Software Package for Electron Tomography
Protomo is a software package for image processing in transmission electron microscopy, with a special focus on tomography. The main applications are marker-free alignment of single-axis and dual-axis tilt series, 3D-reconstruction, and processing of volumetric data. The marker-free alignment is based on cross-correlation methods and projection matching. It also includes the refinement of geometric parameters of the tilt series. 3D reconstruction is implemented with weighted back-projection using general weighting functions that allow varying tilt angle increments. Processing of volumetric data includes the extraction of subvolumes from the computed tomograms, multivariate statistical methods applied to the subvolumes, classification and averaging of similar structures to produce images with higher signal-to-noise ratio. The procedures include options to compensate for missing data (missing wedge) in the tomograms. The software was originally developed for thin sections of insect flight muscle and paracrystalline protein arrays, but has since been successfully applied to various other specimens in cryo-electron tomography.