Amyloid supramolecular assemblies

To obtain further insight into the structure and heterogeneity of amyloid fibrils, direct observation of individual fibrils is important. Here we describe a unique approach we developed to monitor fibril growth in real time at the single fibril level [13-17]. On the basis of the observed dramatic diversity and underlying structural basis, we classify amyloid supramolecular assemblies [18],... 

Gilead, S., and Gazit, E. (2005). Self-organization of short peptide fragments From amyloid fibrils to nanoscale supramolecular assemblies. Supramol. Chem. 17, 87-92. 

On the basis of the various amyloid supramolecular fibrillar assemblies of AP(l-40) fibrils produced dependent on and independently of seeds, there are three basic types of amyloid supramolecular fibrillar assemblies (Fig. 15.5). 

Inoue et al. (2003) found that silk proteins will form rodlike structures and that those structure will assemble into comblike or fabric-like superstructure. The scale differences between the rods (nanometers) and the superstructure (micrometers) would suggest that the rod formation is governed by amyloid fibril formation and that the supramolecular arrangement is governed by the properties of the rod (Oroudjev et al., 2002 Putthanarat et al., 2000), namely surface interaction and hydration. Three levels of association could be considered (i) within the proteins internal /1-strands will organize to form intra /1-sheet structures, (ii) /1-sheets from neighboring molecules will associate to form fibril subunits, and (iii) the fibril subunits will further associate to form larger fibrils or rods. 

Maji, S. K., Haidar, D., Drew, M. G. B., Banerjee, A., Das, A. K., and Banerjee, A. (2004). Self-assembly of /1-turn forming synthetic tripeptides into supramolecular //-sheets and amyloid-like fibrils in the solid state. Tetrahedron 60, 3251-3259. 

Das AK, Banerjee A, Drew MGB, Haidar D, Baneijee A. Stepwise self-assembly of a tripeptide from molecular dimers to supramolecular /8-sheets in crystals and amyloid-like fibrlis in the solid state. Supramol Chem 2004 16 331-335. 

There is a range of biological self-assembled polymer fibres such as amyloids, actins and fibrin that have important positive and negative roles in biochemistry. These biopolymers act as an inspiration for supramolecular design and share many features in common with their abiotic analogues. We will mention them briefly here in the context of supramolecular polymers. 

Paul van der Schoot, Nucleation and Co-Operativity in Supramolecular Polymers Michael J. McPherson, Kier James, Stuart Kyle, Stephen Parsons, and Jessica Riley, Recombinant Production of Self-Assembling Peptides Boxun Leng, Lei Huang, and Zhengzhong Shao, Inspiration from Natural Silks and Their Proteins Sally L. Gras, Surface- and Solution-Based Assembly of Amyloid Fibrils for Biomedical and Nanotechnology Applications... 

Fig. 15.5. Schematic models of supramolecular fibrillar assemblies of Afi(l-40) fibrils. Variation in morphology can arise at the level of oligomeric species, protofilaments, or initial short fibrils. They associate together on the quartz surface, creating three types of supramolecular fibrillar assemblies Straight fibrils (Type I), spherulitic assemblies (Type II), and worm-like fibrils (Type III). A mixed architecture of type I and fibrils (Type I/II) was also observed when the internal density is coarse. It is to be noted that the different precursors are represented together in a box and that the relationships between amyloid precursors and final products remain unclear. Reproduced from [18] with permission...

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. 

The biological and biomedical applications of graphene and its derivatives are currently of great interest and have been reviewed in de-tail. Li and Mezzenga have recently reviewed the interaction of amyloid fibrils with carbon nanomaterials such as graphene, extending the scope of biomedical applications and composite biomaterials, indeed, the supramolecular self-assembly of carbonaceous nanomaterials by biomolecules is now a possibility. ... 

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