Free energy of hydration and heat capacity of calcium dipicolinate in Bacillus spore cores

Wet heat treatments are widely used sterilization techniques for inactivating dangerous and resistant sporulating bacteria. The effectiveness of such treatments depends upon the thermodynamics of water uptake by the spore as well as the kinetics of phase transformations in the hydrated spore core. The mechanism behind these chemical and physical processes remains unknown because the thermodynamic properties of the spore core constituents are not well understood. Here, we use reactive molecular dynamics simulations to calculate the vibrational density of states and specific heat of hydrated calcium dipicolinate as well as the free energy of hydration based on Jarzynski's inequality. These two quantities are used to construct a phase diagram of hydrated calcium dipicolinate, indicating the extent of hydration at different pressures and temperatures, which can be used to identify potential regimes for wet-heat sterilization of bacterial spores.Wet heat treatments are widely used sterilization techniques for inactivating dangerous and resistant sporulating bacteria. The effectiveness of such treatments depends upon the thermodynamics of water uptake by the spore as well as the kinetics of phase transformations in the hydrated spore core. The mechanism behind these chemical and physical processes remains unknown because the thermodynamic properties of the spore core constituents are not well understood. Here, we use reactive molecular dynamics simulations to calculate the vibrational density of states and specific heat of hydrated calcium dipicolinate as well as the free energy of hydration based on Jarzynski's inequality. These two quantities are used to construct a phase diagram of hydrated calcium dipicolinate, indicating the extent of hydration at different pressures and temperatures, which can be used to identify potential regimes for wet-heat sterilization of bacterial spores.