Quantification of Proteins and Metabolites by Mass Spectrometry without Isotopic Labeling or Spiked Standards

TLDR

This biotechnology enables differential expression measurements and the discovery of biological markers. The study presents a new LC‑MS method for quantifying proteomic and metabolomic profiles using electrospray ionization. The approach employs human serum (applicable to any fluid or tissue), relies on linear signal‑concentration relationships and reproducible sample processing, and requires no isotopic labeling or similar standards. Linear standard curves were obtained for many compounds in human serum, and median coefficients of variation of 25.7 % (proteome) and 23.8 % (metabolome) were achieved across ~3,400 ions in 25 samples, totaling 85,000 measurements.

Abstract

A new method is presented for quantifying proteomic and metabolomic profile data by liquid chromatography-mass spectrometry (LC-MS) with electrospray ionization. This biotechnology provides differential expression measurements and enables the discovery of biological markers (biomarkers). Work presented here uses human serum but is applicable to any fluid or tissue. The approach relies on linearity of signal versus molecular concentration and reproducibility of sample processing. There is no use of isotopic labeling or chemically similar standard materials. Linear standard curves are reported for a variety of compounds introduced into human serum. As a measure of analytical reproducibility for proteome and metabolome sampling, median coefficients of variation of 25.7 and 23.8%, respectively, were determined for approximately 3400 molecular ions (not counting their numerous isotopes) from 25 independently processed human serum samples, corresponding to a total of 85000 individual molecular ion measurements.