July 28, 2010

Where Do The Drugs Go?

Drug delivery inside the body is a complicated process. Compounds travel through a maze of aqueous solutions, lipid membranes, and barriers between the blood and tissues like the brain. Research reported in the American Institute of Physics publication the Journal of Chemical Physics presents a theoretical model that accurately predicts the hydration free energy (HFE) of a wide variety of organic compounds.

"HFE determines solubility and allows accurate prediction of a compound's path in a complex environment," says author Maxim Fedorov of the Max Planck Institute for Mathematics in the Sciences. "For example, in passive transport, you want to know that the compound will cross a lipid layer into the aqueous environment inside a cell rather than moving back into the surrounding aqueous environment."

Unfortunately, HFE is not measured easily or quickly, so it is available for only about a thousand of the 20 million known organic compounds. Standard prediction methods are inaccurate. The new model used a database of about 50 known HFE values to build a theoretical model using computational hydration thermodynamics and chemo-informatic techniques. "Our predictions are accurate and very cheap computationally, requiring only 10 to 20 seconds on a PC," says Fedorov.

The ultimate goal is to predict the movement of a compound in a complex environment and to screen large databases of candidate compounds for desirable characteristics. In addition to the pharmaceutical applications, Fedorov sees potential application in modeling the environmental flow of agricultural chemicals or industrial pollutants.


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