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341.
Martin A. Schroer Po-Sheng Hu Natalia Tomasovicova Marianna Batkova Katarina Zakutanska Po-Yi Wu Peter Kopcansky 《Molecules (Basel, Switzerland)》2021,26(16)
Understanding the formation process and the spatial distribution of nanoparticle (NP) clusters on amyloid fibrils is an essential step for the development of NP-based methods to inhibit aggregation of amyloidal proteins or reverse the assembling trend of the proto-fibrillary complexes that prompts pathogenesis of neuro degeneration. For this, a detailed structural determination of the diverse hybrid assemblies that are forming is needed, which can be achieved by advanced X-ray scattering techniques. Using a combined solution small angle X-ray scattering (SAXS) and atomic force microscopy (AFM) approach, this study investigates the intrinsic trends of the interaction between lysozyme amyloid fibrils (LAFs) and Fe3O4 NPs before and after fibrillization at nanometer resolution. AFM images reveal that the number of NP clusters interacting with the lysozyme fibers does not increase significantly with NP volume concentration, suggesting a saturation in NP aggregation on the fibrillary surface. The data indicate that the number of non-adsorbed Fe3O4 NPs is highly dependent on the timing of NP infusion within the synthesis process. SAXS data yield access to the spatial distribution, aggregation manner and density of NP clusters on the fibrillary surfaces. Employing modern data analysis approaches, the shape and internal structural morphology of the so formed nanocomposites are revealed. The combined experimental approach suggests that while Fe3O4 NPs infusion does not prevent the fibril-formation, the variation of NP concentration and size at different stages of the fibrillization process can impose a pronounced impact on the superficial and internal structural morphologies of these nanocomposites. These findings may be applicable in devising advanced therapeutic treatments for neurodegenerative diseases and designing novel bio-inorganic magnetic devices. Our results further demonstrate that modern X-ray methods give access to the structure of—and insight into the formation process of—biological–inorganic hybrid structures in solution. 相似文献
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344.
János Farkas Sándor Békássy Béla Ágai Marianna Hegedüs François Figueras 《合成通讯》2013,43(14):2479-2485
Using a series of clay based catalysts (KSF, KSF/0, KP10, K10, K0, KS), resorcinol is acylated in 1,2-dichloroethane by phenylacetyl chloride with a heterogeneous catalytic procedure. The yield of 1-(2,4-dihydroxyphenyl)-2-phenyl-ethanone is in correlation with the specific surface area of the catalyst. 相似文献
345.
Marianna Rossetti Simone Brannetti Marco Mocenigo Bruna Marini Rudy Ippodrino Alessandro Porchetta 《Angewandte Chemie (International ed. in English)》2020,59(35):14973-14978
Easy‐to‐use platforms for rapid antibody detection are likely to improve molecular diagnostics and immunotherapy monitoring. However, current technologies require multi‐step, time‐consuming procedures that limit their applicability in these fields. Herein, we demonstrate effective molarity‐driven electrochemical DNA‐based detection of target antibodies. We show a highly selective, signal‐on DNA‐based sensor that takes advantage of antibody‐binding‐induced increase of local concentration to detect clinically relevant antibodies in blood serum. The sensing platform is modular, rapid, and versatile and allows the detection of both IgG and IgE antibodies. We also demonstrate the possible use of this strategy for the monitoring of therapeutic monoclonal antibodies in body fluids. Our approach highlights the potential of harnessing effective molarity for the design of electrochemical sensing strategies. 相似文献
346.
