Stability of Protein Structure in Aqueous Solution

The 3D structure of a protein molecule is the net result of the covalent structure (primary structure), noncovalent interactions, and conformational entropy. Table 13.3, summarizing the various interactions, compares the compact native (N) state with the completely unfolded denatured (D) state. Which state is promoted depends on the sign of which contains an enthalpic and an entropic term  

A negative value for A qG implies that the N-state is less stable than the D-state and vice versa. Various contributors to An dG counteract each other. Hydrophobic interactions and changes in the rotational freedom of the polypeptide backbone, both dominated by entropy effects, are the main competing factors. Hence, the existence of a compact protein molecule in an aqueous environment is a demonstration of the 

Interactions That Determine the Structure of a Protein Molecule in an Aqueous Environment 

Formation of protein-protein and water—water bonds compensated by loss of protein—water bonds 

Atomic packing densities in compact protein molecules higher than that in water 

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Table 3. Major Non-Covalent Forces and Interactions Important in the Organization and Stabilization of Protein Structure in Aqueous Solutions 8 16-,7)... 

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