EVALUATION OF LC-ESI/LC-MALDI IN THE ANALYSIS OF PHOTOSYSTEM I AND II COMPLEX OF BARLEY

A nanoACQUITY UPLC TM system (Waters, Milford, MA) was used for the chromatographic separation, both for the on-line (ESI) and off-line MALDI experiments, with identical LC conditions. The Photosystem I and II tryptic digest was diluted 1:10 in 0.1% formic acid, and 4 µL of the diluted sample loaded. Trapping column: Symmetry C18 (5µm)180 µm x 20 mm column (Waters, Milford, MA) Analytical column: BEH C18 (1.7µm) 75 µm x 100 mm column (Waters, Milford, MA), flow rate of300 nL/min For off-line sample preparation, the eluent from the analytical column was depoisted onto a MALDI target plate using a CTC-MALDI spotting robot (CTC, Basel, CH). The eluent was mixed in a Y connector with α-cyano-4hydroxycinnamic acid (CHCA) matrix solution (2 mg/mL in 1:1 MeCN:0.1% TFA), with a spotting time of 40 seconds per spot. The on-line and off-line experiments were performed in triplicate.