Isolated from the venom sac of solitary spider wasp, Anoplius samariensis, anoplin is the smallest linear α-helical antimicrobial peptide found naturally with broad spectrum activity against both Gram-positive and Gram-negative bacteria, and little hemolytic activity toward human erythrocytes. Deamidation was found to decrease the peptide's antibacterial properties. In the present work, interactions of amidated (Ano-NH2) and deamidated (Ano-OH) forms of anoplin as well as Ano-NH2 composed of all D-amino acids (D-Ano-NH2) with model cell membranes were investigated by means of Langmuir Blodgett (LB) technique, atomic force microscopy (AFM), X-ray photoemission electron microscopy (X-PEEM) and carboxyfluorescein leakage assay in order to gain a better understanding of the effect of these peptide modifications on membrane binding and lytic properties. According to LB, all three peptides form stable monolayers at the air/water interface with Ano-NH2 occupying a slightly greater area per molecule than Ano-OH. All three forms of the peptide interact preferentially with anionic 1,2-dipalmitoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DPPG), rather than zwitterionic 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid monolayer. Peptides form nanoscale clusters in zwitterionic but not in anionic monolayers. Finally, membrane lytic activity of all derivatives was found to depend strongly on membrane composition and lipid/peptide ratio. The results suggest that amidated forms of peptides are likely to possess higher membrane binding affinity due to the increased charge.

High resolution 13C CPMAS spectra for three configurationally isomeric dicyclohexyl-18-crown-6 ethers and three complexes derived therefrom are presented. Spectra are consistent with conformationally locked crown ether structures at 298 K. Data are discussed in terms of the symmetry properties of the macrocycles and stereochemical effects on 13C chemical shifts in the solid phase. For the complex of 18-crown-6 with NaSCN and H2O, a single line is observed at 298 K. Temperature reduction removes the chemical shift averaging as the different torsional angles of the solid crown ether undergo distortions that become slow on the nuclear magnetic resonance timescale.

I3C NMR spectra of cis-cyclohexyl-15-crown-5 ether in the temperature range 298-173 K have been recorded. A single degenerate conformational process, attributed to cyclohexyl ring inversion, has been detected with a barrier of ca 10.3 kcal mol-'. Sodium ion complexation increases this barrier by ca 0.5 kcal mol-', whereas potassium ion complexation has no measurable effect. Spin-lattice relaxation time results also indicate more effective complexation of sodium ion than potassium ion by the macrocyclic crown ether system.

water-soluble polymer, PEG, to the lamellar phase of DMPC or of several surfactants, induces a topological transformation to a vesicular phase. Such transition can be understood in terms of a modification of the elastic properties of the membranes. In this work we perform a dynamic light scattering (DLS) study of the effect of PEG on phospholipid and surfactant bilayers. The experimental results show that the addition of the polymer slows down the dynamics of the membranes. From fits to an available theory for the scattering of dilute membrane systems, we have calculated the bending elastic modulus of the bilayers. This modulus increases with increasing polymer concentration, thus confirming that the macromolecule modifies the elastic properties of the membranes.