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Membrane Interaction (membrane + interaction)

Distribution by Scientific Domains

Chemistry	53%
Life Sciences	26%
Medical Sciences	19%

Selected Abstracts

Drug,Membrane Interaction on Immobilized Liposome Chromatography Compared to Immobilized Artificial Membrane (IAM), Liposome/Water, and Octan-1-ol/Water Systems

HELVETICA CHIMICA ACTA, Issue 2 2010
Xiangli Liu
Abstract The objective of this study was to investigate drug,membrane interaction by immobilized liposome chromatography (ILC; expressed as lipophilicity index log,Ks) and the comparison with lipophilicity indices obtained by liposome/H2O, octan-1-ol/H2O, and immobilized artificial membrane (IAM) systems. A set of structurally diverse monofunctional compounds and drugs (nonsteroidal anti-inflammatory drugs and , -blockers) were selected in this study. This set of solutes consists of basic or acidic functionalities which are positively or negatively charged at physiological pH,7.4. No correlation was found between log,Ks from ILC and lipophilicity indices from any of the other membrane model systems for the whole set of compounds. For structurally related compounds, significant correlations could be established between log,Ks from ILC and lipophilicity indices from IAM chromatography and octan-1-ol/H2O. However, ILC and liposome/H2O systems only yield parallel partitioning information for structurally related large molecules. For hydrophilic compounds, the balance between electrostatic and hydrophobic interactions dominating drug partitioning is different in these two systems. [source]

Book Review: Drug,Membrane Interactions.

CHEMBIOCHEM, Issue 3 2004
Analysis, Drug Distribution, Modelling.
No abstract is available for this article. [source]

The influence of cholesterol on the interaction of HIV gp41 membrane proximal region-derived peptides with lipid bilayers

FEBS JOURNAL, Issue 19 2007
Ana S. Veiga
A small amino acid sequence (LWYIK) inside the HIV-1 gp41 ectodomain membrane proximal region (MPR) is commonly referred to as a cholesterol-binding domain. To further study this unique and peculiar property we have used fluorescence spectroscopy techniques to unravel the membrane interaction properties of three MPR-derived synthetic peptides: the membrane proximal region peptide-complete (MPRP-C) which corresponds to the complete MPR; the membrane proximal region peptide-short (MPRP-S), which corresponds to the last five MPR amino acid residues (the putative cholesterol-binding domain) and the membrane proximal region peptide-intermediate (MPRP-I), which corresponds to the MPRP-C peptide without the MPRP-S sequence. MPRP-C and MPRP-I membrane interaction is largely independent of the membrane phase. Membrane interaction of MPRP-S occurs for fluid phase membranes but not in gel phase membranes or cholesterol-containing bilayers. The gp41 ectodomain MPR may have a very specific function in viral fusion through the concerted and combined action of cholesterol-binding and non-cholesterol-binding domains (i.e. domains corresponding to MPRP-S and MPRP-I, respectively). [source]

Characterization of Xenopus egg membrane microdomains containing uroplakin Ib/III complex: roles of their molecular interactions for subcellular localization and signal transduction

