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Self-assembled Peptide Nanostructures and Their Applications
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2020
The formation of amyloid fibril is due to the aggregation of proteins in biological systems. Amyloid fibrils are commonly seen in several diseases like Alzheimer’s disease and Parkinson’s diseases (Harper and Lansbury 1997, Wickner et al. 2000, Sunde and Blake 1998, Gazit 2002b, Reches et al. 2002). In different diseases, many proteins without having any structural and functional homology also form amyloid-like fibrils with similar properties. The large, highly ordered, organized amyloid fibrils formed by proteins exhibited a diameter of 7–10 nm and an X-ray diffraction pattern with 4.6–4.8 Å on the meridian (Gilead and Gazit 2005). In general, the formation of amyloid fibrils occurred in long chain polypeptides having greater than 30 amino acids residues. These fibrils are formed via β-sheet conformation. Not only the long chain polypeptides, short tetra-, penta- and hexapeptides also form similar amyloid-like fibrillar nanostructures with similar biophysical and structural properties like the nanofibrils that are formed by larger polypeptides. Tenidis et al. reported fibrillar-like structures with short pentapeptide FGAIL and hexapeptide NFGAIL that are very similar to the fibrillar structures formed by islet amyloid polypeptide (IAPP) (Tenidis et al. 2000). This IAPP is a 37 amino acid containing polypeptide hormone that is responsible for type II diabetes.
Natural Materials – Composition and Combinations
Published in Graham A. Ormondroyd, Angela F. Morris, Designing with Natural Materials, 2018
The tropocollagen helix length is approximately 300 nm, and in fibrillar collagens, these are organised into arrays, with staggered gaps which create bands that are visible on the collagen fibrils under transmission electron spectroscopy. The tropocollagen chains are aligned with a stagger of approximately 67 mm, or one d-period (Figure 3.12c, Orgel et al. 2011, Sherman et al. 2015). Within this stagger, there is a gap (36 mm, or 0.54 d) between the end of one molecule and the start of the next, and an overlap of 31 mm (or 0.46 d) between the fibril and its nearest neighbour. Smith (1968) proposed a collagen filament of five chains cross section with one d-period as the stagger, as an arrangement to maximise the number of quarter staggered tropocollagen chains. This has been observed by Orgel et al. (2006), who also noted the right-handed helix of these fibrils, within which the tropocolagen helical structure was also discerned. The resultant collagen fibrils are micrometers to tens of micrometers long (Figure 3.12d,e). Fibrils are frequently aligned preferentially to provide strength, for example longitudinally in tendon and in antler tissue.
Modeling of Reversible Protein Conjugation on Nanoscale Surface
Published in Sarhan M. Musa, ®, 2018
An initial stage of fibrillogenesis involving the soluble Aβ complex (Step 1 in Figure 11.2) is regarded as a pathologically important step and a key onset for the subsequent aggregation of the protein [28–30].As these precursors of the fibril are thought to be non-fibrillar soluble oligomer forms of Aβ, they possess neurotoxic properties and play a role in the molecular pathogenesis of Alzheimer’s disease [28]. Although still relatively little is known about the structure of this soluble oligomer Aβ, a selective detection of the oligomer form of Aβ aggregate will be an important step in conducting a study of determining its neurotoxicity and clarifying its role in fibrillogenesis. A direct detection of the reversible process associated with conformation in an oligomer has not yet been fully achieved.
A computational study of mechanical properties of collagen-based bio-composites
Published in International Biomechanics, 2020
Collagen is a fundamental part of biological tissues such as bone, tendon, muscle, and skin (Fratzl 2008). A hierarchical structure is a primary characteristic of collagen-based bio-composites (Currey 2002; Fratzl 2008). At the nanoscale, collagen in bone is mainly bundles of fibrils embedded in an extrafibrillar mineral matrix. The fibrils are a composite of primarily type I collagen protein, intrafibrillar mineral, and water. The collagen molecules are arranged in a periodic triclinic structure (Wess et al. 1995; Orgel et al. 2006), forming regions where there are gaps and overlaps between collagen molecules. The combined length of a single gap and overlap region forms what is known as D-banding, where D is approximately 67 nm (Nikolov and Raabe 2008; Streeter and de Leeuw 2010). The brittle mineral phase is primarily hydroxyapatite (HAP), and experiments have shown that fibril mineralization initially begins in the gap region (Nudelman et al. 2010; Wang et al. 2012). Water fills the remaining fibril voids and can be either mobile water typically found in pore channels, or structural water found between collagen and mineral molecules. (Timmins and Wall 1977; Nyman et al. 2006; Zhang et al. 2007; Gul-E-Noor et al. 2015).
Reaction rate theory for supramolecular kinetics: application to protein aggregation
Published in Molecular Physics, 2018
Thomas C. T. Michaels, Lucie X. Liu, Samo Curk, Peter G. Bolhuis, Anđela Šarić, Tuomas P. J. Knowles
Amyloid fibril formation is a process in which soluble proteins spontaneously aggregate into fibrils of a cross- structure, enriched in -sheet content [20]. This is a complex phenomenon that typically involves the concomitant action of multiple molecular mechanisms. Recent advances in the available experimental techniques for measuring aggregation kinetics coupled to mathematical analysis of the underlying kinetic equations have allowed the identification of these mechanisms at a microscopic level [21–23]. In the case of the aggregation of A42 (the 42-residue form of the amyloid- peptide), a process that is intimately linked to Alzheimer's disease [24], the fundamental steps that underlie amyloid fibril formation involve an initial primary nucleation step, where monomeric proteins spontaneously come together to form new fibrils, coupled to filament elongation. In addition, the aggregation process is accelerated by the fact that fibrils are able to generate copies of themselves through surface catalysis [25,26], a process known as secondary nucleation [27].
Development of biomimetic electrospun polymeric biomaterials for bone tissue engineering. A review
Published in Journal of Biomaterials Science, Polymer Edition, 2019
Sugandha Chahal, Anuj Kumar, Fathima Shahitha Jahir Hussian
Collagens are the fibrous protein and major structural building block components in the ECM of all animals, including invertebrates, sponges and vertebrates. The collagen fibrils provide mechanical strength to maintain the integrity for each connective tissue [99] as shown in Figure 10, the chemical structure and microscopic arrangements of fibrils.