Home About us Contact
|
Home About us Contact | ||
|
|
||
Chemical Identity (chemical + identity)
Selected AbstractsElectrochemical stabilization of crystalline silicon with aromatic self-assembled monolayers in aqueous electrolytesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 14 2005Murat Tutus Abstract We report stable chemical engineering of hydrogen-terminated Si[111] surfaces in aqueous electrolytes by electrochemical grafting of aromatic monolayers. The topography and free energy of the engineered surface obtained from AFM and contact angle measurements confirmed homogeneous coating of the surface with a monolayer. Grafting of monolayers actually resulted in a clear suppression of the surface defect densities, demonstrated by photoluminescence lifetime. Changes in the surface chemical identities after grafting and post-treatments were followed by X-ray photoelectron spectroscopy (XPS). The electrochemical stability in aqueous electrolytes was assessed by impedance spectroscopy, revealing an improved stabilization of the Si/electrolyte interface by the grafted monomolecular film. This protocol was further applied for another aromatic compound, where the impact of 4-substituent functions could clearly be detected by photovoltage measurements. The chemical and electrochemical stability achieved here is promising for the successive deposition of biocompatible polymer films and lipid membranes. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Characterization of Lead Precipitate Following Uptake by Roots of Brassica junceaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2009Donald E. R. Meyers Abstract Seedlings of Brassica juncea (L.) Czern. were grown in solution culture for 14 d prior to exposure to Pb2+ at an activity of 31 ,M for 72 h. Electron-dense deposits found within the apoplast and symplast were analyzed using scanning transmission electron microscopy/energy dispersive spectroscopy to determine the chemical identity of the deposits and potential toxicity resistance mechanisms. Irrespective of the cellular compartment in which they were found, the deposits contained Pb, O, P, and Cl. For the extracellular deposits, the average Pb:P:O atomic ratio was 1:0.54:3.0, which together with the hexagonal crystal system suggests that Pb is present as chloropyromorphite (Pb5(PO4)3Cl). A weak Ca signal also was detected in approximately half of the spectra, possibly indicating the presence of small concentrations of phosphohedyphane (Pb3Ca2(PO4)3Cl). The evidence suggests that B. juncea resists Pb toxicity by storing precipitated Pb in the vacuole. [source] Neurochemical identification of stereotypic burst-firing neurons in the rat dorsal raphe nucleus using juxtacellular labelling methodsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2007Mihály Hajós Abstract Recent electrophysiological studies have discovered evidence of heterogeneity of 5-hydroxytryptamine (5-HT) neurons in the mesencephalic raphe nuclei. Of particular interest is a subpopulation of putative 5-HT neurons that display many of the electrophysiological properties of presumed 5-HT-containing neurons (regular and slow firing of single spikes with a broad waveform) but fire spikes in short, stereotyped bursts. In the present study we investigated the chemical identity of these neurons in rats utilizing in vivo juxtacellular labelling methods. Of ten dorsal raphe nucleus (DRN) neurons firing short stereotyped bursts within an otherwise regular firing pattern, all exhibited immunoreactivity for either 5-HT (n = 6) or the 5-HT synthesizing enzyme, tryptophan hydroxylase (TRH; n = 2) or both (n = 2). Supporting pharmacological experiments demonstrated that the burst firing DRN neurons demonstrated equal sensitivity to 5-HT1A agonism and ,1 -adrenoceptor antagonism to single spiking DRN neurons that we have previously identified as 5-HT-containing. Collectively these data provide direct evidence that DRN neurons that exhibit stereotyped burst firing activity are 5-HT containing. The presence of multiple types of electrophysiologically distinct midbrain 5-HT neurons is discussed. [source] Controlled Growth Factor Delivery for Tissue EngineeringADVANCED MATERIALS, Issue 32-33 2009Prakriti Tayalia Abstract Growth factors play a crucial role in information transfer between cells and their microenvironment in tissue engineering and regeneration. They initiate their action by binding to specific receptors on the surface of target cells and the chemical identity, concentration, duration, and context of these growth factors contain information that dictates cell fate. Hence, the importance of exogenous delivery of these molecules in tissue engineering is unsurprising, considering their importance for tissue regeneration. However, the short half-lives of growth factors, their relatively large size, slow tissue penetration, and their potential toxicity at high systemic levels, suggest that conventional routes of administration are unlikely to be effective. In this review, we provide an overview of the design criteria for growth factor delivery vehicles with respect to the growth factor itself and the microenvironment for delivery. We discuss various methodologies that could be adopted to achieve this localized delivery, and strategies using polymers as delivery vehicles in particular. [source] Preparation, characterization and biological evaluation of 99mTc(CO)3 -labelled cyclic polyaminesJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 14 2005H. P. Vanbilloen Abstract Three cyclic polyamines, namely 1,4,7-triazacyclononane, 1,4,7,10-tetraazacyclo-dodecane (cyclen) and 1,4,8,11-tetraazacyclotetradecane (cyclam), were evaluated as potential ligands for complexation of a technetium(I) tricarbonyl core. They can be used as bifunctional chelating agents for labelling bioactive compounds. Each of the three ligands forms a positively charged technetium