Geometric Frustration Controlled Morphogenesis of Protein Superstructures in Demospongiae

• Applicant: Dr. Igor Zlotnikov
• Subject Area: Polymeric and Biogenic Materials and Derived Composites ; Synthesis and Properties of Functional Materials
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 525814459

Sponges (Porifera) are a group of filter-feeding marine animals comprising ~10,000 living species. Whereas the majority of sponge bodies is made of an organic soft tissue, their mechanical stability and strength are achieved by mineralized skeletal elements, called spicules, reinforcing the organic tissue. Demosponges are a sponge class in which these spicules are made of amorphous glass. Astonishingly, despite the amorphous nature of the mineral phase, these spicules exhibit a variety of highly regular three-dimensional branched morphologies that are a paradigm example of symmetry in biological systems. During spicule formation, silica deposition is templated by axial filaments, which are composed of multifunctional enzymatically active proteins (silicateins) that are arranged in a mesoscopic crystal-like structure. Furthermore, the crystallographic branching of these protein crystals determines the highly regular morphology of the spicules that otherwise are made of an amorphous material. However, despite our basic understanding of this extraordinary biomineralization scheme, little is known about how the protein crystals form and about the driving forces that guide spicule morphogenesis in 3D. In this research we propose to perform a multi-scale study of the hybrid protein/mineral crystal in the axial filaments in various spicules of marine sponges and a consequent modelling of their formation, assuming that geometric frustration and the resulting mechanical stress drive their morphogenesis. The main objectives of the proposed research are to use various spicule morphologies in order to: (i) Follow the evolution of morphological and crystallographic properties of the hybrid protein/mineral crystalline superstructure during its growth. (ii) Follow the evolution of lattice defects and lattice strains in the hybrid protein/mineral crystal superstructure during its growth. (iii) Correlate between the measured evolution of morphological and lattice properties with the goal of establishing a comprehensive model for sponge spicule morphogenesis based on a spontaneous geometric frustration of periodically packed protein macromolecules.

• DFG Programme: Research Grants
• International Connection: Israel
• International Co-Applicant: Professor Dr. Efi Efrati