Biophysical-biochemical structural basis of self-assembly peptides, for nanobiotechnological applications

Artificial self-assemblies are known to fold into amyloid-like fibrillar structures with properties that are quite similar to those formed in vivo or in Nature. Therefore, these systems can give insights how to mimic Nature, and then develop it for applicable technologies. Moreover, using short synthetic peptides aids interpretation of structural details compared to the more complex and large naturally occurring amyloidogenic proteins/peptides. Two models of a-amino acids short peptides have been used here to mimic Nature. The first is based on the design KFFEAAAKKFE which has been previously characterised and shown to form an amyloid-like structure with cross-b architecture. It is utilised here for the first time to template silica from the precursor tetraexthoxy orthosilcate. Results reveal that variant peptides are able to form silica-nanowire suprastructures where Arg and Lys play a fundamental role in controlling silica nucleation, polymerisation and shaping the final suprastructure morphology. Furthermore, the silica-nanowires retained the cross-b core even after treating with harsh conditions, which point to their exceptional stability for multiple potential applications. The second model based on the design Ac-IHIHIQI-CONH2 has been previously used to mimic the natural carbonic anhydrase where it coordinated a metal ion (Zn+2) to catalyse a hydrolysing reaction of the substrate p-nitrophenyl acetate. This design is developed here and structurally characterised for the first time to reveal amyloid-like fibrils with cross-b hierarchy, and displays an excellent propensity to mimic carbonic anhydrase. Moreover, results indicated that this activity is governed by a few things: side chains-dependency where alternating His and Ile at position i, i+2 with Tyr at position 6 was the most active design while incorporating Glu at position 5 indicated the lower activity; Zn-dependency, protecting ends-dependency; and temperature and fibril age-dependency. The third model is based on tri- and hexa- peptides that have b-amino acids as a structural unit. These are decorated with functional groups and designed to self-assemble via hydrogen-bonding between amide groups at position i. i+2 into a helical secondary structure. They have been structurally characterised here for the first time, and results revealed that the designed peptides form different morphologies and structural variations depending on the position of the functional group and the sequence. Controlling the balance for all these designs may be adapted for specific properties to be efficient in multiple nanobiotechnological applications.