Interfacial Crystallization and Supramolecular Self-Assembly of Spider Silk Inspired Protein at the Water-Air Interface

Macromolecular assembly into complex morphologies and architectural shapes is an area of fundamental research and technological innovation. In this work, we investigate the self-assembly process of recombinantly produced protein inspired by spider silk (spidroin). To elucidate the first steps of the assembly process, we examined highly concentrated and viscous pendant droplets of this protein in air. We show how the protein self-assembles and crystallizes at the water-air interface into a relatively thick and highly elastic skin. Using time-resolved in situ synchrotron x-ray scattering measurements during the drying process, we showed that the skin evolved to contain a high beta-sheet amount over time. We also found that beta-sheet formation strongly depended on protein concentration and relative humidity. These had a strong influence not only on the amount, but also on the ordering of these structures during the beta-sheet formation process. We also showed how the skin around pendant droplets can serve as a reservoir for attaining liquid-liquid phase separation and coacervation from the dilute protein solution. Essentially, this study shows a new assembly route which could be optimized for the synthesis of new materials from a dilute protein solution and determine the properties of the final products.

Automated summary

This study investigates the self-assembly process of recombinant proteins inspired by spider silk, showing the formation of an elastic skin at the water-air interface with high concentration of beta-sheets over time. The beta-sheet formation strongly depends on protein concentration and relative humidity, influencing both the amount and ordering of these structures during the process.