Characterization and sequence confirmation of unnatural amino acid containing peptide libraries using electrospray...

The content of 24 12-membered heptapeptide libraries was investigated using capillary liquid chromatography coupled with an electrospray ionization quadrupole orthogonal acceleration time-of-flight mass spectrometer. Adjustment of the chromatographic parameters led to the separation of most of the components. Extraction of the [M + 2H]2+ ions allowed us to demonstrate the presence of all expected species in the library and to evaluate their relative abundance in the mixture. Rapid sequence confirmation was achieved by subtraction of product ion spectra, a way to eliminate common ions and to simplify the spectra for interpretation. This technique can also easily be applied to other libraries consisting of components with a common core.