Comparative study of the conformational features of rat immunoglobulin G subclasses by circular dichroism.

Four subclasses of rat immunoglobulin G and some of their fragments were studied by circular dichroism. These studies were carried out in different conditions in order to determine whether conformational differences exist between each subclass. The results showed that in their native state the subclasses cannot be distinguished by characteristic differences. Moreover, differences between monoclonal immunoglobulins G of the same subclass were found, particularly in the 200-250 nm region, and their relationship to aromatic side chain contributions (especially those of tyrosine) has been investigated. However, the conformations of the immunoglobulin G were found to be differently affected by denaturing treatments and a relation to subclass has been demonstrated.