Vanabins
（重定向自Vanadium chromagen）
Vanabins (also known as vanadium-associated proteins or vanadium chromagen) are a specific group of vanadium-binding metalloproteins. Vanabins are found almost exclusively in the blood cells, or vanadocytes of some ascidians and tunicates (sea squirts). The vanabins extracted from tunicate vanadocytes are often called hemovanadins. These organisms are able to concentrate vanadium to a level more than 100 times higher than in the surrounding seawater. Vanabin proteins seem to be involved in collecting and accumulating this metal ion. At present there is no conclusive understanding of why these organisms collect vanadium, and it remains a biological mystery.