Thermochromic dynamic cool materials present a reversible change of their properties wherein by increasing the temperature, the reflectance, conductivity, and transmittance change due to a reversible crystalline phase transition. In particular, vanadium (IV) dioxide shows a reversible phase transition, accompanied by a change in optical properties, from monoclinic VO2(M1) to tetragonal VO2(R). In this paper, we report on a systematic exploration of the parameters for the synthesis of vanadium dioxide VO2(M1) via an easy, sustainable, reproducible, fast, scalable, and low-cost hydrothermal route without hazardous chemicals, followed by an annealing treatment. The metastable phase VO2(B), obtained via a hydrothermal route, was converted into the stable VO2(M1), which shows a metal–insulator transition (MIT) at 68 °C that is useful for different applications, from energy-efficient smart windows to dynamic concrete. Within this scenario, a further functionalization of the oxide nanostructures with tetraethyl orthosilicate (TEOS), characterized by an extreme alkaline environment, was carried out to ensure compatibility with the concrete matrix. Structural properties of the synthesized vanadium dioxides were investigated using temperature-dependent X-ray Diffraction analysis (XRD), while compositional and morphological properties were assessed using Scanning Electron Microscopy, Energy Dispersive X-ray Analysis (SEM-EDX), and Transmission Electron Microscopy (TEM). Differential Scanning Calorimetry (DSC) analysis was used to investigate the thermal behavior. 相似文献
Allenylamides of Boc-protected α-aminoacids easily gave in basic medium heterocyclic products arising from attack of the NH group on the inside C-C double bond of the 1,2-diene moiety, namely imidazolidinones, pyrazinones, and a pyrrole compound. The microwave-assisted heterocyclization occurred cleanly at C-β of the allenyl group with formation of pyrazin-2-ones having an endo- or exocyclic double bond. 相似文献
The interest on phenothiazine drugs has been increased during last years due to their proved utility in the treatment of several diseases and biomolecular processes. In the present work, the binding of the amphiphilic phenothiazines promazine and thioridazine hydrochlorides to the carrier protein human serum albumin (HSA) has been examined by ζ-potential, isothermal titration calorimetry (ITC), fluorescence and circular dichorism (CD) spectroscopies, and dynamic light scattering (DLS) at physiological pH with the aim of analyzing the role of the different interactions in the drug complexation process with this protein. The ζ-potential results were used to check the existence of complexation. This is confirmed by a progressive screening of the protein charge up to a reversal point as a consequence of drug binding. On the other hand, binding causes alterations on the tertiary and secondary structures of the protein, which were observed by fluorescence and CD spectroscopies, involving a two-step, three-state transition. The thermodynamics of the binding process was derived from ITC results. The binding enthalpies were negative, which reveal the existence of electrostatic interactions between protein and drug molecules. In addition, increases in entropy are consistent with the predominance of hydrophobic interactions. Two different classes of binding sites were detected, viz. Binding to the first class of binding sites is dominated by an enthalpic contribution due to electrostatic interactions whereas binding to a second class of binding sites is dominated by hydrophobic bonding. In the light of these results, protein conformational change resembles the acid-induced denaturation of HSA with accumulation of an intermediate state. Binding isotherms were derived from microcalorimetric results by using a theoretical model based on the Langmuir isotherm. On the other hand, the population distribution of the different species in solution and their sizes were determined through dynamic light scattering (DLS). Aggregation of drug/protein complexes was found as a result of a possible expansion of protein structure induced at high drug concentrations. In addition, the presence of free drug aggregates at concentrations below the drug critical micelle concentration was also detected. 相似文献
A simple and rapid development of a stability-indicating LC method for determination of chloroquine diphosphate in the presence of its hydrolysis, oxidative and photolysis degradation products is described. Stress testing showed that chloroquine diphosphate was degraded under basic conditions and by photolytic treatment but was stable under the other stress conditions investigated. Separation of the drug from its degradation products was achieved with a Nova Pack C18 column, 0.01 M PIC B7 and acetonitrile (40:60 v/v) pH 3.6, as mobile phase. Response was linear over the range 0.08–5.70 μg mL−1 (r = 0.996), with limits of detection and quantification (LOD and LOQ) of 0.17 and 0.35 μg mL−1, respectively.
