Acid induced assembly of a reconstituted silk protein system

TL;DR

This study investigates how acid and salt affect the stability and aggregation of reconstituted silk proteins, revealing acid-specific effects on aggregate size and structure through scattering and mass spectrometry analyses.

Contribution

It demonstrates that acid induces specific aggregation behaviors in silk proteins that are not replicated by salt, providing insights into protein assembly mechanisms.

Findings

Acid causes aggregation at concentrations below 8 mM.

Salt does not induce aggregation at similar concentrations.

Acid modulates aggregate size and structure, unlike salt.

Abstract

Silk cocoons are reconstituted into an aqueous suspension, and protein stability is investigated by comparing the protein's response to hydrochloric acid and sodium chloride. Aggregation occurs at <8 mM hydrochloric acid that is not correlated to protein protonation, while sodium chloride over the same range of concentrations does not cause aggregation. We measure the structures present on the protein and aggregate lengthscales in these solutions using both optical and neutron scattering, while mass spectrometry techniques shed light on a possible mechanism for aggregate formation. We find that the introduction of acid modulates the aggregate size and pervaded volume of the protein, an effect that is not observed with salt.