Superresolution Inter-Surface Interaction Energy Mapping Using Particle Tracking Microscopy (Pte)

In biology, binding reactions taking place between apposing surfaces, in contrast to reactions in solution, are controlling a plethora of critical processes including cell adhesion and motility, immunological signaling, neurotransmission etc. However he techniques developed to quantitatively characterize interfacial reactions (e.g. the surface force apparatus, surface plasmon resonance and quartz crystal microbalance) are either not at all amenable to imaging or have at best a resolution of tens of micrometers. Here, we monitored the transient interaction of diffusing particles with a surface to measure quantitatively and under equilibrium conditions, inter-surface on-rates, off-rates and energies for binding reactions (1, 2). These interactions could then be laterally resolved to produce an energy map with sub-diffraction-limited resolution. This novel method was termed Particle Tracking Microscopy. References: 1. Kunding, A.H., M.W. Mortensen, S.M. Christensen, V.K. Bhatia, I. Makarov, et al. 2011. Intermembrane Docking Reactions are Regulated by Membrane Curvature. Biophysical Journal. 101: 2693-2703. 2. Christensen, S.M., M.W. Mortensen, and D.G. Stamou. 2011. Single vesicle assaying of SNARE-synaptotagmin-driven fusion reveals fast and slow modes of both docking and fusion and intrasample heterogeneity. Biophysical Journal. 100: 957-967.