Dextran sulfate solution preparation

Figure 7.16 Dependence on tlie polysaccharide concentration CDS of (a) tlie second virial coefficient A2 and (b) tlie stmcture-sensitive parameter p of complexes of sodium caseinate + dextran sulfate , complexes prepared in bulk solution a, complexes prepared at tlie interface in a protein-stabilized foam , sodium caseinate alone. Reproduced from Semenova et al. (2009) with permission.

A hydrogel with high sensitivity was prepared with chitosan (DA = 0.18) and dextran sulfate the maximum volume of the complex gel was observed in a dilute NaOH solution at pH 10.5, and was about 300 times as large as the volume at pH values below 9 [106,107]. 

Fig. 7A—C. Biochemo-mechanical function of NIPA gel with immobilized concanavalin A (A) Schematic illustration of saccharide-responsive, reversible swelling of a NIPA gel loaded with concanavalin A. Na DS"- is dextran sulfate sodium (DSS). (B) Temperature dependence for equilibrated volume of NIPA gel including the Con A-DSS complex (DSS-gel, O), MP (MP-gel, ), and free of both DSS and MP (A). The latter was prepared as a control sample as described in the text except for the use of an aqueous Con A solution instead of the Con A-DSS solution. Hysteresis was observed in the volume changes of the MP-gel and free-Con A gel on heating and cooling, indicating a discontinuous phase transition. The diameter of each gel in the collapsed state, determined at 50 °C, was d0 = 0.074 mm the volume of this gel is denoted Vp. The concentration of dry matter in the collapsed state was estimated from the preparation recipe to be 90 wt%. (C) Repeated swelling/shrinking control at 34.5 °C by alternate binding of DSS and MP to gel-entrapped Con A. (E. Kokufuta, Y.-Q. Zhang and T. Tanaka [78])...

It is convenient to prepare a stock hybridization solution containing 5 ml formamide, 1.5 ml 20x SSC, and 1 g dextran sulfate made to a volume of 9.0 ml with distilled water. The dextran sulfate will take a while to dissolve. This solution can be stored at 4°C and used for at least several months. To 36 /u.1 of this solution up to 4 p of probe(s) can be added. The volume is made up to 40 jul with water, and all the components are then at the right concentration. 

Add the probe(s). Make up probes in hybridization solution (3x SSC/ 50% formamide/10% dextran sulfate) as in Protocol IV.A, step 6. For each sample prepare 11-15 /xl of hybridization solution containing 20-200 ng of each probe. 

To check hybridization probes on mitotic or polytene squash preparations, we use a procedure similar to that described by Pardue (1986,1994). After the slides are denatured with sodium hydroxide and dehydrated, the denatured probe is applied in the same solution as is used in the hybridization protocols above (3X SSC/50% formamide/10% dextran sulfate), and the same annealing temperature is also used so as to make the annealing conditions as similar as possible to whole-mount experiments. We have found it possible to eliminate both RNase treatment and acetylation steps from traditional procedures with no increase in fluorescent background. 

In order to reduce the interaction of dextran with blood components, the negatively charged dextran sulfate (DS) was used to prepare polyelectrolyte complexes (PECs) together with cationic natural or synthetic polymers, such as chitosan or PEI. PECs can be synthesized by direct interaction of oppositely charged polyelectrolytes in solution. In PECs, the outer coat of dextran sulfate minimizes electrostatic interactions, while the inner posi-... 

Prepare the hybridization mix. The volume required depends upon the number of slides to be hybridized Use 5-10 iL of hybridization mix per cm of tissue section, or 50 pL per slide covered by a 24 x 50-mm cover slip (see Note 22). For 2 mL hybridization mix, combine. 1 mL of deionized formamide, 400 pL of 50% dextran sulfate, 200 pL of lOX salts solution, 20 pL of 1M DTT, 100 pL of 10 pg/pL yeast tRNA, 180 pL of distilled water. Note that this recipe allows for the volume of the probe (l/20th of the final volume of the hybridization mix) to be added in step 3 (see Note 23). 

The presence of three hydroxyl groups per glucose unit was shown by the preparation of a triacetate and a tribenzoate. Six or seven methyla-tions (using dimethyl sulfate and concentrated alkali) of dextran did not raise the methoxyl content above 41% (theoretical maximum 45.6%). Also, Purdie methylations (using methyl iodide and silver oxide) and methylation with thallium ethoxide and methyl iodide were ineffective in raising the methoxyl content of methylated dextran above 43.5%. The maximum theoretical methoxyl content was eventually attained by modified Muskat methylations. 6 Partially methylated dextran suspended in anisole solution was treated with sodium in liquid ammonia, and the sodium salt of methylated dextran thus formed was allowed to react with methyl iodide. The methoxyl content of the partially methylated dextran was raised by three such methylations from 42% to 45.5% and by five such methylations from 30% to 45.4%. 

The complex-formation of polysaccharides with alkali metals and alkaline-earth metals has already been discussed in this Series. A dextran-iron complex has been used in the experimental therapy of synovitis, and chondroitin sulfate-iron colloids have been prepared. The swelling of cellulose in aqueous solutions of zinc chloride depends on the formation of a complex with the vicinal 2- and 3- hydroxyl groups of the repeating unit. ... 

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