Diffusion of microspheres in shear flow near a wall: Use to measure binding rates between attached molecules
Diffusion of microspheres in shear flow near a wall: Use to measure binding rates between attached molecules
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DOI：
10.1016/s0006-3495(01)75677-9
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发表时间：
2001-07-01
影响因子：
3.4
通讯作者：
Bongrand, P
中科院分区：
文献类型：
--
作者：
Pierres, A;Benoliel, AM;Bongrand, P
表面附着分子之间缔合的速率和距离依赖性可以通过监测承载受体的球体沿着流动室中配体涂覆的表面的运动来确定（Pierres等人，Proc. Natl. Acad. Sci. U.S.A. 95：9256-9261，1998）。颗粒滞留揭示键的形成，和颗粒到表面的距离可以从速度和壁剪切速率之间的比率估计。然而，提出了几个问题。首先，数据解释需要大量的计算机模拟。其次，流体力学的标准结果与微米级颗粒与表面纳米级距离的相关性没有得到充分证明。第三，必须以高精度知道壁剪切速率。在这里，我们提出了一个简单的推导算法，允许一个模拟剪切流中的平面附近的球体的运动。我们检查，理论预测是一致的实验依赖于介质粘度或颗粒大小的运动，并要求平衡粒子高度分布遵循玻尔兹曼定律。颗粒速度和加速度之间的统计关系的确定允许人们以1-s（-1）的精度导出壁剪切速率，并且以优于10（-21）J的灵敏度导出颗粒与壁之间的相互作用的Hamaker常数。0.2 s（对于半径为1.4 μ m的颗粒）。当颗粒到表面的距离范围在10和40 nm之间时，可以获得具有范围在8和25 nm之间的标准偏差的颗粒高度分布，条件是以10%的精度确定160 ms时间段期间的平均速度。它的结论是，流动室允许一个检测的最小寿命为40 ms的存在下，类似于5 pN的破坏力的个别键的形成，并评估在几十纳米范围内的距离依赖性。
The rate and distance-dependence of association between surface-attached molecules may be determined by monitoring the motion of receptor-bearing spheres along ligand-coated surfaces in a flow chamber (Pierres et al., Proc. Natl. Acad. Sci. U.S.A. 95:9256-9261, 1998). Particle arrests reveal bond formation, and the particle-to-surface distance may be estimated from the ratio between the velocity and the wall shear rate. However, several problems are raised. First, data interpretation requires extensive computer simulations. Second, the relevance of standard results from fluid mechanics to micrometer-size particles separated from surfaces by nanometer distances is not fully demonstrated. Third, the wall shear rate must be known with high accuracy. Here we present a simple derivation of an algorithm permitting one to simulate the motion of spheres near a plane in shear flow. We check that theoretical predictions are consistent with the experimental dependence of motion on medium viscosity or particle size, and the requirement for equilibrium particle height distribution to follow Boltzman's law. The determination of the statistical relationship between particle velocity and acceleration allows one to derive the wall shear rate with 1-s(-1) accuracy and the Hamaker constant of interaction between the particle and the wall with a sensitivity better than 10(-21) J. It is demonstrated that the correlation between particle height and mean velocity during a time interval Deltat is maximal when Deltat is about 0.1-0.2 s for a particle of 1.4-mum radius. When the particle-to-surface distance ranges between 10 and 40 nm, the particle height distribution may be obtained with a standard deviation ranging between 8 and 25 nm, provided the average velocity during a 160-ms period of time is determined with 10% accuracy. It is concluded that the flow chamber allows one to detect the formation of individual bonds with a minimal lifetime of 40 ms in presence of a disruptive force of similar to5 pN and to assess the distance dependence within the tens of nanometer range.