Principles of Protein Structure - H. Schulz 1982

Statistical Mechanics of the Helix-Coil Transition
Comparison with Experimental Data. Helix-Coil Transition Curves and the Zimm-Bragg Model
Solvent Contribution

Starting from equation (A.1), the Influence of the solvent has been neglected in all formulas for the sake of simplicity. A rigorous solution of the problem would require taking into account the translational and rotational parameters of the surrounding solvent molecules. However, since this is impossible in practice, the solvent contribution is always considered separately.

The solvent can induce helix–coil transitions without Temperature changes. Furthermore, depending on the Solvents, the value of ∆H (equation (A.19)) can also be positive [789]; As a result, Ωc < Ωа, and the helix is formed even at high temperatures. In this case, The values of Ωc and Ωа incorporate solvent effects and can no longer be derived using Fig. 2.3.

* Homopolymers of many residues clearly do not form helices. In such cases, mixed polymers can be used with residues of this type as a "guest" and a good helix former (e.g., poly-γ-benzyl-L-glutamate) as a "host". By analyzing the changes in θ, one can then obtain the transition temperature for the "guest" residue.



Last update: 06/08/2026

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