Check out our New Publishers' Select for Free Articles

BBA - Biomembranes (v.1669, #2)

Editorial Board (pp. ii).

Environmental factors that enhance the action of the cell penetrating peptide pep-1 by S�nia Troeira Henriques; Miguel A.R.B. Castanho (pp. 75-86).

Pep-1 is a cell penetrating peptide (CPP) derived from the nuclear localization sequence of Simian Virus 40 large antigen T and from reverse transcriptase of Human Immunodeficiency Virus. Although it has been successfully used to transport proteins into cells, its action at the molecular level is not yet clear, mainly the local environmental factors that condition partition and translocation. Characterization in aqueous medium and quantification of partition into bilayers were carried out. Dynamic light scattering studies show that pep-1 self-associates in aqueous medium. The role of the bilayer phase, anionic lipids, ionic strength of the medium, reducing agents and pep-1 concentration on the extent and kinetics of partition were studied. Unlike others cationic CPP (e.g. penetratin) pep-1 has a high affinity to neutral vesicles ( K_p=2.8�10³), which is enhanced by anionic lipids. In a reduction environment partition is strongly inhibited ( K_p=2.2�10²), which might be a key-feature in the biological action of pep-1. Peptide incorporation takes place in the millisecond time-range to the lipidic interfaces. These environmental factors are systematized to enlighten how they help cellular uptake.

Keywords: Translocation; Vector; Peptide carrier; Fluorescence; Vesicle

Protein mediated glycolipid transfer is inhibited FROM sphingomyelin membranes but enhanced TO sphingomyelin containing raft like membranes by Matts Nylund; Peter Mattjus (pp. 87-94).

The mammalian glycolipid transfer protein, GLTP, catalyzes the transfer in vitro of glycolipids between membranes. In this study we have examined on one hand the effect of the variations in the donor vesicle composition and on the other hand the effects of variations in the acceptor vesicle composition on the GLTP-catalyzed transfer kinetics of galactosylceramide between bilayer vesicles. For this purpose a resonance energy transfer assay was used, the energy donor being anthrylvinyl-galactosylceramide and the energy acceptor DiO-C₁₆. First, we show that the transfer of anthrylvinyl-galactosylceramide from palmitoyl-oleoyl-phosphatidylcholine donor vesicles was faster than from dipalmitoyl-phosphatidylcholine vesicles, and that there is no transfer from palmitoyl-sphingomyelin vesicles regardless of the cholesterol amount. In this setup the acceptor vesicles were always 100% palmitoyl-oleoyl-phosphatidylcholine. We also showed that the transfer in general is faster from small highly curved vesicles compared to that from larger vesicles. Secondly, by varying the acceptor vesicle composition we showed that the transfer is faster to mixtures of sphingomyelin and cholesterol compared to mixtures of phosphatidylcholines and cholesterol. Based on these experiments we conclude that the GLTP mediated transfer of anthrylvinyl-galactosylceramide is sensitive to the matrix lipid composition and membrane bending. We postulate that a tightly packed membrane environment is most effective in preventing GLTP from accessing its substrates, and cholesterol is not required to protect the glycosphingolipid in the membrane from being transferred by GLTP. On the other hand GLTP can more easily transfer glycolipids to ‘lipid raft’ like membranes, suggesting that the protein could be involved in raft assembly.

Keywords: Abbreviations; RET; resonance energy transfer; SUV; small unilamellar vesicle; GLTP; glycolipid transfer protein; GSL; glycosphingolipid; GalCer; galactosylceramide; SPM; sphingomyelin; PC; phosphatidylcholine; AV-GalCer; N; -[(11; E; )-12-(9-anthryl)-11-dodecenoyl]-1-O-β-galactosylsphingosine; DiO-C; ₁₆; 3,3′-dihexadecyloxacarbocyanine perchlorate; POPC; 1-hexadecanoyl-2-[; cis; -9-octadecenoyl]-; sn; -glycero-3-phosphocholine; DPPC; 1,2-di-hexadecanoyl-; sn; -glycero-3-phosphocholine; P-SPM; (2S,3R,4E)-2-palmitoylaminooctadec-4-ene-3-hydroxy-1-phosphocholineSphingomyelin; Phosphatidylcholine; Fluorescence; Glycosphingolipids; Glycolipid transfer protein; Cholesterol; Lipid rafts

The role of cysteine residues in the sulphate transporter, SHST1: Construction of a functional cysteine-less transporter by Susan M. Howitt (pp. 95-100).

