How Many O-Donor Groups in Enterobactin Does It Take to Bind a Metal Cation?

Area of Science:

• Inorganic Chemistry
• Bioinorganic Chemistry
• Coordination Chemistry

Background:

• Enterobactin is a potent iron chelator produced by E. coli.
• Siderophores play crucial roles in metal ion transport and homeostasis.
• Understanding enterobactin's metal binding is key to its biological function and potential applications.

Purpose of the Study:

• To synthesize and characterize non-symmetric enterobactin analogues.
• To investigate the complexation of Si^IV, Ge^IV, and Ti^IV with enterobactin derivatives.
• To elucidate the structural and electronic factors governing enterobactin's metal binding affinity.

Main Methods:

• Development of synthetic protocols for enterobactin analogues with varying denticities.
• Coupling of diverse benzoic acid residues to the macrocyclic lactone.
• Complexation studies with Si^IV, Ge^IV, and Ti^IV.
• Investigation using experimental and computational techniques, including Density Functional Theory (DFT).

Main Results:

• Successful synthesis of a diverse library of enterobactin analogues.
• Demonstration of hexacoordinate complex formation with Si^IV, Ge^IV, and Ti^IV.
• Identification that a minimum of four O-donors are required for metal binding by enterobactin derivatives.
• DFT calculations revealed that diminished translational entropy and optimal catecholate geometry contribute to strong binding.

Conclusions:

• Enterobactin derivatives exhibit strong complexation with Si^IV, Ge^IV, and Ti^IV.
• The number of coordinating O-donors is critical for metal binding efficacy.
• The chelate effect and specific ligand arrangement enhance the binding strength of enterobactin.