Nanotubes supramolecular structures

The rational synthesis of peptide-based nanotubes by self-assembling of polypeptides into a supramolecular structure was demonstrated. This self-organization leads to peptide nanotubes, having channels of 0.8 nm in diameter and a few hundred nanometer long (68). The connectivity of the proteins in these nanotubes is provided by weak bonds, like hydrogen bonds. These structures benefit from the relative flexibility of the protein backbone, which does not exist in nanotubes of covalently bonded inorganic compounds. 

Nucleic acids can be conjugated to nano-objects, such as nanoparticles, nanowires, or nanotubes. The resulting nucleic acids-nano-objects hybrids combine the tailored recognition and catalytic properties of the nucleic acids with the electronic, optical, and catalytic features of the nano-objects. The forthcoming chapter will address the organization of nanoscale supramolecular structures of nucleic acids on... 

This chapter has focused on the use of biomolecular supramolecular structures and biomolecule-nanoparticle (or carbon nanotubes) composites as functional units for the construction of electrical devices. 

To summarize, in this chapter we have discussed medium-sized supermolecules with unique shapes. Some of them (fullerenes and carbon nanotubes) are found in nature, while others (dendrimers, rotaxanes and catenanes) can be synthesized via artificial molecular design. As seen from palladium-based molecular capsule formation, spontaneous association can sometimes also provide highly sophisticated supramolecular structures. Indeed, as... 

Single- and multiwalled carbon nanotubes represent attractive components for supramolecular structures. Their rod shape predestines them as guest molecules to be included inside host compounds that are designed like rings or hollow cylinders. From an arrangement with the host wrapped helically around the nano-tube, another type of supramolecular compound arises. The tubes can further serve as scaffold to supramolecular structures that form by a complexation of single tubes or bundles. Several examples of supramolecular patterns have already been discussed in Section 3.5.4.2 on the noncovalent functionalization of nano-tubes. Hence only some other specimens will be presented here. 

Interesting supramolecular structures can furthermore be obtained by the controlled crystallization of polymers hke polyethylene or nylon-6,6 on carbon nanotubes. The latter serve both as template and as nucleus of crystallization. There are in principle three modes of how a polymer crystal might grow on a nanotube surface (a) Phase separation may occur in the course of the crystallization so the initially dispersed carbon nanotubes rea omerate and precipitate, (b) The polymer coils around the individual tubes whose solubility increases in the sequel,... 

For long time a way was sought to achieve a size-selective complexation of carbon nanotubes by generating supramolecular structures. By now it has turned out that at least a partial separation can be achieved by the reaction with cyclodex-... 

Other polysaccharides as well suit the formation of supramolecular structures with carbon nanotubes. For instance, a complex may be formed with schizophyl-lan. This (1-1,3-glucane exists as triple helix and winds around the SWNT accordingly. Functionalizing the termini of the glucane, for example, with ladosides, provides a compound that is soluble in water. Furthermore, it may confer to the product an increased affinity, for example, to lecture. 

Kol N, Adler-Abramovich L, Barlam D, Shneck RZ, Gazit E, Rousso I (2005) Self-assembled peptide nanotubes are uniquely rigid bioinspired supramolecular structures. Nano Lett 5... 

Peptides composed of various coded and noncoded amino acid residues self-assemble to form various types of supramolecular architectures, including supramolecular helices and sheets, nanotubes, nanorods, nanovesicles, and nanofibers. The higher-order self-assembly of supramolecular (3-sheets or supramolecular helices composed of short synthetic acyclic peptides leads to the formation of amyloid-like fibrils. Synthetic cyclic peptides were used in supramolecular chemistry as molecular scaffolding for artificial receptors, so as to host various chiral and achiral ions and other small neutral substrates. Cyclic peptides also self-assemble like their acyclic counterparts to form supramolecular structures, including hollow nanotubes. Self-assembling cyclic peptides can be served as artificial ion channels, and some of them exhibit potential antimicrobial activities against drug-resistant bacteria. 

Lu, L.H., Chen, W, 2010. Biocompatible composite actuator a supramolecular structure consisting of the biopolymer chitosan, carbon nanotubes, and an ionic Uquid. Adv. Mater. 22,3745-3748. 

The rational synthesis of peptide-based nanotubes by self-assembling of polypeptides into a supramolecular structures was demonstrated. This self-organization leads... 

Figure 9.4 Surface properties and size influencing the pathways of CNT internalization. Inserted panel Nanotube bundles (CNT)., functionalized with (macro)molecules (f) with the aid of sonication (US) and/or temperature (T), are dispersed in single nanotubes f-CNT this f-CNT can lead to the formation of supramolecular structure p f-CNT. (al) (CNT). interact with cell membrane and are internalized via phagocytosis (bl) f-CNT enter the cells by diffusion (b2) nanotube dispersion is not stable and nanotubes cluster in solution (nanotube clusters enter the cell by phagocytosis) (cl) p f-CNT enters the cell by ligand-receptor (1) binding (c2) p f-CNT cluster on cell membrane and enter by receptor-mediated endocytosis. CNT Carbon nanotube f-CNT Functionalized CNT.

Very interesting supramolecular structures are known as carbon peapods, and consist of single-walled carbon nanotubes (SWCNTs) filled with fullerenes. After their first detection via high-resolution transmission electron microscopy (HRTEM) as a side product in the production of carbon nanotubes, different methodologies have been developed to produce such new carbon allotropes. The harsh conditions previously used (such as high temperatures, low pressures, and acidic medias) have been later overcome by mild condition experiments that exploited not completely understood mechanisms of nano-condensation and nanoextraction. ... 

PLDL did not have covalent characteristics. It may suggest that in these nanocomposite samples the carbon nanotubes are located between the polymer chains and probably have an influence on the supramolecular structure of polylactide during solidification as a result of the interaction of secondary bonding. 

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