Stepwise self-association of penicillin V as deduced by frontal derivativechromatography

The aggregation pattern of penicillin V (PCV) in a 0.15 M potassium chlorid e solution at 298.2 K is investigated by frontal derivative chromatography on Sephadex G-10 columns and is quantitatively analyzed on the basis of a s tepwise aggregation model and a trimer-dodecamer model. The aggregation par ameters for these models are best fitted to the observed centroid volume da ta. The derivative chromatogram of PCV is simulated on the basis of plate t heory with the aggregation models. The height and position of the peak simu lated on the basis of the stepwise aggregation model are in excellent agree ment with the observed ones, whereas those simulated on the basis of the tr imer-dodecamer model remarkably differ from the observed ones, particularly in dilute solutions. Thus, PCV forms dimer and self-associates stepwise.