Protein identifications from a representative xylem sap 2-DE gel. Representative 2-DE gel of xylem sap proteins from 12-week-old Brassica napus plants. Proteins were identified by partial sequences determined by tandem mass spectrometry. Numbers indicate spots from which proteins could be identified. Sequences and identifications are listed in Table 1. Asterisks indicate spots that were analyzed but led to no or low quality mass spectra that did not allow protein identifications. Molecular masses in kD are indicated on the right hand side of the gel.