Kinetic inhibitors trehalose

The result obtained by the transmission electron microscope observations of the freeze-fracture replica on trehalose solutionssuggested that the ice-crystal nucleation is enhanced in the solution with higher trehalose concentration. Based on these experimental results and assuming a similar nucleation process between ice and clathrate hydrates, we can speculate that trehalose, as a kinetic inhibitor, may not inhibit the nucleation but may work as an anti-agglomerant, keeping small hydrate particles dispersed as they form. 

Another possible mechanism of trehalose molecules as a kinetic inhibitor is mentioned below. In the growth process of CO2 hydrate, trehalose may work as the kinetic inhibitor that prevents the rate-determining process of the crystal formation at the reaction site which might have small dependence on AT. Trehalose has been observed to prevent ice-crystal growth with the reduction of the free-water providing because trehalose strongly hydrated in the solution. This effect is found apparently when the trehalose concentration increases beyond the intrinsic hydration number of trehalose molecules. It is thus reasonable that the kinetic effect of trehalose on the inhibition of the hydrate formation would be resulted from the smaller supplement of free water from the solution of higher trehalose concentrations. 

The inhibition effects of type-III AFP and trehalose, two cryoprotecting materials produced in animals, on type-I CO2 clathrate-hydrates were examined. For comparison with the results of a previous study in which the lateral growth rates of COi-hydrate film were dependent on temperature, pressure and NaCl concentration, the solution droplet was observed in a high pressure vessel filled with CO2. Type-III AFP was found to increase the induction period and to reduce the lateral growth rate of C02-hydrate films. It worked well at low concentrations, indicating that AFP works as a kinetic inhibitor. It was also indicated that AFP would weaken the memory effect of C02-hydrate formation. Trehalose had similar inhibition effects on both the induction period and the lateral growth rate, but it had little apparent concentration-dependence on them. Since trehalose also causes the equilibrium conditions of the CO2 hydrate to shift to lower temperatures, it works not only as a thermodynamic inhibitor but also as a kinetic inhibitor, especially as an anti-agglomerant. 

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