Sedimentation behavior

This chapter contains one of the more diverse assortments of topics of any chapter in the volume. In it we discuss the viscosity of polymer solutions, especially the intrinsic viscosity the diffusion and sedimentation behavior of polymers, including the equilibrium between the two and the analysis of polymers by gel permeation chromatography (GPC). At first glance these seem to be rather unrelated topics, but features they all share are a dependence on the spatial extension of the molecules in solution and applicability to molecular weight determination. 

This term gives some information about the asymmetry of the molecular weight distribution and is important in analyzing sedimentation behavior in ultracentrifugation. 

The control of sedimentation is required to ensure a sufficient and uniform dosage. Sedimentation behavior of a disperse system depends largely on the motion of the particles which may be thermally or gravitationally induced. If a suspended particle is sufficiently small in size, the thermal forces will dominate the gravitational forces and the particle will follow a random motion owing to molecular bombardment, called Brownian motion. The distance moved or displacement, Dt, is given by ... 

POCs proportions and content of POCs in river waters compared with maximum permissible concentration (MPC, for DDT, HCH and PCB, are equal to 100,20 and 1 ppb correspondingly for water and 100,100 and 100 for bottom sediments) behavior of toxic compounds in the water body factors promoting an increase of the ecological risk of polluted riverine input into the Caspian Sea (Figure 4). 

As a consequence of high osmolarity, macromolecules or organelles are dehydrated resulting in altered sedimentation behavior thus, different buoyant densities for nucleic acids and mitochondria are observed in different density gradient media, as illustrated in Table 5.3. Data of some density gradient media are given in Table 5.4. 

An alternative description of protein-containing RMs was given by Levashov et al. [148] from ultra-centrifugation studies. Water-soluble dyes (picric acid) were used to determine the molecular weights and sedimentation behavior of the non-protein-containing and protein-containing RMs. The proposed model involved two regimes of Wg (i) at low Wg (where the inner reverse micellar diameter was less than the protein diameter), the protein created a new RM around itself such that the volume of the inner cavity of the filled RM was essentially the volume of the solubihzed protein and (ii) at water contents where... 

Equation (9) is an important result since it describes the relationship among Rs, v, r/, and Ap, the density difference. Any one of these quantities may be evaluated by Equation (9) when the other three are known. Thus, Equation (9) can be used to determine the density difference between two phases or to determine the viscosity of a liquid. In this chapter, however, our interest is in the characterization of colloidal particles by means of observations of their sedimentation behavior. Therefore, we are primarily concerned with Equations (11) and (12), which are specifically directed toward this objective. 

Seagrave, J. Reyes, P. Pyrimidine nucleoside monophosphate kinase from rat bone marrow cells chromatographic, electrophoretic, and sedimentation behavior of active and inactive enzyme forms. Arch. Biochem. Biophys., 247, 76-83 (1986)... 

Sedimentation Behavior. The coating of cathode-ray tubes is usually carried out by sedimentation. The sedimentation characteristics of CRT phosphors and their blends under typical application conditions are an important criterion for their suitability. The sedimentation density allows conclusions to be made on the degree of agglomeration of individual crystals. 

Ghose, A. C., Chaudhuri, S. and Sen, A. 1968. Hydrogen ion equilibria and sedimentation behavior of goat /3-lactoglobulin. Comparison of goat and bovine /3-lactoglobulin. Arch. Biochem. Biophys. 126, 232-243. 

Figure 11.1. Sedimentation behavior of a slurry, showing loose and compacted zones (Osborne, 1981).

Sedimentation tests are of value particularly for rapid evaluation of the effects of aging, flocculants, vibration, and any other variables that conceivably could affect a rate of filtration. The results may suggest what kinds of equipment to exclude from further consideration and what kind is likely to be worth investigating. For instance, if sedimentation is very rapid, vertical leaves are excluded, and top feed drums or horizontal belts are indicated or it may be indicated that the slurry should be preconcentrated in a thickener before going to filtration. If the settling is very slow, the use of filter aids may be required, etc. Figure 11.1 illustrates typical sedimentation behavior. Figure 11.2 summarizes an experimental routine. 

