Articoli di riviste: "Lipid-bilayer insertion"

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Khalid, Syma, Peter J. Bond, John Holyoake, Robert W. Hawtin e Mark S. P. Sansom. "DNA and lipid bilayers: self-assembly and insertion". Journal of The Royal Society Interface 5, suppl_3 (2 settembre 2008): 241–50. http://dx.doi.org/10.1098/rsif.2008.0239.focus.

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DNA–lipid complexes are of biomedical importance as delivery vectors for gene therapy. To gain insight into the interactions of DNA with zwitterionic and cationic (dimyristoyltrimethylammonium propane (DMTAP)) lipids, we have used coarse-grained molecular dynamics simulations to study the self-assembly of DPPC and DPPC/DMTAP lipid bilayers in the presence of a DNA dodecamer. We observed the spontaneous formation of lipid bilayers from initial systems containing randomly placed lipids, water–counterions and DNA. In both the DPPC and DPPC/DMTAP simulations, the DNA molecule is located at the water–lipid headgroup interface, lying approximately parallel to the plane of the bilayer. We have also calculated the potential of mean force for transferring a DNA dodecamer through a DPPC/DMTAP bilayer. A high energetic barrier to DNA insertion into the hydrophobic core of the bilayer is observed. The DNA adopts a transmembrane orientation only in this region. Local bilayer deformation in the vicinity of the DNA molecule is observed, largely as a result of the DNA–DMTAP headgroup attraction.

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Slaybaugh, Gregory, Dhammika Weerakkody, Donald M. Engelman, Oleg A. Andreev e Yana K. Reshetnyak. "Kinetics of pHLIP peptide insertion into and exit from a membrane". Proceedings of the National Academy of Sciences 117, n. 22 (14 maggio 2020): 12095–100. http://dx.doi.org/10.1073/pnas.1917857117.

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To advance mechanistic understanding of membrane-associated peptide folding and insertion, we have studied the kinetics of three single tryptophan pHLIP (pH-Low Insertion Peptide) variants, where tryptophan residues are located near the N terminus, near the middle, and near the inserting C-terminal end of the pHLIP transmembrane helix. Single-tryptophan pHLIP variants allowed us to probe different parts of the peptide in the pathways of peptide insertion into the lipid bilayer (triggered by a pH drop) and peptide exit from the bilayer (triggered by a rise in pH). By using pH jumps of different magnitudes, we slowed down the processes and established the intermediates that helped us to understand the principles of insertion and exit. The obtained results should also aid the applications in medicine that are now entering the clinic.

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SHEPHERD, Craig M., Hans J. VOGEL e D. Peter TIELEMAN. "Interactions of the designed antimicrobial peptide MB21 and truncated dermaseptin S3 with lipid bilayers: molecular-dynamics simulations". Biochemical Journal 370, n. 1 (15 febbraio 2003): 233–43. http://dx.doi.org/10.1042/bj20021255.

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Molecular-dynamics simulations covering 30ns of both a natural and a synthetic antimicrobial peptide in the presence of a zwitterionic lipid bilayer were performed. In both simulations, copies of the peptides were placed in an α-helical conformation on either side of the bilayer about 10Å (1Å = 0.1nm) from the interface, with either the hydrophobic or the positively charged face of the helix directed toward the bilayer surface. The degree of peptide—lipid interaction was dependent on the starting configuration: surface binding and subsequent penetration of the bilayer was observed for the hydrophobically oriented peptides, while the charge-oriented peptides demonstrated at most partial surface binding. Aromatic residues near the N-termini of the peptides appear to play an important role in driving peptide—lipid interactions. A correlation between the extent of peptide—lipid interactions and helical stability was observed in the simulations. Insertion of the peptides into the bilayer caused a dramatic increase in the lateral area per lipid and decrease in the bilayer thickness, resulting in substantial disordering of the lipid chains. Results from the simulations are consistent with early stages of proposed mechanisms for the lytic activity of antimicrobial peptides. In addition to these ‘free’ simulations, 25ns simulations were carried out with the peptides constrained at three different distances relative to the bilayer interface. The constraint forces are in agreement with the extent of peptide—bilayer insertion observed in the free simulations.

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Reshetnyak, Yana K., Oleg A. Andreev, Michael Segala, Vladislav S. Markin e Donald M. Engelman. "Energetics of peptide (pHLIP) binding to and folding across a lipid bilayer membrane". Proceedings of the National Academy of Sciences 105, n. 40 (30 settembre 2008): 15340–45. http://dx.doi.org/10.1073/pnas.0804746105.

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The pH low-insertion peptide (pHLIP) serves as a model system for peptide insertion and folding across a lipid bilayer. It has three general states: (I) soluble in water or (II) bound to the surface of a lipid bilayer as an unstructured monomer, and (III) inserted across the bilayer as a monomeric α-helix. We used fluorescence spectroscopy and isothermal titration calorimetry to study the interactions of pHLIP with a palmitoyloleoylphosphatidylcholine (POPC) lipid bilayer and to calculate the transition energies between states. We found that the Gibbs free energy of binding to a POPC surface at low pHLIP concentration (state I–state II transition) at 37°C is approximately −7 kcal/mol near neutral pH and that the free energy of insertion and folding across a lipid bilayer at low pH (state II–state III transition) is nearly −2 kcal/mol. We discuss a number of related thermodynamic parameters from our measurements. Besides its fundamental interest as a model system for the study of membrane protein folding, pHLIP has utility as an agent to target diseased tissues and translocate molecules through the membrane into the cytoplasm of cells in environments with elevated levels of extracellular acidity, as in cancer and inflammation. The results give the amount of energy that might be used to move cargo molecules across a membrane.

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Salvador-Castell, Marta, Nicholas J. Brooks, Roland Winter, Judith Peters e Philippe M. Oger. "Non-Polar Lipids as Regulators of Membrane Properties in Archaeal Lipid Bilayer Mimics". International Journal of Molecular Sciences 22, n. 11 (4 giugno 2021): 6087. http://dx.doi.org/10.3390/ijms22116087.

