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Where would biologists be without the myriad of synthetic methods and small molecules developed by chemists? Unfortunately, the door does not usually swing both ways; biological tools are rarely used to solve purely chemical problems.

Frédéric Taran, of the French Atomic Energy Commission, aims to change this imbalance, by demonstrating that biological assays can in fact have useful chemical applications. “I was fascinated by the analytical potential of immunoassays,” he says. “They allow the direct measurement of a specific product in complex mixtures without any work-up, and they are fast, precise and sensitive...everything a chemist needs for analyzing reactions!”

Sandwich immunoassays (known more commonly to biologists as enzyme-linked immunosorbent assays; ELISAs) use two monoclonal antibodies that recognize distinct binding epitopes on a single antigen. One antibody is immobilized on a solid support and the other antibody is conjugated to an enzyme that converts a substrate to an easily detectable product. Taran and colleagues extended the idea to detect the products of bond-forming organic coupling reactions. They raised antibodies to recognize small-molecule tags linked to chemically reactive groups. After allowing the chemical reaction to proceed, they analyzed the crude reaction mixture by ELISA and detected bond formation by monitoring the conversion of the enzyme substrate to a colored product.

As chemists, Taran and colleagues are interested in developing high-throughput screening methods to aid in the discovery of synthetic catalysts, and they show that their sandwich immunoassay can be used as an extremely fast, sensitive and general screen for catalysts that trigger bond formation between reactive species. Notably, many reactions can be screened simultaneously in a microtiter plate, using an automatic plate absorbance reader to quantify the product.

Taran hopes that their screening method will be viewed as a useful tool by industrial chemists. He says, “Many chemists are not familiar with immunoassay techniques and are often convinced that they are complicated to set up. But I think this is not the case; these techniques can be routinely run to answer chemical questions without large investments.”