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Cell Biology for Bioprocessing
Published in Wei-Shou Hu, Cell Culture Bioprocess Engineering, 2020
Unlike actin filaments and microtubules, which are ubiquitous to all eukaryotic cells, intermediate filaments are only present in some animals, including vertebrates, nematodes, and mollusks (Figure 2.15 and Figure 2.16, Panel 2.29). Although all intermediate filaments share common structural features, they are comprised of many different molecules and their expression is tissue specific. For example, laminins are present in the nucleus, vimentins in many mesenchymal cells, and keratins in epithelial cells. The major role of intermediate filaments is to transmit mechanical force and provide cells with their mechanical characteristics. For example, the intermediate filament keratin gives the outer layer of skin its toughness. While the diverse intermediate filaments are not conserved in their amino acid sequence, they are conserved in major protein domains and share common characteristics in their molecular organization. A common feature of intermediate filaments is that they form a head-to-tail coiled heterodimer, and then a pair of dimers form an antiparallel and symmetrical tetramer. Thus, intermediate filaments fundamentally differ from actin fibers and microtubules in that the latter two are polar with a “+” and a “−” end. Tetramer subunits are stacked together to form a filament. Each intermediate filament fiber is made of multiple fibrils, which are in turn made of a series of subunit proteins.
Computational and Experimental Approaches to Cellular and Subcellular Tracking at the Nanoscale
Published in Sarhan M. Musa, ®, 2018
Zeinab Al-Rekabi, Dominique Tremblay, Kristina Haase, Richard L. Leask, Andrew E. Pelling
These filaments are part of a subfamily of proteins containing more than 50 different members and have an average diameter of ~10nm. The common structure they share is the central a-helical domain, which consists of over 300 residues that form an entangled coil The dimers assemble themselves into a staggered array forming tetramers that connect end-to-end forming protofilaments. These in turn organize into ropelike structures, where each contains eight protofilaments with an average persistence length of about 1μm (Mucke et al. 2004). Intermediate filaments are relatively stable, and they are involved in providing tensile strength for the cell. In addition, they may be involved in specialized cell-cell junctions (Herrmann et al. 2007). For example, lamins, one of the various types of intermediate filaments form filamentous support inside the inner nuclear membrane; therefore, they are vital to the reassembly of the nuclear envelope after cell division (Georgatos and Blobel 1987; Herrmann et al. 2007; see Figure 9.2).
The Cell as an Inspiration in Biomaterial Design
Published in Heather N. Hayenga, Helim Aranda-Espinoza, Biomaterial Mechanics, 2017
Helim Aranda-Espinoza, Katrina Adlerz
The cytoskeleton is largely responsible for the mechanical properties and spatial organization of animal cells (see Figure 5.1). Its roles include changing the shape of the cell, coordinating migration, imparting mechanical resistance to deformation, and cell division. The cytoskeleton is a collection of three main proteins classified by the diameter of their filaments. Semi-flexible actin filaments, the smallest at around 7 nm, are mainly involved in cell migration. Flexible intermediate filaments provide mechanical strength to the cell. Microtubules with a 25 nm diameter are the largest and stiffest filament of the cytoskeleton and are involved in directing intracellular transport and are major components of cilia and flagella [2]. The unique mechanical properties of the different cytoskeletal filaments make each suited for a different type of biomaterial with specific properties and applications. Weak, noncovalent bonds and hydrogen interactions hold together each of the three components of the cytoskeleton, allowing for rapid assembly and disassembly, which in turn allows the cytoskeleton to adapt to external stimuli, another desirable property in biomaterial design.
Regenerated silk fibroin loaded with natural additives: a sustainable approach towards health care
Published in Journal of Biomaterials Science, Polymer Edition, 2023
Niranjana Jaya Prakash, Xungai Wang, Balasubramanian Kandasubramanian
Keratin is one of the fundamental structural fibrous proteins, which is mostly made up of cysteine that contributes 20-7 percent of the overall amino acid residues. Keratin is mostly found in mammals as the outer covering for hair, nails, feathers, and horns. The chemical, thermal and mechanical properties of these fibres are customarily decided by the inter and intramolecular disulfide bonds generated due to the oxidized cysteine units. The family of wool keratin proteins can be broadly categorized into two factions, namely matrix proteins and intermediate filament proteins (IFP) [73]. Among the matrix proteins, they possess either high cysteine residue content, known as high-sulfur proteins (HSPs) or high tyrosine and glycine residue content, called high-glycine/tyrosine proteins (HGTPs) [74]. The dissolved keratin can be used for multiple applications; however, the weak mechanical strength of this material limits its applicability in practical life. Hence the keratin macromolecules are often used in conjunction with some other structural materials and crosslinking agents. The SF- keratin blend in formic acid is one among such composites which are widely reported. Formic acid is generally used here, considering its ability to dissolve keratin wool partially, whereas it dissolves SF and regenerates keratin completely [52].