We investigated the role of cysteine residues in the sulphate transporter, SHST1, with the aim of generating a functional cysteine-less variant. SHST1 contains five cysteine residues and none was essential for function. However, replacement of C421 resulted in a reduction in transport activity. Sulphate transport by C205 mutants was dependent on the size of the residue at this position. Alanine at position 205 resulted in a complete loss of function whereas leucine resulted in a 3-fold increase in sulphate transport relative to wild type SHST1. C205 is located in a putative intracellular loop and our results suggest that this loop may be important for sulphate transport. By replacing C205 with leucine and the other four cysteine residues with alanine, we constructed a cysteine-less variant of SHST1 that has transport characteristics indistinguishable from wild type. This construct will be useful for further structure and function studies of SHST1.

Keywords: Sulphate transporter; Site-directed mutagenesis; Cysteine; Diastrophic dysplasia; Pendred syndrome; Congenital chloride diarrhoea

Internalisation of cell-penetrating peptides into tobacco protoplasts by Maarja M�e; Helena Myrberg; Yang Jiang; Heiti Paves; Andres Valkna; �lo Langel (pp. 101-107).

Cells are protected from the surrounding environment by plasma membrane which is impenetrable for most hydrophilic molecules. In the last 10 years cell-penetrating peptides (CPPs) have been discovered and developed. CPPs enter mammalian cells and carry cargo molecules over the plasma membrane with a molecular weight several times their own. Known transformation methods for plant cells have relatively low efficiency and require improvement. The possibility to use CPPs as potential delivery vectors for internalisation in plant cells has been studied in the present work. We analyse and compare the uptake of the fluorescein-labeled CPPs, transportan, TP10, penetratin and pVEC in Bowes human melanoma cells and Nicotiana tabacum cultivar (cv.) SR-1 protoplasts (plant cells without cell wall). We study the internalisation efficiency of CPPs with fluorescence microscopy, spectrofluorometry and fluorescence-activated cell sorter (FACS). All methods indicate, for the first time, that these CPPs can internalise into N. tabacum cv. SR-1 protoplasts. Transportan has the highest uptake efficacy among the studied peptides, both in mammalian cells and plant protoplast. The internalisation of CPPs by plant protoplasts may open up a new effective method for transfection in plants.

Keywords: Abbreviations; CPP; cell-penetrating peptide; cv; cultivar; EDTA; ethylenediaminetetraacetate; FACS; fluorescence-activated cell sorter; FITC; fluorescein isothiocyanate; Fl; fluoresceinyl; HEPES; N; -(2-Hydroxyethyl)piperazine-; N′; -(2-ethanesulfonic acid); HKR; HEPES-buffered Krebs-Ringer solution; RP-HPLC; reversed phase high performance liquid chromatography; RT; room temperature; t; -Boc; tert; -butyloxycarbonyl; TFA; trifluoroacetic acid; TP10; transportan 10Cell-penetrating peptide; Plant protoplast; Membrane penetration; Transportan; TP10; Penetratin; p; VEC

Ras couples phosphoinositide 3-OH kinase to the epithelial Na⁺ channel by Alexander Staruschenko; Oleh M. Pochynyuk; Qiusheng Tong; James D. Stockand (pp. 108-115).

