The Shape of a Protein Molecule

Account for the shape of a protein molecule in terms of:
– Electrostatic forces
– Hydrogen bonding forces
– Hydrophobic forces
– Disulfide forces

  • Electrostatic forces:
    • The 3D structure of a protein molecule is determined by a few different basic interactions, including: Geometry of atoms and molecules, forces between atoms, bond lengths and angles, angle twisting, electrostatic forces, and van der Waals interactions.
    • Electrostatic interactions occur between all pairs of atoms. Like charges repel like charges, and opposite charges attract opposite charges.
  • Hydrogen bonding forces:
    • The 3D structure of a protein molecule is also determined by complex interactions, which include Hydrogen bonds and Hydrophobicity.
    • Hydrogen bonds occur between electronegative atoms such as F, N, or O and a hydrogen atom bound to another electronegative atom.
    • These forces play a critical role in the structure of the protein.
  • Hydrophobic forces:
    • Hydrophilic molecules are polar and readily form hydrogen bonds with water.
    • Hydrophobic molecules are non-polar and do not form bonds with water.
    • Hydrophobic effect: Hydrophobic molecules tend to cluster together in water in order to minimise contact. This is where the saying, “oil and water don’t mix” comes from. This is also critical to protein structure.
  • Disulfide forces:
    • Disulfide bonds are covalent and form when the side chain contains Sulfur. They provide stability for the shape of the protein.
    • The position of disulfide bonds can determine whether the protein has a straight or curly appearance.
    • Cysteine is one of the main amino acids that will form a disulfide bond, and does so with another cysteine.
    • In general, disulfide bonds can be created and broken very easily.