Acyl Chain Disorder and Azelaoyl Orientation in Lipid Membranes Containing Oxidized Lipids.

Oxidized phospholipids occur naturally in conditions of oxidative stress and have been suggested to play an important role in a number of pathological conditions due to their effects on a lipid membrane acyl chain orientation, ordering, and permeability. Here we investigate the effect of the oxidized phospholipid 1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine (PazePC) on a model membrane of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) using a combination of (13)C-(1)H dipolar-recoupling nuclear magnetic resonance (NMR) experiments and united-atom molecular dynamics (MD) simulations. The obtained experimental order parameter SCH profiles show that the presence of 30 mol % PazePC in the bilayer significantly increases the gauche content of the POPC acyl chains, therefore decreasing the thickness of the bilayer, although with no stable bilayer pore formation.

Interactions and dynamics of two extended conformation adapting phosphatidylcholines in model biomembranes.

In order to obtain molecular level insight into the biophysics of the apoptosis promoting phospholipid 1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine (PazePC) we studied its partitioning into different lipid phases by isothermal titration calorimetry (ITC). To aid the interpretation of these data for PazePC, we additionally characterized by both ITC and fluorescence spectroscopy the fluorescent phospholipid analog 1-palmitoyl-2-{6-[(7-nitro-2-1,3-benzoxadiazol-4-yl)amino]hexanoyl}-sn-glycero-3-phosphocholine (NBD-C6-PC), which similarly to PazePC can adopt extended conformation in lipid bilayers. With the NBD-hexanoyl chain reversing its direction and extending into the aqueous space out of the bilayer, 7-nitro-2,1,3-benzoxadiazol-4-yl (NBD) becomes accessible to the water soluble dithionite, which reduces to non-fluorescent product.

Correction: Formation of lipid/peptide tubules by IAPP and temporin B on supported lipid membranes.

Correction for 'Formation of lipid/peptide tubules by IAPP and temporin B on supported lipid membranes' by Paavo K. J. Kinnunen et al.

Formation of lipid/peptide tubules by IAPP and temporin B on supported lipid membranes.

The conversion of various and to is accelerated by , which are also postulated to represent targets mediating the cytotoxicity of protofibrils. Yet, our understanding of the molecular details governing -catalyzed fibrillogenesis of precursors remains limited. To obtain insight into the intricate interplay of and biophysics we have recently introduced supported bilayers (SLBs) with fluorescent analogs as model biomembranes, observed by time-lapse .

Phospholipid lateral diffusion in phosphatidylcholine-sphingomyelin-cholesterol monolayers; effects of oxidatively truncated phosphatidylcholines.

Oxidative stress is involved in a number of pathological conditions and the generated oxidatively modified lipids influence membrane properties and functions, including lipid-protein interactions and cellular signaling. Brewster angle microscopy demonstrated oxidatively truncated phosphatidylcholines to promote phase separation in monolayers of 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphocholine (POPC), sphingomyelin (SM) and cholesterol (Chol). More specifically, 1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine (PazePC), was found to increase the miscibility transition pressure of the SM/Chol-phase.

Novel endosomolytic peptides for enhancing gene delivery in nanoparticles.

Trapping in the endosomes is currently believed to represent the main barrier for transfection. Peptides, which allow endosomal escape have been demonstrated to overcome this barrier, similarly to the entry of viruses. However, the design principles of such endosomolytic peptides remain unclear.

Identification of Sphingomyelinase on the Surface of Chlamydia pneumoniae: Possible Role in the Entry into Its Host Cells.

We have recently suggested a novel mechanism, autoendocytosis, for the entry of certain microbes into their hosts, with a key role played by the sphingomyelinase-catalyzed topical conversion of sphingomyelin to ceramide, the differences in the biophysical properties of these two lipids providing the driving force. The only requirement for such microbes to utilize this mechanism is that they should have a catalytically active SMase on their outer surface while the target cells should expose sphingomyelin in the external leaflet of their plasma membrane. In pursuit of possible microbial candidates, which could utilize this putative mechanism, we conducted a sequence similarity search for SMase.

Principles of rational design of thermally targeted liposomes for local drug delivery.

Unlabelled: Drug release from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes occurs close to the main transition temperature Tm=41°C. The exact release temperature can be adjusted by additional lipids, which shift Tm. A major issue is drug leakage at 37°C.

Human heat shock protein 70 (Hsp70) as a peripheral membrane protein.

