Citrate extraction

BoNTs can be isolated from bacterial culture by acid precipitation and citrate extraction of the pellet, followed by ammonium sulfate fractionation and chromatography on SP-Sephadex (Shone and Tranter, 1995). Alternatively, CNTs can also be obtained from different commercial sources (see 14.8). 

Chemical extractions were performed in parallel (non-sequential extraction) on soil subsamples to characterize the speciation of trace metals (1) the exchangeable fraction was determined by a CaCl2 extract (2) the fraction supposedly bound to iron and manganese oxides was determined by a Na-dithionite - Na-citrate extraction (3) the fraction supposedly bound to organic matter was determined by a Na-pyrophosphate extraction and (4) the acid-soluble fraction was determined by a 0.43 M HNO3 extract. 

A citrate extract from soil, previously thought to contain oxidative enzymes, was shown to contain manganese in a form capable of oxidative coupling activity toward... 

Repetitive washes with Buffer C diminished O2 rates, determined in the presence of 2 mM EGTA and the absence of Ca, and the Ca abundance to 2 Ca/RC. When assayed in the presence of 15 mM CaCI, the O2 rates were enhanced 5 to 6.5 fold, similar to 2 M NaCl-PS2 membranes which exhibit K , s for Ca + of 50-100 m and 1-2 mM in Ca repletion analyses of 0 evolution (1,10). Extraction with 2 M NaCl at pH 5.0 and repetitive washes with Buffer C decreased the Ca abundance to <1 Ca/RC and virtually eliminated O2 rates in the absence of Ca " addition however, 15 mM Ca reconstituted near maximum 0, rates. Similar Ca depletion and reversible inhibition was obtained using citrate extraction and Buffer C washes. Extraction with 0.8 M Tris Cl"/Buffer C also diminished the Ca to <1 Ca/RC. Scatchard plot... 

For our soils water, EDTA, citrate, NaOH, etc. extractions were carried out on individual samples or subsamples of soils with or without amendment phenolic acid(s). Thus the recovery for each extractant comprised the sum of the free , reversibly sorbed, and/or fixed (not immediately available to roots or microbes) phenolic acids that were recoverable by a given extractant. Differences between water extractions (primarily free phenolic acids) and EDTA or citrate ( free and reversibly sorbed phenolic acids) extractions were utilized to estimate reversibly sorbed phenolic acids. Differences between EDTA or citrate extractions and NaOH extractions were utilized to estimate the fraction of fixed phenolic acids that could be recovered by NaOH. For additional details see Section 2.4.3. This approach has been criticized because free phenolic acids were not removed from soil samples before reversibly sorbed phenolic acids were extracted (Ohno and First 1998). However, in a preliminary study extracting our soils by the traditional method (removing free ... 

Fig. 10.29. RP-HPLC of the pH 4.6-soluble fraction of a citrate extract of Cheddar cheese after 3 (a) and 24 (b) weeks ripening at 10 °C (according to Kaiser et ah, 1992)...

The citrate extract contained alumina as well as iron oxide, so Tamura considers that the structure is stabilized by the two oxides. The indication is that the vermiculite-illite interstratification is changing to a chlorite-illite, or chlorite-vermiculite-illite system. 

Polymers containing 8-hydroxyquinoline appear to be selective adsorbents for tungsten in alkaline brines (95). In the presence of tartrate and citrate, quinaldic acid [93-10-7] allows the separation of zinc from gallium and indium (96). Either of these compounds can selectively separate lead and zinc from oxide ores as complexes (97). It is also possible to separate by extraction micro quantities of rhenium(VII), using quinoline in basic solution (98). The... 

Typically, grape skin extract has a specific gravity of 1.13 g/mL at 20°C, a solids content of 28—32° Brix (=t3°), a pH of 3.0, and a color strength as anthocyanin of about 1.25% (as measured at 520 nm ia pH 3.0 citrate buffet). Grape skin extract is also available as spray-dried powders with color values three to four times those of the liquid. The properties and uses of grape skin extract ate similar to those of grape color extract. 

Hydroxyquinoline, having both a phenolic hydroxyl group and a basic nitrogen atom, is amphoteric in aqueous solution it is completely extracted from aqueous solution by chloroform at pH < 5 and pH > 9 the distribution coefficient of the neutral compound between chloroform and water is 720 at 18 °C. The usefulness of this sensitive reagent has been extended by the use of masking agents (cyanide, EDTA, citrate, tartrate, etc.) and by control of pH. 