The 3051 USEPA method (or alternatively, the 3051A) can be considered nowadays as a reference method to extract metals from sediments. However, after microwave heating, the sample must be allowed to cool down, which results in a considerable lengthening of the whole analytical process. Microwave ovens and their maintenance are, in addition, expensive, and its use is relatively dangerous. The use of ultrasound focused energy to assist the extraction of chemicals from solid samples is a safe and relatively cheap technique. In this work we propose a new method to extract simultaneously several elements from sediments using ultrasound energy focused in a glass probe to accelerate the process, and check its possibilities to become an alternative to the EPA3051(A) approach. The optimised procedure allows extracting 13 elements in only 6 min, with similar recoveries and, in general, better repetitivities than the EPA3051. In addition, the suspension is only slightly heated during the leaching process. 相似文献
A combined strategy based on the development of pharmacophore hypotheses and NMR approaches is reported for the identification
of novel inhibitors of heparanase, a key enzyme involved in tumor metastasis through the remodeling of the subepithelial and
subendothelial basement membranes, resulting in the dissemination of metastatic cancer cells. Several pharmacophore hypotheses
were initially developed from the most active heparanase inhibitors known to date and, after their application to a pool of
27 known heparanase inhibitors and a database of 1,120 compounds approved by the FDA, a four-point pharmacophore model was
selected as the most predictive. This model was subsequently applied to a database of 686 chemical fragments, and a subset
of 100 fragments accomplishing completely or partially the four-point model was selected to perform nuclear magnetic resonance
experiments to validate the hypothesis. The experimental studies confirmed the reliability of our pharmacophore model, its
applicability to in silico databases in order to reduce the number of compounds to be experimentally screened, and the possibility
of generating fragment libraries enriched in heparanase inhibitors.
Rafael Gozalbes and Silvia Mosulén contributed equally to this work. 相似文献
The sol–gel reactions of the two methacrylate-modified silanes methacryloxymethyltriethoxysilane (MAMTES) and methacryloxypropyltrimethoxysilane
(MAPTMS) were followed by using two independent time-resolved spectroscopic methods, viz., IR ATR and NMR with the aim to
optimise their pre-hydrolysis times and consequently their use as precursors for hybrid materials. Time resolved measurements
were carried out on the two systems under sol–gel conditions. Whereas the hydrolysis of both siloxanes is very fast, condensation
proceeds gradually and is not completely finished within 5 h. 相似文献
Stem cells or immune cells targeting the central nervous system (CNS) bear significant promises for patients affected by CNS
disorders. Brain or spinal cord delivery of therapeutic cells is limited by the blood-brain barrier (BBB) which remains one
of the recognized rate-limiting steps. Osmotic BBB disruption (BBBD) has been shown to improve small molecule chemotherapy
for brain tumors, but successful delivery of cells in conjunction with BBBD has never been reported. 相似文献
In pregnancy complicated by gestational diabetes mellitus (GDM), the human placenta shows several pathological functional and structural changes, but the extent to which maternal glycemic control contributes to placental abnormalities remains unclear. The aim of this study was to profile and compare the proteome of placentas from healthy pregnant women and those with GDM, to investigate the placenta‐specific protein composition and possible changes of its function in presence of GDM. Quantitative proteomic analysis, based on LC‐MSE approach, revealed that higher (approximately 15% increase) levels of galectin 1 and collagen alpha‐1 XIV chain (although the difference regarding the latter was at the limit of significance) were present in GDM samples, while heat shock 70 kDa protein 1A/1B was less abundant in GDM placental tissue. These data seem to indicate that GDM, when well controlled, did not markedly affect the placental proteome. 相似文献
A simple and highly sensitive CE–UV method was applied in the determination of l ‐ctrulline, which was developed from an oral formulation for pediatric use. The novel method was based on the analysis of l ‐citrulline for direct ultraviolet detection at 198 nm. The BGE consisted of 10 mM sodium tetraborate and 50 mM SDS at pH 9, and the electrophoretic parameters were optimized. The method was validated in terms of specificity, linearity, LOD, LOQ, precision, accuracy, and robustness. The LOD and LOQ obtained were 1.36 and 4.54 μg/mL, respectively. In addition, the method offers higher sensitivity and specificity compared with the results obtained from HPLC method using UV‐detectors, in which l‐ citrulline needs to be derivatizated. Furthermore, low cost and simplicity of the system allowed the rapid and simple quantitation of l‐ citrulline in the oral formulation for quality control and stability indicated method. 相似文献