Sucking secrets

How do vampires suck blood? Well, the mythical nocturnal terrors may be using a protein that makes blood sucking easy. Chemists have uncovered the structure of a protein in the saliva of bloodsucking insects that helps them extract a bigger meal from their victims. The protein -- called nitrophorin one -- stores nitric oxide, which dilates blood vessels. When insects such as bedbugs squirt saliva into blood, a drop in acidity triggers the release of this nitric oxide, delivering more blood to the hungry pest. The host, meanwhile, feels absolutely nothing because the protein also mops up histamine, which normally triggers irritation as well as an immune reaction. "It stops the victim from feeling any distress, so the insect has more time to feed," says Ann Walker, joint leader of the team from the University of Arizona, USA, which made the discovery. Walker and her colleagues reported the structure of the protein in a recent issue of Journal of the American Chemical Society (Vol 121, p 128).