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Nonlinear elastic and viscoelastic deformation of the human red blood cell with optical tweezers. 用光学镊子研究人体红细胞的非线性弹性和粘弹性变形。
J P Mills, L Qie, M Dao, C T Lim, S Suresh

Studies of the deformation characteristics of single biological cells can offer insights into the connections among mechanical state, biochemical response and the onset and progression of diseases. Deformation imposed by optical tweezers provides a useful means for the study of single cell mechanics under a variety of well-controlled stress-states. In this paper, we first critically review recent advances in the study of single cell mechanics employing the optical tweezers method, and assess its significance and limitations in comparison to other experimental tools. We then present new experimental and computational results on shape evolution, force-extension curves, elastic properties and viscoelastic response of human red blood cells subjected to large elastic deformation using optical tweezers. Potential applications of the methods examined here to study diseased cells are also briefly addressed.

研究单个生物细胞的变形特性,可以深入了解细胞的力学状态、生化反应与疾病发生发展之间的关系。光镊施加的变形为研究各种控制良好的应力状态下的单细胞力学提供了一种有用的手段。在本文中,我们首先批判性地回顾了利用光镊方法研究单细胞力学的最新进展,并评估了其与其他实验工具相比的意义和局限性。然后,我们用光学镊子对人体红细胞在大弹性变形下的形状演变、力延伸曲线、弹性特性和粘弹性响应进行了新的实验和计算结果。本文还简要介绍了这些方法在研究病变细胞方面的潜在应用。
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引用次数: 0
Cantilever arrays for multiplexed mechanical analysis of biomolecular reactions. 用于生物分子反应多重力学分析的悬臂阵列。
Min Yue, Jeanne C Stachowiak, Arunava Majumdar

Microchips containing arrays of cantilever beams have been used to mechanically detect and quantitatively analyze multiple reactions of DNA hybridization and antigen-antibody binding simultaneously. The reaction-induced deflection of a cantilever beam reflects the interplay between strain energy increase of the beam and the free energy reduction of a reaction, providing an ideal tool for investigating the connection between mechanics and chemistry of biomolecular reactions. Since free energy reduction is common for all reactions, the cantilever array forms a universal platform for label-free detection of various specific biomolecular reactions. A few such reactions and their implications in biology and biotechnology are discussed.

包含悬臂梁阵列的微芯片已被用于同时机械检测和定量分析DNA杂交和抗原抗体结合的多种反应。悬臂梁的反应引起的挠曲反映了梁的应变能增加与反应的自由能减少之间的相互作用,为研究生物分子反应的力学和化学之间的联系提供了理想的工具。由于自由能还原对所有反应都是常见的,因此悬臂阵列形成了各种特定生物分子反应的无标记检测的通用平台。本文讨论了一些这样的反应及其在生物学和生物技术中的意义。
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引用次数: 0
On the molecular basis for mechanotransduction. 论机械传导的分子基础。
Roger D Kamm, Mohammad R Kaazempur-Mofrad

Much is currently known about the signaling pathways that are excited when cells are subjected to a mechanical stimulus, yet we understand little of the process by which the mechanical perturbation is transformed into a biochemical signal. Numerous theories have been proposed, and each has merit. While cells may possess many different ways of responding to stress, the existence of a single unifying principle has much appeal. Here we propose the hypothesis that cells sense mechanical force through changes in protein conformation, leading to altered binding affinities of proteins, ultimately initiating an intracellular signaling cascade or producing changes in the proteins localized to regions of high stress. More generally, this represents an alternative to transmembrane signaling through receptor-ligand interactions providing the cell with a means of reacting to changes in its mechanical, as opposed to biochemical, environment. One example is presented showing how the binding affinity between the focal adhesion targeting domain of focal adhesion kinase and the LD motif of paxillin is influenced by externally applied force.

