polymer_lipid_particle

Definition
----------

This model calculates the scattering from polymer lipid particles (or polymer nanodiscs)s.
Default parameters corresponds to styrene maleic acid (SMA) (2:1) and DMPC.
The model is a circular polydisperse nanodisc model with molecular parametrization through the number of lipids and molecular volumes.
A log normal distribution in the number of lipids was used - directly coded in the model, not through sasview's build-in polydispersity.
b values are the number of electrons, and should correspond to the relevant molecules (default is SMA(2:1) and DMPC), but the b values *should not be fitted*
The ED (or SLD) values are calculated in the model as ED = b/(molecular volume).
The ED is the solvent electron density. Should be adjusted to match buffer (default 1xPBS), but *should not be fitted*.
The model is not on absolute scale, so the form factor is normalized to 1 and the scaling should be set to I(0)

References:
----------
Tang et al (2026) "Structure and stability of styrene-maleic acid lipid particles: the role of polymer-lipid ratio", Journal of Colloid and Interface Science 724: 141054. https://doi.org/10.1016/j.jcis.2026.141054.
Larsen et al (2027) "State-of-the-art analysis of SAXS data of high-density lipoprotein, nanodiscs or polymer-lipid particles – a practical guide" unpublished.

Authorship and Verification
----------------------------

* **Author:** Andreas Haahr Larsen **Date:** 6 November 2026