Spacer chain length dependence in hydraphile channels

Enhancement of antimicrobial activity by synthetic ion channel synergy

Hydraphile synthetic ion channels were found to enhance the cytotoxicity to E. coli and B. subtilis of erythromycin, kanamycin, rifampicin, and tetracycline when co-administered with the antibiotic at sublethal concentrations of channel.

Dynamic assessment of bilayer thickness by varying phospholipid and hydraphile synthetic channel chain lengths

A library of "hydraphile" synthetic ion channel analogues that differ in overall length from approximately 28-58 A has been prepared. A new and convenient ion-selective electrode (ISE) method was used to assay Na(+) release. Liposomes were formed from three different phospholipids: 1,2-dimyristoleoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), and 1,2-dierucoyl-sn-glycero-3-phosphocholine (DEPC). The acyl chains of the lipids comprise cis-unsaturated 14:1, 18:1, or 22:1 residues, respectively. Sodium release was measured for each liposome system with each of the synthetic channels. Peak activity was observed for shorter channels in liposomes formed from DMPC and for longer channels in DEPC. A separate study was then conducted in DMPC liposomes in the presence of the putative membrane-thickening agents cholesterol and decane. Peak activity was clearly shifted to longer channel lengths upon addition of 20 or 40 mol % cholesterol or n-decane to the liposome preparation.

Synthetic Ion Channel Activity Documented by Electrophysiological Methods in Living Cells

Hydraphiles are synthetic ion channels that use crown ethers as entry portals and that span phospholipid bilayer membranes. Proton and sodium cation transport by these compounds has been demonstrated in liposomes and planar bilayers. In the present work, whole cell patch clamp experiments show that hydraphiles integrate into the membranes of human embryonic kidney (HEK 293) cells and significantly increase membrane conductance. The altered membrane permeability is reversible, and the cells under study remain vital during the experiment. Control compounds that are too short (C(8)-benzyl channel) to span the bilayer or are inactive owing to a deficiency in the central relay do not induce similar conductance increases. Control experiments confirm that the inactive channel analogues do not show nonspecific effects such as activation of native channels. These studies show that the combination of structural features that have been designed into the hydraphiles afford true, albeit simple, channel function in live cells.

Synthetic hydraphile channels of appropriate length kill Escherichia coli

Crown ether-based synthetic cation conducting channels called hydraphiles show clear ionophoretic activity in phospholipid vesicles. These compounds are shown to be active against the bacterium E. coli. Disk diffusion assays were performed to assess the toxicity of different hydraphile derivatives. Liquid culture tests were conducted to quantitate the dependence of bacterical activity on channel length. It is proposed that hydraphiles are toxic to bacteria as a result of channel formation in the membrane. The bactericidal activity is found to depend at least on the presence of a functional central relay and proper channel length. It is speculated that hydraphiles insert into the bilayer and disrupt the cell's osmotic balance, leading to cell death.