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The modification of archaeal lipid bilayer properties by the insertion of apolar molecules in the lipid bilayer midplane has been proposed to support cell membrane adaptation to extreme environmental conditions of temperature and hydrostatic pressure. In this work, we characterize the insertion effects of the apolar polyisoprenoid squalane on the permeability and fluidity of archaeal model membrane bilayers, composed of lipid analogues. We have monitored large molecule and proton permeability and Laurdan generalized polarization from lipid vesicles as a function of temperature and hydrostatic pressure. Even at low concentration, squalane (1 mol%) is able to enhance solute permeation by increasing membrane fluidity, but at the same time, to decrease proton permeability of the lipid bilayer. The squalane physicochemical impact on membrane properties are congruent with a possible role of apolar intercalants on the adaptation of Archaea to extreme conditions. In addition, such intercalant might be used to cheaply create or modify chemically resistant liposomes (archeaosomes) for drug delivery.

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Jo, Euijung, Jack Blazyk e Joan M. Boggs. "Insertion of Magainin into the Lipid Bilayer Detected Using Lipid Photolabels†". Biochemistry 37, n. 39 (settembre 1998): 13791–99. http://dx.doi.org/10.1021/bi980855c.

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Yue, Tongtao, Mingbin Sun, Shuai Zhang, Hao Ren, Baosheng Ge e Fang Huang. "How transmembrane peptides insert and orientate in biomembranes: a combined experimental and simulation study". Physical Chemistry Chemical Physics 18, n. 26 (2016): 17483–94. http://dx.doi.org/10.1039/c6cp01133k.

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Hyland, Caroline, Laurent Vuillard, Colin Hughes e Vassilis Koronakis. "Membrane Interaction of Escherichia coliHemolysin: Flotation and Insertion-Dependent Labeling by Phospholipid Vesicles". Journal of Bacteriology 183, n. 18 (15 settembre 2001): 5364–70. http://dx.doi.org/10.1128/jb.183.18.5364-5370.2001.

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ABSTRACT The 1,024-amino-acid acylated hemolysin of Escherichia coli subverts host cell functions and causes cell lysis. Both activities require insertion of the toxin into target mammalian cell membranes. To identify directly the principal toxin sequences dictating membrane binding and insertion, we assayed the lipid bilayer interaction of native protoxin, stably active toxin, and recombinant peptides. Binding was assessed by flotation of protein-liposome mixtures through density gradients, and insertion was assessed by labeling with a photoactivatable probe incorporated into the target lipid bilayer. Both the active acylated hemolysin and the inactive unacylated protoxin were able to bind and also insert. Ca2+binding, which is required for toxin activity, did not influence the in vitro interaction with liposomes. Three overlapping large peptides were expressed separately. A C-terminal peptide including residues 601 to 1024 did not interact in either assay. An internal peptide spanning residues 496 to 831, including the two acylation sites, bound to phospholipid vesicles and showed a low level of insertion-dependent labeling. In vitro acylation had no effect on the bilayer interaction of either this peptide or the full-length protoxin. An N-terminal peptide comprising residues 1 to 520 also bound to phospholipid vesicles and showed strong insertion-dependent labeling, ca. 5- to 25-fold that of the internal peptide. Generation of five smaller peptides from the N-terminal region identified the principal determinant of lipid insertion as the hydrophobic sequence encompassing residues 177 to 411, which is conserved among hemolysin-related toxins.

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Weerakkody, Dhammika, Oleg A. Andreev e Yana K. Reshetnyak. "Insertion into lipid bilayer of truncated pHLIP ® peptide". Biochemistry and Biophysics Reports 8 (dicembre 2016): 290–95. http://dx.doi.org/10.1016/j.bbrep.2016.10.001.

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Takahashi, Akira, Chiyo Yamamoto, Toshio Kodama, Kanami Yamashita, Nagakatsu Harada, Masayuki Nakano, Takeshi Honda e Yutaka Nakaya. "Pore Formation of Thermostable Direct Hemolysin Secreted from Vibrio parahaemolyticus in Lipid Bilayers". International Journal of Toxicology 25, n. 5 (settembre 2006): 409–18. http://dx.doi.org/10.1080/10915810600868181.

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Vibrio parahaemolyticus secretes thermostable direct hemolysin (TDH), a major virulence factor. Earlier studies report that TDH is a pore-forming toxin. However, the characteristics of pores formed by TDH in the lipid bilayer, which is permeable to small ions, remain to be elucidated. Ion channel-like activities were observed in lipid bilayers containing TDH. Three types of conductance were identified. All the channels displayed relatively low ion selectivity, and similar ion permeability. The Cl− channel inhibitors, DIDS, glybenclamide, and NPPB, did not affect the channel activity of pores formed by TDH. R7, a mutant toxin of TDH, also forms pores with channel-like activity in lipid bilayers. The ion permeability of these channels is similar to that of TDH. R7 binds cultured cells and liposomes to a lower extent, compared to TDH. R7 does not display significant hemolytic activity and cell cytotoxicity, possibly owing to the difficulty of insertion into lipid membranes. Once R7 is assembled within lipid membranes, it may assume the same structure as TDH. The authors propose that the single glycine at position 62, substituted with serine in the R7 mutant toxin, plays an important role in TDH insertion into the lipid bilayer.

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Cheng, Kwan Hon, Liming Qiu, Sara Y. Cheng e Mark W. Vaughn. "Lipid insertion domain unfolding regulates protein orientational transition behavior in a lipid bilayer". Biophysical Chemistry 206 (novembre 2015): 22–39. http://dx.doi.org/10.1016/j.bpc.2015.06.011.

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Babakhani, Arneh, Alemayehu A. Gorfe, Judy E. Kim e J. Andrew McCammon. "Thermodynamics of Peptide Insertion and Aggregation in a Lipid Bilayer". Journal of Physical Chemistry B 112, n. 34 (agosto 2008): 10528–34. http://dx.doi.org/10.1021/jp804710v.

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Ramadurai, Sivaramakrishnan, Ananiy Kohut, Nirod Kumar Sarangi, Oksana Zholobko, Vladimir A. Baulin, Andriy Voronov e Tia E. Keyes. "Macromolecular inversion-driven polymer insertion into model lipid bilayer membranes". Journal of Colloid and Interface Science 542 (aprile 2019): 483–94. http://dx.doi.org/10.1016/j.jcis.2019.01.093.

