The Tyrolean Iceman, a Copper-age specimen, has been one of the most studied mummies ever since hikers found his frozen, preserved body in the Alps in 1991. Since then, scientists have reconstructed his face, clothing, genome and last meal.
A native of central Europe, Ötzi was a 45-year-old agriculturalist, tattooed, and suffered from heart disease, tooth decay, joint pain and lyme disease. A wound shows that an arrow pierced an artery in his shoulder, and an undigested meal in his stomach suggests he was ambushed.
A CAT scan from a previous study showed dark spots at the back of the mummy's cerebrum, suggesting Ötzi also suffered a blow to the head during the fatal attack. But scientists are unclear whether he was hit in the head or suffered a fall after being hit with the arrow.
Scientists took samples of brain tissue and found clotted blood, confirming that Ötzi suffered brain bruising before his death.
A separate 2012 study looked at Ötzi's red blood cells -- the oldest ever identified -- and showed traces of fibrin, a clotting protein which appears in human blood immediately after a wound but disappears quickly. That it was still in Ötzi's blood when he died suggests he didn't survive long after the arrow shot.
The new study focused on proteins found in two brain tissue samples. Of the 502 different proteins identified, 10 were related to blood and coagulation, and they also found evidence of an accumulation of proteins related to wound healing.
"Proteins are the decisive players in tissues and cells, and they conduct most of the processes which take place in cells," Andreas Tholey, a scientist at Germany's Kiel University and a researcher on the new Ötzi study, said in a statement.
A microscopic analysis even revealed well-preserved neural cell structures, the researchers said. Their research was detailed in the journal Cellular and Molecular Life Sciences.