Empirical and theoretical relationships between the sedimentation coefficient and molecular weight of various proteins, with particular reference to the immunoglobulins.

The empirical and theoretical relationships between the sedimentation coefficient and molecular weight of proteins of various conformational shapes have been investigated. In each case it was found that the relationship obeys the general formula log S020,W= a log molecular weight +b. The empirical values obtained for the slope and intercept for globular proteins (non-immunoglobulins) and immunoglobulins have been used to calculate the molecular weight from the sedimentation coefficients of other proteins belonging to these two groups. For most proteins and particularly the immunoglobulins the values obtained were found to be similar to those obtained using the classical experimental techniques. The application of this approach to the determination of molecular weights, of proteins and more particularly protein containing complexes is discussed.