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181.
Young-Seok Shon Hyung Y. Choi Michael S. Guerrero Chuhee Kwon 《Plasmonics (Norwell, Mass.)》2009,4(2):95-105
This article presents a concise review of preparation methods for transparent nanostructured films, with an emphasis on their
current applications in transmission-localized surface plasmon resonance (T-LSPR) sensing. One of the first methods used for
the fabrication of transparent nanostructured metal films is a direct vacuum evaporation of thin gold films. Self-induced
formations of small gold islands result in transparent nanostructured gold arrays. The most well-established method is a nanosphere
lithography developed by Van Duyne. Nanotriangular island arrays with controlled size and optical properties can be fabricated
by this protocol. A different nanolithography method known as focused ion beam milling is reported and used for the fabrication
of nanohole arrays. Simple assembly of solution-phase synthesized nanoparticles has also been utilized for the preparation
of nanoparticle arrays capable of T-LSPR sensing. Lastly, this article also describes a new preparation strategy, in which
self-assembly/thermolysis of nanoparticle multilayers is employed to obtain transparent nanoisland architectures on glass
substrates. 相似文献
182.
To investigate methods to reduce metal artifacts during digital tomosynthesis for arthroplasty, we evaluated five algorithms with and without metal artifact reduction (MAR)-processing tested under different radiation doses (0.54, 0.47, and 0.33 mSv): adaptive steepest descent projection onto convex sets (ASD-POCS), simultaneous algebraic reconstruction technique total variation (SART-TV), filtered back projection (FBP), maximum likelihood expectation maximization (MLEM), and SART. The algorithms were assessed by determining the artifact index (AI) and artifact spread function (ASF) on a prosthesis phantom. The AI data were statistically analyzed by two-way analysis of variance. Without MAR-processing, the greatest degree of effectiveness of the MLEM algorithm for reducing prosthetic phantom-related metal artifacts was achieved by quantification using the AI (MLEM vs. ASD-POCS, SART-TV, SART, and FBP; all P < 0.05). With MAR-processing, the greatest degree of effectiveness of the MLEM, ASD-POCS, SART-TV, and SART algorithms for reducing prosthetic phantom-related metal artifacts was achieved by quantification using the AI (MLEM, ASD-POCS, SART-TV, and SART vs. FBP; all P < 0.05). When assessed by ASF, metal artifact reduction was largest for the MLEM algorithm without MAR-processing and ASD-POCS, SART-TV, and SART algorithm with MAR-processing. In ASF, the effect of metal artifact reduction was always greater at reduced radiation doses, regardless of which reconstruction algorithm with and without MAR-processing was used. In this phantom study, the MLEM algorithm without MAR-processing and ASD-POCS, SART-TV, and SART algorithm with MAR-processing gave improved metal artifact reduction. 相似文献
183.
《Arthropod Structure & Development》2017,46(1):30-38
We identify the presence of multiple vascular channels within the spider fang. These channels seem to serve the transport of zinc to the tip of the fang to cross-link the protein matrix by binding to histidine residues. According to amino acid and elemental analysis of fangs extracted shortly after ecdysis, His-rich proteins are deposited before Zn is incorporated into the cuticle. Microscopic and spectroscopic investigations in the electron microscope and synchrotron radiation experiments suggest that Zn ions are transported through these channels in a liable (yet unidentified) form, and then form stable complexes upon His binding. The resulting cross-linking through the Zn–His complexes is conferring hardness to the fang. Our observations of nano-channels serving the Zn-transport within the His-rich protein matrix of the fibre reinforced spider fang may also support recent bio-inspired attempts to design artificial polymeric vascular materials for self-healing and in-situ curing. 相似文献
184.
