Chemical Forces Affecting Antigen - Antibody Reactions

• Ionic Bonds
  These result from the electrostatic attractive forces between charged sites on antigens (e.g. COO-) and oppositely charged sites on antibodies (e.g. NH3+).

• Hydrogen Bonds
  

  These relatively weak bonds occur when proton donors (OH, NH) and acceptors (COO-) on antigens and antibodies share hydrogen atoms.

• van der Waals Forces
  These are very short-range bonds which result from the interaction of electron clouds of two atoms. When electrons swing to one side of an atom, a slight positive charge occurs at the other side which can attract the negatively charged electrons of a nearby atom.

• Hydrophobic Bonds
  Then two hydrophobic surfaces on a antigen and antibody are brought close together, the water molecules between the surfaces are excluded. The two hydrophobic surfaces then come together to decrease the total surface area exposed. Hydrophobic bonds result from the tendency of all molecules to exist in the lowest free energy state and are entropy driven (energy required to maintain structural order).

Chemical Forces Affecting Antigen-Antibody Reactions