Temperature of compensation: significance for virus in- activation.

The purpose of this report is to call attention to the probable biological utility of a physical constant, the temperature of compensation (T(c)) or isokinetic temperature. T(c) has hitherto not been used in biological research. It is defined as the temperature at which a series of Arrhenius plots, related by variation of a single parameter, pass through a common point. Such systems demonstrate the so-called compensation effect and show linear variation of change in enthalpy with change in entropy; the slope [unk] H/[unk]S is T(c). Related reactions in which, for example, solvent change or structural change of the reactants does not change the mechanism of the reaction or the nature of the transition state exhibit an identical T(c). The system used in this study was a complex one, i.e., protection against thermal inactivation of Sindbis virus by HPO(4) (=) and SO(4) (=). The time-rate constant of loss of infectivity was determined at different temperatures for virus suspended in different salt concentrations at constant pH. The compensation effect was demonstrated and T(c) was found to be approximately 57 degrees C for virus inactivation in both Na(2)HPO(4) and MgSO(4) solutions. The intercept of a DeltaSdouble dagger/DeltaHdouble dagger plot, defined as the constant B, also was the same for the two salts. We suggest that determination of T(c) in biological systems might be of value in (1) establishment of whether an observed phenomenon results from the same process or mechanism as another observed phenomenon; (2) prediction of rates or other behavior under relevant conditions; and (3) classification.