Asymptotic stability of constant steady states for a 2×2 reaction–diffusion system arising in cancer modelling

The dependence of tumor on essential nutrients is known to be crucial for its evolution and has become one of the targets for medical therapies. Based on this fact a reaction–diffusion system with chemotaxis term and nutrient-based growth of tumors is presented. The formulation of the model considers also an influence of tumor and pharmacological factors on nutrient concentration. In the paper, convergence of solutions to constant, stationary states in the one-dimensional case for small perturbation of the equilibria is investigated. The nonlinear stability results are obtained by means of the classical symmetrization method and energy Sobolev estimates.     

Phosphorothioated DNA Engineered Liposomes as a General Platform for Stimuli-Responsive Cell-Specific Intracellular Delivery and Genome Editing

Intracellular protein delivery is highly desirable for protein drug-based cell therapy. Established technologies suffer from poor cell-specific cytosolic protein delivery, which hampers the targeting therapy of specific cell populations. A fusogenic liposome system enables cytosolic delivery, but its ability of cell-specific and controllable delivery is quite limited. Inspired by the kinetics of viral fusion, we designed a phosphorothioated DNA coatings-modified fusogenic liposome to mimic the function of viral hemagglutinin. The macromolecular fusion machine docks cargo-loaded liposomes at the membrane of target cells, triggers membrane fusion upon pH or UV light stimuli, and facilitates cytosolic protein delivery. Our results showed efficient cell-targeted delivery of proteins of various sizes and charges, indicating the phosphorothioated DNA plug-in unit on liposomes could be a general strategy for spatial-temporally controllable protein delivery both in vitro and in vivo.     

Reaction Mechanism of CO2 with Choline-Amino Acid Ionic Liquids: A Computational Study

Carbon capture and sequestration are the major applied techniques for mitigating CO2 emission. The marked affinity of carbon dioxide to react with amino groups is well known, and the amine scrubbing process is the most widespread technology. Among various compounds and solutions containing amine groups, in biodegradability and biocompatibility perspectives, amino acid ionic liquids (AAILs) are a very promising class of materials having good CO2 absorption capacity. The reaction of amines with CO2 follows a multi-step mechanism where the initial pathway is the formation of the C−N bond between the NH2 group and CO2. The added product has a zwitterionic character and can rearrange to give a carbamic derivative. These steps of the mechanism have been investigated in the present study by quantum mechanical methods by considering three ILs where amino acid anions are coupled with choline cations. Glycinate, L-phenylalanilate and L-prolinate anions have been compared with the aim of examining if different local structural properties of the amine group can affect some fundamental steps of the CO2 absorption mechanism. All reaction pathways have been studied by DFT methods considering, first, isolated anions in a vacuum as well as in a liquid continuum environment. Subsequently, the role of specific interactions of the anion with a choline cation has been investigated, analyzing the mechanism of the amine–CO2 reaction, including different coupling anion–cation structures. The overall reaction is exothermic for the three anions in all models adopted; however, the presence of the solvent, described by a continuum medium as well as by models, including specific cation- -anion interactions, modifies the values of the reaction energies of each step. In particular, both reaction steps, the addition of CO2 to form the zwitterionic complex and its subsequent rearrangement, are affected by the presence of the solvent. The reaction enthalpies for the three systems are indeed found comparable in the models, including solvent effects.     

大鼠脑缺血再灌注后运动皮质细胞凋亡的体视学观察

用体视学方法分析大鼠脑缺血再灌注后大脑运动皮质细胞的凋亡情况。随机将24只SD大鼠分为缺血再灌注后6、12、24 h和对照组。采用结扎大鼠左侧颈总动脉和夹闭右侧颈总动脉15m in后放开的方法制备大鼠脑缺血再灌注模型。应用Hoechst33258荧光染色及免疫组化Bax蛋白表达来检测细     

双中子星的并合及其引力波和电磁信号

2017年,轰动世界的引力波事件GW170817被确认来自于双中子星的并合。这是人类历史上首次探测到这种极端、剧烈的天体物理事件。双中子星是两个致密天体——中子星组成的系统,由双恒星系统经历漫长演化后形成。文章将从双中子星并合前、并合过程中与并合后全面地描述这种剧烈的天文现象,走进一段神奇而迤逦的旅程。未来随着引力波观测设备的升级,有望再次看到来自宇宙深处的引力波以及伴随的丰富多彩的电磁信号。     

Long‐range π‐type hydrogen bond in dimers CH2?HF,CH2O?H2O,and CH2O?NH3

Using four basis bets, (6‐311G(d,p), 6‐31+G(d,p), 6‐31++G(2d,2p), and 6‐311++G(3df,3pd), the optimized structures with all real frequencies were obtained at the MP2 level for the dimers CH₂O? HF, CH₂O? H₂O, CH₂O? NH₃, and CH₂O? CH₄. The structures of CH₂O? HF, CH₂O? H₂O, and CH₂O? NH₃ are cycle‐shaped, which result from the larger bend of σ‐type hydrogen bonds. The bend of σ‐type H‐bond O…H? Y (Y?F, O, N) is illustrated and interpreted by an attractive interaction of a chemically intuitive π‐type hydrogen bond. The π‐type hydrogen bond is the interaction between one of the H atoms of CH₂O and lone pair(s) on the F atom in HF, the O atom in H₂O, or the N atom in NH₃. In contrast with the above three dimers, for CH₂O? CH₄, because there is not a π‐type hydrogen bond to bend its linear hydrogen bond, the structure of CH₂O? CH₄ is noncyclic shaped. The interaction energy of hydrogen bonds and the π‐type H‐bond are calculated and discussed at the CCSD (T)/6‐311++G(3df,3pd) level. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005