Chain coiling

Autoacceleration, Glass and Zutty (S) and Burnett and Melville 9) reported an increase in the rate and average degree of polymerization with increasing solution viscosity, heterogeneous conditions and chain coiling for free radical, vinyl polymerizations. Autoacceleration is also called Trommsdorff. (10) effect. 

In network BI in which chain expansion was the greatest, the measured results show more chain swelling than a network with f=3 but less than a network with f=4. Chain swelling was less than that of the phantom network model for the other two networks, and in one case, the chains coiled to a size slightly less than that of the unperturbed molecule. 

The asphericity of uniform stars should decrease with increasing number of arms from the results corresponding to linear chain coils. Highly branched stars present small asphericity values that characterize configurations close to the... 

In contrast, when the coupling reaction was performed in THF without the self-assembly, the SEC profile contains only two peaks, namely, a dimer peak with Mw 1.2 x 104 and precursor triblock copolymer peak. It shows that the coupling reaction stops after two triblock copolymer chains are linked together. This is because for longer copolymer chains (Mw > 104 g/mol), the chain ends are likely wrapped and hidden inside the chains coiled in a good... 

N 125 "Theory of Helix-Coif Transitions of cc-Helical, Two-Chain, Coiled Coils"... 

FIGURE 4-11 Structure of hair, (a) Hair a-keratin is an elongated a helix with somewhat thicker elements near the amino and carboxyl termini. Pairs of these helices are interwound in a left-handed sense to form two-chain coiled coils. These then combine in higher-order structures called protofilaments and protofibrils. About four protofibrils—32 strands of a-keratin altogether—combine to form an intermediate filament. The individual two-chain coiled coils in the various substructures also appear to be interwound, but the handedness of the interwinding and other structural details are unknown, (b) A hair is an array of many a-keratin filaments, made up of the substructures shown in (a). 

Lubricating oil, like this automobile engine oil, consists primarily of high-molar-mass hydrocarbons. Their long chains coil about one another, giving the oil a high viscosity. 

Steinert, P. M. (1990). The two-chain coiled-coil molecule of native epidermal keradn intermediate filaments is a Type I-Type II heterodimer. /. Biol. Chem. 265, 8766-8774. 

Watson and Crick also found that the two complementary strands of DNA are coiled into a helical conformation about 20 A in diameter, with both chains coiled around the same axis. The helix makes a complete turn for every ten residues, or about one turn in every 34 A of length. Figure 23-27 shows the double helix of DNA. In this drawing, the two sugar-phosphate backbones form the vertical double helix with the heterocyclic bases stacked horizontally in the center. Attractive stacking forces between the pi clouds of the aromatic pyrimidine and purine bases are substantial, further helping to stabilize the helical arrangement. 

From the reaction of Au with alkali metal polysulfide liquids, LiAuS and NaAuS were discovered. Both compounds contain infinite one-dimensional (AuS) chains, featuring alternating sulfide anions and linear coordinated Au centers. In LiAu8, the chains are zigzag and fully extended and they pack in mutually perpendicular sets. In NaAuS, the same chains coil in an unusual fashion so that they become interwoven to form layers reminiscent of chicken-wire (Figure 17). This novel coiling mode allows Au Au contacts to form, which help to stabilize the structure. 

The delivery of the NO and the prevention of histamine production are both thought to be carried out by nitrophorin. The nitrophorin molecule consists of a long protein chain coiled around to produce a roughly spherical shape with a heme molecule attached (see accompanying figure). The molecule acts as a carrier of nitric oxide by binding the NO molecule to the iron atom of the heme. 

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