Aldosterone induces the expression of the small G protein K-Ras. Both K-Ras and its 1st effector phosphoinositide 3-OH kinase (PI3-K) are necessary and sufficient for the activation of ENaC increasing channel open probability. The cell signaling mechanism by which K-Ras enhances ENaC activity, however, is uncertain. We demonstrate here that K-Ras significantly activates human ENaC reconstituted in Chinese hamster ovary cells ∼3-fold. Activation in response to K-Ras was sensitive to the irreversible PI3-K inhibitor wortmannin but not the competitive LY294002 inhibitor of this phospholipid kinase. Similarly, a PI3-K 1st effector-specific Ras mutant (G12:C40) enhanced ENaC activity in a wortmannin but not LY294002 sensitive manner. Constitutively active PI3-K also enhanced ENaC activity but in a wortmannin and LY294002 sensitive manner with the effects of PI3-K and K-Ras not being additive. The activation of ENaC by PI3-K was also sensitive to intracellular GDPβS. Constitutively active PI3-K that is incapable of interacting with K-Ras (K227E p110α) acted as dominant negative with respect to the regulation of ENaC even in the presence of K-Ras. K-Ras is known to directly interact with PI3-K with aldosterone promoting this interaction. Here we demonstrate that K-Ras also interacts with ENaC through an, as yet, undetermined mechanism. We conclude that K-Ras enhances ENaC activity by localizing PI3-K near the channel and stimulating of PI3-K activity.

Keywords: K-Ras; Phosphoinositide 3-OH kinase; ENaC activation

Precision parameters from spin-probe studies of membranes using a partitioning technique. Application to two model membrane vesicles by Miroslav Peric; Marilene Alves; Barney L. Bales (pp. 116-124).

A new version of the ESR spin probe partitioning method is developed and applied to the study of hydration properties of dimyristoyl-phosphatidylglycerol (DMPG) and dimyristoyl-phosphatidylcholine (DMPC) vesicles as functions of salt concentration and temperature above the lipid phase transition. The small spin probe di- tert-butyl nitroxide (DTBN) is used in order to achieve motionally narrowed Electron Spin Resonance (ESR) spectra which may be analyzed with high precision. The new method relies on the use of the second harmonic display of the ESR spectrum followed by spectral line fitting. Spectral fitting yields precise ESR parameters giving detailed information on the surroundings of the spin probe in both phospholipid and aqueous phases. The nitrogen hyperfine coupling constant of DTBN arising from those probes occupying the vesicles is used to study the hydration of the vesicle surface. The hydration properties of the negatively charged vesicle surface of DMPG vesicles are affected by the addition of salt at all temperatures. In contrast, the hydration of DMPC vesicles does not change with salt concentration at the low temperatures. However, at higher temperatures the hydration properties of DMPC vesicle are affected by salt which is interpreted to be due to the faster motion of the phospholipid molecules. The partitioning of the spin probe increases with salt concentration for both DMPG and DMPC vesicles, while water penetration decreases simultaneously. The spin probe in the phospholipid bilayer exhibits anisotropic motion and the extent of the anisotropy is increased at the higher salt concentrations.

Keywords: Electron Spin Resonance spectroscopy; Membrane hydration; Dimyristoyl-phosphatidylglycerol vesicle; Dimyristoyl-phosphatidylcholine vesicle; Spin probe; Spectral line fitting

Structural rearrangement of model membranes by the peptide antibiotic NK-2 by Regine Willumeit; Mont Kumpugdee; S�rgio S. Funari; Karl Lohner; Beatriz Pozo Navas; Klaus Brandenburg; Sebastian Linser; J�rg Andr� (pp. 125-134).

