Proteins Fibrils Immobilized at SAMs

The assembly of proteins into higher-order structures provides new routes to nanostructured materials. Amyloid proteins, which assemble into fibers having thickness of ~10 nm and lengths of 1 mm, represent a model system that is well-suited to exploring this new class of nanostructures. In an early example, a yeast amyloid protein was genetically engineered to introduce a single cysteine residue, which was then used to label the protein with a biotin ligand. This engineered protein was allowed to self-assemble into fibers, which were then captured onto a self-assembled monolayer presenting streptavidin proteins (which have very high binding affinity for biotin ligands).

The figure shows two adjacent fibers running vertically in parallel which were imaged in liquid with a new atomic force microscope (AFM) that is optimized for this function. The liquid imaging provides far more structural detail-including the periodically spaced "bumps" (~70nm spacing) on each fiber-than does imaging of dry fibers on mica. The periodic structure may be characteristic of the fiber assembly from smaller units or represent a helical twist of a structure with rectangular cross section.

This work illustrates a strategy for the complementary engineering of proteins and materials and which will provide further control of the architectures of the protein scaffold.

by Seth B. Darling, Milan Mrksich
created 04/01