Single-and Multi-bead Coarse-grained Form Factors for SAXS Calculations
Abstract
Small-angle X-ray scattering (SAXS) is widely used to study proteins in solution, but atomistic scattering calculations are computationally demanding for large systems and many-body simulations. We develop two coarse-grained, polynomial form factor models for proteins: a one-bead-per-residue amino acid model and a Martini bead-based model. We systematically derive the form factors using the single-bead approximation with rotamer-library averaging to incorporate amino acid conformational variability. The models are evaluated against atomistic calculations, existing coarse-grained form factors, and experimental SAXS data from the Small Angle Scattering Biological Data Bank, SASBDB. Compared with a two-bead residue model, the amino acid bead model shows improved agreement to atomic scattering model, achieving nearatomistic accuracy. The Martini bead form factors perform comparably, or better, to existing Martini form factors. Comparisons with experimental SAXS profiles show that both models achieve similar agreement when hydration-shell contributions are included. These results demonstrate that systematically parameterised coarse-grained form factors provide accurate and efficient SAXS calculations, supporting their use in large-scale biomolecular modelling and simulation-based SAXS analysis. Coarse-graining also enables scattering calculations for highly dense interacting systems.
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BibTeX
@misc{vinterbladh2026singleand,
title = {{Single-and Multi-bead Coarse-grained Form Factors for SAXS Calculations}},
author = {Isabel Vinterbladh and Rémi Vuillemot and Sergei Grudinin and Mikael Lund},
howpublished = {HAL},
year = {2026},
month = jul,
url = {https://hal.science/hal-05839750v1},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Single-and Multi-bead Coarse-grained Form Factors for SAXS Calculations
AU - Isabel Vinterbladh
AU - Rémi Vuillemot
AU - Sergei Grudinin
AU - Mikael Lund
PY - 2026
DA - 2026/07/17
PB - HAL
UR - https://hal.science/hal-05839750v1
AB - Small-angle X-ray scattering (SAXS) is widely used to study proteins in solution, but atomistic scattering calculations are computationally demanding for large systems and many-body simulations. We develop two coarse-grained, polynomial form factor models for proteins: a one-bead-per-residue amino acid model and a Martini bead-based model. We systematically derive the form factors using the single-bead approximation with rotamer-library averaging to incorporate amino acid conformational variability. The models are evaluated against atomistic calculations, existing coarse-grained form factors, and experimental SAXS data from the Small Angle Scattering Biological Data Bank, SASBDB. Compared with a two-bead residue model, the amino acid bead model shows improved agreement to atomic scattering model, achieving nearatomistic accuracy. The Martini bead form factors perform comparably, or better, to existing Martini form factors. Comparisons with experimental SAXS profiles show that both models achieve similar agreement when hydration-shell contributions are included. These results demonstrate that systematically parameterised coarse-grained form factors provide accurate and efficient SAXS calculations, supporting their use in large-scale biomolecular modelling and simulation-based SAXS analysis. Coarse-graining also enables scattering calculations for highly dense interacting systems.
ER -