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Orientational Effect of Surface-Confined Cyclodextrin on the Inclusion of Bisphenols

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journal contribution
posted on 15.02.2005, 00:00 by Hiroshi Endo, Tadashi Nakaji-Hirabayashi, Shinta Morokoshi, Makoto Gemmei-Ide, Hiromi Kitano
The molecular recognition of various kinds of bisphenols (BPs) and a bisphenol A−polymer conjugate (BPA−polymer) by a self-assembled monolayer (SAM) of thiolated β-cyclodextrin (CD) on a gold electrode was examined using cyclic voltammetry (CV). Based on the inhibitory effect of BPs on the inclusion of hydroquinone (HQ) as a probe by the surface-confined CD, the association constants (Kassoc) of BPs with the immobilized β-CD were estimated. The Kassoc values for BPs with the SAM of 3-dithiobis(undecanoylamido)-3-deoxy-β-cyclodextrin (DTUA-β-CD) were smaller than those in the free β-CD system reported previously. A similar tendency was obtained when 6-(lipoylamido)-6-deoxy-β-cyclodextrin (LP-β-CD) was used in place of DTUA-β-CD. The Kassoc values for all the BPs except for bisphenol B with the SAM of LP-β-CD were always larger than those with the SAM of DTUA-β-CD, due to a difference in the orientation of the β-CD moiety in the SAMs. Furthermore, adsorption and desorption processes of the BPA−polymer from the surface-confined β-CD was followed using local surface plasmon resonance spectroscopy.