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471.
472.
Isaak Beyer Dr. Nasrollah Rezaei‐Ghaleh Dr. Hans‐Wolfgang Klafki Dr. Olaf Jahn Dr. Ute Haußmann Prof. Dr. Jens Wiltfang Prof. Dr. Markus Zweckstetter Prof. Dr. Hans‐Joachim Knölker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(25):8685-8693
In addition to the prototypic amyloid‐β (Aβ) peptides Aβ1–40 and Aβ1–42, several Aβ variants differing in their amino and carboxy termini have been described. Synthetic availability of an Aβ variant is often the key to study its role under physiological or pathological conditions. Herein, we report a protocol for the efficient solid‐phase peptide synthesis of the N‐terminally elongated Aβ‐peptides Aβ?3–38, Aβ?3–40, and Aβ?3–42. Biophysical characterization by NMR spectroscopy, CD spectroscopy, an aggregation assay, and electron microscopy revealed that all three peptides were prone to aggregation into amyloid fibrils. Immunoprecipitation, followed by mass spectrometry, indicated that Aβ?3–38 and Aβ?3–40 are generated by transfected cells even in the presence of a tripartite β‐site amyloid precursor protein cleaving enzyme 1 (BACE1) inhibitor. The elongated Aβ peptides starting at Val(?3) can be separated from N‐terminally‐truncated Aβ forms by high‐resolution isoelectric‐focusing techniques, despite virtually identical isoelectric points. The synthetic Aβ variants and the methods presented here are providing tools to advance our understanding of the potential roles of N‐terminally elongated Aβ variants in Alzheimer's disease. 相似文献
473.
Somayeh Zanganeh Safoora Khosravi Naser Namdar Morteza Hassanpour Amiri Milad Gharooni Mohammad Abdolahad 《Analytica chimica acta》2016
One of the most interested molecular research in the field of cancer detection is the mechanism of drug effect on cancer cells. Translating molecular evidence into electrochemical profiles would open new opportunities in cancer research. In this manner, applying nanostructures with anomalous physical and chemical properties as well as biocompatibility would be a suitable choice for the cell based electrochemical sensing. Silicon based nanostructure are the most interested nanomaterials used in electrochemical biosensors because of their compatibility with electronic fabrication process and well engineering in size and electrical properties. Here we apply silicon nanograss (SiNG) probing electrodes produced by reactive ion etching (RIE) on silicon wafer to electrochemically diagnose the effect of anticancer drugs on breast tumor cells. Paclitaxel (PTX) and mebendazole (MBZ) drugs have been used as polymerizing and depolymerizing agents of microtubules. PTX would perturb the anodic/cathodic responses of the cell-covered biosensor by binding phosphate groups to deformed proteins due to extracellular signal-regulated kinase (ERK1/2) pathway. MBZ induces accumulation of Cytochrome C in cytoplasm. Reduction of the mentioned agents in cytosol would change the ionic state of the cells monitored by silicon nanograss working electrodes (SiNGWEs). By extending the contacts with cancer cells, SiNGWEs can detect minor signal transduction and bio recognition events, resulting in precise biosensing. Effects of MBZ and PTX drugs, (with the concentrations of 2 nM and 0.1 nM, respectively) on electrochemical activity of MCF-7 cells are successfully recorded which are corroborated by confocal and flow cytometry assays. 相似文献
474.
Elham Oveili Shohreh Jahani Omid Tayari Abbas Jahanara Zohreh Fazli Zahra Aramesh-Boroujeni Soroush Rashidi Nadia Rezaei Zade Baravati Mohammad Mehdi Foroughi 《Electroanalysis》2023,35(7):e202200432
The current work aimed to fabricate a new cocaine sensor of octahedral palladium-doped cobaltite composite (Oh-Pd2+ : Co3O4-C) using a simple hydrothermal protocol. As-fabricated cocaine sensing approach was validated by various methods. Energy dispersive X-ray analysis, X-ray diffraction and scanning electron microscopy were recruited to characterize our charged modified composite. The electrode could sensitively detect cocaine, with a lengthy linear range (0.01 μM–900.0 μM) and a limit of detection (1.3 nM). The quantitative cocaine determination was achieved in the biological specimens using our modified electrode, the results of which displayed admirable outcomes. 相似文献
475.
