Rod-shaped structures

Problem. Let a polymer fiber contain rod-shaped structural entities in an amorphous matrix with some preferential orientation. Let us assume that the rods are crystalline. Our interest is to study the crystalline structure of the rods. Instead of sharp hkl reflections we observe that each reflection is smeared over a spherical cap in solid angle. Thus the observed intensity is suitably expressed in polar coordinates... 

At their critical micelle concentrations, surface active agents (such as sodium dodecyl sulfate, Triton X-100, lysolecithin, and bile salts) self-associate into spherical or rod-shaped structures. Because dilution to below the c.m.c. results in rapid disassembly or dissolution of these detergent micelles, micelles are in dynamic equilibrium with other dissolved detergent molecules in the bulk solution. 

Flue gas gypsum is obtained as finely divided crystals in an aqueous reaction medium. Depending on die process, the size and shape of the crystals vary from 1 to 200 pm and from a cubic to a rod shaped structure, as shown in Figs. 2a... 

Going from a phosphaalkene to a phosphaalkyne, we increase the. r-contribution in the carbon phosphorus multiple bond, and would therefore expect a further down-field shift of the phosphorus resonance. However, a glance at the situation in carbon carbon multiple bond systems in particular, alkenes and alkynes, tells us that C-NMR spectra of these molecules show the carbon resonance of alkynes upheld from that of alkenes. This is usually explained by anisotropic effects associated with the linear rod-shaped structure of alkynes versus the bend structure of alkenes. As the geometries of phosphaalkenes andphosphaalkynes are analogous to alkenes and alkynes, respectively, we can assume that the explanation given for the appearance of the carbon resonance in alkynes upheld from that for alkenes in C-NMR spectra is also applicable for the respective unsaturated phosphoms compounds. 

The internal structure of these large particles has not yet been resolved by electron microscopy, but it is clear that they are not homogeneous. It is quite possible that they represent conglomerates of 200 A particles similar to those observed in the experiments of Samarina et al. (1968b) with isolated particles. In the latter case the polysomelike complexes are very often not extended but clumped, and it is impossible to recognize any internal structural organization. For this reason one cannot exclude the possibility that the Beermann particles are polysomelike complexes between D-RNA and informofers. It was shown further that the particles are formed near the chromatin masses from rod-shaped structures (which may be chains of informofers). Different steps in the conversion of rods of 400 A particles may be found. 

Notochord. The notochord is a rod-shaped structure that is derived from the mesoderm close to the neural tube (called axial mesoderm) during gastrulation. It extends from head to tail beneath the developing nervous system and physically supports the embryo. It also secretes factors that control the patterning of surrounding tissues. 

Changes to the molecular shape can afford different supramolecular organization properties. Smectic liquid crystals with layer-by-layer structures (Fig. 1.3) can be obtained by effectively breaking the cone-shaped cavity via the replacement of the five feathers with five rod-shaped structures, which reduces the number of phenyl groups on the five organic addends from ten to five (compound 4) [4]. As a result of these changes, the structure formed from the five rod-shaped addends... 

DNA and proteins are sometimes referred to as the polymers of life. They are more complex in nature and performance than cellulose and starch, and demand a separate examination. In the Uvtng cell, both DNA and proteins take very specific 3-D structures, and do not form either the random coils or the rod-shaped structures of synthetic polymers. The following subsections will describe a few characteristic structures and motions of these natural polymers. 

The presence of polar and non-polar fragments in the macromolecule s structure determines hyaluronan s ability to interact with different chemical compounds and plays a major role in the various conformational transformations. Hyaluronan may exist on the cell surface in an incredibly large number of conformational states (elongated chains, relaxed (non-condensed) helixes, condensed rod-shaped structures, helixes, the structures similar to the pearl necklace and chps ). The HA chains, when interacting with each other, form fibrils, webs and other structures. 

Fig. 15 Perylene 20 that forms rod-shaped structures in dimethyl sulfoxide...

Aerobic respiration occins in prokaryotes in the cytoplasm of the cell but in the eukaryotes it takes place in the cytoplasm and in cell organelles known as mitochondria. These oval- or rod-shaped structures consist of a matrix siuroimded by two membranes between which there is a compartment, as shown in Figine 3.8. The inner membrane is convoluted to increase the surface area and the folds so formed are called cristae which project into the fluid-filled matrix. Respiration takes place in two stages, the first of which occurs in the cytoplasm of the cell and is called glycolysis. The second stage occurs in the mitochondria and involves the citric acid cycle (also known as the Krebs Cycle after its discoverer Hans Krebs) and electron transport. This is discussed below (Figure 3.10). 

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