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Chetwynd, Alan, Chze Ling Wee, Benjamin A. Hall e Mark S. P. Sansom. "The Energetics of Transmembrane Helix Insertion into a Lipid Bilayer". Biophysical Journal 99, n. 8 (ottobre 2010): 2534–40. http://dx.doi.org/10.1016/j.bpj.2010.08.002.

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Smirnova, Elena Yu, e Andrey A. Anosov. "Bilayer Lipid Membrane as Memcapacitance: Capacitance–Voltage Pinched Hysteresis and Negative Insertion Conductance". Membranes 13, n. 1 (11 gennaio 2023): 97. http://dx.doi.org/10.3390/membranes13010097.

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Inelastic (dissipative) effects of different natures in lipid bilayer membranes can lead to hysteresis phenomena. Early, it was shown that lipid bilayer membranes, under the action of a periodic sinusoidal voltage, demonstrate pinched-hysteresis loops in the experimental capacitance–voltage dependences and are almost the only example of the physical implementation of memcapacitance. Here, we propose an equivalent circuit and mathematical framework for analyzing the dynamic nonlinear current response of a lipid bilayer membrane as an externally controlled memcapacitance. Solving a nonlinear differential equation for the equivalent circuit of a membrane in the form of a parallel connection of a nonlinear viscoelastic capacitor and an active resistance using the small parameter method, we obtain explicit analytical dependences for the current response of the membrane and pinched-hysteresis loops. The explicit solutions and their comparison with experimental data allow us to identify the lumped equivalent circuit parameters that govern the memcapacitor behavior of the membrane and hence the magnitude of the hysteresis. We quantify the memcapacitance hysteresis in terms of negative work done by the control signal. An analysis of the formulas leads to the conclusion that the determining factor for the appearance of pinched hysteresis is the type of nonlinear dependence of the device capacitance on voltage.

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Ouberai, Myriam M., Juan Wang, Marcus J. Swann, Celine Galvagnion, Tim Guilliams, Christopher M. Dobson e Mark E. Welland. "α-Synuclein Senses Lipid Packing Defects and Induces Lateral Expansion of Lipids Leading to Membrane Remodeling". Journal of Biological Chemistry 288, n. 29 (5 giugno 2013): 20883–95. http://dx.doi.org/10.1074/jbc.m113.478297.

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There is increasing evidence for the involvement of lipid membranes in both the functional and pathological properties of α-synuclein (α-Syn). Despite many investigations to characterize the binding of α-Syn to membranes, there is still a lack of understanding of the binding mode linking the properties of lipid membranes to α-Syn insertion into these dynamic structures. Using a combination of an optical biosensing technique and in situ atomic force microscopy, we show that the binding strength of α-Syn is related to the specificity of the lipid environment (the lipid chemistry and steric properties within a bilayer structure) and to the ability of the membranes to accommodate and remodel upon the interaction of α-Syn with lipid membranes. We show that this interaction results in the insertion of α-Syn into the region of the headgroups, inducing a lateral expansion of lipid molecules that can progress to further bilayer remodeling, such as membrane thinning and expansion of lipids out of the membrane plane. We provide new insights into the affinity of α-Syn for lipid packing defects found in vesicles of high curvature and in planar membranes with cone-shaped lipids and suggest a comprehensive model of the interaction between α-Syn and lipid bilayers. The ability of α-Syn to sense lipid packing defects and to remodel membrane structure supports its proposed role in vesicle trafficking.

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Harris, Nicola J., Kalypso Charalambous, Heather E. Findlay e Paula J. Booth. "Lipids modulate the insertion and folding of the nascent chains of alpha helical membrane proteins". Biochemical Society Transactions 46, n. 5 (6 settembre 2018): 1355–66. http://dx.doi.org/10.1042/bst20170424.

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Membrane proteins must be inserted into a membrane and folded into their correct structure to function correctly. This insertion occurs during translation and synthesis by the ribosome for most α-helical membrane proteins. Precisely how this co-translational insertion and folding occurs, and the role played by the surrounding lipids, is still not understood. Most of the work on the influence of the lipid environment on folding and insertion has focussed on denatured, fully translated proteins, and thus does not replicate folding during unidirectional elongation of nascent chains that occurs in the cell. This review aims to highlight recent advances in elucidating lipid composition and bilayer properties optimal for insertion and folding of nascent chains in the membrane and in the assembly of oligomeric proteins.

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Zheng, Hui, Sungsoo Lee, Marc C. Llaguno e Qiu-Xing Jiang. "bSUM: A bead-supported unilamellar membrane system facilitating unidirectional insertion of membrane proteins into giant vesicles". Journal of General Physiology 147, n. 1 (28 dicembre 2015): 77–93. http://dx.doi.org/10.1085/jgp.201511448.

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Fused or giant vesicles, planar lipid bilayers, a droplet membrane system, and planar-supported membranes have been developed to incorporate membrane proteins for the electrical and biophysical analysis of such proteins or the bilayer properties. However, it remains difficult to incorporate membrane proteins, including ion channels, into reconstituted membrane systems that allow easy control of operational dimensions, incorporation orientation of the membrane proteins, and lipid composition of membranes. Here, using a newly developed chemical engineering procedure, we report on a bead-supported unilamellar membrane (bSUM) system that allows good control over membrane dimension, protein orientation, and lipid composition. Our new system uses specific ligands to facilitate the unidirectional incorporation of membrane proteins into lipid bilayers. Cryo–electron microscopic imaging demonstrates the unilamellar nature of the bSUMs. Electrical recordings from voltage-gated ion channels in bSUMs of varying diameters demonstrate the versatility of the new system. Using KvAP as a model system, we show that compared with other in vitro membrane systems, the bSUMs have the following advantages: (a) a major fraction of channels are orientated in a controlled way; (b) the channels mediate the formation of the lipid bilayer; (c) there is one and only one bilayer membrane on each bead; (d) the lipid composition can be controlled and the bSUM size is also under experimental control over a range of 0.2–20 µm; (e) the channel activity can be recorded by patch clamp using a planar electrode; and (f) the voltage-clamp speed (0.2–0.5 ms) of the bSUM on a planar electrode is fast, making it suitable to study ion channels with fast gating kinetics. Our observations suggest that the chemically engineered bSUMs afford a novel platform for studying lipid–protein interactions in membranes of varying lipid composition and may be useful for other applications, such as targeted delivery and single-molecule imaging.

