Determination of the illuminating angle and defocus spread in transmission electron microscopy

Electron Source Brightness and Illumination Semi-Angle Distribution Measurement in a Transmission Electron Microscope

The electron source brightness is an important parameter of an electron microscope. Reliable and easy brightness measurement routes are not easily found. A determination method for the illumination semi-angle distribution in transmission electron microscopy is even less well documented. Herein, we report a facile measurement route for both entities and demonstrate it on a state-of-the-art instrument. The reduced axial brightness of the FEI X-FEG with a monochromator was determined to be larger than 108 A/(m2 sr V).

Dynamical electron scattering from negatively stained protein microcrystals

Multislice n-beam dynamical calculations have been carried out at 20 and 15.6 A resolution to simulate the electron scattering from a negatively-stained protein microcrystal using a model based on the crystal structure of E. coli matrix porin. Images at t = 100 A, i.e. the thickness of reconstituted vesicle preparation, correspond to the projected potential of the kinematical structure. The kinematical model is valid at least to t = 500 A, beyond which the projected-image symmetry does not correspond to the actual structure. If a crystallographic residual limit R = 0.20 is imposed, the electron diffraction intensity data correspond to the kinematical data up to t = 700 and 1000 A, respectively, for 15.6 and 20 A resolution.