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261.
Laura Sbrcea Ionu-Mihai Tnase Adriana Ledei Denisa Cîrcioban Gabriela Vlase Paul Barvinschi Marinela Miclu Renata-Maria Vru Cristina Trandafirescu Ionu Ledei 《Molecules (Basel, Switzerland)》2020,25(23)
Risperidone (RSP) is an atypical antipsychotic drug which acts as a potent antagonist of serotonin-2 (5TH2) and dopamine-2 (D2) receptors in the brain; it is used to treat schizophrenia, behavioral and psychological symptoms of dementia and irritability associated with autism. It is a poorly water soluble benzoxazole derivative with high lipophilicity. Supramolecular adducts between drug substance and two methylated β-cyclodextrins, namely heptakis(2,6-di-O-methyl)-β-cyclodextrin (DM-β-CD) and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TM-β-CD) were obtained in order to enhance RSP solubility and improve its biopharmaceutical profile. The inclusion complexes were evaluated by means of thermoanalytical methods (TG—thermogravimetry/DTG—derivative thermogravimetry/HF—heat flow), powder X-ray diffractometry (PXRD), universal-attenuated total reflectance Fourier transform infrared (UATR-FTIR), UV spectroscopy and saturation solubility studies. Job’s method was employed for the determination of the stoichiometry of the inclusion complexes, which was found to be 2:1 for both guest–host systems. Molecular modeling studies were carried out for an in-depth characterization of the interaction between drug substance and cyclodextrins (CDs). The physicochemical properties of the supramolecular systems differ from those of RSP, demonstrating the inclusion complex formation between drug and CDs. The RSP solubility was enhanced as a result of drug encapsulation in the CDs cavity, the higher increase being obtained with DM-β-CD as host; the guest–host system RSP/DM-β-CD can thus be a starting point for further research in developing new formulations containing RSP, with enhanced bioavailability. 相似文献
262.
Gülhan Turan Begüm Nurpelin Sağlik Ulviye Acar Çevik Serkan Levent Betül Kaya Çavuşoğlu 《Phosphorus, sulfur, and silicon and the related elements》2020,195(6):491-497
AbstractIn this study, a novel series of benzothiazole-thiazolylhydrazine (3a–3i) was synthesized and their structures were characterized by 1H-NMR, 13C-NMR spectrometry, and mass spectroscopy. These compounds were evaluated as inhibitors of type A and type B monoamine oxidase (MAO) enzymes. The most active compound 3b (2-((2-(2-(4-(4-Nitrophenyl)thiazol-2-yl)hydrazineylidene)-2-phenylethyl)thio)benzothiazole) showed strong inhibitory activity at hMAO-A (IC50 of 0.095?±?0.004?µM). Furthermore, compound 3i (2-((2-(2-(4-(2,4-dichlorophenyl)thiazol-2-yl)hydrazineylidene)-2-phenylethyl)thio)benzothiazole) showed significant inhibition profile on hMAO-A with the IC50 values 0.141?±?0.006?µM. 相似文献
263.
N. Stipanelov Vrandečić I. Klarić U. Roje 《Journal of Thermal Analysis and Calorimetry》2001,65(3):907-918
The thermal degradation of poly(vinyl chloride)/chlorinated poly(ethylene) (PVC/CPE) blends of different compositions was
investigated by means of dynamic and isothermal thermogravimetric analysis in flowing atmosphere of nitrogen. Kinetic parameters
(the apparent activation energy E, and pre-exponential factor Z) were calculated after Flynn-Wall-Ozawa method for the first stage of dynamic degradation of PVC/CPE blends, and after Flynn
method for the isothermal degradation. In both cases, there is the compensation dependence between the values E and logZ. The values of compensation ratios as well as the characteristics of TG and DTG curves, confirm the stabilizing effect of
CPE on PVC dehydrochlorination.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
264.
We report on the application of a simple and versatile antioxidant capacity assay for dietary polyphenols, vitamin C and vitamin
E utilizing the copper(II)-neocuproine (Cu(II)-Nc) reagent as the chromogenic oxidant, which we term the CUPRAC (cupric reducing
antioxidant capacity) method. It involves mixing the antioxidant solution (directly or after acid hydrolysis) with solutions
of CuCl2, neocuproine, and ammonium acetate at pH 7, and measuring the absorbance at 450 nm after 30 min. Slowly reacting antioxidants
required an incubation at 50 °C for 20 min for color development. The flavonoid glycosides were hydrolyzed to their corresponding
aglycones by refluxing in 1.2 M HCl-containing 50% MeOH for fully exhibiting their antioxidant potencies. Certain compounds
also needed incubation after acid hydrolysis for color development. The CUPRAC absorbances of mixture constituents were additive,
indicating lack of chemical deviations from Beer’s law. The CUPRAC antioxidant capacities of a wide range of polyphenolics
are reported in this work and compared to those found by ABTS/persulfate and Folin assays. The trolox-equivalent capacities
of the antioxidants were linearly correlated (r = 0.8) to those found by ABTS but not to those of Folin. The highest antioxidant capacities in the CUPRAC method were observed
for epicatechin gallate, epigallocatechin gallate, quercetin, fisetin, epigallocatechin, catechin, caffeic acid, epicatechin,
gallic acid, rutin, and chlorogenic acid in this order, in accordance with theoretical expectations. The experiences of other
CUPRAC users also are summarized.
