Detection of ferric ions in a gram-positive bacterial cell: Staphylococcus aureus

• Published in: Journal of coordination chemistry Vol. 74; no. 1-3; pp. 380 - 401
• Main Authors: Manandhar, Erendra, Johnson, Ashley D. G., Watson, William M., Dickerson, Shelby D., Sahukhal, Gyan S., Elasri, Mohamed O., Fronczek, Frank R., Cragg, Peter J., Wallace, Karl J.
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 23.12.2020; Taylor & Francis Ltd
• Subjects: Aluminum; Arsenic; Calcium ions; Chemical sensors; Chemoreceptors; Cobalt; coordination; Crystal structure; Ferric ions; Fluorescence; gram-positive bacteria; Mercury (metal); molecular probes; NMR; Nuclear magnetic resonance; Oxidation; Rhodamine; sensing; Stoichiometry
• ISSN: 0095-8972; 1029-0389
• DOI: 10.1080/00958972.2020.1868042

A rhodamine-based chemosensor was synthesized and found to selectively bind ferric ions over other metal ions (Na + , K + , Ca 2+ , Mg 2+ , Fe 2+ , Zn 2+ , Cd 2+ , Co 2+ , Hg 2+ Cr 3+ , Al 3+ ) in an organic-aqueous mixture (CH 3 CN-MES). Upon addition of ferric ions, the spirolactam ring opens, producing a visual color change and a fluorescence intensity increase, i.e. a "turn on" optical response at 577 nm is observed. The chemosensor coordinates to ferric ions in 1:1 stoichiometry with a calculated K a = 3.5 × 10 4  mol⋅dm −3 by fluorescence spectroscopy and a LoD of 27 ppb. The chemosensor was reversible upon addition of the Fe 3+ chelator desferrioxamine. One- and two-dimensional NMR experiments with Al 3+ ions aided in understanding of the coordination environment of the ferric ion with the chemosensor, which were confirmed by molecular modeling calculations. X-ray quality crystals of the chemosensor were obtained, and the solid-state structure is reported. Confocal microscopy was used to detect free ferric ions in Staphylococcus aureus.