reaction mechanism

反应机理
  • 文章类型: Journal Article
    凝血酶原酶复合物,由凝血因子Xa(FXa)和Va(FVa)组成,是血液凝固网络的主要酶,通过激活磷脂膜表面上的非活性前体凝血酶原(FII)来产生凝血酶。然而,凝血酶原酶形成和底物传递的途径和机制仍在讨论中。在这里,我们设计了一种新颖的数学模型,该模型考虑了FXa或FII结合(来自膜或来自溶液)的不同潜在途径,并分析了在各种反应物浓度存在下凝血酶形成的动力学。我们观察到大FVa浓度的抑制作用,这种作用是磷脂浓度依赖性的。我们预测,有效的FII激活是通过形成三元复合物而发生的,其中FVa,FXa和FII处于膜结合状态。凝血酶原递送主要是膜依赖性的,但是在磷脂缺乏或FXa/FVa过量的情况下,从溶液中递送是主要的。同样,在FVa过量的情况下,FXa从溶液中递送是主要的,但高FII没有将FXa交付切换到解决方案依赖的交付。此外,FXa递送途径不依赖于磷脂浓度,即使在磷脂缺乏的情况下也是膜依赖性的。这些结果表明凝血酶原酶功能的灵活机制,该机制根据条件利用不同的复合物形成甚至抑制机制。
    Prothrombinase complex, composed of coagulation factors Xa (FXa) and Va (FVa) is a major enzyme of the blood coagulation network that produces thrombin via activation of its inactive precursor prothrombin (FII) on the surface of phospholipid membranes. However, pathways and mechanisms of prothrombinase formation and substrate delivery are still discussed. Here we designed a novel mathematical model that considered different potential pathways of FXa or FII binding (from the membrane or from solution) and analyzed the kinetics of thrombin formation in the presence of a wide range of reactants concentrations. We observed the inhibitory effect of large FVa concentrations and this effect was phospholipid concentration-dependent. We predicted that efficient FII activation occurred via formation of the ternary complex, in which FVa, FXa and FII were in the membrane-bound state. Prothrombin delivery was mostly membrane-dependent, but delivery from solution was predominant under conditions of phospholipid deficiency or FXa/FVa excess. Likewise, FXa delivery from solution was predominant in the case of FVa excess, but high FII did not switch the FXa delivery to the solution-dependent one. Additionally, the FXa delivery pathway did not depend on the phospholipid concentration, being the membrane-dependent one even in case of the phospholipid deficiency. These results suggest a flexible mechanism of prothrombinase functioning which utilizes different complex formation and even inhibitory mechanisms depending on conditions.
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  • 文章类型: Journal Article
    水性锌离子电池(AZIBs)由于其高安全性,为大规模储能提供了巨大的潜力,低成本和可接受的能量密度。然而,AZIBs的循环寿命不可避免地受到电极等多种因素引起的寄生反应和枝晶生长的影响,电解质和隔膜,这对AZIB的实际应用构成了重大障碍。为了应对这些挑战,导电聚合物(CP)基材料由于其可调节的带隙而在充电电池领域得到了广泛的关注,可控形态,以及CP的出色灵活性。特别是,CP表现出显著的导电性,低维,和掺杂特性,使它们非常有希望集成到AZIB系统。在这次审查中,与阴极相关的问题,阳极,电解质,讨论了AZIB的分离器,并总结了CP在其改性中的应用。该综述对CP改性过程中涉及的作用机制进行了全面分析,并为可在AZIB中有效利用的CP的设计和开发提供了宝贵的见解。此外,这篇综述对这一研究领域提出了有希望的展望,旨在进一步推进低成本高性能CPs及其复合材料在AZIB中的应用。
    Aqueous zinc ion batteries (AZIBs) offer great potential for large-scale energy storage because of their high safety, low cost and acceptable energy density. However, the cycle life of AZIBs is inevitably affected by parasitic reactions and dendritic growth caused by multiple factors such as electrode, electrolyte and separator, which pose significant obstacles to the practical application of AZIBs. To address these challenges, conducting polymer (CP) based materials have gained widespread attention in the realm of rechargeable batteries due to the adjustable band gap, controllable morphology, and excellent flexibility of CPs. In particular, CPs exhibit remarkable conductivity, low dimensionality, and doping characteristics, making them highly promising for integration into the AZIB system. In this review, the problems associated with the cathode, anode, electrolyte, and separator of AZIBs are discussed, and the application of CPs for their modification is summarized. The review provides a comprehensive analysis of the action mechanisms involved in the CP modification process and offers valuable insights for the design and development of CPs that can be effectively utilized in AZIBs. Additionally, the review presents a promising outlook of this research field, aiming to further advance the application of low-cost and high-performance CPs and their composites in AZIBs.
