Figure 4.

Binding dynamics between IgG-coated microparticles and cells. (A) Thermal motion of an optically trapped IgG-coated particle that binds stepwise to the membrane of a macrophage (see orange arrows and insets), which become visible in the plots below, is shown. (B) Autocorrelation analysis of the particle position fluctuations allows determining the binding force constant κ_tot(t). The binding force constant increases stepwise as the particle binds to the cell. A second abrupt increase a few seconds after the initial binding to the cell indicates a further bond formation between particle and cell membrane. (C) Stepwise change of the viscous drag γ_tot(t) experienced by the particle upon binding is shown. To see this figure in color, go online.