126927-53-5Relevant articles and documents
Cooperative binding by aggregated mono-6-(alkylamino)-β-cyclodextrins
Petter, Russell C.,Salek, Jeffrey S.,Sikorski, Christopher T.,Kumaravel,Lin, Fu-Tyan
, p. 3860 - 3868 (2007/10/02)
Mono-6-(hexadecylamino)-β-cyclodextrin (5) and mono-6-(octylamino)-β-cyclodextrin (4) have been titrated against organic guests (4-nitrophenol, 4-hydroxybenzoic acid, cyclohexanecarboxylic acid, etc.) in aqueous solution to give sigmoidal binding isotherms. Replotting of these data according to the Hill equation gives Hill coefficients > 1.0 (2.2 in the case of 5 and 4-nitrophenol). In contrast, both β-cyclodextrin (β-CD) and mono-6-amino-β-cyclodextrin (3) both exhibit hyperbolic binding isotherms, leading to Hill coefficients close to unity. Hill coefficients greater than one are the experimental hallmark of cooperativity, in which initial binding events render subsequent binding events more favorable. The degree of cooperativity is sensitive to the concentration of the hosts (4 and 5) and the solvent (cooperativity is suppressed in DMSO). These results are discussed in terms of the aggregation properties of the amphipathic hosts (cmc = 200 and 1.4 μM, for 4 and 5, respectively), which were studied by conductivity, dynamic light scattering, and NMR. Two possible mechanisms to account for the observed cooperativity are presented and discussed.
