title: SCT: a suite of programs for comparing atomistic models with small-angle scattering data.
abstract: Small-angle X-ray and neutron scattering techniques characterize proteins in solution and complement high-resolution structural studies. They are of particular utility when large proteins cannot be crystallized or when the structure is altered by solution conditions. Atomistic models of the averaged structure can be generated through constrained modelling, a technique in which known domain or subunit structures are combined with linker models to produce candidate global conformations. By randomizing the configuration adopted by the different elements of the model, thousands of candidate structures are produced. Next, theoretical scattering curves are generated for each model for trial-and-error fits to the experimental data. From these, a small family of best-fit models is identified. In order to facilitate both the computation of theoretical scattering curves from atomistic models and their comparison with experiment, theSCTsuite of tools was developed.SCTalso includes programs that provide sequence-based estimates of protein volume (either incorporating hydration or not) and add a hydration layer to models for X-ray scattering modelling. The originalSCTsoftware, written in Fortran, resulted in the first atomistic scattering structures to be deposited in the Protein Data Bank, and 77 structures for antibodies, complement proteins and anionic oligosaccharides were determined between 1998 and 2014. For the first time, this software is publicly available, alongside an easier-to-use reimplementation of the same algorithms in Python. Both versions ofSCThave been released as open-source software under the Apache 2 license and are available for download from https://github.com/dww100/sct.
authors.affiliation: Department of Structural and Molecular Biology, Division of Biosciences, University College London , Darwin Building, Gower Street, London WC1E 6BT, UK.
authors.forename: David W
authors.initials: DW
authors.lastname: Wright
authors.affiliation: Department of Structural and Molecular Biology, Division of Biosciences, University College London , Darwin Building, Gower Street, London WC1E 6BT, UK.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Perkins
keywords: X-ray scattering; analytical ultracentrifugation; constrained modelling; hydration shells; neutron scattering