COGITO: A Coarse-Grained Force Field for the Simulation of Macroscopic Properties of Triacylglycerides

Abstract

The use of molecular dynamics simulations is becoming ever more widespread; however, the application of this to pure triacylglyceride (TAG) systems is not. In this study, we are presenting the development, and validation, of a new force field (FF), which we have called the COarse-Grained Interchangeable Triacylglyceride-Optimized FF. The FF has been developed using both a bottom-up and top-down approach for different parameters, with the non-bonded parameters being optimized using a Bayesian optimization method. While the FF was developed using monounsaturated TAGs, results show that it is also suitable for fully saturated TAGs. Description of molecules which were not used during the development of the FF is carried out simply by interchanging the bead in the molecule topologies. Results show that the FF can reproduce the macroscopic properties (density and lattice parameters) of pure TAGs as both crystals and melt with high accuracy, as well as reproduce the differences in enthalpies.

Triacylglyceride melting point determination using coarse‐grained molecular dynamics

“…Due to the non‐equilibrium nature of a melting simulation, an increased number of simulations per void size are required to estimate an accurate melting point, although we find that after 150 simulations the results are sufficiently converged. All simulations were carried out using the COGITO FF, 11 which has proven to be able to reproduce the thermodynamic melting point of various TAGs, despite not being specifically parameterized against this macroscopic property.…”

“…All simulations have been carried out using GROMACS 12 2021.3 with the COGITO FF 11 . All equilibrations were done using an NPT ensemble, using a time‐step of 25 fs and a pressure of 1.01325 bar using a v‐rescale thermostat and a Berendsen barostat.…”

“…All simulations have been carried out using GROMACS 12 2021.3 with the COGITO FF. 11 All equilibrations were done using an NPT ensemble, using a time-step of 25 fs and a pressure of 1.01325 bar using a v-rescale thermostat and a Berendsen barostat. Anisotropic pressure coupling, with a compressibility of 1 Â 10 À5 bar À1 in the x, y and z directions was used.…”

“…The coarse-grained (CG) representations of sn-POSt, sn-POP, sn-StOSt and sn-StStSt were built by mapping the XRD crystalline structures [13][14][15] as per Cordina et al 11 In the case of sn-COC, given that no crystal structure was available, a crystal was built using the CG representation of sn-POP as the starting point. The sn-COC unit cell was built by reducing the number of beads on the capric fatty acid chains, moving the molecules close to each other, using the sn-POP distances as a guideline, and reducing the unit cell dimensions accordingly.…”

“…Knowing the melting point of these compounds is very important to their processing and use. In this study, we have attempted to simulate the melting points of a range of pure TAGs with the recently developed COGITO FF, 11 using the direct heating method. The COGITO FF is a coarse‐grained FF specifically parameterized to simulate the macroscopic properties of TAGs in different phases.…”