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The usefulness of pyrene-1,3,6-trisulfonates as cofactors for p-octiphenyl ?-barrel ion channels to mediate recognition and conversion of otherwise inaccessible benzaldehyde substrates is described.

Studies on the usefulness of rigid-rod molecules to address pertinent questions of biological relevance are summarized. Emphasis is placed on (a) the supramolecular functional plasticity of p-octiphenyl ?-barrels expressed in molecular recognition (adaptable synthetic hosts), molecular translocation (adaptable synthetic ion channels) and molecular transformation (esterases, RNases), (b) molecular recognition of polarized membranes by rigid push-pull rods, as well as (c) the synthetic organic chemistry of rigid-rod molecules.

The current study is aimed at investigating the effect of fine-tuning the cationic character of synthetic mimics of antimicrobial peptides (SMAMPs) on the hemolytic and antibacterial activities. A series of novel norbornene monomers that carry one, two, or three Boc-protected amine functionalities was prepared. Ring-opening metathesis polymerization (ROMP) of the monomers, followed by deprotection of the amine groups resulted in cationic antimicrobial polynorbornenes that carry one, two, and three charges per monomer repeat unit. Increasing the number of amine groups on the most hydrophobic polymer reduced its hemolytic activity significantly. To understand the membrane activity of these polymers, we conducted dye leakage experiments on lipid vesicles that mimic bacteria and red blood cell membranes, and these results showed a strong correlation with the hemolysis data. [ABSTRACT FROM AUTHOR]

Host defense peptides (HDPs), part of the innate immune system, selectively target the membranes of bacterial cells over that of host cells. As a result, their antimicrobial properties have been under intense study. Their selectivity strongly depends on the chemical and mostly structural properties of the lipids that make up different cell membranes. The ability to synthesize HDP mimics has recently been demonstrated. To better understand how these HDP mimics interact with bilayer membranes, three homologous antimicrobial oligomers (AMOs) 1−3with an m-phenylene ethynylene backbone and alkyl amine side chains were studied. Among them, AMO 1is nonactive, AMO 2is specifically active, and AMO 3is nonspecifically active against bacteria over human red blood cells, a standard model for mammalian cells. The interactions of these three AMOs with liposomes having different lipid compositions are characterized in detail using a fluorescent dye leakage assay. AMO 2and AMO 3caused more leakage than AMO 1from bacteria membrane mimic liposomes composed of PE/PG lipids. The use of E. colilipid vesicles gave the same results. Further changes of the lipid compositions revealed that AMO 2has selectively higher affinity toward PE/PG and E. colilipids than PC, PC/PG or PC/PS lipids, the major components of mammalian cell membranes. In contrast, AMO 3is devoid of this lipid selectivity and interacts with all liposomes with equal ease; AMO 1remains inactive. These observations suggest that lipid type and structure are more important in determining membrane selectivity than lipid headgroup charges for this series of HDP mimics. [ABSTRACT FROM AUTHOR]