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11.
Calreticulin (CRT) is localized to and has functions in multiple cellular compartments, including the cell surface, the endoplasmic reticulum, and the extracellular matrix. Mutagenesis studies have identified several residues on a concave β-sheet surface of CRT critical for CRT binding to carbohydrate and other proteins/peptides. How the mutations of these key residues in CRT affect the conformation and dynamics of CRT, further influencing CRT binding to carbohydrates and other proteins to signal the important biological activities remain unknown. In this study, we investigated the effect of three key point mutations (C105A, C137A and W319A) on CRT conformation and dynamics via atomistic molecular dynamics simulations. Results show that these three key residues mutations induced the changes of CRT local backbone flexibility and secondary structure of CRT N-domain, which could further affect CRT’s binding activity. C137A mutation led to dramatic decrease of the overall size of CRT due to the P-domain fold back to the globular domain and formed new inter-domain contacts, which can cause blockage of CRT’s binding with other large substrates. Furthermore, for CRT concave β-strand surface patch containing lectin binding site, CRT C105A, C137A and W319A point mutation resulted in the changes in solvent accessible surface area, key residues’ side chain atom positions and dynamical correlated motions between residues. All these changes could directly affect CRT binding behavior. Results of this study provide molecular and structural insights into understanding the role of key residues of CRT in its binding behavior. 相似文献
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Alexander G. Sturm Tobias Santowski Julia I. Schweizer Dr. Lioba Meyer Dr. Kenrick M. Lewis Dr. Thorsten Felder Prof. Dr. Norbert Auner Prof. Dr. Max C. Holthausen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(36):8499-8502
The industrial production of monosilanes MenSiCl4−n (n=1–3) through the Müller–Rochow Direct Process generates disilanes MenSi2Cl6−n (n=2–6) as unwanted byproducts (“Direct Process Residue”, DPR) by the thousands of tons annually, large quantities of which are usually disposed of by incineration. Herein we report a surprisingly facile and highly effective protocol for conversion of the DPR: hydrogenation with complex metal hydrides followed by Si−Si bond cleavage with HCl/ether solutions gives (mostly bifunctional) monosilanes in excellent yields. Competing side reactions are efficiently suppressed by the appropriate choice of reaction conditions. 相似文献
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Dr. Wan-Shan Li Dr. Ren-Jie Yan Yi Yu Prof. Zhi Shi Dr. Attila Mándi Dr. Li Shen Prof. Tibor Kurtán Prof. Jun Wu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(31):13128-13136
Marine dinoflagellates produce remarkable organic molecules, particularly those with polyoxygenated long-carbon-chain backbones, namely super-carbon-chain compounds (SCCCs), characterized by the presence of numerous stereogenic carbon centers on acyclic polyol carbon chains. Even today, it is a challenge to determine the absolute configurations of these compounds. In this work, the planar structures and absolute configurations of two highly flexible SCCCs, featuring either a C69- or C71-linear carbon backbone, gibbosols A and B, respectively, each containing thirty-seven stereogenic carbon centers, were unambiguously established by a combined chemical, spectroscopic, and computational approach. The discovery of gibbosols A and B with two hydrophilic acyclic polyol chains represents an unprecedented class of SCCCs. A reasonable convergent strategy for the biosynthesis of these SCCCs was proposed. 相似文献
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The chalcogenido indates K6In2Q6 (Q = S, Se, Te) were synthesized from melts of the pure elements at a maximum temperature of 700 °C. All three potassium salts contain dinuclear units [In2Q6]6– of two edge-sharing [InQ4] tetrahedra. The sulfido and the selenido indate are isotypic and crystallize in the K6Mn2O6-type structure [monoclinic, space group P21/c, a = 784.32(9)/809.32(3), b = 1274.58(14)/1322.37(4), c = 836.48(9)/870.53(3) pm, β = 97.900(2)/97.5877(8)°, Z = 2, R1 = 0.0123/0.0109; for Q = S/Se]. The tellurido indate K6In2Te6 crystallizes in a new orthorhombic structure type [space group Pnma, a = 1793.70(12), b = 1491.55(11), c = 837.40(6) pm, Z = 4, R1 = 0.0157]. In this structure, the telluride anions form a hexagonal close packing, in which K+ cations occupy all octahedral voids; the In3+ ions take 1/6 (but always adjacent) tetrahedral voids. This structure-chemical relation to the h.c.p. packing, which is similarly found for most of the sodium dimetallates (e.g. Na6Fe2S6), is substantiated by a full crystallographic group-subgroup tree. The crystal chemistry of the new indates is discussed and compared with that of alkali chalcogenido metallates(III) of Fe, Al and Ga containing [M2Q6]6– dimers, which overall form as many as ten different structure types. DFT band structure calculations of the three title compounds exhibit bandgaps, which continuously decrease from the S to the Te compound and which are also in accordance with the pale yellow (S), bright yellow (Se) and red-brown (Te) color of the compounds. The chemical bonding in the salts and within the metallate anion is discussed on the basis of the partial DOS and a Bader analysis of the calculated electron density. 相似文献
16.
