Macromolecular orientation

Kondo T et al (2002) Biodirected epitaxial nanodeposition of polymers on oriented macromolecular templates. Proc Natl Acad Sci USA 99(22) 14008-14013... 

Macromolecular stmcture and supermolecular organization also affect dye affinity. Drawn (oriented) nylon-6 has more of a random open stmcture than nylon-6,6 (172). Nylon-6, therefore, dyes more rapidly than nylon-6,6, but is also more susceptible to color crocking, especially with disperse dyes. 

Macromolecular fixation on the filler surface, their orientation in the direction complanar or normal to the surface and condensation result in hard interphases [116]. 

Usually, dilute polymer solutions are isotropic systems, i.e. macromolecular chains can exist in these solutions independently of each other with a random distribution of orientations of the long axes of coils. The solutions of flexible-chain polymers remain isotropic when the solution concentration increases whereas in concentrated solutions of macromolecules of limited flexibility the chains can no longer be oriented arbitrarily and some direction of preferential orientations of macromolecular axes appears, i.e. the mutual orientations of the axes of neighboring molecules are correlated. This means that... 

Fig. 13 a, b. Possible stacking of macromolecular bilayers in the P form crystals of s-PS. The regular succession of bilayers ABAB. .. gives rise to the ordered P" modification (a) defects, corresponding to pairs of bilayers of the kind AA or BB, would characterize the disordered P modification an AA defect is reported in (b). The symbols (/) and ( ) indicate the orientation of the lines connecting the adjacent phenyl rings of each chain inside the macromolecular bilayers A and B, respectively [29]... 

A disorder of the same kind has been suggested also for the orthorhombic form of s-PS. In fact, in the so-called disordered [V modification the disorder would be in the stacking of ordered macromolecular bilayers and a 3-D long range periodicity would characterize only the mean position and orientation of the phenyl rings [28,29] (Fig. 13). 

Another important sub-case, of disorder in macromolecular crystals, corresponds to the statistical occurrence of two specific orientations only, at well defined positions in a 3-D lattice, of a group of macromolecules or of each single macromolecule. 

Organization into macromolecular structures. There are no apparent templates necessary for the assembly of muscle filaments. The association of the component proteins in vitro is spontaneous, stable, and relatively quick. Filaments will form in vitro from the myosins or actins from all three kinds of muscle. Yet in vitro smooth muscle myosin filaments are found to be stable only in solutions somewhat different from in vivo conditions. The organizing principles which govern the assembly of myosin filaments in smooth muscle are not well understood. It is clear, however, a filament is a sturdy structure and that individual myosin molecules go in and out of filaments whose structure remains in a functional steady-state. As described above, the crossbridges sticking out of one side of a smooth muscle myosin filament are all oriented and presumably all pull on the actin filament in one direction along the filament axis, while on the other side the crossbridges all point and pull in the opposite direction. The complement of minor proteins involved in the structure of the smooth muscle myosin filament is unknown, albeit not the same as that of skeletal muscle since C-protein and M-protein are absent. 

DREAM++ A set of programs (ORIENT++, REACT++ and SEARCH++) for docking computationally generated ligands into macromolecular binding sites University of California [31]... 

In the laboratories of Natta in Milan it was found that the Ziegler catalysts could polymerize (besides ethene) propene, styrene, and several a-olefins to high linear polymers. These polymers appeared crystalline when examined by X-ray diffraction techniques and were able to give oriented fibers. In less than one year since the preparation of the first polymer of propene, Natta was able to communicate, in the meeting of the Accademia dei Lincei of December 1954 in Rome, that a new chapter had been disclosed in the field of macromolecular chemistry, due to the discovery of processes to obtain polymers with an extraordinary regularity in their structure in terms of both chemical constitution and configuration of the successive monomeric units along the chain of each macromolecule. 

Lyotropic polymeric LC, formed by dissolving two aromatic polyamides in concentrated sulphuric acid, have been studied using variable-director 13C NMR experiments.324 The experimental line shapes at different angles w.r.t the external field were used to extract macromolecular order and dynamic in these ordered fluids. An interesting application of lyotropic LC is for the chiral discrimination of R- and S-enantiomers, and has recently been demonstrated by Courtieu and co-workers.325 The idea was to include a chiral compound 1-deutero-l-phenylethanol in a chiral cage (e.g., /1-cyclodextrin) which was dissolved and oriented by the nematic mean field in a cromolyn-water system. Proton-decoupled 2H NMR spectrum clearly showed the quad-rupolar splittings of the R- and S-enantiomers. The technique is applicable to water-soluble solutes. 

Motivating the research is the need for systematic, quantitative information about how different surfaces and solvents affect the structure, orientation, and reactivity of adsorbed solutes. In particular, the question of how the anisotropy imposed by surfaces alters solvent-solute interactions from their bulk solution limit will be explored. Answers to this question promise to affect our understanding of broad classes of interfacial phenomena including electron transfer, molecular recognition, and macromolecular self assembly. By combining surface sensitive, nonlinear optical techniques with methods developed for bulk solution studies, experiments will examine how the interfacial environment experienced by a solute changes as a function of solvent properties and surface composition. 

Journal of Macromolecular Science A A35, NOS.7 8,1998, p. 1147-58 MORPHOLOGY AND ORIENTATION OF PP-STRUCTURAL FOAM MOULDINGS... 

Various criteria can be considered in the classification of the SEC applications. The most important are the analytical SEC procednres. The preparative applications, which encompass the purification of complex samples before their further treatment, draw rather wide attention. In this latter case, analytes are preseparated by SEC according to the size of their components and either macromolecular or low molecular fractions are subject to further analyses by other methods. The production oriented SEC did not find wide application in the area of synthetic polymers due to both the high price of organic solvents and the ecological considerations. 

This bimodal dynamics of hydration water is intriguing. A model based on dynamic equilibrium between quasi-bound and free water molecules on the surface of biomolecules (or self-assembly) predicts that the orientational relaxation at a macromolecular surface should indeed be biexponential, with a fast time component (few ps) nearly equal to that of the free water while the long time component is equal to the inverse of the rate of bound to free transition [4], In order to gain an in depth understanding of hydration dynamics, we have carried out detailed atomistic molecular dynamics (MD) simulation studies of water dynamics at the surface of an anionic micelle of cesium perfluorooctanoate (CsPFO), a cationic micelle of cetyl trimethy-lainmonium bromide (CTAB), and also at the surface of a small protein (enterotoxin) using classical, non-polarizable force fields. In particular we have studied the hydrogen bond lifetime dynamics, rotational and dielectric relaxation, translational diffusion and vibrational dynamics of the surface water molecules. In this article we discuss the water dynamics at the surface of CsPFO and of enterotoxin. 

Another experimental method that has been used to determine orientational correlation functions in macromolecular systems is based on measurements of the time-dependence of the depolarization of fluorescence 26 From these measurements rotational diffusion coefficients and the shape of the rotating macromolecule have been determined.27... 

Mesophase materials of linear, flexible macromolecules have gained attention only more recently, when it was found that parallel molecular orientation is easily achieved in some of these mesophases. This orientation can lead to high modulus and tensile strength 6). Presently there exists a certain amount of confusion in the literature about the description, properties, and nomenclature of these macromolecular mesophases and their place in the arrangement of all matter. Even for the better understood small-molecule mesophases there are some problems in the description of glasses and in the separation of orientational and conformational disorder. Also, the distinction between mesophases based on molecular structure and on super-molecular structure is not always made. We will try in this review to clarify some of these points. 

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