Preliminary Structural Data Revealed That the SARS-CoV-2 B.1.617 Variant's RBD Binds to ACE2 Receptor Stronger Than the Wild Type to Enhance the Infectivity

The evolution of new SARS-CoV-2 variants around the globe has made the COVID-19 pandemic more worrisome, further pressuring the health care system and immunity. Novel variations that are unique to the receptor-binding motif (RBM) of the receptor-binding domain (RBD) spike glycoprotein, i. e. L452R-E484Q, may play a different role in the B.1.617 (also known as G/452R.V3) variant's pathogenicity and better survival compared to the wild type. Therefore, a thorough analysis is needed to understand the impact of these mutations on binding with host receptor (RBD) and to guide new therapeutics development. In this study, we used structural and biomolecular simulation techniques to explore the impact of specific mutations (L452R-E484Q) in the B.1.617 variant on the binding of RBD to the host receptor ACE2. Our analysis revealed that the B.1.617 variant possesses different dynamic behaviours by altering dynamic-stability, residual flexibility and structural compactness. Moreover, the new variant had altered the bonding network and structural-dynamics properties significantly. MM/GBSA technique was used, which further established the binding differences between the wild type and B.1.617 variant. In conclusion, this study provides a strong impetus to develop novel drugs against the new SARS-CoV-2 variants.     

Suppressing Ion Migration across Perovskite Grain Boundaries by Polymer Additives

Passivation of organometal halide perovskites with polar molecules has been recently demonstrated to improve the photovoltaic device efficiency and stability. However, the mechanism is still elusive. Here, it is found that both polymers with large and small dipole moment of 3.7 D and 0.6 D have negligible defect passivation effect on the MAPbI₃ perovskite films as evidenced by photothermal deflection spectroscopy. The photovoltaic devices with and without the polymer additives also have comparable power conversion efficiencies around 19%. However, devices with the additives have noticeable improvement in stability under continuous light irradiation. It is found that although the initial mobile ion concentrations are comparable in both devices with and without the additives, the additives can strongly suppress the ion migration during the device operation. This contributes to the significantly enhanced electrical-field stress tolerance of the perovskite solar cells (PVSCs). The PVSCs with polymer additives can operate up to −2 V reverse voltage bias which is much larger than the breakdown voltage of −0.5 V that has been commonly observed. This study provides insight into the role of additives in perovskites and the corresponding device degradation mechanism.     

High-pressure hydrogen storage performances of ZrFe2 based alloys with Mn,Ti, and V addition

The microstructure of ZrFe₂-based alloys were modified by alloying with the Mn, Ti, and V, aiming to obtain proper hydriding/dehydriding plateau features for the high-pressure application. The multi-component ZrFe₂-based alloys show a wide tunable range in the plateau pressure via the interaction of Ti, Mn, and V. Further, the V addition plays the best role to improve the hysteresis in absorption-desorption isotherms, while the proper addition amount Ti helps to realize a low plateau slope as well as a high plateau pressure. Among the investigated alloys, Zr_1.05Fe_1.6Mn_0.4 shows a relatively high dehydriding pressure of 20.58 atm at 298 K, while Zr_1.05Fe_1.7Mn_0.2V_0.1 with C15 structure shows the lowest hysteresis. Overall, too much of Ti and Mn would promote the transformation of the C15 to C14 structure with large hysteresis and low plateau pressure.     

