Transmembrane Fluoride Transport by a Cyclic Azapeptide With Two β-Turns

Area of Science:

• Supramolecular Chemistry
• Membrane Transport
• Chemical Biology

Background:

• Anion transporters are crucial in biological systems, with chloride transport extensively studied.
• Fluoride transport remains less explored despite its significance in bacterial survival.
• Existing anion transporters often focus on chloride, overlooking fluoride's unique role.

Purpose of the Study:

• To design and synthesize a novel cyclic azapeptide for selective fluoride transport.
• To investigate the role of molecular encapsulation in enhancing anion transporter activity.
• To compare the fluoride transport capabilities of a cyclic receptor versus acyclic analogs.

Main Methods:

• Synthesis of a cyclic azapeptide (1) and acyclic control compounds (2, 3).
• Structural analysis to confirm stable β-turn structures in the cyclic receptor.
• Osmotic assays and fluoride ion-selective electrode (ISE) measurements to assess transmembrane transport.
• Electrochemical analysis to determine the transport mechanism.

Main Results:

• Cyclic receptor 1 demonstrated selective fluoride transport across a lipid bilayer.
• Acyclic compounds 2 and 3 showed no transmembrane transport activity, despite binding fluoride.
• An electrogenic anion transport mechanism was identified for the cyclic receptor.
• The cyclic structure provided a confined cavity with hydrogen bond donors for anion binding.

Conclusions:

• Encapsulation of an anionic guest within a cyclic host is critical for enhancing anion transport activity and selectivity.
• The cyclic azapeptide 1 represents a promising new class of selective fluoride transporters.
• Molecular design focusing on host-guest chemistry can overcome limitations in anion transport research.