Reactivity of Petrobactin and Its Sulfonated Derivatives with Iron and Their Determination by Isotopic Saturation...

Petrobactin is a bis-catechol siderophore, synthesized by Marinobacter nauticus (formerly Marinobacter hydrocarbonoclasticus), an important oil-degrading bacterium that proliferates in oil-polluted marine ecosystems. The complexes formed by petrobactin and its sulfonated derivatives with iron were, for the first time, chromatographically separated and identified by mass spectrometry. Conditions for the separation of the iron complexes using reversed-phase HPLC and size-exclusion LC were optimized. A method for quantifying petrobactin and its sulfonated derivatives has been developed. The analytical procedure is based on the saturation of the apo form of the siderophore with isotopically enriched iron, followed by its separation by ultraperformance size-exclusion chromatography with ICP-MS detection. The method is characterized by a detection limit of 0.03 ± 0.01 and 0.02 ± 0.01 μmol L^-1, for petrobactin and sulfonated derivatives, respectively. Conditions of the formation of iron complexes were discussed in terms of iron source and pH. The complexation reaction was the fastest when iron was supplied as citrate or malate and when it occurred at pH 8. The monosulfonated derivative bound iron significantly faster than petrobactin itself, unlike the disulfonated derivative.