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排序方式: 共有940条查询结果,搜索用时 31 毫秒
211.
Sebestyén Zoltán Jakab Emma Domán Andrea Bokrossy Péter Bertóti Imre Madarász János László Krisztina 《Journal of Thermal Analysis and Calorimetry》2020,141(1):301-312
Journal of Thermal Analysis and Calorimetry - The refrigerator unit based on electrically driven vapor compression technology consumes high energy, associated with high cost and loss of ecosystem.... 相似文献
212.
Emma van Groesen Dr. Christopher T. Lohans Dr. Jürgen Brem Kristina M. J. Aertker Prof. Dr. Timothy D. W. Claridge Prof. Dr. Christopher J. Schofield 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(51):11837-11841
Bacterial production of β-lactamases with carbapenemase activity is a global health threat. The active sites of class D carbapenemases such as OXA-48, which is of major clinical importance, uniquely contain a carbamylated lysine residue which is essential for catalysis. Although there is significant interest in characterizing this post-translational modification, and it is a promising inhibition target, protein carbamylation is challenging to monitor in solution. We report the use of 19F NMR spectroscopy to monitor the carbamylation state of 19F-labelled OXA-48. This method was used to investigate the interactions of OXA-48 with clinically used serine β-lactamase inhibitors, including avibactam and vaborbactam. Crystallographic studies on 19F-labelled OXA-48 provide a structural rationale for the sensitivity of the 19F label to active site interactions. The overall results demonstrate the use of 19F NMR to monitor reversible covalent post-translational modifications. 相似文献
213.
Letters in Mathematical Physics - A recent generalization of the “Kleinian sigma function” involves the choice of a point P of a Riemann surface X, namely a “pointed curve”... 相似文献
214.
Emma R. L. Brisson James C. Griffith Ayana Bhaskaran George V. Franks Luke A. Connal 《Journal of polymer science. Part A, Polymer chemistry》2019,57(18):1964-1973
Histidine functional block copolymers are thermally self‐assembled into polymer micelles with poly‐N‐isopropylacrylamide in the core and the histidine functionality in the corona. The thermally induced self‐assemblies are reversible until treated with Cu2+ ions at 50 °C. Upon treatment with 0.5 equivalents of Cu2+ relative to the histidine moieties, metal‐ion coordination locks the self‐assemblies. The self‐assembly behavior of histidine functional block copolymers is explored at different values of pH using DLS and 1H NMR. Metal‐ion coordination locking of the histidine functional micelles is also explored at different pH values, with stable micelles forming at pH 9, observed by DLS and imaged by atomic force microscopy. The thermal self‐assembly of glycine functional block copolymers at pH 5, 7, and 9 is similar to the histidine functional materials; however, the self‐assemblies do not become stable after the addition of Cu2+, indicating that the imidazole plays a crucial role in metal‐ion coordination that locks the micelles. The reversibility of the histidine‐copper complex locking mechanism is demonstrated by the addition of acid to protonate the imidazole and destabilize the polymer self‐assemblies. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1964–1973 相似文献
215.
Peter Kaali Emma Strömberg György Czél Sigbritt Karlsson 《Polymer Degradation and Stability》2010,95(9):1456-1465
In biomedical applications, tubes (e.g. catheters etc.) are commonly produced from polyurethane (PU) and silicone rubber which are known to be biocompatible materials. Several studies have shown that tubes, which are connected to the body (invasive) (especially urinary, tracheotomy and central venous catheters) are associated with infections. The present study reports the development of a new method aiming at obtaining antibacterial properties for PU and silicone rubber by mixing respective material with a natural antibacterial agent (Ag+ loaded zeolite) in different weight fractions. The influence of the zeolite content on the antimicrobial properties were analysed by exposure to bacteria (ISO 22196) and mixtures of fungi (ISO 846). The materials were also subject to artificial body fluids (Artificial Lysosomal Fluid (ALF) and Gamble’s solution) for periods up to three months and the subsequent changes in the chemical properties after in-vitro exposure were determined by Matrix Assisted Laser Deposition/Ionization Time Of Flight Mass Spectrometry (MALDI-TOF MS) and Attenuated Total Reflection Fourier Transform Infra Red spectroscopy (ATR-FTIR). It was established that the antimicrobial effect of the materials increased with the increase of the zeolite content. The wettability of the materials was found to decrease significantly during the in-vitro exposure, but this could not be correlated to the zeolite content. In the PU samples, the formation of free carbonyl and -OH groups was observed, which corresponds to oxidative degradation. In case of the silicone rubber the ratio of cyclic PDMS to linear PDMS (H, CH3 and dimethyl terminated) decreased, which indicates a change in the concentration of the compounds. The formation and increase of the O-H bond during the exposure was also confirmed by the infrared spectra of the material which corresponds to hydrolysis of the silicone rubber. 相似文献
216.
