Observation of Entropic Effect on Conformation Changes of Complex Systems Under Well-Controlled Temperature Condition

Journal Article · Thu Jan 17 04:00:00 EST 2008 · Journal of Physical Chemistry A, 112(2):172-175

DOI:https://doi.org/10.1021/jp711205z· OSTI ID:928274

Wang, Xue B; Yang, Jie; Wang, Lai S

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 Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 928274
• Report Number(s): PNNL-SA-57552; 21790; 25395; KC0301020
• Journal Information: Journal of Physical Chemistry A, 112(2):172-175, Journal Name: Journal of Physical Chemistry A, 112(2):172-175 Journal Issue: 2 Vol. 112
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
59 BASIC BIOLOGICAL SCIENCES
CARBOXYLIC ACID SALTS
CONFORMATIONAL CHANGES
ENTHALPY
ENTROPY
Environmental Molecular Sciences Laboratory
HYDRATION
KINETICS
PHOTOELECTRON SPECTROSCOPY
SOLVATION
SOLVENTS
TEMPERATURE CONTROL
TEMPERATURE DEPENDENCE