Explorative Study of the Protein Composition of Amniotic Fluid by Liquid Chromatography Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

To explore the suitability of FTICR mass spectrometry for the analysis of the protein composition of amniotic fluid (AF), an AF sample from 15 weeks gestation from a healthy 36-year-old woman was tryptically digested, with or without prior serum albumin removal. The tryptic peptides were separated by gradient capillary liquid chromatography (LC) followed by electrospray ionization (ESI) and mass spectrometric detection with a 9.4 T Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR). The obtained data underwent computer-aided mathematical and statistical evaluation to extract significant tryptic peptide patterns from human proteins. Forty-three proteins were putatively identified; among them were known protein constituents of amniotic fluid, but also many that not have been detected before. The removal of serum albumin prior to tryptic digestion reduced ion suppression from abundant HSA fragments. The protein analysis of amniotic fluid by albumin removal, tryptic digestion and LC/FT-ICR−MS analysis was found to be a straightforward technique.