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Solid state (19)F NMR revealed the conformation and alignment of the fusogenic peptide sequence B18 from the sea urchin fertilization protein bindin embedded in flat phospholipid bilayers. Single (19)F labels were introduced into nine distinct positions along the wild-type sequence by substituting each hydrophobic amino acid, one by one, with L-4-fluorophenylglycine. Their anisotropic chemical shifts were measured in uniaxially oriented membrane samples and used as orientational constraints to model the peptide structure in the membrane-bound state. Previous (1)H NMR studies of B18 in 30% TFE and in detergent micelles had shown that the peptide structure consists of two alpha-helical segments that are connected by a flexible hinge. This helix-break-helix motif was confirmed here by the solid-state (19)F NMR data, while no other secondary structure (beta-sheet, 3(10)-helix) was compatible with the set of orientational constraints. For both alpha-helical segments we found that the helical conformation extends all the way to the respective N- and C-termini of the peptide. Analysis of the corresponding tilt and azimuthal rotation angles showed that the N-terminal helix of B18 is immersed obliquely into the bilayer (at a tilt angle tau approximately 54 degrees), whereas the C-terminus is peripherally aligned (tau approximately 91 degrees). The azimuthal orientation of the two segments is consistent with the amphiphilic distribution of side-chains. The observed 'boomerang'-like mode of insertion into the membrane may thus explain how peptide binding leads to lipid dehydration and acyl chain perturbation as a prerequisite for bilayer fusion to occur.  相似文献   
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New lanthanide dimethyl-N-benzoylamidophosphate (HL) based tetrakis-complexes NEt4[LnL4] (Ln3+=La, Nd, Sm, Eu, Gd, Tb, Dy) are reported. The complexes are characterized by means of NMR, IR, absorption, and luminescent spectroscopy as well as by elemental, X-Ray, and thermal gravimetric analyses. The phenyl groups of the four ligands of the complex anion are directed towards one side, while the methoxy groups are directed in the opposite side, which makes the complexes under consideration structurally similar to calixarenes. The effect of changing the alkali metal counterion to the organic cation NEt4+ on the structure and properties of the tetrakis-complex [LnL4]- is analyzed. The complexes exhibit bright characteristic for respective lanthanides luminescence. Rather high intensity of the band of 5D07F4 transition, observed in the luminescence spectrum of NEt4[EuL4], is discussed based on theoretical calculations.  相似文献   
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Cell-penetrating peptides (CPPs) are short polycationic sequences that can translocate into cells without disintegrating the plasma membrane. CPPs are useful tools for delivering cargo, but their molecular mechanism of crossing the lipid bilayer remains unclear. Here we study the interaction of the HIV-derived CPP TAT (48-60) with model membranes by solid-state NMR spectroscopy and electron microscopy. The peptide induces a pronounced isotropic (31)P NMR signal in zwitterionic DMPC, but not in anionic DMPG bilayers. Octaarginine and to a lesser extent octalysine have the same effect, in contrast to other cationic amphiphilic membrane-active peptides. The observed non-lamellar lipid morphology is attributed to specific interactions of polycationic peptides with phosphocholine head groups, rather than to electrostatic interactions. Freeze-fracture electron microscopy indicates that TAT(48-60) induces the formation of rodlike, presumably inverted micelles in DMPC, which may represent intermediates during the translocation across eukaryotic membranes.  相似文献   
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Conformationally constrained non‐racemizing trifluoromethyl‐substituted lysine isosteres [(E)‐ and (Z)‐TCBLys] with charged side chains are presented as a new type of 19F‐NMR labels for peptide studies. Design of the labels, their synthesis, incorporation into peptides and experimental demonstration of their application for solid state NMR studies of membrane‐active peptides are described. A series of fluorine‐labeled analogues of the helical amphipathic antimicrobial peptide PGLa(Nle) was obtained, in which different lysine residues in the original peptide sequence were replaced, one at a time, by either (E)‐ or (Z)‐TCBLys. Antimicrobial activities of the synthesized analogues were practically the same as those of the parent peptide. The structural and orientational parameters of the helical PGLa(Nle) peptide in model bilayers, as determined using the novel labels confirmed and refined the previously known structure. (E)‐ and (Z)‐TCBLys, as a set of cationic 19F‐NMR labels, were shown to deliver structural information about the charged face of amphipathic peptides by solid state 19F‐NMR, previously inaccessible by this method.  相似文献   
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A multicomponent synthetic approach for 5-aryl/heterylidene-2-(2-hydroxyethylamino)- and 2-(3-hydroxypropylamino)-thiazol-4-ones starting from 2-thioxothiazolidin-4-one or 2-methylsulfanylthiazol-4-one was developed. The proposed method involves simultaneous aminolysis of 2-thioxo- or 2-methylsulfanyl groups and Knoevenagel condensation with (hetero)aromatic aldehydes using 2-aminoethanol or 3-aminopropan-1-ol as catalysts. Side-chain prototropic amino–imino tautomerism was observed for target 5-ylidene-2-alkylaminothiazol-4-ones.  相似文献   
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The base-mediated cyclocondensation of 1,3-dicarbonyl compounds with 4-chloro-3-nitrocoumarin provides a convenient approach to various chromeno[3,4-b]pyrrol-4(3H)-ones.  相似文献   
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