The chemical compositions of organelles within cells, and the relationship of the chemical compositions to the organelle morphologies and functions, are key for understanding biochemical processes in healthy and diseased cells. However, progress in the field has been hampered by limitations of the techniques commonly used for chemical analysis. Macro-analytical techniques analyze a large number of organelles of certain type, so the results represent the average composition of a population of organelles and cannot reveal compositional differences between single organelles. Most relevant micro-analytical techniques lack the required spatial resolution and/or elemental detection sensitivity to measure the chemical compositions of single organelles, including trace elements, with the exception of the nucleus.
To address this issue, a collaboration of researchers from Argonne National Laboratory, Northwestern University, University of Chicago and Yoav Kashiv of the Physics Department at University of Notre Dame combined the highest available spatial resolution nano-synchrotron X-ray fluorescence (nano-SXRF) with transmission electron microscopy (TEM) and improved sample preparation protocol to image the natural trace element distributions between single organelles in cells. Detected elements include Cl, K, Ca, Co, Ni, Cu, Zn and Cd (which some cells were supplemented with). The method opens up new possibilities in subcellular biochemistry for studying variabilities among single organelles and other subcellular compartments, which are usually analyzed at the organelle population level. It could be applied to any type of cell to address a wide range of issues relating to the impact of chemical composition on cell function.
Kashiv, Y. et al. Imaging trace element distributions in single organelles and subcellular features. Sci. Rep. 6, 21437; doi: 10.1038/srep21437 (2016).
Dr. Yoav Kashiv is a Visiting Scholar in the Department of Physics.