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.