Abstract Cryo Electron Microscopy is a powerful Structural Biology technique, allowing the
elucidation of the three-dimensional structure of biological macromolecules. In particular, the
structural study of purified macromolecules–often referred as Single Particle Analysis (SPA)–
is normally performed through an iterative process that needs a first estimation of the three-
dimensional structure that is progressively refined using experimental data. It is well-known
the local optimisation nature of this refinement, so that the initial choice of this first structure …