The complexity of the BU anionophores is further highlighted by their strongly varied response to the addition of cholesterol to the membrane compositions, where compounds with hydrogen bond accepting oxygen atoms seem to be most impacted. Further investigations are therefore required in the context of biological applications, as cell membranes are much more complex than the model LUVs used here. Despite several variations in the BU substituents, 1 remains the most active BU macrocycle-based transporter to date and the most active Cl -/HCO3 -antiporter known. The study of different antiport processes between halides and oxoanions by 1 has shown that a balanced binding selectivity for the transported anions is preferred for an effective antiport process by these BUs with very high anion affinities.