Applications for Constrained and functionalised Peptides and Proteins Using Organic Crosslinkers

The key to successful drug discovery lies in the perfect balance between target accessibility and affinity. Small molecules have the advantage of easily penetrating into the cell but may lack a stronger engagement with their target. On the other hand, biological mimics and components provide a better engagement but due to their larger size and polarity, their cell penetrating abilities pose a challenge to the researcher.

A more recent approach involves the use of peptidic drugs as a midpoint between the two sides, providing the advantageous accessibility and affinity that small molecules and biologics have. Finding novel cell-penetrating peptides with drug-like properties has been a rising trend in recent years and their high potential has now been proven.

Using this knowledge, this project aims to find new applications for constrained peptides that are held as an alpha-helix or beta-sheet. This constraint would ensure that the secondary structure displayed is ideal for its target. The targets described will be proteins that are prone to aggregation and other pathogenic protein-protein interactions (PPIs) which are described in patients with either neurogenerative, inflammatory, immune diseases or cancers. In this sense, three studies are proposed as a starting point:

(1) Design of and synthesis of constrained alpha-helical peptides that are functionalised to bind to a protein of interest (POI) in order to inhibit the formation of undesired PPIs.

(2) Investigate the induction of peptide "strandicity" as opposed to "helicity" via the rational design of functionalised constraints.

(3) Finally, we aim to improve cell penetrability by introducing additional functionality into the cargo of the peptide.

The peptides and their constraints will be made synthetically and their target affinity will be tested through biochemical techniques such as protein-fragment complementation assay (PCA). This technique consists of a bait-and-prey approach in which an essential protein for cell survival is only formed when the POI and peptide interact. If there is no interaction between the two components, no bacterial colonies will be observed. Cell-penetration will be monitored using fluorescent tags (FAM) attached to the peptides.

In conclusion, this project aims to develop and perfect constrained cell-penetrating peptides to target PPIs.