An Anion Selective Aminocyclodextrin Ion Channel: Ion Selectivity, pH Sensitivity and Potential as a Scaffold for Light Gating
Madhavan, Nandita
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https://hdl.handle.net/2142/84226
Description
Title
An Anion Selective Aminocyclodextrin Ion Channel: Ion Selectivity, pH Sensitivity and Potential as a Scaffold for Light Gating
Author(s)
Madhavan, Nandita
Issue Date
2006
Doctoral Committee Chair(s)
Mary S. Gin
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Organic
Language
eng
Abstract
The synthesis and characterization of a highly active ion channel mimic and a photocleavable tether as a potential light activated switch is described. Signal activated ion channels are attractive for use in applications such as biosensors and nano-switches. A new photocleavable o-nitrobenzyl dimeric tether has been developed as a potential trigger for the photoactivation of the ion channel. The utility of the tether was demonstrated by functionalizing primary, secondary and benzylic alcohols with the tether and subjecting the resulting ethers to photolysis. The photolysis of the tethered ethers was found to be extremely efficient and the corresponding alcohols were isolated in 79-100% yields. Comparison with the corresponding monomeric ethers indicated superior yields for the ethers functionalized with the dimeric tether. An aminocyclodextrin ion channel was synthesized from heptaiodinated beta-cyclodextrin and amine functionalized pentabutylene glycol chains. Ion transport through the channel gauged using 23Na NMR and fluorescence spectroscopy indicated high ion transport activity, comparable to natural ion channels. The fluorescence studies also indicated that the ion channel was highly anion selective with anion transport rates being ClO4- > I- > NO3- > Br- > Cl-. The rates for the transport of ClO4 -, I-, NO3- and Br- ions were ca. 20, 9, 3.1 and 2.6 times that for Na + ions, respectively. The anion selectivity for the ion channel is attributed to the presence of seven amino groups conferring positive charge at the pore opening of the ion channel. The ion transport rates and the ion selectivity of the ion channel were found to be pH dependent. At high pH values fast transport rates for Na+ and X- ions was demonstrated, while at low pH higher selectivity between ions was observed.
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