The function of a protein is determined by its structure. Although natural proteins are highly versatile, creating proteins with controlled structures, assemblies, and recognition abilities can be challenging. Computational protein design from scratch is a powerful tool that can be used to develop protein systems with unique functions. This article presents experimental studies of one protein system designed using computational methods to bind a wide range of lanthanides and two peptide systems designed as building blocks to study the formation of polymeric peptide materials. The first example of the de novo designed protein is named ScCC-Ln, which has been designed to bind trivalent ions of lanthanides. ScCC-Ln is a single-chain protein that can fold into a four-helix coiled-coil structure with the binding site located in the hydrophobic core. To monitor the binding of lanthanides, a tryptophan residue has been designed adjacent to the binding site which facilitates energy transfer effect. The binding of 14 lanthanides and associated pH dependence have been investigated. The study of lanthanides in this computationally designed de novo protein can help in understanding the affinity and selectivity of lanthanide binding within protein systems.

We consider two types of designed peptides that can form polymeric materials through covalent linkage. One forms homotetrameric coiled-coil bundles and is designed to be covalently linked by a thiol-maleimide click reaction. We study the influence of hydrophobic modifications at the terminal regions of the bundle and potential impact on the physical properties of covalently linked polymeric rods. Secondly, we consider a designed heterotetrameric bundle comprising two distinct peptides, A and B, having complementary charges. All ionizable residues from Chain A are positive and those on Chain B are negative. These two peptides are designed to form heterotetrameric bundles when they are simultaneously present in the solution. We studied the conditions of forming the A2B2 four-helix bundle by using circular dichroism (CD) spectroscopy.