Amphiphilic molecules, molecular self-assembly

Figure 14.10 Self-assembly of peptide-amphiphiles into nanofibers (a) a peptide amphi-phile molecule with five distinct regions designed for hydroxyapatite mineralization, (b) a schematic of molecular self-assembly, and (c) a negatively stain transmission electron microscopy image of the nanofibers. Reprinted from Hartgerink et al. (2001). Copyright 2001 American Association for the Advancement of Science.

The monolayer in a multi-component system has been attracting attention from the viewpoints of fundamental understanding on molecular self-assembly [1], as well as its applications for surface modifiers [2], biosensing [3-5], photoswitching [6] and electrical devices [7]. In this system, whether amphiphilic molecules are miscible or immiscible in the monolayer is important for its properties. Therefore, a systematic tmder-standing on the phase separation mechanism in a mixed monolayer appears to be an essential step in the design and constmction of functionalized structures in the system. The phase separation in a monolayer state depends on many factors involving electrostatic interaction, molecular chirality and so on besides thermodynamic parameters such as the subphase temperature and surface pressure. Hence, for... 

Lyotropic mesophases contain at least two chemical components the organic molecule and its solvent. The organic moiety must exhibit some chemical complexity, or otherwise the solvent will simply dissolve the molecule, forming a structureless - and certainly not liquid crystalline - molecular solution of dispersed and disordered molecules. The simplest examples are amphiphilic molecules. The addition of a solvent such as water will selectively hydrate the hydrophilic moiety of each molecule, avoiding the hydrophobic regions. This schizophrenic relationship between the solvent and solute drives the molecules to self-assemble, thereby minimizing the exposure of hydrophobic moieties to the water. (Clearly, the argument holds in reverse if a lipophilic solvent, such as an alkane, is used. Indeed, a combination of hydrophobic and hydrophilic solvents can also lead to the formation of liquid crystalline mesophases.)... 

The most versatile method to prepare such hollow capsules is self-assembly [203-205, 214, 215]. Owing to their amphiphilic nature and molecular geometry, lipid-based amphiphiles can aggregate into spherical closed bilayer structures in water so-called liposomes. It is quite reasonable that the hollow sphere structure of liposomes makes them suitable as precursors for the preparation of more functional capsules via modification of the surfaces with polymers and ligand molecules [205, 216, 217]. Indeed, numerous studies based on liposomes in this context have been performed [205, 209, 213]. 

This paper is not a review covering the entire field of carbohydrate-recognition in any organized system. Many excellent papers have already been devoted to supramolecular systems such as cyclodextrins, podands, coronands or cryptants able to entrap carbohydrate molecules [1]. This article only deals with the molecular recognition of mono and oligosaccharides in organized self-assemblies of amphiphilic carbohydrates (possibly blended with other lipids) in aqueous medium i.e. in assemblies mimicking the cell membrane. 

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