Gelation mechanism of agarose

The non-Newtonian behavior and dynamic viscoelasticity of a series of aqueous solutions of agarose were measured with a rheogoniometer. The flow curve, at 25 degrees, of agarose solution approximated to plastic behavior at 0.1,0.13, and 0.15% concentrations. Gelation occurred at concentration of 0.13% at low temperature (0 degrees). The dynamic modulus of agarose showed a very high value at low temperature, and increased with an increase in temperature, showing a maximum value at 30 degrees, then it decreased. In the presence of NaCl, KCl, CaCl2, and MgCl2 for a solution of agarose at 0.08% concentration, the transition temperature, at which dynamic modulus decreased rapidly, was observed at 60 degrees. Gelation was also observed at low temperature (0 degrees) in acid and alkaline range after reaching pH values of 2.3 and 9.5, respectively, by addition of 100mM HCl, H2SO4, NaOH, and Ca(OH), to a 0.08% agarose solution. A possible mode of intra-and inter-molecular hydrogen bonding within and between the agarose molecules in aqueous solution is proposed.