当细胞受到机械刺激时,信号通路被激发,目前我们知道的很多,但我们对机械扰动转化为生化信号的过程知之甚少。人们提出了许多理论,每种理论都有其优点。虽然细胞可能有许多不同的方式来应对压力,但存在一个统一的原则是很有吸引力的。在这里,我们提出了一种假设,即细胞通过改变蛋白质的构象来感知机械力,从而改变蛋白质的结合亲和力,最终启动细胞内信号级联或产生位于高应激区域的蛋白质的变化。更一般地说,这代表了一种通过受体-配体相互作用的跨膜信号的替代方法,为细胞提供了一种对其机械环境(而不是生化环境)变化作出反应的手段。一个例子显示了焦点粘附激酶的焦点粘附靶向区域与paxillin的LD基序之间的结合亲和力如何受到外力的影响。
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引用次数: 0
Determination of membrane tension during balloon distension of intestine. 肠球囊扩张过程中膜张力的测定。
Pub Date : 2004-09-01 DOI: 10.3970/MCB.2004.001.191
Hans Gregersen, G. S. Kassab, Yuan-Cheng B. Fung
During the last decades, it has become increasingly common to make balloons distension in visceral organs in vivo. In particular this is true for studies of gastrointestinal motor function and biomechanics. Balloon distension is often used for assessment of small intestinal compliance and tension based on Laplace's law for cylindrical pressure pipes. This commonly used law is valid only when the balloon-distended intestine is cylindrical. Experimentally, it is seen that the diameter of the balloon-distended intestine is not a constant, but variable in the axial direction. Hence, it is necessary to improve Laplace's law for intestinal investigation. In this paper we develop the framework for determination of the tension distribution in circumferential and longitudinal direction during balloon distension. When the radii of curvature are measured from a photograph of the intestinal profile, then the membrane stress resultants can be computed everywhere in the intestine in contact with the balloon from the equations of equilibrium. The experimental data were obtained from small intestinal segments from five pigs and three guinea pigs. Papaverine was injected before the animals were sacrificed to relax the intestinal smooth muscle. The segments were immersed in a bath with calcium-free Krebs solution with dextran and EGTA. A balloon was distended in the lumen with pressures up to 15 cmH2O in the pigs and 10 cmH2O in the guinea pigs and radii were measured along the z-axis. The tension in circumferential direction had its maximum approximately 25% away from the middle of the balloon. The circumferential tension was 2-3 times higher than the longitudinal tension. In conclusion when we know the shape of the intestine, we can compute the circumferential and longitudinal components of tension. The large variation in tensions along the z axis must be considered when performing balloon distension studies in the gastrointestinal tract for studying physiological and pathophysiological problems in which loading conditions are important, e.g. intestinal mechanoreceptor studies in order to obtain accurate description of the biomechanics and the stimulus-response function.
在过去的几十年里,在体内内脏器官中使气球膨胀已经变得越来越普遍。对于胃肠道运动功能和生物力学的研究尤其如此。基于圆柱压力管的拉普拉斯定律,气囊扩张常用于小肠顺应性和张力的评估。这个常用的规律只有在气球膨胀的肠呈圆柱形时才有效。实验发现,气球膨胀肠的直径在轴向上不是恒定的,而是变化的。因此,有必要对肠道调查中的拉普拉斯定律进行改进。本文建立了测定气球膨胀过程中周向和纵向张力分布的框架。当从肠道轮廓的照片中测量曲率半径时,就可以根据平衡方程计算出与气球接触的肠道中任何地方的膜应力结果。实验数据取自5头猪和3只豚鼠的小肠段。在处死前注射罂粟碱放松肠道平滑肌。片段浸泡在含有葡聚糖和EGTA的无钙Krebs溶液中。在猪和豚鼠的管腔内用压力分别达到15 cmH2O和10 cmH2O的球囊膨胀,沿z轴测量半径。在距离球囊中心约25%处,圆周方向的张力达到最大值。周向张力比纵向张力高2-3倍。总之,当我们知道肠的形状时,我们可以计算出张力的周向和纵向分量。为了准确描述生物力学和刺激-反应函数,在研究负荷条件重要的生理和病理生理问题(如肠机械受体研究)时,在胃肠道进行球囊膨胀研究时,必须考虑沿z轴张力的大变化。
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引用次数: 11
On the molecular basis for mechanotransduction. 论机械传导的分子基础。
Pub Date : 2004-09-01 DOI: 10.3970/MCB.2004.001.201
R. Kamm, M. Kaazempur-Mofrad