Dimethylglyoxime. The complexes with nickel and with palladium are soluble in chloroform. The optimum pH range for extraction of the nickel complex is 4-12 in the presence of tartrate and 7-12 in the presence of citrate (solubility 35-50 fig Ni mL 1 at room temperature) if the amount of cobalt exceeds 5 mg some cobalt may be extracted from alkaline solution. Palladium(II) may be extracted out of ca lM-sulphuric acid solution. 

Procedure. To 10.0 mL of the solution containing up to 200 fig of copper in a separatory funnel, add 5.0 mL of 10 per cent hydroxylammonium chloride solution to reduce Cu(II) to Cu(I), and 10 mL of a 30 per cent sodium citrate solution to complex any other metals which may be present. Add ammonia solution until the pH is about 4 (Congo red paper), followed by lOmL of a 0.1 per cent solution of neo-cuproin in absolute ethanol. Shake for about 30 seconds with 10 mL of chloroform and allow the layers to separate. Repeat the extraction with a further 5 mL of chloroform. Measure the absorbance at 457 nm against a blank on the reagents which have been treated similarly to the sample. 

Discussion. Nickel (200-400 fig) forms the red dimethylglyoxime complex in a slightly alkaline medium it is only slightly soluble in chloroform (35-50 fig Ni mL -1). The optimum pH range of extraction of the nickel complex is 7-12 in the presence of citrate. The nickel complex absorbs at 366 nm and also at 465-470 nm. 

Cobalt in steel Discussion. An alternative, but less sensitive, method utilises 2-nitroso-l-naphthol, and this can be used for the determination of cobalt in steel. The pink cobalt(III) complex is formed in a citrate medium at pH 2.5-5. Citrate serves as a buffer, prevents the precipitation of metallic hydroxides, and complexes iron(III) so that it does not form an extractable nitrosonaphtholate complex. The cobalt complex forms slowly (ca 30 minutes) and is extracted with chloroform. 

Dissolve a known weight (ca 0.5 g) of the steel by any suitable procedure. Treat the acidic sample solution (< 200 /jg Co), containing iron in the iron(II) state, with 10-15 mL of 40 per cent (w/v) sodium citrate solution, dilute to 50-75 mL and adjust the pH to 3-4 (indicator paper) with 2M hydrochloric acid or sodium hydroxide. Cool to room temperature, add 10 mL of 3 per cent (10-volume) hydrogen peroxide and, after 3 minutes, 2mL of the reagent solution. Allow to stand for at least 30 minutes at room temperature. Extract the solution in a separatory funnel by shaking vigorously for 1 minute with 25 mL of chloroform repeat the extraction twice with 10 mL portions of chloroform. Dilute the combined extracts to 50 mL with chloroform and transfer to a clean separatory funnel. Add 20 mL of 2M hydrochloric acid, shake for 1 minute, run the chloroform layer into another separatory funnel, and shake for 1 minute with 20 mL of 2M sodium hydroxide. Determine the absorbance of the clear chloroform phase in a 1 cm cell at 530 nm. 

Extraction and purification of luciferin and luciferase (Viviani etal., 2002a) To isolate luciferin, the lanterns of the Australian A. flava were homogenized in hot 0.1 M citrate buffer, pH 5, and the mixture was heated to 95°C for 5 min. The mixture was acidified to pH 2.5-3.0 with HCl, and luciferin was extracted with ethyl acetate. Upon thin-layer chromatography (ethanol-ethyl acetate-water, 5 3 2 or 3 5 2), the active fraction of luciferin was fluorescent in purple (emission Lav 415 nm when excited at 290 nm). To isolate the luciferase, the cold-water extract prepared according to Wood (1993 see above) was chromatographed on a column of Sephacryl S-300. On the same... 

It is clear from these data that homocitrate is intimately involved in the mechanism of substrate reduction and that close homologs such as citrate cannot entirely fill this role. Rationalization of this phenomenon is difficult, but comparisons of the reactivity of extracted FeMoco from the MoFe protein from wild type and NifV strains have led to an intellectually satisfying explanation (see Section V,E,2). 

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