We have developed a novel α-helical peptide antibiotic termed NK-2. It efficiently kills bacteria, but not human cells, by membrane destruction. This selectivity could be attributed to the different membrane lipid compositions of the target cells. To understand the mechanisms of selectivity and membrane destruction, we investigated the influence of NK-2 on the supramolecular aggregate structure, the phase transition behavior, the acyl chain fluidity, and the surface charges of phospholipids representative for the bacterial and the human cell cytoplasmic membranes. The cationic NK-2 binds to anionic phosphatidylglycerol liposomes, causing a thinning of the membrane and an increase in the phase transition temperature. However, this interaction is not solely of electrostatic but also of hydrophobic nature, indicated by an overcompensation of the Zeta potential. Whereas NK-2 has no effect on phosphatidylcholine liposomes, it enhances the fluidity of phosphatidylethanolamine acyl chains and lowers the phase transition enthalpy of the gel to liquid cristalline transition. The most dramatic effect, however, was observed for the lamellar/inverted hexagonal transition of phosphatidylethanolamine which was reduced by more than 10 °C. Thus, NK-2 promotes a negative membrane curvature which can lead to the collapse of the phosphatidylethanolamine-rich bacterial cytoplasmic membrane.

Keywords: Abbreviations; DSC; differential scanning calorimetry; FTIR; Fourier-transform infrared spectroscopy; SAXS; small-angle X-ray scattering; POPE; 1-palmitoyl-2-oleoyl-; sn; -glycero-3-phosphoethanolamine; POPG; 1-palmitoyl-2-oleoyl-; sn; -glycero-3-[phospho-rac-(1-glycerol)] (sodium salt); POPC; 1-palmitoyl-2-oleoyl-; sn; -glycero-3-phosphocholine; DMPC; 1,2-dimyristoyl-; sn; -glycero-3-phosphocholine; DMPG; 1,2-dimyristoyl-; sn; -glycero-3-[phospho-rac-(1-glycerol)] (sodium salt); DPPC; 1,2-dipalmitoyl-; sn; -glycero-3-phosphocholine; DPPE; 1,2-dipalmitoyl-; sn; -glycero-3-phosphoethanolamine; DPPG; 1,2-dipalmitoyl-; sn; -glycero-3-phosphoglycerolAntimicrobial peptide; Membrane curvature; NK-lysin; Phosphatidylethanolamine; Small-angle X-ray diffraction

High zinc sensitivity and pore formation in an invertebrate P2X receptor by Ramin Raouf; Dominique Blais; Philippe S�gu�la (pp. 135-141).

To investigate fast purinergic signaling in invertebrates, we examined the functional properties of a P2X receptor subunit cloned from the parasitic platyhelminth Schistosoma mansoni. This purinoceptor (SmP2X) displays unambiguous homology of primary sequence with vertebrate P2X subunits. SmP2X subunits assemble into homomeric ATP-gated channels that exhibit slow activation kinetics and are blocked by suramin and PPADS but not TNP-ATP. SmP2X mediates the uptake of the dye YO-PRO-1 through the formation of large pores and can be blocked by submicromolar concentrations of extracellular Zn²⁺ ions (IC₅₀=0.4 μM). The unique receptor phenotype defined by SmP2X suggests that slow kinetics, modulation by zinc and the ability to form large pores are ancestral properties of P2X receptors. The high sensitivity of SmP2X to zinc further reveals a zinc regulation requirement for the parasite's physiology that could potentially be exploited for therapeutic purposes.

Keywords: Abbreviations; BzATP; 2′-3′-; O; -(4-benzoylbenzoyl) ATP; αβmATP; α,β-methyleneATPPurinoceptor; ATP; Cation channel; Ionotropic; Schistosoma; Xenopus; oocytes

Nectin-like molecule 1 is a protein 4.1N associated protein and recruits protein 4.1N from cytoplasm to the plasma membrane by Yan Zhou; Guangwei Du; Xiaoyan Hu; Shun Yu; Yaobo Liu; Yaqin Xu; Xiaowei Huang; Jin Liu; Bin Yin; Ming Fan; Xiaozhong Peng; Boqin Qiang; Jiangang Yuan (pp. 142-154).