Much is currently known about the signaling pathways that are excited when cells are subjected to a mechanical stimulus, yet we understand little of the process by which the mechanical perturbation is transformed into a biochemical signal. Numerous theories have been proposed, and each has merit. While cells may possess many different ways of responding to stress, the existence of a single unifying principle has much appeal. Here we propose the hypothesis that cells sense mechanical force through changes in protein conformation, leading to altered binding affinities of proteins, ultimately initiating an intracellular signaling cascade or producing changes in the proteins localized to regions of high stress. More generally, this represents an alternative to transmembrane signaling through receptor-ligand interactions providing the cell with a means of reacting to changes in its mechanical, as opposed to biochemical, environment. One example is presented showing how the binding affinity between the focal adhesion targeting domain of focal adhesion kinase and the LD motif of paxillin is influenced by externally applied force.
当细胞受到机械刺激时,信号通路被激发,目前我们知道的很多,但我们对机械扰动转化为生化信号的过程知之甚少。人们提出了许多理论,每种理论都有其优点。虽然细胞可能有许多不同的方式来应对压力,但存在一个统一的原则是很有吸引力的。在这里,我们提出了一种假设,即细胞通过改变蛋白质的构象来感知机械力,从而改变蛋白质的结合亲和力,最终启动细胞内信号级联或产生位于高应激区域的蛋白质的变化。更一般地说,这代表了一种通过受体-配体相互作用的跨膜信号的替代方法,为细胞提供了一种对其机械环境(而不是生化环境)变化作出反应的手段。一个例子显示了焦点粘附激酶的焦点粘附靶向区域与paxillin的LD基序之间的结合亲和力如何受到外力的影响。
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引用次数: 63
An improved mathematical approach for determination of molecular kinetics in living cells with FRAP. 用FRAP测定活细胞分子动力学的改进数学方法。
Pub Date : 2004-09-01 DOI: 10.3970/MCB.2004.001.181
T. Lele, P. Oh, J. Nickerson, D. Ingber
The estimation of binding constants and diffusion coefficients of molecules that associate with insoluble molecular scaffolds inside living cells and nuclei has been facilitated by the use of Fluorescence Recovery after Photobleaching (FRAP) in conjunction with mathematical modeling. A critical feature unique to FRAP experiments that has been overlooked by past mathematical treatments is the existence of an 'equilibrium constraint': local dynamic equilibrium is not disturbed because photobleaching does not functionally destroy molecules, and hence binding-unbinding proceeds at equilibrium rates. Here we describe an improved mathematical formulation under the equilibrium constraint which provides a more accurate estimate of molecular reaction kinetics within FRAP studies carried out in living cells. Due to incorporation of the equilibrium constraint, the original nonlinear kinetic terms become linear allowing for analytical solution of the transport equations and greatly simplifying the estimation process. Based on mathematical modeling and scaling analysis, two experimental measures are identified that can be used to delineate the rate-limiting step. A comprehensive analysis of the interplay between binding-unbinding and diffusion, and its effect on the recovery curve, are presented. This work may help to bring clarity to the study of molecular dynamics within the structural complexity of living cells.
利用光漂白后荧光恢复(FRAP)与数学建模相结合,可以估计活细胞和细胞核内与不溶性分子支架相关的分子的结合常数和扩散系数。过去的数学处理忽略了FRAP实验独有的一个关键特征,即“平衡约束”的存在:局部动态平衡不会受到干扰,因为光漂白不会在功能上破坏分子,因此结合-解结合以平衡速率进行。在这里,我们描述了一个在平衡约束下改进的数学公式,它提供了在活细胞中进行的FRAP研究中分子反应动力学的更准确估计。由于加入了平衡约束,原来的非线性动力学项变成了线性的,从而可以解析求解输运方程,大大简化了估计过程。在数学建模和尺度分析的基础上,确定了两种可用于描述限速步骤的实验方法。综合分析了结合-解结合与扩散之间的相互作用及其对回收率曲线的影响。这项工作可能有助于使活细胞结构复杂性中的分子动力学研究更加清晰。
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引用次数: 30
An improved mathematical approach for determination of molecular kinetics in living cells with FRAP. 用FRAP测定活细胞分子动力学的改进数学方法。
Tanmay Lele, Philmo Oh, Jeffrey A Nickerson, Donald E Ingber