GENES TO CELLS, Issue 2 2007
A.K.M. Mahbub Hasan
A single-transmembrane protein uroplakin III (UPIII) and its tetraspanin binding-partner uroplakin Ib (UPIb) are members of the UP proteins that were originally identified in mammalian urothelium. In Xenopus laevis eggs, these proteins: xUPIII and xUPIb, are components of the cholesterol-enriched membrane microdomains or "rafts" and involved in the sperm,egg membrane interaction and subsequent egg activation signaling via Src tyrosine kinase at fertilization. Here, we investigate whether the xUPIII-xUPIb complex is in close proximity to CD9, a tetraspanin that has been implicated in the sperm,egg fusion in the mouse and GM1, a ganglioside typically enriched in egg rafts. Preparation of the egg membrane microdomains using different non-ionic detergents (Brij 98 and Triton X-100), chemical cross-linking, co-immunoprecipitation, in vitro kinase assay and in vitro fertilization experiments demonstrated that GM1, but not CD9, is in association with the xUPIII-xUPIb complex and contributes to the sperm-dependent egg activation. Transfection experiments using HEK293 cells demonstrated that xUPIII and xUPIb localized efficiently to the cholesterol-dependent membrane microdomains when they were co-expressed, whereas co-expression of xUPIII and CD9, instead of xUPIb, did not show this effect. Furthermore, xUPIII and xUPIb were shown to suppress kinase activity of the wild type, but not a constitutively active form of, Xenopus Src protein co-expressed in HEK293 cells. These results provide novel insight into the molecular architecture of the egg membrane microdomains containing xUPIII, xUPIb and Src, which may contribute to the understanding of sperm,egg interaction and signaling during Xenopus fertilization. [source]

Drug,Membrane Interaction on Immobilized Liposome Chromatography Compared to Immobilized Artificial Membrane (IAM), Liposome/Water, and Octan-1-ol/Water Systems

Ab initio computational study of positron emission tomography ligands interacting with lipid molecule for the prediction of nonspecific binding

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 14 2008
Lula Rosso
Abstract Nonspecific binding is a poorly understood biological phenomenon of relevance in the study of small molecules interactions in vivo and in drug development. Nonspecific binding is thought to be correlated in part to a molecule's lipophilicity, typically estimated by measuring (or calculating) octanol,water partition coefficient. This is, however, a gross simplification of a complex phenomenon. In this article, we present a computational method whose aim is to help identify positron emission tomography (PET) ligands with low nonspecific binding characteristics by investigating the molecular basis of ligand,membrane interaction. We considered a set consisting of 10 well-studied central nervous system PET radiotracers acting on a variety of molecular targets. Quantum mechanical calculations were used to estimate the strength of the interaction between each drug molecule and one phospholipid molecule commonly present in mammalian membranes. The results indicate a correlation between the computed drug,lipid interaction energy and the in vivo nonspecific distribution volume relative to the free tracer plasma concentration, calculated using standard compartmental modeling for the analysis of PET data. Significantly, the drugs whose interaction with the lipid molecule more favorably possessed, in general, a higher nonspecific binding value, whereas for the drugs taken in consideration in this study, the water-octanol partition coefficient, log P, did not show good predictive power of the nonspecific binding. This study also illustrates how ab initio chemical methods may offer meaningful and unbiased insights for the understanding of the underlying chemical mechanisms in biological systems. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008 [source]

Real-time monitoring of the membrane-binding and insertion properties of the cholesterol-dependent cytolysin anthrolysin O from Bacillus anthracis,

JOURNAL OF MOLECULAR RECOGNITION, Issue 4 2006
Simon Cocklin
Abstract Bacillus anthracis has recently been shown to secrete a potently hemolytic/cytolytic protein that has been designated anthrolysin O (ALO). In this work, we initiated a study of this potential anthrax virulence factor in an effort to understand the membrane,binding properties of this protein. Recombinant anthrolysin O (rALO35,512) and two N-terminally truncated versions of ALO (rALO390,512 and rALO403,512) from B. anthracis were overproduced in Escherichia coli and purified to homogeneity. The role of cholesterol in the cytolytic activity of ALO was probed in cellular cholesterol depletion assays using mouse and human macrophage-like lines, and also Drosophila Schneider 2 cells. Challenging the macrophage cells with rALO35,512, but not rALO390,512 or rALO403,512, resulted in cell death by lysis, with this cytolysis being abolished by depletion of the membrane cholesterol. Drosophila cells, which contain ergosterol as their major membrane sterol, were resistant to rALO-mediated cytolysis. In order to determine the molecular mechanism of this resistance, the interaction of rALO with model membranes comprised of POPC alone, or with a variety of structurally similar sterols including ergosterol, was probed using Biacore. Both rALO35,512 and rALO403,512 demonstrated robust binding to model membranes composed of POPC and cholesterol, with amount of protein bound proportional to the cholesterol content. Ergosterol supported greatly reduced binding of both rALO35,512 and rALO403,512, whereas other sterols tested did not support binding. The rALO403,512,membrane interaction demonstrated an equilibrium dissociation constant (KD) in the low nanomolar range, whereas rALO35,512 exhibited complex kinetics likely due to the multiple events involved in pore formation. These results establish the pivotal role of cholesterol in the action of rALO. The biosensor method developed to measure ALO recognition of cholesterol in a membrane environment could be extended to provide a platform for the screening of inhibitors of other membrane-binding proteins and peptides. Copyright© 2006 John Wiley & Sons, Ltd. [source]

