Amphiphilic oligopeptides

Figure 2.7. Aggregated conformations of an amphiphilic oligopeptide, (a) Aggregated antiparallel (i-sheets at pH 4. (b) a-helices aggregating at pH 7.

E. (2007) Self-assembly of recombinant amphiphilic oligopeptides into vesicles. Biomacromolecules, 8, 2753—2761. 

The third type of self-assembling units are peptidomimetics [39-42], in which the amphiphilic oligopeptides are combined with hydrophobic synthetic compounds (Type 111 in Fig. 1). For example, Kelly et al. prepared a dibenzofuran-based simple peptidomimetic and showed that the pep-tidomimetic formed polymorphic -sheet assemblies including protofilaments, filaments, ribbons, and fibrils [39]. On the basis of the TEM, AFM,... 

Oligopeptides in the Monoolein-Water System. Most oligopeptides are amphiphilic molecules, i.e. they have both hydrophilic and lipophilic characteristics,... 

Various comprehensive studies on the polymerization of enantiopure and racemic esters of a-amino acids performed at the air/water interface to yield peptides have been reported over the years [189,190]. Recent reinvestigations of the products of these reactions by MALDI-TOF MS have demonstrated, however, that they are not longer than dipeptides [191]. For this reason, such esters cannot be regarded as realistic prebiotic model systems for the formation of long oligopeptides. On the other hand, amphiphilic Na-carboxyanhydrides [192] and thio-esters [193] of a-amino acids yield longer oligopeptides. 

Recently, the difference in structure and chemical reactivity between 2-D racemic and enantiomorphous crystallites has been used to generate enan-tiopure homochiral oligopeptides from non-racemic mixtures of amphiphilic a-amino acid NCAs. The racemic N"-carboxyanhydridc of y-slcaryl-glutamic acid (Cis-Glu-NCA) self-assembles on water to form racemic 2-D crystallites (Fig. 16a,b), as proved by GIXD. 

Novel polymer-bound oligopeptides exhibiting antimicrobial activity have been developed. The oligopeptides are unique amino acid sequences which form amphiphilic helices. 

Liquid crystalline phases are also of interest from the point of view of controlled or sustained release, or even the absence (e.g. in the case of certain potent enzymes) of such release of bioactive molecules. For example, due to the presence of both water and oil channels in bicontinuous cubic structures, such systems are capable of solubilizing both hydrophilic, hydrophobic and amphiphilic drugs, the release of which can be sustained over extended periods of time. Particularly interesting in this respect is the incorporation of large oligopeptide or macromolecular drugs (e.g. enzymes). For example, Ericsson et al. investigated the incorporation of lysozyme in a cubic phase formed by monoolein and water, and found that a considerable amount could be solubilized in the liquid crystalline phase (182). Furthermore, the incorporation of c -lactalbumin, bovine serum albumin and pepsin was found to resemble that... 

Tubules with hollow cavities through self-assembly of small molecules are a major structural feature of biological systems, as exemplified by tobacco mosaic virus and cytoplasmic micrombules [15,16]. Many studies have focused on the nanostructures through self-assembly of lipid molecules [17], aromatic amphiphiles [18-22] and oligopeptides [23,24] using various non-covalent interactions [25]. Also, the... 

Figure 3.15 Self-assembly of tripodal amphiphiles variation in the hydrophobicity of the oligopeptide can be used to tune the self-assembly properties. Reproduced with permission from Y.J. Jun, M.K. Park, V.B. Jadhav, J.H. Song, S.W. Chae, H.J. Lee, K.S. Park, B. Jeong, J.H. Choy and Y.S. Sohn, Journal of Controlled Release, 2010,142,1,132. 2010, Elsevier [107]...

Fig. 2 A Molecular structure of the amphiphilic triblock-type oligopeptide, LKL16, used as a building unit for self-assembly. B CD spectral change of LKL16 in Tris-bulfer at pH 9.2. The peptide was incubated at room temperature for the time indicated. [LKL16] = 40 (aM...

Fig. 5 A Chemical structure of the amphiphilic diblock-type oligopeptide, LK16, and its molecular dimension in a-helical form. B Tapping-mode AFM image of the self-assembled nanoparticle obtained from LK16. C Proposed model of the nanoparticle from a-helical LK16...

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