Structure–activity relationships in linear oligoester ion-channels

Abstract

The ion transport activity of eighteen linear oligoesters was assessed using a quantitative fluorescence assay to monitor the collapse of a pH gradient across a vesicle bilayer membrane. Significant activity was associated with compounds that have extended lengths comparable to the thickness of the bilayer membrane, and with the most hydrophilic members of the compounds surveyed. Substantial differences in activity between constitutional isomers were also observed. The aggregation of active compounds in aqueous solution was detected by a pyrene fluorescence probe, and subsequently detected as a rate-limiting step in a sequential vesicle experiment.

Design, Synthesis and Characterisation of Guanosine‐Based Amphiphiles

“…However, the excitation wavelength of the acidic form (403 nm) is significantly different from that of the conjugate-base form (460 nm) so that the acid/base ratio is directly reflected in the emission intensity modulation produced by alternating excitation at the two wavelengths. [24] In essence, the modulated emission signal, obtained by cycling the excitation wavelength and recording the emission at 510 nm, reports the effective pH within the liposome. An increase in HPTS fluorescence emission indicates basification of the liposome inner water pools that may be correlated to H + /OH À transportation and to the associated cation/anion symport or antiport.…”

Photocontrol of ion permeation in lipid vesicles with amphiphilic dithienylethenes

“…The photocontrol of ion permeability for lipid vesicles incorporating DTEs 1-3 was assessed using a common ratiometric fluorescence technique 37,38 in which these vesicles are encapsulated with a pH-sensitive fluorophore, 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS), during their preparation. The fluorescence of these vesicles is stable prior to the injection of a base pulse, which creates a transmembrane pH gradient.…”

“…The fluorescence of these vesicles is stable prior to the injection of a base pulse, which creates a transmembrane pH gradient. 37 This assay was performed in the dark to assess vesicle stability and with UV irradiation to determine the effect of DTE isomerization on ion permeability. The emission maximum for HPTS is the same for both the acid and conjugate base forms; however, the excitation wavelengths differ.…”

“…37 Briefly, 2 mL of phosphate buffer and 100 μL of the lipid vesicle sample were added to a fluorescence cell and stirred. 37 Briefly, 2 mL of phosphate buffer and 100 μL of the lipid vesicle sample were added to a fluorescence cell and stirred.…”

Planar-bilayer activities of linear oligoester bolaamphiphiles

“…Structurally they similarly consist of a linear topology linked by internal esters (Es); the classes differ by the presence of multiple aromatic rings in the phthalates, and the lack of centrosymmetry in the alkyl compounds. These were expected to be active in voltage-clamp experiments, as close analogues to the phthalate compounds were found to be active in vesicles and planar bilayers [12], and the activities of the solid-phase compounds in vesicle experiments were previously established [13]. …”