Thermo-Finnigan, USA) and a LTQ Orbitrap mass spectrometer
(Thermo Scientific, Bremen, Germany). The molecules were separated
on a C18 LichroCART (250 mm × 4.6 mm) column (Merck,
Germany) using the following mobile phase: (A) water formic acid
0.1% and (B) MeOH, acetonitrile, formic acid (50/50/0.1). LC separation
consisted in an isocratic step at 1% of B for 2 min followed by
a linear gradient from 1% to 40% of B in 100 min, then to 70% of B in
25 min and 90% of B in 55 min with a flow rate at 700 l/min. The
mass spectrometer conditions and data processing were the same
as described in Chougui et al. (2013).