Mercury is a toxic pollutant released into the atmosphere from coal-fired power plants. In its native form, it is a metallic liquid – the same silvery liquid found in old thermometers. As a metal, its toxicity is relatively limited as it is difficult for the mercury to cross the skin barrier (unless there are cuts or scrapes present). However, chemical changes to the mercury, specifically changes which oxidize the mercury into a cationic state, greatly enhance the toxicity of the mercury as the resulting molecule is water-soluble. When you consider that mercury spills in natural water sources such as lakes and rivers can rapidly contaminate the water supply, and that water soluble salts are extremely difficult to cheaply purify from the surrounding solvent, there is an obvious need for new mercury remediation technologies.
A recent publication in the top journal Science reveals a new technique for mercury cleanup which receives its inspiration from Nature. Certain species of bacteria are able to thrive in mercury-laden waters, which doesn’t make sense at first glance as these conditions are normally toxic to life. However, long strands of amino acids known as enzymes are present inside the bacteria; these enzymes act as catalysts, and rapidly break the (normally strong) mercury-carbon bond present in the mercury contaminant. This is a reaction that chemists struggle mightily to perform in the laboratory; our catalysts do not yet approach the power and versatility of the enzymatic catalysts found in Nature.
The team of chemists took this bacteria, isolated the enzyme, and studied its structure carefully. The enzyme itself is quite large, as far as molecules go; however, the region of the enzyme responsible for the mercury decontamination is a relatively small section of the molecule. The chemists then synthesized a much smaller molecule from simple starting materials that mimicked this region of the enzyme. Tests showed this new artificial “enzyme” to be very effective at cleaning up mercury contaminated water supplies.
This type of research has extremely exciting long-term implications. It’s a great example of how scientists can dissect a complicated problem, focus on the crucial key point, and then develop a new smaller system that performs the same essential function without the baggage / cost associated with a much larger chemical species.
Source for this article:
“Cleaving Mercury-Alkyl Bonds: A Functional Model for Mercury Detoxification by MerB“
Melnick, J. G.; Parkin, G.
Science , a publication of the American Association for the Advancement of Science.