A minor ,-structured conformation is the active state of a fusion peptide of vesicular stomatitis virus glycoprotein,

JOURNAL OF PEPTIDE SCIENCE, Issue 4 2008
Carolina G. Sarzedas
Abstract Entry of enveloped animal viruses into their host cells always depends on a step of membrane fusion triggered by conformational changes in viral envelope glycoproteins. Vesicular stomatitis virus (VSV) infection is mediated by virus spike glycoprotein G, which induces membrane fusion at the acidic environment of the endosomal compartment. In a previous work, we identified a specific sequence in the VSV G protein, comprising the residues 145,164, directly involved in membrane interaction and fusion. In the present work we studied the interaction of pep[145,164] with membranes using NMR to solve the structure of the peptide in two membrane-mimetic systems: SDS micelles and liposomes composed of phosphatidylcholine and phosphatidylserine (PC:PS vesicles). The presence of medium-range NOEs showed that the peptide has a tendency to form N - and C -terminal helical segments in the presence of SDS micelles. Analysis of the chemical shift index indicated helix,coil equilibrium for the C -terminal helix under all conditions studied. At pH 7.0, the N -terminal helix also displayed a helix,coil equilibrium when pep[145-164] was free in solution or in the presence of PC:PS. Remarkably, at the fusogenic pH, the region of the N -terminal helix in the presence of SDS or PC:PS presented a third conformational species that was in equilibrium with the helix and random coil. The N -terminal helix content decreases pH and the minor ,-structured conformation becomes more prevalent at the fusogenic pH. These data point to a ,-conformation as the fusogenic active structure-which is in agreement with the X-ray structure, which shows a ,-hairpin for the region corresponding to pep[145-164]. Copyright © 2007 European Peptide Society and John Wiley & Sons, Ltd. [source]

Parallel and antiparallel dimers of magainin 2: their interaction with phospholipid membrane and antibacterial activity

JOURNAL OF PEPTIDE SCIENCE, Issue 10 2002
Yasuhiro Mukai
Abstract Magainin 2 (M2) forms pores by associating with several other M2 molecules in lipid membranes and shows antibacterial activity. To examine the effect of M2 dimerization on biological activity and membrane interaction, parallel and antiparallel M2 dimers were prepared from two monomeric precursors. Antibacterial and haemolytic activities were enhanced by dimerization. CD measurements showed that both dimers and monomers have an ,-helical structure in the presence of lipid vesicles. Tryptophan fluorescence shift and KI quenching studies showed that all the peptides were more deeply embedded in acidic liposomes than in neutral liposomes. Experiments on dye-leakage activity and membrane translocation of peptides suggest that dimers and monomers form pores through lipid membranes, although the pore formation may be accompanied by membrane disturbance. Although dimerization of M2 increased the interaction activity with lipid membranes, no appreciable difference between the activities of parallel and antiparallel M2 dimers was observed. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd. [source]

Direct MinE,membrane interaction contributes to the proper localization of MinDE in E. coli