The estimation of binding constants and diffusion coefficients of molecules that associate with insoluble molecular scaffolds inside living cells and nuclei has been facilitated by the use of Fluorescence Recovery after Photobleaching (FRAP) in conjunction with mathematical modeling. A critical feature unique to FRAP experiments that has been overlooked by past mathematical treatments is the existence of an 'equilibrium constraint': local dynamic equilibrium is not disturbed because photobleaching does not functionally destroy molecules, and hence binding-unbinding proceeds at equilibrium rates. Here we describe an improved mathematical formulation under the equilibrium constraint which provides a more accurate estimate of molecular reaction kinetics within FRAP studies carried out in living cells. Due to incorporation of the equilibrium constraint, the original nonlinear kinetic terms become linear allowing for analytical solution of the transport equations and greatly simplifying the estimation process. Based on mathematical modeling and scaling analysis, two experimental measures are identified that can be used to delineate the rate-limiting step. A comprehensive analysis of the interplay between binding-unbinding and diffusion, and its effect on the recovery curve, are presented. This work may help to bring clarity to the study of molecular dynamics within the structural complexity of living cells.

利用光漂白后荧光恢复(FRAP)与数学建模相结合,可以估计活细胞和细胞核内与不溶性分子支架相关的分子的结合常数和扩散系数。过去的数学处理忽略了FRAP实验独有的一个关键特征,即“平衡约束”的存在:局部动态平衡不会受到干扰,因为光漂白不会在功能上破坏分子,因此结合-解结合以平衡速率进行。在这里,我们描述了一个在平衡约束下改进的数学公式,它提供了在活细胞中进行的FRAP研究中分子反应动力学的更准确估计。由于加入了平衡约束,原来的非线性动力学项变成了线性的,从而可以解析求解输运方程,大大简化了估计过程。在数学建模和尺度分析的基础上,确定了两种可用于描述限速步骤的实验方法。综合分析了结合-解结合与扩散之间的相互作用及其对回收率曲线的影响。这项工作可能有助于使活细胞结构复杂性中的分子动力学研究更加清晰。
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引用次数: 0
Nonlinear elastic and viscoelastic deformation of the human red blood cell with optical tweezers. 用光学镊子研究人体红细胞的非线性弹性和粘弹性变形。
Pub Date : 2004-09-01 DOI: 10.3970/MCB.2004.001.169
J. P. Mills, L. Qie, M. Dao, Chwee Teck Lim, S. Suresh
Studies of the deformation characteristics of single biological cells can offer insights into the connections among mechanical state, biochemical response and the onset and progression of diseases. Deformation imposed by optical tweezers provides a useful means for the study of single cell mechanics under a variety of well-controlled stress-states. In this paper, we first critically review recent advances in the study of single cell mechanics employing the optical tweezers method, and assess its significance and limitations in comparison to other experimental tools. We then present new experimental and computational results on shape evolution, force-extension curves, elastic properties and viscoelastic response of human red blood cells subjected to large elastic deformation using optical tweezers. Potential applications of the methods examined here to study diseased cells are also briefly addressed.
研究单个生物细胞的变形特性,可以深入了解细胞的力学状态、生化反应与疾病发生发展之间的关系。光镊施加的变形为研究各种控制良好的应力状态下的单细胞力学提供了一种有用的手段。在本文中,我们首先批判性地回顾了利用光镊方法研究单细胞力学的最新进展,并评估了其与其他实验工具相比的意义和局限性。然后,我们用光学镊子对人体红细胞在大弹性变形下的形状演变、力延伸曲线、弹性特性和粘弹性响应进行了新的实验和计算结果。本文还简要介绍了这些方法在研究病变细胞方面的潜在应用。
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引用次数: 333
Illuminating the dynamics of intracellular activity with 'active' molecular reporters. 用“活跃的”分子报告器阐明细胞内活动的动力学。
A Tsourkas, R Weissleder

