Nanotubes, peptide-polymer

Couet J, Jeyaprakash JD, Samuel S, Kopyshev A, Santer S et al (2005) Peptide-polymer hybrid nanotubes. Angew Chem Int Ed 44 3297-3301... 

Couet J, Biesalski M (2008) Polymer-wrapped peptide nanotubes peptide-grafted polymer mass impacts length and diameter. Small 4 1008-1016... 

Another approach for fabricating the peptide-polymer hybrid nanofibers is the polymerization method at the surface of self-assembled /3-sheet nanofibers (or nanotubes). In the jd-sheet structure, adjacent /3-strands align... 

Atom transfer radical polymerization (ATRP) is also an interesting strategy to construct peptide-polymer hybrid ID-arrays. Graft-polymerization of AT-isopropylacrylamide was carried out from the surface of self-assembled peptide nanotube in water, and as a result, cyclicpeptide-poly(f -isopropyl-acrylamide) hybrid nanotube was successfully prepared (Fig. 19) [61]. fii other words, this research indicates that surface chemistry of ID-peptide nano-assembly can be adjusted by the grafted synthetic polymers, such as thermo-sensitive PNIPAM and polyelectrolytes. 

Fig. 19 Schematic outline of the synthesis of peptide-polymer hybrid nanostructure. A cyclicpeptide with ATRP initiators self-assembles to form a peptide nanotube through /S-sheet formation. A subsequent surface-initiated ATRP of NIPAM monomer coats the peptide nanotube by PNIPAM-shell. (Adapted from [61])...

Protein structures are so diverse that it is sometimes difficult to assign them unambiguously to particular structural classes. Such borderline cases are, in fact, useful in that they mandate precise definition of the structural classes. In the present context, several proteins have been called //-helical although, in a strict sense, they do not fit the definitions of //-helices or //-solenoids. For example, Perutz et al. (2002) proposed a water-filled nanotube model for amyloid fibrils formed as polymers of the Asp2Glni5Lys2 peptide. This model has been called //-helical (Kishimoto et al., 2004 Merlino et al., 2006), but it differs from known //-helices in that (i) it has circular coils formed by uniform deformation of the peptide //-conformation with no turns or linear //-strands, as are usually observed in //-solenoids and (ii) it envisages a tubular structure with a water-filled axial lumen instead of the water-excluding core with tightly packed side chains that is characteristic of //-solenoids. 

A similar approach was followed by Couet et al. [69] who fimctionahzed peptide Ghadiri rings on 3 sites with ATRP initiators, which were subsequently used for the polymerization of N-isopropyl acrylamide. These hybrid polymer peptide structures were capable of forming peptide nanotubes, which were homogeneously covered by the attached polymer. 

Figure 8 Synthesis of polymer-coated peptide nanotubes using an ATRP bio-macroinitiator approach. Reprinted with permission from Couet, J. Jeyaprakash, J. D. Samuel, S. etal. Angew. Chem., Int. Ed. 2005, 44, 3297. Copyright 2005, Wiley VCH. ...

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