269 research outputs found
Pseudopeptides designed to form supramolecular helixes: The role of the stereogenic centers
No full textThe two epimers Boc-L-Phe-D-Oxd-(S)-Î23-hPhg-OBn (1) and Boc-L-Phe-D-Oxd-(R)-Î23-hPhg-OBn (2) have been prepared by standard methods in solution, and their conformation was analyzed both in solution and in the solid state. While in solution 1 shows a random coil structure, 2 tends to assume a Î3-turn conformation that is nearly retained in the solid state. On the other hand, in the solid state molecules of 1 associate generating a helix that involves the formation of elongated crystals with hexagonal cross-section. This effect is not observed in the crystals formed by Boc-L-Phe-D-Oxd-(R)-Î23-hPhg-OBn 2. © 2009 American Chemical Society
Nanofibers from oxazolidi-2-one containing hybrid foldamers: what is the right molecular size?
No full textA series of oligomers of the type Boc-(L-Phe-D-Oxd)n-OBn (Boc = tert-butoxycarbonyl; Oxd = 4-methyl-5carboxy oxazolidin-2-one; Bn = benzyl) were prepared for n = 2-5. The shortest oligomer, Boc-(L-Phe-D-Oxd)2-OBn, aggregates and forms a fiber-like material with an anti-parallel β-sheet struc- ture in which the oligopeptide units are connected to each other by only one intermolecular hydrogen bond. The longer oligomers exhibit structural heterogeneity. They start to organize into secondary structures by the formation of intramolecular hydrogen bonds at the pentamer level. Microscopy and diffraction of the oligomers indicated a crystalline character for only the shorter ones. © 2009 Wiley-VCH Verlag GmbH & Co
The Interaction of Lipid Modified Pseudopeptides with Lipid Membranes
No full textWe have studied the structure of two lipopeptides based on the simple dipeptide building block L-Phe-D-Oxd. These peptides have been reported previously to form fiber-like materials. The lipopeptides synthesized here had the structures Cn2H(2n+1)CO-L-Phe-D-Oxd-OBn or Cn2H(2n+1)CO-D-Phe-L-Oxd-OBn with n = 5 or 11. Addition of the N-terminal lipid modification did not cause a major disturbance of the structures these molecules form. The lipid modifications themselves showed highly rigid structures as inferred from solid-state 2H NMR. The peptide backbone showed 13C NMR chemical shifts in agreement with -sheet secondary structure. Addition of a lipid modification to the N-terminus is a common motif in biology to attach proteins to the membrane. Therefore, we also investigated the lipopeptides in the pre¬sence of synthetic POPC bilayers. Two different molecular species were detected under these circumstan¬ces: (i) lipopeptide monomers that showed chain order parameters similar to those of the host membrane, (ii) lipopeptide aggregates that exhibited very similar structures and dynamics as the crystalline aggre¬gates. Overall, the lipopeptides showed a well defined and rigid secondary structure that is in agreement with fibrillar aggregates previously detected for those peptides without the lipid modification
AMYLOIDS: SELF-ASSEMBLY OF OXAZOLIDIN-2-ONES CONTAINING HYBRID PSEUDOPEPTIDES
No full textWith the aim of obtaining new molecules that could form nanomaterials through intermolecular aggregations in the solid state, we prepared some oligomers of the Boc-(L-Phe-D-Oxd)n-OR series with the expectation that the presence of phenyl groups could favour aggregation by means of NH hydrogen bonds and/or pi-stacking interactions. We can show that fibers or fibrils are formed dependent on the length of the foldamer chain. The chemical properties of these compounds have been examined in the solid phase utilizing X-ray diffraction, solid state NMR, SEM, and TEM microscopy. Theoretical calculations have been performed to explain the results
Defective cellular localization of mutant ATP7B in Wilson's disease patients and hepatoma cell lines
