Redox-Active Monolayers in Mesoporous Silicon

Herein, redox reactions at chemically derivatized porous silicon (PSi) films are investigated. Passivation of the PSi matrix, by replacing metastable Si–H termini with nonpolar SiCCR linkages, allows the electrochemical PSi device to operate in aqueous environments under oxidizing conditions (i.e., electron hole accumulation regime). Cu­(I)-catalyzed alkyne–azide cycloaddition reactions are used to anchor ferrocene derivatives and probe electrochemical reactions at the exceedingly large surface area-to-volume ratio of mesoporous PSi. The forward-biased p-type PSi/electrolyte interface retains a quasi-metallic behavior throughout its entire contour, and it does so for prolonged times even when the electrode is poised at potentials at which a bare silicon electrode would rapidly oxidize. The interfacial capacitance of the PSi matrix is, however, unexpectedly low. An explanation is proposed where PSi morphology and the semiconductor space-charge layer capacitance play a significant role in determining the charging properties of the electrode. These results are important for the application of porous semiconductor electrodes in sensing, electrocatalytic, and energy-conversion devices

The Diagnostics of Laser-Induced Fluorescence (LIF) Spectra of PAHs in Flame with TD-DFT: Special Focus on Five-Membered Ring

The electronic emission characteristics of 13 gas-phase PAHs, ranging from phenlylacetylene to rubicene, were investigated to diagnose laser-induced fluorescence (LIF) spectra of PAHs in flame by DFT, TD-DFT, and premixed flame modeling methods. It was found that the maximum emission wavelengths of the PAHs with five-membered ring are located in visible region and insensitive to the number of C atoms. However, the fluorescence wavelengths of the PAHs without five-membered rings increase with the number of C atoms due to the reduced HOMO–LUMO gap. In addition, the fluorescence wavelength of the PAHs without five-membered rings with linear arrangement is longer than that of PAHs with nonlinear arrangement. According to the Franck–Condon principle, the vibrationally resolved electronic fluorescence spectra were obtained. The results show that fluorescence bandwidth of the PAHs with five-membered rings is much broader than that of the PAHs without five-membered rings. The concentration of PAHs was calculated by using the premixed flat-flame model with KM2 mechanism. On the basis of the fluorescence bandwidth and the concentration of the PAHs, the potentially fluorescence distribution of PAHs in flame was mapped. One can distinguish the specific PAHs according to the mapped fluorescence distribution of PAHs in this study. It was found that naphthalene should be responsible for the fluorescence located in the 312–340 nm region in the flame. 1-Ethynylnaphthalene is the most possible candidate to emit the fluorescence located in the 360–380 nm region. The fluorescence signals with the wavelength longer than 500 nm are likely emitted by the PAHs with five-membered rings. This study contributes to enhance the selectivity of PAHs in LIF technology, especially in the visible region

Investigating the Role of CH₂ Radicals in the HACA Mechanism

Detailed mechanisms of PAH growth involving methylene (CH₂) were studied using accurate ab initio density functional theory B3LYP/6-311+G­(d,p) calculations, as well as approximate QCISD­(T,full)/6-311++G­(3df,2pd) calculations. The PAH growth can be divided into five essential reaction steps, namely, addition C₂H₂ → intramolecular hydrogen migration → addition CH₂ → cyclization → H-elimination. The aliphatic species of indene and 1H-phenalene are found in the pathways of PAH growth, which is in accord with the experimental results that reveal the formation of aliphatic species in flames. It was found that the simultaneous removal of two H atoms in one reaction step is feasible in PAH evolution, and this can reasonably interpret the absence of a H atom in the post-flame region. The corresponding rate coefficients at 1 atm were evaluated by using TST and RRKM theory by solving the master equations in the temperature range of 500–2500 K. The calculated branching ratios suggest that the pathways involving CH₂ are competitive in PAH growth

Depth-Resolved Chemical Modification of Porous Silicon by Wavelength-Tuned Irradiation

The ability to impart discrete surface chemistry to the inside and outside of mesoporous silicon is of great importance for a range of biomedical applications, from selective (bio)­sensing to tissue-specific drug delivery. Here we present a generic strategy toward achieving depth-resolved functionalization of the external and internal porous surfaces by a simple change in the wavelength of the light being used to promote surface chemical reactions. UV-assisted hydrosilylation, limited by the penetration depth of UV light, is used to decorate the outside of the mesoporous structure with carboxylic acid molecules, and white light illumination triggers the attachment of dialkyne molecules to the inner porous matrix

Identification and Validation of Inhibitor-Responsive Kinase Substrates Using a New Paradigm To Measure Kinase-Specific Protein Phosphorylation Index

