Elastin composition

For example, there are several reports that indicate many of the previously reported changes in elastin composition during atherosclerosis are related to the methods used in the initial isolation of the elastins (52,53). Although in certain forms of emphysema there appears to be evidence that elastic fibers are destroyed, the data related to compositional changes and alter-... 

In an effort to determine which spectral changes in the coronary sections were associated with Cl and C3 and elastin composition changes, a set of sample mixtures of Cl, C3, and elastin was prepared using pure lyophilized standards (see Figure 34.11). A triangular array of compositions... 

Chemical Composition. From the point of view of leathermaking, hides consist of four broad classes of proteins coUagen, elastin, albumen, and keratin (3). The fats are triglycerides and mixed esters. The hides as received in a taimery contain water and a curing agent. Salt-cured cattie hides contain 40—50% water and 10—20% ordinary salt, NaCl. Surface dirt is usuaUy about 2—5 wt %. Cattie hides have 5—15% fats depending on the breed and source. The balance of the hide is protein (1). 

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). 

The fibrous protein elastin found extensively in connective tissues is unlike collagen in that it occurs in a less well ordered fashion, furthermore, there are quite marked differences seen between the chemical compositions of collagen and elastin. Whereas collagen comprises a very limited number of different amino acids, elastin contains a wider variety, the most abundant being glycine (approximately 30% dry weight), alanine (23%) valine (15%) and proline (12%). 

Rovira, A., Amedee, J., Bareille, R., and Rabaud, M. (1996). Colonization of a calcium phosphate/elastin-solubilized peptide-collagen composite material by human osteoblasts. Biomaterials 17, 1535-1540. 

We now well appreciate, of course, that polymers are virtually everywhere. Some of them occur naturally, and we continue to better understand their compositions, structures, and properties. Many of these materials have been used since the dawn of human existence, for food, obviously. Cellulose alone has been essential for clothing, fire, shelter, tools, weapons, writing, and art. Leather is probably the result of the first synthetic polymer reaction, essentially the crosslinking of protein (elastin). How we progressed over time to the Polymer Age is a fascinating series of stories, some of which are well worth recounting here. 

AMINO ACID COMPOSITION (EXPRESSED AS RESIDUES PER 1000 TOTAL RESIDUES) OF TYPICAL MATURE ELASTIN, MATRIX COLLAGEN AND MICROFIBRILLAR PROTEIN PREPARATIONS. 

The exact form in which non-crosslinked elastin is secreted from smooth muscle cells is yet to be clearly defined. Foster et al. (36) have suggested that a non-cross linked elastin (pro-elastin) is secreted from smooth muscle cells in a form that is approximately 120,000 to 140,000 daltons. They have suggested that proelastin is cleaved to smaller molecular weight forms of non-crosslinked elastin. It should be noted, however, that this view is not entirely supported by data from other laboratories. There are two reports on the use of isolated mRNA from chick aorta suggesting only a 70,000 dalton non-cross linked elastin is the major product of translation (37,38). There is also a recent report suggesting that aortic mRMA translates a 200,000 dalton putative elastin product (39). We have recently isolated a non-crosslinked elastin from the aortas of copper deficient chicks that appears to be 100,000 daltons (27). Its amino acid composition is similar to that for tropoelastin (Table III). A major problem in resolving these points is that the trypsin-like proteinase associated with elastin is not easily denatured or separated from the non-crosslinked forms of elastin. The proteinase is also not readily inhibited by commonly used inhibitors for trypsin-like proteinases (26). 

AMINO ACID COMPOSITION OF TROPOELASTIN AND A PUTATIVE TROPO-ELASTIN PRECURSOR (EXPRESSED AS MOLES PER 1000 MOLES OF AMINO ACID RESIDUE). 

The most ready source of elastin of high purity is the ligamentum nuchae of the larger ruminants, and from this source a protein of constant composition can be isolated by a variety of methods depending on the solubilization and removal of other less inert tissue components. Because of the ease with which it may be isolated the elastin of bovine ligamentum nuchae has come to be regarded as the type standard, but it is by no means certain that elastins from other mammals or other tissues in the same mammal are of identical constitution. 

No systematic survey of the amino acid composition of mammalian elastins has yet been reported, but from the information available it ap-... 

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