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Protein-based Wood Adhesives Current Trends of Preparation and Application
Published in Zhongqi He, Bio-based Wood Adhesives, 2017
Birendra B. Adhikari, Pooran Appadu, Michael Chae, David C. Bressler
A fundamental feature of all biological materials is that they are composed of basic molecular building blocks that are linked together to form a variety of large, complex structures. In proteins, the building blocks, known as amino acids, are linked together by peptide bonds to form a linear polypeptide chain (Fig. 1). The polypeptide chains can differ dramatically in chain length and structural complexity, ranging from simple dipeptides and oligopeptides to the largest known protein, titin, which consists of over 38,000 amino acid residues (Kruger and Linke, 2011). Although polypeptides and proteins are extremely diverse, they are all made of the same pool of twenty amino acids. Proteins can assume complex threedimensional shapes, which are generally integral to the functions that they perform. The diversity in structure and function of proteins is due to the differences in number, type, and particular order of constituent amino acids in polypeptide chains (Cozzone, 2010). These attributes define the primary structure of proteins.
Principles of Chemistry
Published in Arthur T. Johnson, Biology for Engineers, 2019
Proteins are very diverse and complex. The intestinal bacterium Escherichia coli contains about 2400 different proteins, with an average length of 320 amino acids (King et al., 2002). The simple nematode Caenorhabditis elegans has 14,261 different proteins, ranging from 40 to 2,000 amino acids long. Human beings are estimated to have 30,000 genes, each coding for a different protein. The muscle protein titin is one of the longest of these proteins, containing 10,000 amino acids.
Urinary N-terminal fragment of titin: A surrogate marker of serum creatine kinase activity after exercise-induced severe muscle damage
Published in Journal of Sports Sciences, 2021
Yoko Tanabe, Kazuhiro Shimizu, Hiroyuki Sagayama, Naoto Fujii, Hideyuki Takahashi
Titin, a potential non-invasive marker of muscle damage, is a scaffolding protein in striated muscles, with a molecular weight ranging from 3,000 to 3,700 kDa (Wang et al., 1979). This protein exists between the Z-disk and M-line of sarcomeres and plays a major role in muscle stretching and elasticity (Kruger & Linke, 2009). When muscles are damaged, as in muscular dystrophy, the N-terminal fragment of titin is cleaved by the calpain-3 protease found in the muscles. Thereafter, the N-terminal fragment of titin in the skeletal muscle interstitial space moves to the bloodstream through vascular endothelial and smooth muscle cells due to elevated cell membrane permeability, and is subsequently excreted through urine by glomerular filtration (Maruyama et al., 2016). Urinary N-terminal fragment of titin (U-titin), which has a molecular weight of approximately 27 kDa (Rouillon et al., 2014), may assess the magnitude of muscle damage under pathophysiological conditions, including muscular dystrophy (Yoshihisa et al., 2018). If so, the response patterns of U-titin concentration may be similar to those of serum CK activity, following exercise-induced muscle damage.
Cross-bridge mechanism of residual force enhancement after stretching in a skeletal muscle
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2018
Residual force enhancement has frequently been explained using sarcomere length non-uniformity theory (Morgan 1990; Edman and Tsuchiya, 1996; Edman 2012). This theory considers serially arranged sarcomeres to be unstable on the descending limb of the force–length relationship; the competition between the active forces in lightly stretched parts of a muscle and the greater passive force in overstretched parts of a muscle results in residual force enhancement. Another mechanism that has been proposed is based on the engagement of the structural protein titin when a muscle is activated (Herzog and Leonard 2002; Rode et al. 2009; Rassier 2012; Nocella et al. 2014; Herzog et al. 2015; Schappacher-Tilp et al. 2015); specifically, the stiffness of titin increases when a muscle undergoes active stretching rather than passive stretching. These ideas can be added to cross-bridge theory (Huxley 1957; Huxley and Simmons 1971) to account for residual force enhancement of a muscle after active lengthening.