Advancing the sensitivity of selected reaction monitoring‐based targeted quantitative proteomics

Abstract

Selected reaction monitoring (SRM) – also known as multiple reaction monitoring (MRM) – has emerged as a promising high‐throughput targeted protein quantification technology for candidate biomarker verification and systems biology applications. A major bottleneck for current SRM technology, however, is insufficient sensitivity for, e.g. detecting low‐abundance biomarkers likely present at the low ng/mL to pg/mL range in human blood plasma or serum, or extremely low‐abundance signaling proteins in cells or tissues. Herein, we review recent advances in methods and technologies, including front‐end immunoaffinity depletion, fractionation, selective enrichment of target proteins/peptides including posttranslational modifications, as well as advances in MS instrumentation which have significantly enhanced the overall sensitivity of SRM assays and enabled the detection of low‐abundance proteins at low‐ to sub‐ng/mL level in human blood plasma or serum. General perspectives on the potential of achieving sufficient sensitivity for detection of pg/mL level proteins in plasma are also discussed.