Ab initio methods: how they work

Dmitri Svergun

Principles of ab initio shape determination in small-angle scattering are explained and different approached proposed to reconstruct three-dimensional models out of one-dimensional scattering data are presented. The question of informational content in the small-angle scattering data is related to the possibility of ab initio shape analysis. Several methods are discussed including the angular envelope function based on spherical harmonics (Stuhrmann, 1970; Svergun & Stuhrmann, 1991; Svergun et al., 1996), and Monte-Carlo type approaches using models consisting of densely packed fixed beads (Chacon et al., 1998; Svergun, 1999; Walther, Cohen & Doniach, 2000) or condensation of a gas of dummy residues (Svergun, Petoukhov & Koch, 2001). The possibilities (and necessity) of the use of a priori information are discussed and advantages and limitations of ab initio methods are illustrated in practical applications.

Models used in ab initio methods

All the methods minimize Discrepancy[Data] + Penalty[Additional info]

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Date/time: Friday, 19 October 2012, 9:00