Imaging proteins at the truly single-molecule level

TL;DR

This paper demonstrates the direct imaging of individual proteins and complexes at sub-nanometer resolution using low-energy electron holography on graphene, revealing conformations without radiation damage.

Contribution

It introduces a novel method combining electrospray ion beam deposition and low-energy electron holography for imaging single proteins at high resolution.

Findings

Achieved sub-nanometer resolution images of individual proteins.

Successfully imaged protein complexes without averaging.

Demonstrated gentle, damage-free imaging technique.

Abstract

Imaging single proteins has been a long-standing ambition for advancing various fields in natural science, as for instance structural biology, biophysics and molecular nanotechnology. In particular, revealing the distinct conformations of an individual protein is of utmost importance. Here, we show the imaging of individual proteins and protein complexes by low-energy electron holography. Samples of individual proteins and protein complexes on ultraclean freestanding graphene were prepared by soft-landing electrospray ion beam deposition, which allows chemical- and conformational-specific selection and gentle deposition. Low-energy electrons do not induce radiation damage, which enables acquiring sub-nanometer resolution images of individual proteins (cytochrome C and bovine serum albumin) as well as of protein complexes (hemoglobin), which are not the result of an averaging process.