Christopher M. MacNeill 《Inorganica chimica acta》2011,365(1):196-203
Five new isostructural two-dimensional lanthanide-based coordination polymers with the formula Ln2(F4BDC)3(DEF)2(EtOH)2-2(DEF) (Ln = Tb, 1; Gd, 2; Eu, 3; La, 4; Nd, 5; F4BDC2− = 2,3,5,6-tetrafluoro-1,4-benzenedicarboxylate ligands; DEF = N,N′-diethylformamide), have been synthesized by reaction of Ln(NO3)3 and F4BDC in a DEF/EtOH solvent mixture. The compounds were characterized by single-crystal and powder X-ray diffraction. In all cases, the metal ion is coordinated by nine oxygen atoms from two bidentate μ2-F4BDC2− ligands, two bridging μ2-F4BDC2− ligands, one μ3-F4BDC2− ligand, one DEF molecule and one EtOH molecule forming a tri-capped trigonal prism. The Ln(1) metal ion is linked to an adjacent Ln(1) metal ion through the oxygen atoms of two bridging μ2-F4BDC2− ligands and two μ3-F4BDC2− bridging ligands to form a Ln2O18 dimer. The Ln2O18 polyhedra building units are linked to each other through four F4BDC2− ligands to form 2D sheets that are held together by hydrogen bonding to form a 3D framework. Compounds 1-5 were further characterized using thermogravimetric analysis and infrared spectroscopy. Studies of the photoluminescence properties of compounds 1 and 3, as well as the catalytic activity of compounds 3-5 in the Biginelli reaction, are presented. 相似文献
185.
Jency Thomas 《Inorganica chimica acta》2011,372(1):243-3394
Reaction of molybdate and phosphate precursors in the presence of 3d transition metal ions and pyrazole (pz) under hydrothermal condition resulted in the crystallization of four new phosphomolybdate cluster based solids: (pz)2[{Co(pz)4}5{P2Mo5O23}2]·6H2O (1), (pz){Ni(pz)4(H2O)2}[{Ni(pz)4}5{P2Mo5O23}2]·2H2O (2), {Cu(pz)4(H2O)2}[{Cu(pz)4}{Cu(pz)4(H2O)}{P2Mo5O23}]·2H2O (3) and (pz)[{Zn(pz)3}3{P2Mo5O23}]·2H2O (4). In all the solids, a metal complex {M(pz)n} covalently links{P2Mo5O23} clusters to form a chain. The dimensionality of the structures differs in the way the chains link or self assemble with counter ions and water molecules. To the best of our knowledge, 4 is the first example of a zinc complex incorporated with {P2Mo5O23} cluster. The paper discusses the self assembly occurring between in situ metal pyrazole complex and phosphomolybdate clusters through coordinate/covalent and noncovalent interactions during crystallization of a particular solid. 相似文献
186.
The role of signaling pathways in the regulation of cellular iron metabolism is becoming increasingly recognized. Iron chelation is used for the treatment of iron overload but also as a potential strategy for cancer therapy, because iron depletion results in cell cycle arrest and apoptosis. This study examined potential signaling pathways affected by iron depletion induced by desferrioxamine (DFO) or di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT). Both chelators affected multiple molecules in the mitogen-activated protein kinase (MAPK) pathway, including a number of dual specificity phosphatases that directly de-phosphorylate MAPKs. Examination of the phosphorylation of major MAPKs revealed that DFO and Dp44mT markedly increased phosphorylation of stress-activated protein kinases, JNK and p38, without significantly affecting the extracellular signal-regulated kinase (ERK). Redox-inactive DFO-iron complexes did not affect phosphorylation of JNK or p38, whereas the redox-active Dp44mT-iron complex significantly increased the phosphorylation of these kinases similarly to Dp44mT alone. Iron or N-acetylcysteine supplementation reversed Dp44mT-induced up-regulation of phospho-JNK, but only iron was able to reverse the effect of DFO on JNK. Both iron chelators significantly reduced ASK1-thioredoxin complex formation, resulting in the increased phosphorylation of ASK1, which activates the JNK and p38 pathways. Thus, dissociation of ASK1 could serve as an important signal for the phosphorylation of JNK and p38 activation observed after iron chelation. Phosphorylation of JNK and p38 likely play an important role in mediating the cell cycle arrest and apoptosis induced by iron depletion. 相似文献
187.
Bacterioferritin (BFR) from Escherichia coli is a member of the ferritin family of iron storage proteins and has the capacity to store very large amounts of iron as an Fe(3+) mineral inside its central cavity. The ability of organisms to tap into their cellular stores in times of iron deprivation requires that iron must be released from ferritin mineral stores. Currently, relatively little is known about the mechanisms by which this occurs, particularly in prokaryotic ferritins. Here we show that the bis-Met-coordinated heme groups of E. coli BFR, which are not found in other members of the ferritin family, play an important role in iron release from the BFR iron biomineral: kinetic iron release experiments revealed that the transfer of electrons into the internal cavity is the rate-limiting step of the release reaction and that the rate and extent of iron release were significantly increased in the presence of heme. Despite previous reports that a high affinity Fe(2+) chelator is required for iron release, we show that a large proportion of BFR core iron is released in the absence of such a chelator and further that chelators are not passive participants in iron release reactions. Finally, we show that the catalytic ferroxidase center, which is central to the mechanism of mineralization, is not involved in iron release; thus, core mineralization and release processes utilize distinct pathways. 相似文献
188.
