Low-Barrier Hydrogen Bond in Fujikurin A-D: A Computational Study

Area of Science:

• * Computational Chemistry
• * Molecular Dynamics
• * Quantum Chemistry

Background:

• * Fujikurin A, B, and D compounds from *Fusarium fujikuroi* exhibit intramolecular low-barrier hydrogen bonds (LBHBs).
• * These LBHBs feature a proton that appears to rapidly switch between two states via a transition state (TS).

Purpose of the Study:

• * To investigate the detailed characteristics of intramolecular LBHBs in Fujikurin compounds.
• * To understand the role of nuclear quantum effects (NQEs) on proton transfer dynamics.

Main Methods:

• * Path integral molecular dynamics (PIMD) simulations were employed.
• * PIMD simulations considered nuclear quantum effects (NQEs) at finite temperatures.

Main Results:

• * PIMD simulations predicted the complete elimination of the energy barrier for proton transfer due to NQEs.
• * The effective free-energy potential surface showed a single-well shape for proton distribution.

Conclusions:

• * The hydrogen-bonded proton in Fujikurin does not transfer between two distinct equilibrium structures.
• * Protons are widely delocalized around a global minimum structure that includes the TS region.