Correspondence: Reşat Apak, Department of Chemistry, Faculty of Engineering, Istanbul University, Avcilar, TR-34320 Istanbul,
Turkey 相似文献
265.
In this work, a sensitive, practical and reliable acetylthiocholine (ATCh) biosensor based on poly(allylamine hydrochloride) functionalized multiwalled carbon nanotube (PAH/MWCNT) was fabricated and used for pesticide detection. As far as we know, this is the first work that constitutes the usage of PAH and MWCNT for ATCh biosensor. The developed system was characterized by using scanning electron microscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The influence of parameters such as enzyme amount and pH were examined and a linearity between 5×10?5 M?2.0×10?3 M for ATCh was obtained. The proposed biosensor was applied for a model pesticide, monocrotophos, detection. The analytical curve showed an excellent linearity in the monocrotophos concentration range of 1–25 pg/mL with an incubation time of 5 min. Limit of detection and limit of quantification values were calculated as 0.88 and 2.9 pg/mL, respectively. The system was also applied for detection of monocrotophos in grape, tomatoe, tap and mineralized water samples and promising recovery values were obtained. 相似文献
266.
Remziye Güzel Haslet Ekşi Zafer Üstündağ Ali Osman Solak 《Surface and interface analysis : SIA》2013,45(13):1821-1829
In this study, 4‐thiophenol modified glassy carbon electrode was prepared by the reduction of 4‐diazothiophenol tetrafluoroborate salt. Silver nanoparticles were attached to the thiophenol modified surface to prepare a thiophenol‐silver nanoparticle composite film. 4‐Aminothiopenol molecules were deposited by self‐assembling technique to form multi‐layered nanofilms of TP/SNP/PhNH2 on glassy carbon substrate. These surfaces were characterized by cyclic voltammetry, electrochemical impedance spectroscopy, X‐ray photoelectron spectroscopy, reflectance‐absorption infrared spectroscopy, and ellipsometry at each multilayer film growth process. Atomic force microscopic images of GC/TP/SNP/PhNH2 surfaces were also acquired. The characterization methods show that the amine group containing surface permits the subsequent modification by a variety of coupling reactions for the immobilization of more complex systems. An application of the electrode modification for the determination of uric acid with a significantly lower detection limit is described. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
267.
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268.
Selda Kabatas Paola Agüi‐Gonzalez Kim‐Ann Saal Sebastian Jhne Felipe Opazo Silvio O. Rizzoli Nhu T. N. Phan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(11):3476-3481
Boron has been employed in materials science as a marker for imaging specific structures by electron energy loss spectroscopy (EELS) or secondary ion mass spectrometry (SIMS). It has a strong potential in biological analyses as well; however, the specific coupling of a sufficient number of boron atoms to a biological structure has proven challenging. Herein, we synthesize tags containing closo‐1,2‐dicarbadodecaborane, coupled to soluble peptides, which were integrated in specific proteins by click chemistry in mammalian cells and were also coupled to nanobodies for use in immunocytochemistry experiments. The tags were fully functional in biological samples, as demonstrated by nanoSIMS imaging of cell cultures. The boron signal revealed the protein of interest, while other SIMS channels were used for imaging different positive ions, such as the cellular metal ions. This allows, for the first time, the simultaneous imaging of such ions with a protein of interest and will enable new biological applications in the SIMS field. 相似文献
269.
Tereza Tůmová Lenka Monincová Václav Čeřovský Václav Kašička 《Electrophoresis》2016,37(23-24):3186-3195
Capillary electrophoresis (CE) was employed for the determination of thermodynamic acidity constants (pKa) and actual ionic mobilities of polycationic antimicrobial peptides (AMPs). The effective electrophoretic mobilities of AMPs were measured by CE in a series of the background electrolytes within a wide pH range (2.00–12.25), at constant ionic strength (25 mM) and ambient temperature, using polybrene coated fused silica capillaries to suppress sorption of cationic AMPs to the capillary wall. Eventually, Haarhoff–Van der Linde peak fitting function was used for the determination of correct migration times of some AMPs peaks that were distorted by electromigration dispersion. The measured effective mobilities were corrected to 25°C. Mixed acidity constants, , and actual ionic mobilities, mi, of AMPs were determined by the nonlinear regression analysis of pH dependence of their effective mobilities. The values were recalculated to thermodynamic pKas using the Debye–Hückel theory. Thermodynamic pKa of imidazolium group of histidine residues was found to be in the range 3.72–4.98, pKa of α‐NH3+ group was in the range 6.14–6.93, and pKa of ε‐NH3+ group of lysine spanned the interval 7.26–9.84, depending on the particular amino acid sequence of the AMPs. Actual ionic mobilities of AMPs with positive charges from one to six elementary units achieved values (9.8 – 36.5) × 10?9 m2V?1s?1. 相似文献
270.
Sibe Marde
i 《Topology and its Applications》1988,30(3):291-306
The well-known factorization theorems for covering dimension dim and compact Hausdorff spaces are here established for the cohomological dimension dim
using a new characterization of dim
In particular, it is proved that every mapping f: X → Y from a compact Hausdorff space X with
to a compact metric space Y admits a factorization f = hg, where g: X → Z, h: Z → Y and Z is a metric compactum with
. These results are applied to the well-known open problem whether
. It is shown that the problem has a positive answer for compact Hausdorff spaces X if and only if it has a positive answer for metric compacta X. 相似文献