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  • 文章类型: Journal Article
    在这项工作中,我们提出了一个多层次的协议,用于化学反应机理的常规理论研究。我们研究的系统的初始反应路径是使用廉价的电子结构方法驱动的微动弹性带(NEB)方法采样的。用机器学习技术(在我们的例子中,对称梯度域机器学习或sGDML)以更精确的电子结构理论为路径上的一组点重新计算的力,以产生半局部无功势能面(PES),拥抱反应物,产品和过渡状态(TS)区域。该方法已成功应用于单分子(烯二炔的Bergman环化)和双分子(SN2取代)反应。特别是,我们证明,只有50到150个能量力评估与精确的参考方法(这里是完全活动空间自洽场,CASCF,和耦合集群单打和双打,CCSD)可以构造半局部PES,从而为固定点几何形状提供定性协议,内在反应坐标和障碍。此外,我们发现振动频率和反应速率系数在质量上是一致的。该方法性能的关键方面是其多层次的性质,这不仅节省了计算量,而且允许沿着反应路径提取有意义的信息,除一个方向外,所有方向的梯度为零。对TS的性质和计算经济不了解,该方案可以很容易地自动化,并常规用于机械反应研究。
    In this work, we propose a multi-level protocol for routine theoretical studies of chemical reaction mechanisms. The initial reaction paths of our investigated systems are sampled using the Nudged Elastic Band (NEB) method driven by a cheap electronic structure method. Forces recalculated at the more accurate electronic structure theory for a set of points on the path are fitted with a machine learning technique (in our case symmetric gradient domain machine learning or sGDML) to produce a semi-local reactive potential energy surface (PES), embracing reactants, products and transition state (TS) regions. This approach has been successfully applied to a unimolecular (Bergman cyclization of enediyne) and a bimolecular (SN2 substitution) reaction. In particular, we demonstrate that with only 50 to 150 energy-force evaluations with the accurate reference methods (here complete-active-space self-consistent field, CASSCF, and coupled-cluster singles and doubles, CCSD) it is possible to construct a semi-local PES giving qualitative agreement for stationary-point geometries, intrinsic reaction coordinates and barriers. Furthermore, we find a qualitative agreement in vibrational frequencies and reaction rate coefficients. The key aspect of the method\'s performance is its multi-level nature, which not only saves computational effort but also allows extracting meaningful information along the reaction path, characterized by zero gradients in all but one direction. Agnostic to the nature of the TS and computationally economic, the protocol can be readily automated and routinely used for mechanistic reaction studies.
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  • 文章类型: Journal Article
    开发具有高效氧活化能力的稳健金属基整体式催化剂对于挥发性有机化合物(VOC)污染的热催化处理至关重要。二维(2D)金属氧化物是替代的热催化剂,但是他们在载体上的传统装载策略在实际应用中仍然面临挑战。在这里,我们提出了一种新型的原位熔盐加载策略,该策略首次同步实现了2DCo3O4的构建及其在Fe泡沫上的生长,从而产生了一种名为Co3O4/Fe-S的独特整体催化剂。与负载Co3O4纳米立方体的Fe泡沫相比,Co3O4/Fe-S表现出显着改善的催化性能,在90%的甲苯转化率下温度降低了44°C。像差校正的扫描透射电子显微镜和理论计算表明,Co3O4/Fe-S具有丰富的2DCo3O4/Fe3O4复合界面,这促进了活性部位(氧空位和Co3+)的构建,以促进氧活化和甲苯化学吸附,从而通过Langmuir-Hinshelwood(L-H)和Mars-vanKrevelen(MvK)机制加速反应中间体的转化。此外,生长机理揭示了2DCo3O4/Fe3O4复合界面在熔盐中原位生成,诱导2DCo3O4生长到2DFe3O4的表面晶格上。这项研究为增强氧活化提供了新的见解,并为制备用于VOC氧化的有效整体催化剂开辟了前所未有的途径。
    Developing robust metal-based monolithic catalysts with efficient oxygen activation capacity is crucial for thermal catalytic treatment of volatile organic compound (VOC) pollution. Two-dimensional (2D) metal oxides are alternative thermal catalysts, but their traditional loading strategies on carriers still face challenges in practical applications. Herein, we propose a novel in situ molten salt-loading strategy that synchronously enables the construction of 2D Co3O4 and its growth on Fe foam for the first time to yield a unique monolithic catalyst named Co3O4/Fe-S. Compared to the Co3O4 nanocube-loaded Fe foam, Co3O4/Fe-S exhibits a significantly improved catalytic performance with a temperature reduction of 44 °C at 90% toluene conversion. Aberration-corrected scanning transmission electron microscopy and theoretical calculation suggest that Co3O4/Fe-S possesses abundant 2D Co3O4/Fe3O4 composite interfaces, which promote the construction of active sites (oxygen vacancy and Co3+) to boost oxygen activation and toluene chemisorption, thereby accelerating the transformation of reaction intermediates through Langmuir-Hinshelwood (L-H) and Mars-van Krevelen (MvK) mechanisms. Moreover, the growth mechanism reveals that 2D Co3O4/Fe3O4 composite interfaces are generated in situ in molten salt, inducing the growth of 2D Co3O4 onto the surface lattice of 2D Fe3O4. This study provides new insights into enhancing oxygen activation and opens an unprecedented avenue in preparing efficient monolithic catalysts for VOC oxidation.
