Elastin microscopy

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. 

Numerous studies have been undertaken to elucidate the secondary structure of soluble elastin. These studies have been performed on elastin, elastin solubilized by oxalic acid (a-elastin) or potassium hydroxide (/, -elastin). synthetic polypeptide models of elastin, and tropoelastin. Techniques used include circular dichroism, FT-Raman, and electron microscopy. No consensus has been reached on the overall structure of elastin. 

Macroscopically, elastin appears to be an amorphous mass. Ultrastruc-tural electron microscopy studies reveal that elastin has a fibrillar substructure comprised of parallel-aligned 5nm thick filaments that appear to have a twisted ropelike structure (Gotte et al., 1974 Pasquali-Ronchetti et al, 1998). A variety of techniques have been used to resolve these filaments, including negative staining electron microscopy of sonicated fragments of purified elastic fibers (Serafini-Fracassini et al., 1976), freeze... 

Pasquali-Ronchetti, I., Fornieri, C., Baccarani Contri, M., and Volpin, D. (1979). The ultrastructure of elastin revealed by freeze-fracture electron microscopy. Micron. 10, 89-99. 

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. 

Yang G, Woodhouse KA, Yip CM. Substrate-facilitated assembly of elastin-like peptides studies by variable-temperature in situ atomic force microscopy. J. Am. Chem. Soc.,... 

The dermis follows the epidermis and has a thickness of 1 to 2 mm. It is a complex structure and consists of cells including fibroblasts, mast cells, endothelial cells, blood cells, and nerve cells. Fluorescence microscopy suggests that the dermis is filled with a gel containing oriented tropocollagen (polypeptide) macromolecules. The network or gel structure is responsible for the elastic properties of the skin. An approximate composition of the dermis includes collagen (75%), elastin (4%), reticulin (0.4%), and ground... 

Figm 13 (a) Sequence and schematic representation of the self-assembly of an amphiphilic diblock elastin polypeptide into core-shell nanoparticles. Elastin-mimetic protein polymers that comprise fusions of elastin sequences with different 7, values can be induced to undergo self-assembly at a temperature between the two transition temperatures, (b) Differential scanning calorimetry measurements indicate an endothermic transition for the more hydrophobic (lower 7 block with a value that corresponds to those observed for the burial of hydro-phobic residues within a folded protein, (c) This transition coincides with the formation of spherical assemblies in which the more hydrophobic block is confined within the micellar core. Transmission electron microscopy measurements are consistent with spherical micelles and more complex assemblies. Reprinted from Lee, T. A. T. Cooper, A. Apkarian, R. P. Conticello, V. P. Adv. Mater. 2000, f2(15), Copyright 2000, with... 

Figure 15 Differential growth on human umbilical vein endothelial cells plated on glass (left) or glass coated with an elastin-mimetic polypeptide containing the CSS cell adhesion sequence (right). Phase contrast optical microscopy was employed to obtain the images. Reprinted from Panitch, A. Yamaoka, T. Fournier, M. J. et at. MacromoleculesMSS, 32(5), 1701. Copyright 1999, with permission from the American Chemical Society.

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