AGAROSE GELS - EFFECT OF SUCROSE, GLUCOSE, UREA, AND GUANIDINE-HYDROCHLORIDE ON THE RHEOLOGICAL AND THERMAL-PROPERTIES

The effect of sucrose, glucose, guanidine hydrochloride, or urea on the dynamic elastic modulus E' and mechanical loss tangent and on the differential scanning calorimetry (DSC) curves of agarose gels were examined. E' increased with increasing concentration of sugars up to a certain amount, but the excessive addition of sugars decreased E'. The DSC endothermic peak accompanying the transition from gel to sol shifted to higher temperatures, while the heat absorbed on forming 1 mol of junction zones increased and then decreased with increasing sugar concentration. Guanidine hydrochloride or urea decreased E' and shifted the gel to sol transition temperature to lower temperatures. The mechanism by which these chemical reagents weaken or strengthen the gel-forming ability was discussed. © 1990, American Chemical Society. All rights reserved.