A single-molecule tracking/imaging technique with semiconductor quantum dot (QD) nanosensors conjugated with appropriate peptides or antibodies is appealing for probing cellular dynamic events in living cells. We developed a 2D analysis of single-molecule trajectories using normalized variance versus mean square displacement (MSD) to provide high-quality statistics sampled by nanosensors while preserving single-molecule sensitivity. This plot can be more informative than MSD alone to reflect the diffusive dynamics of a protein in its cellular environment. We illustrate the performance of this technique with selected examples, which are designed to expose the functionalities and importance in live cells. Our findings suggest that biomolecule-conjugated QD nanosensors can be used to reveal interactions, stoichiometries, and conformations of proteins, and provide an understanding of the mode of the interaction, stable states, and dynamical pathways of biomolecules in live cells.
Part of the book: Nonmagnetic and Magnetic Quantum Dots