Binding constant of cell adhesion receptors and substrate-immobilized ligands depends on the distribution of ligands

Cell-cell adhesion and the adhesion of cells to tissues and extracellular matrix, which are pivotal for immune response, tissue development, and cell locomotion, depend sensitively on the binding constant of receptor and ligand molecules anchored on the apposing surfaces. An important question remains of whether the immobilization of ligands affects the affinity of binding with cell adhesion receptors. We have investigated the adhesion of multicomponent membranes to a flat substrate coated with immobile ligands using Monte Carlo simulations of a statistical mesoscopic model with biologically relevant parameters. We find that the binding of the adhesion receptors to ligands immobilized on the substrate is strongly affected by the ligand distribution. In the case of ligand clusters, the receptor-ligand binding constant can be significantly enhanced due to the less translational entropy loss of lipid-raft domains in the model cell membranes upon the formation of additional complexes. For ligands randomly or uniformly immobilized on the substrate, the binding constant is rather decreased since the receptors localized in lipid-raft domains have to pay an energetic penalty in order to bind ligands. Our findings help to understand why cell-substrate adhesion experiments for measuring the impact of lipid rafts on the receptor-ligand interactions led to contradictory results

晶状体蛋白液-液相分离及逾渗相变的分子动力学模拟研究

探究不同势场下晶状体蛋白胶体粒子的微观分布与结构特性,研究单元系晶状体蛋白体系的液-液相分离及逾渗相变过程

氟苯尼考在日本囊对虾体内的药代动力学研究

为了给养殖日本囊对虾制定正确的用药方案、确定氟苯尼考的休药期提供科学依据,应用反相高效液相色谱法(rP-HPlC)研究了氟苯尼考在日本囊对虾体内的药物代谢动力学。试验结果表明,在水温23±0.5℃,盐度29.91的条件下,氟苯尼考在肝脏、肌肉和血淋巴的平均回收率为93.37%、91.79%、91.82%;试验数据经药代动力学软件3P97分析表明,日本囊对虾采用氟苯尼考单次腹部肌肉注射,其肌肉药—时数据符合二室模型,肝脏和血淋巴药—时数据符合一室模型。其中,氟苯尼考在肝脏、肌肉和血淋巴中的主要动力学参数分别为:浓度—时间曲线的曲线下面积AuC分别为10.315、0.77、14.33(μg/g).H;药物的峰值浓度C(MAX)分别为13.03、10.46、8.031μg/g;药物浓度处于峰值时的时间TP分别为0.2044、0.22980、.6544 H;吸收半衰期分别为0.67710、.4746、0.4193 H;消除半衰期分别为3.766、16.16、4.917 H。建议在23±0.5℃的水温条件下,氟苯尼考对日本囊对虾的休药期不少于7 d。山东省高等学校优秀青年教师国内访问学者项目;公益性行业(农业)科研专项(200803012)资

Non-Fourier effect and inertia effect analysis of a strip with an induced crack under thermal shock loading

In this paper, the transient temperature fields and the dynamic stress intensity factors of a thermo-elastic strip containing an inner crack parallel to the heated surface under thermal shock are studied. The Biot number of the crack gap, hyperbolic heat conduction theory and equation of motion are considered to investigate the behavior of the temperature fields around the crack and the stress intensity factors. Fourier transform and Laplace transform are used to reduce this mixed boundary value problem. Numerical methods are used to solved the singular integrate equations. Finally, the numerical results are presented illustrating the influence of Biot number, non-Fourier effect and inertia effect on temperature field and stress intensity factors. It is found that the Biot number strongly affect the uniformity of the temperature field and the magnitude of the stress intensity factors. The stress intensity factors have higher amplitude and an oscillating feature comparing to those obtained under conventional Fourier thermal conduction condition and quasi-static hypothesis, which can help to better understand the crack behaviors of advanced materials under thermal impact loading. (C) 2016 Elsevier Ltd. All rights reserved

Impact of lipid rafts on the T-cell-receptor and peptide-major-histocompatibility-complex interactions under different measurement conditions

The interactions between T-cell receptor (TCR) and peptide-major-histocompatibility complex (pMHC), which enable T-cell development and initiate adaptive immune responses, have been intensively studied. However, a central issue of how lipid rafts affect the TCR-pMHC interactions remains unclear. Here, by using a statistical-mechanical membrane model, we show that the binding affinity of TCR and pMHC anchored on two apposing cell membranes is significantly enhanced because of the lipid raft-induced signaling protein aggregation. This finding may provide an alternative insight into the mechanism of T-cell activation triggered by very low densities of pMHC. In the case of cell-substrate adhesion, our results indicate that the loss of lateral mobility of the proteins on the solid substrate leads to the inhibitory effect of lipid rafts on TCR-pMHC interactions. Our findings help to understand why different experimental methods for measuring the impact of lipid rafts on the receptor-ligand interactions have led to contradictory conclusions

