Investigation of Noncovalent Complexes Between β-Cyclodextrin and Polyamide Acids Containing N-Methylpyrrole and N-Methylimidazole by Electrospray Ionization Mass Spectrometry

Electrospray ionization (ESI) mass spectrometry was utilized to investigate noncovalent complexes between β-cyclodextrin (β-CD) and five novel polyamide acids containing N-methylpyrrole and N-methylimidazole. The 1:1 binding mode was specified by examining the binding stoichiometry from ESI mass spectra. It found that polyamide acids with β-CD have binding affinities in the order: ImImImβCOOH > ImPyImβCOOH > ImPyPyβCOOH > PyPyPyβCOOH > NO2PyPyPyβCOOH. The method gives, simultaneously, the binding constants between β-CD and polyamide acids based on a novel linear equation.