Combination of Abundant Protein Depletion and Multi-Lectin Affinity Chromatography (M-LAC) for Plasma Protein Biomarker Discovery

We report on the development of a robust and relatively high-throughput method for in-depth proteomic
analysis of human plasma suitable for biomarker discovery. The method consists of depletion of albumin
and IgG and multi-lectin affinity chromatography (M-LAC), followed by nanoLC-MS/MS analysis of
digested proteins and label-free comparative quantitation of proteins. The performance of the method
is monitored by multiple quality control points to ensure reproducibility of the analysis. The method
identifies proteins that are reported to be present in normal plasma at concentrations of 10−100 ng/mL and that may be of particular interest when studying a variety of disease conditions. Numerous
tissue leakage proteins of potentially even lower concentrations are also identified. When the method
was used in a study to identify potential biomarkers of psoriasis, the differential abundance of proteins
present at low μg/mL level was quantitated and later verified by ELISA measurements.
Keywords: plasma • multi-lectin affinity chromatography (M-LAC) • abundant protein depletion • biomarker discovery
• ELISA