Chain conformations and interactions

The high concentration method assumes that deuteration does not change chain conformations and interactions (provided that the total polymer concentration is kept constant) i.e., that Pf>(Q) Pf,(Q) (call it PS(Q)) and... 

This method applies for whatever polymer concentration. In practice, it is preferable to use high concentrations in order to increase the signal-to-noise ratio and therefore minimize counting time. However, it can also be applied to semidilute or even dilute solutions where Zimm plots are useful. It also applies not only to linear polymers but also to any form of chain architecture and to deuterated/protonated mixtures in non-solvent matrices such as polymer blends or polymer networks provided that changing the deuterated fraction does not change the homogeneous nature of the mixture (i.e., no change to the chain conformations and interactions). 

Prediction of Polymer Solution Properties from a Model of Chain Conformations and Interactions... 

We can trace this failure to two reasons. First, chain conformations and interactions at molecular and segmental level have not been appropriately taken into consideration. Second -again - the existence of compact bundles has not been realized. While the model we are studying has been constructed essentially in equilibrium terms, its extension to DR and MDF (40) turned out to be successful. To conclude this paper, let us enumerate some of the phenomena related to DR and MDF, explained in terms of the model proposed in (23) and on the basis of our calculations ... 

Besides crystalline order and structure, the chain conformation and segment orientation of polymer molecules in the vicinity of the surface are also expected to be modified due to the specific interaction and boundary condition at the surface between polymers and air (Fig. 1 a). According to detailed computer simulations [127, 128], the chain conformation at the free polymer surface is disturbed over a distance corresponding approximately to the radius of gyration of one chain. The chain segments in the outermost layers are expected to be oriented parallel to the surface and chain ends will be enriched at the surface. Experiments on the chain conformation in this region are not available, but might be feasible with evanescent wave techniques described previously. Surface structure on a micrometer scale is observed with IR-ATR techniques [129],... 

Schwartz BJ (2003) Conjugated polymers as molecular materials how chain conformation and film morphology influence energy transfer and interchain interactions. Annu Rev Phys Chem 54 141-172... 

The availability of high-resolution structures of peptides EKG, T3-785, IBP, and G991-G1032, which include residues other than Pro and Hyp in the X and Y positions, offers the opportunity to investigate the conformation and interactions of side chains from residues typically found within the collagen triple helix. In the peptide with an EKG tripeptide sequence, the Lys and Glu residues did not form direct intermolecular or intramolecular ion pairs, even though such pairs are sterically feasible. ... 

By their nature, and in contrast with microscopic and scattering techniques that are used to elucidate long-ranged structure, spectroscopic methods interrogate short-range structure such as interactions between fixed ions in side chains and counterions, main chain conformations and conformational dynamics, and the fundamental hopping events of water molecules. The most common methods involve infrared (mid-IR and to a much lesser extent near- and far-IR) and solid-state NMR spectroscopies, although other approaches, such as molecular probes, have been utilized. 

Accurate measurements of fluid viscosity are important in many industries for such diverse uses as monitoring syrup manufacture or studying polymer structures such as polymer branching, chain conformation, solvent interactions or polymer molecular weight (MW). Historically, the drop-time type glass capillaries, such as the Ubbelohde or Cannon and Fenske types, have been widely used to measure fluid viscosity. However, this traditional method is tedius and labor intensive, and lacks the desired speed and sensitivity to... 

There is a long history of controversy in the literature regarding the mode of action of general anesthetics. Experimental results derived from model systems of lipids alone or lipid-cholesterol are somewhat controversial. To mention just a few, using Raman spectroscopy it was found that, at clinical concentrations, halothane had no influence on the hydrocarbon chain conformations, and it was concluded that the interaction between halothane and the lipid bilayer occurs in the head group region [57]. This idea was also supported by 19F-NMR studies. The chemical shifts of halothane in a lipid suspension were similar to those in water and differed from those in hydrocarbons. In contrast, from 2H-NMR experiments, it was concluded that halothane is situated in the hydrocarbon region of the membrane (see also chapter 3.3). 

Fig. 4. TRAF2-receptor interactions. (A) Ribbon diagram of a TRAF2-receptor complex, looking down the three-fold axis. The bound receptor chains are shown as stick models. (B) Ribbon diagram of a TRAF2-receptor complex with the threefold axis vertical. The bound receptor chains are shown as arrows. (C) Surface electrostatic representation of TRAF2-peptide complexes. (D) Superposition of bound receptor peptides, showing the structural conservation of the main chain conformations and the side chain conformations at P2, Po, and Pi positions. Parts of this figure were modified from Ye et al. (1999). (See Color Insert.)...

Compare the chain conformations and types of crystal structures found in nylon 6 and silk. Include in your answer a discussion of the role of hydrogen bonding and other interactions. 

The extent of delocalization of electrons, and hence the colours of the antimony chains, may also be influenced by the presence of different conformers and interaction of lone pairs. A more extended conjugation should be possible in all trans chains of the solid whereas gauche interactions in the liquid might interrupt the delocalization. IR and Raman spectroscopic investigations of liquid and solid tetramethyldistibane have been carried out. There are considerable spectral changes between the solid state spectra and the liquid. The possibility of the presence of both gauche and trans conformers in liquid tetramethyldistibane has, however, been discussed controversely - . 

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