Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometric characterization of high molecular mass Starburst™ dendrimers

A series of Starburst (TM) polyamidoamine (PAMAM) dendrimers, built from a tetrafunctional ethylenediamine (EDA) core, generations 1 to 10 (G1-G10), and covering a wide range of charge state distributions (i.e. from m/z similar to 500 to m/z similar to 15000), have been investigated by electrospray ionization (ESI) Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. High resolution mass spectra for lower generation dendrimers (G1, M-r similar to 1429 u to G5, M-r similar to 28825 u) allowed characterization of the polydispersity of these systems, providing a basis for improving synthetic strategies and characterizing surface-modified dendrimers. The relationship between charge state in the gas phase and molecular mass of these spherical macromolecules is reported and used to estimate the stoichiometry of a G5 PAMAM dendrimer - polyclonal rabbit IgG immunoconjugate. The results presented herein represent the highest molecular mass species yet detected by FT-ICR MS with the exception of measurements based upon individual ion detection. (C) 1997 Elsevier Science B.V.