Coupled to dextran

Brunswick, M., Finkelman, F.D., Higher P.F., Inman, J.K., Dintzis, H.M., and Mond, J.J. (1988) Picogram quantities of anti-Ig antibodies coupled to dextran induce B cell proliferation. /. Immunol. 140, 3364-3372. 

Brunswick M, Finkelman FD, Highet PF, Inman JK, Dintzis HM, Mond JJ. Picogram quantitites of anit-lg antibodies coupled to dextran induce B-cell proliferation. J. Immunol. 1988 140 3364— 3372. 

The electrochemical detection utilized the re-oxidation of hexacyano-ferrate(II) on a platinum electrode. For pyruvate determination this assay was extended to a 3-enzyme system by the addition of glutamate p5u-uvate transaminase, which produces alanine from pyruvate. All enz5unes were used in solution in a reaction chamber of approximately 2 pi directly in front of the electrode. The cofactor NAD" " was coupled to dextran with a molecular weight of 40,000 to avoid its replacement for each assay. As the sensor responded to L-alanine and pyruvate again a differential measurement was required when a sample contained both compounds. It was applied to off-line monitoring of a cultivation of S. cerevisiae and data showed good correlation to the photometric assays. 

In this way, penicillin G amidase was first coupled to dextran (see below) with the modified enzyme showing significantly increased thermostability, and this preparation was then immobilized on amino-activated silica gels [49]. 

Detection of heavy metals was demonstrated by Wu et al. who used a Bi-acore X instrument (Biacore AB, Sweden) with rabbit metallothinein coupled to dextran matrix on the sensor chip [48]. Metallothinein is a protein that can be found in the cells of many organisms and is known to bind to metals (especially cadmium and zinc). Model experiments in which metallothein was used as a receptor demonstrated the potential of this sensor to directly detect Cd, Zn, and Ni in buffer at concentrations down to 0.1 jigmL . ... 

The preparation of the DTPA derivative for coupling to dextran was carried out by three steps, as shown in Fig. 1. 

In this study we have demonstrated a particular example of a sensor system, which combines catalytic activity for the substrate (urea) and at the same time enabling to monitor the enzymatic reaction by co-encapsulated pH sensitive dye. Substrate sensitive enzyme urease was co-encapsulated together with SNARF-1 coupled to dextran in multilayer tnicrocapsules. Enzymatic activity was recorded by fluorescent changes caused by increasing of pH in course of enzymatic cleavage of urea as measured on... 

Nicotinamide adenine dinucleotide+-A -[A-(6-aminohexyl)acetamide] has been coupled to dextran cyclic imidocarbonate with a view to incorporating the immobilized coenzyme, as a cofactor, into a multi-enzyme electrode and model enzyme reactors. ... 

HEMA-lactate-CI (5) is coupled to dextran (7) to yield dex-laetateHEMA (8) (Fig. 8). A comparable dextran derivative without lactate spacer between the methacrylate ester and dextran was also synthesized. For this compound, HEMA was activated with CDl, and the resulting HEMA-Cl (9) is then coupled to dextran, yielding dexHEMA (10) (Fig. 9). 

A suitable degree of esterification of dextran with butyric or palmitic acid is achieved by CDI in formamide or DMSO. In the absence of carboxylic acids dextran can be converted by CDI into a crosslinked product with intrachain as well as interchain carbonate links. Such carbonate links permit drugs containing hydroxyl groups to be coupled to the dextran.[174]... 

Even though the short oligosaccharide segment made of seven units may not be considered as a true polymer chain, the chemistry devised by them should be easily applicable to longer saccharidic chains. Liu and Zhang used the Michael reaction for coupling a dextran (Dex) with an amino-functionalized terminal and acrylolyl end-capped PCL [146]. Sun et al. also synthesized Dex-b-PCL by disulfide bond formation [147]. 

The hydroxylic content of the dextran sugar backbone makes the polymer very hydrophilic and easily modified for coupling to other molecules. Unlike PEG, discussed previously, which has modifiable groups only at the ends of each linear polymer, the hydroxyl functional groups of dextran are present on each monomer in the chain. The monomers contain at least 3 hydroxyls (4 on the terminal units) that may undergo derivatization reactions. This multivalent nature of dextran allows molecules to be attached at numerous sites along the polymer chain. 

Add 10 mg of the protein to be coupled to the dextran solution. Other ratios of dextran-to-protein may be used as appropriate. For instance, if more than one protein or a protein plus a smaller molecule are both to be conjugated to the dextran backbone, the amount of protein added initially may have to be scaled back to allow the second molecule to be coupled latter. Many times, a small molecule such as a drug will be coupled to the dextran polymer first, and then a targeting protein such as an antibody conjugated secondarily. The optimal ratio of components forming the dextran conjugate should be determined experimentally to obtain the best combination possible. 

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