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Self-assembling peptides are a category of peptides which undergo spontaneous assembling into ordered nanostructures. These designer peptides have attracted interest in the field of nanotechnology for its potential for application in areas such as biomedical nanotechnology, cell culturing, molecular electronics, and more. Effectively they act as building blocks for a wide range of material and device applications. The essence of this technology is to replicate what nature does: to use molecular recognition processes to form ordered assemblies of building blocks that are capable of conducting biochemical activities. ==Background== Peptides are able to perform as excellent building blocks for a wide range of materials as they can be designed to combine with a range of other building blocks such as lipids, sugars, nucleic acids, metallic nanocrystals and so on; this gives the peptides an edge over carbon nanotubes which are another popular nanomaterial, as the carbon structure is unreactive. They also exhibit properties such as biocompatibility and molecular recognition; the latter is particularly useful as it enables specific selectivity for building ordered nanostructures. Additionally peptides have superb resistance to extreme conditions of high/low temperatures, detergents and denaturants.〔Dinca, V., et al., Directed Three-Dimensional Patterning of Self-Assembled Peptide Fibrils. Nano Letters, 2007. 8(2): p. 538-543.〕 The ability of peptides to perform self-assembly allows them to be used as fabrication tools which is currently and will continue to grow as a fundamental part of nanomaterials production.〔Zhang, S., Building from the bottom up. Materials Today, 2003. 6(5): p. 20-27.〕 The self-assembling of peptides is facilitated through the molecules’ structural and chemical compatibility with each other and the structures formed demonstrates physical and chemical stability.〔 A great advantage of using self-assembling peptides to build nanostructures in a bottom-up approach is that specific features can be incorporated; the peptides can be modified and functionalized. This approach means that the final structures are built from the self-integration of small, simple building blocks. Essentially this approach is needed for nanoscale structure, as the top-down method of miniaturizing device using sophisticated lithography and etching techniques has reached a physical limit. Moreover, the top-down approach is applicable to mainly only silicon based technology, and is unable to be used for biological developments. The peptide structure is organized hierarchically into four levels. The primary structure of a peptide is the sequence of the amino acids on the peptide chain. Amino acids are monomer molecules that carries a carboxyl and an amine functional groups; a spectrum of other chemical groups are attached to different amino acids, such as thiols and alcohols. This facilitates the wide range of chemical interactions and therefore molecular recognitions that peptides are capable of. For designer self-assembling peptides both natural and non-natural amino acids are used. They link together in a controlled manner to form short peptides which links to form long polypeptide chains. Along these chains the alternating amine (NH) and carbonyl (CO) groups are highly polar and they readily form hydrogen bonds with each other. These hydrogen bonds binds peptide chains together to give rise to secondary structures. Stable secondary structures include the alpha-helices and beta-sheets. Unstable secondary structures are random loops, turns and coils that are formed. The secondary structure that is formed is dependent on the primary structure; different sequences of the amino acids exhibit different preferences. Secondary structures usually fold into with a variety of loops and turns into a tertiary structure. What differentiates the secondary structure from the tertiary structure is primarily that the latter includes non-covalent interactions. The quaternary structure is the combination of two or more different chains of polypeptide to form what is known as a protein sub-unit. The self-assembly process of the peptide chains is dynamic—reassembly occurs repeatedly in a self-healing manner.〔 The type of interactions that occurs to reassemble peptide structures include van der Waals forces, ionic bonds, hydrogen bonds and hydrophobic forces.〔 These forces also facilitate the molecular recognition function that the peptides encompasses. These interactions works on a basis of preference dependent on energy properties and specificity. A range of different nanostructures can be formed. Nanotubes are defined as an elongated nano-object with a definite inner hole.〔Scanlon, S. and A. Aggeli, Self-assembling peptide nanotubes. Nano Today. 3(3-4): p. 22-30.〕 Nanofibrils are solid on the inside as opposed to hollow nanotubes. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Self-assembling peptide」の詳細全文を読む スポンサード リンク
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