Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE, USA.
Biophys J. 2013 Feb 19;104(4):863-72. doi: 10.1016/j.bpj.2012.12.014.
We calculate the displacement of a single spherical particle from the minimum of a harmonic well positioned near a plane wall and immersed in a uniform flow. A failure to account for the fluctuations in particle position orthogonal to the plane (leading to fluctuations in hydrodynamic drag) results in large discrepancies, with the naive displacement calculated by assuming no fluctuations in the balance of forces. The chief criterion for neglecting such fluctuations is that the stiffness of the harmonic potential exceeds the thermal stresses on the particle by at least two orders of magnitude. For micrometer-diameter particles typically employed in force spectroscopy of DNA, macromolecules, and molecular motors, this can lead to errors of up to 100% in the measured properties. The Supporting Material to the article provides an implementation of this model intended to fit experimental measurements for the stiffness of the harmonic potential constraining the particle.
我们计算了一个位于平面壁附近的简谐势阱中的单个球形粒子的位移，该粒子处于均匀流中。如果不考虑粒子在垂直于平面的位置上的波动（导致水动力阻力的波动），则会导致很大的差异，因为通过假设力平衡中没有波动来计算的简单位移。忽略这种波动的主要标准是谐势能的刚度至少超过粒子上的热应力两个数量级。对于通常用于 DNA、大分子和分子马达的力谱学中的微米级直径的粒子，这可能导致测量性质的误差高达 100%。文章的支持材料提供了这种模型的实现，旨在拟合限制粒子的谐势能的刚度的实验测量。
