Dialkyl amphiphiles

Another important area of progress is the enlargement of the scope of the structure of aqueous aggregates. The bilayer membrane formed from dialkyl amphiphiles belongs to a new class of the aqueous aggregate, totally different from the conventional surfactant micelle. A trialkylammonium compound gives yet another type of aggregation. 

As discussed in the preceding sections, fluid, globular micelles are formed from monoalkyl surfactants, whereas the liquid-crystalline bilayer structure is formed from a variety of dialkyl amphiphiles and from single-chain amphiphiles with rigid hydrophobic segments. It may then be asked what structure is expected from amphiphiles with three alkyl chains. 

Chiral dialkyl amphiphiles [61] and [62], prepared from alanine and glutamic acid (Kunitake et al., 1979b), also form bilayer structures when dispersed in water. Chiral bilayers should be interesting because they provide... 

The size of molecular assembly of six synthetic dialkyl amphiphiles as determined by a quasi-elastic light scattering is varied in the presence of nonionic MEGA-n surfactants (N-D-gluco-N-methylalkanamide C = 7-9). 

At high MEGA-n concentration, the size is as small as a MEGA-n micelle itself suggesting that dialkyl amphiphile is solubilized in the nonionic micelle. At low concentration a dialkyl amphiphile vesicle keeps its size relatively constant and takes up MEGA-n molecules. 

Dialysis causes a deficiency in MEGA surfactant which has patched hydrophobic portion of dialkyl amphiphilic molecular assembly. 

Kimizuka, N., Wakiyama, T., Miyauchi, H., Yoshimi, T., Tokuhiro, M., Kunikate, T. (1996). Formation of stable bilayer membranes in binary aqueous-organic media from a dialkyl amphiphile with a highly dipolar head group, J. Am. Chem. Soc., 118 5808. 

MO is the most appropriate azo dye for similar investigations, because it can be included into oH-, /S-, /-cdx monomers (6), and form complexes with peptides (7,8), and with bilayer membranes of chiral dialkyl amphiphiles (9) ... 

We also established the bilayer formation by the following nonionic and zwitterionic dialkyl amphiphiles(8) ... 

Complexes based on the double-helix DNA and oppositely charged surfactants are formed in aqueous solution due to Coulombic attraction between the polyanion chain units and surfactant ions, and they are stabilized by hydro-phobic interaction of nonpolar fragments of the surfactant [4-5]. One can expect that such amphiphilic structure of DNA-surfactant complexes will also promote solubility in low-polarity organic solvents. At present, there is lack of information on the behavior of DNA-surfactant complexes in nonaqueous organic solvents. However, some studies indicate that the complexes based on DNA and cationic dialkyl amphiphiles can be soluble in organic media in the presence of a small amount of water [6]. We... 

This kind of ester acts as a nonionic surfactant if the alkanol groups contain hydrophilic moieties. If only two molecules of alkanoles are added to the phosphoric acid molecule an acid or secondary dialkyl phosphoric acid ester is formed that are an amphiphilic molecule by itself see Eq. (5). 

As an alternative to the Glu and Asp scaffolds, the A-(dialkyl)amide of diglycolic acid has been proposed (13). This is readily prepared by heating equivalent amounts of diglycolic anhydride and, for example, bis(octadecyl)amine in refluxing toluene for 48 hours followed by recrystallization from chloroform (mp 81-82 °C)J178 In a similar mode, polyoxyethylene of selected chain length has been used to prepare dicarboxylic acids which, upon mono-amidation with bis(alkyl)amines, yield lipo moieties (e.g., 14) that are coupled to selected amine groups of peptides to produce the peptide amphiphiles. 179180 ... 

A reactive surfactant shown next (RS) was used as a comonomer in a seeded polymerization. RS was easily adsorbed on seed particles due to their amphiphilicity. If dialkyl fumarate was preabsorbed in the particle, the polymerization proceeded quickly and resulted in the formation of skin layer of RS-fumarate copolymer. Because the vinyl group in RS is an allyl type, RS in aqueous phase hardly polymerizes and no water-soluble homopolymer was formed. The active ester group of RS on the skin layer was used for the preparation of functional microspheres (18). 

Several laboratories have described systems by which synthetic linear peptide chains self-assemble into desirable secondary and tertiary structures. One self-assembly approach has been the creation of a peptide-amphiphile, whereby a peptide head group has the propensity to form a distinct structural element, while a lipophilic tail serves to align the peptide strands and induce secondary and tertiary structure formation, as well as providing a hydrophobic surface for self-association and/or interaction with other surfaces. The preparation of a dialkyl ester tail first involves the acid-catalyzed condensation of H-Glu-OH with the appropriate fatty acid alcohol to form the dialkyl ester of H-Glu-OH a typical example is shown in Scheme 7. The assembly of peptide-amphiphiles with mono- and dialkyl ester tails is shown in Scheme 8. A series of studies have demonstrated that triple-helical and a-helical protein-like molecular architecture is stabilized in the peptide-amphiphile 44,63-65 ... 

Solid-Phase Synthesis of Dialkyl Peptide-Amphiphiles 12 General Procedure 144-66 ... 

Peptide-resin assembly was performed by Fmoc solid-phase methodology. All peptide-amphiphiles were synthesized as C-terminal amides to prevent piperazine-2,5-dione formation. 62 Peptide-resins were characterized by Edman degradation sequence analysis as described previously for embedded (non-covalent) sequencing. 67 Peptide-resins were then lipidated with the appropriate (Cn)2-Glu-C2-OH tail to give the dialkyl peptide-amphiphile-resin. 

All the characteristics expressed in the biological lipids and phospholipids are also expressed in peptide amphiphiles. A variety of alkyl and dialkyl oligoglutamates will be initially discussed as representative of such molecules, which helped in the determination of the structure/assembly relationship (Figure 7.9). The latest advances that demonstrate how using this knowledge, peptide-derived materials were tailored for the construction of functional nanostructures amphiphiles will also be discussed. 

The structure of donor-acceptor porphyrin complexes such as 68 has very recently been modified to make a new family of amphiphilic porphyrin dyes with polar pyridinium acceptor head groups and hydrophobic dialkyl-aniline donors (Figure 1.34). The free porphyrins and... 

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