EELS and EFTEM Analysis of Biological Materials

The high sensitivity of electron energy-loss spectroscopy (EELS) for detecting light elements at the nanoscale in the analytical electron microscope makes it a valuable technique for applications to biological materials [1]. In particular, EELS provides quantitative information about elemental distributions within subcellular compartments, and the number of specific atoms that are bound to individual macromolecular assemblies. EELS data can be acquired either in the fixed beam energyfiltered transmission electron microscope (EFTEM) or in the scanning transmission electron microscope (STEM), and recent progress in the development of both approaches has greatly expanded the range of applications for EELS analysis. Near single atom sensitivity is now achievable for certain elements bound to isolated macromolecules [2], and it has become possible to obtain three-dimensional compositional distributions from sectioned cells through EFTEM tomography [3].