Non-destructive imaging of an individual protein

TL;DR

This paper demonstrates non-destructive, high-resolution imaging of a single protein using low-energy electron holography, allowing detailed structural analysis without averaging or radiation damage.

Contribution

It presents the first sub-nanometer resolution images of an individual protein without damage, surpassing traditional averaging methods in structural biology.

Findings

Single protein imaged at sub-nanometer resolution

Imaging performed without radiation damage

Cross-validation with TEM images of iron core

Abstract

The mode of action of proteins is to a large extent given by their ability to adopt different conformations. This is why imaging single biomolecules at atomic resolution is one of the ultimate goals of biophysics and structural biology. The existing protein database has emerged from X-ray crystallography, NMR or cryo-TEM investigations. However, these tools all require averaging over a large number of proteins and thus over different conformations. This of course results in the loss of structural information. Likewise it has been shown that even the emergent X-FEL technique will not get away without averaging over a large quantity of molecules. Here we report the first recordings of a protein at sub-nanometer resolution obtained from one individual ferritin by means of low-energy electron holography. One single protein could be imaged for an extended period of time without any sign of radiation damage. Since ferritin exhibits an iron core, the holographic reconstructions could also be cross-validated against TEM images of the very same molecule by imaging the iron cluster inside the molecule while the protein shell is decomposed.