Ultra-centrifuge

MWCO centrifugal ultra-filter (Microcon, Millipore)... 

Furusawa N, Simultaneous high-performace liquid chromatographic determination of sulfamonomethoxine and its hydroxy/N4-acetyl metabolites following centrifugal ultra-filtration in animal blood plasma, Chromatographia 2000 52 653-656. 

Anotlier standard metliod is to use a (high-speed) centrifuge to sediment tire colloids, replace tire supernatant and redisperse tire particles. Provided tire particles are well stabilized in tire solvent, tliis allows for a rigorous purification. Larger objects, such as particle aggregates, can be fractionated off because tliey settle first. A tliird metliod is (ultra)filtration, whereby larger impurities can be retained, particularly using membrane filters witli accurately defined pore sizes. 

Golden delicious apples Malus domestica) and tomatoes Solarium lycopersicum) were purchased at the local market. Fruits were peeled and sliced before treatment (4 h at 45 °C) with 0.1 % Pectinex Ultra Sp-L (Novo Ferment) in presence of 9 mM ascorbic acid. The insoluble material was then eliminated by centrifugation and the obtained juices dialysed against distilled water. 

Carrots (Boleo) were peeled by 2% NaOH at 88-96°C for 4 minutes, minced by a meat mincer (2 mm) and homogenised for 2 minutes by an ULTRA-TURRAX T25 homogenizer (from Jahne Kunkel). The carrot mash was preheated to 45°C (20 minutes) before the enzyme preparations, 25 mg enzyme protein/kg mash, were added. The enzymes were dissolved in water to give a dilution of 5% (v/v) of the carrot mash. The mash was incubated at 45°C under stirring (60 rpm) for 2 hours, before the enzymes were inactivated at 86°C for 5 minutes in a microwave oven. Finally the purees were homogenised for 1 minute by ULTRA TURRAX. The viscosity of the puree was measured by a BROOKFIELD viscosimeter Model DV-n + with spindle A from HELIPATH SPINDLE SET at 2.5 rpm thermosta-ted at 50°C. The stability of the puree was measured as the sediment (in %) after centrifugation in 10 ml tube a 1660 x g for 10 minutes. 

Combine a 50-g soil sample with 200 mL of ultra-pure water in a 500-mL round-bottom flask. Seal and shake the mixture vigorously for 2 min. Measure the pH to ensure that the pH of the mixed solution is between 6 and 8. Connect the flask to a water-cooled condenser (ca 30-cm height) and reflux the mixture for 2 h. Cool the solution and transfer >100mL of the extract to a centrifuge tube of sufficient size. Centrifuge the extract for 15 min at 3500 rpm. Save a 100-mL aliquot portion of the supernatant for further cleanup. Adjust the pH to 6-8 with phosphate buffer (pH 7) if needed, add 1 mL of methanol to the extract aliquot portion and shake the solution well. 

Separate complexes by ultra-centrifugation using a SW41 rotor at 35,000 rpm for 2 25 h at 4°. 

The specific polysaccharide of the dominant O somatic antigen of Shigella dysenteriae has been shown to be electrophoretically and ultra-centrifugally homogeneous, and to possess a molecular weight of 26,000 from sedimentation and diffusion measurements.2601... 

For separation of colloidal particles and for breaking down emulsions, the ultra-centrifuge is used. This operates at speeds up to 30 rpm (1600 Hz) and produces a force of 100,000 times the force of gravity for a continuous liquid flow machine, and as high as 500,000 times for gas phase separation, although these machines are very small. The bowl is usually driven by means of a small air turbine. The ultra-centrifuge is often run either at low pressures or in an atmosphere of hydrogen in order to reduce frictional losses, and a fivefold increase in the maximum speed can be attained by this means. 

Samples of gallbladder bile obtained in this way were analysed for bile acids, phospholipids and cholesterol (from which the cholesterol saturation indices were derived). Biliary bile-acid composition was then measured by HPLC. The vesicles were separated from micelles by sucrose density gradient ultra-centrifugation and the cholesterol microcrystal nucleation time measured as described above. 

Prepare a linear gradient from Soln. B and Soln. C in a centrifuge tube (e.g., 13 ml Ultra-Clear for Beckman SW 41 rotor 6 ml of Soln. B and Soln. C each) at the day before run. If a gradient mixer is used, e.g., according to Fig. 2.2, place tbe centrifuge tube either in a slanting position, start with Soln. C, and let flow along the tube... 

The tendency for ferritin to aggregate is shown 135, 136) by its heterogeneity as demonstrated on gel electrophoresis, column chromatography, ultra-centrifugation, and many other techniques. This association is readily reversible. The re-examination of any single ferritin fraction isolated from a mixture will show at least four fractions similar to the original preparation. This association is a function of the protein subunit surface of the molecule. Apoferritin molecules behave in a quite similar fashion 137) the iron core has little if any effect. 

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... 

First, the sample was examined by GPC, for which four columns of styragel of 106,10s, 104 and 103 A nominal pore size were used. The total number of theoretical plates as determined by acetone at a flow rate of 1 ml/min was ca. 26,000. The eluent was tetrahydrofuran. The chromatogram is shown in Figure 9, which indicates two peaks at ca. 21 and 24 counts. The former may be assigned to the tetra-chain, star-draped component, and the latter to the precursor. However, no complete separation of the two peaks was observed. For another comparison, velocity ultra-centrifugation was performed for the sample at 59,780 rpm using a 6-solvent for polystyrene, cyclohexane. The operation temperature was established at 35 °C, the 6-temperature, to minimize the concentration dependence of sedimentation velocity and other effects. A sedimentation pattern taken by UV-absorption is shown in Figure 10. It is seen that the separation of S-A sample into the two components was quite difficult even at a very low polymer concentration, 0.077 g/dl. 

Zippe, The Development of Short Bowl Ultra-Centrifuges , EP-4420-101-60V, Univ of Virginia... 

Figure 1. Apparent micellar weight by equilibrium ultra-centrifugation vs. initial concentration difference...

Some data for the molecular weight of cellulose of various origins determined by ultra-centrifuging cuprammonium solution, are given in Table 35. 

Bowen, T. J. (1970) An Introduction to Ultra-centrifugation, Wiley (Interscience), New York... 

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