Dependence of cyclo amylose substrate binding on charge
Bergeron, R.J.; Channing, M.A.; Mcgovern, K.A.
Journal of the American Chemical Society 100(9): 2878-2883
ISSN/ISBN: 0002-7863 Accession: 005106801
The direction of sodium benzoate and benzoic acid penetration of the cyclohexaamylose cavity in aqueous solution is determined by a 1H NMR study of the respective cycloamylose complexes. Chemical-shift changes in the host and guest molecules, as well as a strong intermolecular nuclear Overhauser effect, suggest that benzoic acid has a strong orientational preference for binding in the cycloamylose cavity, while sodium benzoate binding is somewhat more random. Both benzoic acid and sodium benzoate form 1:1 AB complexes with cyclohexaamylose, and the benzoic acid generates conformational changes in the cyclic oligosaccharide's glucose rings. The dependence of cycloamylose-substrate binding on charge is discussed in terms of the energy required to move a charged species from a medium of high dielectric to a medium of low dielectric. This insertion energy is approximated from free energy of solution studies. [Cycloamyloses have been studied frequently as enzyme active-site models.].