MOLECULAR MICROBIOLOGY, Issue 2 2010
Cheng-Wei Hsieh
Summary Dynamic oscillation of the Min system in Escherichia coli determines the placement of the division plane at the midcell. In addition to stimulating MinD ATPase activity, we report here that MinE can directly interact with the membrane and this interaction contributes to the proper MinDE localization and dynamics. The N-terminal domain of MinE is involved in direct contact between MinE and the membranes that may subsequently be stabilized by the C-terminal domain of MinE. In an in vitro system, MinE caused liposome deformation into membrane tubules, a property similar to that previously reported for MinD. We isolated a mutant MinE containing residue substitutions in R10, K11 and K12 that was fully capable of stimulating MinD ATPase activity, but was deficient in membrane binding. Importantly, this mutant was unable to support normal MinDE localization and oscillation, suggesting that direct MinE interaction with the membrane is critical for the dynamic behavior of the Min system. [source]

New insights into the cellular organization of the RNA processing and degradation machinery of Escherichia coli

MOLECULAR MICROBIOLOGY, Issue 4 2008
Aziz Taghbalout
Summary Ribonuclease E (RNase E) is a component of the Escherichia coli RNA degradosome, a multiprotein complex that also includes RNA helicase B (RhlB), polynucleotide phosphorylase (PNPase) and enolase. The degradosome plays a key role in RNA processing and degradation. The degradosomal proteins are organized as a cytoskeletal-like structure within the cell that has been thought to be associated with the cytoplasmic membrane. The article by Khemici et al. in the current issue of Molecular Microbiology reports that RNase E can directly interact with membrane phospholipids in vitro. The RNase E,membrane interaction is likely to play an important role in the membrane association of the degradosome system. These findings shed light on important but largely unexplored aspects of cellular structure and function, including the organization of the RNA processing machinery of the cell and of bacterial cytoskeletal elements in general. [source]

Protein kinase C activity in mouse eggs regulates gamete membrane interaction,

MOLECULAR REPRODUCTION & DEVELOPMENT, Issue 11 2007
Hiroto Akabane
Abstract Gamete membrane interaction is critical to initiate the development of a new organism. The signaling pathways governing this event, however, are poorly understood. In this report, we provide the first evidence that protein kinase C activity in mouse eggs plays a crucial role in the regulation of this process. Stimulating PKC activity in mouse eggs by phorbol 12-myristate 13-acetate (PMA) drastically inhibited the egg's membrane ability to bind and fuse with sperm. Surprisingly, this significant reduction of gamete membrane interaction was also observed in eggs treated with the PKC inhibitors staurosporine and calphostin c. In further analysis, we found that while no change of egg actin cytoskeleton was detected after either PMA or calphostin c treatment, the structural morphology of egg surface microvilli was severely altered in the PMA-treated eggs, but not in the calphostin c-treated eggs. Moreover, sperm, which bound but did not fuse with the eggs treated with the anti-CD9 antibody KMC8, were liberated from the egg membrane after PMA, but not calphostin c, treatment. Taken together, these results suggest that egg PKC may be precisely balanced to regulate gamete membrane interaction in a biphasic mode, and this biphasic regulation is executed through two different mechanisms. Mol. Reprod. Dev. 74: 1465,1472, 2007. © 2007 Wiley-Liss, Inc. [source]

Exploring the interactions of gliadins with model membranes: Effect of confined geometry and interfaces

