A Multimodal Lens on Protein Assembly: From Silk to Seeds

Protein-based materials rely on controlled assembly across multiple length
scales. Key organisational features often emerge before macroscopic fibres or
gels form. Yet the pathways linking molecular organisation to material formation
remain poorly resolved. This is partly because structural evolution across length
scales is rarely measured concurrently within the same sample.
This thesis examines protein assembly as a multiscale, pathway-dependent
process. Silk proteins serve as the primary model system, as they form highly
organised fibres under mild aqueous conditions. Yellow pea proteins provide a
complementary multicomponent case in which processing history and co-existing
components influence assembly.
The work focuses on the solution and pre-gelation states. In reconstituted
silk fibroin from Bombyx mori, time-resolved multimodal measurements are used.
Neutron scattering is combined with ultraviolet and fluorescence spectroscopy
to follow structural evolution from molecular to mesoscopic scales within the
same samples. These measurements reveal structured intermediate states prior
to extensive β-sheet formation. The accessibility and persistence of these
intermediates depend on the assembly environment, showing that processing
conditions select assembly pathways rather than simply triggering final states.
Native and recombinant cylindriform spidroins are examined as a simpler
spider silk system. Small-angle X-ray scattering and ensemble modelling reveal
elongated, modular solution architectures, linking solution-state organisation to
its multi-domain architecture. Recombinant constructs further demonstrate the
sensitivity of assembly to junction stability and solution context.
In pea protein–starch mixtures, contrast-variation neutron scattering shows that
proteins and residual starch are largely independent in solution. Thermal treatment
induces co-assembly in a processing-history-dependent manner.
Together, these studies show that protein-based material formation is shaped
upstream of macroscopic assembly. Resolving organisation across length scales
highlights the roles of pre-organisation, pathway-dependent intermediates,
and solvent participation. The multimodal and scattering-based approaches
established here provide a general strategy for investigating hierarchical protein
assembly in both silk-like and food-relevant systems.