The dynamics of particles with ligand-receptor contacts

Synopsis

Particles that stick to each other via ligand-receptor interactions are common in biology, such as white blood cells, virus particles, cargo in the nuclear pore complex, etc, and they are also useful in materials science, where coating colloids with single-stranded DNA creates particles with programmable interactions. In these systems, the ligand-receptor interactions not only hold particles together, but also influence their dynamics. How do such particles move? Do they “roll” on each others’ surfaces, as is commonly thought? Or could they slide? And does it matter? In this talk I will introduce our modelling efforts and experiments aimed at understanding the coarse-grained dynamics of particles with ligand-receptor interactions, and show these interactions change the particles' effective diffusion by orders of magnitude. I will argue that in some cases, particles should preferentially roll. Then, I will describe our attempts to understand the statistical mechanics of particles that are constrained to roll, which will lead us to explore the geometry of nonholonomic constraints, and to the challenge of incorporating such constraints into stochastic systems.