BIOPOLYMERS, Issue 8 2009
Amélie Banc
Abstract Mechanisms leading to the assembly of wheat storage proteins into proteins bodies within the endoplasmic reticulum (ER) of endosperm cells are unresolved today. In this work, physical chemistry parameters which could be involved in these processes were explored. To model the confined environment of proteins within the ER, the dynamic behavior of ,-gliadins inserted inside lyotropic lamellar phases was studied using FRAP experiments. The evolution of the diffusion coefficient as a function of the lamellar periodicity enabled to propose the hypothesis of an interaction between ,-gliadins and membranes. This interaction was further studied with the help of phospholipid Langmuir monolayers. ,- and ,-gliadins were injected under DMPC and DMPG monolayers and the two-dimensional (2D) systems were studied by Brewster angle microscopy (BAM), polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS), and surface tension measurements. Results showed that both gliadins adsorbed under phospholipid monolayers, considered as biological membrane models, and formed micrometer-sized domains at equilibrium. However, their thicknesses, probed by reflectance measurements, were different: ,-gliadins aggregates displayed a constant thickness, consistent with a monolayer, while the thickness of ,-gliadins aggregates increased with the quantity of protein injected. These different behaviors could find some explanations in the difference of aminoacid sequence distribution: an alternate repeated - unrepeated domain within ,-gliadin sequence, while one unique repeated domain was present within ,-gliadin sequence. All these findings enabled to propose a model of gliadins self-assembly via a membrane interface and to highlight the predominant role of wheat prolamin repeated domain in the membrane interaction. In the biological context, these results would mean that the repeated domain could be considered as an anchor for the interaction with the ER membrane and a nucleus point for the formation and growth of protein bodies within endosperm cells. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 610,622, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source]

Proposal for molecular mechanism of thionins deduced from physico-chemical studies of plant toxins

CHEMICAL BIOLOGY & DRUG DESIGN, Issue 6 2004
B. Stec
Abstract:, We propose a molecular model for phospholipid membrane lysis by the ubiquitous plant toxins called thionins. Membrane lysis constitutes the first major effect exerted by these toxins that initiates a cascade of cytoplasmic events leading to cell death. X-ray crystallography, solution nuclear magnetic resonance (NMR) studies, small angle X-ray scattering and fluorescence spectroscopy provide evidence for the mechanism of membrane lysis. In the crystal structures of two thionins in the family, ,1 - and , -purothionins (MW: approximately 4.8 kDa), a phosphate ion and a glycerol molecule are modeled bound to the protein. 31P NMR experiments on the desalted toxins confirm phosphate-ion binding in solution. Evidence also comes from phospholipid partition experiments with radiolabeled toxins and with fluorescent phospholipids. This data permit a model of the phospholipid,protein complex to be built. Further, NMR experiments, one-dimensional (1D)- and two-dimensional (2D)-total correlation spectroscopy (TOCSY), carried out on the model compounds glycerol-3-phosphate (G3P) and short chain phospholipids, supported the predicted mode of phospholipid binding. The toxins' high positive charge, which renders them extremely soluble (>300 mg/mL), and the phospholipid-binding specificity suggest the toxin,membrane interaction is mediated by binding to patches of negatively charged phospholipids [phosphatidic acid (PA) or phosphatidyl serine (PS)] and their subsequent withdrawal. The formation of proteolipid complexes causes solubilization of the membrane and its lysis. The model suggests that the oligomerization may play a role in toxin's activation process and provides insight into the structural principles of protein,membrane interactions. [source]

Ion channel formation and membrane-linked pathologies of misfolded hydrophobic proteins: The role of dangerous unchaperoned molecules

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 9 2002
Joseph I Kourie
Summary 1.,Protein,membrane interaction includes the interaction of proteins with intrinsic receptors and ion transport pathways and with membrane lipids. Several hypothetical interaction models have been reported for peptide-induced membrane destabilization, including hydrophobic clustering, electrostatic interaction, electrostatic followed by hydrophobic interaction, wedge × type incorporation and hydrophobic mismatch. 2.,The present review focuses on the hypothesis of protein interaction with lipid membranes of those unchaperoned positively charged and misfolded proteins that have hydrophobic regions. We advance the hypothesis that protein misfolding that leads to the exposure of hydrophobic regions of proteins renders them potentially cytotoxic. Such proteins include prion, amyloid , protein (A,P), amylin, calcitonin, serum amyloid and C-type natriuretic peptides. These proteins have the ability to interact with lipid membranes, thereby inducing membrane damage and cell malfunction. 3.,We propose that the most significant mechanism of membrane damage induced by hydrophobic misfolded proteins is mediated via the formation of ion channels. The hydrophobicity based toxicity of several proteins linked to neurodegenerative pathologies is similar to those observed for antibacterial toxins and viral proteins. 4.,It is hypothesized that the membrane damage induced by amyloids, antibacterial toxins and viral proteins represents a common mechanism for cell malfunction, which underlies the associated pathologies and cytotoxicity of such proteins. [source]

