Small-molecule sensing and capture by de novo protein receptors followed by fluorescence spectroscopy and mass spectrometry.

Proteins already have an incredibly versatile array of structures and functions in nature and our understanding of them has enabled the design of new structures. De novo protein design has enabled the creation of proteins for use in industrial biotechnologies or engineering, free of the selective pressures found in nature. One protein fold, coiled coils, are one such example of successful de novo design targets. Their structure can be described parametrically which has allowed for computational design, and the discovery of new oligomeric states as of yet unseen in nature. Higher order coiled coils possess a continuous pore running through their structure, named a-helical barrels (aHBs). These aHBs have been shown to be incredibly thermostable and tolerable of several mutations in the lumen orientated residues. aHBs have already been exploited to perform simple chemical modifications, full catalytic cycles and the capturing of small-molecules. The latter of which is only just beginning to be explored.

At the current understanding, lipids are the most attractive targets for aHBs. The lipidome can be used to identify many diseases through the use of characteristic biomarkers including cancers, obesity, Alzheimer's disease and diabetes. Treated lipids samples are often analysed through the use of mass spectroscopy coupled with a chromatographic separation method. However, such metabolomic studies can be intensive, requiring complex instrumentation with a large perquisite of knowledge to analyse the results. Here, we aim to identify specific aHB:ligand binding partners in complex fluids in order to produce simple to read, quantitative colorimetric diagnostic tests through the use of aHBs arrays in tandem with environment-sensitive dyes. aHBs by their nature attract hydrophobic compounds with some specificity on compound size. Enhancing our understanding of how the general binding occurs would further enable peptide design with unique binding-partner types in mind.

The differential sensing of particular macromolecules can enable the fingerprinting of different conditions and the presence, or lack thereof, of unique compounds. The result would be a hyper-stable, mutable and easily readable diagnostic array with applications in industry and medicine.