Functional Peptide Nanostructures

The ultimate goal is to be able not only to develop structurally defined peptide nanostructures, but also to render them functional by incorporating a binding, a reactive, or a catalytic site. The term functional here is used in a very broad sense. In the following lines, we shall illustrate the potential of peptide nanostructures in miscellaneous areas. 

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Fig. 25. The development of lamellar molecular crystals using polypeptides with a repeating sequence. The correct folding of these macromolecules produced by molecular biology gives peptide nanostructures, bearing specific functional groups in a well-defined spatial relationship. (Reproduced with the permission of Ref. 63)...

Moreoever, similar to the dynamic behavior of phospholipid vesicles and other microstructures (Wick et al., 1996), these simplest of peptide nanostructures appear to behave as dynamic entities in water they can fuse, divide, and change shape as a function of time and environmental influence (see Figures 20.4-20.7) (Vauthey et al., 2002 Santoso et al., 2002a,b von Maltzahn et al., 2003). 

Acknowledgements We thank PEPSY-lab at IBG2 for peptide material, and the DFG-Center for Functional Nanostructures (TP E1.2) for supporting the NMR facility. 

Sheets also play an important role in the construction of peptide-based functional nanohbrous materials. /3-sheets are preferred over a-helices as molecular building blocks in the fabrication of artificial nanostructured materials perhaps because of the growing interest in understanding the self-assembly of two types of namral /3-sheet products silk protein and amyloid-Uke /3-sheets. Furthermore, extended /3-sheet conformation is relatively easy to achieve. Indeed, preventing their formation, particularly in high concentration or at high temperature, can be difficult in both synthetic and natural constructs. 

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 utilization of peptide self-assembly additionally allows control of structural parameters and the rational control of functionalities, which are displayed at the nanofiber surface. This makes the presentation of biological signals and thus the introduction of bioactivity feasible. Stupp and coworkers investigated the self-assembly of peptide-amphiphiles (Fig. 4) [87, 115], The resulting worm-like, cylindrical nanostructures consist of a hydrophobic core that is formed by the alkyl... 

In recent years, there has been a lot of research in the utilization of biomolecule-functionalized nanoparticles for the formation of hybrid nanostructures. While much effort was spent on solution systems, there are some examples that exploit the binding specificity of the biomolecules, for example, proteins, peptides, and DNA to assemble nanoparticles on surfaces. 

The bacteriostatic and antibacterial properties are in addition to pH-conditions and the nanostructural entrapping mechanism also related to the surface structure developed of the hydrated biomaterial. The nano-particle/crystal size of hydrates are in the interval 15-40 nm with a nanoporosity size of 1-3 nm. The number of pores per square micrometer is at least 500, preferably > 1000 [9]. The number of nanopores will thus be extremely high, which will affect the possibility of catching and fastening bacteria to the hydrate surface - an analogue to how certain peptides may function as antibacterial material due to a structure with nano-size holes within the structure. This may also provide a long-term antibacterial activity after the initial hydration. 

Due to many attractive properties, peptides are the most conunonly used building blocks and the most comprehensively understood for constructing self-assembled biomaterials. Peptides are reasonably tractable and scalable compared to other moiety for self-assembly and, in terms of biological functionality and flexibility, peptides are highly versatile and facile [3]. In most peptide-based self-assemblies, p-sheet and a-helix are frequently used for assembling nanostructures and, thus, become important basic structures for fabricating self-assembled nanostructures. 

Protein and large polypeptides nsnally possess more functionality facilitating self-assanbly than peptides. A number of natural proteins (including collagen, elastin, silk protein, etc.) that spontaneonsly self-assemble into high-order structures have been widely used in the laboratory to fabricate self-assembled nanostructures for biomedical... 

Lim, Y Lee, M. Nanostructures of P-sheet peptides steps towards bioactive functional materials. J. Mater. Chem., 2008,18, 723-727. 

Self-assembly is used to organize molecules into amazing and complex structures. Small molecular weight molecules can be assembled into structures of varying degrees from dimers and trimers all the way up to and including supramolecular polymers. Simple amphiphiles form micelles and vesicles. Dendrimers, DNA-based materials, peptides, and peptides amphiphiles have been assembled into nanostructured fibrals reminiscent of the extracellular matrix. Obviously, we cannot cover here even a fraction of the creative and functional assembled systems reported. In this section, we highlight selected symmetrical self-assembled systems to illustrate how different... 

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