title: Thiosquaramides: pH switchable anion transporters.
abstract: The transport of anions across cellular membranes is an important biological function governed by specialised proteins. In recent years, many small molecules have emerged that mimick the anion transport behaviour of these proteins, but only a few of these synthetic molecules also display the gating/switching behaviour seen in biological systems. A small series of thiosquaramides was synthesised and their pH-dependent chloride binding and anion transport behaviour was investigated using1H NMR titrations, single crystal X-ray diffraction and a variety of vesicle-based techniques. Spectrophotometric titrations and DFT calculations revealed that the thiosquaramides are significantly more acidic than their oxosquaramide analogues, with pKavalues between 4.0 and 9.0. This led to the observation that at pH 7.2 the anion transport ability of the thiosquaramides is fully switched OFF due to deprotonation of the receptor, but is completely switched ON at lower pH.
authors.affiliation: Chemistry, University of Southampton, Southampton, SO17 1BJ, UK.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Busschaert
authors.affiliation: School of Chemistry (F11), The University of Sydney, 2006 NSW, Australia.
authors.forename: Robert B P
authors.initials: RB
authors.lastname: Elmes
authors.affiliation: Chemistry, University of Southampton, Southampton, SO17 1BJ, UK.
authors.forename: Dawid D
authors.initials: DD
authors.lastname: Czech
authors.affiliation: Chemistry, University of Southampton, Southampton, SO17 1BJ, UK.
authors.forename: Xin
authors.initials: X
authors.lastname: Wu
authors.affiliation: Chemistry, University of Southampton, Southampton, SO17 1BJ, UK.
authors.forename: Isabelle L
authors.initials: IL
authors.lastname: Kirby
authors.affiliation: Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, 46556, USA.
authors.forename: Evan M
authors.initials: EM
authors.lastname: Peck
authors.affiliation: Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, 46556, USA.
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Hendzel
authors.affiliation: Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, 46556, USA.
authors.forename: Scott K
authors.initials: SK
authors.lastname: Shaw
authors.affiliation: School of Chemistry (F11), The University of Sydney, 2006 NSW, Australia.
authors.forename: Bun
authors.initials: B
authors.lastname: Chan
authors.affiliation: Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, 46556, USA.
authors.forename: Bradley D
authors.initials: BD
authors.lastname: Smith
authors.affiliation: School of Chemistry (F11), The University of Sydney, 2006 NSW, Australia.
authors.forename: Katrina A
authors.initials: KA
authors.lastname: Jolliffe
authors.affiliation: Chemistry, University of Southampton, Southampton, SO17 1BJ, UK ; Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Gale