Mass spectrometric quantification of neuropeptides.

The molecular specificity of MS/MS methods for the accurate quantification of endogenous neuropeptides, such as ME and BE, exceeds that of all other methods because: 1. MS/MS qualitative analysis first establishes the amino acid sequence of the endogenous peptide; 2. MS/MS establishes and maintains the structural link between the (M + H)+ ion and its corresponding amino acid sequence-determining ion(s) during quantification; and 3. A stable isotope-incorporated synthetic peptide internal standard is used. Endogenous ME and BE have been measured in human pituitary tissue by this quantitative analytical MS method.