While a significant fraction of heat shock protein 70 (Hsp70) is membrane associated in lysosomes, mitochondria, and the outer surface of cancer cells, the mechanisms of interaction have remained elusive, with no conclusive demonstration of a protein receptor. Hsp70 contains two Trps, W90 and W580, in its N-terminal nucleotide binding domain (NBD), and the C-terminal substrate binding domain (SBD), respectively. Our fluorescence spectroscopy study using Hsp70 and its W90F and W580F mutants, and Hsp70-∆SBD and Hsp70-∆NBD constructs, revealed that binding to liposomes depends on their lipid composition and involves both NBD and SBD.

Golgi-Associated plant Pathogenesis Related protein 1 (GAPR-1) forms amyloid-like fibrils by interaction with acidic phospholipids and inhibits Aβ aggregation.

Golgi-Associated plant Pathogenesis Related protein 1 (GAPR-1) is a mammalian protein that is a member of the Cysteine-rich secretory proteins, Antigen 5 and Pathogenesis related proteins group 1 (CAP) superfamily of proteins. A role for the common CAP domain in the function of the diverse superfamily members has not been described so far. Here, we show by a combination of independent techniques including electron microscopy, Thioflavin T fluorescence, and circular dichroism that GAPR-1 has the capability to form amyloid-like fibrils in the presence of liposomes containing negatively charged lipids.

Pathway and morphological transformation of liposome nanocarriers after release from a novel sustained inner-ear delivery system.

Aim: To validate a novel sustained delivery system of liposome nanocarriers for inner-ear therapy and to investigate the transport pathway for their delivery.

Materials & Methods: Liposome nanocarriers containing gadolinium-tetra-azacyclo-dodecane-tetra-acetic acid (LPS+Gd-DOTA) were developed for MRI tracking the in vitro release profile and for in vivo uptake studies.

Results: Encapsulating Gd-DOTA did not modify the liposomes.

Impact of oxidized phospholipids on the structural and dynamic organization of phospholipid membranes: a combined DSC and solid state NMR study.

Membranes undergo severe changes under oxidative stress conditions due to the creation of oxidized phospholipid (OxPL) species, which possess molecular properties quite different from their parental lipid components. These OxPLs play crucial roles in various pathological disorders and their occurrence is involved in the onset of intrinsic apoptosis, a fundamental pathway in programmed mammalian cell death. However, the molecular mechanisms by which these lipids can exert their apoptotic action via their host membranes (e.

Class specific peptide inhibitors for secretory phospholipases A2.

Phospholipases A2 (PLA2) catalyze the hydrolytic cleavage of free fatty acids from the sn-2 OH-moiety of glycerophospholipids. These enzymes have a number of functions, from digestion to signaling and toxicity of several venoms. They have also been implicated in inflammation and are connected to diverse diseases, such as cancer, ischemia, atherosclerosis, and schizophrenia.

Oxidized phosphatidylcholines in membrane-level cellular signaling: from biophysics to physiology and molecular pathology.

The oxidation of lipids has been shown to impact virtually all cellular processes. The paradigm has been that this involvement is due to interference with the functions of membrane-associated proteins. It is only recently that methodological advances in molecular-level detection and identification have begun to provide insights into oxidative lipid modification and its involvement in cell signaling as well as in major diseases and inflammation.

Oxidized phosphatidylcholines promote phase separation of cholesterol-sphingomyelin domains.

Lipid lateral segregation in the plasma membrane is believed to play an important role in cell physiology. Sphingomyelin (SM) and cholesterol (Chol)-enriched microdomains have been proposed as liquid-ordered phase platforms that serve to localize signaling complexes and modulate the intrinsic activities of the associated proteins. We modeled plasma membrane domain organization using Langmuir monolayers of ternary POPC/SM/Chol as well as DMPC/SM/Chol mixtures, which exhibit a surface-pressure-dependent miscibility transition of the coexisting liquid-ordered and -disordered phases.

Peptide-mediated targeting of liposomes to TrkB receptor-expressing cells.

Background: The neurotrophic receptor tyrosine kinase B (TrkB) has diverse signaling roles in neurons and tumor cells. Accordingly, its suppressive targeting is of interest in neuroblastoma and other tumors, whereas its role in improving survival is focused in neurons. Here we describe targeting of TrkB-binding peptide-conjugated liposomes (PCL) to the TrkB-expressing mouse macrophage-like cell line RAW264, and to all-trans-retinoic acid-treated neuron-like TrkB⁺ SH-SY5Y human neuroblastoma cells.

Gravimetric determination of phospholipid concentration.

