SINGLE MOLECULE 3D STRUCTURES DETERMINED BY INDIVIDUAL-PARTICLE ELECTRON TOMOGRAPHY

Macromolecules, such as proteins and nucleic acids, play essential roles in cellular functions through dynamic structural changes. Understanding these functions requires detailed characterization of structural dynamics. While techniques like X-ray crystallography and cryo-EM resolve high-resolution static structures, they struggle to capture low-resolution, flexible structures and the full distribution of conformations during chemical reactions. These limitations arise from averaging processes that enhance signal-to-noise ratio (SNR) but exclude flexible regions, distort resolution, and miss rare high-energy states. To address this, we developed individual-particle electron tomography (IPET), a method for determining 3D structures of single particles at low-to-intermediate resolution (up to 2 nm) without averaging. IPET reconstructs a detailed 3D density map by capturing images at multiple tilt angles, facilitating flexible model fitting and revealing unique particle structures. This method reveals unbiased structural distributions, enhancing the study of molecular dynamics, phase transitions, and structural alterations during chemical reactions and self-folding.