Ficoll viscosity

There are theoretical expressions for the effect of the solvent on the reaction rate using dielectric constant (e) and viscosity parameters. Grissom et al. [95] have reported the increase in photostability of Vitamin B-12 by addition of viscogens, such as glycerol and Ficoll. However, in this section the focus will be on the inLuence of the dielectric constant of the solvent. 

Pretlow et al. (1978) showed that a shallow gradient of Ficoll (2.7-5.5%) centrifuged at low speed (about lOOOg) for about 100 min, allowed clear, isokinetic separation of spheres differing 2-fold in volume. The density change in the gradient was small (1.017-1.027 g/ml) and viscosity effects negligible. 

The most common materials used to generate density gradients are sucrose, Ficoll, and Cs salts. Sucrose solutions can be as concentrated as 65% w/w, with a maximum density of 1.32 g/cm3 at 4 °C however, concentrated solutions of sucrose have high osmotic strength and viscosity. Ficoll is a brand name for a synthetic polysaccharide with an average MW of 400,000 and a maximum density in aqueous solution of 1.23. It is very useful to separate osmotically sensitive particles, like mammalian cells. 

Also, dependence of tlie fluorescence emission on tlie medium viscosity was studied by varying the Ficoll concentration. Addition of sucrose allows maintaining tlie polarity of the medium constant. Figure 9.11 clearly shows that the viscosity has no effect on the maximum emission of protoporphyrin IX. 

Figure 9.11. Correlation between the emission peak ( ) of protoporphyrin IX with viscosity ( ) of sucrose -Ficoll mixtures.

Figure 12.2 Low-shear viscosities of (0) 413 kDa dextran, (Q) 676 kDa dextran, and ( ) 428 kDa ficoll solutions, and functional fits, using measurements reported...

Figure 12.6 Viscosity of (a) (o) ficoll 70 and ( ) calf thymus DNA in phosphate-buffered 0.15 MNaCl, using measurements from Busch, etal.(26), and 445]cDa polymethylmethacrylate in toluene, using measurements of Brown and Rymden (27), (b) Mw 680 kDa hyaluronic acid in water, using results from de Smedt, et fl/.(28), (c) Mw 110 (OX 140 ( ), 450 (A), and 850 ( ) kDa HPC, using data of Yang and Jamieson(29), and (d) 1900 (0)> 610 ( ), 182 (A), 95 ( ), and 57 ( ) kDa polyisobutylenes in chloroform, based on findings of Pu and Brown(30).

Polymers that affect macroscopic viscosity by changing the hydration at the DNA surface substantially increase the rate of annealing (30) Ficoll [neutral polymer, at 5.7% (w/v)] and sodium-dextran sulfate [anionic polymer, at 2% (w/ v)] increase the rate by 1.5 and 4 times, respectively. 

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