Calcium-coated chromosomes

We know that cations associate with DNA and help to neutralize the negative charges of phosphate groups, but for the most part the analysis of cation effects has not gone any further. Now Strick et al. demonstrate that calcium is distributed on chromosomes in a particular pattern that may implicate it in regulating a chromosomal protein and thus chromosomal structure (page 899).

The author's method of choice is secondary ion mass spectrometry (SIMS). Unlike previous X-ray–based techniques, SIMS yields the depth and localization information characteristic of the results from a confocal microscope. It does so by first using a laser to displace a thin, localized layer of the material under study, and then using mass spectrometry to analyze the displaced material. Strick et al. refine this technique to measure isotopes of a number...