Selectivity and Specificity in Chelation
Although chelating agents are never entirely specific for a particular metal ion,
some complicated chelating agents of biological origin approach almost complete
specificity for certain metal ions. One example of such a chelating agent is ferrichrome,
synthesized by and extracted from fungi, which forms extremely stable
chelates with iron(III). It has been observed that cyanobacteria of the Anabaena
species secrete appreciable quantities of iron-selective hydroxamate chelating agents
during periods of heavy algal bloom. These photosynthetic organisms readily take up
iron chelated by hydroxamate-chelated iron, whereas some competing green algae,