Abstract
Increasing the reaction time or the temperature, or decreasing the enzyme or sucrose concentration, produced dextrans with higher molecular weights (light scattering) and lower intrinsic viscosities. This was consistent with the results of periodate titrations, which indicated that under these conditions the degree of branching of the samples was increased. The increase in branching which occurs when the reaction time is increased or the sucrose concentration is decreased may be due to the resulting increase in the ratio of acceptor sites for branching (chain glucose units) to the number of sucrose molecules. In addition, as the molecule grows larger with increasing reaction time, an increase in steric factors would reduce the availability of the reducing end of the chain. After allowance has been made for the change in the steric factor, it seems that the effect of enzyme concentration on branching is negligible, but that a decrease in the temperature decreases the degree of branching. The effect of temperature on the velocity of synthesis corresponds to an Arrhenius activation energy of 10.6 kcal./mole.