Azobenzene-bridged potent divalent ligands of Pseudomonas aeruginosa LecA

Photoswitchable glycoligands present an alternative tool to investigate interaction between bacterial lectins and carbohydrates and the potential to the light-controlled inhibition of bacterial adhesion and biofilm formation. Based on the reported potent divalent inhibitors of Pseudomonas aeruginosa LecA, we have designed and synthesized a series of azobenzene-bridged bis-galactosides bearing different linkers with varied distance between the two galactoside units. All the synthesized divalent ligands are photoswitchable in aqueous medium, with good to excellent photochromic properties, and nanomolar to low nanomolar range affinity towards LecA. However, only the triazole-linked tetra-fluoroazobenzene ligand 3 showed a significant photoswitching effect (3.5-fold lower affinity for Z-3 compared to E-3). Mass photometry analysis has been used to investigate the ligand-lectin interaction, allowing to evaluate the size for LecA-ligand complexes and to determine the equilibrium between chelation of neighboring sites and cross-linking between tetramers. This equilibrium is dependent on the nature of the compounds with a more pronounced chelating effect for the Z-isomers. Molecular modeling study with docking and molecular dynamics rationalized the very high affinity observed for one compound and the weak differences observed between the E and Z photoinhibitors.