Evaluation of plasma peptides extraction methods by high-resolution mass spectrometry.

Monitoring of peptides offers a promising approach for the discovery of novel biomarkers, which might be valuable for detection, treatment and prevention of large variety of diseases. Development of highly effective methods for plasma peptide extraction remains an important task. In the current study, we applied different types of plasma peptide extraction approaches to reveal efficient methods which would provide the highest peptide yield. We used different combinations of plasma treatment with acetonitrile and/or urea/guanidine, protein precipitation by acetone, gel-filtration, ultrafiltration, and two types of solid phase extraction. The extracted peptides were analyzed by LC-MS/MS. The obtained results suggest that several methods, including differential solubilization, organic precipitation, as well as some variants of ultrafiltration and solid phase extraction, provide effective plasma peptide enrichment convenient for further LC-MS/MS analysis. Alas, most of the identified peptides were extracted by only one of the applied methods. Hence, it seems reasonable to consider several methods to increase the possibility of novel biomarker discovery.