title: Volumetric restrictions in single particle 3DEM reconstruction.
abstract: 3D electron microsscopy aims at the reconstruction of density volumes corresponding to the electrostatic potential distribution of macro-molecules. There are many factors limiting the resolution achievable when this technique is applied to biological macromolecules: microscope imperfections, molecule flexibility, lack of projections from certain directions, unknown angular distribution, noise, etc. In this communication we explore the quality gain in the reconstruction by including a priori knowledge such as particle symmetry, occupied volume, known surface relief, density nonnegativity and similarity to a known volume in order to improve the quality of the reconstruction. If the reconstruction is represented as a series expansion, such constraints can be expressed by set of equations that the expansion coefficients must satisfy. In this work, these equation sets are specified and combined in a novel way with the ART + blobs reconstruction algorithm. The effect of each one on the reconstruction of a realistic phantom is explored. Finally, the application of these restrictions to 3D reconstructions from experimental data are studied.
authors.affiliation: Unidad de Biocomputación, Centro Nacional de Biotecnología (CSIC), Campus Universidad Autónoma s/n, 28049 Cantoblanco, Madrid, Spain.
authors.forename: C O S
authors.initials: CO
authors.lastname: Sorzano
authors.forename: J A
authors.initials: JA
authors.lastname: Velázquez-Muriel
authors.forename: R
authors.initials: R
authors.lastname: Marabini
authors.forename: G T
authors.initials: GT
authors.lastname: Herman
authors.forename: J M
authors.initials: JM
authors.lastname: Carazo