Fitting of heat capacity curves

The integration method relies heavily on the accuracy of the heat capacity data of the native or the unfolded state and on the possibility to extrapolate these data into the transition range. Application of the method shows that results are significantly altered if the reference integration baseline (either Cj,iv(r) or Cp u T)) is only slightly varied. Therefore it is a better approach to fit the data to analytical equations derived for the various folding models. This approach has two advantages. On the one hand the compatibility of the model with the data can be tested, and on the other hand - if the model is compatible - a maximum of thermodynamic information can be extracted. 

In the following we shall give enthalpy and heat capacity equations for some typical folding models. For each model the relative partition function is given as well as the enthalpy and the heat capacity functions resulting from the temperature derivatives according to equations 35 and 36. In this 

Only those models are presented for which a complete analytical solution can be given. Stoichiometries of n 1 require the solution of polynomials of n-th order, which is analytically problematic for n=3 or 4 and impossible for n 4. 

1 Two-state model, 1 1 Stoichiometry The relative partition function for this model is 

2 Three-state model, 1 1 1 Stoichiometry This simple sequential two-step unfolding reaction is described by the following equations 

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