Observation of Entropic Effect on Conformation Changes of Complex Systems Under Well-Controlled Temperature Condition
We report direct observation of entropic effect in determining the folding of a linear dicarboxylate dianion with a flexible aliphatic chain [–O2C-(CH2)6-CO2–] by photoelectron spectroscopy as a function of temperature (18 – 300 K) and degree of solvation from 1 to 18 water molecules. A folding transition is observed to occur at 16 solvent water molecules at room temperature, but at 14 solvent molecules below 120 K due to the entropic effect. The –O2C-(CH2)6-CO2–(H2O)14 hydrated cluster exhibits interesting temperature-dependent behaviors and its ratio of folded over linear conformations can be precisely controlled as a function of temperature, yielding the enthalpy and entropy differences between the two conformations. A folding barrier is observed at very low temperatures, resulting in kinetic trapping of the linear conformation. The current work provides a simple model system to study the dynamics and entropic effect in complex systems and may be important for understanding the hydration and conformation changes of biological molecules.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 928274
- Report Number(s):
- PNNL-SA-57552; 21790; 25395; KC0301020; TRN: US200815%%729
- Journal Information:
- Journal of Physical Chemistry A, 112(2):172-175, Vol. 112, Issue 2
- Country of Publication:
- United States
- Language:
- English
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