Crown ethers membrane amphiphiles

Shinkai and coworkers prepared numerous novel amphiphilic crowns (Shinkai, 1990) and incorporated them into membranes, formed membranes from them, or used them in liquid crystalline assemblies to control properties (He et al., 1990). Interest in this area continues. Four chiral amphiphilic crown ethers were recently reported that recognize enantiomeric amino acids when examined as Langmuir films (Badis et al., 2004). Finally, it is interesting to note that liposomes formed from amphiphiles (e.g., crown ethers) having neutral headgroups (i. e., niosomes) have been studied as drug delivery vehicles (Uchegbu and Vyas, 1998). 

Furusawa, K. Obata, C. Matsumura, H. Takeuchi, M. Kuwamura, T., (1990) Bilayer membranes of amphiphilic crown ethers with amino acid residue Chem. Lett. 1047-1050. 

Munoz, S. Mallen, J. Nakano, A. Chen, Z. Gay, L Echegoyen, L. Gokel, G. W., (1993) Ultrathin monolayer lipid membranes from a new family of crown ether-based bola-amphiphiles J. Am. Chem. Soc. 115, 1705-1711. 

A new family of crown-ether-based bolaamphiphiles, 21, that aggregate into a previously unknown type of bolaamphisome was prepared by Gokel and coworkers [50]. Evidence was presented on vesicle formation from the aqueous suspension of such bolaform amphiphiles. Several reports describing the synthesis of various macrocyclic models related to archael compounds have also appeared in the literature [51]. Fyles et al. prepared a novel series of asymmetric bis-macrocyclic bolaphiles, 22, and evaluated their transport activities in vesicles and planar bilayer membranes [52]. 

Amphiphilic macrocyclic host molecules have been investigated for many years. Among others, it is known that amphiphilic crown ethers, " cryptands, calixarenes, cyclodextrins, and curcubitnrils can form bilayer vesicles in aqueous solution. However, the host-guest chemistry of such host vesicles remained largely unexplored for many years. Darcy and Ravoo prepared bilayer vesicles composed entirely of amphiphilic cyclodextrin host molecules. These vesicles have a membrane that displays a high density of embedded host molecules that bind hydrophobic guest molecules such as f-butylbenzyl and adamantane derivatives. The characteristic size-selective inclusion behavior of the cyclodextrins is maintained, even when the host molecules are embedded in a hydrophobic... 

Similar to the retention of LLC phases, thermotropic LC assemblies have also been covalently captured, leading to robust polymer films that retain the original nanostructures. Mdller et al. cross-linked columnar assemblies formed by amphiphile 7 bearing crown ether units inside the pores of track-etched membranes and obtained membranes containing oriented channels. Salt-diffusion experiments demonstrated that the resultant nanoporous membrane displayed... 

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