Results promising for computational quantum chemical methods for drug d...( Blacksburg Va. New research led by ...),Health

Blacksburg, Va. New research, led by a Virginia Tech chemist, may someday help natural-products chemists decrease by years the amount of time it takes for the development of certain types of medicinal drugs. The research by T. Daniel Crawford, associate professor of chemistry, involves computations of optical rotation angles on chiralnon-superimposablemolecules. The research titled, The Current State of Ab Initio Calculations of Optical Rotation and Electronic Circular Dichcoism Spectra, appeared recently as the cover article in The Journal of Physical Chemistry A.

Many chiral molecules are important for medical treatment for illnesses ranging from acid-reflux to cancer. The term chiral means that two mirror images of a molecule cannot be superimposed onto each other. In other words, some are left-handed and some are right-handed.

Most drugs have this handedness property, Crawford said, and for many of these drugs, even though both hands can cause a reaction, it is a situation where one hand does a good thing and one does a bad thing. He used thalidomide as an example. A mixture of both hands of the drug was used in the late 1950s and early 1960s to treat morning sickness in pregnant women. Later studies revealed that, while one of the two hands acted as the desired sedative, the other hand was found to cause significant birth defects. Thalidomide was never approved by the FDA in the United States and was eventually taken off the market in Europe.

For chemists, therefore, it is often vital to determine which hand of a molecule they are using. In other words, when you have a sample of a chiral molecule, how do you distinguish between the left and right hand"

This is where a technique called polarimetry comes in to play. By shooting plane-polarized light through a sample of one hand, the chiral molecule in question will rotate to a characteristic angle either clockwise or counterclockwise, and the two hands of a chiral molec
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