Bilayer formation

Rutland M W and Parker J L 1994 Surface forces between silica surfaces in cationic surfactant solutions adsorption and bilayer formation at normal and high pH Langmuir 0 1110-21... 

The (I)-(III)-samples sorption ability investigation for cationic dyes microamounts has shown that for DG the maximum rate of extraction is within 70-90 % at pH 3. The isotherm of S-type proves the physical character of solution process and a seeming ionic exchange. Maximal rate of F extraction for all samples was 40-60 % at pH 8 due to electrostatic forces. The anionic dyes have more significant affinity to surface researching Al Oj-samples comparatively with cationic. The forms of obtained soi ption isotherms atpH have mixed character of H,F-type chemosorption mechanism of fonuation of a primary monolayer with the further bilayers formation due to H-bonds and hydrophobic interactions. The different values of pH p for sorbents and dyes confirm their multifunctional character and distinctions in the acid-base properties of adsoi ption centers. 

Figure 5. Scheme of the bilayer formation at the tip of the patch pipets (a) and single channel recordings of pardaxin pores (b). 

Fig. 23 A projection of the structure of [Ni(ebbg)]Cl2-H20 onto the (0 1 0) plane showing the bilayer formation (atom identification as for Fig. 22) [47,48]...

Totally synthetic bilayers show liquid crystalline properties similar to those of lecithin bilayers (Nagamura et al., 1978 Kano et al., 1979). Bilayer formation has also been observed for dialkyl compounds with anionic head groups such as [2] and [3] (Kunitake and Okahata, 1978a Mortara et al., 1978), and with nonionic and zwitterionic head groups as in [4] and [5] (Okahata et al., 1978a). 

Holland JW, Cullis PR, Madden TD. Poly(ethyleneglycol)-lipid conjugates promote bilayer formation in mixtures of non-bilayer-forming lipids. Biochemistry... 

The polar character of the liposomal core makes the encapsulation of polar drug molecules possible. Amphiphilic and lipophilic molecules are solubilized within the phospholipid bilayer according to their affinity toward the phospholipids. Participation of nonionic surfactants instead of phospholipids in the bilayer formation results in Niosomes . The term sphingosomes is suggested for vesicles from sphingolipids. However, the nomenclature is not consistent, and the term liposomes is used as a general term, although vesicles would be the better choice. 

As w ell as lateral heterogeneity in mixed protein layers, there is also the possibility of segregation of biopolymer components perpendicular to the interface, z.e., bilayer formation (Dickinson, 1995, 2009). Let us consider the case of an interface containing casein and whey protein in an emulsion system. The images in Figure 8.4 are confocal micrographs... 

Out of a variety of polymerizable lipids tested for possible use of bilayer formation, only three systems exhibited BLM lifetimes of more than a few minutes (Table 2 26)). These BLMs were characterized by measuring their resistance and capacitance (Table 2., see26> for details). The data obtained were comparable with values obtained with egg lecithin the most frequently used material for preparing BLMs. 

FIGURE 34. Proposed models of bilayer formation in the SAd phase... 

A full discussion of water penetration into micelles is beyond the scope of this chapter. The results described above, and others employing longer chain keto -surfactants in other micelles and bilayers, indicated a trend toward less water penetration to the core of aggregates as the surfactant tail length increased, and as aggregate curvature decreased (bilayer formation). More data from FT-IR studies... 

There are a great many methods by which small molecules can be assembled to form nanotubes and other similar columnar aggregates [50]. Unlike the stacked disc methodology employed by Fenniri s group, Russell and co-workers took a completely different approach, which consisted of nanotubes made by way of rolled-up bilayers [48], Their study of biocidal nanotubes from a self-assembled diacetylene salt employed a hydrophobically driven bilayer type of self-assembly step. This bilayer formation was based on the alignment of the hydrophobic chains, including aligned Ji-systems of the acetylenes on the interior of the bilayer and the polar hydrobromide salts of an amine on the exterior of the bilayer (Fig. 7.6). 

A problem that is rarely taken into account is related to the fact that the water concentration shows a conspicuous gradient within the stratum corneum thickness. These factors are likely to influence the physical state of lipids in bilayer formations, and therefore we expect lipid barrier structure to vary within the thickness of the stratum corneum.53... 

Sasai, R., Shinya, N., Shichi, T., Takagi, T. and Gekko, K. (1999). Molecular alignment and photodimerization of 4 -chloro-4-stilbenecarboxylic acid in hydrotalcite clays bilayer formation in the interlayers. Langmuir 15, 413. 

Subsequently, the ion channel activity of 34 was studied using planar bilayer methods.50c Peptide 34 was either introduced to the bulk KC1 solution or mixed with the lipid sample prior to bilayer formation. In the first method, incorporation proved difficult, possibly due to the high tendency of 34 to form aggregates. In the second method the stability of the bilayer was perturbed and single-channels were not obtained. It was postulated that this was due to the adsorption of the peptide onto the surface of the membrane due to electrostatic interactions of the crown ethers with the polar head groups. However as soon as the peptide was incorporated successfully into the bilayer, i.e. peptide parallel to the lipid hydrocarbons, singlechannel events were recorded indicative of 34 functioning in a unimolecular fashion. 

As it is well known, the contacts between drops (in emulsions), solid particles (in suspensions) and gas bubbles (in foams) are accomplished by films of different thickness. These films, as already discussed, can thin, reaching very small thickness. Observed under a microscope these films reflect very little light and appear black when their thickness is below 20 nm. Therefore, they can be called nano foam films. IUPAC nomenclature (1994) distinguishes two equilibrium states of black films common black films (CBF) and Newton black films (NBF). It will be shown that there is a pronounced transition between them, i.e. CBFs can transform into NBFs (or the reverse). The latter are bilayer formations without a free aqueous core between the two layers of surfactant molecules. Thus, the contact between droplets, particles and bubbles in disperse systems can be achieved by bilayers from amphiphile molecules. 

Temperature dependence of the critical concentration Ce of a foam bilayer formation. The Cc concentration (see Eq. (3.129)) of formation of DMPC foam bilayer was determined on the basis of observations of the final state which the foam film reached during its drainage (see Section 3.2), i.e. either rupture at a definite critical thickness without formation of black spots occurs, or formation of foam bilayer via black spots is observed. Rupture at critical thickness occurred at lower DMPC concentrations in the solution (C < Cc) and black spots were formed at higher concentrations (C > Cc). These black spots encountered the film turning it into a foam bilayer of constant radius. At each temperature a series of observations were carried out at various DMPC concentrations for the determination of Cc (the minimum DMPC concentration at which a foam bilayer is formed). This concentration is... 

Briand E, Zach M, Svedhem S, Kasemo B, Petronis S (2010) Combined QCM-D and EIS study of supported lipid bilayer formation and interaction with pore-forming peptides. Analyst 135 343-350... 

The adsorption of binary mixtures of anionic surfactants of a homologous series (sodium octyl sulfate and sodium dodecyl sulfate) on alpha aluminum oxide was measured. A thermodynamic model was developed to describe ideal mixed admicelle (adsorbed surfactant bilayer) formation, for concentrations between the critical admicelle concentration and the critical micelle concentration. Specific... 

The major driving force for hpid bilayer formation is hydrophobic interaction. This interaction is much less specific and less directional than the hydrogen bonding and metal coordination interactions that are used in precisely programmed supramolecular assembhes. A simphfied lipid structure is depicted in Fig. 4.18. A lipid molecule consists of a hydrophihc head and... 

Another fundamental question about bilayer formation is whether am-phiphiUc molecules are really necessary. The answer to this question is y s... 

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