Amino acids: fluorescensors for mercury ions

Arun Ankush Tanpure, a graduate student at IISER Pune, India, writes on a recent OBC article

Many human activities have been responsible for heavy metal poisoning in recent years, Mercury (Hg) poisoning being one of them. Mercury occurs in several forms and even trace concentrations of mercury ions in crops, fish or the human body are enough to produce potentially toxic effects to vital organs. Mercury poisoning can lead to several diseases including Acrodynia (also known as the pink disease), the Hunter-Russell syndrome and the Minamata disease.

Selective detection of mercury, particularly in aqueous media, has been a key area for analytical chemists, since traditional analytical techniques for mercury detection are time consuming, laborious and involve expensive instrumentation. In this work, Korean researcher Keun-Hyeung Lee and co-workers have developed a pair of very sensitive amino acid based fluorescence-ON probes for the exclusive detection of mercury ions in aqueous solution.

The team has combined the fluorescence properties of pyrene and Hg(II) binding ability of tyrosine residues for the design and synthesis of two novel fluorescensors. Both newly-synthesised probes show emission maxima at 386 and 400 nm in the absence of Hg(II) ion. Upon titration with Hg(II) ions, both probes show exponential fluorescence enhancement and display a remarkable red shift (90-100 nm) emission. These probes are also highly selective for mercury ions in the presence of a range of other metal ions and are effective in aqueous solutions.

The team further clarifies the binding mode of these sensors and the coordination of the metal ion. This method can be implemented for rapid and quantitative detection of Hg(II) from various polluted water sources. This work also underscores the unconventional use of an amino acid as a chemosensor.

Ratiometric fluorescence chemosensor based on tyrosine derivatives for monitoring mercury ions in aqueous solutions
Ponnaboina Thirupathi, Ponnaboina Saritha (née Gudellin) and Keun-Hyeung Lee
DOI: 10.1039/C4OB01044B

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