Chain connectivity

The electric potential in and around a flexible polyelectrolyte chain is directly dependent on how the monomers are spatially correlated. Unlike the situations in Chapter 3, a flexible polymer molecule cannot be simply assumed to 

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The effect of stereogenic centers along the chain, connecting the 7t-nueleophile and the nitrogen atom, has been studied. For substituents adjacent to the nitrogen atom, an axial orientation is preferred in order to avoid A 1-31 strain between the substituent and the carbonyl function of the A-acyl group146. 

Clostridial neurotoxins are bacterial protein toxins that consist of a heavy and a light chain connected by a disulfide bond and non-covalent interactions. They... 

Ubiquitin/Proteasome. Figure 2 Functional consequences of ubiquitin linkage. Substrates (blue bars) are linked via lysine residues (K) to ubiquitin or ubiquitin chains, (a) Attachment of chains connected via Lysines in position 48 of ubiquitin (K48) targets substrates for proteasomal degradation. In contrast modification of one (b) or multiple (c) lysines by a single ubiquitin molecule mediates novel protein interactions or initiates endocytosis. Conjugation of K63-linked polyubiquitin (d) alters protein function and can also serve as a signal for endocytosis. 

In order to model the restrictions imposed by chain connectivity additional rules are required. Two different sets of rules are used, both of which lead to similar results. The first set derives from the inability of a chain to extend once it has been folded over. The Monte Carlo simulation does not explicitly include folds, but any stem which is completely surrounded by other stems is assumed to have folded and additional units are unable to add in the z-direction. In Fig. 4.3 we denote by all those positions where a new unit may add, all other surface sites are blocked. 

Fig. 2 (a) Antiparallel and (b) parallel P-sheet structures of two peptide chains connected by hydrogen bonds... 

Functionally and strucmrally, the components of the respiratory chain are present in the inner mitochondrial membrane as four protein-lipid respiratory chain complexes that span the membrane. Cytochrome c is the only soluble cytochrome and, together with Q, seems to be a more mobile component of the respiratory chain connecting the fixed complexes (Figures 12-7 and 12-8). 

The purpose of the following treatment is to define the conditions under which indefinitely large chemical structures, or infinite networks, will occur. To this end we seek the answer to the question Under what conditions is there a finite probability that an element of the structure selected at random occurs as part of an infinite network In order to simplify the problem, any given molecule such as the one shown in Fig. 61 may be regarded as an assemblage of chains connected together through polyfunctional, or branch, units (trifunctional in... 

The 68-kDa t-PA molecule, although synthesized as a single chain, undergoes modification to result in A and B polypeptide chains connected by a single disulfide bridge (36). This modification is mediated by factor Xa, tissue kallikrein, and directly on the surface of a thrombus by plasmin (37). The affinity of the A chain... 

Analogues with a seven-carbon chain connecting the phenyl and isoxazole rings, and with a substituent on the oxazoline ring, were bound with the isoxazole ring in the toe of the hydro-phobic pocket. 

The x-ray studies on several analogues in this series of compounds showed that the chain connecting the isoxazole and phenyl rings adopts a bowed... 

Triblock copolymers, as shown in Fig. 5.8 d), comprise a central homopolymer block of one type, the ends of which are attached to homopolymer chains of another type. As with other block copolymers, the components of triblocks may be compatible or incompatible, which will strongly influence their properties. Of particular interest are triblocks with incompatible sequences, the middle block of which is rubbery, and the end blocks of which are glassy and form the minor phase. When such polymers phase-segregate, it is possible for the end blocks of a single molecule to be incorporated into separate domains. Thus, a number of rubbery mid-block chains connect the glassy phases to one another. These materials display rubber-like properties, with the glassy domains acting as physical crosslinks. Examples of such materials are polystyrene/isoprene/polystyrene and polystyrene/polybutadiene/polystyrene triblock copolymers. 

The generic name given to the nylon type of polymer, which consists of short carbon chains connected by amide groups -NHCO-. See Nylon. Polybutadiene... 

For a fluid at a hard wall this implies p(r) = constant. As expected, because the theory leaves out the entropic effects of confinement, namely chain connectivity, it is in qualitative error for the depletion effects" for a polymer at a surface [118-120]. 

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