Cell contact interaction between adipose-derived stromal cells and allo-activated T lymphocytes

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 12 2009
Monique E. Quaedackers
Abstract Mesenchymal stromal cells regulate immune cell function via the secretion of soluble factors. Cell membrane interactions between these cell types may play an additional role. Here, we demonstrate that subpopulations of allo-activated T cells are capable of binding to human adipose-derived stromal cells (ASC). The bound T-cell population contained CD8+ T cells and was enriched for CD4,CD8, T cells, whereas the proportion of CD4+ T cells was decreased compared with the non-bound T-cell population. Bound CD4+ T cells had high proliferative activity and increased CD25 and FoxP3 expression. However, they also expressed CD127, excluding regulatory T-cell function. In CD8+ T cells, IL-2 sensitivity, as determined by the analysis of phosphorylated STAT5, was lower in the presence of ASC and even lower in bound cells. In contrast, IL-2-induced phosphorylated STAT5 levels were higher in bound CD4+ T cells than in non-bound CD4+ T cells. Additionally, pro-proliferative TGF-, signalling via endoglin and SMAD1/5/8 phosphorylation was detected in bound CD4+ T cells. Even after prolonged co-culture with ASC, the activated phenotype of bound CD4+ T cells persisted. In conclusion, these results demonstrate that the binding of lymphocytes to ASC represents an immunomodulatory mechanism in which CD8+ T cells are inhibited in their responsiveness to pro-inflammatory stimuli and reactive CD4+ T cells are depleted from the immune response. [source]

Domain V of m-calpain shows the potential to form an oblique-orientated ,-helix, which may modulate the enzyme's activity via interactions with anionic lipid

FEBS JOURNAL, Issue 22 2002
Klaus Brandenburg
The activity of m-calpain, a heterodimeric, Ca2+ -dependent cysteine protease appears to be modulated by membrane interactions involving oblique-orientated ,-helix formation by a segment, GTAMRILGGVI, in the protein's smaller subunit. Here, graphical and hydrophobic moment-based analyses predicted that this segment may form an ,-helix with strong structural resemblance to the influenza virus peptide, HA2, a known oblique-orientated ,-helix former. Fourier transform infrared spectroscopy showed that a peptide homologue of the GTAMRILGGVI segment, VP1, adopted low levels of ,-helical structure (, 20%) in the presence of zwitterionic lipid and induced a minor decrease (3 °C) in the gel to liquid-crystalline phase transition temperature, TC, of the hydrocarbon chains of zwitterionic membranes, suggesting interaction with the lipid headgroup region. In contrast, VP1 adopted high levels of ,-helical structure (65%) in the presence of anionic lipid, induced a large increase (10 °C) in the TC of anionic membranes, and showed high levels of anionic lipid monolayer penetration (,SP = 5.5 mN·m,1), suggesting deep levels of membrane penetration. VP1 showed strong haemolytic ability (LD50 = 1.45 mm), but in the presence of ionic agents, this ability, and that of VP1 to penetrate anionic lipid monolayers, was greatly reduced. In combination, our results suggest that m-calpain domain V may penetrate membranes via the adoption of an oblique-orientated ,-helix and electrostatic interactions. We speculate that these interactions may involve snorkelling by an arginine residue located in the polar face of this ,-helix. [source]

