Protein electrostatic interactions, bond strength

Within the natural clusters, the redox potential is highly dependent on protein environment and on solvent effects, including electrostatic interactions (such as hydrogen bonding), pH, and ionic strength. The potentials for this... 

Fig. 7. Schematic diagram of the contributions of various types of interactions to the free energy of the native conformations of a hypothetical protein or a DNA molecule in aqueous solution. Fs, Fb, Fi/b, and Fm represent the free energy contributions of conformational entropy, electrostatic interactions, hydrogen bonding, and hydrophobic interactions, respectively. The magnitude oi Fg may vary considerably with the pH and ionic strength of the aqueous solution.

Clearly hydrogen bonding is critical in stabilising a globular protein structure. Also of importance are electrostatic and van der Waals interactions, of respective bond strengths 5kcalmole-1 and lkcalmole-1. 

Helices that form pores will be amphiphilic because it is more favorable to have situated in the inner side of the pore hydrophilic amino acid side chains, while the outer side of the pore represents a more favorable environment for hydrophobic amino acid side chains since these are in contact with lipids. Some authors point to the possibility that such a structure contains hydrogen bonds between amino acid residues and the main chain in order to compensate opposite charges and oppositely oriented dipoles. A comparison between the strength of different interactions in the structure of soluble and membrane proteins leads to the conclusion that because of the decreased strength of hydrophobic interactions and increased strength of electrostatic interactions (because of the reduced dielectric constant), the electrostatic interactions play the main role in stabilizing the structure of membrane proteins. ... 

---