Collagen fibrils models

Figure 3 Molecular packing in collagen fibrils Model for a transverse section. The red dots correspond to molecules ending in the gap. Reproduced from Hulmes, D. J. S. Wess, T. J. Prockop, D. J. Fratzl, P. Biophys. J. 1995, 68,1661-1670. Copyright (1995), with permission from Elsevier.

Chapman, J. A., Tzaphlidou, M., Meek, K. M., and Kadler, K. E. (1990). The collagen fibril—a model system for studying the staining and fixation of a protein. Electron... 

Fig. 4. A model for the possible relationship between crystalline and disordered regions within a collagen fibril. The cross-sectional model of a 50-nm diameter fibril shows regions of crystallinity interfaced by grain boundaries. The individual crystalline unit cells are shown and the gap region is represented by a darker color. The axial projection of a single microfibrillar unit is also shown. Based on die structures developed by Hulmes et al. (1995) and adapted with permission from Hulmes et al (2002).

Ortolani, F., Giordano, M., and Marchini, M. (2000). A model for type II collagen fibrils Distinctive D-band patterns in native and reconstituted fibrils compared with sequence data for helix and telopeptide domains. Biopolymers 54, 448-463. 

Trus, B. L., and Piez, K. A. (1980). Compressed microfibril models of the native collagen fibril. Nature 286, 300-301. 

Tendon contains dense ECM composed primarily of aligned collagen fibers. The modeling of this tissue is simpler than other ECMs because the analysis requires considering the mechanism of collagen fibril deformation, which has been studied in great depth. On a molecular basis the initial part... 

Fig. 5 TEM images of acid-soluble collagen fibrils formed a in the absence and b in the presence of DNA. c Schematic model of collagen-DNA complex formed in aqueous solution...

It should be pointed out that Schmitt, et al. (1942) have shown, under certain conditions in the electron microscope, that collagen fibrils can apparently extend manyfold. This led Bear (1952) to suggest that a successful model should allow for such extensibility. However, under all other conditions collagen fibers have proved essentially inextensible beyond about 10% over rest-length, and in recent years this requirement for the collagen structure seems to have been generally abandoned. 

Next, we discuss the collagen, which takes the triple helix structure. The amino acid sequence of collagen fibril consists of the repeating amino-acid sequence unit [Gly-Xaa-Yaa]n, where Xaa and Yaa are frequently occupied by prolyl (Pro) and 4-hydroxyprolyl (Hyp) residues, respectively. It is well known that the sequential model polypeptides such as [Pro-Ala-Gly]n or [Pro-Pro-Gly]n take the triple-helix conformation similar to that of collagen, as studied by X-ray diffraction and C, N CP-MAS NMR. This section focuses on the structure of [Pro-Ala-Gly]n, and the collagen structure as described by H CRAMPS NMR. 

Some natural fibrous proteins and sequential model polypeptides have been used as follows (1) Tussah Antheraea perni silk fibroin [a-helix form], (2) Bombyx mori silk fibroin [silk I and II forms], (3) poly(L-alanyL-glycine) [Ala-Gly]i2 [silk I and II], (4) collagen fibril [triple-strand helix], and (5) poly(L-prolyl-L-alanyL-glycine) [Pro-Ala-Gly [triple-strand helix]. 

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