The Taft equation is often employed in biological chemistry and medicinal chemistry for the development of quantitative structure–activity relationships (QSARs).  In a recent example, Sandri and co-workers have used Taft plots in studies of polar effects in the aminolysis of β-lactams.  They have looked at the binding of β-lactams to a poly(ethyleneimine) polymer, which functions as a simple mimic for human serum albumin (HSA).  The formation of a covalent bond between penicillins and HSA as a result of aminolysis with lysine residues is believed to be involved in penicillin allergies.  As a part of their mechanistic studies Sandri and co-workers plotted the rate of aminolysis versus calculated σ* values for 6 penicillins and found no correlation, suggesting that the rate is influenced by other effects in addition to polar and steric effects.