全透明高压反应釜甲烷水合物动力学实验

水合物的生长和分解规律对开发海洋天然气水合物资源，实现深水天然气水合物气液固多相管道输送都具有重要意义。为了进一步揭示水合物的生长和分解特性，本文采用高压全透明反应釜装置，进行了温度0～30℃、压力3.35～8.16MPa和搅拌速率200～1000r/min范围内的16组甲烷水合物生长和分解动力学实验研究。结果表明：实验过程可分为水合物诱导期、快速生长期、缓慢生长期以及分解期这4个阶段。在水合物快速生长阶段，获得了温度、压力、搅拌电机扭矩和水合物生长速率随时间的变化规律，观察到了水合物颗粒的均相和非均相分布状态。通过加热促使水合物分解，揭示了分解阶段温度、压力和分解速率等关键参数的变化规律以及水合物块的分解形态。分析表明，水合物颗粒的分布状态与水合物浆液的流动性直接相关；水合物块的静态分解过程受到分解气传质控制。     

钾长石-硫酸钙-碳酸钙体系提钾添加剂的实验研究

研究了不同温度下氯化钙、硫酸钠对钾长石-硫酸钙-碳酸钙体系[n(microcline)∶n(CaSO4)∶n(CaCO3)=1∶1∶14]钾熔出率的影响,并进一步研究了加入硫酸钠时的热分解反应动力学。结果表明:硫酸钠可有效地促进钾长石的热分解,当其添加量为2.91%时,反应温度可降为1050℃,表观活化能可降为87.71kJ/mol;在950℃、1050℃时,钾长石释钾主要机理是离子交换;在1150℃时,钾长石释钾机理主要是阴离子吸附。     

FOX-7团簇中分子间相互作用对其裂解影响的量子化学研究

采用色散校正密度泛函理论的RI-B2PLYP-D3和PW6B95-D3方法得到了1,1-二氨基-2,2-二硝基乙烯(FOX-7)的四种气相团簇,以此模拟FOX-7分子在晶体结构中的存在状态。绘制了团簇形成过程中各分子相邻处的电子密度差图,从电子密度变化的角度解释了分子间相互作用的形成及来源,研究了凝聚相FOX-7分子间相互作用对FOX-7裂解机理的影响。结果表明,FOX-7团簇中分子间相互作用源于电子偏移形成的部分分子间共享电子,分子间相互作用形成的同时也使部分分子内的化学键被弱化,致使FOX-7的裂解通道发生改变。采用PW6B95-D3理论时,分子间相互作用使各团簇中FOX-7的C—NO_2键裂解活化能比单分子状态时普遍降低。不同团簇中分子间相互作用力角度不同,硝基异构反应的过程有所变化,与单分子FOX-7相比,团簇Ⅱ硝基异构通道的活化能下降了210.9 k J·mol~(-1),而团簇Ⅳ硝基异构通道的活化能升高了39.4 k J·mol~(-1)。     

考虑固相分解的含水合物沉积物体积应变分析模型

水合物开采通过打破固相水合物相平衡状态使其分解为水和气体,含水合物沉积物（gas hydrate-bearing sediment,GHBS）固相组分减少使孔隙体积增大,土骨架间胶结作用弱化,产生的水和气显著改变孔隙压力,造成沉积物软化和体积收缩。基于GHBS三轴压缩试验,考虑水合物降压分解过程对GHBS变形特性的影响,将固相骨架分为惰性土骨架和可分解的水合物固相,引入随水合物饱和度变化的压缩参数,建立了能够描述GHBS应力和水合物分解耦合作用、体积应变随时间变化的分析模型。该模型能够描述降压速率、降压幅值及水合物分解速率对GHBS变形特性的影响,结果表明：降压速率增大,降压阶段体积应变速率增大,达到相平衡时间缩短,降压开采时应综合考虑开采过程中储层变形速率和开采效率间的关系;不同粒径组成的沉积物水合物分解速率存在差异,分解速率对储层变形速率影响明显;降压开采稳定孔压影响储层最终沉降量,降低稳定孔压可以提高开采效率,但最终变形量增大。     

