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Notes on Rock-forming Minerals(29) A pyralspite garnet from a schistose garnetbearing siliceous rock included within a serpentinite mass of Sekizen Mine, Ehime Prefecture, Japan.,

rights: 日本地質学会 rights: 本文データは学協会の許諾に基づきCiNiiから複製したものである relation: IsVersionOf: http://ci.nii.ac.jp/naid/110003020140/textapplication/pdfjournal articl

Helical Structure of Dermaseptin B2 in a Membrane-Mimetic Environment

Dermaseptins are antimicrobial peptides from frog skin that have high membrane-lytic activity against a broad spectrum of microorganisms. The structure of dermaseptin B2 in aqueous solution, in TFE/water mixtures, and in micellar and nonmicellar SDS was analyzed by CD, FTIR, fluorescence, and NMR spectroscopy combined with molecular dynamics calculations. Dermaseptin B2 is unstructured in water, but helical conformations, mostly in segment 3−18, are stabilized by addition of TFE. SDS titration showed that dermaseptin B2 assumes nonhelical structures at SDS concentrations far below the critical micellar concentration and helical structures at micellar concentrations. Dermaseptin B2 bound to SDS micelles (0.4 mM peptide, 80 mM SDS) adopts a well-defined amphipathic helix between residues 11−31 connected to a more flexible helical segment spanning residues 1−8 by a flexible hinge region around Val9 and Gly10. Experiments using paramagnetic probes showed that dermaseptin B2 lies near the surface of SDS micelles and that residue Trp3 is buried in the SDS micelle, but close to the surface. A slow exchange equilibrium occurs at higher peptide/SDS ratios (2 mM peptide, 80 mM SDS) between forms having distinct sets of resonances in the N-terminal 1−11 segment. This equilibrium could reflect different oligomeric states of dermaseptin B2 interacting with SDS micelles. Structure−activity studies on dermaseptin B2 analogues showed that the N-terminal 1−11 segment is an absolute requirement for antibacterial activity, while the C-terminal 10−33 region is also important for full antibiotic activity

Comparison of Penetratin and Other Homeodomain-Derived Cell-Penetrating Peptides: Interaction in a Membrane-Mimicking Environment and Cellular Uptake Efficiency^†

Antennapedia and other homeoproteins have the unique ability to efficiently translocate across biological membranes, a property that is mediated by the third helix of the homeodomain. To analyze the effects of sequence divergence in the homeodomain, we have compared the cellular uptake efficiencies and interaction properties in a membrane-mimicking environment of four peptides corresponding to the third helix sequence of Antennapedia, Engrailed-2, HoxA-13, and Knotted-1. NMR studies revealed that these peptides adopt helical conformations in SDS micelles. Their localization with respect to the micelle was investigated using Mn2+ as a paramagnetic probe. Peptides are positioned parallel to the micelle surface, but subtle differences in the depth of immersion were observed. Using a recently developed method for quantification of CPP cellular uptake based on MALDI−TOF mass spectrometry, all of these peptides were found to translocate into cells but with large differences in their uptake efficiencies. The peptide with the highest uptake efficiency was found to be the least deeply inserted within the micelle, indicating that electrostatic surface interactions may be a major determinant for membrane translocation. A new cell-penetrating peptide derived from Knotted-1 homeodomain with improved uptake properties compared to penetratin is introduced here

Figure 1

<p>Projections of α–helices of the six basic studied peptides. Basic residues in black, hydrophobic residues in red, other residues in blue. The structure of SP associated to membranes is not known. pAntp is only ∼70% helical when interacting with membranes. The basic/hydrophobic surfaces ratio of RL16 is higher than that of RW16. Helices were generated with the Swiss-PdbViewer programme.</p

Sequences and physicochemical features of peptides.

a)<p>Net theoretical positive charge at pH 7. (R9, RW9 and SP contained a free N-terminal amino group. RW16 and RL16 contained a biotin (Bi) on N-terminus. Both biotinylated and acetylated penetratin derivatives were also tested in experiments and gave the same results than the non-modified peptide).</p>b)<p>Amphipathic α-helix when bound to membranes</p

Effect of the peptides on the thickness of the membrane bilayer (d_bilayer) and hydration layer (d_water) of the two distinct lamellar phases (Ld1 and Ld2) comprised in the PC/PG (9/1) multilamellar vesicles at 20°C.

<p>Effect of the peptides on the thickness of the membrane bilayer (d_bilayer) and hydration layer (d_water) of the two distinct lamellar phases (Ld1 and Ld2) comprised in the PC/PG (9/1) multilamellar vesicles at 20°C.</p

Morphological effects of peptides on giant unilamellar vesicles (GUVs)^a

a)<p>The quantification of effects was obtained by observation of 153 recorded GUVs. The number of GUVs containing the different structures and adhering to other GUVs was counted, however the number of tubes or vesicles induced by the peptides was not measured due to the frequent high density of structures inside the vesicles. The evolution of fines tubes to large tubes and vesicles increases the difficulty to quantify precisely the proportion of structures.</p

Figure 6

<p>Peptide-induced LUVs permeability at different Peptide/Lipid weight ratio. Percent of calcein release from LUVs 5 min after peptide addition: R9 (○), pAntp (□), RW9 (•), RW16 (▪), RL16 (▴) and SP (X). Experiments were achieved at 25°C.</p