Elastin properties

Siegel, R. C., Pinnell, S. R., and Martin, G. R. (1970) Cross-linking of collagen and elastin Properties of lysyl oxidase. Biochemistry 9 4486. 

A star copolymer (SCP) of PCLA was synthesized by Younes and coworkers. This kind of SCP PCLA elastomer was also synthesized in two steps. First, the small molecular SCP was produced by ring-opening polymerization of s-caprolactone (s-CL) with glycerol as initiator and stannous 2-ethyUiexanoate as catalyst. Second, the living SCP was further reacted with different ratios of a cross-linking monomer, such as 2,2-bis(s-CL-4-yl)-propane (BCP) and s-CL. The SCP elastomers had very low glass transition temperature (—32°C). It was reported that the SCPs were soft and weak with physical properties similar to those of natural bioelastomers such as elastin. A logarithmic decrease in each tensile property with time was observed in this SCP PCLA. 

The first elastomeric protein is elastin, this structural protein is one of the main components of the extracellular matrix, which provides stmctural integrity to the tissues and organs of the body. This highly crosslinked and therefore insoluble protein is the essential element of elastic fibers, which induce elasticity to tissue of lung, skin, and arteries. In these fibers, elastin forms the internal core, which is interspersed with microfibrils [1,2]. Not only this biopolymer but also its precursor material, tropoelastin, have inspired materials scientists for many years. The most interesting characteristic of the precursor is its ability to self-assemble under physiological conditions, thereby demonstrating a lower critical solution temperature (LCST) behavior. This specific property has led to the development of a new class of synthetic polypeptides that mimic elastin in its composition and are therefore also known as elastin-like polypeptides (ELPs). 

This chapter will discuss the basic aspects of elastin and resilin and will address their biological role, biochemical processing, and properties. The materials inspired by elastin and resilin, such as elastin-like polypeptides and resilin-like polypeptides, and applications thereof, will also be covered. 

Research into elastin, its properties, and the fiber formation was for a considerable period of time hindered due to its insolubihty. However, discovery of the soluble tropoelastin precursor made new investigations possible. The tropoelastin protein can be isolated from copper-deficient animals. However, this is a very animal-unfriendly and low yielding process [2]. Therefore, it is preferred to obtain tropoelastin from overexpression in microbial hosts such as Escherichia coli (E. coli). Most studies are thus based on tropoelastin obtained via bacterial production. 

Resilin and elastin, unlike other structural proteins, fulfill both definitions of an elastic material. Colloquially speaking, resilin and elastin are stretchy or flexible. They also fulfill the strict definition of an elastic material, i.e., the ability to deform in proportion to the magnitude of an applied stress without a loss of energy, and the recovery of the material to its original state when that stress is removed. Resilin and elastin are alone in the category of structural proteins (e.g., collagen, silk, etc.) in that they have the correct blend of physical properties that allow the proteins to fulfill both definitions of elasticity. Both proteins have high extensibility and combine that property with remarkable resilience [208]. 

Elastin is a structural protein with outstanding properties, and therefore it has inspired many investigations, with special interest in its elastomeric properties. This behavior can be mimicked with ELPs and these have found wide application in... 

Nettles DL, Haider MA, Chilkoti A et al (2010) Neural network analysis identifies scaffold properties necessary for in vitro chondrogenesis in elastin-like polypeptide biopolymer scaffolds. Tissue Eng A 16 11-20... 

The pleural tissue is a typical connective tissue that consists mostly of matrix the fibrous proteins (collagen, elastin), and mucopolysaccharides, and a few scattered mesothelial cells, capillaries, venules, and ducts. Anatomists have defined several layers (Fig. 3.4) for each of the pleura. Layers 3 and 5 in Fig. 3.4 contain an abundance of fibrous protein, especially elastin. Both the interstitial (Layer 4) and mesothelial (1 and 2) layers contain capillaries of the vascular system and lymphatic channels. The matrix (ground substance) gives the pleura structural integrity and is responsible for its mechanical properties such as elasticity and distensibility. 

Collagens (see p. 344), of which there are at least 19 different varieties, form fibers, fibrils, networks, and ligaments. Their characteristic properties are tensile strength and flexibility. Elastin is a fiber protein with a high degree of elasticity. 

This enzyme catalyzes the hydrolysis of proteins, including elastin, with preferential cleavage at Ala-Xaa. The following are reviews on the molecular and physical properties of this enzyme [EC 3.4.21.36 (pancreatic) and EC 3.4.21.37 (leukocyte)]. 

Many tissues, such as lung, blood vessels, and skin, require elasticity for proper function this property is fulfilled by the matrix elastic fibers, which are composed of the proteins elastin and fibrillin. 

Urry DW, Luan CH, Harris CM, Parker TM. Protein-based materials with a profound range of properties and applications the elastin DTt hydrophobic paradigm. Prot Based Mater 1997 133-177. 

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