Deformation of Surface Nanobubbles Induced by Substrate Hydrophobicity

Recent experimental measurements have shown that there exists a population of nanobubbles with different curvature radii, whereas both computer simulations and theoretical analysis indicated that the curvature radii of different nanobubbles should be the same at a given supersaturation. To resolve such inconsistency, we perform molecular dynamics simulations on surface nanobubbles that are stabilized by heterogeneous substrates either in the geometrical heterogeneity model (GHM) or in the chemical heterogeneity model (CHM) and propose that the inconsistency could be ascribed to the substrate-induced nanobubble deformation. We find that, as expected from theory and computer simulation, for either the GHM or the CHM, there exists a universal upper limit of contact angle for the nanobubbles, which is determined by the degree of supersaturation alone. By analyzing the evolution of the shape of nanobubbles as a function of substrate hydrophobicity that is controlled here by the liquid-solid interaction, two different origins of nanobubble deformation are identified. For substrates in the GHM, where the contact line is pinned by surface roughness, variation in the liquid-solid interaction changes only the location of the contact line and the measured contact angle; without causing a change in the nanobubble curvature. For substrates in the CHM, however, the liquid-solid interaction exerted by the bottom substrate can deform the vapor-liquid interface, resulting in variations in both the curvature of the vapor-liquid interface and the contact angle

中国物理海洋学研究70年：发展历程、学术成就概览

本文概略评述新中国成立70年来物理海洋学各分支研究领域的发展历程和若干学术成就。中国物理海洋学研究起步于海浪、潮汐、近海环流与水团,以及以风暴潮为主的海洋气象灾害的研究。随着国力的增强,研究领域不断拓展,涌现了大量具有广泛影响力的研究成果,其中包括:提出了被国际广泛采用的"普遍风浪谱"和"涌浪谱",发展了第三代海浪数值模式;提出了"准调和分析方法"和"潮汐潮流永久预报"等潮汐潮流的分析和预报方法;发现并命名了"棉兰老潜流",揭示了东海黑潮的多核结构及其多尺度变异机理等,系统描述了太平洋西边界流系;提出了印度尼西亚贯穿流的南海分支(或称南海贯穿流);不断完善了中国近海陆架环流系统,在南海环流、黑潮及其分支、台湾暖流、闽浙沿岸流、黄海冷水团环流、黄海暖流、渤海环流,以及陆架波方面均取得了深刻的认识;从大气桥和海洋桥两个方面对太平洋–印度洋–大西洋洋际相互作用进行了系统的总结;发展了浅海水团的研究方法,基本摸清了中国近海水团的分布和消长特征与机制,在大洋和极地水团分布及运动研究方面也做出了重要贡献;阐明了南海中尺度涡的宏观特征和生成机制,揭示了中尺度涡的三维结构,定量评估了其全球物质与能量输运能力;基本摸清了中国近海海洋锋的空间分布和季节变化特征,提出了地形、正压不稳定和斜压不稳定等锋面动力学机制;构建了"南海内波潜标观测网",实现了对内波生成–演变–消亡全过程机理的系统认识;发展了湍流的剪切不稳定理论,提出了海流"边缘不稳定"的概念,开发了海洋湍流模式,提出了湍流混合参数化的新方法等;在海洋内部混合机制和能量来源方面取得了新的认识,并阐述了混合对海洋深层环流、营养物质输运等过程的影响;研发了全球浪–潮–流耦合模式,推出一系列海洋与气候模式;发展了可同化主要海洋观测数据的海洋数据同化系统和用于ENSO预报的耦合同化系统;建立了达到国际水准的非地转(水槽/水池)和地转(旋转平台)物理模型实验平台;发展了ENSO预报的误差分析方法,建立了海洋和气候系统年代际变化的理论体系,揭示了中深层海洋对全球气候变化的响应;初步建成了中国近海海洋观测网;持续开展南北极调查研究;建立了台风、风暴潮、巨浪和海啸的业务化预报系统,为中国气象减灾提供保障;突破了国外的海洋技术封锁,研发了万米水深的深水水听器和海洋光学特性系列测量仪器;建立了溢油、危险化学品漂移扩散等预测模型,为伴随海洋资源开发所带来的风险事故的应急处理和预警预报提供科学支撑。文中引用的大量学术成果文献(每位第一作者优选不超过3篇)显示,经过70年的发展,中国物理海洋学研究培养了一支实力雄厚的科研队伍,这是最宝贵的成果。这支队伍必将成为中国物理海洋学研究攀登新高峰的主力军

仿生纳米界面及其热性能研究

通过对超高温陶瓷材料表面进行仿蜻蜓翼膜表面结构的粗糙化处理,使陶瓷表面成为一种纳米尺度的散热肋结构。实验证明,这种仿生纳米肋结构能够使陶瓷材料在直到接近其熔点温度的热震下也不会发生强度突变。进一步对其机制的研究表明,在陶瓷材料的热震过程中,

仿生学里的小结构大力学

我们生活的世界和大自然经历了亿万年的演化。演化的过程是，物竞天择，优胜劣汰。通过这种演化过程，现存地球上的生物，不管是动物或者是植物都具备了一种与自身生活环境相适应的特殊形态，或者说是功能