tricarbonyl complex in high yield but heating is required to promote complex formation. The charge of the 99mTc(I)tricarbonyl labelled derivatives was confirmed using electrophoresis, and radio-LC,MS supports their proposed chemical identity. After i.v. injection in mice, the compounds were rapidly cleared from the blood by the hepatobiliary or urinary pathway depending on their lipophilicity. Copyright © 2005 John Wiley & Sons, Ltd. [source] HPLC purification and re-evaluation of chemical identity of two circular bacteriocins, gassericin A and reutericin 6LETTERS IN APPLIED MICROBIOLOGY, Issue 4 2010K. Arakawa Abstract Aim:, The study aimed for the complete purification and recharacterization of the highly hydrophobic circular bacteriocins, gassericin A and reutericin 6. Methods and Results:, Gassericin A and reutericin 6 were purified to homogeneity using previously described method and reverse-phase HPLC with an octyl column and eluents of aqueous acetonitrile and 2-propanol. Mass analysis, N-terminal sequencing and bacteriocin assay of the HPLC-purified bacteriocins showed the two bacteriocins had identical seamless circular structures with the same m/z value (5651) of [M + H]+ and both had the same specific activity. d/l- amino acid composition analysis using two distinct methods with the chiral fluorescent derivatization reagents (+)-1-(9-fluorenyl)ethyl chloroformate and o -phthalaldehyde/N -acetyl- l -cystein revealed neither gassericin A nor reutericin 6 contained d -alanine residues contrary to our previous results. Conclusion:, Purified gassericin A and reutericin 6 are chemically identical circular molecules containing no d -alanine residues. Significance and Impact of the Study:, The HPLC conditions developed in this study will facilitate advanced purification and correct characterization of other highly hydrophobic bacteriocins. [source] Characterization of CART neurons in the rat and human hypothalamusTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 1 2001Carol F. Elias Cocaine- and amphetamine-regulated transcript (CART) is a recently described neuropeptide widely expressed in the rat brain. CART mRNA and peptides are found in hypothalamic sites such as the paraventricular nucleus (PVH), the supraoptic nucleus (SON), the lateral hypothalamic area (LHA), the dorsomedial nucleus of the hypothalamus (DMH), the arcuate nucleus (Arc), the periventricular nucleus (Pe), and the ventral premammillary nucleus (PMV). Intracerebroventricular administration of recombinant CART peptide decreases food intake and CART mRNA levels in the Arc are regulated by leptin. Leptin administration induces Fos expression in hypothalamic CART neurons in the PVH, the DMH, the Arc, and the PMV. In the current study, we used double label in situ hybridization histochemistry to investigate the potential direct action of leptin on hypothalamic CART neurons and to define the chemical identity of the hypothalamic CART neurons in the rat brain. We found that CART neurons in the Arc, DMH, and PMV express long form leptin-receptor mRNA, and the suppressor of cytokine signaling-3 (SOCS-3) mRNA after an acute dose of intravenous leptin. We also found that CART neurons in the parvicellular PVH, in the DMH and in the posterior Pe coexpress thyrotropin-releasing hormone (TRH) mRNA. CART neurons in the magnocellular PVH and in the SON coexpress dynorphin (DYN), and CART cell bodies in the LHA and in the posterior Pe coexpress melanin-concentrating hormone (MCH) and glutamic acid decarboxylase (GAD-67) mRNA. In the Arc, a few CART neurons coexpress neurotensin (NT) mRNA. In addition, we examined the distribution of CART immunoreactivity in the human hypothalamus. We found CART cell bodies in the PVH, in the SON, in the LHA, in the Arc (infundibular nucleus) and in the DMH. We also observed CART fibers throughout the hypothalamus, in the bed nucleus of the stria terminalis, and in the amygdala. Our results indicate that leptin directly acts on CART neurons in distinct nuclei of the rat hypothalamus. Furthermore, hypothalamic CART neurons coexpress neuropeptides involved in energy homeostasis, including MCH, TRH, DYN, and NT. The distribution of CART cell bodies and fibers in the human hypothalamus indicates that CART may also play a role in the regulation of energy homeostasis in humans. J. Comp. Neurol. 432:1,19, 2001. © 2001 Wiley-Liss, Inc. [source] PANTELLERIAN WARE: A COMPREHENSIVE ARCHAEOMETRIC REVIEW,ARCHAEOMETRY, Issue 3 2007G. MONTANA Pantellerian ware is a Late Roman cooking ware whose production centre was established on the island of Pantelleria by the pioneering research of Fulford and Peacock almost 20 years ago (Peacock 1982; Fulford and Peacock 1984). Archaeological and archaeometric studies carried out by the authors of the present contribution during the past four years have aimed to fully characterize this ceramic class. Recurrent ceramic forms, their distribution over time and space, their petrographic characteristics and their chemical identity, as well as possible raw materials and their technological properties, were considered. The present paper is a comprehensive review of this archaeometric work and aims to establish a ,reference group'. Using a representative number of samples of Pantellerian ware that were recently discovered in the island through archaeological field surveys or surface and submarine excavations, it was possible to characterize in detail the compositional variability of this ware in terms of chemistry and petrography. Furthermore, the physical properties of this ceramic type have been defined in order to better understand its performance characteristics, mainly in response to induced thermal stress. In the meantime, the experimental mixing and tempering of locally sampled raw materials have shed light on the ancient manufacturing process and have led to an approximation of the original paste. [source] | ||||||||||