Ouch!! You cut your finger with a knife. Blood immediately starts coming out from the wound, and in a panic you search through your drawer for a band-aid. However, well before you can find the band-aid, and even before the "ouch" came out, just about the same time you sensed the pain, your body's self-healing mechanism was turned on. A multistep signaling cascade involving a dozen different proteins in the blood started immediately after the cut, calling for platelet cells to clog arround the wound and form a plug to stop the bleeding. How does our body sense a wound so fast? A possible answer is that the platelet cells carry on their surface a sensitive molecular flow sensor, a protein called GP1b, which senses erroneous blood flow caused by a cut in the blood vessel. It has been hypothesized that a small segment located on the alpha-subunit of GP1b, called the ß-switch, transforms from a random coil to a ß-hairpin in the presence of shear flow (see movies). The ß-switch, in its ß-hairpin form, is able to bind to a protein called von Willerbrand factor, which will then anchor the platelet to the damage site. To test this hypothesis, researchers resorted to computer simulation using the program NAMD and mimicked blood flow around GP1b. As reported recently, the researchers discovered that a long suspected part of GP1b indeed changes shape under flow conditions, the likely trigger of the body's self-healing system. For more information see our molecular flow sensor web site.