Thermodynamic molecular switch in micelles

It is well known that essentially all macromolecular interactions function over a well-defined temperature range. The Gibbs free energy change, DeltaG degrees (T), for macromolecular interaction shows a complicated behavior, wherein DeltaG degrees (T) changes from positive to negative, then reaches a negative value of maximum magnitude (favorable), and finally becomes positive as temperature increases. This communication demonstrates that the critical factor is a temperature-dependent DeltaC(p)(o)(T) (specific heat capacity change) of reaction, which is positive at low temperature but switches to a negative value at a temperature well below the ambient range. This thermodynamic molecular switch determines the behavior patterns of the Gibbs free energy change, and hence a change in the equilibrium constant, K-eq, and/or spontaneity. The subsequent, mathematically predictable changes in DeltaH degrees (T), DeltaS degrees (T), DeltaW degrees (T) and DeltaG degrees (T) give rise to the classically observed behavior patterns in biological systems. This communication will also demonstrate the existence of a thermodynamic molecular switch in both nonionic surfactants, (OPE), where i = 1, 3, 8, and 10 and ionic n-DTAB surfactants in H2O, D2O, 3 M urea and 2 M dioxane, over the experimental temperature range of 285-360 K, based on Chun's development of the Planck-Benzinger methodology (P.W. Chun, Int. J. Quantum Chem.: Quantum Biol. Symp. 15 (1988) 247; P.W. Chun, Manual for Computer-Aided Analysis of Biochemical Processes with Florida 1-2-4, University of Florida copyright reserved, 1991; P.W. Chun, J. Phys. Chem. 86 (1994) 6851; P.W. Chun, J. Biol. Chem., 270 (1995) 13925; P.W. Chun, J. Phys. Chem. 100 (1996) 7283; P.W. Chun, in: 212th National American Chemistry Society Meeting, Orlando, Fla, American Chemical Society, Biophysical Chemistry, poster 283, 1996; P.W. Chun, J. Phys. Chem. B 101 (1997) 7835; P.W. Chun, Methods in Enzymology, vol. 295, 1998, pp. 12, 227; P.W. Chun, Int. J. Quantum Chem.: Quantum Biol. Symp., 75 (1999) 1027; P.W. Chun, Int. J. Quantum Chem.: Quantum Biol. Symp. (2000); P.W. Chun, Biophysical J., 75 (2000) 416; P.W. Chun, Cell Biochem. Biophys. (2000)). In the case of micellar size distribution, the change in inherent chemical bond energy, DeltaH degrees (T-0), in micellar interaction is small. In contrast, the thermal agitation energy (heat capacity integrals), is much larger and roughly the same over a broad size distribution. This qualitative trend differs markedly from results seen for biochemical interactions, yet the underlying mathematical interpretation is the same. (C) 2001 Elsevier Science B.V. All rights reserved.