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Angewandte Chemie Press Release No. 11/99
Angew. Chem. Int. Ed. 1999, 38, 1793 - 1795

Poison Gas Test That Fits in Your PocketA simple biochemical test kit detects sarin at a fraction of the previous cost

They are feared as the "poor country's nuclear weapon": the chemical weapons - also known as nerve gasses - sarin and soman. They are easy to produce, and the necessary starting materials are cheap and relatively easy to obtain. Sarin and its relatives are deadly and internationally monitored. Inspections of potential poison gas production plants serve this purpose, but are difficult. Until now, the procedure has consisted of taking soil samples on location and analyzing them with complicated special equipment, usually in a distant laboratory. A portable test kit, whose fundamentals have been introduced by a research group working with Kim D. Janda and Peter Wirsching at California's Scripps Research Institute, could change this.

Many of the rapid tests currently distributed in portable "suitcase laboratories" stem from the ability of artificially generated antibodies to quickly and accurately recognize specific substances to which they have previously been "trained." Biochemists copied this idea, among others, from the human immune system; here too, antibodies are responsible for crucial friend-foe recognition. In the case of sarin, however, there was a problem: previously, no one could obtain antibodies that reacted to this nerve gas.

Janda and Wirsching came up with a trick, though. They used the fact that one of the natural decomposition products of sarin, methylphosphonic acid (MPA), contains two relatively reactive binding sites. To these, the researchers bound two conspicuous molecular fragments using an easily obtainable reaction solution. After this reaction, the nearly spherical MPA molecule looks like an air-traffic controller with two signal flags - and like the controller, the "signal-flags" render the molecule far more noticeable. Janda and Wirshing were now finally able to "train" special antibodies to recognize MPA molecules modified in this way.

In the future, the search for traces of poison gas could thus look like this: a bit of dust is collected in a suspected weapons manufacturing plant, some solvent containing the "signal-flag reagent" is added, and the mixture is dripped onto a small plate containing the antibodies. If the antibodies recognize the decomposition products of sarin, the reaction mixture changes color, and the terrorist is convicted - without any high-tech machinery.

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