Membrane activity of 3-hydroxyglutarate diesters

Abstract

The synthesis and characterisation of the transport activity and membrane localisation of three 3-hydroxyglutarate diesters containing saturated and diphenylacetylene-derived groups are described. In bilayer vesicles and planar bilayers, the two compounds bearing a terminal carboxylic acid form active ion channels; a related neutral compound is inactive. Nonlinear current–voltage behaviour is observed for the active diphenylacetylene-derived diester. The transport activity occurs at concentrations that are substantially below the level at which the compounds aggregate. Diphenylacetylene-derived fluorescence allows the partitioning and the aggregation states of the compounds to be probed. It is clear that the active compounds do not simply act as detergents, but form defined, if irregular, ion channels in the membrane.

Keywords:

• synthetic ion channel
• fluorescence
• vesicle
• bilayer membrane

Acknowledgements

The ongoing support of the Natural Sciences and Engineering Research Council of Canada and of The Nora and Mark DeGoutiere Memorial Scholarship (JMM) is gratefully acknowledged.

Notes

^1. ‘The trivial naming of the compounds follows from the linear structures with the carboxy and hydroxy termini explicity specified; named subunits are assumed to be linked as esters. The G(n) unit indicates a diester of 3-hydroxyglutaric acid with an n-carbon alkyl ester, the esters of α,ω-hydroxyalkanoic acids of 8, 10, and 12 carbons as Oct, Dec, and Dod, and the ester of 4-carboxymethyl-4’ hydroxymethyl-diphenylacetylene as Dip. In this paper only the final structures are named this way