Evaluation and determination of the cyclofructans–amino acid complex binding pattern by electrospray ionization mass spectrometry

The noncovalent complex interactions between cyclofructans, a new class of cyclic oligosaccharide hosts, and various amino acids have been characterized by means of electrospray ionization mass spectrometry and nuclear magnetic resonance. The 1 : 1 stoichiometry of cyclofructans and amino acid complexes was confirmed by their mass‐to‐charge ratio in positive mode. Cyclofructans (CFs)–amino acid complexes and cyclodextrin–amino acid complexes exhibited distinctive different fragment behaviors in collision‐induced dissociation experiments. Coupled with the results of ¹H NMR and nuclear overhauser effect spectroscopy, cyclofructan–amino acid complexes were deduced to be rim complexes via formation hydrogen bonding and ion–dipole forces. The interaction pattern could be controlled by changing the pH condition. In neutral solution, amino acids are located on the positive side of CFs, although moved to the negative side pocket constructed by 3‐OH oxygen of furanose ring and the crown ether oxygen in acid condition. In addition, theory calculation for geometry optimization of Trp and CFs was performed, which was in good agreement with the experimental results. Copyright © 2014 John Wiley & Sons, Ltd.