Nectins are immunoglobulin superfamily adhesion molecules that participate in the organization of epithelial and endothelial junctions. Sharing high homology with the poliovirus receptor (PVR/CD155), nectins were also named poliovirus receptor-related proteins (PRRs). Four nectins and five nectin-like molecules have been identified. Here we describe the cloning and characterization of human and mouse nectin-like molecular 1 (NECL1). Human and mouse NECL1 share 87.3% identity at the amino acid level. NECL1 contains an ectodomain made of three immunoglobulin-like domains, and a cytoplasmic region homologous to those of glycophorin C and contactin-associated protein. RNA blot and in situ hybridization analysis showed that NECL1 predominantly expressed in the central nervous system, mainly in neuronal cell bodies in a variety of brain regions including the cerebellum, cerebral cortex and hippocampus. In vitro binding assay proved the association of NECL1 with protein 4.1N. NECL1 localizes to the cell–cell junctions and recruits protein 4.1N to the plasma membranes through its C-terminus, thus may regulate the function of the cell–cell junction. We propose that the NECL1 and protein 4.1N complex is involved in the morphological development, stability, and dynamic plasticity of the nervous system.

Keywords: Nectin; NECL1; Protein 4.1N

Stabilized plasmid–lipid particles containing PEG-diacylglycerols exhibit extended circulation lifetimes and tumor selective gene expression by E. Ambegia; S. Ansell; P. Cullis; J. Heyes; L. Palmer; I. MacLachlan (pp. 155-163).

Stabilized plasmid lipid particles (SPLP) consist of a single copy of DNA surrounded by a lipid bilayer. The particles are small (∼100 nm), stable, monodisperse and have a low surface charge. A diffusible polyethylene glycol (PEG) coating attached to a lipid anchor is critical to the SPLP's functionality. The PEG–lipid exchanges out of the bilayer at a rate determined by the size of the lipid anchor. Here we show that SPLP can be prepared using a series of PEG–diacylglycerol lipids (PEG–S-DAGs). SPLP were prepared incorporating PEG–dimyristoylglycerol (C₁₄), PEG–dipalmitoylglycerol (C₁₆) or PEG–distearoylglycerol (C₁₈) and the rate of PEG–lipid diffusion from the bi-layer determined using a FRET assay. SPLP pharmacokinetics confirm a correlation between the stability of the PEG–lipid component and circulation lifetime. PEG–S-DAGs with longer lipid anchors yield more stable SPLP particles with longer circulation half-lives yielding an increase in tumor delivery and gene expression. PEG–distearoylglycerol (C₁₈) containing SPLP bypass so-called ‘first pass’ organs, including the lung, and elicit levels of gene expression in distal tumor tissue 100- to 1000-fold greater than that observed in any other tissue. The incorporation of PEG–S-DAG in SPLP confirms that small size, low surface charge and extended circulation lifetimes are prerequisite to the accumulation and tumor selective expression of plasmid DNA following systemic administration.

Keywords: Gene therapy; Stabilized plasmid–lipid particle; Systemic drug delivery; Poly(ethylene glycol)–lipid conjugate; Lipid exchange

Changes in the morphology of cell-size liposomes in the presence of cholesterol: Formation of neuron-like tubes and liposome networks by Shin-ichiro M. Nomura; Yumi Mizutani; Kimio Kurita; Akihiko Watanabe; Kazunari Akiyoshi (pp. 164-169).

Spontaneous changes in the morphology of cell-size liposomes (dioleoylphosphatidylcholine, DOPC and egg PC) as model cells were investigated in the presence of cholesterol. Tube structures and liposome networks connected by the tubes were observed in the presence of 5–30% cholesterol by dark-field and laser-scanning microscopy. Furthermore, in the presence of more than 40 mol% of cholesterol, the tubes disappeared and changed to small liposomes. Thus, cholesterol induced a morphological change in giant liposomes from tubes to small liposomes. These phenomena may be related to the role of cholesterol in the morphological changes in living cells such as neurons.

