1. Single molecule imaging of T cell receptor conformation dynamics
To understand the molecular mechanism of TCR ligand discrimination and conformation dynamics, we apply single molecule fluorescence resonance energy transfer (smFRET) to measure the intermolecular TCR-pMHC bond distance and intramolecular TCR-CD3 conformation with a spatiotemporal resolution of ~1 Å and ~10 ms at the membrane of a live primary T cell. This experiment uncover how TCRs discriminate structurally similar peptides by forming TCR-pMHC bonds of different conformations, which in turn control the accessibility of CD3 ITAMs for signal initiation, thus explaining the molecular mechanism of TCR ligand discrimination.