The thermal set point of water vapor and life in the condensed state

Application of the Planck–Benzinger thermal work function to biological systems has demonstrated a basic pattern for life processes, in that there is a lower cutoff point, T h , where entropy is favorable but enthalpy is unfavorable, i.e. Δ H 0 ( T h )(+) = T Δ S 0 ( T h )(+), and upper cutoff, T m , above which enthalpy is favorable but entropy unfavorable, i.e. Δ H 0 ( T m )(−) = T Δ S 0 ( T m )(−). Only between these two limits, where Δ G 0 ( T ) = 0, is the net chemical driving force favorable for interacting biological processes. In the case of water vapor condensation, the compensatory temperatures, T h and T m , are 30 K and 380 K. As water is a part of every living system, this suggests that the single point at which the system is its most stable, defined as the thermal set point, T S , must fall between the limits defined by the compensatory temperatures, 30 K and 380 K. We find that each interacting biological system will exhibit a negative minimum of Gibbs free energy change at a single well‐defined temperature, T S , where the bound unavailable energy T Δ S 0 = 0. At this point, Δ H 0 ( T S )(−) = Δ G 0 ( T S )(−) minimum , the maximum work can be accomplished. For water vapor condensation, the thermal set point falls at 260 K and T Cp at Δ C p 0 ( T ) = 0 is 130 K. In examining interacting protein systems, it would appear that the heat capacity change of reaction of water within the system determines the behavior of the other thermodynamic functions. It is clear that the requirements for the existence of a condensed state of water and the existence of life are essentially the same, and are uniquely linked to a characteristic thermal set point. Without the existence of a condensed state, life would not exist. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008