Ultrafiltration method

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). 

Temperature 37°C, 0.02 M ionic strength, ultrafiltration method, small unilamellar vesicles (DMPC) [441],... 

Attached to the periphery of a lst-generation dendrimer, Ti(OCHMe2)2-com-plexes of the six TADDOL moieties in 84 catalyze - in homogeneous solution -the enantioselective addition of diethylzinc to benzaldehyde with about the same selectivity ((S) (R) 97 3) as do six monomeric TADDOL units [105],but, with a molecular weight of only 3833 Da, dendrimer 84 had to be separated by column chromatography rather than by ultrafiltration methods. 

Undoubtedly, the most notable feature of these new dendrimeric organometallic molecules is their ability to act successfully as effective homogeneous catalysts for the Kharasch addition reaction of polyhalogenoalkanes to olefinic C=C double bonds. Indeed, they show catalytic activity and clean regiospecific formation of 1 1 addition products in a similar way to that observed in the mononuclear compounds. Likewise, the nanoscopic size of these first examples of soluble dendritic catalysts allows the separation of such macromolecules from the solution of the products by ultrafiltration methods. 

Biologically friendly ionic surfactants can be added to the wastewater at concentrations above the threshold value beyond which the surfactants self-assemble to form micelles. The resulting micelles can trap the hydrocarbon wastes since the hydrocarbon solutes prefer the hydrocarbon interior of the micelle over the aqueous environment outside. In addition, ionic wastes in the water adsorb to the polar heads of the surfactants (see Fig. 8.1). The resulting waste-laden micelles can then be removed more easily using ultrafiltration methods. Such a process, known as micellar-enhanced ultrafiltration (MEUF), can be made continuous, scalable, cost effective, and environmentally friendly (through the use of biodegradable surfactants). 

In either approach, the selection of isolation (e.g., solvent extraction, adsorption on carbon and synthetic resins) and concentration (e.g., lyophilization, vacuum distillation, reverse osmosis, ultrafiltration) methods is of paramount importance in properly assessing the potential toxicity of waterborne organics. A comprehensive literature review on the development and application of these and other methods to biological testing has recently been published by Jolley (3). 

Ultrafiltration is a French originated process that uses a membrane filtering system. In its raw form, whey contains protein, lactose, ash, and some minerals. This should not surprise anyone since whey is the bi-product of cheese or casein production from milk. The original ultrafiltration method separated the ash and lactose from the whey protein resulting in a product providing about 35-70% protein. As the process improved the protein, content was elevated to up to 80% -86.5% protein content. Ultrafiltration provides a decent product with... 

Gamble, D.S., M.I. Haniff, and R.H. Zienius (1986b). Solution phase complexing of atrazine by fulvic acid A theoretical comparison of ultrafiltration methods. Anal. Chem., 54 732-734. 

By the dialysis method, the protein binding of moxalactam was 43 percent and by the agar-diffusion method, 40 percent (6). By an ultrafiltration method, the binding of moxalactam in pooled fresh human plasma was 50.7 percent at physiologic temperature and pH (38). 

Table 13.7 Comparison of retention data for an environmental sample using different ultrafiltration methods...

Schratter, P. (1996) Purification and concentration by ultrafiltration, Methods Md. Biol. 59,115-134. 

Various comparisons of the conventional refining technique versus the ultrafiltration based method using soybean and rapeseed oils are reported, and the results show that there is no difference in the quality of the oils obtained from these two methods. Table 7 compares composition of crude, degummed, superdegummed, and ultrafiltratred oils. The lowest phospholipid, Ca, Mg, and Fe contents were obtained by the ultrafiltration method. Both UF and superdegummed oils were... 

The ultrafiltration method was found to be very effective for the removal of the excess reagent. An enzymatic method was employed in this case for the splitting of the peptide from the polymer support. 

The total count of bacteria was determined by direct ultrafiltration method on Sartorius filters of pore size 0.2 fxm. The erythrosine solution (4%) was employed for staining. 

The observation that the smaller organic fraction is associated with actinides could have significant applications in the mitigation and cleanup of low-level radioactive contamination in ground and surface waters, in that hollow-fiber ultrafiltration methods could be used to physically concentrate the smaller fractions and remove the actinides 10,21). 

Cylindrical internal reflectance (CIR) techniques have been applied to humic and fulvic acids that were size fractionated by using hollow-fiber ultrafiltration methods with cutoffs of 0.1pm and 100,000, 30,000,... 

Jerkunica I, Sophianopoulos J, Sgoutas D. Improved ultrafiltration method for determining unbound cortisol in plasma. Clin Chem 1980 26 1734-7. 

Historically, direct procedures were too cumbersome, time-consuming, and expensive for use in a routine clinical laboratory. The introduction of very sensitive immunoassays for T4 and T3 combined with improvements in the dialysis or ultrafiltration of undiluted serum has allowed direct measurement of free thyroid hormones. Thus direct equilibrium dialysis and ultrafiltration methods are available for FT4 measurement. 

FT4 assays based on direct equilibrium dialysis or ultrafiltration measure free hormone without the need for total hormone measurements. These methods are unaffected by either variations in serum binding proteins or thyroid hormone autoantibodies. However, IV heparin administration can cause spurious elevations m FT4 determined by these techniques as a consequence of in vitro generation of free fatty acids. Mean values obtained in euthyroid healthy subjects are reported to be slightly higher when using ultrafiltration methods than when using equilibrium dialysis. Analytical performance goals have been recommended for free thyroid hormone assays.When an FT4 assay... 

Sophianopoulos JA, Jerkunica I, Sgoutas DS. A rapid ultrafiltration method for the measurement of free thyroxine (FT4) or free triiodothyronine (FT3) in serum. Clin Chem 1979 25 1080-1. 

Tikanoja S, Liewendahl R. New ultrafiltration method for free thyroxin compared with equhibrimn dialysis in patients with thyroid dysfunction and nonthy-roidal illness. Clin Chem 1990 36 800-4. 

In the equilibrium dialysis/ultrafiltration method for determining free testosterone in blood, a sample is first equilibrated with radioactive testosterone. Free steroid is then separated from bound steroid by filtration through an anisotropic, hydrophilic ultrafiitration membrane. The driving force for ultrafiltration is provided by centrifugation at 1000 to 2000 xg. Filtrate containing free steroid collects in the filtrate cup, whereas protein-bound steroid remains above the filter. Radioactivity in the filtrate is a measure of... 

Ephraim J.H., Mathuthu A.S., Marinsky J.A. (1994), Calcium binding by fulvic acids studied by an ion selective electrode and an ultrafiltration method. Humic Substances in the Global Environment and Implications on Human Health, (Ed. N. Senesi, T.M. hliano), Elsevier Science, 1125-1130. 

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