Fibrous proteins, structure

Pauling and Corey Provided the Foundation for Our Understanding of Fibrous Protein Structures... 

In the analysis of fibrous protein structures little mention was made of the importance of their interaction with water in determining the final folded structures of the proteins. This is because most of the side chains in fibrous proteins are exposed to water except when they interact with each other to form multimolecular aggregates. Then the relative affinity between other similar side chains and water becomes a major issue. In the case of globular proteins the interaction of amino acid side chains with water is a major issue from the start because globular proteins have many of their amino acid side chains buried in the interior of their folded structures. Hence, in our analysis of the structure of globular proteins we must be aware of the structural considerations that are important in the determination of fibrous proteins but also of additional considerations, first raised in chapter 1, that relate to the interaction of the amino acid side chains with water. 

Cohen, C., and Vibert, P. J. (1987). Actin filaments Images and models. In Fibrous Protein Structure (J. M. Squire and P. J. Vibert, Eds.). Academic Press, New York. 

In this section, the potential application for amyloid fibrils and other selfassembling fibrous protein structures are outlined. These include potential uses in electronics and photonics presented in Section 4.1, uses as platforms for the immobilization of enzymes and biosensors presented in Section 4.2, and uses as biocompatible materials presented in Section 4.3. Each of these applications makes use of the ability of polypeptides to self-assemble and form nanostructured materials, a process that can occur under aqueous conditions. These applications also seek to exploit the favorable properties of fibrils such as strength and durability, the ability to arrange ligands on a nanoscale, and their potential biocompatibility arising from the natural materials used for assembly. 

A range of functionalized and unfunctionalized self-assembling fibrous structures have been tested for their biocompatibility and ability to provide cells with a favorable micro- and nanoenvironments for soft tissue engineering. In this section, studies that focus on amyloid fibrils, on peptide amphi-philes, on ionic complementary peptides, and on dipeptide structures are reviewed. Hard tissue engineering, composites, and coating are also explored followed by macroscopic structures and networks that can be created from fibrous protein structures. 

Fibrous protein structure investigations applying X-ray diffraction and electron microscopy were reviewed by Blakely (31). Keratin fibers are made of three main structural components the cuticle, the cortex, and the medulla. The medulla is only present in coarse fibers. The cortex forms the bulk of the fiber. Various morphological models have been proposed to explain the mechanical properties of keratin fibers. It is generally agreed that the cortex consists of fibrils in which protein molecules exist in helical and nonhelical regions. 

Silk contains another type of fibrous protein structure, called a p-sheef conformation because of the rippled or pleated structure of these molecules. The polypeptide chains of the extended cods are bound together laterally by disulfide covalent bonds and hydrogen bonds, which connect the peptide bonds of different chains instead of connecting dif-... 

Fraser, R. D. B. The interpretation of infrared dichroism in fibrous protein structures J. Chem. Phys. 21, 1511 (1953). 

Fibrous Proteins Structural Materials of Cells and Tissues (Table 6.2)... 

Squire, J. M., Vibert, R J. (1987). Fibrous Protein Structure, Academic Press, London. 

Amyloid deposits are fibrous protein structures of high P-sheet content that are identified microscopically from their staining characteristics, giving a green birefringence when stained with the dye Congo red. 

The conformation of fibrous proteins has been studied by Infrared dichroism. Thus rat tall tendons, porcupine quills, silk fibre etc. have been studied. In these proteins the absorptions at 1640 cm" and 3300 cm" are maximum when the electric vector of Infrared li t is perpendicular to the fibre axis. These two frequencies are for C=0 and N—H stretching respectively. This observation can only be interpreted one way - these two bonds in the peptide backbone must be oriented perpendicular to the fibre axis (Figiu 8.25). This inference is backed up by other studies on fibrous protein structure as well. 

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