Qualitative and quantitative screening of amino acids in plant tissues

The comprehensive analysis of metabolites (metabolomics) and expressed proteins (proteomics) in any given biological system forms the center of modern efforts to define the critical functions of biological systems. Because amino acids play important roles in primary and secondary metabolic pathways as well as serving as the building blocks of proteins, they have been important targets for efforts at metabolic profiling. Amino acids have been analyzed using a number of procedures, including separation by high performance liquid chromatography (HPLC), gas chromatography (GC), liquid chromatography (LC), and capillary electrophoresis (CE). Mass spectrometry (MS) remains the primary analytical and detection system for metabolic profiling, including amino acid analysis, due to its accuracy and the information content obtained by such analyses, which facilitates the identification and measurement of large numbers of biomolecules. MS methods also add the capability of monitoring isotope distributions of molecules for metabolic flux analysis. Here we describe a GC-MS method that is suitable for analysis of amino acids in sub-milligram quantities of fresh plant material and that is easily adapted to high-throughput screening approaches.