"This method allows us to see what has never been seen before, and to measure what has never before been measured," Lechene says. "Imagine looking into a building, slice by slice. You can see not only that it contains apartments, but also that each apartment contains a refrigerator. You can see that there are tomatoes in the refrigerator of one apartment, and potatoes in the refrigerator of another. You can count how many there are and measure how fast they are used and replaced. It is this level of resolution and quantification that MIMS makes possible within cells."
Lechene, of Harvard Medical School and Brigham and Women's Hospital in the US, worked with colleagues from around the world to develop and test the new methodology.
A beam of ions is used to bombard the surface atoms of the biological sample, and a fraction of the atoms are emitted and ionized. These "secondary ions" can then be manipulated with ion optics ?in the way lenses and prisms manipulate visible light - to create an atomic mass image of the sample. Lechene et al. developed MIMS by combining the use of a novel secondary-ion mass spectrometer developed by Georges Slodzian, from the Université Paris-Sud in France, labeling with stable isotopes and building quantitative image-analysis software.
MIMS can generate quantitative, three-dimensional images of proteins, DNA