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Martín, César, M. Asunción Requero, Jiri Masin, Ivo Konopasek, Félix M. Goñi, Peter Sebo e Helena Ostolaza. "Membrane Restructuring by Bordetella pertussis Adenylate Cyclase Toxin, a Member of the RTX Toxin Family". Journal of Bacteriology 186, n. 12 (15 giugno 2004): 3760–65. http://dx.doi.org/10.1128/jb.186.12.3760-3765.2004.

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ABSTRACT Adenylate cyclase toxin (ACT) is secreted by Bordetella pertussis, the bacterium causing whooping cough. ACT is a member of the RTX (repeats in toxin) family of toxins, and like other members in the family, it may bind cell membranes and cause disruption of the permeability barrier, leading to efflux of cell contents. The present paper summarizes studies performed on cell and model membranes with the aim of understanding the mechanism of toxin insertion and membrane restructuring leading to release of contents. ACT does not necessarily require a protein receptor to bind the membrane bilayer, and this may explain its broad range of host cell types. In fact, red blood cells and liposomes (large unilamellar vesicles) display similar sensitivities to ACT. A varying liposomal bilayer composition leads to significant changes in ACT-induced membrane lysis, measured as efflux of fluorescent vesicle contents. Phosphatidylethanolamine (PE), a lipid that favors formation of nonlamellar (inverted hexagonal) phases, stimulated ACT-promoted efflux. Conversely, lysophosphatidylcholine, a micelle-forming lipid that opposes the formation of inverted nonlamellar phases, inhibited ACT-induced efflux in a dose-dependent manner and neutralized the stimulatory effect of PE. These results strongly suggest that ACT-induced efflux is mediated by transient inverted nonlamellar lipid structures. Cholesterol, a lipid that favors inverted nonlamellar phase formation and also increases the static order of phospholipid hydrocarbon chains, among other effects, also enhanced ACT-induced liposomal efflux. Moreover, the use of a recently developed fluorescence assay technique allowed the detection of trans-bilayer (flip-flop) lipid motion simultaneous with efflux. Lipid flip-flop further confirms the formation of transient nonlamellar lipid structures as a result of ACT insertion in bilayers.

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Longo, M. L. "Flow-immunofluorescent studies of lung surfactant protein (SP-B)". Proceedings, annual meeting, Electron Microscopy Society of America 49 (agosto 1991): 254–55. http://dx.doi.org/10.1017/s0424820100085575.

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Respiratory distress syndrome (RDS), a life threatening disorder, occurs if a lipid-protein complex which lines the airspaces of the lungs is compromised. Successful treatment of RDS has been reported with a vesicular dispersion containing dipalmitoylphosphatidylcholine (DPPC), egg phosphatidylglycerol (egg PG), palmitic acid and lung surfactant protein, SP-B. It has been hypothesized that amphipathic regions of SP-B are important in these synthetic lung surfactants as they serve as a point of insertion for the protein into the lipid bilayer. Therefore two amphipathic peptides, SP-B(l-25) and SP-B(49-66), were synthesized to use in reconstitution studies. The incorporation of SP-B(l-25) into lipid bilayer has been visualized using immunofluorescent tagging in a specially designed flow-chamber.

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DUBOVSKII, Peter V., Dmitry M. LESOVOY, Maxim A. DUBINNYI, Anastasiya G. KONSHINA, Yuri N. UTKIN, Roman G. EFREMOV e Alexander S. ARSENIEV. "Interaction of three-finger toxins with phospholipid membranes: comparison of S- and P-type cytotoxins". Biochemical Journal 387, n. 3 (26 aprile 2005): 807–15. http://dx.doi.org/10.1042/bj20041814.

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The CTs (cytotoxins) I and II are positively charged three-finger folded proteins from venom of Naja oxiana (the Central Asian cobra). They belong to S- and P-type respectively based on Ser-28 and Pro-30 residues within a putative phospholipid bilayer binding site. Previously, we investigated the interaction of CTII with multilamellar liposomes of dipalmitoylphosphatidylglycerol by wide-line 31P-NMR spectroscopy. To compare interactions of these proteins with phospholipids, we investigated the interaction of CTI with the multilamellar liposomes of dipalmitoylphosphatidylglycerol analogously. The effect of CTI on the chemical shielding anisotropy and deformation of the liposomes in the magnetic field was determined at different temperatures and lipid/protein ratios. It was found that both the proteins do not affect lipid organization in the gel state. In the liquid crystalline state of the bilayer they disturb lipid packing. To get insight into the interactions of the toxins with membranes, Monte Carlo simulations of CTI and CTII in the presence of the bilayer membrane were performed. It was found that both the toxins penetrate into the bilayer with the tips of all the three loops. However, the free-energy gain on membrane insertion of CTI is smaller (by ≈7 kcal/mol; 1 kcal≡4.184 kJ) when compared with CTII, because of the lower hydrophobicity of the membrane-binding site of CTI. These results clearly demonstrate that the P-type cytotoxins interact with membranes stronger than those of the S-type, although the mode of the membrane insertion is similar for both the types.

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Osman, Peter, Scott Martin, Dusan Milojevic, Charles Tansey e Frances Separovic. "Optical Modulation of the Insertion of Gramicidin into Bilayer Lipid Membranes". Langmuir 14, n. 15 (luglio 1998): 4238–42. http://dx.doi.org/10.1021/la9801357.

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Nakatani, Koji, Tomoyuki Morita e Shunsaku Kimura. "Vertical and Directional Insertion of Helical Peptide into Lipid Bilayer Membrane". Langmuir 23, n. 13 (giugno 2007): 7170–77. http://dx.doi.org/10.1021/la7002723.

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Wang, Kathleen F., Ramanathan Nagarajan e Terri A. Camesano. "Antimicrobial peptide alamethicin insertion into lipid bilayer: A QCM-D exploration". Colloids and Surfaces B: Biointerfaces 116 (aprile 2014): 472–81. http://dx.doi.org/10.1016/j.colsurfb.2014.01.036.

