SnapShot: Mass Spectrometry for Protein and Proteome Analyses

Quantify proteins without stable isotopes Label-free quantifi cation Quantitative data are derived from the number of MS/ MS spectra per peptide (spectral counting) or the integrated peak area of the ion chromatogram of a specifi c peptide. Generally considered less accurate than isotope-based methods but does not require expensive labeling reagents; method of choice for large numbers of samples; also used for estimating absolute protein quantities in a sample. Compatible with all acquisition methods.