Abstract
Isotope substitution plays an important role in bio-molecular structure elucidation by NMR spectroscopy.The ability to measure isotope enrichment is essentialto the development of an effective procedure for isotopeincorporation. Gas chromatography coupled to massspectrometry (GC/MS) is a commonly used techniquefor the analysis of the isotopic composition of a protein(1). However, the technique is tedious because it in-volves protein extraction, hydrolysis, and amino acidderivatization prior to GC/MS analysis.We have demonstrated that MALDI–TOF massspectrometry is a simple, accurate, and fast methodfor monitoring isotope incorporation in photosyntheticorganisms.