Electrospray voltage was set to 2,000 V, applied at the end of the analytical column to stainless steel needle from Pepsep (Odense, Denmark) and was inserted in a custom holder for Valco (Houston, TX) liquid junction that is available from ESI Source Solution (Woburn, MA). To reduce common laboratory atmospheric background ions and enhance peptide signal to single charged general noise ratio, an ABIRD (Active Background Ion Reduction Device by ESI Source Solutions, Woburn MA) was used at the nano spray interface. The temperature of ion transfer tube was 275 degrees Celsius and the S-lens RF level set to 60. After a precursor scan from 400 to 1400 m/z at 120,000 resolving power, MS2 method with the top 10 most intense precursor ions with charges 2 to 4 and above the AGC min threshold 10,000 were isolated for MS2 analysis via a 0.8 Th isolation window with offset settled to 0.3 Th. These ions were accumulated for at most 100ms. Then they were fragmented via HCD at a normalized collision energy of 34 eV and MS2 spectra were detected at 60,000 resolving power. Dynamic exclusion was used with a duration of 60 seconds with a mass tolerance of +/-5 ppm. Raw MS data Raw data were searched by Proteome Discoverer 2.4 with Bionic 3.5 node against protein sequence database including all entries from the Human SwissProt database (downloaded January 2018; 20,197 entries) and with a home curated contaminants database containing proteins such as human keratins and common lab contaminants.