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Werz, Emma, e Helmut Rosemeyer. "Terminal lipophilization of a unique DNA dodecamer by various nucleolipid headgroups: Their incorporation into artificial lipid bilayers and hydrodynamic properties". Beilstein Journal of Organic Chemistry 11 (1 giugno 2015): 913–29. http://dx.doi.org/10.3762/bjoc.11.103.

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A series of six cyanine-5-labeled oligonucleotides (LONs 10–15), each terminally lipophilized with different nucleolipid head groups, were synthesized using the recently prepared phosphoramidites 4b–9b. The insertion of the LONs within an artificial lipid bilayer, composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), was studied by single molecule fluorescence spectroscopy and microscopy with the help of an optically transparent microfluidic sample carrier with perfusion capabilities. The incorporation of the lipo-oligonucleotides into the bilayer was studied with respect to efficiency (maximal bilayer brightness) as well as stability against perfusion (final stable bilayer brightness). Attempts to correlate these parameters with the log P values of the corresponding nucleolipid head groups failed, a result which clearly demonstrates that not only the lipophilicity but mainly the chemical structure and topology of the head group is of decisive importance for the optimal interaction of a lipo-oligonucleotide with an artificial lipid bilayer. Moreover, fluorescence half-live and diffusion time values were measured to determine the diffusion coefficients of the lipo-oligonucleotides.

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Mironov, Alexander A., Anna Mironov, Jure Derganc e Galina V. Beznoussenko. "Membrane Curvature, Trans-Membrane Area Asymmetry, Budding, Fission and Organelle Geometry". International Journal of Molecular Sciences 21, n. 20 (14 ottobre 2020): 7594. http://dx.doi.org/10.3390/ijms21207594.

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In biology, the modern scientific fashion is to mostly study proteins. Much less attention is paid to lipids. However, lipids themselves are extremely important for the formation and functioning of cellular membrane organelles. Here, the role of the geometry of the lipid bilayer in regulation of organelle shape is analyzed. It is proposed that during rapid shape transition, the number of lipid heads and their size (i.e., due to the change in lipid head charge) inside lipid leaflets modulates the geometrical properties of organelles, in particular their membrane curvature. Insertion of proteins into a lipid bilayer and the shape of protein trans-membrane domains also affect the trans-membrane asymmetry between surface areas of luminal and cytosol leaflets of the membrane. In the cases where lipid molecules with a specific shape are not predominant, the shape of lipids (cylindrical, conical, or wedge-like) is less important for the regulation of membrane curvature, due to the flexibility of their acyl chains and their high ability to diffuse.

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MEREZHINSKAYA, Natasha, Gemma A. J. KUIJPERS e Yossef RAVIV. "Reversible penetration of α-glutathione S-transferase into biological membranes revealed by photosensitized labelling in situ". Biochemical Journal 335, n. 3 (1 novembre 1998): 597–604. http://dx.doi.org/10.1042/bj3350597.

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Fluorescent lipid analogue 3,3´-dioctadecyloxacarbocyanine incorporated into biological membranes was used to induce photoactivation of a hydrophobic probe 5-[125I]iodonaphthyl-1-azide (125INA) by energy transfer and to thereby confine subsequent radiolabelling of proteins to the lipid bilayer. This approach was applied in bovine chromaffin cells to discover cytosolic proteins that reversibly penetrate into membrane domains. α-Glutathione S-transferase (α-GST) was identified as the only labelled protein in bovine chromaffin-cell cytosol, indicating that it inserts reversibly into the membrane lipid bilayer. The selectivity of the labelling towards the lipid bilayer is demonstrated by showing that influenza virus haemagglutinin becomes labelled by 125INA only after the insertion of this protein into the target membrane. The molar 125INA:protein ratio was used as a quantitative criterion for evaluation of the penetration of proteins into the membrane lipid bilayer. This ratio was calculated for four integral membrane proteins and four soluble proteins that interact with biological membranes. The values for four integral membrane proteins (erythrocyte anion transporter, multidrug transporter gp-170, dopamine transporter and fusion-competent influenza virus haemagglutinin) were 1, 8, 2 and 2, respectively, whereas for soluble proteins (annexin VII, protein kinase C, BSA and influenza virus haemagglutinin) the values were 0.002, 0, 0.002 and 0.02, respectively. The molar ratio for α-GST was found to be 1, compatible with the values obtained for integral membrane proteins.

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Grage, Stephan L., Sergii Afonin, Marco Ieronimo, Marina Berditsch, Parvesh Wadhwani e Anne S. Ulrich. "Probing and Manipulating the Lateral Pressure Profile in Lipid Bilayers Using Membrane-Active Peptides—A Solid-State 19F NMR Study". International Journal of Molecular Sciences 23, n. 9 (20 aprile 2022): 4544. http://dx.doi.org/10.3390/ijms23094544.

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The lateral pressure profile constitutes an important physical property of lipid bilayers, influencing the binding, insertion, and function of membrane-active peptides, such as antimicrobial peptides. In this study, we demonstrate that the lateral pressure profile can be manipulated using the peptides residing in different regions of the bilayer. A 19F-labeled analogue of the amphiphilic peptide PGLa was used to probe the lateral pressure at different depths in the membrane. To evaluate the lateral pressure profile, we measured the orientation of this helical peptide with respect to the membrane using solid-state 19F-NMR, which is indicative of its degree of insertion into the bilayer. Using this experimental approach, we observed that the depth of insertion of the probe peptide changed in the presence of additional peptides and, furthermore, correlated with their location in the membrane. In this way, we obtained a tool to manipulate, as well as to probe, the lateral pressure profile in membranes.

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Ramachandran, Rajesh, Thomas J. Pucadyil, Ya-Wen Liu, Sharmistha Acharya, Marilyn Leonard, Vasyl Lukiyanchuk e Sandra L. Schmid. "Membrane Insertion of the Pleckstrin Homology Domain Variable Loop 1 Is Critical for Dynamin-catalyzed Vesicle Scission". Molecular Biology of the Cell 20, n. 22 (15 novembre 2009): 4630–39. http://dx.doi.org/10.1091/mbc.e09-08-0683.