Keywords: Giant liposome; Cholesterol; Lipid bilayer; Tubular network; Neuron

Phospholipid diversity: Correlation with membrane–membrane fusion events by F. Deeba; H. Nasti Tahseen; K. Sharma Sharad; N. Ahmad; S. Akhtar; M. Saleemuddin; O. Mohammad (pp. 170-181).

The transport of various metabolically important substances along the endocytic and secretory pathways involves budding as well as fusion of vesicles with various intracellular compartments and plasma membrane. The membrane–membrane fusion events between various sub-compartments of the cell are believed to be mainly mediated by so-called “fusion proteins�?. This study shows that beside the proteins, lipid components of membrane may play an equally important role in fusion and budding processes. Inside out (ISO) as well as right side out (RSO) erythrocyte vesicles were evaluated for their fusogenic potential using conventional membrane fusion assay methods. Both fluorescence dequenching as well as content mixing assays revealed fusogenic potential of the erythrocyte vesicles. Among two types of vesicles, ISO were found to be more fusogenic as compared to the RSO vesicles. Interestingly, ISO retained nearly half of their fusogenic properties after removal of the proteins, suggesting the remarkable role of lipids in the fusion process. In another set of experiments, fusogenic properties of the liposomes (subtilosome), prepared from phospholipids isolated from Bacillus subtilis (a lower microbe) were compared with those of erythrocyte vesicles. We have also demonstrated that various types of vesicles upon interaction with macrophages deliver encapsulated materials to the cytosol of the cells. Membrane–membrane fusion was also followed by the study, in which a protein synthesis inhibitor ricin A (that does not cross plasma membrane), when encapsulated in the erythrocyte vesicles or subtilosomes was demonstrated to gain access to the cytosol.

Keywords: Abbreviations; ISO; Inside out vesicles; RSO; Right side out vesicles; LUV; Large unilamellar vesicles; EL; Erythrocyte lipids; OVA; Ovalbumin; PC; Phosphatidylcholine; PS; Phosphatidylserine; PE; Phosphatidylethanolamine; R18; Octadecylrhodamine B-chloride; NBD–PE; l; -(Phosphatidylethanolamine–; N; -(4-nitrobenzo-2-oxa-1,3-diazole); Rh–PE; N; -(Lissamine rhodamine B sulfonyl)phosphatidylethanolamine; ANTS; l; -Aminonapthalene-3,6,8-trisulfonic acid; DPX; N; ,; N; '-; p; -Xylylenebis (pyridinium bromide); DMEM; Dulbecco's modified Eagle medium; HBSS; Hanks balanced salt solution; FCS; Fetal calf serum; CTL; Cytotoxic T lymphocyteSubtilosomes; Inside out vesicles; Fusion; Membranes

Agonist-induced up-regulation of human somatostatin receptor type 1 is regulated by β-arrestin-1 and requires an essential serine residue in the receptor C-tail by Jos� L. Ram�rez; Heather L. Watt; Magalie Rocheville; Ujendra Kumar (pp. 182-192).

We have previously shown that the human somatostatin receptor type 1 (hSSTR1) does not undergo agonist-induced internalization, but is instead up-regulated at the membrane upon prolonged somatostatin (SST) exposure. The deletion of the carboxyterminal C-tail of the receptor completely abolishes up-regulation. To identify molecular signals that mediate hSSTR1 up-regulation, we created mutant receptors with progressive C-tail deletions. Up-regulation was found to be absent in mutants lacking residues Lys³⁵⁹-Ser³⁶⁰-Arg³⁶¹. Moreover, point mutation of Ser³⁶⁰ to Ala completely abolished up-regulation. The coexpression of wild type hSSTR1 with V53D, a dominant negative mutant of β-arrestin-1, completely blocked hSSTR1 up-regulation. Further analysis demonstrated that calcium-calmodulin (CaM) dependent kinases were essential for the SST-induced up-regulation response. Like wild type receptors, all mutants failed to internalize after agonist exposure and were able to inhibit forskolin-stimulated cAMP accumulation. Taking these data together, we suggest that SST-induced hSSTR1 up-regulation is critically dependent upon a specific Lys-Ser-Arg sequence in the C-tail of the receptor, with Ser³⁶⁰ being essential. Up-regulation also requires the participation of CaM protein kinases and interactions with β-arrestins. In contrast, coupling to adenyl cyclase (AC) and internalization occur independently of molecular signals in the receptor's C-tail.

