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Mapping isotopically labeled alanine Electron microscopy of organic materials must avoid the destructive effects of electron beam impact. One approach is to measure vibrational spectra with electron energy-loss spectroscopy in a mode where the electron beam grazes the sample and couples to it through evanescent modes. Hachtel et al. used such methods to probe carbon-12– and carbon-13–labeled alanine crystals, which exhibited an isotopic shift in the asymmetric carbon-oxygen stretching mode. They used this property to map the distribution of labeled clusters of alanine on length scales of tens of nanometers. Science , this issue p. 525
Hachtel et al. (Fri,) studied this question.