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Query: UNIPROT:P06889 (Mol)
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Inhalation of crystalline silica results in pulmonary fibrosis and silicosis. It has been suggested that mast cells play a role in these conditions. How mast cells would influence pathology is unknown. We thus explored mast cell interactions with silica in vitro and in B6.Cg-kit(W-sh) mast cell-deficient mice. B6.Cg-kit(W-sh) mice did not develop inflammation or significant collagen deposition after instillation of silica, while C57Bl/6 wild-type mice did have these findings. Given this supporting evidence of a role for mast cells in the development of silicosis, we examined the ability of silica to activate mouse bone marrow-derived mast cells (BMMC), including degranulation (beta-hexosaminidase release); production of reactive oxygen species (ROS) and inflammatory mediators; and the effects of silica on Fc epsilon RI-dependent activation. Silica did not induce mast cell degranulation. However, TNF-alpha, IL-13, monocyte chemotactic protein-1, protease activity, and production of ROS were dose-dependently increased after silica exposure, and production was enhanced after Fc epsilon RI stimulation. This mast cell activation was inhibited by anti-inflammatory compounds. As silica mediates some effects in macrophages through scavenger receptors (SRs), we first determined that mast cells express scavenger receptors; then explored the involvement of SR-A and macrophage receptor with colleagenous structure (MARCO). Silica-induced ROS formation, apoptosis, and TNF-alpha production were reduced in BMMC obtained from SR-A, MARCO, and SR-A/MARCO knockout mice. These findings demonstrate that silica directs mast cell production of inflammatory mediators, in part through SRs, providing insight into critical events in the pathogenesis and potential therapeutic targets in silicosis.
Am J Respir Cell Mol Biol 2007 Jan
PMID:Silica-directed mast cell activation is enhanced by scavenger receptors. 1690 92

A highly sensitive and selective fluorogenic probe for fluoride ion, 4-methylumbelliferyl tert-butyldimethylsilyl ether (4-MUTBS), was designed and synthesized. 4-MUTBS was a weakly fluorescent compound and was synthesized via the one-step reaction of 4-MU with tert-butyldimethylsilyl chloride. Upon incubation with fluoride ion in acetone-water solution (7:3, v/v), the Si-O bond of 4-MUTBS was cleaved and highly fluorescent 4-methylumbelliferone (4-MU) was released, hence leading to the fluorescence increase of the reaction solution. The fluorescence increase is linearly with fluoride concentration in the range 50-8000 nmol l(-1) with a detection limit of 19 nmol l(-1) (3sigma). Because of the high affinity of silicon toward fluoride ion, the proposed probe shows excellent selectivity toward fluoride ion over other anions. The method has been successfully applied to the fluoride determination in toothpaste and tap water samples.
Spectrochim Acta A Mol Biomol Spectrosc 2007 Jun
PMID:Novel fluorogenic probe for fluoride ion based on the fluoride-induced cleavage of tert-butyldimethylsilyl ether. 1696 35

Silica particle-associated inflammation is implicated in the genesis of several pulmonary diseases, including silicosis and lung cancer. In this study we investigated the role of phosphatidylcholine-specific phospholipase C (PC-PLC) in silica-stimulated induction of TNF-alpha and IL-1beta and how PC-PLC activity is regulated by silica in a rat alveolar macrophage model. We demonstrated that inhibition of PC-PLC, which was achieved with tricychodecan-9-yl-xanthate (D609), blocked the silica-stimulated induction of TNF-alpha and IL-1beta in alveolar macrophage, suggesting that PC-PLC is involved in the silica-associated inflammatory response. PC-PLC activity was increased significantly by silica exposure, and this could be inhibited by MnTBAP, which catalyzes both the dismutation of O2.- to O2 and H2O2 and the dismutation of H2O2 to O2 and H2O, revealing that PC-PLC activity is regulated in a redox-dependent manner. This is further confirmed by the finding that PC-PLC activity was increased by exogenous H2O2. The intracellular calcium chelator BAPTA blocked the H2O2-increased PC-PLC activity, while the calcium ionophore, A23187, enhanced PC-PLC activity. The data indicate that PC-PLC plays critical roles in the silica-associated inflammatory response and that PC-PLC is regulated through redox- and calcium-dependent manners in alveolar macrophages.
Am J Respir Cell Mol Biol 2007 May
PMID:Silica induces macrophage cytokines through phosphatidylcholine-specific phospholipase C with hydrogen peroxide. 1715 58

