Correlation times of C–H bond direction in different force fields

We are starting a small project to see how well the correlation times of C–H bond vectors are reproduced in different force fields. We aim to simply follow the analysis of the R₁ and τ_eff times as was done earlier by Tiago, Samuli, et al. for the Berger force field, but for all the different force fields available at the Zenodo repository of NMRlipids.

The plan is to not make this an official NMRlipids project, but still to do it fully openly; to this end, we warmly welcome anyone interested to follow the progress and to participate on GitHub!

Leftin and Brown have published experimental R₁ times for many different lipids in various temperatures and at various field strengths. Concerning the experimental τ_eff times, in Tiago's paper they are reported for POPC at full hydration and 298 K, and they have also been published for DMPC at low hydration and 300 K. However, as many of the trajectories at the Zenodo repository have DPPC, the experimental τ_eff times for DPPC at full hydration would be warmly welcomed.

Beyond force field comparison, possibly interesting physical questions to look from the data would be the effects of hydration, salts, and cholesterol on C-H bond dynamics. A possible extension could also be to look at the temperature dependence.

Hanne Antila and Markus Miettinen