Degree of derivatization

Since the active ester end of the molecule is subject to hydrolysis (half-life of about 20 minutes in phosphate buffer at room temperature conditions), it should be coupled to an amine-containing protein or other molecule before the photolysis reaction is done. During the initial coupling procedure, the solutions should be protected from light to avoid decomposition of the phenyl azide group. The degree of derivatization should be limited to no more than a 5- to 20-fold molar excess of sulfo-SBED over the quantity of protein present to prevent possible precipitation of the modified molecules. For a particular protein, studies may have to be done to determine the optimal level of modification. 

In the section discussing Diels-Alder cycloadditions, it was shown how this reaction can be exploited as a way to link polymeric chains to the nanotube sidewalls. Attachment of polymers to carbon nanotubes is an important possibility for the chemistry of nanotubes as even low degrees of derivatization considerably enhance their solubility. 

The labelled polyacrylic acid PAA-M, used for polarized luminescence measurements, was prepared by grafting of 9-aminoacridine on the PAA-800 000 chain (15). The degree of derivatization of the polyacid (evaluated from the UV-vis spectra of PAA-M And 9-aminoa-cridine) is very low ... 

These results indicate that, under partial derivatization, the chemical nature of the derivatized end group is not critical to anticoagulant activity within the limited number of derivatizing agents tested however, the degree of derivatization is critical. Furthermore, both carboxylic and hydroxyl heparin groups can be utilized in heparin surface coupling reactions. 

Figure 3. Degree of derivatization of dextran activation with CDI...

After activation of dextran with different concentrations of CDI, DTPA NH2 was coupled to the activated dextran, as shown in the scheme of Fig 4. Four samples were prepared and, in order to obtain higher degrees of derivatization of the dextran with DTPA-NH2, the CDLdextran ratio was extended to 1.5. 

Figure 5. IH NMR spectrum of Dextran-DTPA-NH2 with a degree of derivatization of 71% in DjO+NaOD at 25 C, pH 7.0...

Figure 6. Degree of derivatization of Dextran>DTPA>NH2 by reacting with different molar ratios of CDI/dextran (glucose equivalents) A - 15%, B - 20%, C - 45% and D - 71%...

Many starch derivatives are prepared in a manner similar to cellulose modification. Both heat and alkali ate often used to prepare the starch for chemical addition. As with cellulose, the properties of the starch change with the degree of derivatization. The final characteiisties of the modified gums are controlled by factors which include (a) the amylose/amylopectin content, (b) the degree of modification, (c) the degree of derivatization, and (d) the type of derivatization. This range of factors can result in wide varieties of different gums. 

Rrfi-ONa + CICH COOH R n-OCHjCOOH + NaCl Swells and dissolves in basic water where the degree of derivatization of the caiboxymethyl group is over 0.3. When it is over 0.4, it dissolves and swells in water. 

The normal chain polymer is obtained in the form of sodium salt that is a normal hygroscopic white solid that absorbs humidity. The properties change according to the degree of the derivatization of the caiboxymethyl group. When the degree of derivatization is over 0.3, it is acidic and it precipitates, but those that are acidic and are between 0.5-0.8 will not precipitate, but will precipitate in alcohol. 

It has unique application due to low cost because it dissolves faster with degree of derivatization than carboxymethyl cellulose... 

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