Quantitative analysis of mammalian chromosome by scanning transmission soft X-ray microscopy.

Soft X-ray spectromicroscopy was applied to study the quantitative distribution of DNA and protein in a mammalian chromosome at the spatial resolution of 100 nm. The quantities of DNA and protein were evaluated using 1s-π* transition in the NEXAFS spectra at the nitrogen K absorption edge. DNA was not uniformly distributed in the chromosome and DNA/protein ratio was less than 0.497. The present analysis revealed the clues to identify other molecules that contribute to the absorption spectrum of the sample. The results suggested that accumulation of the absorption spectra of relevant molecules would support the refinement of the analysis.