics relationships to describe the thermodynamics of the folding/unfolding equilibrium of the peptide. The results illustrate the power of current molecular simulation force fields and techniques in establishing the link between thermodynamic quantities and conformational distributions.
Tandem Cofacial Stacks of Porphyrin–Phthalocyanine Dyads through Complementary Coordination
Authors: Morisue Mitsuhiko , Kobuke Yoshiaki 
Published: April 2008

AbstractA novel straightforward methodology to organize discrete heterogeneous stacks of porphyrin and phthalocyanine employed an imidazolyl‐to‐zinc complementary coordination protocol for a ZnIIphthalocyanine that contains an imidazolyl terminal with an ethynylporphyrin as a coplanar spacer. Structural elucidation was performed by means of size‐exclusion chromatography, spectral titration, and NMR spectroscopy. The association constants for the complementary coordination of the heterogeneous slipped‐cofacial tetrads reached extremely high values, in the order of 1014 M−1. Close contact of the porphyrin and phthalocyanine planes led to a strong shielding of the cofacial protons, which were split due to the slipped‐cofacial heterogeneous environment. In variable‐temperature NMR spectroscopy, the split signals remained in the aromatic region, a result suggesting structural robustness. Addition of trifluoroacetic acid dissociated the coordination structure to unify the split signals. The stacked tetrads showed unique electronic structures, such as strong exciton coupling and charge‐transfer properties between the porphyrin and phthalocyanine units, which were modulated by the peripheral substituents of the phthalocyanine subunit and by the solvent. Interconversion between the coordination tetrad and the corresponding dyad was observed upon addition of an axial ligand.
A Core–Shell Nanoparticle Approach to Photoreversible Fluorescence Modulation of a Hydrophobic Dye in Aqueous Media
Authors: Chen Jian , Zeng Fang , Wu Shuizhu , Chen Qiming , Tong Zhen 
Published: April 2008

AbstractAmphiphilic core–shell nanoparticles containing spiropyran moieties have been prepared in aqueous media. The nanoparticles consist of hydrophilic and biocompatible poly(ethyleneimine) (PEI) chain segments, which serve as the shell, and a hydrophobic copolymer of methyl methacrylate (MMA), a spiropyran‐linked methacrylate, and a cross‐linker, which forms the core of the nanoparticles. A hydrophobic fluorescent dye based on the nitrobenzoxadiazolyl (NBD) group was introduced into the nanoparticles to form NBD–nanoparticle complexes in water. The nanoparticles not only greatly enhance the fluorescence emission of the hydrophobic dye NBD in aqueous media, probably by accommodating the dye molecules in the interface between the hydrophilic shells and the hydrophobic cores, but also modulate the fluorescence of the dye through intraparticle energy transfer. This biocompatible and photoresponsive nanoparticle complex may find applications in biological areas such as biological diagnosis, imaging, and detection. In addition, this nanoparticle approach will open up possibilities for the fluorescence modulation of other hydrophobic fluorophores in aqueous media.
Developing a New Class of Axial Chiral Phosphorus Ligands: Preparation and Characterization of Enantiopure Atropisomeric Phosphinines
Authors: Müller Christian , Pidko Evgeny A. , Staring Antonius J. P. M. , Lutz Martin , Spek Anthony L. , van Santen Rutger A. , Vogt Dieter 
Published: April 2008

AbstractBoth enantiomers of the first atropisomeric phosphinine (1) have been isolated by using analytical HPLC on a chiral stationary phase. The enrichment of one enantiomer and a subsequent investigation into its racemization kinetics revealed a barrier for internal rotation of Δ${G{{{\ne}\hfill \atop 298\hfill}}}$=(109.5±0.5) kJ mol−1, which is in excellent agreement with the theoretically predicted value of Δ${G{{{\ne}\hfill \atop 298\hfill}}}$=116 kJ mol−1. Further analysis with UV and circular dichroism spectroscopies and density functional theory calculations led to the determination and assignment of the absolute configurations of both enantiomers. These results are the basis for future investigations into this new class of axially chiral phosphinine‐based ligands and their possible applications in asymmetric homogeneous catalysis.
Superstructure‐Dependent Optical and Electrical Properties of an Unusual Face‐to‐Face, π‐Stacked, One‐Dimensional Assembly of Dehydrobenzo[12]annulene in the Crystalline State
Authors: Hisaki Ichiro , Sakamoto Yuu , Shigemitsu Hajime , Tohnai Norimitsu , Miyata Mikiji , Seki Shu , Saeki Akinori , Tagawa Seiichi 
Published: April 2008

AbstractTo develop a novel π‐conjugated molecule‐based supramolecular assembly, we designed and synthesized trisdehydrotribenzo[12]annulene ([12]DBA) derivative 2 with three carboxyl groups at the periphery. Recrystallization of 2 from DMSO gave a crystal of the solvate 2⋅3 DMSO. Crystallographic analysis revealed, to our surprise, that a face‐to‐face π‐stacked one‐dimensional (1D) assembly of 2 was achieved and that the DMSO molecule played a significant role as a “structure‐dominant element” in the crystal. This is the first example of [12]DBA to stack completely orthogonal to the columnar axis. To reveal its superstructure‐dependent optical and electrical properties, 2 and its parent molecule 1, which crystallizes in a herringbone fashion, were subjected to fluorescence spectroscopic analysis and charge‐carrier mobility measurements in crystalline states. The 1D stacked structure of 2 provides a red‐shifted, broadened, weakened fluorescence profile (λmax=545 nm, ϕF=0.01), compared to 1 (λmax=491 nm, ϕF=0.12), due to strong interactions between the p orbitals of the stacked molecules. The charge‐carrier mobility of the single crystal of 2⋅3 DMSO, as well as 1, was determined by flash photolysis time‐resolved microwave conductivity (FP‐TRMC) measurements. The single crystal of 2⋅3 DMSO revealed significantly‐anisotropic charge mobility (∑μ=1.5×10−1 cm2 V−1 s−1) along the columnar axis (crystallographic c axis). This value is 12 times larger than that along the orthogonal axis (the a axis).