Nanotubes, peptide

FIGURE 5.17 TEM micrographs of diphenylalanine peptide nanotubes self-assembled after the enzymatic cleavage, (a) TEM images of 22 prior to the enzymatic cleavage, (b and c) TEM images of 22 after the enzymatic cleavage. 

FIGURE 5.19 Controlled formation of diphenylalanine peptide nanotubes. 

Adler-Abramovich, L. Perry, R. Sagi, A. Gazit, E. Shabat, D. Controlled assembly of peptide nanotubes triggered by enzymatic activation of self-immolative dendrimers. Chem. Biochem. 2007, 8, 859-862. 

Reches, M., and Gazit, E. (2003). Casting metal nanowires within discrete self-assembled peptide nanotubes. Science 300, 625-627. 

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. 

Ghadiri MR, Granja JR, Buehler LK. Artificial transmembrane ion channels from selfassembling peptide nanotubes. Nature (Lond) 1994 369 301-304. 

Reches M, GazitE. Casting metal nanowires within discrete self-assembled peptide nanotubes. 

Reches M, Gazit E (2006) Controlled patterning of aligned self-assembled peptide nanotubes. Nat Nanotechnol 1 195-200... 

Compared to classical drug delivery systems such as liposomes or peptides, nanotubes have a higher efficiency [41] and this can be used for the further development of delivery systems. Stability and diversity of nanotube forms provide long time circulation and biocompatibility that result in more efficient transport of substances. 

Figure 4. IS. Self-assembled peptide nanotube incorporated into a membrane.

Figure 14.15 (a) X-ray structure of a model dimer repeat unit of peptide nanotubes made up from the self-... 

Figure 11.8 Self-assembled cyclic-D,L-a-peptide nanotubes containing NDI as the core, (a) Reversible reduction of the NDIs with sodium dithionate. (b) Self-assembly of the peptide NDI nanotube after reduction reaction via chemical or electrochemical methods.

The self-assembling cyclic D,L-cc-peptide nanotubes described demonstrate high stability on surfaces even after two months exposure to ambient temperature. NDI peptide nanotubes 18 may provide a facile method for the preparation of a new class of synthetic biomaterials [16b, 34a]. Recently Sanders and co-workers demonstrated the formation of amino acid-derived NDI hydrogen-bonded supramo-lecular organic M-helical nanotubes in nonpolar solvents and also in the solid state [34b]. The hydrogen-bonded supramolecular nature of the helical nanotubes was confirmed by the circular dichroism (CD) spectrum in chloroform with the addition of methanol, destruction of the supramolecular nanotubes was observed, due to the capabilities of such an aprotic solvent to compete for hydrogen-bond interactions [34b]. 

Figure 7 Scanning electron microscopy image of vertically aligned diphenylalanine-based peptide nanotubes assembled on a glass surface. The scale bar is 10 lm in length. Reprinted by permission from Macmillan Publishers Ltd., Nature Nanotechnology (Reches and Gazit, 2006), copyright 2006 (http //www.nature.com/nnano/index.html).

Larger patterned surfaces can also be achieved using inkjet printing. This technique has been used to create micron-sized letters of the alphabet containing diphenylalanine peptide nanotubes [tertbutoxycarbonyl-Phe-Phe-OH (Boc-Phe-Phe-OH)] on either transparent foil or indium-tin oxide (Adler-Abramovich and Gazit, 2008) as shown in Figure 13. This later... 

Copper has been immobilized on glycylglycine bolaamphiphile peptide nanotubes that display histidine residues, and paramagnetic gadolinium, a magnetic resonance image contrast agent, has been immobilized on nanofibers produced from peptide amphiphiles (see Gazit, 2007 and references therein). 

The diphenylalanine nanotube sensors were based on the observation that peptide nanotubes improve the electrochemical properties of graphite and gold electrodes when deposited directly onto the electrode surface (Yemini et al., 2005b). The high surface area of the nanotubes and the potential alignment of aromatic residues are thought to contribute to the observed increase in conductivity. This property makes nanotube-coated electrodes and hydrophobin-coated electrodes suitable for use as amperometric biosensors that produce a current in response to an electrical potential across two electrodes. 

Figure 18 Schematic of a glucose biosensor assembled from diphenylalanine peptide nanotubes. The enzyme GOX has been cross-linked to these nanotubes, which are further linked to the gold (Au) electrode and immobilized in a polyethyleneimine (PEI) matrix. The nanofibers act in two ways they immobilize the sensing enzyme and enhance the transducer. Reprinted in part with permission from Yemini et al. (2005a) (copyright 2005 American Chemical Society).

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