Coiled‐Coil Peptide Beacon: A Tunable Conformational Switch for Protein Detection

Fortified Coiled Coils: Enhancing Mechanical Stability with Lactam or Metal Staples

Coiled coils (CCs) are powerful supramolecular building blocks for biomimetic materials, increasingly used for their mechanical properties. Here, we introduce helix-inducing macrocyclic constraints, so-called staples, to tune thermodynamic and mechanical stability of CCs. We show that thermodynamic stabilization of CCs against helix uncoiling primarily depends on the number of staples, whereas staple positioning controls CC mechanical stability. Inserting a covalent lactam staple at one key force application point significantly increases the barrier to force-induced CC dissociation and reduces structural deformity. A reversible His-Ni2+ -His metal staple also increases CC stability, but ruptures upon mechanical loading to allow helix uncoiling. Staple type, position and number are key design parameters in using helical macrocyclic templates for fine-tuning CC properties in emerging biomaterials.

A Peptide-PNA Hybrid Beacon for Sensitive Detection of Protein Biomarkers in Biological Fluids

Specific and rapid detection of proteins in biological fluids poses a challenging problem. In biological fluids, many proteins are present at low concentrations, requiring high affinity and specificity of the beacon-protein interaction. We report the design of a peptide-PNA hybrid beacon that exploits the dimeric nature of a target protein, S100B, a biomarker for brain trauma, to enhance binding affinity and specificity. The complementary base-pairing of the PNA bases brings the two arms of the beacon, one carrying an Alexa tag and the other carrying a Dabcyl moiety, into proximity, thus quenching Alexa fluorescence. Each of the arms carries a sequence that binds to one of the subunits. Binding to the target separates the quencher from the probe lifting the quenching of fluorescence. Enhanced affinity and specificity resulting from simultaneously binding to two sites allowed specific detection of S100B at low-nanomolar concentrations in the presence of serum. The design can be easily adapted for the detection of proteins containing multiple binding sites and could prove useful for rapid and sensitive biomarker detection.