Matrix-assisted laser desorption mass spectrometry of biotransformation products of dynorphin a in vitro.

The utility of matrix-assisted laser desorption mass spectrometry for characterizing products of in vitro processing of synthetic dynorphin A (Dyn A) peptides in biologic matrices is described. A series of laser desorption matrices were tested for their response to Dyn A (1-6), Dyn A (1-7), Dyn A (1-8), Dyn A (1-9), Dyn A (1-l0), Dyn A (1-13), Dyn A (2-17), and Dyn A (1-17). α-Cyano-4-hydroxycinnamic acid was chosen as a suitable matrix for subsequent studies. Mass spectra of dynorphin peptides indicated a good signal-to-noise response down to (1) 10 fmole of Dyn A (1-10) amide standard in aqueous acidic solution and (2) a concentration of 10(-7) M for seven dynorphin peptides spiked into human plasma. Two examples of the mass spectrometric analysis of the products of in vitro processing are presented: Dyn A (1-13) and Dyn A (1-17) in human blood. The presence and identity of processed peptides can be simply inferred from the molecular masses provided by the mass spectrometric measurement without extensive sample purification. A comparison of matrixassisted laser desorption mass spectrometry is made with high-performance liquid chromatography.