Immunochemical studies on dextrans: microheterogeneity of dextran NRRL B1397 demonstrated by precipitation with concanavalin A

Electromigration behavior of polysaccharides in capillary electrophoresis under pulsed-field conditions

Various polysaccharides can successfully migrate through entangled polymer solutions during high-voltage capillary electrophoresis. For neutral polysaccharides, complexation with borate provides the electric charge needed for electromigration, while a fluorescent tag is needed to detect the solute bands with adequate sensitivity. At constant potentials between 50 and 300 V/cm, the charged polysaccharides undergo molecular stretching, resisting the desired separation according to their molecular mass. This problem can be overcome through the use of variable fields, pulsed along the separation capillary at a 180 degree angle. Variables of the pulsing experiment appear to have a profound influence on molecular shape rearrangements of polysaccharides with respect to the separation medium, as demonstrated here with highly efficient separations of polydextrans (8,000-2,000,000 Da).

Preparation of a non-immunogenic arginase by the covalent attachment of polyethylene glycol

Methoxypolyethylene glycol of 5000 daltons (PEG) was attached covalently to bovine liver arginase using 2,4,6-trichloro-s-triazine as the coupling agent. The conjugate (PEG-arginase), with PEG attached to 53% of the amino groups, retained 65% of its original enzymatic activity. Mice were injected intravenously with arginase or PEG-arginase for periods of one to three months. The blood-circulating life of PEG-arginase was greatly extended over that of arginase. The half-life of injected arginase at day 30 was less than 1 h, whereas that of the PEG-enzyme was 12 h. Antisera from mice injected with native arginase reacted against arginase but not against PEG-arginase when tested by immunodiffusion. Antisera from animals injected with PEG-arginase reacted neither with native arginase nor PEG-arginase. The data indicate that arginase modified by PEG has been rendered both non-immunogenic and non-antigenic when tested in mice. The injection of PEG-arginase into mice did not induce tolerance toward the native enzyme. Injected PEG-arginase, in the presence of precipitating antibody directed against native arginase, circulated at the same level as in virgin animals. The attachment of PEG to arginase altered its kinetic properties.