Extended x-ray absorption fine-structure study of the bound form of lanthane in chlorophyll-a from Dicranopteris dichotoma

The in vivo coordination structure of lanthanum. ions interacting with chlo rophyll-a of the fern. Dicranopteris dichotoma grown in a rare earth minefi eld in southern China was determined by the extended xray absorption fine s tructure (EXAFS). The results show that lanthanum. includes two porphyrin r ings in its coordination sphere. It is postulated that the La-chlorophyll-a complex may have a bilayer structure. The analytical method may serve as a new tool to gain insight in the in vivo interactions of rare earth element s.