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The GTPase dynamin catalyzes the scission of deeply invaginated clathrin-coated pits at the plasma membrane, but the mechanisms governing dynamin-mediated membrane fission remain poorly understood. Through mutagenesis, we have altered the hydrophobic nature of the membrane-inserting variable loop 1 (VL1) of the pleckstrin homology (PH) domain of dynamin-1 and demonstrate that its stable insertion into the lipid bilayer is critical for high membrane curvature generation and subsequent membrane fission. Dynamin PH domain mutants defective in curvature generation regain function when assayed on precurved membrane templates in vitro, but they remain defective in the scission of clathrin-coated pits in vivo. These results demonstrate that, in concert with dynamin self-assembly, PH domain membrane insertion is essential for fission and vesicle release in vitro and for clathrin-mediated endocytosis in vivo.

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Almarwani, Bashiyar, Yahia Z. Hamada, Nsoki Phambu e Anderson Sunda-Meya. "Investigating the Insertion Mechanism of Cell-Penetrating Peptide Penetratin into Cell Membranes: Implications for Targeted Drug Delivery". Biophysica 3, n. 4 (11 novembre 2023): 620–35. http://dx.doi.org/10.3390/biophysica3040042.

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The cell-penetrating peptide (CPP) penetratin (PEN) has garnered attention for its potential to enter tumor cells. However, its translocation mechanism and lack of selectivity remain debated. This study investigated PEN’s insertion into healthy cells (H-) and cancer cells (C-) using micromolar concentrations and various techniques. Raman spectroscopy was used to determine PEN’s location in the lipid bilayer at different lipid-to-peptide ratios. Dynamic light scattering (DLS) and zeta potential analysis were used to measure the lipid–PEN complex’s size and charge. The results showed helical PEN particles directly inserted into C- membranes at a ratio of 110, while aggregated particles stayed on H- surfaces. Raman spectroscopy and scanning electron microscopy confirmed PEN insertion in C- membranes. Zeta potential studies revealed highly negative charges for PEN–C- complexes and neutral charges for PEN–H- complexes at pH 6.8. C- integrity remained unchanged at a ratio of 110. Specific lipid-to-peptide ratios with dipalmitoylphosphatidylserine (DPPS) were crucial for direct insertion. These results provide valuable insights into CPP efficacy for targeted drug delivery in cancer cells, considering membrane composition and lipid-to-peptide ratios.

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Karabadzhak, Alexander, Dhammika Weerakkody, Donald M. Engelman, Oleg A. Andreev e Yana K. Reshetnyak. "Kinetics Of Peptide (pHLIP) Insertion And Folding In A Lipid Bilayer Membrane". Biophysical Journal 96, n. 3 (febbraio 2009): 453a. http://dx.doi.org/10.1016/j.bpj.2008.12.2327.

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Vivcharuk, Victor, e Yiannis Kaznessis. "Thermodynamic Analysis of Protegrin-1 insertion and Permeation through a Lipid Bilayer". Biophysical Journal 100, n. 3 (febbraio 2011): 498a. http://dx.doi.org/10.1016/j.bpj.2010.12.2916.

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Vivcharuk, Victor, e Yiannis N. Kaznessis. "Thermodynamic Analysis of Protegrin-1 Insertion and Permeation through a Lipid Bilayer". Journal of Physical Chemistry B 115, n. 49 (15 dicembre 2011): 14704–12. http://dx.doi.org/10.1021/jp205153y.

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Favero, G., A. D’Annibale, L. Campanella, R. Santucci e T. Ferri. "Membrane supported bilayer lipid membranes array: preparation, stability and ion-channel insertion". Analytica Chimica Acta 460, n. 1 (maggio 2002): 23–34. http://dx.doi.org/10.1016/s0003-2670(02)00139-3.

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35

Vasquez-Montes, Victor, Janessa Gerhart, Kelly E. King, Damien Thévenin e Alexey S. Ladokhin. "Comparison of lipid-dependent bilayer insertion of pHLIP and its P20G variant". Biochimica et Biophysica Acta (BBA) - Biomembranes 1860, n. 2 (febbraio 2018): 534–43. http://dx.doi.org/10.1016/j.bbamem.2017.11.006.

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Surrey, T., e F. Jahnig. "Refolding and oriented insertion of a membrane protein into a lipid bilayer." Proceedings of the National Academy of Sciences 89, n. 16 (15 agosto 1992): 7457–61. http://dx.doi.org/10.1073/pnas.89.16.7457.

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37

Baldwin, R. L., T. Mirzabekov, B. L. Kagan e B. J. Wisnieski. "Conformation and ion channel activity of lymphotoxin at neutral and low pH." Journal of Immunology 154, n. 2 (15 gennaio 1995): 790–98. http://dx.doi.org/10.4049/jimmunol.154.2.790.

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Abstract Lymphotoxin (LT or TNF-beta), a T cell-derived lymphokine with partial homology to TNF-alpha, was found to bind to dimyristoylphosphatidylcholine vesicles in a pH-dependent manner: binding increased with decreasing pH. Binding was not limited to surface association with phospholipid head groups because studies with a photoreactive membrane-restricted probe revealed protein penetration of the hydrocarbon core of the bilayer. Intramembranous photolabeling of the trimeric form of LT demonstrated maintenance of quaternary structure upon bilayer insertion. The efficiency of insertion was greatly enhanced with gel-phase bilayers compared with fluid phase bilayers even though the binding efficiency was much lower. Hence, binding and insertion represent two distinct physical processes. Intrinsic fluorescence and dye binding assays showed that the acid-facilitated membrane interactions stemmed from acid-induced changes in protein conformation. The acquisition of hydrophobic characteristics through these conformational changes supplies a physical explanation for LT conversion from a water-soluble form to a membrane-embedded structure. Moreover, the use of vesicle-embedded LT to prepare planar bilayers vs the addition of soluble LT subsequent to bilayer formation demonstrated that LT exhibits channel activity and that low pH-induced membrane insertion precedes and is distinct from expression of voltage-dependent ion gating. LT's ability to associate intimately with lipid vesicles and form ion channels mirrors the behavior of TNF-alpha. Thus, although LT and TNF-alpha are secreted by different cell types, the conservation of membrane binding, insertion, and channel-forming activities suggests a functional role in response induction.

