Organic ion imaging of biological tissue with secondary ion mass spectrometry and matrix-assisted laser desorption/ionization

Organic secondary ion mass spectrometry (SIMS) and matrix-assisted laser de sorption/ionization (MALDI) mass spectrometry can be used to produce molecu lar images of samples. This is achieved through ionization from a clearly i dentified point on a flat sample, and performing a raster of the sample by moving the point of ionization over the sample surface. The unique analytic al capabilities of mass spectrometry for mapping a variety of biological sa mples at the tissue level are discussed. SIMS provides information on the s patial distribution of the elements and low molecular mass compounds as wel l as molecular structures on these compounds, while MALDI yields spatial in formation about higher molecular mass compounds, including their distributi ons in tissues at very low levels, as well as information on the molecular structures of these compounds. Application of these methods to analytical p roblems requires appropriate instrumentation, sample preparation methodolog y, and a data presentation usually in a three-coordinate plot where x and y are physical dimensions of the sample and z is the signal amplitude. The u se of imaging mass spectrometry is illustrated with several biological syst ems. Copyright (C) 2001 John Wiley & Sons, Ltd.