Effect of water potential on sol–gel transition and intermolecular interaction of gelatin near the transition temperature

Abstract

The sol-gel transition of gelatin, measured by thermal analysis and viscosity measurement, was analyzed in terms of the change in hydration state of polymer molecules. A new thermodynamic model was proposed in which the effect of water potential is explicitly taken into account for the evaluation of the free energy change in the sol-gel transition process. Because of the large number of water molecules involved and the small free energy change in the transition process, the contribution of water activity, a(W), was proved to be not negligible in the sol-gel transition process in solutions containing such low-molecular cosolutes as sugars, glycerol, urea, and formamide. The gel-stabilization effect of sugars and glycerol was linear with a(W), which seemed consistent with the contribution of water potential in the proposed model. The different stabilization effect among sugars and glycerol was explained by the difference in solvent ordering, which affects hydrophobic interaction among protein molecules. The gel-destabilization effect of urea and formamide could be explained only by the direct binding of them to protein molecules through hydrogen bonding. On the contrary, the polymer-polymer interaction, measured by the viscosity analysis, in polyethyleneglycol and dextran solutions was not sensitive to the change in a(W), suggesting that no substantial change in hydration state with a(W) occurred in these polymer solutions.

3D cell entrapment in crosslinked thiolated gelatin-poly(ethylene glycol) diacrylate hydrogels

“…Temperature effects were investigated via a dynamic frequency sweep at 37 °C and results showed G ′ values at 37 °C were lower than values obtained at R.T for both covalently and physically crosslinked gelatin hydrogels. The decrease of shear storage modulus at higher temperature may be explained by the sol-gel transition of gelatin, which involves triple helix to protein coil transition [36]. The unfolding of triple helices in the gelatin backbone may result in the gelatin chain relaxation at higher temperature and hence, in decreased hydrogel mechanical strength.…”

UCST‐type phase transition driven by protein‐derived polypeptide employing gelatin and chitosan

“…It was envisaged that the phase transition of the G/C complex would respond to the addition of a denaturant if it were governed by the secondary structure transition of gelatin. A variety of different additives have been reported to denature proteins by weakening their hydrophobic bonding interactions through the formation of disruptive hydrogen bonding or ionic interactions with the protein . Urea has been widely used as a protein denaturant in this regard, because it can interact directly with proteins through the formation of hydrogen bonds.…”

Thermodynamic analysis of sol–gel transition of gelatin in terms of water activity in various solutions

“…Therefore, the sol–gel transition is inevitably accompanied with a large change in the intra‐ and intermolecular hydrogen‐bonding involving a large change in the hydration state of the protein . Because of the large number of water molecules involved in this process, we pointed out the importance of the water potential, or water activity, in the sol–gel transition of gelatin in solutions with cosolutes …”