Facilitated Chloride Transport Across Phosphatidylcholine Bilayers by an Acyclic Calixarene Derivative: Structure- Function Relationships

As the field of anion transport develops, it becomes increasingly important to understand mechanistic and structure-function relationships for those synthetic compounds that facilitate transmembrane anion transport. We define some key structural aspects that control the Cl anion transport function of an acyclic calixarene analog, triamide 2.We find that the secondary amide NH groups are necessary, but not sufficient, for activity in a standard base-pulse assay that measures the ability of compounds to dissipate pH via chloride transport. Evidence for self-association of 2 in the liposome is found in comparative studies of H/ Cl transport in EYPC and DPPC liposomes. Using an assay with a Cl sensitive dye, we also report direct evidence for Cl transmembrane transport by the acyclic triamide 2 and the 1,3 alternate calix[4]arene 1.Consistent with the base-pulse assay, the acyclic triamide 2 is more active than calixarene 1 in the lucigenin Cl transport assay.