Xiaoshuang Luo Xinxian Qin Zhengyi Liu Dan Chen Weiwei Yu Kankan Zhang Deyu Hu 《Biomedical chromatography : BMC》2020,34(1):e4694
A simple and rapid analytical method for the detection of trifloxystrobin, trifloxystrobin acid and tebuconazole in soil, brown rice, paddy plants and rice hulls was established and validated by liquid chromatography with tandem mass spectrometry. Acceptable linearity (R2 > 0.99), accuracy (average recoveries of 74.3–108.5%) and precision (intra- and inter-day relative standard deviations of 0.9–8.8%) were obtained using the developed determination approach. In the field trial, the half-lives of trifloxystrobin and tebuconazole in paddy plants were 5.7–8.3 days in three locations throughout China, and the terminal residue concentrations of trifloxystrobin and tebuconazole were <100 and 500 μg/kg (maximum residue limits set by China), respectively, at harvest, which indicated that, based on the recommended application procedure, trifloxystrobin and tebuconazole are safe for use on rice. The risk assessment results demonstrated that, owing to risk quotient values of both fungicides being <100%, the potential risk of trifloxystrobin and tebuconazole on rice was acceptable for Chinese consumers. These data could provide supporting information for the proper use and safety evaluation of trifloxystrobin and tebuconazole in rice. 相似文献
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In developing countries, subsistence gold mining entails mixing metallic mercury with crushed sediments to extract gold. In this approach, the gold−mercury amalgam is heated to evaporate mercury and obtain gold. Thus, the highly volatile mercury can be absorbed through inhalation, resulting in adverse health effects. Urinalysis can be used to detect mercury, which is excreted in urine and feces, and correlate exposure with toxic effects. The current gold standard analytical methods are based on fluorescence or inductively coupled plasma mass spectrometry methods, but are expensive, time consuming, and are not easily accessible in countries where testing is needed. In this work, we report on a miniature electrochemical sensor that can rapidly detect mercury in urine at levels well below the US Biological Exposure Index (BEI) limit of 50 ppb (μg/L). The sensor is based on a thin-film gold electrode and anodic stripping voltammetry electroanalytical approach. The sensor successfully detected mercury at trace levels in urine, with a limit of detection of ∼15 ppb Hg in the linear range of 20–80 ppb. With the low-cost disposable sensors and portable instrumentation, it is well suited for point-of-care applications. 相似文献
20.
采用纳米Fe3O4粒子(nano-Fe3O4)和石墨烯(Reduced Graphene Oxide,RGO)制备了nano-Fe3O4-RGO复合材料修饰玻碳电极(nano-Fe3O4-RGO/GCE),采用循环伏安法(cyclic voltammetry,CV),方波伏安法(square wave voltammetry,SWV),计时电流法(chronoamperometry,CA),计时库仑法(chronocoulometry,CC)研究了吡罗昔康(Piroxicam,PC)在此复合修饰电极上的电化学行为及电化学动力学性质。实验结果表明,与GCE相比,nano-Fe3O4-RGO/GCE对PC的电化学氧化作用有显著的促进作用,其氧化峰电流显著增加;对各种实验条件进行了优化,测得峰电流Ipa与PC浓度在2.0×10-6~2.0×10-4mol·L-1范围内呈良好的线性关系,检出限(S/N=3)为5.3×10-7mol·L-1,加标回收率为100.0%~104.0%。该方法快速,灵敏,并将nano-Fe3O4-RGO/GCE用于市售吡罗昔康片剂的测定,结果符合定量测定要求。 相似文献