Seeing and Measuring Stable Isotope Tags in Subcellular Domains with Ion Microscopy

Abstract

Multi-isotope Imaging Mass Spectrometry (MIMS) is the combination of an ion microscope-secondary ion mass spectrometer with tracer methods and intensive quantitative image analysis. MIMS allows one to image the distribution and to measure the accumulation of molecules labelled with stable or radioactive isotopes within subcellular domains in volume smaller than 1 cubic micron. The lateral resolution is better than 30 nm, and the depth resolution is a few atomic layers. Up to seven quantitative atomic mass images (or tags) can be recorded simultaneously. A whole cell can be studied layer-after-layer and rendered in quantitative 3D.MIMS can provide unique information in almost all fields of biomedical research, particularly in two broad areas: 1. metabolic turnover (protein, lipids and sugars in sub-cellular domains using as precursors for example 15N-labeled amino-acids or 13C labeled fatty acids) 2. cell lineage ( tracking individual cells within large populations by labelingDNA, for example with 15N thymidine for the salvage pathway and 18O for the de novo pathway).Because stable isotopes are integral part of living organisms, they are not toxic. This allows one to label DNA with a stable isotope precursors for period of time that could reach years. And, this allows applications of MIMS to human.