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Black lipid membrane composition and interface state as determinants of mitochondrial porin (VDAC) incorporation and assembly
No full textAβP1-42 incorporation and channel formation in planar lipid membranes: the role of cholesterol and its oxidation products
No full textAmyloid beta peptide (AP) is a natural peptide, normally released into the cerebrospinal fluid (CSF), that plays a key role in Alzheimer’s disease. The conversion of the peptide from a native soluble form to a non-native and often insoluble form, such as small and large aggregates, protofibrils and fibrils of AP appears to be implicated in the pathogenesis of AD. Although the molecular mechanisms of AP neurotoxicity are not fully understood, a large body of data suggests that the primary target of amyloid peptides is the cell membrane of neurons, that may modulate the structural and functional conversion of AP into assemblies involved in pathological processes. In our study, we provide a systematic investigation of AP1-42’s ability to incorporate and form channel-like events in membranes of different lipid composition and focus on cholesterol and its oxidation products. We propose that cholesterol and its oxidation products can be considered neuroprotective factors because a) by favouring AP1-42 insertion into membranes, the fibrillation/clearance balance shifts toward clearance; b) by shifting channel selectivity toward anions, the membrane potential is moved far from the threshold of membrane excitability, thus decreasing the influx of calcium into the cell
Modulation of some membrane proteins by cholesterol and related sterols
No full textBiological membranes, depicted being as composed of a fluid bilayer considered to be a uniform semi-permeable barrier, have evolved into a complex and dynamic environment in which lipid assembly forms a fluid platform that segregates membrane components into a sort of patchwork of domains. Cholesterol, an essential component of animal cell membranes whose concentration is tightly controlled by a feedback system, is often found in domains in biological and model membranes. A wide variety of physiological functions such as signal transduction processes, pathogen entry, protein sorting and trafficking, modulation of peptide incorporation and channel formation - have been attributed to these domains. The focus of this review is to gain some understanding on how membrane cholesterol and closely-related sterols modulate some proteins
Choline modulation of the ABP1-40 channel reconstituited into a model lipid membrane
No full textNicotinic acetylcholine receptors (AChRs), implicated in memory and learning, in subjects affected by Alzheimer’s disease result
altered. Stimulation of α7-nAChRs inhibits amyloid plaques and increases ACh release. β-amyloid peptide (AβP) forms ion
channels in the cell and model phospholipid membranes that are retained responsible in Alzheimer disease. We tested if choline,
precursor of ACh, could affect the AβP1-40 channels in oxidized cholesterol (OxCh) and in palmitoyl-oleoyl-phosphatidylcholine
(POPC):Ch lipid bilayers. Choline concentrations of 5 × 10−11 M–1.5 × 10−8M added to the cis- or trans-side of membrane
quickly increased AβP1-40 ion channel frequency (events/min) and ion conductance in OxCh membranes, but not in POPC:Ch
membranes. Circular Dichroism (CD) spectroscopy shows that after 24 and 48 hours of incubation with AβP1-40, choline stabilizes
the random coil conformation of the peptide, making it less prone to fibrillate. These actions seem to be specific in that ACh is
ineffective either in solution or on AβP1-40 channel incorporated into PLMs
Effect of cations on b-Amyloid Peptide (AbP 1-40) channels incorporated into oxidized cholesterol planar membranes
No full textLong-term effect of Ca2+ on AbP1-42 channel activity when incorporated into planar lipid membranes
No full textMagainin 2 channel formation in planar lipid membranes: the role of lipid polar groups and ergosterol
No full textMagainin 2, a polycationic peptide, displays
bactericidal and tumoricidal activity, presumably interacting
with negatively charged phospholipids in the
membrane hosts. In this work, we investigate the role
played by the lipid head-group in the interactions and selfassociation
of magainin 2 during pore formation in lipid
bilayers. Two methods are used: single-channel and
macroscopic incorporation into planar lipid membranes.
Single-channel incorporation showed that magainin 2 did
not interact with zwitterionic membranes, while the addition
of negatively charged dioleoylphosphatidylglycerol
to the membrane leads to channel formation. On the other
hand, magainin 2 did not form channels in membranes
made up of dioleoylphosphatidylserine (DOPS), although
the addition of ergosterol to DOPS membranes leads to
channel formation. This finding could indicate that ergosterol
may be a possible target of magainin 2 in fungal
membranes. Further support for this hypothesis comes
from experiments in which the addition of ergosterol to
palmitoyloleoylphosphatidylcholine membranes induced
channel formation. Besides the role of negatively charged
membranes, this study has shown that magainin 2 also
forms channels in membranes lacking heads, such as
monoolein and oxidized cholesterol, indicating an interaction
of magainin 2 with acyl chains and cholesterol,
respectively. This finding provides further evidence that
peptide binding and assembly in lipid membranes is a
complex process driven by electrostatic and/or hydrophobic
interactions, depending on the structure of the
peptide and the membrane composition
Acetylcholine modulates the AbP1-40 single channel reconstituted in oxidized cholesterol PLM
No full textEffects of n-Octyl-β-D-Glucopyranoside on Human and Rat Erythrocyte Membrane Stability against Hemolysis
Full text linkThe practical importance for the pharmaceutical and cosmetics industries of the interactions between biological membranes and surfactant molecules has led to intensive research within this area. The interactions of non-ionic surfactant n-octyl-β-D-glucopyranoside (OG) with the human and rat erythrocyte membranes were studied. The in vitro hemolytic and antihemolytic activities were determined by employing a method in which both erythrocytes were added to the hypotonic medium containing OG at different concentrations, and the amount of haemoglobin released was determined. n-octyl-β-D-glucopyranoside was found to have a biphasic effect on both types of erythrocyte membrane. We also investigated the interactions of OG with the erythrocyte membrane in isotonic medium; the dose-dependent curves show similar behaviour in both human and rat erythrocytes. Our results showed that OG has greater antihemolytic potency on rat than on human erythrocytes; furthermore, rat erythrocytes were more sensitive than human erythrocytes to hypotonic shock. How the different lipoprotein structure of these erythrocytes determines a difference in antihemolytic activity is discussed
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