Research under way at Monash University's Malaysian campus could result in lasers being used to produce molecular switches and single-isomer drugs.

Dr Lan Boon Leong is designing laser pulses which will create molecular switches.

Molecules are formed when atoms link up. Probably the best known example is H2O, where two atoms of hydrogen bond with one of oxygen to produce water.

Dr Lan Boon Leong, a lecturer in physics at Monash's campus near Kuala Lumpur, is particularly interested in families of molecules called isomers, which are variations on a theme - they contain the same atoms, but are arranged differently. Isomers are of interest not just to chemists, but to investigators as diverse as computer scientists and drug designers.

In collaboration with Professor Werner Jakubetz from the University of Vienna, Dr Lan is working with the small, three-atom (hydrogen, carbon, nitrogen) molecule of hydrogen cyanide. This has two isomers - HCN and HNC - whose properties are well known.

The researchers are designing laser pulses that will transfer, or switch, the hydrogen atom from the carbon to the nitrogen side of the molecule in ultrafast time. The aim: to develop a controlled, predictable process that will create a molecular switch - a small switch indeed.

Towards molecular computing

Monashıs Malaysia campus where researchers are working on the molecular switch project with a researcher from the University of Vienna.

An ultrafast molecular switch has a number of potential applications. One attracting a great deal of interest is molecular computing, because conventional silicon chips are thought to be approaching their limit in terms of speed.

The researchers' work could also help drug companies produce single-isomer drugs instead of the typical 50-50 mixture of two mirror-image isomers. This is highly desirable because, in some cases, one of the isomers is harmful. For example, one of the isomers of thalidomide is a sedative but the other causes birth defects.

Super-computing solution

"In theory, it should be possible to turn the mixture into 'harmless' single isomers by zapping it with properly designed laser pulses, based on a complete quantum chemical knowledge of the molecule," Dr Lan says. "Unfortunately, pharmaceutically useful isomers are usually large, necessitating calculations that take years - even for a supercomputer."

One possible solution is feedback in the laboratory: the molecules are zapped with an initial laser pulse and the outcome measured. This information is sent to a computer which uses it in a genetic algorithm to vary the pulse characteristics and cycle repeats.

Dr Lan and Professor Jakubetz, however, are using hydrogen cyanide as a test case to develop an alternative solution. "It's a compromise approach which entails finding out, then using, the minimum amount of molecular information that's necessary to theoretically design laser pulses that will turn undesirable isomers into useful ones."

		To find out more on Dr Lan Boon Leong's research into isomers, email lan.boon.leong@engsci.monash.edu.my