Gelling mechanism and interactions of polysaccharides from Mesona blumes: Role of urea and calcium ions.
In this study, the relaxation modulus was used to elucidate the gelling mechanism of polysaccharides from Mesona blumes. The pH of Mesona blumes polysaccharides (MBP) was adjusted could significantly change the relaxation modulus of MBP. The results showed that the hydrogen bonds and electrostatic interaction existed in during the formation of MBP gel. The addition of salt ions (sodium ions and calcium ions), EDTA and urea have different effects on the relaxation modulus of MBP. Result showed that the hydrogen bond was the main force maintaining the MBP gel network structure, followed was calcium ions. And electrostatic interaction was not the decisive role of gel formation. The small molecules with active hydrogen-bond donors and/or acceptors were added into MBP, which proved -COOH was involved in the hydrogen bonds formation of MBP gel. In addition, the entanglement network number (ENN) results quantitatively assessed contribution of interaction: hydrogen bonds interaction > calcium ions (calcium bridge) >electrostatic interaction.