A human pericardium biopolymeric scaffold for autologous heart valve tissue engineering: cellular and extracellular matrix structure and biomechanical properties in comparison with a normal aortic heart valve
Published in Journal of Biomaterials Science, Polymer Edition, 2018
Frantisek Straka, David Schornik, Jaroslav Masin, Elena Filova, Tomas Mirejovsky, Zuzana Burdikova, Zdenek Svindrych, Hynek Chlup, Lukas Horny, Matej Daniel, Jiri Machac, Jelena Skibová, Jan Pirk, Lucie Bacakova
Immunohistochemical detection of collagen I, III and elastin was performed on paraffin sections 4 μm in thickness, using a two-step indirect method. The slides were deparaffinized in xylene, and were rehydrated in graded ethanol. After deparaffinization and rehydration, endogenous peroxidase was blocked by 0.3% H2O2 in 70% methanol for 30 min. A primary antibody was applied for 30 min at RT, and antibody detection was performed using Histofine Simple Stain MAX PO (MULTI) Universal Immuno-peroxidase Polymer, anti-Mouse and anti-Rabbit (Histofine; Nichirei, Japan). Immunohistochemical detection of vimentin (a type III intermediate filament protein), desmin (a marker of striated muscles), alpha smooth muscle actin (α-SMA), Ki-67 (a nuclear marker for cell proliferation), CD31 (a platelet-endothelial cell adhesion molecule, also referred to as PECAM-1), leukocyte common antigen (LCA) and β-catenin (a cell adhesion protein associated with cadherin junctions linking cadherins to the actin cytoskeleton) were performed on sections of paraffin-embedded tissues 4 μm in thickness, using the Ventana Benchmark Ultra system (Tuscon, AZ, USA) with the ultraView Universal DAB Detection Kit.
Extraction of keratin from unhairing of bovine hide
Published in Chemical Engineering Communications, 2022
Franck da Rosa de Souza, Jaqueline Benvenuti, Michael Meyer, Hauke Wulf, Enno Klüver, Mariliz Gutterres
The keratins are defined as a family of scleroproteins, characterized by the high sulfur content (3%–5%), which is specifically related to cysteine and cystine amino acid residues. They are found in the epidermis layer and in the related appendages, providing mechanical stability and having protective functions (Seifter and Gallop 1966). The hair (in dry basis) is composed of 90%–97% of protein (keratins), 2% of lipids, and the remainder consists of nucleic acid, carbohydrates, and inorganic substances. The chemical composition is around 50% carbon, 22% oxygen, 16% nitrogen, 7% hydrogen, and 5% sulfur (Popescu and Hocker 2007). The hairs are formed by two structures (Wagner and Bailey 1999): the cuticle is the external layer and because of the presence of lipids, it is a hydrophobic in nature; and the cortex, which is the hydrophilic layer inside. The cortex is formed basically by the keratin, packed as α-helix arrangements with high cystine content (Edwards and Routh 1944), assembled in microfibrils (intermediate filament protein, IFP) (Jones et al. 1997), and immersed in a matrix (intermediate filament associated protein, IFAP) (Rogers 1988). Keratin in its α-helix arrangements is the protein that builds up microfibrils. These bigger structures, also called IFP, are locked inside a matrix, which is formed by another class of protein, IFAP. The “A” means that this class of protein is associated to the IFP. The keratins from the matrix contain high sulfur contents, and therefore promote the stability of the structure by introducing crosslinks in the form of disulfide bonds. The range of the IFAP molecular weight is between 10 and 25 kDa. The keratins from intermediate filament (IFP) have a lower content of sulfur and the helical conformation gives support to the structure having molecular weight from 40 to 60 kDa (Rouse and Van Dyke 2010).