Subsequent to enrichment and purification through the Zip-Tip pipette tips, peptide mixtures were dissolved in 0.5 mL of CHCA matrix solution (5 mg/mL CHCA in 50% ACN/0.1% TFA) and spotted onto a freshly cleaned MALDI target plate. Spots were allowed to dry for 30 mins at room temperature. After air drying, the crystallized spots were analysed using a 4800 MALDI-TOF/ TOF mass spectrometer (AB Sciex, Framingham, MA) linked to 4000 series explorer software (version 3.5.3). All mass spectra were recorded in a reflector mode within a mass range from 800 to 4000 Da, using a Nd:YAG 355 nm laser. The acceleration voltage and extraction voltage were kept at 20 kV and 18 kV respectively. Six point calibration of the instrument was automatically performed by a peptide standard Kit (AB Sciex) that included des-Arg1-bradykinin (m/z 904.468), Angiotensin I (m/z 1296.685), Glu1-fibrinopeptide B (m/z 1570.677), ACTH (18-39, m/z 2465.199), ACTH (1-17, m/z 2903.087), and ACTH (7-38, m/z 3657.923). All the MS spectra were obtained from accumulation of 900 shots. MS/MS spectra were acquired for the 15 most abundant precursor ions, with a total accumulation of 1500 laser shots and collision energy of 1 kV. Once the MS survey scans were completed, the data were processed to generate a list of precursor ions for interrogation by MS/MS. The combined MS and MS/ MS peak lists were searched using the GPS TM Explorer software version 3.6 (AB Sciex). Protein identification was performed by MS/MS ion search using MASCOT version 2.1 (http://www. martixscience.com) search engine against the Swiss-Prot database. Searches were carried out with the following parameters; all entries taxonomy, trypsin digestion with one missed cleavage, fixed modifications: carbamidomethylation of cysteine residues, variable modifications: oxidation of methionine residues, mass tolerance 150 ppm for MS and 0.4 Da for MS/MS. Identified proteins having at least two unique matched peptides were selected for further analysis. We have reported only those proteins with a protein identification confidence interval of $95%.