Thermodynamics and Kinetics of a Partial Peptide of K+ Channels: DFT Transition State Calculations Coupled with Temperature-Controlled Gas Phase Laser Spectroscopy
英文:
Thermodynamics and Kinetics of a Partial Peptide of K+ Channels: DFT Transition State Calculations Coupled with Temperature-Controlled Gas Phase Laser Spectroscopy
著者
和文:
Yukina Suzuki,
Keisuke Hirata,
James M. Lisy,
Shun-ichi Ishiuchi,
Masaaki Fujii.
英文:
Yukina Suzuki,
Keisuke Hirata,
James M. Lisy,
Shun-ichi Ishiuchi,
Masaaki Fujii.
K+ channels selectively conduct K+ at a high conduction rate, but not smaller Na+ and Li+. To provide an insight into the conduction mechanism previously, we experimentally observed the temperature dependence of the conformer distributions of a model peptide in K+ channels (Ac-Tyr-NHMe) complexed with alkali metal ions (Li+, Na+, K+, Rb+, and Cs+) by gas phase laser spectroscopy. The K+ and Rb+ complexes showed a more significant temperature dependence than the Li+ complexes, whose conformer distributions barely varied. This different behavior with temperature can be interpreted either thermodynamically (entropy vs. enthalpy) or kinetically (barrier height). Due to the lack of temperature dependence of the Li+ complex, we could not determine which factor, an enthalpy-driven structure or a high energy barrier, governs the Li+ complex?s behavior. To resolve this issue, we carried out DFT transition state calculations and time-dependent simulation of the metal complexes? conformer distributions based on the theoretical barrier heights. By comparing the experimental and computational data, the origin of the variation in the temperature dependence among different ion complexes was determined to be thermodynamic.
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