溶剂法制备天然橡胶结合胶的研究

结合胶是未硫化的混炼胶中不能被其良溶剂溶解的那部分橡胶。用化学溶剂法制备结合胶具有药品用量小、实验过程操作简单,重现性好等优点。通过讨论橡胶加入量、炭黑用量、反应时间、静置时间等因素,确定了溶剂法制备结合胶的最佳工艺参数,并与混炼法制备的结合胶进行了性能对比。结果表明,橡胶在甲苯溶液中的质量浓度约为0.02g/mL、橡胶和炭黑的质量比为2∶1、反应时间为14h、静置时间为72h的工艺参数下,可以制得高质量结合胶。混炼法制备的结合胶的质量比溶剂法制备的结合胶的质量大。但是其具有与溶剂法结合胶相同的抽提温度曲线,在结合胶的实验研究中,可以用溶剂法代替混炼法。     

A density functional theory study of methane activation on MgO supported Ni9M1 cluster: role of M on C–H activation

Methane activation is a pivotal step in the application of natural gas converting into high-value added chemicals via methane steam/dry reforming reactions. Ni element was found to be the most widely used catalyst. In present work, methane activation on MgO supported Ni–M (M = Fe, Co, Cu, Pd, Pt) cluster was explored through detailed density functional theory calculations, compared to pure Ni cluster. CH₄ adsorption on Cu promoted Ni cluster requires overcoming an energy of 0.07 eV, indicating that it is slightly endothermic and unfavored to occur, while the adsorption energies of other promoters M (M = Fe, Co, Pd and Pt) are all higher than that of pure Ni cluster. The role of M on the first C–H bond cleavage of CH₄ was investigated. Doping elements of the same period in Ni cluster, such as Fe, Co and Cu, for C–H bond activation follows the trend of the decrease of metal atom radius. As a result, Ni–Fe shows the best ability for C–H bond cleavage. In addition, doping the elements of the same family, like Pd and Pt, for CH₄ activation is according to the increase of metal atom radius. Consequently, C–H bond activation demands a lower energy barrier on Ni–Pt cluster. To illustrate the adsorptive dissociation behaviors of CH₄ at different Ni–M clusters, the Mulliken atomic charge was analyzed. In general, the electron gain of CH₄ binding at different Ni–M clusters follows the sequence of Ni–Cu (–0.02 e) < Ni (–0.04 e) < Ni–Pd (–0.08 e) < Ni–Pt (–0.09 e) < Ni–Co (–0.10 e) < Ni–Fe (–0.12 e), and the binding strength between catalysts and CH ₄ raises with the CH₄ electron gain increasing. This work provides insights into understanding the role of promoter metal M on thermal-catalytic activation of CH₄ over Ni/MgO catalysts, and is useful to interpret the reaction at an atomic scale.     

MALDI Q-TOF CID MS for Diagnostic Ion Screening of Human Milk Oligosaccharide Samples

Human milk oligosaccharides (HMO) represent the bioactive components of human milk, influencing the infant’s gastrointestinal microflora and immune system. Structurally, they represent a highly complex class of analyte, where the main core oligosaccharide structures are built from galactose and N-acetylglucosamine, linked by 1–3 or 1–4 glycosidic linkages and potentially modified with fucose and sialic acid residues. The core structures can be linear or branched. Additional structural complexity in samples can be induced by endogenous exoglycosidase activity or chemical procedures during the sample preparation. Here, we show that using matrix-assisted laser desorption/ionization (MALDI) quadrupole-time-of-flight (Q-TOF) collision-induced dissociation (CID) as a fast screening method, diagnostic structural information about single oligosaccharide components present in a complex mixture can be obtained. According to sequencing data on 14 out of 22 parent ions detected in a single high molecular weight oligosaccharide chromatographic fraction, 20 different oligosaccharide structure types, corresponding to over 30 isomeric oligosaccharide structures and over 100 possible HMO isomers when biosynthetic linkage variations were taken into account, were postulated. For MS/MS data analysis, we used the de novo sequencing approach using diagnostic ion analysis on reduced oligosaccharides by following known biosynthetic rules. Using this approach, de novo characterization has been achieved also for the structures, which could not have been predicted.