Nanoelectrospray ion mobility spectrometry and ion trap mass spectrometry studies of the non-covalent complexes of amino acids and peptides with polyethers

The non-covalent complexes formed between cyclic (e.g., 12-crown-4 (12C4), 15-crown-5 (15C5), and 18-crown-6 (18C6)) and acyclic (e.g., triglyme and tetraglyme) polyethers with amino acids (histidine and arginine) and peptides (MRFA, WAR, gp70 and bradykinin) have been analysed by atmospheric pressure nano-electrospray ionisation (nano-ESI) ion mobility spectrometry and ion trap mass spectrometry. The reduced mobilities for these complexes are reported and correlate well with the mass and size of the polyether. The ability of IMS to distinguish between cyclic and acyclic polyethers and their complexes with biomolecules, based on differences in their reduced mobilities, is demonstrated. These differences are attributed to variations in the collision cross-section arising from subtle changes in conformation in these ligand-receptor complexes. (C) 2003 Elsevier B.V. All rights reserved.