Electrophoretic mobilities of the quartz particles in cobalt (II) perchlorate solutions were determined with a calibrated Zeta-Meter apparatus. Coagulation sedimentation behavior was followed using a stop-flow type apparatus. The dispersion is pumped in a closed loop from an equilibration vessel through an optical cell located in the sample compartment of a recording spectrophotometer. From the optical densitytime curve obtained from the time the pump is switched off, the turbidity index (in arbitrary units) is obtained as the slope of the curve at zero time. 

Methods based on differences in sedimentation behavior between the two types of DNA. This is the approach of choice if highly purified plasmid DNA is required. 

This property remains difficult to define and to estimate. The value of 0.6 g/g quoted above from low angle X-ray scattering appears high. In a careful study of sedimentation behavior as a function of salt concentration, Cox and Shumaker 263) concluded that the preferential... 

The lower curve in Figure 6 shows the sedimentation behavior of a PMMA latex containing 2% acrylic acid added in Stage II in the same manner employed to make the model carboxylic acrylic latex. A contraction of approximately 75 A was observed at pH = 11. 

During the development of our OMA-based detector system we performed a number of tests aimed at verifying the correct behavior of various components. With the completion of the entire system, it was important to evaluate its performance by the examination of images obtained from objects with known dimensions and solutions of known sedimentation behavior. 

Even though one can obtain good agreement between the measured and calculated light intensity profiles for sedimentation equilibrium experiments, this method has drawbacks for the routine assessment of the performance of the optical system. There is not commercially available a standard solute with guaranteed purity and certified sedimentation behavior. Moreover each experiment requires a correction baseline obtained from the cells spun with both sectors filled with solvent. Since a time period of 8 hr or more is required to achieve equilibrium, it becomes a formidible task to investigate the effect of a number of parameters. 

Phelps, R. A. and J. R. Cann On the modification of conalbumin by acid. II. Effect of pH and salt concentration on the sedimentation behavior, viscosity, and osmotic pressure of conalbumin solutions. Arch. Biochem. Biophys. 61, 51 (1956). 

The thickness of the platelets can be adjusted by controlling the reaction conditions to produce interference colors. The pigment crystals are mechanically sensitive and show a fast sedimentation behavior because of the high density (6.4gcm 3). Agglomeration tendency and occupational health (toxicity) risks are the reason why Pb(OH)2 2PbC03 is not produced in powder form, but is flushed from the aqueous phase into suitable organic solvents or resins and handled as stabilized dispersions. Today, the application of basic lead carbonate is limited to artificial pearls, buttons, and bijouterie. 

The interaction between particles and fluids is important in many industrial processes. The most relevant size distribution in such cases is, therefore, based on the sedimentation behavior of particles in fluids and the applicable size is the settling or Stokes diameter. 

R. G. Martin and B. N. Ames, J. Biol. Chem., 236 1372 (1961). A Method for Determining the Sedimentation Behavior of Enzymes Application to Protein Mixtures. 

Kegeles, G., L. Rhodes and J. L. Bethune (1967). Sedimentation Behavior of Chemically Reacting Systems. Proc. Natl. Acad. Sci. 58,45-51. 

Ribosomal RNA (rRNA), the major component of ribosomes, plays both a catalytic and a structural role in protein synthesis (Section 29.3.1). In E. coli, there are three kinds of rRNA, called 23S, I6S, and 5S RNA because of their sedimentation behavior. One molecule of each of these species of rRNA is present in each ribosome. 

Figure 1. Ultracentrifuge Schlieren photographs of sedimentation behavior of highly purified rat skin collagen and its mildly gelatinized product at corresponding times...

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