Marianna Teplova Christoph Falschlunger Olga Krasheninina Michaela Egger Aiming Ren Dinshaw J. Patel Ronald Micura 《Angewandte Chemie (International ed. in English)》2020,59(7):2837-2843
Pistol ribozymes constitute a new class of small self‐cleaving RNAs. Crystal structures have been solved, providing three‐dimensional snapshots along the reaction coordinate of pistol phosphodiester cleavage, corresponding to the pre‐catalytic state, a vanadate mimic of the transition state, and the product. The results led to the proposed underlying chemical mechanism. Importantly, a hydrated Mg2+ ion remains innersphere‐coordinated to N7 of G33 in all three states, and is consistent with its likely role as acid in general acid base catalysis (δ and β catalysis). Strikingly, the new structures shed light on a second hydrated Mg2+ ion that approaches the scissile phosphate from its binding site in the pre‐cleavage state to reach out for water‐mediated hydrogen bonding in the cyclophosphate product. The major role of the second Mg2+ ion appears to be the stabilization of product conformation. This study delivers a mechanistic understanding of ribozyme‐catalyzed backbone cleavage. 相似文献
347.
Marianna Nytka Lucie Borovcov Petr Fry
k Petr Bartk Karel Lemr 《Journal of mass spectrometry : JMS》2020,55(10)
The efficiency of desorption/ionization becomes more critical as the sampled surface area decreases. Desorption electrospray and desorption nanoelectrospray belong to ambient ionizations and enable direct surface analysis including mass spectrometric imaging. Lateral resolution in tens of micrometers was demonstrated for desorption nanoelectrospray previously, but sensitivity of the surface scan can be an issue. For desorption electrospray, the drag force in the source is driven by the flow of used gases and vacuum suction. Ion signal intensity can be improved by controlling the nebulizing gas flow rate or auxiliary pumping of a closed compartment in front of the mass spectrometer inlet. Because nanoelectrospray generates charged droplets without the assistance of a nebulizing gas, only vacuum suction drives the gas flow. In this study, the effect of pressure drop between the atmospheric and evacuated region of a mass spectrometer on the ion signal intensity was investigated for desorption nanoelectrospray. A modification of the commercial inlet was designed. An auxiliary pump was directly connected to an inner compartment of the modified mass spectrometer inlet through a needle valve that enabled the regulation of the reduced pressure. Adjustment of the pressure drop significantly increased signal intensity (more than one order of magnitude in some cases). To a lesser extent, the temperature of a heated capillary (an integral part of the inlet) also influenced the signal intensity. The applicability of desorption nanoelectrospray equipped with pressure regulation was demonstrated by the analysis of synthetic cathinones or a pill of paracetamol. Because pressure in the inlet depends on the diameters of orifices and the power of vacuum systems of mass spectrometers, the effect of the pressure regulation can be different for different instruments. Nevertheless, the presented results confirmed the importance of pressure drop‐driven transport for desorption nanoelectrospray efficiency and can encourage its new applications. 相似文献
348.
Małgorzata Pająk Katarzyna Pałka Elżbieta Winnicka Marianna Kańska 《Journal of Radioanalytical and Nuclear Chemistry》2018,317(2):643-666
This review compiles the combined chemical and enzymatic synthesis of aromatic l-amino acids (l-phenylalanine, l-tyrosine, l-DOPA, l-tryptophan, and their derivatives and precursors) specifically labeled with carbon and hydrogen isotopes, which were elaborated in our research group by the past 20 years. These compounds could be then employed to characterize the mechanisms of enzymatic reactions via kinetic and solvent isotope effects methods. 相似文献
349.
Cristofari Andrea De Santis Marianna Lucidi Stefano Rinaldi Francesco 《Computational Optimization and Applications》2022,83(2):693-721
Computational Optimization and Applications - The $$\ell _1$$ -ball is a nicely structured feasible set that is widely used in many fields (e.g., machine learning, statistics and signal analysis)... 相似文献
350.
An enantiopure diselenide based on a chiral bicyclic backbone—synthesis and configuration assignment
Karolina Kamińska Elżbieta Wojaczyńska Claudio Santi Luca Sancineto Marianna Francesca Pensa Andrzej Kochel Robert Wieczorek Jacek Wojaczyński Gauthier Slupski 《Tetrahedron: Asymmetry》2017,28(10):1367-1372
An enantiomerically pure diselenide containing two chiral bicyclic subunits was prepared from the respective halides. The stereochemical outcome of the reaction was established via NMR spectroscopy and X-ray diffraction measurements. 相似文献