Regulation of all cellular processes requires dynamic regulation of protein phosphorylation. We have developed an unbiased system to globally quantify the phosphorylation index for substrates of a specific kinase by independently quantifying phosphorylated and total substrate molecules in a reverse in-gel kinase assay. Non-phosphorylated substrate molecules are first quantified in the presence and absence of a specific stimulus. Total substrate molecules are then measured after complete chemical dephosphorylation, and a ratio of phosphorylated to total substrate is derived. To demonstrate the utility of this approach, we profiled and quantified changes in phosphorylation index for Protein Kinase CK2 substrates that respond to a small-molecule inhibitor. A broad range of inhibitor-induced changes in phosphorylation was observed in cultured cells. Differences among substrates in the kinetics of phosphorylation change were also revealed. Comparison of CK2 inhibitor-induced changes in phosphorylation in cultured cells and in mouse peripheral blood lymphocytes <i>in vivo</i> revealed distinct kinetic and depth-of-response profiles. This technology provides a new approach to facilitate functional analyses of kinase-specific phosphorylation events. This strategy can be used to dissect the role of phosphorylation in cellular events, to facilitate kinase inhibitor target validation studies, and to inform <i>in vivo</i> analyses of kinase inhibitor drug efficacy

Antibody Modified Porous Silicon Microparticles for the Selective Capture of Cells

Herein, the ability of porous silicon (PSi) particles for selectively binding to specific cells is investigated. PSi microparticles with a high reflectance band in the reflectivity profile are fabricated, and subsequently passivated and modified with antibodies via the Cu­(I)-catalyzed alkyne–azide cycloaddition reaction and succimidyl activation. To demonstrate the ability of the antibody-modified PSi particles to selectively bind to one cell type over others, HeLa cells were transfected with surface epitopes fused to fluorescent proteins. The antibody-functionalized PSi particles showed good selectivity for the corresponding surface protein on HeLa cells, with no significant cross-reactivity. The results are important for the application of PSi particles in cell sensing and drug delivery

Photolithographic Strategy for Patterning Preformed, Chemically Modified, Porous Silicon Photonic Crystal Using Click Chemistry

Porous silicon (PSi) is an ideal platform for label-free biosensing, and the development of porous silicon patterning will open a pathway to the development of highly parallel PSi biochips for detecting multiple analytes. The optical response of PSi photonic crystal is determined by the changes in the effective bulk refractive index resulting from reactions/events occurring within the internal pore space. Therefore, introducing precise chemical functionalities in the pores of PSi is essential to ensure device selectivity. Here we describe the fabrication of PSi patterns that possess discrete chemical functionalities that are restricted to precise locations. The key difference to previous patterning protocols for PSi is that the entire porous material is first modified with a self-assembled monolayer of a α,ω-diyne adsorbate prior to patterning using a microfabricated titanium mask. The distal alkyne moieties in the monolayer are then amenable to further selective modification by the archetypal “click” reaction, the copper catalyzed alkyne–azide cycloaddition (CuAAC), using the titanium mask as a resist. This type of patterning is suitable for further immobilization of biological recognition elements, and presents a new platform for highly parallel PSi biosensor for multiple detections

Le Courrier

01 septembre 18241824/09/01 (A0,N245)

Notch3 Interactome Analysis Identified WWP2 as a Negative Regulator of Notch3 Signaling in Ovarian Cancer

<div><p>The Notch3 signaling pathway is thought to play a critical role in cancer development, as evidenced by the <i>Notch3</i> amplification and rearrangement observed in human cancers. However, the molecular mechanism by which Notch3 signaling contributes to tumorigenesis is largely unknown. In an effort to identify the molecular modulators of the Notch3 signaling pathway, we screened for Notch3-intracellular domain (N3-ICD) interacting proteins using a human proteome microarray. Pathway analysis of the Notch3 interactome demonstrated that ubiquitin C was the molecular hub of the top functional network, suggesting the involvement of ubiquitination in modulating Notch3 signaling. Thereby, we focused on functional characterization of an E3 ubiquitin-protein ligase, WWP2, a top candidate in the Notch3 interactome list. Co-immunoprecipitation experiments showed that WWP2 interacted with N3-ICD but not with intracellular domains from other Notch receptors. Wild-type WWP2 but not ligase-deficient mutant WWP2 increases mono-ubiquitination of the membrane-tethered Notch3 fragment, therefore attenuating Notch3 pathway activity in cancer cells and leading to cell cycle arrest. The mono-ubiquitination by WWP2 may target an endosomal/lysosomal degradation fate for Notch3 as suggested by the fact that the process could be suppressed by the endosomal/lysosomal inhibitor. Analysis of The Cancer Genome Atlas dataset showed that the majority of ovarian carcinomas harbored homozygous or heterozygous deletions in WWP2 locus, and there was an inverse correlation in the expression levels between WWP2 and Notch3 in ovarian carcinomas. Furthermore, ectopic expression of WWP2 decreased tumor development in a mouse xenograft model and suppressed the Notch3-induced phenotypes including increase in cancer stem cell-like cell population and platinum resistance. Taken together, our results provide evidence that WWP2 serves as a tumor suppressor by negatively regulating Notch3 signaling in ovarian cancer.</p></div

Additional file 6: of Comparative transcriptome and proteome profiling of two Citrus sinensis cultivars during fruit development and ripening

Analysis of co-expression of proteins and cognate mRNA identified at fruit delayed-harvest stage between two cultivars. (XLSX 478 kb