Jolanta Pajewska

Replacing proline at the apex of heptapeptide-based chloride ion transporters alters their properties and their ionophoretic efficacy

A membrane anchored heptapeptide, (C18H37)2NHCOCH2OCH2CO–NH–Gly–Gly–Gly–Pro–Gly–Gly–Gly–OCH2Ph, has proved to be a selective chloride anion transporter that functions in phospholipid bilayer membranes. When Pro was replaced by the natural amino acid Leu, the activity decreased dramatically. In the present study, Pro is replaced by pipecolic acid (homoproline, Pip); the resulting anchored heptapeptide is a membrane active, chloride selective transporter.

The effect of midpolar regime mimics on anion transport mediated by amphiphilic heptapeptides

Nine amphiphilic heptapeptides, synthetic anion transporters (SATs) of the form (C18H37)2N–Y–(Gly)3-Pro-(Gly)3–OCH2Ph were prepared. The unit (OH2)Y represents the diacids succinic, glutaric, diglycolic, 3-thiaglutaric, N-methyliminodiglycine, isophthalic, and terephthalic acids. Additionally, Y was absent or present as acetic acid affording the structure (C18H37)2N–(Gly)3-Pro-(Gly)3–OCH2Ph or (C18H37)2N–(Gly)4-Pro-(Gly)3–OCH2Ph. The diglycolic acid derivative was reported previously but the remaining compounds are new. These nine peptides mediated release of Cl– from DOPC/DOPA vesicles with varying efficacy. Chloride release diminished for the Y-containing amphiphilic heptapeptides in the order glutaric, succinic > 3-thiaglutaric > terephthalic > acetic, N-methyliminodiacetic, > no Y, isophthalic. The release of Cl– was generally exponential over time but the curve shapes were distinctly sigmoidal for the more flexible diacids. Computational studies were undertaken to assess differences in conformation. Overall, it appeared that Cl– release for those SATs that could adopt a linear conformation on the N-terminal side of proline correlated best with the polarity of the diacid.

Anchor chain length alters the apparent mechanism of chloride channel function in SCMTR derivatives.

Two membrane-anchored heptapeptides have been prepared and their pore-formation behavior in phospholipid bilayer membranes has been found to differ profoundly as a result only of alkyl chain length.

Glycine position permutations and peptide length alterations change the aggregation state and efficacy of ion-conducting, pore-forming amphiphiles

Changes in the peptide chain of amphiphilic heptapeptides known to form ion-conducting pores in bilayers dramatically alter transport efficacy and the aggregation number of pore formation.

The C-terminal ester of membrane anchored peptide ion channels affects anion transport.

Five heptapeptide derivatives, [CH3(CH2)17]2NCOCH2OCH2CO-Gly-Gly-Gly-Pro-Gly-Gly-Gly-OR, in which R = ethyl, 2-propyl, heptyl, benzyl, and cyclohexylmethyl, were found to transport chloride anion through a phospholipid bilayer to varying extents dependent on the identity of R. It was concluded that the R group is a membrane anchor for the synthetic chloride channels.

A hydrocarbon anchored peptide that forms a chloride-selective channel in liposomes

The heptapeptide sequence Gly-Gly-Gly-Pro-Gly-Gly-Gly, when anchored to diglycolic acid derived (C18H37)2NCOCH2OCH2COOH, forms chloride-selective ion channels in phospholipid liposomes but the related heptapeptide Gly-Gly-Gly-Leu-Gly-Gly-Gly, and tripeptide Gly-Gly-Gly do not.

Solid-State Evidence for Alkali Metal to Arene Pi-Complexation

We report a variety of alkali metal cation-π interactions, documented by X-ray crystallography. These include interactions with the neutral arenes benzene, phenol, and indole. We also include structural results for lithium, sodium, potassium, rubidium, and cesium cation-π complexes in which the arene has enhanced electron richness owing to an adjacent or integral charge.