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  • 文章类型: Journal Article
    制造批量高效,用户友好和环保,和明确定义的合成氧化石墨的产率方法,氧化石墨烯及其还原衍生物的主要前体,是一个重要而强大的研究领域,然而,近年来却很少进行调查或创新。这篇概念综述展示了满足上述设计参数的电化学装置制造的最新进展,其中工作电极结构被认为在塑造产量特性和帮助对所采用方法的效率的机械理解中起着关键作用。特别是,这些进步为新的和各种可调的设计参数铺平了道路,通过制造不同的方法封装石墨粉,而不是使用传统的裸整体形式的石墨作为工作电极。封装几何结构,压力,和基质材料,以及粉末尺寸是这种可调设计参数的例子,在整体方法中不存在。封装验证了电化学插层实时监测的真实性,剥脱,和石墨粉的氧化,从而提供优异的和明确的产量控制。
    Fabrication of batch-wise efficient, user- and environmentally-friendly, and well-defined yield methods for the synthesis of graphite oxide, the main precursor to graphene oxide and its reduced derivative, is an essential and robust research field, yet is sparingly investigated or innovated in recent years. This Concept review showcases recent advances in the fabrication of electrochemical set ups that meet aforementioned design parameters, wherein working electrode construction is seen to play a key role in shaping the yield characteristics and aiding the mechanistic understanding of efficiency of adopted methods. Particularly, these advances pave the way for new and various tunable design parameters by fabricating different methods of encapsulating graphite powder instead of using conventional bare monolith forms of graphite as working electrode. Encapsulation geometry, pressure, and matrix material, as well as powder size are examples of such tunable design parameters, absent in the monolith methods. The encapsulation validates authenticity of real-time monitoring of electrochemical intercalation, exfoliation, and oxidation of graphite powder, thereby offering excellent and well-defined control on yield.
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  • 文章类型: Journal Article
    硫循环的化学性质大大有助于大气成核过程,这是新粒子形成(NPF)的第一步。在本研究中,通过理论计算和大气集群动态代码模拟,全面研究了三氧化硫(SO3)与硫化氢(H2S)的环加成反应机理,硫化氢是一种典型的空气污染物和对环境有害的有毒气体。进一步分析了产物硫代硫酸(H2S2O3,TSA)的气相稳定性和成核潜力,以评估其对大气的影响。没有任何催化剂,H2S+SO3反应在24.2kcal/mol的势垒下是不可行的。大气成核前体甲酸(FA),硫酸(SA),和水(H2O)可以有效地降低反应壁垒作为催化剂,甚至可以进行无阻碍的反应,其效率为顺式SA>反式FA>反式SA>H2O。随后,研究了TSA的气相稳定性。在SA的催化作用下,单独的水解反应屏障高达61.4kcal/mol,吸热异构化反应屏障为5.1kcal/mol,证明了TSA的足够稳定性。此外,进行拓扑和动力学分析以确定TSA的成核潜力。由TSA和大气成核前体形成的大气团簇(SA,氨NH3和二甲胺DMA)是热力学稳定的。此外,TSA基簇的蒸发系数逐渐减小,特别是对于TSA-DMA,表明TSA可能参与基础分子浓度相对较高的NPF。目前的新反应机理可能有助于更好地理解大气硫循环和NPF。
    The chemistry of sulfur cycle contributes significantly to the atmospheric nucleation process, which is the first step of new particle formation (NPF). In the present study, cycloaddition reaction mechanism of sulfur trioxide (SO3) to hydrogen sulfide (H2S) which is a typical air pollutant and toxic gas detrimental to the environment were comprehensively investigate through theoretical calculations and Atmospheric Cluster Dynamic Code simulations. Gas-phase stability and nucleation potential of the product thiosulfuric acid (H2S2O3, TSA) were further analyzed to evaluate its atmospheric impact. Without any catalysts, the H2S + SO3 reaction is infeasible with a barrier of 24.2 