In backbone

Carbon Cha.in Backbone Polymers. These polymers may be represented by (4) and considered derivatives of polyethylene, where n is the degree of polymeriza tion and R is (an alkyl group or) a functional group hydrogen (polyethylene), methyl (polypropylene), carboxyl (poly(acryhc acid)), chlorine (poly(vinyl chloride)), phenyl (polystyrene) hydroxyl (poly(vinyl alcohol)), ester (poly(vinyl acetate)), nitrile (polyacrylonitrile), vinyl (polybutadiene), etc. The functional groups and the molecular weight of the polymers, control thek properties which vary in hydrophobicity, solubiUty characteristics, glass-transition temperature, and crystallinity. 

Fig. 5.3 Evolution of the aPNA backbone design. Rationale for choice of amino acid in backbones 1 and 2...

NMRrelaxation and diffusion experiments provide important insights into both the internal molecular dynamics and the overall hydrodynamic behavior of unfolded and partly folded states. Local variations in backbone dynamics are correlated with propensities for local compaction of the polypeptide chain that results in constriction of backbone motions (Eliezer et al., 1998, 2000). This can occur through formation of... 

Crane et al. first established the three-dimensional fold of NOS by solving the structure of a monomeric form of the mouse iNOS heme domain (78). This version of iNOS was missing the first 114 residues, which are known to be critical for dimer formation and activity (79). The monomer structure was soon followed by the dimeric heme domain structures of mouse iNOS (80), bovine eNOS (81), and the human isoforms of iNOS (82, 83) and eNOS (82). A comparison of eNOS and iNOS reveals that the structures are essentially the same with an overall root-mean-square deviation in backbone atoms of 1.1 A (S3). The sequence identity between human iNOS and bovine eNOS is 60% for 420 residues compared in the crystal structures (83). 

A notable feature of the HO-1 distal helix is its flexibility. The HO-1 crystal form used for solving the structure has two molecules in the asymmetric imit, which provides two independent views of the HO-1 structure. As shown in Fig. 19, a plot of the rms (root-mean-square) deviation in backbone atoms between molecules A and B in the as5un-metric imit reveals a large deviation in the distal helix as well as in the loop immediately following the distal helix. In addition, the distal... 

Depolymerization can result in backbone degradation and/or in the formation of cyclic or other products. The thermal degradation of PVA and PVC occurs with the splitting of water... 

Homodetic cyclic peptides are classified according to the location of the ring juncture as shown in Scheme 1. The most common mode of cyclization is head-to-tail where ring closure occurs by amide bond between the N-terminal amino group and the C-terminal carboxy group. Additional ring closures involve side-chain functionalities such as head-to-side-chain, side-chain-to-side-chain or side-chain-to-tail cyclizations. Moreover, in backbone cycliza-tions 29 (see Section 6.8.3.2.4) the backbone amides may be linked to a second backbone amide or to side chains as well as to the termini of the peptide. 

Table III shows x values for other structurally regular substituted silane high polymers measured both at 1.064 and 1.907 /an. Examination of this data suggests relatively little difference between the polysilanes with nonplanar, yet regular structures and trans planar PDN6S which is included in the table for comparison. This result is a little surprising given that changes in backbone conformation can cause spectral absorption shifts of more than 60 nm.

The absorption maximum of alkyl-substituted polysilanes shifts linearly to lower energies with increasing substituent size. This shift comes from steric interference of the substituents, resulting in straining of the Si-Si backbone and a change in backbone conformation.75... 

In the PFPE Zdol model, due to the polarity of endgroups induced by the hydroxyl group, the atomistic interaction is different from that in backbone beads. Here, the polarity interaction is assumed to occur within a short range, and is modeled as an exponential decay function. The potential function among endbeads is... 

New cyclolinear carbosiloxane copolymers containing organotricyclohexasiloxane fragments in backbones were synthesized in the reaction. They represent viscous liquids with molecular mass varying in the range of 35xl03 - 45 xlO3. 

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