Cellulose acetate phosphate, preparation

Triphenyl phosphate is a crystalline solid which has less compatibility with the polymer. This may be expected from solubility parameter data. It is often used in conjunction with dimethyl phthalate and has the added virtues of imparting flame resistance and improved water resistance. It is more permanent than DMP. Triacetin is less important now than at one time since, although it is compatible, it is also highly volatile and lowers the water resistance of the compound. Today it is essential to prepare low-cost compounds to allow cellulose acetate to compete with the synthetic polymers, and plasticisers such as ethyl phthalyl ethyl glycollate, which are superior in some respects, are now rarely used. 

After preincubation of the brush border membrane vesicle preparation for 2 h, [2 14 C]urate uptake is initiated by adding 200 pi of incubation medium to 20 pi of the membrane suspension. The incubation medium has the following composition (mmol/1) 150 mannitol, 2 MgS04, 50 potassium phosphate buffer, pH 6.0 or 7.5, 0.02 [2-14 C]urate, and various concentrations of the inhibitor. At 10 s after the addition of the incubation medium, 200 pi portions of the suspension are pipetted onto the center of prewetted cellulose acetate filters kept under suction. The vesicles retaining on the filter are washed immediately with 5 ml of an ice-cold solution containing 150 mmol/1 mannitol and 50 mmol/1 potassium phosphate buffer, pH 6.0 or 7.5, which is used at the same pH as the incubation medium. Preincubations and incubations are performed at 23 1 °C. Each experiment is performed in triplicate. Corrections are made for the radioactivity bound to the filters in the absence of membrane vesicles. The term of the OH gradient-dependent urate uptake is defined as the difference between the uptakes in the incubation medium at pH 6.0 and that at pH 7.5. The OII gradient-dependent urate uptake at 10 s is assumed to present an initial velocity. 

The functional stability of GOD membranes has also been enhanced by coupling with an asymmetric ultrafiltration membrane (Koyama et al., 1980). The GOD-cellulose acetate membrane used was prepared as follows 250 mg cellulose triacetate was dissolved in 5 ml dichloro-methane, the solution was mixed with 0.2 ml 50% glutaraldehyde and 1 ml l,8-diamino-4-amino methyl octane and sprayed onto a glass plate. After three days the membrane was removed from the support and immersed in 1% glutaraldehyde solution for 1 h at 35°C, rinsed with water and exposed for 2-3 h to phosphate buffer, pH 7.7, containing 1 mg/ml GOD. The membrane was then treated with sodium tetraborate, rinsed with water and stored at 4-lO°C until use. It was combined with the ultrafiltration membrane in the following way 20 mg cellulose diacetate was dissolved in 35 g formamide and 45 g acetone and cast on a glass plate. At room temperature the solvents evaporated within a few seconds and a membrane of about 30 pm thickness remained, which was kept in ice water for 1 h before application in the sensor. 

The varions flavin phosphates and their acetyl derivatives were identified by pH titration, electrophoresis, and H-NMR, which permit direct analysis of crude reaction prodncts as well as rapid purity check of commercial flavin mononucleotide or riboflavin 5 -monophosphate (FMN or 5 -FMN) [7]. Riboflavin 4 -monophosphate was determined as the main by-product of commercial FMN by preparative TLC on cellulose with n-butanol/acetic add/water (5 2 3, v/v) as a solvent [7]. 

Partition Column. Two columns packed with coarse powdered cellulose impregnated with capryl alcohol as immobile phase were prepared in an identical manner. The mobile phase consists of 0.2Af phosphate buffer at pH 6.5. To avoid overloading the column, only a small portion of the extract could be used. The natural extract consisted of 0.20 ml. of the reduced-pressure evaporated solution, corresponding to about 10 grams of kudzu. A similar quantity was added as the spiked extract, except that it contained 500 /xg. of added GA3. Ten-milliliter eluent fractions were collected, acidified to pH 2, and extracted with ethyl acetate. The ethyl acetate extracts were concentrated prior to chromatography. 

In addition to the references cited above (83-91), Kirchner (147) has presented considerable information on TLC analysis of DNP-amino acids based on the literature available up to 1970. Grant and Wicken (148) prepared thin layers (5 plates of 20 x 20 cm x 0.25 mm) from a mixture of 10 g of cellulose MN-3(X) and 4 g of silica gel H (Merck), homogenized in 80 ml of water. The plates were dried overnight at 37 C and developed in the first dimension in two solvents successively, viz., I ro-propanol-acetic acid-H20 (75 10 15) for 15 min and n-butanol-0.15N ammonium hydroxide (1 1, upper phase). The dried chromatograms were developed in 1.5 M sodium phosphate buffer (pH 6.0) in the second dimension. 

Sample preparation Mix 500 xL plasma with 25 p,L 1.5 jig/mL IS in 50 mM pH 7.2 phosphate buffer. Using a Cuprophan cellulose membrane (cut-off 15 kDa) dialyze a 370 m-L aliquot against 18 mL 40 mM pH 4.0 ammonium acetate buffer. Pump the buffer through a 650 p,L recipient channel over 18 min and allow it to flow through column A. At the end of this time, backflush the contents of column A onto column B with the mobile phase, monitor the effluent from column B. (ASTED system. After use, flush the donor side with 10 mL 0.05% Triton X-100 in 0.86% NaCl solution. Flush the recipient side with 4 mL 40 mM pH 4.0 ammonium acetate buffer. Regenerate column A with 1 mL 40 mM pH 4.0 ammonium acetate buffer.)... 

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