Silylative coupling of olefins differs from olefin metathesis. Although in both these reactions ruthenium catalysts play a crucial role and ethylene product is detected, ruthenium-carbene intermediate is formed only in the course of the metathesis reaction. In this study quantum chemical calculations based on the density functional theory (DFT) have been carried out in order to examine the mechanism of the silylative coupling of olefins leading to ethylene elimination. In the first step of the catalytic cycle, a hydrogen atom from the ruthenium catalytic center is transferred preferentially to the carbon atom bound to Si in a vinylsilane. This H transfer is coupled with the formation of Ru-C bond. Next, the rotation around the newly formed C-C single bond occurs so that silicon atom is placed in the vicinity of the ruthenium center. The following step involves the migration of a silyl moiety, and leads to Ru-Si bond formation, coupled with ethylene elimination. The next reaction, that is the insertion of ethylene (alkene) into Ru-Si bond, has an activation barrier almost as high as the reaction of ethylene elimination. However, the posibility of removing gaseous ethylene from the reactive mixture together with the entropic fators suggests that the insertion of alkene that is larger than C(2)H(4) is the rate limiting step in the silylative coupling of olefins. It also suggests that the substituents attached to the silicon atom or the carbon atoms of an alkene by electronic and steric effects may significantly affect silyl migration and thus the effectiveness of the catalytic reaction.
J Mol Model 2007 Apr
PMID:Quantum chemical study of the mechanism of ethylene elimination in silylative coupling of olefins. 1721 86

Understanding the fundamental interactions between proteins and solid surfaces is essential in the area of implantable medical devices. Fluorescence methods offer the sensitivity required to study the formation of the initial thin protein layers that mediate biocompatibility of materials. Thin protein layers (bovine serum albumin labelled with 1-anilino-8-naphthalenesulfonate, BSA-ANS) deposited on several surfaces (glass, silicon, stainless steel, polystyrene, and silver island film) were studied using confocal frequency domain Fluorescence Lifetime Imaging Microscopy (FLIM) and single-point multifrequency lifetime analysis techniques. FLIM provides spatial information about both fluorophores located on the surface and physicochemical parameters of the surface microenvironment. The average fluorescence lifetimes (tau(av)) of the adsorbed BSA-ANS generated by the contact between a protein solution and the material surface were measured by the multifrequency modulation and phase shift. Results indicate that tau(av) values of the albumin complexes on the surfaces (approximately 12 ns) are, in general, shorter than tau(av) found in the bulk solution (approximately 14 ns). For some surfaces, like polystyrene and silver island film the differences in tau(av) of the adsorbed BSA-ANS were found to be much greater. The differences in fluorescence lifetimes may indicate structural changes in the BSA protein induced by contact with the surface.
Exp Mol Pathol 2007 Apr
PMID:Fluorescence lifetime imaging study of a thin protein layer on solid surfaces. 1733 93

The various spatial arrangements of frontier orbitals that may lead to facile reductive splitting of the H2 molecule at mono- or binuclear catalysts containing s, p, d or f-block metals, and on surfaces of solids are briefly reviewed. The postulation is also made that binuclear divalent titanium (Ti(II)) and mononuclear silicon (Si(II)) species might serve as active sites for the H2 attachment reaction for hydridoalanates doped with Ti salts and hydridoborates doped with SiO2, respectively.
J Mol Model 2007 Jul
PMID:Orbital landscapes for reductive 2e- activation of dihydrogen molecule. 1738 Mar 53

pi-A isotherms, transmission electron microscope (TEM), atomic force microscope (AFM) images and photoluminescence spectra of a mixed Langmuir-Blodgett (LB) film of C(60) and stearic acid (SA) deposited on silicon substrate have been measured at room temperature. C(60)/SA nanoparticles aggregated and formed an ordered net-like structure when deposited on silicon substrate. Two PL intense bands centered at 731 and 806nm, respectively, which are rare at room temperature, were obtained. It is supposed that the particular ordered net-like construction of the LB film plays a crucial role in the enhancement of the photoluminescence. The 731nm PL band is related with the aggregation state of the particles and the 806nm PL band is referred as the intrinsic PL spectrum of the C(60).
Spectrochim Acta A Mol Biomol Spectrosc 2008 Jan
PMID:Photoluminescence of a mixed Langmuir-Blodgett film of C(60) and stearic acid at room temperature. 1749 18

