Protein antigenic sites definition

The exact boundary, residue, conformational, and directional definitions of the three antigenic sites of hen egg-white lysozyme have been described. The results revealed that the three antigenic sites account quantitatively for the total antigenic reactivity of the protein. Thus the entire antigenic structure of the enzyme has now been determined precisely. Its nature was discussed together with the power of the surface-simulation synthetic concept. 

Now, while it is possible, by lowering the surface tension of the liquid medium to 50 dyn/cm by means of solutes of low molecular weight, to dissociate antigen-antibody precipitates (of the pure VDW type) (6), whole mammalian serum (with a surface tension < 50 dyn/cm) definitely has no such dissociating power. Upon some reflection this is not as anomalous as it might seem. Table I shows that it is mainly because of the presence of proteins (of molecular weight > 20,000) that blood (or plasma) has a surface tension y < 50 (and not y 70), and it cannot be expected that molecules with dimensions of the order of 100 A will effect a separation by purely physical means between other proteins of the same approximate size that are only about 2 A apart at their site of interaction (13). 

---