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Gao, Yiyi, Dangxin Mao, Jun Wu, Xiaogang Wang, Zhikun Wang, Guoquan Zhou, Liang Chen, Junlang Chen e Songwei Zeng. "Carbon Nanotubes Translocation through a Lipid Membrane and Transporting Small Hydrophobic and Hydrophilic Molecules". Applied Sciences 9, n. 20 (12 ottobre 2019): 4271. http://dx.doi.org/10.3390/app9204271.

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Carbon nanotubes (CNTs) are extensively adopted in the applications of biotechnology and biomedicine. Their interactions with cell membranes are of great importance for understanding the toxicity of CNTs and the application of drug delivery. In this paper, we use atomic molecular dynamics simulations to study the permeation and orientation of pristine and functionalized CNTs in a lipid bilayer. Pristine CNT (PCNT) can readily permeate into the membrane and reside in the hydrophobic region without specific orientation. The insertion of PCNTs into the lipid bilayer is robust and independent on the lengths of PCNTs. Due to the presence of hydroxyl groups on both ends of the functionalized CNT (FCNT), FCNT prefers to stand upright in the lipid bilayer center. Compared with PCNT, FCNT is more suitable to be a bridge connecting the inner and outer lipid membrane. The inserted CNTs have no distinct effects on membrane structure. However, they may block the ion channels. In addition, preliminary explorations on the transport properties of CNTs show that the small hydrophobic molecule carbon dioxide can enter both PCNT and FCNT hollow channels. However, hydrophilic molecule urea is prone to penetrate the PCNT but finds it difficult to enter the FCNT. These results may provide new insights into the internalization of CNT in the lipid membrane and the transport properties of CNTs when embedded therein.

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Li, Zhenlong, e Alemayehu A. Gorfe. "Deformation of a two-domain lipid bilayer due to asymmetric insertion of lipid-modified Ras peptides". Soft Matter 9, n. 47 (2013): 11249. http://dx.doi.org/10.1039/c3sm51388b.

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Oñaderra, M., J. M. Mancheño, M. Gasset, J. Lacadena, G. Schiavo, A. Martínez del Pozo e J. G. Gavilanes. "Translocation of α-sarcin across the lipid bilayer of asolectin vesicles". Biochemical Journal 295, n. 1 (1 ottobre 1993): 221–25. http://dx.doi.org/10.1042/bj2950221.

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alpha-Sarcin is a cytotoxic protein produced by the mould Aspergillus giganteus. Insertion of alpha-sarcin into asolectin membranes has been demonstrated by protein labelling with photoreactive phospholipids. alpha-Sarcin added externally to tRNA-containing asolectin liposomes degrades the entrapped tRNA. Trypsin-containing asolectin liposomes were also prepared. Encapsulated trypsin degrades alpha-sarcin, even in the presence of a large excess of external hen egg-white trypsin inhibitor to prevent any alpha-sarin degradation outside the vesicles. These processes occur only with acidic phospholipids and were not observed when phosphatidylcholine vesicles were used. These results indicate that alpha-sarcin penetrates the lipid bilayer and becomes exposed to the lumen of negatively charged liposomes.

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Renner, Stephan, Andrey Bessonov e Friedrich C. Simmel. "Voltage-controlled insertion of single α-hemolysin andMycobacterium smegmatisnanopores into lipid bilayer membranes". Applied Physics Letters 98, n. 8 (21 febbraio 2011): 083701. http://dx.doi.org/10.1063/1.3558902.

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Sharma, Bineet, Hossein Moghimianavval, Sung-Won Hwang e Allen P. Liu. "Synthetic Cell as a Platform for Understanding Membrane-Membrane Interactions". Membranes 11, n. 12 (23 novembre 2021): 912. http://dx.doi.org/10.3390/membranes11120912.

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In the pursuit of understanding life, model membranes made of phospholipids were envisaged decades ago as a platform for the bottom-up study of biological processes. Micron-sized lipid vesicles have gained great acceptance as their bilayer membrane resembles the natural cell membrane. Important biological events involving membranes, such as membrane protein insertion, membrane fusion, and intercellular communication, will be highlighted in this review with recent research updates. We will first review different lipid bilayer platforms used for incorporation of integral membrane proteins and challenges associated with their functional reconstitution. We next discuss different methods for reconstitution of membrane fusion and compare their fusion efficiency. Lastly, we will highlight the importance and challenges of intercellular communication between synthetic cells and synthetic cells-to-natural cells. We will summarize the review by highlighting the challenges and opportunities associated with studying membrane–membrane interactions and possible future research directions.

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Greig, Sarah L., Mazdak Radjainia e Alok K. Mitra. "Oligomeric Structure of Colicin Ia Channel in Lipid Bilayer Membranes". Journal of Biological Chemistry 284, n. 24 (8 aprile 2009): 16126–34. http://dx.doi.org/10.1074/jbc.m900292200.

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Colicin Ia is a soluble, harpoon-shaped bacteriocin which translocates across the periplasmic space of sensitive Escherichia coli cell by parasitizing an outer membrane receptor and forms voltage-gated ion channels in the inner membrane. This process leads to cell death, which has been thought to be caused by a single colicin Ia molecule. To directly visualize the three-dimensional structure of the channel, we generated two-dimensional crystals of colicin Ia inserted in lipid-bilayer membranes and determined a ∼17 three-dimensional model by electron crystallography. Supported by velocity sedimentation, chemical cross-linking and single-particle image analysis, the three-dimensional structure is a crown-shaped oligomer enclosing a ∼35 Å-wide extrabilayer vestibule. Our study suggests that lipid insertion instigates a global conformational change in colicin Ia and that more than one molecule participates in the channel architecture with the vestibule, possibly facilitating the known large scale peptide translocation upon channel opening.

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Monnier, Noadya, Aurélien Furlan, Sébastien Buchoux, Magali Deleu, Manuel Dauchez, Sonia Rippa e Catherine Sarazin. "Exploring the Dual Interaction of Natural Rhamnolipids with Plant and Fungal Biomimetic Plasma Membranes through Biophysical Studies". International Journal of Molecular Sciences 20, n. 5 (26 febbraio 2019): 1009. http://dx.doi.org/10.3390/ijms20051009.

