Proteins provide a diversity of chemical functionality and have dimensions at the nanometer scale, thus offering enormous potential to fabricate new nanostructured materials. Another important feature is that of self-assembly due to molecular interfaces evolved for biopartner interactions. The self-assembly of a protein system is exploited here for bottom-up fabrication of proteinaceous tubules and array scaffolds. Potential applications of this bio-nanomaterial include, using its RNA-binding capacity for developing new biosensors or delivery capsules.

 Lsm proteins spontaneously self-assemble in vivo into discrete rings of 6-8 protomers. We are fabricating nanostructures by exploiting variants of Lsmα (from thermophilic Methanobacterium thermoautotrophicum), a heptameric ring of 6.5 nm diameter. In our first approach, insertion of a histidine-rich segment at the N-terminus of each Lsmα amino acid sequence (H₆α) provides a chemical control to direct higher order assemblies of the rings. H₆α is observed to form ~420 kDa cage-like architectures via metal-mediated assembly.

 In a second approach, we are designing covalent attachments to fuse rings into tubules via axial (head-to-head, head-to-tail) interactions. Judicious placement of cysteine residues at ring surfaces allows disulphide conjugation that can be controlled by the redox state of the surroundings. It is important to know the physical shape and chemical stability of these new Lsm stacks. Contemporary techniques such as small angle x-ray scattering, transmission electron microscopy, and size exclusion chromatography are used to define the characteristics of these novel protein-based structures.