Amphiphilic properties

An even coarser description is attempted in Ginzburg-Landau-type models. These continuum models describe the system configuration in temis of one or several, continuous order parameter fields. These fields are thought to describe the spatial variation of the composition. Similar to spin models, the amphiphilic properties are incorporated into the Flamiltonian by construction. The Flamiltonians are motivated by fiindamental synnnetry and stability criteria and offer a unified view on the general features of self-assembly. The universal, generic behaviour—tlie possible morphologies and effects of fluctuations, for instance—rather than the description of a specific material is the subject of these models. 

Diederich F, Jonas U, Gramlich V, Herrmann A, Ringsdorf H and Thilgen C 1993 Synthesis of a fullerene derivative of benzo[18]crown-6 by Diels-Alder reaction complexation ability, amphiphilic properties, and x-ray crystal structure of a dimethoxy-1,9-(methano[1, 2]benzomethano)fullerene[60] benzene clathrate Helv. Chim. Acta 76 2445-53... 

The polymers described so far have relatively flexible main chains which can result in complex confonnations. In some cases, tliey can double back and cross over tliemselves. There are also investigations on polymers which are constrained to remain in a confonnation corresponding, at least approximately, to a straight line, but which have amphiphilic properties tliat ensure tliat tliis line is parallel to tire water surface. Chiral molecules are one example and many polypeptides fall into tliis class [107]. Another example is cofacial phtlialocyanine polymers (figure C2.4.9). 

Fischer, H., Kansy, M., Bur, D. CAFCA a novel tool for the calculation of amphiphilic properties of charged drug molecules. Chimia 2000, 54, 640-645. 

The approach presented here can help us better understand the behavior of some enzymatic systems in vivo. It can be useful for optimizing the operating conditions of bioreactors containing chemical species with amphiphilic properties. 

Characterization. The overall structure and amphiphilic properties of the networks were characterized by DSC and swelling experiments, respectively. The Mc of the PDMAAm segments (that is the molecular weight between PIB crosslinks of the PDMAAm segment) was calculated by... 

Hazen and Deamer looked at the chemical and physical properties of the end products of hypothetical prebiotic reactions carried out under extreme conditions of pressure and temperature, for example in CCh-rich regions of hydrothermal vents. The results of laboratory experiments indicate that prebiotic syntheses leading to a variety of products could have occurred in hydrothermal systems some of these have amphiphilic properties, and would have been capable of self-organisation processes. 

It may seem curious to make specific mention of this matter, but in a biological context, it is crucial. The nuclei of porphyrins and related systems are hydrophobic it appears to be generally desirable that the photosensitizer has some degree of intermediate polarity (i.e., amphiphilic properties Section 9.22.3) and the incorporation of a metal, such as zinc(II), which can take on an axial ligand (e.g., H20 in aqueous media, or RNH2 in a biological fluid), or magnesium(II), which can take on two, is expected to enhance solubility in hydroxylic solvents, and shift the... 

The same group modified the linker by using different numbers of carbon atoms (1, 5, 10) to afford variations of the local saccharide concentrations at the dendrimer surface.418 This study was aimed to determine the influence of this linker parameter on the glycodendrimer-protein interactions, the relationship between structure and water solubility, and to investigate amphiphilic properties. 

Liposomes are artificial structures composed of phospholipid bilayers exhibiting amphiphilic properties (Chapter 22). In complex liposome morphologies, concentric spheres or sheets of lipid bilayers are usually separated by aqueous regions that are sequestered or compartmentalized... 

If the substances have passed the stratum comeum, they also generally diffuse into the living part of the epidermis, reach the circulation, and then have systemic effects depending on the amount absorbed. Because these are often constituents of formulations, one generally expects them to have little direct influence on skin penetration. However, their amphiphilic properties allow them to form new systems with the body s constituents and even to change the physical state of water in the skin. By this means, a pathway is cleared for other hydrophilic substances to gain entry into the general circulation. 

P. Saarinen-Savolainen, T. Jarvinen, P. Suhonen, A. Urtti, Amphiphilic Properties of Pilocarpine Prodrugs , Int. J. Pharm. 1996, 133, 171-178. 

Lyotropic liquid crystals differ from thermotropic liquid crystals. They are formed by mesogens which are not the moleeules themselves but their hydrates or solvates as well as associates of hydrated or solvated molecules. In the presenee of water or a mixture of water and an organie solvent as the most important solvents for drug molecules, the degree of hydration or solvation, respectively, depends on the amphiphilic properties of a drug moleeule. Hydration of the mostly rod-shaped molecule— and the same holds for solvation—results in different geometries, eone or cylinder [5] (Fig. 3). 

