Search results for "layer"
showing 10 items of 2667 documents
Hydrophobic mismatch of mobile transmembrane helices: Merging theory and experiments
2012
Abstract Hydrophobic mismatch still represents a puzzle for transmembrane peptides, despite the apparent simplicity of this concept and its demonstrated validity in natural membranes. Using a wealth of available experimental 2 H NMR data, we provide here a comprehensive explanation of the orientation and dynamics of model peptides in lipid bilayers, which shows how they can adapt to membranes of different thickness. The orientational adjustment of transmembrane α-helices can be understood as the result of a competition between the thermodynamically unfavorable lipid repacking associated with peptide tilting and the optimization of peptide/membrane hydrophobic coupling. In the positive misma…
An enzyme caught in action: Direct imaging of hydrolytic function and domain formation of phospholipase A2 in phosphatidylcholine monolayers
1989
AbstractPhospholipase A2, a ubiquitous lipolytic enzyme that actively catalyses hydrolysis of phospholipids, has been studied as a model for enzyme-substrate reactions, as a membrane structural probe, and as a model for lipid-protein interactions. Its mechanism of action remains largely controversial. We report here for the first time direct microscopic observation of the lipolytic action of fluorescently marked phospholipase A2 (Naja naja naja) against phosphatidylcholine monolayers in the lipid phase transition region. Under these conditions, phospholipase A2 is shown to target and hydrolyse solid-phase lipid domains of L-α-dipalmitoylphosphatidylcholine. In addition, after a critical ext…
Small unilamellar liposomes from mixed natural and polymeric phospholipids: stability and susceptibility to phospholipase A2.
1991
The concept of the uncorkable liposome composed of phase-separated mixtures of a polymerized phospholipid and an enzymically digestible phospholipid has been investigated, using small unilamellar vesicles composed of mixtures of (polymerized) dienoylphosphatidylcholine (DENPC) and dimyristoylphosphatidylcholine (DMPC). Mixed liposomes, even those containing only 10% DENPC, were much more stable than DMPC liposomes, as indicated by the release of entrapped [3H]inulin or [14C]glucose. DMPC liposomes released entrapped solute on exposure to phospholipase A2, whereas mixed vesicles were resistant. The results are compared with those of an earlier study on monolayers of similar compositions. It …
Production and characterisation of recombinant forms of human pulmonary surfactant protein C (SP-C):Structure and surface activity
2006
Udgivelsesdato: 2006-Apr Surfactant protein C (SP-C) is an essential component for the surface tension-lowering activity of the pulmonary surfactant system. It contains a valine-rich alpha helix that spans the lipid bilayer, and is one of the most hydrophobic proteins known so far. SP-C is also an essential component of various surfactant preparations of animal origin currently used to treat neonatal respiratory distress syndrome (NRDS) in preterm infants. The limited supply of this material and the risk of transmission of infectious agents and immunological reactions have prompted the development of synthetic SP-C-derived peptides or recombinant humanized SP-C for inclusion in new prepar…
Double-spanning Plant Viral Movement Protein Integration into the Endoplasmic Reticulum Membrane Is Signal Recognition Particle-dependent, Translocon…
2005
The current model for cell-to-cell movement of plant viruses holds that transport requires virus-encoded movement proteins that intimately associate with endoplasmic reticulum membranes. We have examined the early stages of the integration into endoplasmic reticulum membranes of a double-spanning viral movement protein using photocross-linking. We have discovered that this process is cotranslational and proceeds in a signal recognition particle-dependent manner. In addition, nascent chain photocross-linking to Sec61alpha and translocating chain-associated membrane protein reveal that viral membrane protein insertion takes place via the translocon, as with most eukaryotic membrane proteins, …
Could structural changes in the retinal layers be a new biomarker of mental disorders? A systematic review and thematic synthesis.
2019
It has recently been suggested that alterations of the layers of the retina could be a biomarker of specific mental disorders since they originate in the same embryonic layer as the brain and both are interconnected through the optic nerve. The purpose of this article is to offer a systematic review of the literature and a thematic synthesis on the current state of the alterations of the retina layers identified by optical coherence tomography in patients with schizophrenia, bipolar disorder and major depression. For this purpose, we performed a bibliographic search, a systematic review of the studies and a thematic synthesis of the reported findings. Patients with schizophrenia have more a…
Multilayered cultural identity and the perception of the self
2012
This qualitative study examines the reciprocal relationship between a person’s multilayered cultural identity (MCI) and the concept of self (CoS), that is presented purely on a theoretical level and encompasses various theories. Nowadays, in an increasingly globalising world, it is not enough to merely look at a national, ethnic or other type of identity. It is important to realise that there are different layers in an identity that one can view themselves through. The ways an individual perceives themselves through their multicultural background can also be different. This thesis helps identify the ways a person can see themselves. The thesis also attempts to explain the varied nature of o…
Continuum Monte Carlo simulation of phase transitions in rod-like molecules at surfaces
1994
Stiff rod-like chain molecules with harmonic bond length potentials and trigonometric bond angle potentials are used to model Langmuir monolayers at high densities. One end of the rod-like molecules is strongly bound to a flat two-dimensional substrate which represents the air-water interface. A ground-state analysis is performed which suggests phase transitions between phases with and without collective uniform tilt. Large-scale off-lattice Monte Carlo simulations over a wide temperature range show in addition to the tilting transition the presence of a strongly constrained melting transition at high temperatures. The latter transition appears to be related to two-dimensional melting of th…
Encapsulation capacity and natural payload delivery of an anticancer drug from boron nitride nanotube.
2016
The behavior of confined anticancer carboplatin (CPT) molecules in a single (10, 10) boron nitride nanotube (BNNT) was studied by means of molecular dynamics simulations. Our study revealed a very large storage capacity of BNNT. Analysis of the energy profiles depending on the number of confined molecules, and on their spatial organization allowed us to quantify the ability of BNNT to vectorize CPT. Indeed, BNNT despite its small radius presented a large inner volume that favored stable encapsulation of multiple active anticancer molecules. Moreover, in our molecular dynamics simulations, the empty BNNT and the BNNT filled with CPT diffused spontaneously to the cell membrane and were able t…
Unsteady Separation and Navier-Stokes Solutions at High Reynolds Numbers
2010
We compute the numerical solutions for Navier-Stokes and Prandtl’s equations in the case of a uniform bidimensional flow past an impulsively started disk. The numerical approx- imation is based on a spectral methods imple- mented in a Grid environment. We investigate the relationship between the phenomena of unsteady separation of the flow and the exponential decay of the Fourier spectrum of the solutions. We show that Prandtl’s solution develops a separation singularity in a finite time. Navier-Stokes solutions are computed over a range of Reynolds numbers from 3000 to 50000. We show that the appearance of large gradients of the pressure in the stream- wise direction, reveals that the visc…