The controlled organization of inorganic materials into multi-dimensional addressable arrays is the foundation for logic and memory devices, as well as other nonlinear optical and sensing devices. Many of these devices are currently fabricated using lithographic patterning processes that have progressively developed toward greater integration densities and smaller sizes. At submicron scales, however, conventional lithographic processes are approaching their practical and theoretical limits. At scales below 100 nm, ion and electron beam lithography becomes prohibitively expensive and time consuming, and more importantly, at these scales, quantum effects fundamentally change the properties of devices.
Nanoscale templates for constrained synthesis, in-situ deposition, or direct patterning of nanometer-scale inorganic arrays are being developed using both artificial and natural materials. The present invention provides chaperonin polypeptides that are modified to include N-terminal and C-terminal ends relocated from the central pore region to various different positions in the polypeptide that are located on the exterior of the folded modified chaperonin polypeptide. In the modified chaperonin polypeptide, the naturally occurring N-terminal and C-terminal ends are joined together directly or with an intervening linker peptide sequence. The relocated N-terminal or C-terminal ends can be covalently joined to, or bound with, another molecule such as a nucleic acid molecule, a lipid, a carbohydrate, a second polypeptide, or a nanoparticle. The modified chaperonin polypeptides can assemble into double-ringed chaperonin structures. Further, the chaperonin structures can organize into higher order structures such as nanofilaments or nanoarrays, which can be used to produce nanodevices and nanocoatings.
A number of protein complexes have been developed as nanoscale templates. These templates can be functionalized by genetic modification to add chemically reactive sites that bind inorganic materials. For example, chaperonin complexes can be functionalized to bind soft metals. Protein complexes can also be modified to include peptide sequences having desirable binding or catalytic functions. These protein complexes comprise subunits having inserted peptide sequences. However, the mutant sub-units may fail to fold, assemble into complexes, or organize into higher-order structures. Furthermore, insertion as a loop may render the peptide sequence inactive, and fusion to one of the native termini may not provide sufficient surface accessibility. To overcome this challenge, circular permutation has been used to join peptide sequences within a protein template. Circular permutation is a reordering of the polypeptide chain such that the original N- and C-terminal ends are joined and new termini are created elsewhere in the protein. New peptide sequences can be joined to either of the new termini without perturbing subunit assembly.