Dextran phosphate, preparation

The preparation of dextran phosphate (Fig. 9) is simply achieved by treatment of the polysaccharide with polyphosphoric acid in formamide yielding products with up to 1.7% phosphorus. 

Suzuki M, Mikami T, Matsumoto T, Suzuki S (1977) Preparation and antitumor activity of O-palmitoyldextran phosphates, O-palmitoyldextrans, and dextran phosphate. Carbohydrate Res 53 223-229... 

M. Suzuki, T. Mikami, T. Matsumoto, and S. Suzuki, Preparation and Antitumor Activity of 6>-Palmitoyldextran Phosphates, 0-Palmitoyldextrans, and Dextran Phosphate, Carbohydr. Res. 53 ... 

To make an amine derivative of dextran, dissolve ethylene diamine (or another suitable diamine) in 0.1 M sodium phosphate, 0.15 M NaCl, pH 7.2, at a concentration of 3 M. Note Use of the hydrochloride form of ethylene diamine is more convenient, since it avoids having to adjust the pH of the highly alkaline free-base form of the molecule. Alternatively, to prepare a hydrazide-dextran derivative, dissolve adipic acid dihydrazide (Chapter 4, Section 8.1) in the coupling buffer at a concentration of 30 mg/ml (heating under a hot water tap may be necessary to completely dissolve the hydrazide compound). Adjust the pH to 7.2 with HC1 and cool to room temperature. 

Fig. 9 Preparation of dextran phosphoric acid esters (phosphates) with polyphosphoric acid...

In addition, esters of dextran-bearing palmitoyl groups and phosphate functions can be used for the preparation of specifically modified liposomes, which are exploited for the entrapment of peptides such as hirudin, the most potent inhibitor of thrombin [105]. 

It had a degree of esterification of 73 and was labeled 73G. Characterization and preparation of samples were as reported previously (5) with minor modification. Samples to be neutralized with NaOH were dissolved in 0.01 M phosphate buffer (pH 6.1) containing 0.1 M EDTA, titrated to pH 7 with 0.1 M NaOH, dialysed against four changes of water over 48 hr., centrifuged for 1 hr. at 30,000 x g to remove insoluble matter and then lyophilized. Protonated samples were dissolved in deionized water (Continental Water Systems) followed by dialysis, centrifugation, and lyophillization weight cut off of 12,000. Dextran standards were from Pharmacia... 

Figure 4 Thermal stability of lysozyme-polysaccharide conjugates. O, lysozyme , lysozyme-dextran conjugate , lysozyme-galactomannan conjugate. Lysozyme-polysaccharide conjugates were prepared by dry heating at 60°C for 2 weeks. Sample solutions (0.1%) in 67 mM phosphate buffer (pH 7.4) were heated at an increasing rate of l°C/min. The resulting turbidity was measured with the absorbance at 500 nm.

The glucose-sensitive dispersions were prepared by slowly mixing 0.5 ml of a phosphate-buffered solution (8 mM, pH 7.3, 0.9 % NaCl, 0.05 % NaNs) of ConA (22mg/ml) to 0.5 ml of a solution containing Rhodamine-labeled dextran (2,000 kDa, 12 mg/ml). The colored dextran makes the spot easily visible for size determination. 

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