Filter paper molecular weight

The resins used in air and oil filters are moderate-to-low molecular weight, catalyzed by caustic in one step 10—20% alcohol is added soHds content is in the range of 50—60%. These resins are designed to penetrate the sheet thoroughly, yet not to affect the porosity of the paper. In the B-stage, the resin must have sufficient flexibiHty to permit pleating the C-stage should have stiffness and resistance to hot oil. 

This method is very useful for separating amino acids found in food samples. The most effective matrix for separation is an absorbent cellulose-based filter paper. A very effective mobile phase is 70% isopropyl alcohol in water. Although the 20 amino acids are chemically very similar, they may be successfully separated by this method. Amino acids interact with the stationary phase to different extents, thus moving at different speeds. Chemical differences among amino acids that determine migration speed include molecular weight, charge, and polarity. 

The dimer has also been isolated from photolysis of dried uracil deposits on filter paper,33 and its elementary composition and molecular weight determined. It has an ultraviolet spectrum similar to that of thymine dimer (15). Uracil can be recovered by photolysis of the dimer in solution at 240 nm, but only to the extent of 75%. The photoreversal of dimer in solution gives, in part, the photohydrate.33 The thermal reversibility of the photolyzed aqueous solution ranges from 17 to 44% recovery of absorbance. 

Sluyterman, J. A., Electrophoretic behaviour in filter paper and molecular weight of insulin. Biochim. et Biophys. Acta 17, 169 (1955). 

To 10 mL of the stock solution of 2,4-dinitrophenylhydrazine in phosphoric acid add about 0.1 g of the compound to be tested. Ten milliliters of the 0.1 M solution contains 1 millimole (0.001 mole) of the reagent. If the compound to be tested has a molecular weight of 100 then 0.1 g is 1 millimole. Warm the reaction mixture for a few minutes in a water bath and then let crystallization proceed. Collect the product by suction filtration (Fig. 1), wash the crystals with a large amount of water to remove all phosphoric acid, press a piece of moist litmus paper on to the crystals, and if they are acidic wash them with more water. Press the product as dry as possible between sheets of filter paper and recrystallize from ethanol. Occasionally a high-molecular-weight derivative won t dissolve in a reasonable quantity (20 mL) of ethanol. In that case cool the hot suspension and isolate the crystals by suction filtration. The boiling ethanol treatment removes impurities so that an accurate melting point can be obtained on the isolated material. 

Diffusion is simple but rather slow and resolution may be poor compared to the other methods. The gel is placed between two sheets of nitrocellulose membranes, which are in turn inserted between two filter papers covered with foam pads and rigid screens (Bowen et al., 1980 Aubertin et al., 1983 Table 16.9). High-molecular weight polypeptides are transferred less efficiently in the presence of SDS. Nevertheless, in the presence of SDS more faithful replicas... 

To simplify the enzymatic measurement of glucose, Free et al. (1956) adopted the principle of the litmus paper used for pH measurement. By impregnating filter paper with the glucose-converting enzymes they obtained the first enzyme test strip which can be regarded as the predecessor of optoelectronic biosensors and which initiated the development and application of dry chemistry . Nowadays highly sophisticated enzyme test strips are commercially available for the determination of about 15 different low molecular weight metabolites as well as the activities of 10 enzymes. 

Enzyme preparations active against crystalline cellulose, marble-milled filter paper, carboxymethylcellulose (CM-cellulose), hemicellulose, and D-xylan have been obtained from cultures of Ruminococcus flavefaciens. Carboxymethyl cellulase and D-xylanase activities were present in a high molecular weight complex (see p. 461). 

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