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951.
Di- and tri-organotin(IV) derivatives of N -acetyltriglycine and N -benzoyltriglycine (HA) were obtained by refluxing equimolar mixtures of the ligand and the organotin(IV) oxide or hydroxide in methanol or acetone. According to the spectroscopic data, triorganotin(IV) derivatives adopt a trigonal-bipyramidal structure in which the planar R3SnIV unit is bonded by a monodentate carboxylate group and a donor group, presumably the amide CO. The reaction of HA with the appropriate diorganotin(IV) compounds gave both dicarboxylates R2SnA2, with six-coordinated tin, and dimeric tetraorganodistannoxanes {[R2SnA]2O}2, in which the tin atoms are essentially five-coordinated. 相似文献
952.
953.
Lauren M. Reid Ileana Guzzetti Tor Svensson Anna-Carin Carlsson Wu Su Tomas Leek Lena von Sydow Werngard Czechtizky Marija Miljak Chandra Verma Leonardo De Maria Jonathan W. Essex 《Chemical science》2022,13(7):1957
Understanding the conformational ensembles of intrinsically disordered proteins and peptides (IDPs) in their various biological environments is essential for understanding their mechanisms and functional roles in the proteome, leading to a greater knowledge of, and potential treatments for, a broad range of diseases. To determine whether molecular simulation is able to generate accurate conformational ensembles of IDPs, we explore the structural landscape of the PLP peptide (an intrinsically disordered region of the proteolipid membrane protein) in aqueous and membrane-mimicking solvents, using replica exchange with solute scaling (REST2), and examine the ability of four force fields (ff14SB, ff14IDPSFF, CHARMM36 and CHARMM36m) to reproduce literature circular dichroism (CD) data. Results from variable temperature (VT) 1H and Rotating frame Overhauser Effect SpectroscopY (ROESY) nuclear magnetic resonance (NMR) experiments are also presented and are consistent with the structural observations obtained from the simulations and CD. We also apply the optimum simulation protocol to TP2 and ONEG (a cell-penetrating peptide (CPP) and a negative control peptide, respectively) to gain insight into the structural differences that may account for the observed difference in their membrane-penetrating abilities. Of the tested force fields, we find that CHARMM36 and CHARMM36m are best suited to the study of IDPs, and accurately predict a disordered to helical conformational transition of the PLP peptide accompanying the change from aqueous to membrane-mimicking solvents. We also identify an α-helical structure of TP2 in the membrane-mimicking solvents and provide a discussion of the mechanistic implications of this observation with reference to the previous literature on the peptide. From these results, we recommend the use of CHARMM36m with the REST2 protocol for the study of environment-specific IDP conformations. We believe that the simulation protocol will allow the study of a broad range of IDPs that undergo conformational transitions in different biological environments.A protocol for simulating intrinsically disordered peptides in aqueous and hydrophobic solvents is proposed. Results from four force fields are compared with experiment. CHARMM36m performs the best for the simulated IDPs in all environments. 相似文献
954.
Pedro L. R. Guedes Carolina P. F. Carvalho Adriana A. F. Carbonel Manuel J. Simes Marcelo Y. Icimoto Jair A. K. Aguiar Maria Kouyoumdjian Marcos L. Gazarini Marcia R. Nagaoka 《Molecules (Basel, Switzerland)》2022,27(3)
During liver fibrogenesis, there is an imbalance between regeneration and wound healing. The current treatment is the withdrawal of the causing agent; thus, investigation of new and effective treatments is important. Studies have highlighted the action of chondroitin sulfate (CS) in different cells; thus, our aim was to analyze its effect on an experimental model of bile duct ligation (BDL). Adult Wistar rats were subjected to BDL and treated with CS for 7, 14, 21, or 28 days intraperitoneally. We performed histomorphometric analyses on Picrosirius-stained liver sections. Cell death was analyzed according to caspase-3 and cathepsin B activity and using a TUNEL assay. Regeneration was evaluated using PCNA immunohistochemistry. BDL led to increased collagen content with corresponding decreased liver parenchyma. CS treatment reduced total collagen and increased parenchyma content after 21 and 28 days. The treatment also promoted changes in the hepatic collagen type III/I ratio. Furthermore, it was observed that CS treatment reduced caspase-3 activity and the percentage of TUNEL-positive cells after 14 days and cathepsin B activity only after 28 days. The regeneration increased after 14, 21, and 28 days of CS treatment. In conclusion, our study showed a promising hepatoprotective action of CS in fibrogenesis induced by BDL. 相似文献
955.
