Volume 125, Issue 9, 07 September 2006
Index of content:
125(2006); http://dx.doi.org/10.1063/1.2336425View Description Hide Description
The solvent effect on reactions in solutions is crucial for many systems. In this study, the reaction barrier with respect to the number of solvent molecules included in the system is systematically studied using density functiontheory calculations. Our results show that the barriers rapidly converge with respect to the number of solvent molecules. The solvent effect is investigated by calculating cisplatin hydrolysis in several types of solvents. The results are analyzed and a linear relationship between the reaction barrier and the interaction strength of solvent–reactants is found. Insight into the general solvent effect is obtained.
125(2006); http://dx.doi.org/10.1063/1.2238870View Description Hide Description
This Communication describes a mechanism to explain antifreeze protein’s function to inhibit the growth of ice crystals. We propose that the adsorption of antifreeze protein (AFP) molecules on an icesurface induces a dense AFP-water layer, which can significantly decrease the mole fraction of the interfacial water and, thus, lower the temperature for a seed ice crystal to grow in a super-cooled AFP solution. This mechanism can also explain the nearly unchanged melting point for the ice crystal due to the AFP’s ice-surface adsorption. A mathematical model combining the Langmuir theory of adsorption and the colligative effect of thermodynamics has been proposed to find the equilibrium constants of the ice-surface adsorptions, and the interfacial concentrations of AFPs through fitting the theoretical curves to the experimental thermal hysteresis data. This model has been demonstrated by using the experimental data of serial size-mutated beetle Tenebrio molitor (Tm) AFPs. It was found that the AFP’s ice-surface adsorptions could increase the interfacial AFP’s concentrations by 3 to 4 orders compared with those in the bulk AFP solutions.
125(2006); http://dx.doi.org/10.1063/1.2349476View Description Hide Description
The hydroperoxyl radical has long been considered as a prototype for statistical vibrational dynamics. In this work, however, it is shown that the bound state energy levels (up to the dissociation threshold) and low-lying resonances of the system obtained on a new ab initiopotential energy surface exhibit surprisingly large regularity. The implications of the non-statistical behavior of the system in unimolecular and bimolecular reactions are discussed.