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Rhamnolipids (RLs) are potential biocontrol agents for crop culture protection. Their mode of action has been proposed as dual, combining plant protection activation and antifungal activities. The present work focuses on the interaction of natural RLs with plant and fungi membrane models at the molecular scale. Representative models were constructed and the interaction with RLs was studied by Fourier transform infrared (FTIR) and deuterium nuclear magnetic resonance (2H NMR) spectroscopic measurements. Molecular dynamic (MD) simulations were performed to investigate RL insertion in lipid bilayers. Our results showed that the RLs fit into the membrane models and were located near the lipid phosphate group of the phospholipid bilayers, nearby phospholipid glycerol backbones. The results obtained with plant plasma membrane models suggest that the insertion of RLs inside the lipid bilayer did not significantly affect lipid dynamics. Oppositely, a clear fluidity increase of fungi membrane models was observed. This effect was related to the presence and the specific structure of ergosterol. The nature of the phytosterols could also influence the RL effect on plant plasma membrane destabilization. Subtle changes in lipid dynamics could then be linked with plant defense induction and the more drastic effects associated with fungal membrane destabilization.

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Hills, Jr, Ronald D. "Refining amino acid hydrophobicity for dynamics simulation of membrane proteins". PeerJ 6 (10 gennaio 2018): e4230. http://dx.doi.org/10.7717/peerj.4230.

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Coarse-grained (CG) models have been successful in simulating the chemical properties of lipid bilayers, but accurate treatment of membrane proteins and lipid-protein molecular interactions remains a challenge. The CgProt force field, original developed with the multiscale coarse graining method, is assessed by comparing the potentials of mean force for sidechain insertion in a DOPC bilayer to results reported for atomistic molecular dynamics simulations. Reassignment of select CG sidechain sites from the apolar to polar site type was found to improve the attractive interfacial behavior of tyrosine, phenylalanine and asparagine as well as charged lysine and arginine residues. The solvation energy at membrane depths of 0, 1.3 and 1.7 nm correlates with experimental partition coefficients in aqueous mixtures of cyclohexane, octanol and POPC, respectively, for sidechain analogs and Wimley-White peptides. These experimental values serve as important anchor points in choosing between alternate CG models based on their observed permeation profiles, particularly for Arg, Lys and Gln residues where the all-atom OPLS solvation energy does not agree well with experiment. Available partitioning data was also used to reparameterize the representation of the peptide backbone, which needed to be made less attractive for the bilayer hydrophobic core region. The newly developed force field, CgProt 2.4, correctly predicts the global energy minimum in the potentials of mean force for insertion of the uncharged membrane-associated peptides LS3 and WALP23. CgProt will find application in studies of lipid-protein interactions and the conformational properties of diverse membrane protein systems.

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Shin, I., D. Kreimer, I. Silman e L. Weiner. "Membrane-promoted unfolding of acetylcholinesterase: A possible mechanism for insertion into the lipid bilayer". Proceedings of the National Academy of Sciences 94, n. 7 (1 aprile 1997): 2848–52. http://dx.doi.org/10.1073/pnas.94.7.2848.

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Hwang, Hyonseok, George C. Schatz e Mark A. Ratner. "Coarse-Grained Molecular Dynamics Study of Cyclic Peptide Nanotube Insertion into a Lipid Bilayer†". Journal of Physical Chemistry A 113, n. 16 (23 aprile 2009): 4780–87. http://dx.doi.org/10.1021/jp8080657.

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Angelique, Coutable, Vincent Noireaux, Bruno Lepioufle, Olivier Français, Christophe Vieu, Jean-Marie François, Christophe Thibault e Emmanuelle Trevisiol. "Insertion of Functional Proteins into Bilayer Lipid Membrane using a Cell-Free Expression System". Biophysical Journal 104, n. 2 (gennaio 2013): 548a. http://dx.doi.org/10.1016/j.bpj.2012.11.3039.

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Pirri, Giovanna, Andrea Giuliani, Silvia Nicoletto, Lorena Pizzuto e Andrea Rinaldi. "Lipopeptides as anti-infectives: a practical perspective". Open Life Sciences 4, n. 3 (1 settembre 2009): 258–73. http://dx.doi.org/10.2478/s11535-009-0031-3.

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AbstractLipopeptide antibiotics represent an old class of antibiotics that were discovered over 50 years ago, which includes the old polymyxins but also new entries, such as the recently approved daptomycin. They generally consist of a hydrophilic cyclic peptide portion attached to a fatty acid chain which facilitates insertion into the lipid bilayer of bacterial membranes. This review presents an overview of this class of antibiotics, focusing on their therapeutic applications and putting particular emphasis on chemical modifications introduced to improve their activity.

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Leznicki, Pawel, Jim Warwicker e Stephen High. "A biochemical analysis of the constraints of tail-anchored protein biogenesis". Biochemical Journal 436, n. 3 (27 maggio 2011): 719–27. http://dx.doi.org/10.1042/bj20101737.

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TA (tail-anchored) proteins utilize distinct biosynthetic pathways, including TRC40 (transmembrane domain recognition complex of 40 kDa)-mediated, chaperone-dependent and/or unassisted routes to the ER (endoplasmic reticulum) membrane. We have addressed the flexibility of cytosolic components participating in these pathways, and explored the thermodynamic constraints of their membrane insertion, by exploiting recombinant forms of Sec61β and Cytb5 (cytochrome b5) bearing covalent modifications within their TA region. In both cases, efficient membrane insertion relied on cytosolic factors capable of accommodating a surprising range of covalent modifications to the TA region. For Sec61β, we found that both SGTA (small glutamine-rich tetratricopeptide repeat-containing protein α) and TRC40 can bind this substrate with a singly PEGylated TA region. However, by introducing two PEG [poly(ethylene glycol)] moieties, TRC40 binding can be prevented, resulting in a block of subsequent membrane integration. Although TRC40 can bind Sec61β polypeptides singly PEGylated at different locations, membrane insertion is more sensitive to the precise location of PEG attachment. Modelling and experimentation indicate that this post-TRC40 effect results from an increased energetic cost of inserting different PEGylated TA regions into the lipid bilayer. We therefore propose that the membrane integration of TA proteins delivered via TRC40 is strongly dependent upon underlying thermodynamics, and speculate that their insertion is via a phospholipid-mediated process.

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