Fructose, and dextran

This approach is valid for more complex isotherms only when the i.e., ternary interaction effects can be neglected and the adsorbate-adsorbate interactions in the ternary system are the same as these interactions between the same components in the corresponding binary systems. The validity of this assumption was confirmed for the mixtures of fructose and dextran T6, of fructose and dextran T9, and of dextran T6 and dextran T9, by comparing the predicted and the measiued retention times obtained for the ternary system [111]. 

On the Exploring simulation box (LHS), click on component list. Then in the Contents box below double-click on Default. A and B are listed. Change these names to the names of the conponents to be separated (fructose and dextran T6). First, click the Remove all button. In the window below, type in the first component name (e.g., fructose), and click on the add button. Do the same for all the other components. Click OK. ... 

Now click on the Specify button. This opens an imposing table where you specify the column dimensions, isotherms, and so forth. Note that it lists fructose and dextran T6 because in step 3 you told it to do this. Use the following values to start with L = Hb = 25 cm, column diameter Db = 2.0 cm, external porosity Ei = 0.4, particle porosity Ep = 0.0, dispersion coefficients Ez = 0.15 for both components. Mass transfer coefficient MFC = 5.52 min (fructose) and = 2.84 min (dextran T6). Isotherm coefficients Aspen uses the formula for linear isothernr q = (IPl) c + IP2. 

When dextransucrase is allowed to act on sucrose, the final concentration of the disaccharide becomes extremely low. Attempts to demonstrate the reversibility of the reaction by showing a formation of sucrose in the reaction medium when the enzyme is incubated with fructose and dextran... 

Homopolysaccharides are synthesised by relatively few spedfic enzymes and are not constructed from subunits. The commerdally important homo polymer dextran is synthesised extracellularly by the enzyme dextransucrase. In Leuconostoc mesenteroides the enzyme is induced by the substrate sucrose. This is deaved to release free fructose and link the glucose to the redudng end of the acceptor dextran chain, which is bound to the enzyme. The product from this bacterium is composed almost exdusively of... 

Polarimetric determination of the sucrose concentration of a solution is valid when sucrose is the only optically active constituent of the sample. In practice, sugar solutions are almost never pure, but contain other optically active substances, most notably the products of sucrose inversion, fructose and glucose, and sometimes also the microbial polysaccharide dextran, which is dextrorotatory. Corrections can be made for the presence of impurities, such as invert, moisture, and ash. The advantage of polarization is that it is rapid, easy, and very reproducible, having a precision of 0.001°. 

The formation of dextran was first observed as a troublesome slimy product in sugar manufacturing. The enzyme dextran saccharase produced by bacteria only affects saccharose and liberates fructose with dextran formation. A primer of the kind used in the amylose synthesis is not required. In the formation reaction, a very stable complex SEPi, is formed from the enzyme EPn binding to the dextran polymer and the saccharose S. This then decomposes to form fructose F ... 

G6. Separation of ternary mixture with a feed consisting of dextran, fructose and a heavy inpurity. A... 

The composition, particularly the molecular weight, is affected by the temperature of the medium, concentrations of sucrose and fructose, and by the addition of primers, such as low-molecular-weight dextrans or maltose ISO). Periodate techniques (p. 700) have been particularly valuable for rapid analyses of these substances. 

Howard et al studied the antibody response of High and Low lines to native levan (mol. wt. 2 x 10 ) and native dextran (mol. wt. 8 x 10. The specificities of these antigens are respectively determined by /J 2-6-linked fructose and a -3-linked glucose. As Sill, levan and dextran are T independent antigens eliciting the synthesis of only IgM antibody in the mouse but unlike Sill, levan and dextran produce equivalent antibody response in High and Low lines (Figure 5.20). 

A reducing disaccharide, composed of D-glucose and D-fructose and named leucrose was isolated in 7.9% yield from the reaction mixture produced by the synthesis of dextran from sucrose by an enzyme from Leuconosioc mesenteroides NRRLB-512A. Methylation and other evidence showed that this disaccharide is 0-a-D-glucopyranosyl-(i -> 5)-fructop5n anose. 

The selective separation range of P-6/S-200 was determined with Blue Dextran (Vexdi exclusion limit) and fructose (V,o total permeation limit). Molecular weight (degree of polymerization) calibration (Fig. 16.22) was established with dextran standards and low dp pullulans (dp 3, 6, 9, 12, 15, 18) formed by the controlled hydrolysis of high dp pullulan. 

Some antigens, such as type 3 pneumococcal polysaccharide, EPS and other polymeric substances such as dextrans (poly-D-glucose) and levan (poly-D-fructose) can induce antibody synthesis without the assistance of TH cells. These are known as T-independent (Ti) antigens. Only one class of immunoglobulin (IgM) is synthesized and there is a weak memory response. 

Bacterial cellulose, dextran and many other bacterial polysaccharides are composed entirely of D-glucose units the levans are condensation polymers of D-fructose. Dextrans from different species of Leuconostoc... 

In the presence of such weak acceptors as fructose, initial overall reaction rates decrease significantly with increasing concentration of acceptor, whereas they increase with the substrate concentration. Initial rates of acceptor-product formation increase with both substrate and acceptor formation, the formation of dextran being... 

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