Emergence of amyloidic fibrillation in 2D-ordered Langmuir-Blodgett protein multilayers upon heating

Langmuir-Blodgett protein nanofilms can serve as templates for nucleation and growth of protein crystals. This functionality can be enhanced by thermal annealing. While surface ordering of the multilayered nanofilms and an improvement of the correlation between the layers during thermal annealing have been revealed by atomic force microscopy and grazing-incidence small-angle X-ray scattering, information on the structure developing in the bulk of nanofilms is lacking. In this paper, we report on scanning X-ray nanodiffraction experiments of penicillin-G-acylase multilayers deposited on Si3N4 membranes and annealed at 150 °C. While the annealed multilayer has remained mostly featureless, we observe locally globular aggregates and filamentous spherulites based on nanofibrillar subunits with cross-β amyloidic motifs.