Structure and medium effects on hydraphile synthetic ion channel toxicity to the bacterium E. coli

Synthetic hydraphile channels were systematically varied at the side arm position and tested under neutral and acidic conditions against the Gram-negative bacterium E. coli. Side arm structure is a critical determinant of channel activity within the bilayer and greatly influences toxicity. The biological activity data correlate remarkably well with the results of Na ⁺ transport studies conducted using synthetic liposome systems. Experiments to determine minimum inhibitory concentrations (MIC) were conducted under both neutral and acidic conditions. Hydraphile toxicity was diminished at pH = 5.5, compared to that at pH = ∼7, providing an example of a pH-dependent, synthetic, non-peptide ion channel.