Helix triple-stranded

Another feature of this particular exopolysaccharide is that gel strength depends upon the temperature used. It is constant between 60-80°C, increasing in strength from 80-100°C and finally changing structure from a single to a triple stranded helix at temperatures over 120°C. This makes it particularly well suited for use as a molecular sieve, immobilised enzyme support and a binding agent. 

Vitagliano, L., Nemethy, G., Zagari, A., and Scheraga, H. A. (1995). Structure of the type-I collagen molecule based on conformational energy computations The triple-stranded helix and the N-terminal telopeptide. / Mol. Biol. 247, 69-80. 

The oriented gel consists of micelles, of which the average diameter is about 80 A. Micelle-micelle distance is about 120 A. Area between micelles is filled with water molecules. Micelle interior is packed mostly by 7/1 single helical molecules that are hydrogen-bonded to one another by water molecules. The single helical molecule is also probably hydrated. Some parts of the micelle are occupied by molcules of triple-stranded helix, which are also hydrated to some extent. 

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]. 

Fig. 35. 300 MHz H CRAMPS NMR spectra of (A) [Pro-Ala-Glyjn (triple-stranded helix), and (B) collagen fibril (triple-stranded helix). Peak assignment H, 10-8 ppm side-chain phenyl, 8-7 ppm H of L-proline residue and H", 4.3-3.8 other side-chain protons, 1.6-1.9 ppm. 

Figure 27. Stereo pair plots of the collagen triple-stranded helix using the polytripeptide (l Pro-L Pro-Gly), coordinates of Miller and Scheraga [129].

The conformation of the triple-stranded helix is shown by means of stereo pairs in Figure 27 for the polytripeptide, (l Pro-L Pro-Gly) . On careful examination it is possible to see why every third residue must be a glycine. These stereo pairs are given for cross-eye viewing rather than the usual wall-eye (distance) viewing. 

Every third amino acid in the collagen chain is glycine. It is important to the structure because the triple-stranded helix forms as a result of interchain hydrogen bonding involving glycine. Thus, every third amino acid on one strand is in very close contact with the other two strands. Glycine has another... 

Only single-stranded mRNAs can serve as templates for protein synthesis. Since poly(G) forms a triple-stranded helix, it cannot serve as a template for protein synthesis. 

By applying this method to the triple-stranded helix of schizophyllan (an extracellular (3-, 3-glucan) in water, Yanaki et al. [36] obtained essentially the same values for the above three parameters (Ml = 2150 nm, d = 2.6 nm, and q — 200 nm) from [77] and / measured over a wide range of M. Figure 5-7 shows that their experimental results can be described with these parameter values. This Ml value yields 0.3 nm for /i, which happens to equal the pitch per main chain glucose residue of the schizophyllan triple helix in the crystalline state [37],... 

To confirm the conformational properties of CUR-N+, we measured the optical rotatory dispersion (ORD) spectra at various conditions (Fig. 35A). In the form of a triple-stranded helix, the ORD spectra of /J-l,3-glucan polysaccharides such as SPG and CUR have positive values at the wavelength region from 600 to 200 nm. However, CUR-N+ in water shows a negative sign at this... 

Figure 35 Supramolecular isomerism—influence of solvent, (a) Chemical structure of the basic building block, copper(I) 2-ethylimidazolate, (b) supramolecular chain isolated from a polar solvent, (c) triple-stranded helix shown in space Ailing mode resulting from the combination of three symmetry-related chains illustrated in (b), and (d) zigzag chain obtained from a less-polar solvent.

Realignment of the chains follows two strands of pro-a and one chain of pro-a are joined to form a triple-stranded helix (b-d). The extended peptides at the N-terminus appear to play a distinct role in these reactions. Disulfide bridging occurs between the strands at this stage in order to stabilize the structure. The procollagen thus formed will cross the membrane of the cell in which it was synthesized (e). The N-terminal peptides are removed by limited proteolysis (f) and the pro-... 

Some of the /3-amyloid proteins are built from a double or triple strand helix called /3-helix, formed by the association of parallel /3 strands in a helical pattern. The structure was first found in the tail region of bacteriophages P22 and T4 where a rigid structure that would sustain the mechanical injection of DNA into bacterial cell body through cell wall and cell membrane [58, 59] and the growth property of amyloid protein was studied using TIRFM [60]. 

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