Aggregation and membrane permeabilizing properties of designed histidine-containing cationic linear peptide antibiotics,

JOURNAL OF PEPTIDE SCIENCE, Issue 4 2008
Arnaud Marquette
Abstract Members of the LAH4 family of cationic linear peptide antibiotics have been designed to form amphipathic helical structures in membrane environments and switch from alignments parallel to the bilayer surface to transmembrane orientations in a pH-dependent manner. Here the aggregation in aqueous buffer of two members of the family has been investigated by DLS. The peptides form monomers or small oligomers at pH = 5 but associate into nano-sized aggregates at physiological pH. The diameter of these latter complexes can be considerably reduced by sonication. Furthermore, the membrane interactions of the various supramolecular aggregates with POPC or mixed POPC/POPS vesicles have been investigated in calcein-release assays. In all the cases tested, the large preformed oligomeric peptide aggregates of 20,40 nm in size were more active than the structures with the smallest hydrodynamic radii in releasing the fluorescent dye from LUV. In contrast, the relative activity after sonication depends on the specific environment tested. The data suggest that these amphiphiles form micellar structures and support the notion that they can act in a manner comparable to detergents. Copyright © 2007 European Peptide Society and John Wiley & Sons, Ltd. [source]

Structural studies and model membrane interactions of two peptides derived from bovine lactoferricin

JOURNAL OF PEPTIDE SCIENCE, Issue 7 2005
Leonard T. Nguyen
Abstract The powerful antimicrobial properties of bovine lactoferricin (LfcinB) make it attractive for the development of new antimicrobial agents. An 11-residue linear peptide portion of LfcinB has been reported to have similar antimicrobial activity to lactoferricin itself, but with lower hemolytic activity. The membrane-binding and membrane-perturbing properties of this peptide were studied together with an amidated synthetic version with an added disulfide bond, which was designed to confer increased stability and possibly activity. The antimicrobial and cytotoxic properties of the peptides were measured against Staphylococcus aureus and Escherichia coli and by hemolysis assays. The peptides were also tested in an anti-cancer assay against neuroblastoma cell lines. Vesicle disruption caused by these LfcinB derivatives was studied using the fluorescent reporter molecule calcein. The extent of burial of the two Trp residues in membrane mimetic environments were quantitated by fluorescence. Finally, the solution NMR structures of the peptides bound to SDS micelles were determined to provide insight into their membrane bound state. The cyclic peptide was found to have greater antimicrobial potency than its linear counterpart. Consistent with this property, the two Trp residues of the modified peptide were suggested to be embedded deeper into the membrane. Although both peptides adopt an amphipathic structure without any regular ,-helical or ß-sheet conformation, the 3D-structures revealed a clearer partitioning of the cationic and hydrophobic faces for the cyclic peptide. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd. [source]

Variable-temperature Raman spectro-microscopy for a comprehensive analysis of the conformational order in PEGylated lipids

JOURNAL OF RAMAN SPECTROSCOPY, Issue 4 2009
Rajan K. Bista
Abstract The investigation of phase transitions and associated changes in the conformational order of lipids is of importance in various research areas dealing with phenomena such as the formation and fusion of vesicles, transmembrane diffusion and membrane interactions with drugs and proteins. In this article, we have focused on the study of thermotropic phase behaviors and associated changes in the conformational order of two newly developed synthetic PEGylated lipids trademarked as QuSomes. In contrast to conventional phospholipids, this new kind of lipid forms liposomes spontaneously upon hydration, without the supply of external activation energy. Variable-temperature Raman spectro-microscopy has been employed in order to plot the transition temperature profiles showing the phase behavior of these new lipids composed of 1,2-dimyristoyl-rac-glycerol-3-dodecaethylene glycol (GDM-12) and 1,2-distearoyl-rac-glycerol-3-triicosaethylene glycol (GDS-23). Furthermore, several spectral indicators were calculated and correlated which allowed for the deduction of various aspects of molecular structure as well as intramolecular motion and intermolecular interactions. To confirm the observations, differential scanning calorimetry (DSC) was applied and revealed a good agreement with the Raman spectroscopy results. Finally, this information may find application in various studies including the development of lipid-based novel substances and drug delivery systems. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Protein,membrane interactions: blood clotting on nanoscale bilayers

JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 2009
J. H. MORRISSEY
Summary., The clotting cascade requires the assembly of protease,cofactor complexes on membranes with exposed anionic phospholipids. Despite their importance, protein,membrane interactions in clotting remain relatively poorly understood. Calcium ions are known to induce anionic phospholipids to cluster, and we propose that clotting proteins assemble preferentially on such anionic lipid-rich microdomains. Until recently, there was no way to control the partitioning of clotting proteins into or out of specific membrane microdomains, so experimenters only knew the average contributions of phospholipids to blood clotting. The development of nanoscale membrane bilayers (Nanodiscs) has now allowed us to probe, with nanometer resolution, how local variations in phospholipid composition regulate the activity of key protease,cofactor complexes in blood clotting. Furthermore, exciting new progress in solid-state NMR and large-scale molecular dynamics simulations allow structural insights into interactions between proteins and membrane surfaces with atomic resolution. [source]

Membrane type-1 matrix metalloproteinase stimulates tumour cell-induced platelet aggregation: role of receptor glycoproteins

BRITISH JOURNAL OF PHARMACOLOGY, Issue 2 2004
David Alonso-Escolano
Matrix metalloproteinase-2 (MMP-2) plays a role in agonist- and tumour cell-induced platelet aggregation (TCIPA). MMP-2 is synthesized as a proenzyme and is activated at the cell surface by membrane type-1 matrix metalloproteinase (MT1-MMP, MMP-14). The significance of tumour cell-associated MT1-MMP for TCIPA was investigated using human breast carcinoma MCF7 cells stably coexpressing the integrin ,v,3 with MT1-MMP, cells expressing ,v,3 alone and mock-transfected cells. Western blot and zymography confirmed that ,v,3/MT1-MMP cells expressed MT1-MMP and efficiently processed proMMP-2 to MMP-2. Aggregometry, phase-contrast and transmission electron microscopy and flow cytometry were used to characterize TCIPA induced by MCF7 cell lines. The aggregating potency of cells was: ,v,3/MT1-MMP >,v,3=mock cells, as shown by aggregometry and phase-contrast microscopy. Electron microscopy revealed close, membrane,membrane interactions between activated platelets and ,v,3/MT1-MMP cells during TCIPA. Inhibition of MMP-2 with the neutralizing anti-MMP-2 antibody (5 ,g ml,1) and o -phenanthroline (100 ,M) reduced aggregation induced by ,v,3/MT1-MMP cells. TCIPA induced by ,v,3/MT1-MMP cells was also reduced by inhibiting the generation and actions of ADP with apyrase (250 ,g ml,1) and 2-methylthio-AMP (2-MeSAMP) (30 ,M), but not N6 -methyl-2,-deoxyadenosine-3,,5,-bisphosphate (MRS2179) (30 ,M). Flow cytometry demonstrated that TCIPA enhanced expression of glycoprotein (GP) Ib and IIb/IIIa receptors not only on platelets but also on breast cancer cells. Thus, (a) human breast carcinoma cell surface-associated MT1-MMP, via activating proMMP-2, stimulates TCIPA; (b) ADP amplifies the effects of MMPs via stimulation of P2Y12 receptors and (c) both tumour- and platelet-derived GPIb and GPIIb/IIIa are involved in the aggregatory effects of MT1-MMP. British Journal of Pharmacology (2004) 141, 241,252. doi:10.1038/sj.bjp.0705606 [source]