Ultra performance liquid chromatography (ULC) grade solvents were used for all chromatographic
steps. Protein (2 mg) from each sample was loaded using split-less nano-ULC (10 kpsi nanoAcquity,
Waters). The mobile phase consisted of: (A) H2Oþ0.1% formic acid and (B) acetonitrileþ0.1% formic
acid. Desalting of the samples was performed online using a reversed-phase C18 trapping column
(180 mm internal diameter, 20 mm length, 5 mm particle size; Waters). The peptides were then
separated using a an HSS T3 nano-column (75 mm internal diameter, 250 mm length, 1.8 mm particle
size; Waters) at 0.35 mL/min. Peptides were eluted from the column using the following gradient: 4–
35% B in 150 min, 35–90% B in 5 min, maintained at 90% for 5 min and then back to initial conditions.