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

Abstract

The compounds Fujikurin A, B, and D, recently isolated from Fusarium fujikuroi , possess intramolecular low-barrier hydrogen bonds (LBHBs), which are hydrogen bonds with a very low-energy barrier for proton transfer. The isolated compounds have a hydrogen-bonded proton that appears to rapidly switch between two equilibrium states via a transition state (TS). To understand the characteristics of these intramolecular LBHBs in detail, we performed path integral molecular dynamics (PIMD) simulations, which can consider nuclear quantum effects (NQEs) under a finite temperature. The PIMD simulations predicted that the NQE completely washed out the energy barrier for the proton transfer reaction. Consequently, a single-well shape emerged in the results, along with the effective free-energy potential surface for the hydrogen-bonded proton distribution. Thus, we conclude that the hydrogen-bonded proton in Fujikurin does not in fact transfer between two equilibrium structures but widely delocalizes around the global minimum structure involving the TS region.

Nuclear quantum and H/D isotope effects on aromaticity: path integral molecular dynamics study

“…For example, several groups and we have reported that NQEs of hydrogen nuclei enhance the hydrogen bond strength and facilitate proton transfer reactions. 19–24 Furthermore, we have also demonstrated that considering the NQEs is indispensable for the analysis of the H/D isotope effects. 24…”

Nuclear quantum and H/D isotope effects on intramolecular hydrogen bond in curcumin

“…We have already demonstrated that the NQE should be considered for the quantitative analysis of LBHB systems. 11–14 For such systems, CLMD results without NQE occasionally differ completely from PIMD results. In particular, the proton distributions obtained through CLMD and PIMD simulations should be quite different.…”

Location of the Shared Proton in Proton-Bound Dimer Compound of Hydrogen Sulfate and Formate: Path Integral Molecular Dynamics Study

“…Since the PIMD simulations use MD simulation to calculate the statistical average, the PIMD simulations can take not only the NQEs but also thermal effects into account. Many research groups have investigated hydrogen-bonded systems with the aid of PIMD method, 22−30 to analyze the stationary point structures of the LBHB systems [22][23][24]29 at the finite temperature. Therefore, we decided to conduct a PIMD simulation on the PBD compound of hydrogen sulfate and formate in this study.…”

“…Since the PIMD simulations use MD simulation to calculate the statistical average, the PIMD simulations can take not only the NQEs but also thermal effects into account. Many research groups have investigated hydrogen-bonded systems with the aid of PIMD method, − and these studies demonstrated that the PIMD simulation is the suitable choice to analyze the stationary point structures of the LBHB systems − , at the finite temperature.…”