New possibilities for drug design

An article in Journal of Physics B, published on 7 July 2003 by the Institute of Physics, reports on a new technique which could in future help scientists working in rational drug design (a way of tailoring a new drug to fit the structure of the protein it targets) to develop drugs more efficiently. The work, which was on a molecule called stella-2,6-dione, was a collaboration between colleagues at three Australian universities (Flinders, Swinburne and ANU), the Commonwealth Scientific and Industrial Research Organisation and the University of Heidelberg in Germany.

The team used a unique experimental method called electron momentum spectroscopy (EMS) to examine the outermost electrons in stella-2,6-dione, which are important for chemical and biological interactions. They were imaging the “wavefunction” of the molecule, which is a mathematical function that contains all the information about a molecule. So if you know its wavefunction, you have the basis of all the physics, chemistry and biology of that molecule.

Researchers usually use theoretical models to work out the wavefunction, rather than measuring it directly. As a wavefunction is so complicated, there are many different ways of approximating it. One such model is density functional theory (DFT), which is computationally inexpensive and so can be used for large and complex molecules. The team compared their experimental results from EMS against the calculated wavefunctions from DFT to discover which theoretical approximation was best.

This optimum approximation could then be used in the quantitative structure activity relationships (QSAR) method for drug design. Using QSAR, properties of the molecule can be calculated that are needed for designing new drugs, and that cannot be otherwise measured.

This study confirmed that EMS is a practical way of finding out the wavefunctions of large molecules.

Dr Michael Brunger, from Flinders University of South Australia, said:
“We showed that EMS can be successfully used to study larger molecules. Drugs are generally made up of lots of large molecules and so we believe EMS will be of real use to rational drug design and the drug industry.”