Non-destructive imaging of an individual protein

Abstract

The mode of action of proteins is to a large extent given by their ability to\nadopt different conformations. This is why imaging single biomolecules at\natomic resolution is one of the ultimate goals of biophysics and structural\nbiology. The existing protein database has emerged from X-ray crystallography,\nNMR or cryo-TEM investigations. However, these tools all require averaging over\na large number of proteins and thus over different conformations. This of\ncourse results in the loss of structural information. Likewise it has been\nshown that even the emergent X-FEL technique will not get away without\naveraging over a large quantity of molecules. Here we report the first\nrecordings of a protein at sub-nanometer resolution obtained from one\nindividual ferritin by means of low-energy electron holography. One single\nprotein could be imaged for an extended period of time without any sign of\nradiation damage. Since ferritin exhibits an iron core, the holographic\nreconstructions could also be cross-validated against TEM images of the very\nsame molecule by imaging the iron cluster inside the molecule while the protein\nshell is decomposed.\n