| Popis: |
For cancer research, serum and plasma are especially attractive sample types as collection of blood is common, simple and only minimally invasive. Yet serum samples can offer unique challenges in LC-MS proteomic analyses. The two biggest challenges being: 1) the high abundance of Albumin accounting for about 50% of the total protein mass and, 2) proteolytic resistance, in large part due to substantial amount of glycoprotein, a modification that manifests proteolytic resistance. In this short report, we describe new methods using a surface/bead based product, AlbuVoid™, which depletes Albumin through a negative selection or voidance strategy, retaining the vast amount of the remaining serum proteome on the bead. We then combine this novel enrichment, with a direct and seamless integration with Trypsin digestion, a method conventionally referred to as on-bead digestion. We evaluated the digestion time as a parameter to identify whether different sub-populations of peptides and proteins can be observed by LC-MS analyses. Using 2 different allotted digestion times - 4 hours, and overnight, each with a singular 3 hour gradient LC-MS run, between 400-500 total proteins were observed for both human and rat sera, with overlapping and distinct sub-populations observable at each digest time. These results support that the described methods gain efficiencies over other high abundance depletion and in-solution digestion workflows. We solicit that such workflows will minimize many of the inconsistencies of proteolytic hydrolysis for both discovery and quantitative serum proteomic applications. |
