Hindered Mobility of a Rigid Sphere Near a Wall

Size Dependence of Protein Diffusion Very Close to Membrane Surfaces: Measurement by Total Internal Reflection with Fluorescence Correlation Spectroscopy

“…[33][34][35] The theoretical predictions have been experimentally verified, in part, for large colloidal particles. [36][37][38][39][40][41][42][43] In the work described herein, the diffusion coefficients of nine fluorescently labeled antibody fragments, antibodies, and antibody complexes (with hydrodynamic radii ranging from 3 to 24 nm) adjacent to planar supported model membranes were measured by using TIR-FCS. The results show that the local diffusion coefficient decreases with the hydrodynamic radius, over and above that predicted by the Stokes-Einstein equation describing diffusion in bulk solution, and in a manner consistent with theoretical predictions according to hydrodynamic theories describing particle motions next to walls.…”

A new approach for analyzing particle motion near an interface using total internal reflection microscopy

“…The authors calculated the absolute separation distance of the particle from the surface assuming Brenner's lubrication theory to be valid. Using the same TIRM technique, Pagac et al [7] measured the hindered mobility of 7 to 15 µm diameter of microscopic spheres near an interface (0-500 nm). The mobility was determined by applying a known radiation pressure force using a focused laser beam to a Brownian particle several hundred times and measuring the resulting ensemble-average change in the particle/plate separation distance as a function of time.…”

“…For example, in the sedimentation experiments of Walz and Suresh [8], data was only collected at large separations from the plate where the only significant force was gravity. In the work of Pagac et al [7], the particle mobility was obtained only at a single point, namely the minimum in the local potential energy profile. Obtaining results at different separations required changing either the amount of radiation pressure applied to the particle (which moved it to a different equilibrium position) or the solution ionic strength (which altered the magnitude of the electrostatic repulsive force keeping the particle elevated).…”

Shear-Dependent Boundary Slip in an Aqueous Newtonian Liquid

“…"Free" systems, such as a sphere approaching a wall under the action of a negative buoyancy force [33,34] or the approach of two colloidal particles, are unlikely to exhibit boundary slip as the drainage force acts to reduce the relative velocity of the surfaces considerably as the surface separation decreases. We have shown that low relative velocities will not result in boundary slip.…”