Functional genomics is not just restricted to mRNA identification and dosage. Progress in two-dimensional gel electrophoresis makes it possible to prepare an inventory, or fingerprint, of the protein composition of individual tissues. Often, the amount of protein detected is high enough to obtain amino acid sequences from some of the peptides of these proteins and in this way it is possible to identify the enzyme or protein present in such a gel spot. The new classes of tabletop mass spectrometers now available permits detection sensitivities down to the femtomole level as well as simultaneous N- and C-terminal sequencing of protein-derived peptides within minutes, rather than hours, as is the case with the traditional Edman-based N-terminal sequencing.
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