Modular Design for Proteins Assembling into Antifouling Coatings: Case of Gold Surfaces.

We analyze modularity for a B-M-E triblock protein designed to self-assemble into antifouling coatings. Previously, we have shown that the design performs well on silica surfaces when B is taken to be a silica-binding peptide, M is a thermostable trimer domain, and E is the uncharged elastin-like polypeptide (ELP), E = (GSGVP)40. Here, we demonstrate that we can modulate the nature of the substrate on which the coatings form by choosing different solid-binding peptides as binding domain B and that we can modulate antifouling properties by choosing a different hydrophilic block E. Specifically, to arrive at antifouling coatings for gold surfaces, as binding block B we use the gold-binding peptide GBP1 (with the sequence MHGKTQATSGTIQS), while we replace the antifouling blocks E by zwitterionic ELPs of different lengths, EZn = (GDGVP-GKGVP)n/2, with n = 20, 40, or 80. We find that even the B-M-E proteins with the shortest E blocks make coatings on gold surfaces with excellent antifouling against 1% human serum (HS) and reasonable antifouling against 10% HS. This suggests that the B-M-E triblock protein can be easily adapted to form antifouling coatings on any substrate for which solid-binding peptide sequences are available.

De novo designed ice-binding proteins from twist-constrained helices.

Attaining molecular-level control over solidification processes is a crucial aspect of materials science. To control ice formation, organisms have evolved bewildering arrays of ice-binding proteins (IBPs), but these have poorly understood structure-activity relationships. We propose that reverse engineering using de novo computational protein design can shed light on structure-activity relationships of IBPs. We hypothesized that the model alpha-helical winter flounder antifreeze protein uses an unusual undertwisting of its alpha-helix to align its putative ice-binding threonine residues in exactly the same direction. We test this hypothesis by designing a series of straight three-helix bundles with an ice-binding helix projecting threonines and two supporting helices constraining the twist of the ice-binding helix. Our findings show that ice-recrystallization inhibition by the designed proteins increases with the degree of designed undertwisting, thus validating our hypothesis, and opening up avenues for the computational design of IBPs.

Design of Polypeptides Self-Assembling into Antifouling Coatings: Exploiting Multivalency.

We propose to exploit multivalent binding of solid-binding peptides (SBPs) for the physical attachment of antifouling polypeptide brushes on solid surfaces. Using a silica-binding peptide as a model SBP, we find that both tandem-repeated SBPs and SBPs repeated in branched architectures implemented via a multimerization domain work very well to improve the binding strength of polypeptide brushes, as compared to earlier designs with a single SBP. At the same time, for many of the designed sequences, either the solubility or the yield of recombinant production is low. For a single design, with the domain structure B-M-E, both solubility and yield of recombinant production were high. In this design, B is a silica-binding peptide, M is a highly thermostable, de novo-designed trimerization domain, and E is a hydrophilic elastin-like polypeptide. We show that the B-M-E triblock polypeptide rapidly assembles into highly stable polypeptide brushes on silica surfaces, with excellent antifouling properties against high concentrations of serum albumin. Given that SBPs attaching to a wide range of materials have been identified, the B-M-E triblock design provides a template for the development of polypeptides for coating many other materials such as metals or plastics.

Flexible and disposable gold nanoparticles-N-doped carbon-modified electrochemical sensor for simultaneous detection of dopamine and uric acid.

Catalytic and electrocatalytic applications of supported metal nanoparticles are hindered due to an aggregation of metal nanoparticles and catalytic leaching under harsh operations. Hence, stable and leaching free catalysts with high surface area are extremely desirable but also challenging. Here we report a gold nanoparticles-hosted mesoporous nitrogen doped carbon matrix, which is prepared using bovine serum albumin (BSA) through calcination. BSA plays three roles in this process as a reducing agent, capping agent and carbon precursor, hence the protocol exhibits economic and sustainable. Gold nanoparticles at N-doped BSA carbon (AuNPs@NBSAC)-modified three-electrode strip-based flexible sensor system has been developed, which displayed effective, sensitive and selective for simultaneous detection of uric acid (UA) and dopamine (DA). The AuNPs@NBSAC-modified sensor showed an excellent response toward DA with a linear response throughout the concentration range from 1 to 50 µM and a detection limit of 0.05 µM. It also exhibited an excellent response toward UA, with a wide detection range from 5 to 200 µM as well as a detection limit of 0.1 µM. The findings suggest that the AuNPs@NBSAC nanohybrid reveals promising applications and can be considered as potential electrode materials for development of electrochemical biosensors.