Cytochemical behaviour of rare earth ions in Euglena gracilis studied by XAFS

The uptake of rare earth elements(REE) by Euglena gracilis cell has been investigated in Fudan University. It was found that such cell can transport REE cations against an apparent concentration gradient on the order of 5 or higher. It is a very interesting phenomenon, not only in cell study itself, but also in application to biological elimination in aquatic environment for removing REE. Despite its remarkable ability to transport REE to the cell compartments, the transport mechanism is still not clear although there were indications that a calcium ion channel would play an important role from our previous studies. X-ray absorption fine structure experiments (XAFS) of cerium in Euglena gracilis were measured at Beijing Synchrotron Facility (BSRF) to directly determine the cerium valence state and coordination structure in situ. The absorption and fluorescence spectra of chlorophyll in the algae cell were measured as well for the cell loaded with REE ions. All the results indicated that most likely REE mainly located in chlorophyll molecules.