kcal/mol. Atmospheric nucleation precursors formic acid (FA), sulfuric acid (SA), and water (H2O) could effectively lower the reaction barriers as catalysts, even to a barrierless reaction with the efficiency of cis-SA > trans-FA > trans-SA > H2O. Subsequently, the gas-phase stability of TSA was investigated. A hydrolysis reaction barrier of up to 61.4 kcal/mol alone with an endothermic isomerization reaction barrier of 5.1 kcal/mol under the catalytic effect of SA demonstrates the sufficient stability of TSA. Furthermore, topological and kinetic analysis were conducted to determine the nucleation potential of TSA. Atmospheric clusters formed by TSA and atmospheric nucleation precursors (SA, ammonia NH3, and dimethylamine DMA) were thermodynamically stable. Moreover, the gradually decreasing evaporation coefficients for TSA-base clusters, particularly for TSA-DMA, suggests that TSA may participate in NPF where the concentration of base molecules are relatively higher. The present new reaction mechanism may contributes to a better understanding of atmospheric sulfur cycle and NPF.
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  • 文章类型: Journal Article
    电化学反应非常复杂,涉及多种物理化学过程。对反应过程中的中间过程变化进行准确和系统的监测对于理解电化学反应的机理至关重要,并且是合理设计新电化学反应的基础。基于质谱(MS)的在线电化学分析已成为研究电化学反应的重要工具。该技术基于不同的电离和采样手段,通过建立电化学-MS(EC-MS)耦合装置,实现了电化学反应的在线分析。特别是,它通过捕获和识别反应中间体为阐明反应机理提供了关键证据。这篇综述将对各种EC-MS设备及其研究的有机电化学反应系统进行分类,近年来的最新研究进展。它还将分析各种设备的性能,并展望EC-MS的未来发展。
    Electrochemical reactions are very complex and involve a variety of physicochemical processes. Accurate and systematic monitoring of intermediate process changes during the reaction is essential for understanding the mechanism of electrochemical reactions and is the basis for rational design of new electrochemical reactions. On-line electrochemical analysis based on mass spectrometry (MS) has become an important tool for studying electrochemical reactions. This technique is based on different ionization and sampling means and realizes on-line analysis of electrochemical reactions by establishing electrochemistry-MS (EC-MS) coupling devices. In particular, it provides key evidence for elucidating the reaction mechanism by capturing and identifying the reactive reaction intermediates. This review will categorize various EC-MS devices and the organic electrochemical reaction systems they study, highlighting the latest research progress in recent years. It will also analyze the properties of various devices and look forward to the future development of EC-MS.
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  • 文章类型: Journal Article
    将魔芋的甲醇提取物过乙酰化,以获得不寻常的过乙酰化γ-内酯主链。结构阐明表明,该化合物是庚酸γ-内酯化学转化的结果。
    The methanolic extract of Amorphophallus paeoniifolius was peracetylated to obtain an unusual peracetylated γ-lactone backbone. Structure elucidation revealed that this compound is an outcome of the chemical transformation of heptonic acid γ-lactone.
