Bleached brains

 作者:司侑丑     |      日期:2019-03-08 04:05:01
By Michael Day THE abnormal protein deposits that clog the brains of Alzheimer’s patients probably damage nerve cells by producing the toxic chemical hydrogen peroxide, new research suggests. Experts say this raises hopes that it might be possible to treat the disease by blocking this fairly simple chemical. In Alzheimer’s disease, an abnormal form of beta-amyloid protein forms in the brain. Scientists already knew that cells containing this protein also have raised levels of the powerful oxidising agent hydrogen peroxide. However, it was unclear why this was. To find out more, scientists from Harvard Medical School and the University of Heidelberg looked at the chemical reactions in these cells by studying changes in the way they absorbed light and fluoresced. The researchers discovered that when abnormal beta-amyloid binds to iron andcopper, the metal ions donate electrons to dissolved oxygen ( Biochemistry, vol 99, p 438). Oxygen molecules with two excess negative charges then react with hydrogen ions to form hydrogen peroxide. The team also showed that the type of beta-amyloid associated with the most aggressive form of Alzheimer’s was the best at binding copper and iron—and hence at generating peroxide—suggesting that this reaction is a major factor in causing the brain damage. “Ultimately we would like to be able to interrupt this process,” says team member Ashley Bush of Harvard Medical School in Charlestown, Massachusetts. “The sites where the copper and iron bind could be an easy target.” He adds that scientists will first need to figure out the three-dimensional structure of the binding site. The new evidence that the generation of peroxide may be involved in the disease process fits in with other observations,