Cell adhesion is required for essential biological functions such as migration, tissue formation and wound healing, and it is mediated by individual molecules that bind specifically to ligands on other cells or on the extracellular matrix. Atomic force microscopy (AFM) has been successfully used to measure cell adhesion at both single molecule and whole cell levels. However, the measurement of inherent cell adhesion properties requires a constant cell-probe contact area during indentation, a requirement which is not fulfilled in common pyramidal or spherical AFM tips. We developed a procedure using focused ion beam (FIB) technology by which we modified silicon pyramidal AFM cantilever tips to obtain flat-ended cylindrical tips with a constant and known area of contact. The tips were validated on elastic gels and living cells. Cylindrical tips showed a fairly linear force-indentation behaviour on both gels and cells for indentations >200 nm. Cylindrical tips coated with ligands were used to quantify inherent dynamic cell adhesion and elastic properties. Force, work of adhesion and elasticity showed a marked dynamic response. In contrast, the deformation applied to the cells before rupture was fairly constant within the probed dynamic range. Taken together, these results suggest that the dynamic adhesion strength is counterbalanced by the dynamic elastic response to keep a constant cell deformation regardless of the applied pulling rate.
J Mol Recognit
PMID:Cell dynamic adhesion and elastic properties probed with cylindrical atomic force microscopy cantilever tips. 1789 55

Silica sol-gels have been prepared under different conditions using triethoxysilane (TES) as precursor. The prepared sol-gels have been used to coat aluminum for corrosion protection. Vibrational assignments have been made for most vibration bands of TES, TES sol-gel, TES sol-gel-coated aluminum and xerogel. It has been noticed that air moisture may have helped the hydrolysis of the thin coating films. Xerogels have been obtained from the sol-gel under different temperature conditions and the resulting samples have been characterized by using infrared and Raman spectroscopic methods. IR data indicate that the sol-gel process is incomplete under the ambient conditions although an aqueous condition can have slightly improved the process. Two nonequivalent silicon atoms have been identified from the collected 29Si NMR spectra for the sol-gel, supporting the result derived from the IR data. The frequency of Si-H bending vibration has been found to be more sensitive to the skeletal structure than that of the Si-H stretching vibration. A higher temperature condition could favor the progression of hydrolysis and condensation. A temperature higher than 300 degrees C would cause sample decomposition without seriously damaging the silica network. From infrared intensity measurements and thermo-gravimetric analyses, the fractions of incomplete hydrolysis and condensation species have been estimated to be 4% and 3%, respectively. Electrochemical data have shown that the sol-gel coating significantly improves the corrosion protection properties of aluminum.
Spectrochim Acta A Mol Biomol Spectrosc 2008 Oct
PMID:Spectroscopic studies of triethoxysilane sol-gel and coating process. 1806 Aug 31

Nucleic acid array technology refers to the use and fabrication of arrays containing thousands of nucleic acid samples bound to solid substrates such as glass microscope slides or silicon wafers. Because the physical area occupied by each sample is usually 50 to 200 mum in diameter, it is possible to assay nucleic acid samples representing entire genomes, ranging in size from 3,000 to 32,000 genes, on a single slide. Microarrays are good for, among other things, analyzing gene expression patterns, genotyping and genetic mapping, comparative genomic hybridization, polysome analysis, and DNA-protein interactions. This overview describes the technology and the uses, and provides valuable web site listings for readers to obtain additional information.
Curr Protoc Mol Biol 2001 May
PMID:Overview of nucleic acid arrays. 1826 99


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