How does the concentration and chemical speciation of elements change across an organism?
Living systems are not homogeneous: The gradients of metals and other elements across an organism reveal important information about structure and function. A great deal has already been done by fluorescence microscopy, including, for example, many beautiful studies of calcium waves in different organisms. However, x-ray spectromicroscopy can discover information inaccessible by other means. For example, James Penner-Hahn has used x-ray absorption to study the distribution of zinc in sperm cells, where he has seen clear gradients across the cells. Further, the changes in zinc NEXAFS between different locations indicates different chemical forms of the element. • How does the chemical speciation of elements change over time? The time dependence of chemical species in an organism is just as important as the spatial variation. X-ray spectroscopy can provide valuable information about species which are difficult to observe by other spectroscopies. For example, Klein and coworkers have used
