Towards Microsecond Time-Resolved Cryo-Electron Microscopy - Ulrich Lorenz (EPFL)

Cryo-electron microscopy (cryo-EM) is rapidly becoming the dominant method in structural biology. However, with a time resolution of several milliseconds, it is frequently too slow to observe proteins in action, whose relevant dynamics typically occur on the microsecond timescale. This leaves our understanding of these nanoscale machines fundamentally incomplete. We have recently demonstrated a novel approach to time-resolved cryo-EM that is 1000 times faster, affording a time resolution of just a few microseconds. Our method involves melting a cryo sample in situ with a laser beam for a duration of tens of microseconds. This allows dynamics of the embedded particles to occur in liquid once a suitable stimulus is provided, for example by releasing a caged compound. While the dynamics occur, the heating laser is switched off at a well-defined point in time, causing the sample to rapidly recool, so that it vitrifies and traps the particles in their transient configurations, in which they can subsequently be imaged. Describes initial results that demonstrate the viability of the concept. Also discusses new avenues that our technique opens up for the study of the fast dynamics of proteins.