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991.
Marta Ambrová Jana Jurišová Alexandra Sýkorová Dalibor Uher Vladimír Danielik Ján Híveš 《Chemical Papers》2008,62(2):154-159
The electrochemical behaviour of the LiF-La2O3 and LiF-CaF2-La2O3 systems was investigated by means of cyclic voltammetry. Several types of working electrodes (spectrographic pure graphite,
W, Mo, Ni, Cu) were used. It was found that chemical reactions take place in the system during the dissolution of lanthanum
oxide. The reduction of lithium cations occurred at the most positive potential from the species formed in the melt on ‘inert’
cathodes (W, Mo). The reactive cathodes (Cu, Ni) allowed the lanthanum deposition with depolarisation. 相似文献
992.
Harris RK Becker ED De Menezes SM Granger P Hoffman RE Zilm KW;International Union of Pure Applied Chemistry Physical Biophysical Chemistry Division 《Magnetic resonance in chemistry : MRC》2008,46(6):582-598
IUPAC has published a number of recommendations regarding the reporting of nuclear magnetic resonance (NMR) data, especially chemical shifts. The most recent publication [Pure Appl. Chem. 73, 1795 (2001)] recommended that tetramethylsilane (TMS) serve as a universal reference for reporting the shifts of all nuclides, but it deferred recommendations for several aspects of this subject. This document first examines the extent to which the (1)H shielding in TMS itself is subject to change by variation in temperature, concentration, and solvent. On the basis of recently published results, it has been established that the shielding of TMS in solution [along with that of sodium-3-(trimethylsilyl)propanesulfonate, DSS, often used as a reference for aqueous solutions] varies only slightly with temperature but is subject to solvent perturbations of a few tenths of a part per million (ppm). Recommendations are given for reporting chemical shifts under most routine experimental conditions and for quantifying effects of temperature and solvent variation, including the use of magnetic susceptibility corrections and of magic-angle spinning (MAS). This document provides the first IUPAC recommendations for referencing and reporting chemical shifts in solids, based on high-resolution MAS studies. Procedures are given for relating (13)C NMR chemical shifts in solids to the scales used for high-resolution studies in the liquid phase. The notation and terminology used for describing chemical shift and shielding tensors in solids are reviewed in some detail, and recommendations are given for best practice. 相似文献
993.
Maruyama T Yamamura H Hiraki M Kemori Y Takata H Goto M 《Colloids and surfaces. B, Biointerfaces》2008,66(1):119-124
We investigated DNA-directed aggregation of vesicles using DNA-surfactants. Following tethering of single-stranded DNA oligonucleotides to vesicles using DNA-surfactant, the tethered vesicles were assembled with other vesicles bearing complementary strands. The vesicle aggregation was strongly affected by the salt concentration and by temperature according to the characteristics of DNA hybridization. Restriction enzyme, which can hydrolyze the double-stranded DNA used in the present study, dissociated the vesicle aggregates. Exploration using fluorescently labeled vesicles suggested that the DNA-directed vesicle aggregation took place in a sequence-specific manner through DNA-duplex formation. Interestingly, the DNA-directed aggregation using short DNA-surfactant induced the fusion of vesicles to produce giant vesicles, resulting in an enzymatic reaction in the giant vesicle. 相似文献
994.
Membrane fusion between two lipid membranes with different curvatures was measured by using a fluorescence fusion assay for lipid vesicle systems and was also obtained by measuring lipid monolayer surface tension upon the fusion of vesicles to monolayer membranes. For such membrane systems, it was found that when lysolipid was incorporated only in the membrane with a greater curvature, membrane fusion was more suppressed than those for the case where the same amount (molar ratio of lysolipid to non-lysolipids) of lysolipid was incorporated only in the membrane with a lower curvature. When lysolipid was incorporated only in a flat membrane (e.g., monolayer) and the fusion of small vesicles (SUV) to the monolayer was measured, suppression of membrane fusion by lysolipid was minimal. It is known that lysolipid lowers the surface energy of curved membranes, which stabilizes energetically such membrane surfaces, and thus suppresses membrane fusion. Our results support our theory of lipid membrane fusion where the membrane fusion occurs through the most curved membrane region at the contact area of two interacting membranes. 相似文献
995.
Kashiwada A Matsuda K Mizuno T Tanaka T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(24):7343-7350
In many viruses, pH-responsive coiled-coil domains in the specific fusion proteins play important roles in membrane fusion and the infection of viruses into host cells. To investigate the relationship between the conformational change of the coiled coil and the fusion process, we have introduced a de novo designed polypeptide as a model system of the coiled-coil domain. This system enables the systematic study of the dynamics of pH-responsive coiled-coil polypeptide-membrane interactions. First, we designed and synthesized pH-responsive isoleucine-zipper triple-stranded coiled-coil polypeptides. Then the relationship between the pH-induced conformational change of the polypeptide and the membrane's interactive properties was studied by physicochemical methods. Structural changes in the designed polypeptides were examined by means of circular dichroism measurements. And finally, the behavior of the membrane fusion was investigated by leakage of liposomal contents, turbidity analysis, dynamic light scattering, and lipid mixing experiments. Our data show that coiled-coil formation under acidic pH conditions enhances polypeptide-induced membrane fusion. The results in this study demonstrate that an artificial membrane fusion system can be constructed on a molecular level by the use of a pH-responsive isoleucine-zipper triple-stranded coiled-coil polypeptide. 相似文献
996.
