iderophores usually form a stable, hexadentate, octahedral complex preferentially with Fe3+ compared to other naturally occurring abundant metal ions, although if there are less than six donor atoms water can also coordinate. The most effective siderophores are those that have three bidentate ligands per molecule, forming a hexadentate complex and causing a smaller entropic change than that caused by chelating a single ferric ion with separate ligands.[15] A comprehensive list of siderophores is presented in.[16] Fe3+ is a hard Lewis acid, preferring hard Lewis bases such as anionic or neutral oxygen to coordinate with. Microbes usually release the iron from the siderophore by reduction to Fe2+ which has little affinity to these ligands.[8]
Siderophores are usually classified by the ligands used to chelate the ferric iron. The major groups of siderophores include the catecholates (phenolates), hydroxamates and carboxylates (e.g. derivatives of citric acid).[3] Citric acid can also act as a siderophore.[17] The wide variety of siderophores may be due to evolutionary pressures placed on microbes to produce structurally different siderophores which cannot be transported by other microbes' specific active transport systems, or in the case of pathogens deactivated by the host organism.[3][6]
iderophores usually form a stable, hexadentate, octahedral complex preferentially with Fe3+ compared to other naturally occurring abundant metal ions, although if there are less than six donor atoms water can also coordinate. The most effective siderophores are those that have three bidentate ligands per molecule, forming a hexadentate complex and causing a smaller entropic change than that caused by chelating a single ferric ion with separate ligands.[15] A comprehensive list of siderophores is presented in.[16] Fe3+ is a hard Lewis acid, preferring hard Lewis bases such as anionic or neutral oxygen to coordinate with. Microbes usually release the iron from the siderophore by reduction to Fe2+ which has little affinity to these ligands.[8]
Siderophores are usually classified by the ligands used to chelate the ferric iron. The major groups of siderophores include the catecholates (phenolates), hydroxamates and carboxylates (e.g. derivatives of citric acid).[3] Citric acid can also act as a siderophore.[17] The wide variety of siderophores may be due to evolutionary pressures placed on microbes to produce structurally different siderophores which cannot be transported by other microbes' specific active transport systems, or in the case of pathogens deactivated by the host organism.[3][6]
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