• biological thermodynamics;
  • condensation;
  • water vapor;
  • interacting biological systems


This communication reports for the first time a link that has gone unrecognized between the compensatory temperatures of water vapor condensation and the thermal set point in interacting biological systems, where the bound unavailable energy TΔS° = 0, that is ΔH°(TS)(−) and ΔG°(TS)(−)min intersect. In addition to determining the unique thermal set point for water vapor, which falls at 260 K, our results indicate that in any biological interaction, the thermal set point must fall between the limits defined by the compensatory temperatures of water vapor, that is between 30 and 380 K, where ΔH°(Th)(+) ≅ TΔS°(Th)(+) at (Th) and ΔH°(Tm)(−) ≅ TΔS°(Tm)(−) at (Tm) or (Tcond). Only between these limits, where ΔG°(T) = 0, is the net chemical driving force favorable for biological interaction to occur. © 2012 Wiley Periodicals, Inc.