Traditionally, fluorescent and luminescent reporter proteins have been used as indicators of gene expression and protein localization. However, insightful mutagenesis and protein engineering strategies have transformed these simple passive reporters into active biological sensors. Molecular reporters are now being designed to alter their intrinsic optical properties in response to specific biomolecular interactions. Applications for these novel biological sensors range from monitoring intracellular pH and ion fluxes to detecting protein-protein interactions and enzymatic activity. The ability to monitor the dynamics of intracellular activity in response to external stimuli can help elucidate the cascade of events involved in complex processes such as mechanotransduction. Here we review some of the approaches used to create these novel biological sensors, including resonance energy transfer (RET) between reporter proteins and protein fragmentation strategies.

传统上,荧光和发光报告蛋白被用作基因表达和蛋白质定位的指标。然而,深刻的诱变和蛋白质工程策略已经将这些简单的被动报告变成了主动的生物传感器。分子报告器现在被设计用来改变其固有的光学特性,以响应特定的生物分子相互作用。这些新型生物传感器的应用范围从监测细胞内pH值和离子通量到检测蛋白质相互作用和酶活性。监测响应外部刺激的细胞内活动动态的能力可以帮助阐明复杂过程(如机械转导)中涉及的级联事件。在这里,我们回顾了一些用于创建这些新型生物传感器的方法,包括报告蛋白之间的共振能量转移(RET)和蛋白质碎片化策略。
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引用次数: 0
A simple phenomenological theory of tissue growth. 组织生长的简单现象学理论。
Pub Date : 2004-06-01 DOI: 10.3970/MCB.2004.001.147
K. Volokh
A simple phenomenological framework for modeling growth of living tissues is proposed. Growth is defined as a change of mass and configuration of the tissue. Tissue is considered as an open system where mass conservation is violated and the full-scale mass balance is applied. A possible structure of constitutive equations is discussed with reference to simple growing materials. 'Thermoelastic' formulation of the simple growing material is specified. Within this framework traction free growth of cylindrical and spherical bodies is examined. It is shown that the theory accommodates the case where stresses are not generated in uniform volumetric growth. It is also found that surface growth corresponds to a boundary layer solution of the governing equations. This finding proves the ability of continuum mechanics to describe surface growth. The latter is contrary to the usual use of purely kinematical theories, which do not involve balance and constitutive equations, for treating surface growth.
提出了一个简单的现象学框架来模拟活组织的生长。生长被定义为组织质量和结构的变化。组织被认为是一个开放的系统,质量守恒被打破,全尺寸质量平衡被应用。参考简单生长材料,讨论了本构方程的一种可能结构。指定了简单生长材料的“热弹性”配方。在这个框架内,柱体和球体的牵引自由生长进行了研究。结果表明,该理论适用于在均匀体积增长中不产生应力的情况。还发现,表面生长对应于控制方程的边界层解。这一发现证明了连续介质力学描述表面生长的能力。后者与通常使用的纯运动学理论相反,后者不涉及平衡和本构方程,用于处理表面生长。
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引用次数: 10
期刊
Mechanics & chemistry of biosystems : MCB
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