Elastin chemical structure

Scheme 9 Chemical structure of the modified, elastin-like poly (pentapeptide) XIV, found to exhibit photomodulated inverse temperature transition. 59 ...

Fig. 8 pH-dependent LCST behavior of a triblock copolymer containing elastin side chains, a Chemical structure b turbidity measurements performed at different pH (1, 2 and 3) for a triblock copolymer consisting of a PEG block of Mn = 1000 g/mol and elastin blocks with n = 11. Reprinted with permission from [41]. Copyright 2005 American Chemical Society... 

Martino, M., Perri, T., and Tamburro, A. M. (2002). Elastin-based biopolymers Chemical synthesis and structural characterization of linear and cross-linked poly (OrnGlyGlyOrnGly). Biomacromolecules 3, 297-304. 

The view that the structure and properties of elastin can be understood on the basis of the presence of chemical cross bonds at fairly wide intervals... 

Types of Bonds in Proteins. Two kinds of bonds are usually present. The main covalent bonds are the peptide bonds between the amino acid residues and the disulfide bonds which are the cross-links. Both of these are subject to chemical modification. With very few exceptions, methods for chemical modifications must not affect the peptide bonds. In addition, there are certain other types of cross-linkages found in specialized proteins such as in the structural proteins collagen and elastin. 

Urry, D. W., Mitchell, L. W., and Ohnishi, T. (1974). Biochem. Biophys. Res. Comm. 59, 62. Solvent Dependence of Peptide Carbonyl Carbon Chemical Shifts and Polypeptide Secondary Structure The Repeat Tetrapeptide of Elastin. 

Early in our studies it was expected that the post-translational modification of proline hydroxylation, so important to proper collagen structure and function, would raise the value of the temperature, T, for the onset of the inverse temperature transition for models of elastin. Accordingly, hydroxyproline (Hyp) was incorporated by chemical synthesis into the basic repeating sequence to give the protein-based polymers poly[fvs,i(Val-Pro-Gly-Val-Gly), fHyp( al-Hyp-Gly-Val-Gly)], where f sl -i- fnyp = 1 and values of fnyp were 0, 0.01, and 0.1. The effect of prolyl hydroxylation is shown in Figure 7.49. Replacement of proline by hydroxyproline markedly raises the temperature for hydrophobic association. Prolyl hydroxylation moves the movable cusp of... 

It is not always possible to apply enzymatic hydrolysis directly to proteins as they are in the native form. Native, globular proteins (e.g., from soy, corn, almond) or fibrous insoluble proteins (e.g., collagen, keratins, elastin) are generally resistant to proteolysis this is generally explained by the compact tertiary structure of the protein that protects most of the peptide bonds. In the denatured, unfolded form the peptide bonds are exposed and available for enzymatic cleavage. As native proteins in aqueous solution are in dynamic equilibrium with a number of more or less distorted forms, part of which can be considered denatured and thereby accessible to enzyme attack, the initial break of a few peptide bonds can destabilize the protein molecule and cause irreversible unfolding in some cases (e.g., hydrolysis of egg albumin by pepsin) this mechanism allows the protease to perform the hydrolysis to a remarkable extent. More frequently, especially when covalent bonds (disulfide bonds) stabilize the native form of the protein, a preliminary partial or extended denaturation is needed to make enzymatic hydrolysis possible this is normally achieved by heating or chemical attack, or a combination of the two. 

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