Planck–Benzinger thermal work function in biological systems

The Planck–Benzinger methodology provides a means of determining the innate temperature‐invariant enthalpy and thermal agitation energy, or the heat capacity integrals, ∫   T 0ΔCp°(T)dT, and allows precise determination of 〈T Cp 〉, 〈T h 〉, 〈T s 〉, and 〈T m 〉. It is a method for evaluating [ΔH   ° 298− ΔH°(T 0 )], the heat of reaction for biological molecules at room temperature. The results imply that the negative Gibbs free energy change minimum at a well‐defined stable temperature, 〈T s 〉, where the bound unavailable energy TΔS° = 0, has its origin in the sequence‐specific hydrophobic interactions. Each case confirms the existence of a thermodynamic molecular switch wherein a change of sign in ΔCp°(T) reaction leads to true negative minimum in the Gibbs free energy change of reaction and, hence, a maximum in the related equilibrium constant, K eq . At this temperature, 〈T S 〉, ΔH°(T S )(−) = ΔG°(T S )(−) min , the maximum work can be accomplished in biological systems. Application of the Planck–Benzinger methodology to biological systems has demonstrated a basic rule for life processes, in that there is a lower cutoff point, 〈T h 〉, where entropy is favorable but enthalpy is unfavorable, that is, ΔH°(T h )(+) = TΔS°(T h )(+), and an upper cutoff, 〈T m 〉, above which enthalpy is favorable but entropy unfavorable, that is, ΔH°(T m )(−) = TΔS°(T m )(−). Only between these two limits, that is, where ΔG°(T) = 0, is the net chemical driving force favorable for such biological processes as protein folding; protein–protein, protein–nucleic acid or protein‐membrane interactions; and protein–self‐assembly. Indeed, all interacting biological systems examined using the Planck–Benzinger methodology have shown such a thermodynamic switch at the molecular level, suggesting that its existence may be universal. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004