Amphiphiles generalized structure

Thus far, the interactions of phospholipid head groups have been considered, because the model was applied toward rationalizing the membranolysis of eukaryotic cells such as erythrocytes, and PLs are the primary constituents of eukaryotic cell membranes. A reasonable question to ask at this time is whether the above results are relevant to prokaryotic membranes. Although PLs constitute a smaller proportion of the prokaryotic cell wall and cell membrane, the other constituent molecules such as liopolysaccharides and teichoic acids, are also amphiphilic. The general structure of a hydrophilic portion attached to a hydrophobic tail is common... 

Figure 1. Generalized amphiphilic molecular structure. The lipophilic portion is the long-chain fatty acid stearic acid.

Figure 7. General structures of amphiphilic and bolaamphiphilic polyols.

Some general structures of naturally occurring amphiphiles are shown in Scheme 2 [14]. 

Figure 3.5 General structure of amphiphilic modular norbornene derivatives. Reproduced with permission from M. Firat Ilker, Hanna Schule and E. Bryan Coughlin, Macromolecules, 2004, 37, 694.

The term gemini surfactant was coined by Menger inl991. A gemini surfactant may be viewed as a surfactant dimer, i.e. two amphiphilic molecules connected by a spacer. Figure 17.1 shows the general structure. Gemini surfactants are also referred to as twin surfactants , dimeric surfactants or bis-surfactants . 

Figure 19 General structure for designed fluorinated amphiphilic oxadiazoles.

Ezrahi, S., Tuval, E., Aserin, A., and Garti, N. 2005 The effect of structural variation of alcohols on water solubilization in nonionic microemulsions 1. From linear to branched amphiphiles-general considerations, J. ColloidInterf. Sci. 291 263-272. 

The general structure (9) ascribed to the ornithine-containing lipids with two hydrophobic acyl chains and a zwitterionic group shows the amphiphilic character of the molecule. This structure is quite similar to that of phosphatidylethanolamine (Fig. 1). 

In 2004, Deming s laboratory studied the roles of chain length and block composition on the assembly of uncharged diblock copolypeptide amphiphiles of the general structure poly(77e-2-[2-(2-methoxyethoxy)ethoxy]acetyl-L-lysine)-Z loc -poly(L-leucine), or [88]. These diblock copolypeptide amphiphiles... 

General anesthetics are usually small solutes with relatively simple molecular structure. As overviewed before, Meyer and Overton have proposed that the potency of general anesthetics correlates with their solubility in organic solvents (the Meyer-Overton theory) almost a century ago. On the other hand, local anesthetics widely used are positively charged amphiphiles in solution and reversibly block the nerve conduction. We expect that the partition of both general and local anesthetics into lipid bilayer membranes plays a key role in controlling the anesthetic potency. Bilayer interfaces are crucial for the delivery of the anesthetics. 

Recently, many studies have focused on self-assembled biodegradable nanoparticles for biomedical and pharmaceutical applications. Nanoparticles fabricated by the self-assembly of amphiphilic block copolymers or hydrophobically modified polymers have been explored as drug carrier systems. In general, these amphiphilic copolymers consisting of hydrophilic and hydrophobic segments are capable of forming polymeric structures in aqueous solutions via hydrophobic interactions. These self-assembled nanoparticles are composed of an inner core of hydrophobic moieties and an outer shell of hydrophilic groups [35, 36]. 

A special class ofblock copolymers with blocks of very different polarity is known as amphiphilic (Figure 10.1). In general, the word amphiphile is used to describe molecules that stabilize the oil-water interface (e.g., surfactants). To a certain extent, amphiphilic block copolymers allow the generalization of amphi-philicity. This means that molecules can be designed that stabilize not only the oil-water interface but any interface between different materials with different cohesion energies or surface tensions (e.g., water-gas, oil-gas, polymer-metal, or polymer-polymerinterfaces). This approach is straightforward, since the wide variability of the chemical structure of polymers allows fine and specific adjustment of both polymer parts to any particular stabilization problem. 

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