Estimates of protein surface areas in solution by electrospray ionization mass spectrometry.

The extent of multiple charging of protein ions in electrospray ionization (ESI) mass spectra depends on the solvent-exposed surface area, but it may also be influenced by a variety of other extrinsic and intrinsic factors. Gas-phase ion chemistry (charge-transfer and charge-partitioning reactions) appears to be the major extrinsic factor influencing the extent of protonation as detected by ESI MS. In this work, we demonstrate that under carefully controlled conditions, which limit the occurrence of the charge-transfer reactions in the gas phase, charge-state distributions of protein ions can be used to assess the solvent-exposed surface area in solution.

A chemometric approach to detection and characterization of multiple protein conformers in solution using electrospray ionization mass spectrometry.

Protein ion charge state distributions in electrospray ionization mass spectra have a potential to provide a wealth of information on protein dynamics, because they contain contributions from all protein conformers present in solution. Such ionic contributions often overlap, limiting the amount of useful information that can be extracted from the spectra. This difficulty is overcome in the present work by using a chemometric approach, which allows spectral deconvolution to be carried out and information on individual protein conformers to be extracted.