For therapeutical purposes, a likewise frequently used group of drug compounds are the nonsteroidal anti-inflammatory drugs (NSAID). Among the best known representatives of the aryl acetic acid derivatives is diclofenac as well as ibuprofen, an aryl propionic acid derivative. As both have acidic properties, they dissociate while being dissolved and may form salts with amphiphilic properties. Together with appropriate counterions these amphiphilic organic acids may form lyotropic mesophases with water even at room or body temperature, for example, diclofenac diethylamine... 

Finally, Lecomte and coworkers reported the synthesis of mikto-arm star-shaped aliphatic polyesters by implementing a strategy based on click chemistry (Fig. 36) [162]. Firstly, the polymerization of sCL was initiated by a diol bearing an alkyne function. The chain-ends were protected from any further undesired reaction by the esterification reaction with acetyl chloride. The alkyne was then reacted with 3-azidopropan-l-ol. The hydroxyl function located at the middle of the chain was then used to initiate the ROP of sCL and y-bromo-s-caprolactone. Finally, pendant bromides were reacted successfully with sodium azide and then with N, N-dimethylprop-2-yn-l-amine to obtain pendant amines. Under acidic conditions, pendant amines were protonated and the polymer turned out to exhibit amphiphilic properties. 

The effect of chain length on surface tension arises from the fact that, as the hydrophobicity increases with each -CH2- group, the amphiphile molecule adsorbs more at the surface. This will thus be a general trend in more complicated molecules also, such as proteins and other polymers. In proteins, the amphiphilic property arises from the different kinds of amino acids (25 different amino acids). Some amino acids have lipophilic groups (such as phenylalanine, valine, leucine, etc.), while others have hydrophilic groups (such as glycine, aspartic acid, etc.) (Figure 3.4). 

The two products differ in polarity and thus in hydrophilicity.The acrylic acid-b-sty-rene-b-acrylic acid triblock copolymer exhibits amphiphilic properties and forms an emulsion in diiute sodium hydroxide solution where the acid groups are neutralized. 

In this chapter, fluorinated saccharidic compounds are considered in the following order fluorinated analogues of furanoses and nucleosides, followed by pyranoses and then fluoromethylated sugars. Finally, a brief summary of perfluoroalkylated sugars and of their amphiphilic properties is given. 

Compounds having O—CF3 (or O—Rf) and S—CF3 (or S—Rf). They are relatively stable derivatives with interesting amphiphilic properties. Moreover, in some cases they are glycosidase inhibitors. 

In the heterocyclic series, racemic 3-(fur-2-yl)alanine has been prepared from furfural using this approach. In addition, (3-(pyrid-3-yl)alanine, ° p-(quinol-3-yl)alanine, ° a p-(benzofuranyl)alanine derivative, 2-amino-3-(2,2 -bipyridi-nyl)propanoic acid, and some interesting derivatives of histidines—in particular 1-alkylhistidines with amphiphilic properties have all been synthesized using this methodology. The complete reaction sequence starting from an aldehyde and an A-acylamino acid derivative is shown in Scheme 7.150. 

Very special amphiphilic properties of a divalent sulfur atom is witnessed in the reaction of a-thiomethylenecycloalkanones with acrylic esters under basic conditions [141]. The donor character of the allylic methylene group is enhanced by the sulfur (acting as an acceptor), yet the Michael cyclization that follows would be facilitated by a donor at that position. 

Liposomes are artificial structures composed of phospholipid bilayers exhibiting amphiphilic properties (chapter 12). In complex liposome morphologies, concentric spheres or sheets of lipid bilayers are usually separated by aqueous regions that are sequestered or compartmentalized from the surrounding solution. The phospholipid constituents of liposomes consist of hydrophobic lipid tails connected to a head constructed of various glycerylphosphate derivatives. The hydrophobic interaction between the fatty acid tails is the primary driving force for creating liposomal bilayers in aqueous solutions. 

In this review we summarize and discuss the amphiphilic properties of polyoxyethylene (PEO) macromonomers and PEO graft copolymer molecules, the aggregation of amphiphilic PEO macromonomers into micelles, the effect of organized aggregation of macromonomers on the polymerization process, and the kinetics of radical polymerization and copolymerization of PEO macromonomer in disperse (dispersion, emulsion, miniemulsion, microemulsion, etc.) systems [1-5]. 

EXTRACTANT SOLUTIONS ARE COMPLEX FLUIDS 7.2.1 Amphiphilic Properties of Extractant... 

Delmau et al. (129) studied the self-association of fluorinated alcohols used as diluent modifiers for the selective extraction of cesium from caustic media by calixarene-crown ethers. They found that the salt distribution ratio is enhanced by the modifiers and explained this by a solubilization effect of the modifier due to its amphiphilic properties. 

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