Diffraction from the beta-sheet crystallites in spider silk

TL;DR

This paper presents a quantitative model for analyzing wide angle X-ray scattering from spider silk's beta-sheet crystallites, enabling extraction of structural parameters and confirming the validity of single crystallite scattering assumptions.

Contribution

The study introduces a comprehensive scattering model that accounts for correlations and parameters of beta-sheet crystallites in spider silk, validated against experimental data.

Findings

Inter-crystallite effects are negligible at observed mosaicity levels.

The model accurately fits experimental scattering intensities.

Single crystallite scattering assumptions are justified in this context.

Abstract

We analyze the wide angle x-ray scattering from oriented spider silk fibers in terms of a quantitative scattering model, including both structural and statistical parameters of the $\beta$-sheet crystallites of spider silk in the amorphous matrix. The model is based on kinematic scattering theory and allows for rather general correlations of the positional and orientational degrees of freedom, including the crystallite's size, composition and dimension of the unit cell. The model is evaluated numerically and compared to experimental scattering intensities allowing us to extract the geometric and statistical parameters. We show explicitly that for the experimentally found mosaicity (width of the orientational distribution) inter-crystallite effects are negligible and the data can be analyzed in terms of single crystallite scattering, as is usually assumed in the literature.