Quantitative peptide analysis by mass spectrometry

摘要

The invention relates to an accurate and safe determination of peptide concentrations in solutions by mass spectrometry using internal reference substances, determining the concentration ratio of a target peptide to a reference peptide by forming the ratio of the integrated ion currents of the complete isotope peak groups instead of only comparing single ion peaks. To obtain the integrated ion current of an isotope peak group, the invention applies a curve fitting method, fitting a family of bell-shaped curves with correct isotope distribution to the measured peak groups. The reference peptide must be chemically identical with the target peptide, but isotopically marked. It is a great advantage over other analysis methods, that the curve fitting delivers additionally individual quality indicators for each analysis, proving absence of any superposition of ion peaks of other substances, proving the measurement of the correct target peptide, and proving failure-free instrument adjustment and operation. A further quality confirmation may be obtained by a joint measurement of a reporter fragment ion spectrum of target and reference peptide.