Elastin, native

Coacervation occurs in tropoelastin solutions and is a precursor event in the assembly of elastin nanofibrils [42]. This phenomenon is thought to be mainly due to the interaction between hydro-phobic domains of tropoelastin. In scanning electron microscopy (SEM) picmres, nanofibril stmc-tures are visible in coacervate solutions of elastin-based peptides [37,43]. Indeed, Wright et al. [44] describe the self-association characteristics of multidomain proteins containing near-identical peptide repeat motifs. They suggest that this form of self-assembly occurs via specific intermolecular association, based on the repetition of identical or near-identical amino acid sequences. This specificity is consistent with the principle that ordered molecular assembhes are usually more stable than disordered ones, and with the idea that native-like interactions may be generally more favorable than nonnative ones in protein aggregates. 

Pometun, M.S., Chekmenev, E.Y., and Wittebort, R.J., Quantitative observation of backbone disorder in native elastin, J. Biol. Chem., 279, 7982-7987, 2004. 

Native elastin is an insoluble, highly cross-linked protein. The chemistry, properties and structure of elastin have been frequently reviewed in the past330-333. In this context, aspects of calcification processes will be discussed. 

Abstract The utility of confocal Raman microscopy to study biological events in skin is demonstrated with three examples, (i) monitoring the spatial and structural differences between native and cultured skin, (ii) tracking the permeation and biochemical transformation in skin of a Vitamin E derivative and (iii) tracking the spatial distribution of three major skin proteins (keratin, collagen, and elastin) during wound healing in an explant skin model. 

Little recent work has been reported on the water relations and sw elling properties either of native elastin or elastin that has been isolated by various procedures or treated with enzymes or hydrolytic reagents. This is to be deplored since the study of the hydration of a protein fiber is often a sensitive means of revealing the pattern of lateral bonds which lends structural stability. A comparison of the hydration of elastins derived from different animals, or different tissues of the same animal, would be particularly valuable since the methods are relatively insensitive to the preseruic... 

From the foregoing it appears that autoclaved elastin may in fact be rather more inert than is normal to the native fiber, but on the other hand,... 

Human elastase-1 (EC 3.4.21.36 no systematic name El) is an anionic protease belonging to the family of serine proteases. It is a carboxyendopeptidase that catalyzes hydrolysis of native elastin, the major structural fibrous protein in connective tissue, with a special affinity for the carboxyl group of alanine, valine, and leucine. 

Samples of native ox ligamentum nuchae elastin and of collagen-free elastin were obtained as reported previously (19). 

Figure 1. Temperature dependencies of the density and specific volume of dry elastin (O) native (%) purified.

The temperature dependence of the density of dry samples of native and purified elastin is shovm in Figure 1. In the temperature range explored, the native protein shows a higher density than the purified one, typical values being 1.245 g/ml and 1.232 g/ml, respectively, at 25 C. In a first approximation, this difference in density can be accounted for by the different composition of the native and purified protein. If native elastin is considered a two phase composite material (approximately 80% elastin and 20% collagen), disregarding other minor components whose density data are not available, the density of the composite can be calculated from the equation ... 

The precise understanding of the structural nature of elastin remains elusive because the unusual physical properties of native elastin have prevented the use of traditional structural biology techniques. The hydrophobic domains are dominated by a pentapeptide repeat sequence of (Val-Pro-Gly-Val-Gly). This repeat sequence is believed to endow elastin its remarkable elastic properties, allowing continual expansion and contractions without loss of structural integrity (2). 

Synthetic ELP hydrogels have been shown to exhibit characteristics similar to those of native elastin in response towards temperature and salt concentrations. Subjecting to mechanical tests, the recombinant human tropoelastin isoform SHELA26A (synthetic human elastin without domain 26A) is extensible up to four times the natural elastin. These hydrogels are able to support cellular growth both in vivo and in vitro (43) (Figure 3A). 

Elastin-like polypeptides (ELPs) are another class of synthetic biopolymers that consist of a repeating pentapeptide sequence that is represented in native elastin. The peptide sequence in ELPs is VPGXG, where X is any amino acid, except proline. ELPs are water soluble and can form micron- or sub-micron-sized aggregates moreover, they are biocompatible and nonimmunogenic, which in turn make it useful as a potent drug delivery system. ... 

Most native elastic tissues consist entirely of elastin. As one would imagine from the name, the elastic properties imbued on the tissues arise from the ahgned elastin fibrils in the tissue. The elastic modulus of the fibers varies largely depending on their location and function. In some cases. 

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