Purging Drugs Of Their Evil Twins
PROMISING DRUGS MUST SOMETIMES BE SHELVED because they contain sinister elements that are mirror images of the beneficial ingredients. Many molecules come in two versions--chemically identical, but reversed in structure. Chemists dub them right-handed or left-handed and refer to them as chiral molecules. When thalidomide was marketed 40 years ago, a left-handed molecule provided relief from morning sickness. But its right-handed counterpart caused horrible birth defects.
Because chiral molecules behave the same in chemical reactions, separating them is tough. That may soon change. Isiah M. Warner, chairman of Louisiana State University's chemistry department, recently received $750,000 in federal grants to develop promising solutions he has pioneered.
One uses tiny balls of special surfactant molecules. While these attach to both chiral forms, either the right-handed or the left-handed version has a slightly stronger bond--and this can be exploited. Pass a current through the solution, and the weak-bond clumps move more rapidly toward an electrode, leaving behind the strong-bond clumps. Warner believes this process could be scaled up to purify bulk chemicals.