Griffith DM Szocs B Keogh T Suponitsky KY Farkas E Buglyó P Marmion CJ 《Journal of inorganic biochemistry》2011,105(6):763-769
Reaction of the potent hydroxamate-based histone deacetylase (HDAC) inhibitor, suberoylanilide hydroxamic acid (SAHA), with hydrated metal salts of Fe(III), Cu(II), Ni(II) and Zn(II) yielded a tris-hydroxamato complex in the case of Fe(III) and bis-hydroxamato complexes in the case of Cu(II), Ni(II) and Zn(II) both in the solid state and in solution. Reaction of the secondary hydroxamic acid, N-Me-SAHA, also yielded a tris-hydroxamato complex in the case of Fe(III) and bis-hydroxamato complexes in the case of Cu(II), Ni(II) and Zn(II) in solution. These metal complexes have the hydroxamato moiety coordinated in an O,O’-bidentate fashion. Stability constants of the metal complexes formed with SAHA and N-Me-SAHA in a DMSO/H2O 70/30%(v/v) mixture are described. A novel crystal structure of SAHA together with a novel synthesis for N-Me-SAHA are also reported. 相似文献
189.
Domínguez-Martín A Choquesillo-Lazarte D González-Pérez JM Castiñeiras A Niclós-Gutiérrez J 《Journal of inorganic biochemistry》2011,105(8):1073-1080
In contrast to the comprehensive structural information about metal complexes with adenine, the corresponding to its isomer 2-aminopurine (H2AP) is extremely poor. With the aim to rationalize the metal binding pattern of H2AP, we report the molecular and/or crystal structure of four novel compounds with various iminodiacetate-like (IDA-like) copper(II) chelates: [Cu(IDA)(H2AP)(H2O)]·H2O (1), [Cu(MIDA)(H2AP)(H2O)]·3H2O (2), {[Cu(NBzIDA)(H2AP)]·1.5H2O}n (3) and [Cu(MEBIDA)(H2AP)(H2O)]·3.5 H2O (4), where IDA, MIDA, NBzIDA and MEBIDA are R = H, CH3, benzyl- and p-tolyl- in R-N-(CH2-COO-)2 ligands, respectively. Synthesis strategies include direct reactions of copper(II) chelates with H2AP (alone, for 1 and 3) and/or with the base pairs H2AP:thymine (1-4) or H2AP:cytosine (3). Moreover, these compounds have been also investigated by spectral and thermal methods. Regardless of the N-derivative of the IDA chelator, molecular recognition between H2AP and the referred Cu(II)-chelates only displays the formation of the Cu-N7(purine-like) bond what is clearly in contrast to what was previously reported for adenine. The metal binding pattern of 2-aminopurine is discussed on the basis of the electronic effects and steric hindrance of the 2-amino exocyclic group. 相似文献
190.
Di Giuro CM Buongiorno D Leitner E Straganz GD 《Journal of inorganic biochemistry》2011,105(9):1204-1211
Mononuclear nonheme iron enzymes (MNHEs) catalyze a range of very diverse reactions in O2 metabolism, but they share a common principle active-site organization. To investigate a putative catalytic promiscuity of these enzymatic metal centers, we studied the reactivity of the 3-His ligated metal center of diketone cleaving enzyme (Dke1) toward non-native substrates, with a focus on alternative O2 dependent reactions. From a screening approach, which aims at eliminating steric factors by including minimal substrate-substructures, three alternative, ‘non-β-dicarbonyl-cleavage’ reactions are identified, among them an unprecedented oxygenation of maltol. Maltol cleavage is characterized by steady state and fast kinetic measurements and shows an O2 concentration dependent rate determining step kcat/KM(O2) of 0.3 mM− 1 s− 1 and a strict coupling of O2 reduction and substrate oxidation. Furthermore, the catalytic potential of the 3-His metal center for O2 dependent catechol ring-cleavage and phenylpyruvate oxidation (PP) is demonstrated. 相似文献