Electrostatic interactions

Electrostatic interactions are attractive or repulsive forces between charged parts of molecules. These charges can be integral (in cations, anions, zwitter-ions, or polyionic species) or partial charges (like in a peptide functional group, which is net neutral but has an uneven charge distribution. The strength of electrostatic interactions decreases with distance, and is modulated by the nature of the medium between the interacting partners (e.g. solvent, membrane, hydrophobic core of protein) as measure by its dielectric constant.

spinqualitylabelsall models Caption for this structure Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Protein: DNA interactions In some protein-nucleic acid complexes, the major attractive interaction leading to complex formation is electrostatic. Duplex DNA is negatively charged; if the binding site of the protein has a net-positive charge (e.g when there are more arginine and lysine side chains than aspartate and glutamate side chains), there will be a large electrostatic component. In that case, the binding constant would be strongly dependent on ionic strength of the solvent. One such example is the interaction between DNA and the nucleoid-associated protein FIS. The electrostatic potential of FIS shows positive charge on the surface of the two helix-turn-helix motifs, with a more balanced potential for the remainder of the protein surface. Dipole of an alpha helix TBA

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