NMR spectroscopic investigation of inclusion complexes between cyclodextrins and the neurotoxin tetramethylenedisulfotetramine.

The binding stoichiometry, strength and structure of inclusion complexes formed between the neurotoxin tetramethylenedisulfotetramine (TETS) and both native and modified cyclodextrins (CyDs) were investigated using nuclear magnetic resonance (NMR) spectroscopy. Of all six examined cases, native β-cyclodextrin (β-CyD) and its chemically modified counterpart heptakis-(2,3,6-tris-(2-hydroxypropyl))-β-cyclodextrin (2HP-β-CyD) were found to associate most strongly with TETS as reflected in the magnitude of their binding constants (K = 537 ± 26 M(-1) for β-CyD and K = 514 ± 49 M(-1) for 2HP-β-CyD). Two-dimensional rotating-frame Overhauser effect spectroscopy NMR experiments confirm close proximity of the TETS molecule to both β-CyD and 2HP-β-CyD as intermolecular, through-space interactions between the H3 and H5 protons located in the interior of the CyD cavity and the methylene protons of TETS were identified.