Measurement of soft X-ray absorption spectra and elemental analysis in local regions of mammalian cells using an electronic zooming tube.

Direct measurement of absorption spectra for minute areas (2 microns x 2 microns) in a dried mammalian cell was attempted using X-ray contact images of a whole cell. The wavelength region used ranged from 1.5 to 10nm covering the absorption edges of the major cellular elements. The measurements were achieved taking advantage of synchrotron radiation as a tuneable light source and an electronic zooming tube as an X-ray detector with a high spatial resolution. The spectra in every intracellular area exhibited marked absorption changes at the absorption edges of carbon, nitrogen and oxygen, while minor but significant changes for iron and calcium were observed, particularly in the cytoplasmic areas. These results reveal the different spatial distributions of the constituent elements in a cell.