TY - JOUR
T1 - Multipolar Force Fields for Amide-I Spectroscopy from Conformational Dynamics of the Alanine Trimer
AU - Mondal, Padmabati
AU - Cazade, Pierre André
AU - Das, Akshaya K.
AU - Bereau, Tristan
AU - Meuwly, Markus
N1 - Publisher Copyright:
© 2021 American Chemical Society
PY - 2021/10/7
Y1 - 2021/10/7
N2 - The dynamics and spectroscopy ofN-methyl-acetamide (NMA) and trialanine in solution are characterized from molecular dynamics simulations using different energy functions, including a conventional point charge (PC)-based force field, one based on a multipolar (MTP) representation of the electrostatics, and a semiempirical DFT method. For the 1D infrared spectra, the frequency splitting between the two amide-I groups is 10 cm-1from the PC, 13 cm-1from the MTP, and 47 cm-1from self-consistent charge density functional tight-binding (SCC-DFTB) simulations, compared with 25 cm-1from experiment. The frequency trajectory required for the frequency fluctuation correlation function (FFCF) is determined from individual normal mode (INM) and full normal mode (FNM) analyses of the amide-I vibrations. The spectroscopy, time-zero magnitude of the FFCFC(t= 0), and the static component Δ02from simulations using MTP and analysis based on FNM are all consistent with experiments for (Ala)3. Contrary to this, for the analysis excluding mode-mode coupling (INM), the FFCF decays to zero too rapidly and for simulations with a PC-based force field, the Δ02is too small by a factor of two compared with experiments. Simulations with SCC-DFTB agree better with experiment for these observables than those from PC-based simulations. The conformational ensemble sampled from simulations using PCs is consistent with the literature (including PII, β, αR, and αL), whereas that covered by the MTP-based simulations is dominated by PIIwith some contributions from β and αR. This agrees with and confirms recently reported Bayesian-refined populations based on 1D infrared experiments. FNM analysis together with a MTP representation provides a meaningful model to correctly describe the dynamics of hydrated trialanine.
AB - The dynamics and spectroscopy ofN-methyl-acetamide (NMA) and trialanine in solution are characterized from molecular dynamics simulations using different energy functions, including a conventional point charge (PC)-based force field, one based on a multipolar (MTP) representation of the electrostatics, and a semiempirical DFT method. For the 1D infrared spectra, the frequency splitting between the two amide-I groups is 10 cm-1from the PC, 13 cm-1from the MTP, and 47 cm-1from self-consistent charge density functional tight-binding (SCC-DFTB) simulations, compared with 25 cm-1from experiment. The frequency trajectory required for the frequency fluctuation correlation function (FFCF) is determined from individual normal mode (INM) and full normal mode (FNM) analyses of the amide-I vibrations. The spectroscopy, time-zero magnitude of the FFCFC(t= 0), and the static component Δ02from simulations using MTP and analysis based on FNM are all consistent with experiments for (Ala)3. Contrary to this, for the analysis excluding mode-mode coupling (INM), the FFCF decays to zero too rapidly and for simulations with a PC-based force field, the Δ02is too small by a factor of two compared with experiments. Simulations with SCC-DFTB agree better with experiment for these observables than those from PC-based simulations. The conformational ensemble sampled from simulations using PCs is consistent with the literature (including PII, β, αR, and αL), whereas that covered by the MTP-based simulations is dominated by PIIwith some contributions from β and αR. This agrees with and confirms recently reported Bayesian-refined populations based on 1D infrared experiments. FNM analysis together with a MTP representation provides a meaningful model to correctly describe the dynamics of hydrated trialanine.
UR - http://www.scopus.com/inward/record.url?scp=85116519364&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcb.1c05423
DO - 10.1021/acs.jpcb.1c05423
M3 - Article
C2 - 34559531
AN - SCOPUS:85116519364
SN - 1520-6106
VL - 125
SP - 10928
EP - 10938
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 39
ER -