Tags out, chips in

THE speed with which new techniques are being introduced in many areas of science, has increased tremendously; whether it is faster techniques for gene sequencing or more efficient image processing algorithms, new methods have made possible many innovations which were hitherto inconceivable.

Combinatorial chemistry, introduced a few years ago, was one such technique. The idea, as the name suggests, was to try and form all possible combinations of a few basic chemicals with the hope that a few of them would be useful. Taking basic building blocks and mixing them, you could end up with a wonder drug or a new material with amazing properties.

Chemical compounds are identified by chemical tags, wherein lies the rub. Each tag increases the number of steps (and the time) for synthesis, and makes synthesis of some compounds difficult. This is because some of the processes involve strong reagents which render the chemical tags ineffective. Now researchers have come up with a scheme which does away with chemical tags altogether. Rob Armstrong and his colleagues at Ontogen Corp and Michael Nova and his team at IRORI Quantum Microchemistry, La Jolla - both in California - have succeeded in replacing chemical tags with microchips (Science, Vol 270, October 27, 1995).

A chip which emits radio signals is inserted in a capsule loaded with polymer beads which serve as the seeds on which the compounds grow. Everytime the seed enters a reagent beaker, the chip emits a signal, thereby identifying the content. This information is recorded on a computer, which thus instantly has a clue to the identity and the structure of the compound.

This approach has not only speeded Lip the synthesis of many Compounds, but has also made possible some compounds which were not easy to synthesise with the chemical tag method, Combinatorial chemistry - even with the relatively slower chemical tags - was the fastest technique to synthesise new compounds. With the faster radio tags, it would give chemists the required speed and flexibility to explore new frontiers.

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