Association and dissociation of a weakly binding antibody to VAR2CSA DBL5ε. The frequency change (Hz) as a function of time (s), shows both the association and dissociation phase of the PAM 4.7 antibody binding to the DBL5ε domain of the VAR2CSA PfEMP1. Black lines indicate data; red lines indicate fitted curves (see Methods) and the calculated rate constants are given on the sensorgrams. A. PAM 4.7, in flow, reacting with VAR2CSA DBL5ε immobilized on a polystyrene surface, tested at the four concentrations shown. B. PAM 4.7, in flow, reacting with VAR2CSA DBL5ε, immobilized on a carboxyl surface and tested at three concentrations with a lower density of surface-immobilized antigen.