Fractionation methods ultrafiltration

Fractionation Methods. Ultrafiltration and gel filtration are nondestructive methods which, based on limited experience, can be used for fractionation of mineral complexes from digests. In earlier studies mineral absorption on the gel material was a problem. Lonnerdal (30) introduced a method of treating dextran gels with sodium borohydride in order to eliminate the mineral-binding sites on the gel. In preliminary studies we have recovered more than 90 of Ca, Mg, Fe, Zn and P in samples applied to a borohydride-treated gel column (Sephadex G-50, Pharmacia Fine Chemicals, Piscataway, NJ). Recovery of Ca (Table IV) and Mg, Fe and Zn from ultrafiltration was also good. 

A fractionation method that seems to be of value, for mixtures of polysaccharides of different molecular size, is ultrafiltration, which has been successfully used by Jones and coworkers for the fractionation of dextrans. 

Figure 4.39 Method for preparing /3-casein-enriched fractions by ultrafiltration...

In the second method, ultrafiltration, centrifugal force is applied for a few minutes to a sample of the compound in plasma, pushing the unbound fraction through a permeability selective membrane. LC/MS/MS analysis of the ultrafiltrate and retentate is then done. This has the advantage of being faster than dialysis. Methods like 96-well plate have been developed here too. As in HTS, edge effects have been noted with these, and one study comparing such a method with results from individually run samples for a dozen research compounds showed an value of 0.60. ... 

Many reactions between fluorophores and their environment will reduce DOM fluorescence and are termed quenching reactions. Huorescence is related primarily to various chemical components constituting DOM, which is reflects DOM sources and molecular size and mass. Colloidal organic matter (COM), fractionated by a variety of ultrafiltration and flow fractionation methods, shows distinct patterns in fluorescence, but these patterns are not consistent among freshwater and seawater sources. In freshwater environments protein fluorescence is often found in the highest molecular size fractions, whereas in seawater environments, fluorescence is often found in lower molecular size fractions. 

Phosphoribosyl pyrophosphate synthetase (from human erythrocytes, or pigeon or chicken liver) [9015-83-2] Mr 60,000, [EC 2.7.6.1]. Purified 5100-fold by elution from DEAE-cellulose, fractionation with ammonium sulfate, filtration on Sepharose 4B and ultrafiltration. [Fox and Kelley J Biol Chem 246 5739 197h, Flaks Methods Enzymol6 158 1963 Kornberg et al. J Biol Chem 15 389 7955.]... 

The alternative large scale recovery method to precipitation is ultrafiltration. For concentration of viscous exopolysaccharides, ultrafiltration is only effective for pseudoplastic polymers (shearing reduces effective viscosity see section 7.7). Thus, pseudoplastic xanthan gum can be concentrated to a viscosity of around 30,000 centipoise by ultrafiltration, whereas other polysaccharides which are less pseudoplastic, are concentrated only to a fraction of this viscosity and have proportionally lower flux rates. Xanthan gum is routinely concentrated 5 to 10-fold by ultrafiltration. 

Fractionation of the Sediment Extract. Ultrafiltration methods (17) have produced some useful data about the nominal molecular size of the active component. Crude sediment extract was filtered (Amicon, 50 psi) and separated into three fractions having the following nominal molecular fractions <10,000, <2,000, <500. The fractions were tested for hydrilla-inhibition, and the two lower M.W. fractions proved to be inactive against the plant. The fraction having a M.W. greater than 2,000 but less than 10,000 showed inhibitory action somewhat enhanced over that of the crude extract (12). 

Amino Acid Content. Amino acid content of field pea products is related to protein level, method of processing, and fraction (starch or protein). The protein fraction contains fewer acidic (glu, asp) amino acids than the starch fraction and more basic (lys, his, arg) amino acids than the starch fraction. Also, there are more aromatic (tyr, phe) amino acids, leu, iso, ser, val, and pro in the protein fraction than in the starch fraction (5). An amino acid profile of pea protein concentrate shows relatively high lysine content (7.77 g aa/16 g N) but low sulfur amino acids (methionine and cystine) (1.08-2.4 g aa/16 g N). Therefore, it is recommended that air classification or ultrafiltration be used because acid precipitation results in a whey fraction which contains high levels of sulfur amino acids (12,23). Also, drum drying sodium proteinates decreases lysine content due to the Maillard reaction (33). 

This simplified calculation is used to illustrate basic computational techniques. It assumes that all of the Fe(OH)3(aq) is a true solute. The quality of this assumption is a matter of debate as at pH 8, Fe(OH)3(aq), tends to form colloids. Thus, laboratory measurements of ferrihydrite solubility yield results highly dependent on the method by which [Fe(lll)]jQ(gj is isolated. Ultrafiltration techniques that exclude colloids from the [Fe(lll)]jQjgj pool produce very low equilibrium solubility concentrations, on the order of 0.01 nM. This is an important issue because a significant fraction of the iron in seawater is likely colloidal, some of which is inorganic and some organic. In oxic... 

Elimination of Cellulases from Xylanases. Classical methods of protein fractionation can be used for to separate cellulases and xylanases on a large scale only when they differ considerably in molecular weight or isoelectric point. The Tricho-derma harzianum enzymes were separated by ultrafiltration because the xylanase was smaller and passed through the membrane into the ultrafiltrate 18). Fractional precipitation with organic solvents is another possibility (7). 

Ultrafiltration has been used in fractionating dextrans,244 By use of specially prepared membranes,246 it should be possible to extend this simple, gentle method to effect fractionation of polyglycoses and polysaccharides in general. Gel filtration also permits passage of macromolecules on the basis of their molecular size, and this method has proved useful in the fractionation of dextrans246 and dextrins.247 The ease and capacity of this method should make it valuable in the fractionation of polyglycoses. 

Because NMR spectroscopy is a nuclei-specific technique and has the ability to distinguish between similar compounds, it is an excellent method for identifying similar species in complex matrices. Thus, 31P FT-NMR spectroscopy is ideal for the identification and characterization of the hydrosphere DOP. Even so, NMR spectroscopy is fairly insensitive and requires high sample concentrations. Low DOP concentrations are increased to 31P FT-NMR detection limits by using ultrafiltration and reverse osmosis membranes. Not only is the DOP concentrated, but it is fractionated according to its molecular size. Compared to other concentration and molecular size fractionation techniques for DOP, ultrafiltration and reverse osmosis are relatively rapid and easy. 

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