Synthese von orthogonal photoschaltbaren Azobenzol-Glycoclustern zur Untersuchung des Einflusses der Ligand-Orientierung im Kontext bakterieller Adhäsion

Numerous biological processes, such as the adhesion of bacteria to the highly glycosylated cell surface, the glycocalyx, are governed by carbohydrate-protein (lectin) interactions. Understanding such processes requires the consideration of effects such as multivalency, heteromultivalency as well as the density and relative spatial orientation of the ligands. Azobenzene glycoconjugates have proven to be effective molecular tools to control the orientation of carbohydrates by light-induced isomerization of the azo group and study the influence of ligand orientation, e.g. in carbohydrate-specific bacterial adhesion.

In this work, the first orthogonally photoswitchable heterobivalent azobenzene glycocluster was synthesized, its photochromic properties and thermal relaxation kinetics were studied in detail, and the ligand orientation of the addressable predominating isomers (EE, EZ, and ZZ) was analyzed. The combination of an electron-rich unsubstituted and an electron-poor tetra-ortho-fluorinated azobenzene derivative enables orthogonal photoswitching of the antennas. This allows the 3D orientation of the terminal glycoligands (Glc/Man) to be changed as required.

This heterobivalent Glc/Man glycocluster was used as a molecular tool to address questions regarding the influence of ligand orientation on carbohydrate-lectin interactions. Besides the Glc/Man glycocluster a homobivalent Man/Man glycocluster and three photosensitive glycoconjugates, representing the antennas of the two glycoclusters, were tested in bacterial adhesion inhibition assays.

The results contribute to a deeper understanding of (hetero-) multivalence effects and the influence of ligand orientation on carbohydrate-lectin interactions. They also extend the young field of optoglycomics, which uses photosensitive glycoconjugates to elucidate carbohydrate recognition in greater detail.

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