No full textBackground & Aims: Wilson's disease, a hereditary disorder caused by mutations in the Wilson's disease gene (ATP7B), leads to hepatic and/or neurological pathology resulting from cellular copper overload. In vitro studies showed that ATP7B, located in the trans-Golgi network, traffics to a cytoplasmic vesicular compartment in response to increased copper concentration. Mislocalization and failed intracellular trafficking of ATP7B mutants are suggested to be among disease-causing mechanisms; however, the effect of mutations on ATP7B localization in human tissues has not been directly shown. Therefore, we characterized the subcellular localization of normal and mutant ATP7B in human livers and in hepatoma cell lines. Methods: Subcellular distribution of ATP7B in liver tissue from 3 control individuals and 3 Wilson's disease patients harboring a homozygous H1069Q-ATP7B mutation was analyzed by using immunogold electron microscopy. In addition, 14 ATP7B mutants tagged to green fluorescent protein were generated and expressed in HuH-7 and HepG2 cells; intracellular localization of these mutants was characterized by confocal microscopy. Results : In hepatocytes, ATP7B was localized in trans-Golgi vesicles, whereas H1069Q-ATP7B was trapped in the endoplasmic reticulum. Similar results were observed for wild-type ATP7B and H1069Q-ATP7B expressed in hepatoma cells. Most ATP7B proteins harboring missense mutations were distributed similarly to wild-type ATP7B. In contrast, truncated ATP7B mutants showed a diffuse, clustered, cytoplasmic pattern, distinct from the trans-Golgi network or endoplasmic reticulum. Conclusions: These results provide a detailed demonstration of the ATP7B distribution in control and diseased human livers and indicate that several Wilson's disease mutations lead to incorrect localization of ATP7B to distinct cell compartments
A fiberlike peptide material stabilized by single intermolecular hydrogen bonds
No full textOne is enough: The dipeptide Boc-L-Phe-D-Oxd-OBn (Boc = tert-butoxycarbonyl, Phe = phenylalanine, Oxd = 4-methyl-5-carboxy oxazolidin-2-one, Bn = benzyl; see picture; gray C, white H, red O, blue N) spontaneously forms uniform fibers consisting of parallel infinite linear chains arising from single intermolecular N-H···O=C hydrogen bonds. This is the absolute borderline case of a parallel β-sheet structure. (Figure Presented). © 2008 Wiley-VCH Verlag GmbH & Co. KGaA
A complex of Ca 1.2/PKC is involved in muscarinic signaling in smooth muscle
No full textHuster M, Frei E, Hofmann F, Wegener J. A complex of Ca 1.2/PKC is involved in muscarinic signaling in smooth muscle. The FASEB Journal. 2010;24(8):2651-2659.Here we present functional and biochemical evidence for a Ca2+ channel (CaV1.2) /protein kinase C (PKC) signaling complex being a key player in muscarinic regulation of urinary bladder smooth muscle. Muscarinic stimulation induced Ca2+ signals and concomitant contractions in detrusor muscle from mice that were dependent on functional Ca2+ channels. These signals were still present in muscles being depolarized by 85 mM extracellular K+. Muscarinic-induced contractions were reduced by a PKC inhibitor [bisindolylmaleimide I (BIM-I)] and a phospholipase D (PLD) inhibitor (1-butanol). A phorbol ester (PDBu) enlarged muscarinic-induced Ca2+ signals and contractions. The effects of BIM-I and PDBu were inhibited by isradipine and/or absent in muscles from CaV1.2-deficient mice. Both carbachol and PDBu increased CaV1.2 channel currents in isolated bladder myocytes. Blue native-PAGE electrophoresis revealed that CaV1.2, PKC, and PLD are closely associated in muscles being previously stimulated by carbachol. Immunoprecipitation using anti-CaV1.2 followed by Western blotting demonstrated that CaV1.2 and PKC are coupled in stimulated muscles from wild-type mice. Autoradiography on immunoprecipitates showed that CaV1.2 is a substrate for PKC-mediated phosphorylation. These findings suggest that a signaling complex consisting of CaV1.2, PKC, and, probably, PLD controls muscarinic-mediated phasic contraction of urinary bladder smooth muscle.—Huster, M., Frei, E., Hofmann, F., Wegener, J. W. A complex of CaV1.2/PKC is involved in muscarinic signaling in smooth muscle. FASEB J. 24, 2651–2659 (2010)
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