The physics of X-ray absorption spectroscopy (XAS) has provided a way to study complex materials, both in situ and in an element-specific way. Notably, K-edge XAS has greatly enhanced the study of biological metals.
Ascidians are an ancient line of animals that are almost unchanged since the Cambrian (550 My). They have large concentrations of vanadium and sulfuric acid in their blood cells, which represent perhaps the most unusual bio-metallic system known.
Ascidians as a research subject will be described. The K-edge XAS spectra of blood cell vanadium will be shown, and then used to deconvolute the kinds of vanadium that are present. The results will point to a chemical analogy that, in turn, will allow a new hypothesis predicting how ascidians manipulate blood cell vanadium. Thus the physics of XAS have produced a light that shines onto a 500 million year old mystery.