@article {2390, title = {Effect of Membrane Composition on Antimicrobial Peptides Aurein 2.2 and 2.3 From Australian Southern Bell Frogs}, journal = {Biophysical Journal}, volume = {96}, number = {2}, year = {2009}, note = {ISI Document Delivery No.: 450BYTimes Cited: 8Cited Reference Count: 96Cheng, John T. J. Hale, John D. Elliot, Melissa Hancock, Robert E. W. Straus, Suzana K.}, month = {Jan}, pages = {552-565}, type = {Article}, abstract = {The effects of hydrophobic thickness and the molar phosphatidylglycerol (PG) content of lipid bilayers on the structure and membrane interaction of three cationic antimicrobial peptides were examined: aurein 2.2, aurein 2.3 (almost identical to aurein 2.2, except for a point mutation at residue 13), and a carboxy C-terminal analog of aurein 2.3. Circular dichroism results indicated that all three peptides adopt an a-helical structure in the presence of a 3:1 molar mixture of 1,2-dimyristoyi-sn-glycero3-phosphocholine/1,2-dimyristoyi-sn-glycero-3- [phospho-rac-(1-glycerol)] (DMPC/DMPG), and 1:1 and 3:1 molar mixtures of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine/1-paimitoyl-2-oleoyl-sn -glycero-3-[phospho-rac-(1-glycerol)] (POPC/POPG). Oriented circular dichroism data for three different lipid compositions showed that all three peptides were surface-adsorbed at low peptide concentrations, but were inserted into the membrane at higher peptide concentrations. The (31)p solid-state NMR data of the three peptides in the DMPC/DMPG and POPC/POPG bilayers showed that all three peptides significantly perturbed lipid headgroups, in a peptide or lipid composition-dependent manner. Differential scanning calorimetry results demonstrated that both amidated aurein peptides perturbed the overall phase structure of DMPC/DMPG bilayers, but perturbed the POPC/POPG chains less. The nature of the perturbation of DMPC/DMPG bilayers was most likely micellization, and for the POPC/POPG bilayers, distorted toroidal pores or localized membrane aggregate formation. Calcein release assay results showed that aurein peptide-induced membrane leakage was more severe in DMPC/DMPG liposomes than in POPC/POPG liposomes, and that aurein 2.2 induced higher calcein release than aurein 2.3 and aurein 2.3-COOH from 1:1 and 3:1 POPC/POPG liposomes. Finally, DiSC(3)5 assay data further delineated aurein 2.2 from the others by showing that it perturbed the lipid membranes of intact S. aureus C622 most efficiently, whereas aurein 2.3 had the same efficiency as gramicidin S, and aurein 2.3-COOH was the least efficient. Taken together, these data show that the membrane interactions of aurein peptides are affected by the hydrophobic thickness of the lipid bilayers and the PG content.}, keywords = {ANTIBIOTIC PEPTIDES, CIRCULAR-DICHROISM SPECTROSCOPY, HOST-DEFENSE PEPTIDES, LIPID-COMPOSITION, MEMBRANES, MODEL, PHOSPHOLIPID-BILAYER MEMBRANES, PROTEIN SECONDARY STRUCTURE, SOLID-STATE NMR, STAPHYLOCOCCUS-AUREUS, TREE-FROG}, isbn = {0006-3495}, url = {://000266377200025}, author = {Cheng, J. T. J. and Hale, J. D. and Elliot, M. and Hancock, R. E. W. and Straus, S. K.} } @article {5206, title = {XPS study of interfaces in a two-layer light-emitting diode made from PPV and Nafion with ionically exchanged Ru(bpy)(3)(2+)}, journal = {Applied Surface Science}, volume = {174}, number = {1}, year = {2001}, note = {ISI Document Delivery No.: 416RQTimes Cited: 13Cited Reference Count: 39}, month = {Apr}, pages = {43-50}, type = {Article}, abstract = {X-ray photoelectron spectroscopy (XPS) was used to investigate the interfacial chemistries occurring in a prototype two-layer polymer light-emitting diode that had been fabricated from PPV and Nafion with ion-exchanged Ru(bpy)(3)(2 +) Magnesium and indium tin oxide (ITO) were used as electrodes, and XPS observations were made as the different layers were added sequentially. Specifically, Mg was deposited on a layer of Nafion with incorporated Ru(bpy)(3)(2 +), and this was itself deposited on PPV-coated ITO. The morphology of Nafion, which is dictated by the strongly hydrophilic and hydrophobic groups that compose it, is indicated to rearrange with the incorporation of Ru(bpy)(3)(2 +) this rearrangement appears reinforced when a thin film is deposited on PPV. The Mg deposition results in substantial changes in XPS spectra, in part due to a direct interaction with the fluorocarbon backbone of Nation. (C) 2001 Elsevier Science B.V. All rights reserved.}, keywords = {CHEMISTRY, conjugated polymers, COPOLYMERS, ELECTROLUMINESCENCE, FILMS, luminescence, MEMBRANES, NAFION, POLYETHYLENETEREPHTHALATE, polymer light-emitting diodes, RAY PHOTOELECTRON-SPECTROSCOPY, ruthenium polypyridyl complex, SYSTEMS, X-ray photoelectron spectroscopy}, isbn = {0169-4332}, url = {://000167794300006}, author = {Susac, D. and Kono, M. and Wong, K. C. and Mitchell, K. A. R.} }