Saida Sissi Silvia Di Giacomo Claudio Ferrante Paola Angelini Alberto Macone Anna Maria Giusti Chiara Toniolo Annabella Vitalone Aghraz Abdellah Mustapha Larhsini Luigi Menghini Mohammed Markouk Gabriela Mazzanti Antonella Di Sotto 《Molecules (Basel, Switzerland)》2022,27(3)
In the present study, the phytochemical composition and bioactivities of A. maroccanus (AM) and A. radiatus (AR), two ecotypes collected in the Demnate road and Essaouira regions, respectively, were studied to highlight a pharmacological interest and to enable possible pharmaceutical development. To this end, methanolic and ethyl acetate extracts were prepared for each ecotype by fractionation; next, their phytochemical composition was evaluated by spectrophotometric and chromatographic analysis. Moreover, in line with the available evidence for Anacyclus spp. and their traditional use, a screening of bioactivities, including antioxidant, hypoglycemic, antiglycative, chelating, and antibacterial activities, was performed. The extracts were characterized by high amounts of polyphenols, tannins, and flavonoids, especially in the methanolic extracts; these samples were also enriched in carotenoids despite a lower chlorophyll content. Chlorogenic acid and rutin were the major identified compounds. The extracts also showed interesting hypoglycemic, antiglycative, and antibacterial properties, although with differences in efficacy and potency. Present results provide more scientific basis to the ethnopharmacological uses of Anacyclus spp. and suggest a further interest in AM and AR ecotypes as natural sources of bioactive compounds and/or phytocomplexes for possible pharmaceutical and nutraceutical developments. 相似文献
956.
The thermal degradation behaviour, in the absence of oxygen, of poly(p-methylstyrene) has been investigated. Monomer is the main product formed in the degradation process, together with different oligomers which have been identified and whose amounts have been determined. A reaction mechanism accounting for the formation of the degradation products, and similar to the mechanism established for polystyrene, is proposed. The main differences of the process comparing with polystyrene are the higher amount of monomer which is produced and the crosslinking structures which are formed at T < 400° C. 相似文献
957.
958.
Iacus Stefano Maria Santamaria Carlos Sermi Francesco Spyratos Spyros Tarchi Dario Vespe Michele 《Nonlinear dynamics》2020,101(3):1901-1919
Nonlinear Dynamics - Countries in Europe took different mobility containment measures to curb the spread of COVID-19. The European Commission asked mobile network operators to share on a... 相似文献
959.
Incoronata Tritto Maria Carmela Sacchi Paolo Locatelli San Xi Li 《Macromolecular Symposia》1995,89(1):289-298
The reaction equilibria of Cp2Ti13CH3Cl and Cp2Ti(CH3)2 with AlMe3 (TMA) and/or methylaluminoxane (MAO) have been investigated by 13C NMR. Several adducts have been identified. A study of the 13C 90% enriched ethylene polymerization in an NMR tube in the presence of the above catalytic systems, in the most experimentally significant conditions, and a comparison of the NMR data with the catalytic activity have been made as well. It has been shown that: i) some species are side products, inactive for addition ethylene polymerization; ii) active cation-like species such as Cp2TiMe+Cl·[AlMeO]n- and Cp2TiMe+Me·[AlMeO]n- are formed in titanocene-MAO systems. Concerning the role of AlMe3, contained in MAO solutions, it has been shown that: a) AlMe3 is mainly bound to MAO; b) if some “free” AlMe3 exists in solution it is not the actual cocatalyst in the metallocene-MAO based catalytic systems; c) the amount of AlMe3 influences either active or inactive species. 相似文献
960.
The effect of shear flow on the phase behaviour of partially miscible blends exhibiting a lower critical solution temperature behaviour has been investigated. Miscibility limits were detected, with and without the application of flow, as changes from optical clarity to turbidity using light scattering and as the appearance of double glass transition temperatures. Light scattering data were collected on a rheo-optical device that was designed to monitor phase changes in polymer blends undergoing shear flow between parallel glass plates in a temperature controlled environment. Glass transition temperatures of some quenched sheared blends were measured using a differential scanning calorimeter in order to confirm the conclusions from the light scattering data. It was found that shear induced demixing and shear induced mixing may be observed within the same blend depending on the magnitude of the applied flow. Miscibility gaps and closed miscibility loops may appear in the phase diagrams. At certain temperatures and shear rates unusual scattering patterns were observed and these were associated with a “ripple” morphology when directly viewed through the microscope. 相似文献