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  • 文章类型: Journal Article
    VOCs可以代替氨作为还原剂去除NO,同时达到去除VOCs和NO的效果。由于常规热催化净化所需的高能耗和低光催化效率,光热耦合催化净化可以综合光催化和热催化的优点,以达到低能耗高效处理污染物的效果。在这项研究中,采用水热法在各种形貌的Fe-MOF上制备了负载Co和Mn催化剂的样品。通过各种表征研究其理化性质的影响,分析了各催化剂的催化性能,包括XRD,SEM,BET,XPS,H2-TPR,TEM和O2-TPD。表征结果表明,孔隙体积,高价Co和Mn原子,催化剂表面吸附氧和氧晶格缺陷的丰度是影响催化剂性能的最关键因素。根据性能测试的结果,负载Co和Mn的八面体形Fe-MOF制备的催化剂比负载Co和Mn的棒状Fe-MOF具有更好的性能。丙酮和NO的转化率分别达到50%和64%,分别,240°C结果表明,该催化剂能够同时去除丙酮和NO。与不含Co和Mn的纯Fe-MOF相比,在多种因素的综合作用下,负载型催化剂同时去除丙酮和NO的能力明显更高。根据Mars-vanKrevelen(MvK)机理,研究了丙酮和NO在催化剂表面催化转化的关键反应步骤,并提出了一种可能的机制。这项研究提出了一种通过光热耦合同时去除丙酮和NOx的新思路。
    VOCs can be used instead of ammonia as a reducing agent to remove NO, achieving the effect of removing VOCs and NO simultaneously. Due to the high energy consumption and low photocatalytic efficiency required for conventional thermocatalytic purification, photothermal coupled catalytic purification can integrate the advantages of photocatalysis and thermocatalysis in order to achieve the effect of pollutants being treated efficiently with a low energy consumption. In this study, samples loaded with Co and Mn catalysts were prepared using the hydrothermal method on Fe-MOF with various morphologies. The catalytic performance of each catalyst was analyzed by studying the effects of their physicochemical properties through various characterizations, including XRD, SEM, BET, XPS, H2-TPR, TEM and O2-TPD. The characterization results demonstrated that the specific surface area, pore volume, high valence Co and Mn atoms, surface adsorbed oxygen and the abundance of oxygen lattice defects in the catalysts were the most critical factors affecting the performance of the catalysts. Based on the results of the performance tests, the catalysts prepared with an octahedral-shaped Fe-MOF loaded with Co and Mn showed a better performance than those loaded with Co and Mn on a rod-shaped Fe-MOF. The conversions of acetone and NO reached 50% and 64%, respectively, at 240 °C. The results showed that the catalysts were capable of removing acetone and NO at the same time. Compared with the pure Fe-MOF without Co and Mn, the loaded catalysts showed a significantly higher ability to remove acetone and NO simultaneously under the combination of various factors. The key reaction steps for the catalytic conversion of acetone and NO on the catalyst surface were investigated according to the Mars-van Krevelen (MvK) mechanism, and a possible mechanism was proposed. This study presents a new idea for the simultaneous removal of acetone and NOx by photothermal coupling.
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  • 文章类型: Journal Article
    生物过滤是一种污染管理方法,它利用含有活性物质的生物反应器来生物吸收和破坏污染物。在本文中,我们研究了混合挥发性有机化合物(VOCs)的生物过滤的数学模型,例如亲水性(甲醇)和疏水性(α-pine烯)。非线性扩散方程组描述了酶化学反应的Michaelis-Menten动力学。这些模型代表气相中的化学氧化和空气-生物膜连接处内的质量传递。此外,为了对α-pine烯和甲醇在生物膜和气体状态下的饱和度进行数值研究,我们开发了一种基于Elman神经网络(ENN)架构的高效监督机器学习算法。此外,Levenberg-Marquardt(LM)优化范例用于查找ENN架构中涉及的参数/神经元。在不同物理参数的变化下,通过ENN-LM技术找到的甲醇饱和度和α-pine烯的解决方案的近似值通过最先进的技术计算得出的数值结果来说明。相对于绝对误差术语的性能指示的图形和统计说明,平均绝对偏差,计算复杂性,和均方误差验证了我们的结果完美地描述了现实生活中的情况,并可进一步用于化学工程中出现的问题。
    Biofiltration is a method of pollution management that utilizes a bioreactor containing live material to absorb and destroy pollutants biologically. In this paper, we investigate mathematical models of biofiltration for mixing volatile organic compounds (VOCs) for instance hydrophilic (methanol) and hydrophobic ( α -pinene). The system of nonlinear diffusion equations describes the Michaelis-Menten kinetics of the enzymic chemical reaction. These models represent the chemical oxidation in the gas phase and mass transmission within the air-biofilm junction. Furthermore, for the numerical study of the saturation of α -pinene and methanol in the biofilm and gas state, we have developed an efficient supervised machine learning algorithm based on the architecture of Elman neural networks (ENN). Moreover, the Levenberg-Marquardt (LM) optimization paradigm is used to find the parameters/ neurons involved in the ENN architecture. The approximation to a solutions found by the ENN-LM technique for methanol saturation and α -pinene under variations in different physical parameters are allegorized with the numerical results computed by state-of-the-art techniques. The graphical and statistical illustration of indications of performance relative to the terms of absolute errors, mean absolute deviations, computational complexity, and mean square error validates that our results perfectly describe the real-life situation and can further be used for problems arising in chemical engineering.
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