Studies of peptide binding to allyl amine and vinyl acetic acid-modified polymers using matrix-assisted laser desorption ionization mass spectrometry

Previous studies have shown that increases in surface-peptide binding affin ity result in decreases in peptide matrix-assisted laser desorption/ionizat ion (MALDI) mass spectrometry (MS) ion signals. The present work demonstrat es that, with appropriate corrections for peptide ionization efficiency und er MALDI conditions, relative surface-peptide binding affinities can be ass ayed using the MALDI MS methodology. Peptides with a range of pi values are allowed to interact with amine-modified and carboxylic acid-modified polym er surfaces (produced by pulsed radiofrequency plasma polymerization of all yl amine and vinyl acetic acid) in buffered solutions of neutral pH. Becaus e of the net positive and negative charges associated with the peptides and surfaces in solution, both electrostatic and hydrophilic interactions play a role in the surface-peptide interaction. Consistent with expectations, t he peptide MALDI ion signals far peptides with net negative charges in solu tion are smaller than those for peptides with net positive charges in solut ion when the peptides are allowed to interact with positively charged surfa ces. A reversal of the relative peptide MALDI ion signal intensities is obs erved when the same peptides are allowed to interact with negatively charge d surfaces. Cumulatively, the results demonstrate that even modest changes in surface-peptide interactions can be comparatively probed by MALDI mass s pectrometry. (C) 1999 Academic Press.