217.
Hanan Alatawi Anna Hogan Ibtihaj Albalawi Emma O'Sullivan-Carroll Samia Alsefri Yineng Wang Eric Moore 《Electrophoresis》2022,43(20):1944-1952
A simple, rapid method using CE and microchip electrophoresis with C4D has been developed for the separation of four nonsteroidal anti-inflammatory drugs (NSAIDs) in the environmental sample. The investigated compounds were ibuprofen (IB), ketoprofen (KET), acetylsalicylic acid (ASA), and diclofenac sodium (DIC). In the present study, we applied for the first time microchip electrophoresis with C4D detection to the separation and detection of ASA, IB, DIC, and KET in the wastewater matrix. Under optimum conditions, the four NSAIDs compounds could be well separated in less than 1 min in a BGE composed of 20 mM His/15 mM Tris, pH 8.6, 2 mM hydroxypropyl-beta-cyclodextrin, and 10% methanol (v/v) at a separation voltage of 1000–1200 V. The proposed method showed excellent repeatability, good sensitivity (LODs ranging between 0.156 and 0.6 mg/L), low cost, high sample throughputs, portable instrumentation for mobile deployment, and extremely lower reagent and sample consumption. The developed method was applied to the analysis of pharmaceuticals in wastewater samples with satisfactory recoveries ranging from 62.5% to 118%. 相似文献
218.
Hanan Alatawi Anna Hogan Ibtihaj Albalawi Emma O'Sullivan-Carroll Yineng Wang Eric Moore 《Electrophoresis》2022,43(7-8):857-864
Paracetamol (PAC) is one of the most extensively used analgesics and antipyretic drugs to treat mild and moderate pain. P-aminophenol (PAP), the main hydrolytic degradation product of PAC, can be found in environmental water. Recently, CE has been developed for the detection of a wide variety of chemical substances. The purpose of this study is to develop a simple and fast method for the detection and separation of PAC and its main hydrolysis product PAP using CE and microchip electrophoresis with capacitively coupled contactless conductivity detection. The determination of these compounds using microchip electrophoresis with capacitively coupled contactless conductivity detection is being reported for the first time. The separation was run for all analytes using a BGE (20 mM β-alanine, pH 11) containing 14% (v/v) methanol. The RSDs obtained for migration time were less than 4%, and RSDs obtained for peak area were less than 7%. The detection limits (S/N = 3) that were achieved ranged from 0.3 to 0.6 mg/L without sample preconcentration. The presented method showed rapid analysis time (less than 1 min), high efficiency and precision, low cost, and a significant decrease in the consumption of reagents. The microchip system has proved to be an excellent analytical technique for fast and reliable environmental applications. 相似文献
219.
Mariz R Poater A Gatti M Drinkel E Bürgi JJ Luan X Blumentritt S Linden A Cavallo L Dorta R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(48):14335-14347
A family of chiral C(2)-symmetric disulfoxide ligands possessing biaryl atropisomeric backbones has been synthesized by using the Andersen methodology. Complete characterization includes X-ray crystallographic studies of all ligands and some of their rhodium complexes. Their synthesis, optical purity, electronic properties, and catalytic behavior in the prototypical rhodium-catalyzed 1,4-addition of phenylboronic acid to 2-cyclohexen-1-one are presented through an in depth study of this ligand class. Density functional theory calculations on the step of the catalytic cycle that determines the enantioselectivity are presented and reinforce the first hypothetical explanations for the high levels of asymmetric induction observed. 相似文献
220.
János Kristóf Ray L. Frost Sara J. Palmer Erzsébet Horváth Emma Jakab 《Journal of Thermal Analysis and Calorimetry》2010,100(3):961-966
Dynamic and controlled rate thermal analysis (CRTA) has been used to characterise alunites of formula [M(Al)3(SO4)2(OH)6] where M+ is the cations K+, Na+ or NH4 +. Thermal decomposition occurs in a series of steps: (a) dehydration, (b) well-defined dehydroxylation and (c) desulphation. CRTA offers a better resolution and a more detailed interpretation of water formation processes via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. Constant-rate decomposition processes of water formation reveal the subtle nature of dehydration and dehydroxylation. 相似文献