The rapid development and dissemination of antibiotic resistance in pathogenic bacteria requires new strategies and new structural scaffolds of antimicrobial compounds to be investigated. A developing trend targets virulence factors rather than pathways essential for survival in an effort to neutralize pathogens while minimizing the risk of resistance. The thesis focuses on the design of new molecules from peptides to peptidomimetics aimed at disrupting the bacterial periplasmic oxidative

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... , a new antivirulence target. This thesis initially describes in chapter I the recent emergence of peptidomimetics in antimicrobial treatments aimed at well-known mechanisms as well as novel targets. Peptidomimetics may be particularly efficient for disrupting protein-protein interactions and have been successful for instance in preventing post-translational modifications or the formation of pili machinery. The thesis also highlights the mechanism and context of the interaction between DsbA and DsbB, both primary factors in the periplasmic oxidative system of gram-negative bacteria and the target proteins of this PhD. Developing inhibitors requires a solid screening pipeline of biophysical assays to measure binding parameters such as affinity, thermodynamics and kinetics. Chapter II highlights the building and optimization of such a pipeline by evaluating differential scanning fluorimetry, isothermal titration calorimetry, surface plasmon resonance, substrate oxidation assay and crystallography in order to characterize the designed peptide scaffolds. Chapter III focuses on the structure-activity relationship studies of 31 manually synthesized peptide sequences screened through this pipeline. Based on peptide length scouting, alanine scanning and rational substitution of specific residues, a final heptameric peptide was found to bind Escherichia coli DsbA with a Kd of 2.9 ± 0.3 µM. Moreover, the data suggest a probable disulfide bond formation between peptide and DsbA essential to the binding interface, while cysteine-free peptides present very weak affinity towards EcDsbA. This chapter generated a manuscript submitted to the Journal of Medicinal Chemistry. iii