Proteins mediate all cellular functions from cell division, metabolism, and transport to programmable cell death. Studying proteins
and their structure-dynamics-function relationship is of paramount importance to understand life and to fight disease. The past
decade has witnessed the emergence of revolutionary interferometric scattering (iSCAT) microscopy, which enables optical singlemolecule
protein imaging, free from laborious fluorescent labeling and chemical tethering. iSCAT paves the way to the long-sought
label-free interrogation of single protein molecules. However, this new approach is fundamentally blind to protein conformational
dynamics. In ProAct we aim to endow iSCAT microscopy with the ability to look behind the curtain of protein conformational dynamics
and thus fulfill the quest for the least invasive and most informative technology to study proteins.
We hypothesize that protein physical properties will be encoded in the optical signal if the molecule is engaged in a periodic motion by
means of interaction with an inhomogeneous electric field. Under such conditions, a protein molecule experiences dielectrophoretic
(DEP) force. The magnitude of this force depends on the protein hydrodynamic radius and dipole moment, which are sensitive to
molecular conformation. The synergy of actuating a single protein molecule using dielectrophoresis while simultaneously optically
monitoring its physical properties using iSCAT microscopy, will yield a radically novel method for label-free interrogation of protein
dynamics.
We expect that the outcomes of this project will enormously simplify the study of protein dynamics, protein-ligand interactions and protein-protein
interactions by eliminating the need for an optimal labeling strategy. Moreover, ProAct will deepen the understanding of protein
dielectrophoresis and elevate iSCAT imaging to the next level for observing molecular dynamics.