Search results for "bilayer"
showing 10 items of 391 documents
Label-Free Detection of Protein-Ligand Interactions by the Quartz Crystal Microbalance
2005
In recent years the quartz crystal microbalance (QCM) has been accepted as a powerful technique to monitor adsorption processes at interfaces in different chemical and biological research areas. In the last decade, the investigation of adsorption of biomolecules on functionalized surfaces turned out to be one of the paramount applications of the QCM comprising the interaction of nucleic acids, specific molecular recognition of protein-receptor couples, and antigen-antibody reactions realized in immunosensors. The advantage of the QCM technique is that it allows for a label free detection of molecules. This is a result of the fact that the frequency response of the quartz resonator is propor…
Langmuir-Blodgett Mono- and Multilayer Assemblies of Amphiphilic Liquid- Crystalline n-Alkyl-4′-n-alkoxybiphenyl-4-carboxylates. I
1991
Five n-Alkyl-4′-Alkoxy-biphenyl-4-carboxylates were investigated as Langmuir monolayers at the air/ water interface and as Langmuir-Blodgett (LB) films on solid supports. All five compounds form stable monolayers at the air/water interface and can be transferred onto solid supports yielding LB-films, whose structures and kinetic behavior strongly depend on the headgroup. The structures of the LB-films were investigated by means of optical textures and X-ray diffraction and compared with the structures of the corresponding bulk phases which were investigated by means of Differential Scanning Calorimetry and X-ray powder diffraction. The LB-films of the acid and the two methyl esters exhibit …
From Hydrophobic Matching to Interfacial Tuning: New Ideas for the Mutual Adaptation Between Membranes and Peptides
2009
It is widely accepted that membrane proteins and lipid bilayers are complementary in terms of the distribution in space of their hydrophobic and polar regions. Similarly, it is also accepted that the hydrophobic parts of the protein and the membrane must adapt to each other. Classically these ideas are rationalized under the concept of hydrophobic matching, which predicts a number of possible mechanisms by which proteins can vary their effective hydrophobic length, or membranes can change their hydrophobic thickness. Such effects have been studied in detail for simplified systems, like transmembrane peptides or protein fragments, which generally show that optimizing peptide orientation is t…
Role of hexagonal structure-forming lipids in diadinoxanthin and violaxanthin solubilization and de-epoxidation
2005
In this study, we have examined the influence of different lipids on the solubility of the xanthophyll cycle pigments diadinoxanthin (Ddx) and violaxanthin (Vx) and on the efficiency of Ddx and Vx de-epoxidation by the enzymes Vx de-epoxidase (VDE) from wheat and Ddx de-epoxidase (DDE) from the diatom Cyclotella meneghiniana, respectively. Our results show that the lipids MGDG and PE are able to solubilize both xanthophyll cycle pigments in an aqueous medium. Substrate solubilization is essential for de-epoxidase activity, because in the absence of MGDG or PE Ddx and Vx are present in an aggregated form, with limited accessibility for DDE and VDE. Our results also show that the hexagonal st…
Controllable membrane remodeling by a modified fragment of the apoptotic protein Bax.
2021
Intrinsic apoptosis is orchestrated by a group of proteins that mediate the coordinated disruption of mitochondrial membranes. Bax is a multi-domain protein that, upon activation, disrupts the integrity of the mitochondrial outer membrane by forming pores. We strategically introduced glutamic acids into a short sequence of the Bax protein that constitutively creates membrane pores. The resulting BaxE5 peptide efficiently permeabilizes membranes at acidic pH, showing low permeabilization at neutral pH. Atomic force microscopy (AFM) imaging showed that at acidic pH BaxE5 established several membrane remodeling modalities that progressively disturbed the integrity of the lipid bilayer. The AFM…
Kinetics of Molecule Transfer between Lipid Vesicles and β-Cyclodextrins
1996
Abstract We propose a calorimetric method based on the van't Hoff model of depression of the freezing temperature to investigate slow kinetics involving lipid vesicles (liposomes) and drug–β-cyclodextrin (Cyd) complexes. Some nonsteroidal antiinflammatory drugs (NSAIDs) were examined and standard phospholipid liposomes were used in our experiments. Three different kinetic processes were investigated: (a)9Transfer of drugs from water-soluble Cyd-complexes to void liposomes. (b)9Uptake of drugs from the surface of liposomes by free Cyd dissolved in the aqueous phase. (c)9Exchange of drugs from loaded to void vesicles, and the effect of free Cyd in enhancing such a transfer. Most experiments w…
Synthesis and phase behaviour of liquid-crystalline side group polyesters
1990
Abstract Several series of liquid-crystalline side group polymers with a polyester backbone structure have been synthesized using mesogenic diethylmalonate and 1,3-propanediol derivatives. The structures of the polymer backbone and the mesogenic units have been varied systematically. As shown by differential scanning calorimetry, polarizing microscopy and X-ray diffraction, the side group polyesters exhibit nematic and/or smectic mesophases. Polyesters synthesized from mesogenic diethylmalonate derivatives can tolerate long non-mesogenic segments in the polymer main chain without losing their liquid crystal properties. X-ray studies suggest that some of the smectic polymers exhibit interdig…
Self-organization of amphiphilic N-acylated linear polyethyleneimines: investigation of a reversible monolayer collapse
1996
Abstract Poly-N-4-decyloxybenzoylethyleneimine, highly crystalline in bulk, forms a stable monolayer at the air-water interface which undergoes a reversible collapse into a probable bilayer structure at higher surface pressures. We achieved transfer both from the monolayer and “bilayer” region of the polymer film at the water surface onto hydrophilic and hydrophobized quartz supports. Based on X-ray investigations on the deposited Langmuir-Blodgett films, a possible mechanism for the reversible collapse is proposed.
Influence of hydrocolloid nature on the structure and functional properties of emulsified edible films
2009
Abstract To investigate the influence of polymer behaviors on the structure and the functional properties of emulsified films, agar (AG) and cassava starch (CAS) were used as hydrocolloid continuous phases in which hydrogenated vegetable oil (VGB81) was dispersed. Different ratios of hydrophilic/hydrophobic materials (HB/HL) were also used in film formulations to study the evolution of film-emulsion structure. Microscopically observed, VGB–CAS emulsified films exhibit a similar bilayer structure. However, there was just a migration and an aggregation of lipid particles. There was no coalescence which could form a continuous “lipid layer” necessary for an effective barrier. Moreover, they co…
Structural variations of liquid crystalline polymers with phasmidic-type mesogens
1989
Abstract The fixation of phasmidic-type mesogens through spacer groups to polysiloxane backbones provided a method of obtaining liquid crystalline polymers with phasmidic mesogens as side groups. The polymer 6b showed a bilayer structure in the mesophase range. The tendency to form liquid-crystalline phase depends on the number and the length of alkoxy substituents.