e is a highly specialized mass spectrometer, which analyzes the mass of small molecular ions formed when a focused ion beam runs across the surface of a sample. ''You take everything in the beam's focal area, which is about 100 nanometers in diameter and about 10 nanometers deep for our experiment, and you obliterate it,'' Boxer said, explaining how the machine works. ''Then you sample the fragments by mass spectrometry. Then you move over and you go another 100 nanometers and you obliterate everything. And now you see if what's in each 100 nanometer region is the same or different from the next region. And so you just raster this beam across the surface, and by rastering over and over and over again, you build an image.''
Called NanoSIMS 50, the mass spectrometer is manufactured by Cameca Instruments of France and housed at LLNL. With a price tag of $3 million, it does a lot more than its cousins common in labs everywhere. It allows scientists to probe the composition of cell membranes with a higher resolution than light microscopy. By providing information about chemical composition of a sample, it fills a gap left by atomic force microscopy, which provides high-resolution information about topography, but not chemistry, as its microscope tip ''feels'' its way through samples. Plus it handles samples less ordered than those addressed by X-ray crystallography, which requires that samples be turned into crystals before analysis.
Geologists, cosmologists, materials scientists and engineers covet the machine for characterizing hard materials, such as rocks, space dust, polymers and nanoelectronics. But in the last five years, biologists have become interested in employing it to characterize components of biological samples on a length scale of 100 nanometers or less.
''There's currently no way to do that,'' Boxer said. ''You can't get more multidisciplinary than something like this. This is a big deal in terms of an analytical method with very
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Source:Stanford University
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