Atomic resolution imaging by scanning probe and electron microscopy

This event is hosted by Sarah Wilson (sarah.wilson@york.ac.uk).

Electrospray ion beam deposition (ESIBD), the deposition of intact molecular ions created by electrospray ionisation onto solid surfaces in vacuum, has been introduced in our lab as a tool for the handling of large and complex, usually non-volatile molecules. Initially, the high-resolution single-molecule imaging by scanning probe microscopy (SPM) has been the major application. Here ESIBD
proved successful in the investigation of structure, conformation, and properties of proteins, peptides, saccharides, and synthetic
molecules.

ESIBD's high level of control over molecular ion beam and environment in opens new avenues in molecular imaging. Native ESI enables the chemically selective enrichment of folded proteins and proteins complexes for structural investigation by electron microscopy imaging  (cryoEM), and low energy electron holography (LEEH). 

Optimised conditions for native deposition promote imaging of individual proteins at a resolution sufficient for the construction of atomic models from cryoEM data. The structure obtained from cryoEM after embedding the landed proteins in ice grown from the gas phase shows a fold and subunit arrangement which is remarkably similar to the solution structure. Small conformational changes cause differences, mostly at the protein surface and interfaces. We find the closing of cavities and crevices’ due to self-interaction in absence of water, a change reversed in MD simulations to find the native structure again.