The molecular origin of body temperature in homeothermic species.

We propose the interfacial water quantum-transition (IWQ) model as a novel paradigm explaining temperature-dependent structural and functional transitions (discontinuities) observed in proteins. The central postulate states that experimentally measured critical temperatures, T_C, are related to physical reference temperatures, T_W, defined by rotational quantum transitions of temporarily free water molecules in the protein-water interface. Applicability of this concept is demonstrated with transitions observed in two disparate model systems, viz., hemoglobin and thermosensitive transient receptor potential (TRP) channels. We propose that the same mechanism underlies the definition of basal body temperatures in homeotherms, the reference temperature for humans being T_W = 36.32°C. Specifically, we demonstrate that the body temperatures of both human and chicken (representing the two classes of homeothermic vertebrates) not only coincide with quantum-transition reference temperatures but are also related to pronounced transitions in hemoglobin oxygen saturation. This suggests that the evolution of body temperatures in different homeothermic species might involve an interplay between critical parameters of oxygen supply on the one hand and quantum-physical rotational transition temperatures of water on the other. Casting the IWQ model concept into a concise formula: Proteins sense and water sets critical physiological temperatures.NEW & NOTEWORTHY We propose the interfacial water quantum-transition (IWQ) model to explain how proteins respond to temperature changes through specific quantum transitions of water at the protein-water interface. This model links key functional temperatures, such as human body temperature, to these transitions. By examining proteins like hemoglobin and thermosensitive channels, the IWQ model reveals a fundamental connection between water behavior and biological temperature regulation, shedding light on evolutionary adaptations in humans and animals.