Keywords: Abbreviations; AC; adenylyl cyclase; CaM; calcium calmodulin; CHO-KI; Chinese hamster ovary cell line; FBS; fetal bovine serum; GPCR; G protein-coupled receptor; GRK; GPCR kinase; hSSTR; human somatostatin receptor; MAPK; mitogen activated protein kinase; PKA; protein kinase A; PTX; pertussis toxin; PLC; phospholipase C; PCR; polymerase chain reaction; SST; somatostatin; SSTR; somatostatin receptorhSSTR1; Somatostatin; Up-regulation; Sequence motif; β-Arrestin; Kinase

New effects in polynucleotide release from cationic lipid carriers revealed by confocal imaging, fluorescence cross-correlation spectroscopy and single particle tracking by Svitlana Berezhna; Stephan Schaefer; Rainer Heintzmann; Michael Jahnz; Guido Boese; Ashok Deniz; Petra Schwille (pp. 193-207).

We report on new insights into the mechanisms of short single and double stranded oligonucleotide release from cationic lipid complexes (lipoplexes), used in gene therapy. Specifically, we modeled endosomal membranes using giant unilamellar vesicles and investigated the roles of various individual cellular phospholipids in interaction with lipoplexes. Our approach uses a combination of confocal imaging, fluorescence cross-correlation spectroscopy and single particle tracking, revealing several new aspects of the release: (a) phosphatidylserine and phosphatidylethanolamine are equally active in disassembling lipoplexes, while phosphatidylcholine and sphingomyelin are inert; (b) in contrast to earlier findings, phosphatidylethanolamine alone, in the absence of anionic phosphatidylserine triggers extensive release; (c) a double-stranded DNA structure remains well preserved after release; (d) lipoplexes exhibited preferential binding to transient lipid domains, which appear at the onset of lipoplex attachment to originally uniform membranes and vanish after initiation of polynucleotide release. The latter effect is likely related to phosphatidyleserine redistribution in membranes due to lipoplex binding. Real time tracking of single DOTAP/DOPE and DOTAP/DOPC lipoplexes showed that both particles remained compact and associated with membranes up to 1–2 min before fusion, indicating that a more complex mechanism, different from suggested earlier rapid fusion, promotes more efficient transfection by DOTAP/DOPE complexes.

Keywords: Abbreviations; GUVs; giant unilamellar vesicles; PS; phosphatidylserine; PE; phosphatidylethanolamine; PC; phosphatidylcholine; SM; sphingomyelin; DOTAP; dioleoyltrimethylammonium propane; DOPE; di-oleoyl phosphatidylethanolamine; DOPC; di-oleoyl phosphatidylcholine; DPPS; di-palmitoyl phosphatidylserine; DOPS; 1,2-dioleoyl-; s; n-glycero-3-phospho-L-serine; DiO; 3,3′-dihexadecyloxacarbocyanine perchlorate (DiOC; ₁₆; (3)); ITO; indium tin oxide; HPLC; high performance liquid chromatography; LSM; laser scanning confocal fluorescence microscopy; FCCS; fluorescence cross-correlation spectroscopy; SPT; single particle tracking; PCR; polymerase chain reactionLipoplex; Endosomal membrane; Release mechanism; Giant unilamellar vesicles; Fluorescence microscopy; Single particle tracking

Cumulative Contents (pp. 209-210).

Sections

Personal tools

BBA - Biomembranes (v.1669, #2)

Sections

Personal tools

Local resources

BBA - Biomembranes (v.1669, #2)