A small cut won't bleed for long because tiny blood cells called platelets stick together and trigger clots. Damaged blood vessels and red blood cells release a compound known as adenosine diphosphate, or ADP, which triggers the process that makes platelets sticky.
Sometimes, however, overly reactive platelets are attracted to arteries damaged by fatty buildup. There, they form clots that, if dislodged, can sweep into the heart or brain, where they sometimes cause heart attacks or strokes.
Researchers know that two drugs—clopidogrel and ticlopidine—that are used to reduce the risk of heart attack and stroke work by blocking an ADP receptor found on the surface of platelets. However, analyzing the receptor itself has been a sticky problem, says Pamela B. Conley of COR Therapeutics in San Francisco. Researchers want to learn the sequence of amino acids in that protein.
"Knowing the . . . sequence will allow us to design better inhibitors for this recepto