Elastin preparation

Variations in Amino Acid Content of Elastin Preparations from Aorta... 

Paper chromatography was used hy Bowes and Kenten (1949) to examine the amino acid composition of elastin preparations from ligamentum nuchae and skin. The results indicated either that the elastic fibers of skin differ from those of ligamentum nvchac in amino acid composition or that they are less resistant to hot water. This interesting suggestion does not appear to have been pursued. 

The final analyses of the three elastin preparations are so similar that it is tempting to regard the proteins as identical and to ascribe the small differences as due to the presence of resistant impurities. That there are real differences between the elastins of different tissues can be shown by an examination of the physical properties of the different products. Slight differences in staining reactions have already been noted, but recent work in this laboratory has shown that there are marked differences in the rate of alkaline hydrolysis between the different samples. Figure 3 shows the... 

With elastin preparations as described above, the classic proteolytic enzymes of the pancreas—trypsin and the chymotrypsins—have little activity and do not produce dissolution of the fibers. In the early literature there are many reports of the dissolution of elastin libers by pan-creatin or by impure preparations of trypsin, but it was not until the work of Balo and Banga (1949) that the existence of a separate elastolytic enzyme in the pancreas was recognized. Soon after this Banga (1952) obtained a purified crystalline enzyme which was thought to be substantially free from nonelastolytic components of the pancreatic system of enzymes. 

Inspired by the elastin-based side-chain polymers, Lemieux et al. prepared elastin-based stimulus-responsive gold nanoparticles. To this end, they capped gold particles with a layer of a single repeat of thiol-functionalized VPGVG peptides (Fig. 17a). These nanoparticles showed LCST behavior, which was modulated by varying the pH of the solution [131]. 

Daamen WF et al (2003) Preparation and evaluation of molecularly-defined collagen-elastin-glycosaminoglycan scaffolds for tissue engineering. Biomaterials 24(22) 4001-4009... 

Elastin-mimetic protein polymers have been fabricated into elastic networks primarily via y-radiation-induced, radical crosslinking of the material in the coacervate state [10]. Although effective, this method cannot produce polymers gels of defined molecular architecture, i.e., specific crosslink position and density, due to the lack of chemoselectivity in radical reactions. In addition, the ionizing radiation employed in this technique can cause material damage, and the reproducibility of specimen preparations may vary between different batches of material. In contrast, the e-amino groups of the lysine residues in polymers based on Lys-25 can be chemically crosslinked under controllable conditions into synthetic protein networks (vide infra). Elastic networks based on Lys-25 should contain crosslinks at well-defined position and density, determined by the sequence of the repeat, in the limit of complete substitution of the amino groups. 

Goissis, G., Suzigan, S., Parreira, D. R., Maniglia, J. V., Braile, D. M., and Raymundo, S. (2000). Preparation and characterization of collagen-elastin matrices from blood vessels intended as small diameter vascular grafts. Artif. Organs 24, 217-223. 

Jensen, S. A., Vrhovski, B., and Weiss, A. S. (2000). Domain 26 of tropoelastin plays a dominant role in association by coacervation./. Biol. Chem. 275, 28449-28454. Kagan, H. M., and Sullivan, K. A. (1982). Lysyl oxidase Preparation and role in elastin biosynthesis. Methods Enzymol. 82, 637-650. 

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

Figure 3. Lysyl oxidase. The enzyme, lysyl oxidase, appears to seek out lysyl residues in alanyl- and lysyl-rich regions in the pro fibrillar forms of elastin. The presence of an aromatic amino acid residue adjacent to lysine appears to block its oxidation. The product of oxidation is peptidyl a-aminoadipic-S-semialdehyde. Assays for the enzyme against elastin involve first the preparation of an elastin-rich pellet containing 3H-lysyl residues labeled in the 6 or 4,5 position. This is usually accomplished by incubating embryonic chick aortas in medium containing 3H-lysine plus f3-aminopropionitrile (BAPN) to inhibit endogenous lysyl oxidase activity. BAPN is then removed leaving behind an elastin-rich residue in which the profibrillar forms of elastin labelled with 3H-lysine are only partially crosslinked. When lysyl oxidase preparations are added to this residue the release of tritium represents the assay for activity. It has also been demonstrated that tropoelastin, when incubated with lysyl oxidase, forms a-aminoadipic-S-semialdehyde and eventually crosslinks as shown in Figure 4.

Enzymes, such as creatine kinase, have been grafted on to collagen films by using water soluble carbodiimides. Porcine intestinal collagen has been crosslinked with EDC in acetone to provide a remodelable scaffold. EDC crosslinking of collagen/elastin matrices is also used to prepare fiat scaffolds. ... 

Probably because of the ease with which they can be prepared, purified fiber preparations from bovine ligamentum nuchae have formed the starting point of most chemical investigations of elastin. These preparations how-... 

In Fig. Ic is seen a preparation made by repeatedly autoclaving material of the tunica media of bovine aorta. The particles of purified elastin were dried, embedded in wax, and then sectioned. The sections were mounted and stained with Verhoeff s hematoxylin. Examination of the sections showed that much of the membranous elastic material had been resolved into flat bundles of fine fibrils, arranged parallel, and in registerlike locks of wavy hair. 

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