The complexes of lysozyme with the anionic surfactant sodium dodecyl sulfate (SDS) and the cationic surfactant dodecyltrimethylammonium
bromide (DTAB) have been investigated by isothermal titration calorimetry at pH=7.0 and 27 °C in a phosphate buffer. A new
direct calorimetric method was applied to follow the protein denaturation and study the effect of surfactants on the stability
of proteins. The extended solvation model was used to represent the enthalpies of lysozyme + SDS interaction over the whole
range of SDS concentrations. The solvation parameters recovered from the new equation are attributed to the structural change
of lysozyme and its biological activity. At low SDS concentrations, the binding is mainly electrostatic with some simultaneous
interaction of the hydrophobic tail with nearby hydrophobic regions of lysozyme. These initial interactions presumably cause
some protein unfolding and expose additional hydrophobic sites. The induced enthalpy of denaturation of lysozyme by SDS is
160.81±0.02 kJ⋅mol−1. The lysozyme-DTAB complexes behave very differently from those of the lysozyme-SDS complexes. SDS induces a stronger unfolding
of lysozyme than DTAB. The induced enthalpy of lysozyme denaturation by DTAB is 86.46±0.02 kJ⋅mol−1. 相似文献
476.
Mohammad Rahimizadeh Esmaeel Rezaei Seresht Neda Golari Mehdi Bakavoli 《Monatshefte für Chemie / Chemical Monthly》2008,139(6):639-645
Several new tetrabromo compounds based on diphenyl- and dimethylglycolurils were synthesized. Sequential treatment of these
compounds with imidazole, methyl iodide, and sodium tetrafluoroborate gave their corresponding tetra imidazolium salts. Some
of these compounds because of their low melting points can be registered as a potential and new class of ionic liquids.
Correspondence: Mehdi Bakavoli, Department of Chemistry, School of Sciences, Ferdowsi University, Mashhad 91375-1436, Iran. 相似文献
477.
Preparation and thermal treatment of Pd/Ag composite membrane on a porous alumina tube by sequential electroless plating technique for H2 separation
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E. Navaei Alvar M. Reza Golmohammadi M. Rezaei H. Navaei Alvar A. Mardanloo S. Habibzad Nouhian M. Didari 《天然气化学杂志》2008,17(4):321-326
Pd/Ag/α-Al2O3 composite membranes were prepared by sequential electroless plating technique. The prepared membranes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy, and inductively coupled plasma atomic emission spectroscopy techniques (ICP-AES). Effects of annealing time, Ag content, and air treatment on the hydrogen permeation flux and morphology of the alloys were investigated. The results of the investigation showed that the prepared type of tube had a good potential as substrate for membrane preparation. In addition, a uniform defect-free alloy was prepared by annealing at 550 ℃ in H2 atmosphere. The permeation results showed an increase in H2 permeation flux by increasing the Ag content and the annealing time. In addition, the air treatment of the prepared membranes at 400 ℃ for 1 h changed the morphology of the alloy and substantially enhanced the hydrogen flux. 相似文献
478.
Hasani M Rezaei A Abdollahi H 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,68(3):414-419
The H-point standard addition method was applied to kinetic data for simultaneous determination of Fe(II) and Fe(III) or selective determination of Fe(II) in the presence of Fe(III). The method is based on the difference in the rate of complex formation between iron in two different oxidation states and methylthymol blue (MTB) at pH 3.5 in mixed cetyltrimethylammonium bromide (CTAB) and Triton X-100 micellar medium. Fe(II) can be determined in the range 0.25-2.5 microg ml(-1) with satisfactory accuracy and precision in the presence of excess Fe(III) and other metal ions that rapidly form complexes with MTB under working condition. The proposed method was successfully applied to the simultaneous determination of Fe(II) and Fe(III) or selective determination of Fe(II) in the presence of Fe(III) in spiked real environmental and synthetic samples with complex composition. 相似文献
479.
CO2 reforming of methane (CDRM) was carried out over MgO supported Ni catalysts with various Ni loadings. The preparation of MgO supported Ni catalysts via surfactant-assisted precipitation method led to the formation of a nanocrystalline carrier for nickel catalysts. The synthesized samples were characterized by XRD, N2 adsorption-desorption, H2 chemisorption, TPR, TPO and SEM techniques. It was found that the high catalytic activity and stability of the prepared catalysts could be attributable to high dispersion of reduced Ni species and basicity of support surface. In addition, the effect of feed ratio, nickel loading and GHSV on the catalytic performance of CDRM over the catalysts were investigated. 相似文献
480.
Melamine-formaldehyde resin supported H~+ is used as an efficient catalyst in the Pechmann condensation reaction of phenols withβ-ketoesters,in solvent-free media leading to the formation of coumarin derivatives using conventional heating and microwave irradiation in excellent yields with good purity. 相似文献