Chemistry Experts Team Up to Predict Reactions

Two Johns Hopkins chemists -- one bioinorganic and the other environmental -- have joined forces to create a new approach for studying pollutant reactions in the environment. By drawing on their different areas of expertise, researchers Justine P. Roth and Alan T. Stone hope to develop a better way to predict the behavior of previously unexplored pollutants, including some hazardous metals.

Roth, an assistant professor in the Department of Chemistry, based in the university's Krieger School of Arts and Sciences, develops methods to examine how enzyme-bound metals gain or lose electrons, most notably in response to reactions with oxygen. A number of elements, including oxygen, exist as two or more natural isotopes, meaning their atoms possess the same number of protons but different numbers of neutrons. Molecules made up of different isotopes react at slightly different rates when the electrons move from one position to another. By comparing these rates, Roth is able to collect important information about the reactions and interpret the results using computational chemistry.

Stone, an environmental chemist in the Department of Geography and Environmental Engineering, based in the Whiting School of Engineering, realized that Roth's approach could uncover critical new data about how pollutant molecules react with chemicals that are naturally present in water, soils and sediments.

Their decision to pool their skills recently received a key endorsement from the Camille and Henry Dreyfus Foundation, which allocated a $120,000 fellowship grant to the faculty members. The money will support two years of research by a postdoctoral scientist who will be supervised by both Stone and Roth. The researcher will seek to develop fundamental models that describe the transfer of electrons to and from dissolved chemicals and mineral surfaces.

The team is interested in gains or losses of electrons that occur when pollutants react with naturally occurring minerals. For example, manganese oxide minerals, which appear black, and iron oxide minerals, with red, yellow, orange and brown hues, are believed to play a particularly important role when they make contact with some hazardous metals. When these minerals take electrons away from the toxic metal chromium, the metal is less likely to stick to soils and is often carried away by water. In contrast, taking electrons away from the toxic metal lead causes the metal to precipitate, forming solid particles that separate from the water instead of dissolving in it.

"With this fellowship, a traditional chemist or chemical engineer will be able to apply his or her skills toward an urgent environmental pollution problem," Stone said. "We need a better understanding of what kind of chemical reactions occur when hazardous metals and other waste materials come in contact with minerals that are already there in the environment."

Added Roth: "This is a chance to apply some of our new lab techniques to practical problems encountered in the Chesapeake Bay and other ecosystems. Appreciating the mechanisms of chemical reactions is something Alan and I have in common. We’re really forging a new field in environmental science by focusing on the fundamental reactions that are taking place when contaminants are present in soil and water."

The Camille and Henry Dreyfus Foundation Inc., based in New York City, was established in 1946 by chemist, inventor and businessman Camille Dreyfus as a memorial to his brother Henry, also a chemist and his partner in developing the first commercially successful system of cellulose acetate fiber production.

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