Accurate determination of lipid concentrations is an obligatory routine in a research laboratory engaged in studies using this class of biomaterials. For phospholipids, this is frequently accomplished using the phosphate assay (Bartlett, G.R.

Size-dependent passage of liposome nanocarriers with preserved posttransport integrity across the middle-inner ear barriers in rats.

Objective: The goal of this study was to evaluate the impact of liposome nanocarrier size on the efficacy of its transport across the middle-inner ear barriers.

Materials And Methods: The dynamic distribution of liposome nanocarriers encapsulating gadolinium-tetra-azacyclo-dodecane-tetra-acetic acid (LPS+Gd-DOTA) of sizes 95, 130, and 240 nm were observed with a 4.7 T magnetic resonance machine after transtympanic injection in Wistar rats.

Protein-oxidized phospholipid interactions in cellular signaling for cell death: from biophysics to clinical correlations.

Oxidative stress is associated with several major ailments. However, it is only recently that the developments in our molecular level understanding of the consequences of oxidative stress in modifying the chemical structures of biomolecules, lipids in particular, are beginning to open new emerging insights into the significance of oxidative stress in providing mechanistic insights into the etiologies of these diseases. In this brief review we will first discuss the role of lipid oxidation in controlling the membrane binding of cytochrome c, a key protein in the control of apoptosis.

Minimally invasive drug delivery to the cochlea through application of nanoparticles to the round window membrane.

Direct drug delivery to the cochlea is associated with the risk of irreversible damage to the ear. In this study, liposome and polymersome nanoparticles (NPs), both formed from amphiphilic molecules (lipids in liposomes and block copolymers in polymersomes), were tested as potential tools for drug delivery to the cochlea via application onto the round window membrane in adult mice (strain C3H). One day after round window membrane application, both types of NPs labeled with fluorescent markers were identified in the spiral ganglion in all cochlear turns without producing any distinct morphological or functional damage to the inner ear.

Oxidized phosphatidylcholines facilitate phospholipid flip-flop in liposomes.

Lipid asymmetry is a ubiquitous property of the lipid bilayers in cellular membranes and its maintenance and loss play important roles in cell physiology, such as blood coagulation and apoptosis. The resulting exposure of phosphatidylserine on the outer surface of the plasma membrane has been suggested to be caused by a specific membrane enzyme, scramblase, which catalyzes phospholipid flip-flop. Despite extensive research the role of scramblase(s) in apoptosis has remained elusive.

Making unilamellar liposomes using focused ultrasound.

Several techniques are available for making large unilamellar vesicles (LUV) with an average diameter of approximately 100 nm, widely employed as model biomembranes as well as vehicles for drug delivery. Here we describe the use of adaptive focused ultrasound (AFU) for the preparation of LUV from multilamellar vesicles (MLV) and studied the effects of ultrasound intensity and number of cycles per burst (CPB) on the average size of vesicles produced. CPB determines the duration of the intermittent pressure wavetrains emitted by the transducer, and the corresponding relaxation periods.

Activation of phospholipase A2 by Hsp70 in vitro.

We recently suggested a novel mechanism for the activation of phospholipase A2 (PLA2), with a (catalytically) highly active oligomeric state, which subsequently becomes inactivated by conversion into amyloid. This process can be activated by lysophosphatidylcholine which promotes both oligomerization and amyloid activation/inactivation. The heat shock protein 70 (Hsp70), has been demonstrated to be able to revert the conversion of α-synuclein and Alzheimer β-peptide to amyloid fibrils in vitro.

1-Palmitoyl-2-(9'-oxononanoyl)-sn-glycero-3-phosphocholine, an oxidized phospholipid, accelerates Finnish type familial gelsolin amyloidosis in vitro.

Finnish type familial amyloidosis (FAF) is a neurodegenerative disease, which involves the deposition of D187N or -Y mutant gelsolin fragments as amyloid in various tissues, accompanied by dermatologic, neurologic, and ophthalmologic disorders. Like the other amyloid diseases, FAF is associated with oxidative stress. The latter results in an extensive chemical modification of biomolecules, such as the formation of a myriad of phospholipids with oxidatively modified acyl chains containing various functional groups.

Visualization of intracellular trafficking of Math1 protein in different cell types with a newly-constructed nonviral gene delivery plasmid.

Background: In recent years, Math1 gene therapy was indicated to be the future therapy for deafness in combination with other growth factors. However, Math1 delivery using adenovirus-mediated gene delivery or electroporation was impractical. The contribution of Math1 in the combined procedure was not clearly elucidated using the existing plasmids.