Evidence for the formation of gas-phase inclusion complexes with cyclodextrins and amino acids

Experimental and theoretical evidence is provided that indicates the presence of inclusion complexes in the gas phase when cyclodextrin and amino acid mixtures are electrosprayed into a Fourier transform mass spectrometer. A guest exchange reaction that is enantiospecific is used to probe the structure of the gas-phase complex. Chiral selectivity is affected by both the size of the guest and the size of the cavity. These observations are based on a selected number of amino acids with various hosts. The experimental results are supported by molecular dynamics calculations. We further conclude that rather than nonspecific complexes, amino acid-cyclodextrin complexes produced in solution maintain the included structure even in the gas phase.