Takayoshi Ishimoto Masanori Tachikawa Umpei Nagashima 《International journal of quantum chemistry》2008,108(3):472-481
To optimize the exponent values in protonic and deuteronic Gaussian‐type functions (GTF) by the elimination of translational and rotational motions, we have proposed the new scheme of an analytical gradient formula with respect to the exponent values in the multi‐component molecular orbital scheme, which can take into account the quantum effects of protons and deuterons, under the Hartree‐Fock level of theory. Numerical assessment of H2 and D2 molecules confirms that there is a clear difference between distributions of protonic and deuteronic orbitals following the elimination of translational and rotational motions. In particular, the d‐type GTF in the protonic orbital drastically improves the total energy. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
997.
Dr. Tatsuhiro Murakami Kanon Ogino Yu Hashimoto Prof. Toshiyuki Takayanagi 《Chemphyschem》2023,24(10):e202200939
In the interstellar medium, the H2 adsorption and desorption on the solid water ice are crucial for chemical and physical processes. We have recently investigated the probabilities of H2 sticking on the (H2O)8 ice, which has quadrilateral surfaces. We have extended the previous work using classical MD and ring-polymer molecular dynamics (RPMD) simulations to the larger ice clusters, (H2O)10 and (H2O)12, which have pentagonal and hexagonal surfaces, respectively. The H2 sticking probabilities decreased as the temperature increased for both cluster cases, whereas the cluster-size-independent profiles were observed. It is thought that the size independence of the probabilities is qualitatively understood from the similar binding energies for all the three cluster systems. Furthermore, the RPMD sticking probabilities are smaller than the classical ones because of the reduction in the binding energies owing to nuclear quantum effects, such as vibrational quantization. 相似文献
998.
Junchen Zhu Kailong Yuan Yue Xie Huabing Liu Huiqing Jin Cuirong Sun Hongru Feng Qi Li Yuanjiang Pan 《Journal of separation science》2023,46(23):2300415
Sucrose esters (SEs) are crucial tobacco smoke flavor precursors and play a significant role in tobacco's functionality. Due to their structural complexity, the separation and analysis of SEs in tobacco remain a major challenge, and massive structures of SEs have not yet been fully identified. In this study, the fractions enriched in SEs were obtained from oriental and flue-cured tobacco through a series of pretreatments, and two types of SEs (Types I and II) were distinguished by liquid chromatography-tandem mass spectrometry (LC-MSn) analysis, with Type II SEs newly characterized in tobacco. Five groups of main SEs were further purified using preparative high-performance LC (HPLC) coupled to an evaporative light scattering detector, and their structures were characterized by nuclear magnetic resonance spectrometry techniques including 1H, 13C, correlation spectroscopy, heteronuclear single quantum correlation, and heteronuclear multiple bond correlation. By combining LC-MSn and nuclear magnetic resonance spectrometry, the structures of eight SE isomers were finally proposed, of which four were newly identified. These findings further enhance the understanding of the structural diversity of SEs in tobacco, serving as a valuable reference for future research on the elucidation, synthesis, and metabolism of SEs. 相似文献
999.
硼石膏近些年在水泥、沥青混合材料等领域应用广泛,其主要成分为CaSO4·2H2O和B2O3以及其他杂质,因此准确、快速测定石膏样品中的硼元素对石膏的应用、资源综合利用等方面具有重要意义。而国家标准GB/T 5484-2012《石膏分析方法》中并没有硼元素的化学分析方法,且相关文献报道也很少。目前测定硼元素主要采用电感耦合等离子体质谱法(ICP-MS),样品前处理多采用酸溶法,而碱熔法应用不多,主要原因是碱熔后溶液中产生大量盐分影响等离子体焰的稳定性,而732型阳离子交换树脂能吸附大量的钠离子,同时吸附了钙、镍、铁及稀土等阳离子,减少盐分干扰。基于此原理,本文采用氢氧化钠碱熔-732型阳离子交换树脂交换分离,在线加入铑内标的方式,建立了ICP-MS法测定石膏中硼的方法,同时由于石膏国家标准物质不包含硼元素的含量,采用高纯硫酸钙分别与岩石标准物质、水系沉积物国家标准物质和土壤国家标准物质混合配置成人工标准物质,并讨论了熔矿体系、阳离子加入量与吸附时间、清洗液、同位素的选择等实验条件。本方法的检出限为0.76μg/g,精密度(RSD,n=7)为0.9%~1.7%,相对误差为1.56%~3.96%,加标回收率在97.5%~102%,该方法快速、准确,记忆效应小,适合石膏中硼元素的测定。 相似文献
1000.
高晓菲 《曲阜师范大学学报》2014,(4):65-68
文章提出了建筑用电设备物联网与云计算平台融合应用的思路,通过这种途径,在降低硬件投入成本的前提下,很好地解决了大规模应用建筑用电设备物联网时,可能出现的节点错误、服务器瘫痪等现象.两者的融合应用必然具有广阔的前景. 相似文献